U.S. patent application number 16/722540 was filed with the patent office on 2020-06-25 for method and system for preparing a solution.
The applicant listed for this patent is Endress+Hauser Conducta GmbH+Co. KG. Invention is credited to Anja Gerlinger, Ulrich Kathe, Daniel Schweitzer.
Application Number | 20200200653 16/722540 |
Document ID | / |
Family ID | 70969332 |
Filed Date | 2020-06-25 |
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United States Patent
Application |
20200200653 |
Kind Code |
A1 |
Schweitzer; Daniel ; et
al. |
June 25, 2020 |
METHOD AND SYSTEM FOR PREPARING A SOLUTION
Abstract
The present disclosure relates to a method for preparing a
solution for use with a measuring device for determining a
measurand that depends on a concentration of at least one analyte
in a sample. The method includes a step of adding at least one
capsule to a predetermined volume of a liquid comprising a solvent,
wherein the capsule has a wall completely surrounding an interior
and at least one substance accommodated within the interior. The
wall of the capsule at least partially dissolves in the liquid and
the substance accommodated in the interior escapes into the liquid.
The method also includes a step of mixing the substance with the
liquid or dissolving the substance in the liquid. The present
disclosure also relates to a system for preparing a solution
according to said method.
Inventors: |
Schweitzer; Daniel;
(Remshalden, DE) ; Kathe; Ulrich; (Ludwigsburg,
DE) ; Gerlinger; Anja; (Stuttgart, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Endress+Hauser Conducta GmbH+Co. KG |
Gerlingen |
|
DE |
|
|
Family ID: |
70969332 |
Appl. No.: |
16/722540 |
Filed: |
December 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 2001/2893 20130101;
G01N 1/28 20130101 |
International
Class: |
G01N 1/28 20060101
G01N001/28 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2018 |
DE |
10 2018 133 148.7 |
Nov 8, 2019 |
DE |
10 2019 130 236.6 |
Claims
1. A method for preparing a solution for use with a measuring
device for determining a measurand that depends on a concentration
of at least one analyte in a sample, including: adding at least one
capsule to a predetermined volume of a liquid comprising a solvent,
wherein the capsule has a wall completely surrounding an interior
and at least one substance accommodated within the interior,
wherein the wall of the capsule at least partially dissolves in the
liquid and the substance accommodated in the interior escapes into
the liquid; and mixing the substance with the liquid and/or
dissolving the substance in the liquid.
2. The method of claim 1, wherein the solution is a standard
solution for calibrating, verifying or adjusting the measuring
device, and wherein the substance forms a first component of the
standard solution, and wherein the liquid forms a second component
of the standard solution.
3. The method of claim 1, wherein the substance comprises a
predetermined quantity of the analyte or of a first reactant which,
upon mixing or dissolving the substance in the liquid, undergoes a
chemical reaction which involves at least one second reactant
contained in the liquid and in which the analyte forms as a
reaction product.
4. The method of claim 1, wherein the solution is a reagent
solution to be added to the sample in order to measure the
measurand, and wherein the substance forms a first component of the
reagent solution comprising one or more chemical substances, and
wherein the liquid forms a second component of the reagent solution
comprising one or more chemical substances.
5. The method of claim 1, wherein the wall of the capsule is formed
from a material which does not influence the determination of the
measurand by means of the measuring device.
6. The method of claim 1, wherein the substance is present in the
interior of the capsule as a solid or bound to a solid phase.
7. The method of claim 1, wherein the predetermined volume of the
liquid is presented in a closed liquid container, wherein the
liquid container is opened, the capsule is added to the volume of
the liquid presented in the liquid container, and the substance
escaping from the capsule is mixed with the liquid or dissolved in
the liquid in the liquid container.
8. The method of claim 1, wherein the liquid contains at least one
stabilizer for inhibiting chemical or photochemical degradation
reactions of the analyte or of the substance intended for carrying
out a chemical reaction with the analyte in the prepared
solution.
9. A method for calibrating, verifying or adjusting a measuring
device for determining a measurand that depends on a concentration
of at least one analyte in a sample, including: preparing at least
one standard solution by: adding at least one capsule to a
predetermined volume of a liquid comprising a solvent, wherein the
capsule has a wall completely surrounding an interior and at least
one substance accommodated within the interior, wherein the wall of
the capsule at least partially dissolves in the liquid and the
substance accommodated in the interior escapes into the liquid; and
mixing the substance with the liquid or dissolving the substance in
the liquid; detecting by means of the measuring device at least one
measured value of the measurand in at least a portion of the
standard solution; and calibrating, verifying and/or adjusting the
measuring device using the at least one measured value.
10. The method of claim 9, wherein the volume of the liquid
predetermined in the step of preparing the standard solution is
presented in a closable liquid container, the capsule is added to
the volume of the liquid presented in the liquid container, and the
substance escaping from the capsule is mixed with the liquid or
dissolved in the liquid in the liquid container, and wherein the
measuring device is an analyzer, and wherein the method further
comprises the following steps: connecting the liquid container to a
liquid line fluidly connected to a reaction vessel of the analyzer;
metering at least one predetermined volume of the standard solution
contained in the liquid container into the reaction vessel via a
liquid line; performing a chemical reaction of the analyte
contained in the standard solution with at least one reaction
partner supplied to the reaction vessel in order to form a reaction
product; and detecting a measured value dependent on the quantity
of the reaction product formed.
11. A method for determining a measured value of a measurand that
depends on the concentration of an analyte in a sample liquid by
means of a measuring device according to a standard addition
method, including: using a measuring device according to a standard
addition method to determine the measured value; adding a specific
quantity of analyte in the form of at least one capsule to the
sample liquid or to samples taken from the sample liquid; wherein
the capsule has a wall completely surrounding an interior and a
substance accommodated within the interior and comprising the
analyte; and dissolving the wall of the capsule at least partially
in the sample liquid, and the substance and the substance
accommodated in the interior escapes into the sample liquid and
dissolves therein.
12. The method of claim 11, including: detecting, using the
measuring device, a first measurement signal representing the
measurand in a sample taken from the sample liquid; adding to the
sample at least one first capsule which has a wall completely
surrounding an interior and a substance accommodated within the
interior and comprising at least one predetermined quantity of the
analyte, wherein the wall of the capsule at least partially
dissolves in the sample and the substance accommodated in the
interior escapes into the sample, and mixing the substance with the
sample or dissolving the substance in the sample; detecting, using
the measuring device, at least one second measurement signal
representing the measurand in the sample; adding to the sample at
least one second capsule having a wall completely surrounding an
interior and a substance accommodated within the interior and
comprising at least one predetermined quantity of the analyte,
wherein the wall of the capsule at least partially dissolves in the
sample and the substance accommodated in the interior escapes into
the sample, and mixing the substance with the sample or dissolving
the substance in the sample; detecting, using the measuring device,
at least one third measurement signal representing the measurand in
the sample; and deriving a measured value of the measurand on the
basis of the first, the second and the third measurement
signal.
13. The method of claim 11, wherein the measured value of the
measurand is determined by extrapolation of a function representing
the sequence of the measurement signals or the sequence of values
derived from the measurement signals depending on the concentration
of the analyte.
14. A system for preparing a solution for use with a measuring
device for determining a measurand that depends on a concentration
of at least one analyte in a sample, including: at least one first
capsule which has a wall completely surrounding an interior and at
least one first substance accommodated within the interior; and a
container closed in a liquid-tight manner, which contains a
predetermined volume of a liquid containing a solvent; wherein the
wall is designed to at least partially dissolve in the solvent.
15. The system of claim 14, wherein the solution is a standard
solution for calibrating, verifying or adjusting the measuring
device.
16. The system of claim 14, wherein the first substance forms a
first component of the standard solution, and wherein the liquid
forms a second component of the standard solution.
17. The system of claim 15, wherein the first substance comprises a
predetermined quantity of the analyte or of a first reactant which,
upon mixing or dissolving the substance in the liquid, undergoes a
chemical reaction which involves at least one second reactant
contained in the liquid and in which the analyte forms as a
reaction product.
18. The system of claim 17, further comprising at least one second
capsule which has a wall completely surrounding an interior and at
least one second substance accommodated within the interior,
wherein the wall of the second capsule is designed to at least
partially dissolve in the solvent, and wherein the second substance
comprises the second reactant.
19. The system of claim 14, wherein the at least one first capsule
is enclosed in an outer packaging in a gas-tight and liquid-tight
manner.
20. The system of claim 14, wherein the at least one first capsule
is accommodated in a blister packaging which has a flexible rear
wall on which the at least one first capsule rests and a plastic
film molding which is integrally bonded to the flexible rear wall
in such a way that the plastic film molding and the rear wall form
a closed chamber in which the at least one first capsule is
arranged.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is related to and claims the
priority benefit of German Patent Application Nos. 10 2018 133
148.7, filed on Dec. 20, 2018 and 10 2019 130 236.6, filed on Nov.
8, 2019, the entire contents of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a method and a system for
preparing a solution for use with a measuring device which serves
to determine a measurand that depends on a concentration of at
least one analyte in a sample. The present disclosure also relates
to a method for calibrating, verifying and/or adjusting such a
measuring device.
SUMMARY
[0003] The object of analytical measuring in the laboratory and in
the field of process measuring is the qualitative and/or
quantitative determination of ingredients in measuring media, e.g.
in measuring liquids. A wide range of measuring devices for
measuring a multiplicity of different parameters are used for this
purpose. In the field of liquid analysis, potentiometric sensors,
such as pH measuring chains or ion-selective electrodes,
amperometric sensors, conductivity sensors, optochemical sensors,
photometers, spectrometers and analyzers are used, for example.
Some measuring devices quantitatively determine a concentration of
a single substance, for example an ion concentration, the pH value,
the concentration of a dissolved gas, or the concentration of
specific chemical compounds. Other measuring devices serve to
determine sum parameters which include the concentration of a
plurality of different substances, e.g. total organic carbon (TOC),
total oxygen demand (CSB or COD), total nitrogen (TN), total
phosphorus (TP), conductivity, or the spectral absorption
coefficient (SAC).
[0004] In measuring mode, some measuring devices for liquid
analysis require solutions which are used for measuring the
measurand in samples of unknown composition and/or for calibrating,
verifying or adjusting the measuring device. One example of such
solutions are reagent solutions which serve to carry out a chemical
reaction with the analyte in a sample before a measured value is
detected.
[0005] Such reagent solutions are used, for example, in automatic
analyzers. Analyzers are used, for example, for measuring the
concentration of an analyte or of a sum parameter determined by a
plurality of analytes. Analyzers are often designed to add one or
more reagent solutions to a sample. The substances contained in the
reagent solutions undergo a chemical reaction with the analyte or
analytes, the reaction product of which can be detected by means of
a measuring method. Frequently, the analyzer is configured to
detect the reaction product optically, for example photometrically
or spectrometrically, and to generate a measurement signal that
correlates with the quantity of reaction product produced. This
measurement signal can be used to determine the concentration of
the analyte or the value of the sum parameter in the original
sample. Such analyzers are known, for example, from DE 10 2013
114138 A1, DE 10 2013 114011 A1, DE 10 2011 075762 A1 or DE 10 2011
007011 A1.
[0006] So-called standard solutions are usually used for
calibrating, verifying and adjusting the measuring devices,
including the analyzers, mentioned here. "Calibrating a measuring
device" is understood to mean ascertaining a deviation of the
measured value measured by the measuring device from a value of the
measurand that is assumed to be correct. This value that is assumed
to be correct can be made available by a second measuring device
which serves as standard. In addition to ascertaining the
deviation, the verification also includes determining the deviation
and evaluating it. "Adjusting" means adapting the measuring device
in such a way that a measuring circuit and/or a model, by means of
which the measuring device determines a measured value in the
physical unit of the measurand from a primary measurement signal,
for example a measuring voltage or a measuring current, is adapted
such that the measured value determined corresponds to the value of
the measurand that is assumed to be correct. Standard solutions
used for the calibration of measuring devices for analytical
measuring contain a predetermined quantity, for example a
predetermined concentration, of one or more analytes to be
determined by the measuring device to be calibrated. This
predetermined analyte content of the standard solutions is used as
a comparative value (measured value that is assumed to be correct)
for the calibration, verification or adjustment of the measuring
devices.
[0007] The composition of the liquids used by measuring devices of
analytical engineering must be adjusted as precisely as possible in
order to ensure correct results. This applies in a particularly
high degree to the standard solutions used for calibration,
verification and/or adjustment since a deviation of the actual
concentration of the analyte or analytes in the standard solution
from the desired concentration has a direct effect on the measuring
accuracy of the measuring device.
[0008] High demands are therefore placed on the degree of purity of
the starting materials used for the liquids. It is also necessary
to work carefully and precisely in the preparation of the standard
solutions. This requires suitable laboratory equipment, high
training levels of the personnel entrusted with the preparation of
the solutions, and elaborate quality control. Depending on which
ingredients are to be added to the solution, corresponding
occupational safety measures must be observed. It is therefore
customary to prepare reagent solutions, standard solutions and
other useful liquids of measuring devices in a specialized central
laboratory and to send them ready-for-use to the users of the
measuring devices. Measuring device manufacturers frequently also
prepare reagent solutions and standard solutions for the
calibration, adjustment and verification of their measuring devices
and offer them as accessories or operating supplies for the
corresponding measuring devices. However, some of these solutions
are only temporarily stable, i.e., do not have a stable
concentration, for example when they contain constituents which are
degenerated or chemically converted under the influence of
temperature, light or oxygen or by bacterial decomposition. Such
standard solutions must frequently be renewed and possibly cannot
be centrally manufactured and sent to the user in a ready-to-use
form.
[0009] It is therefore desirable to prepare standard solutions
immediately before their use for calibrating, verifying or
adjusting a measuring device, possibly on site. Since the user of
the measuring device must in this case as a rule prepare the
standard solution, a method which is as simple, reliable and robust
as possible should be available for the preparation of the standard
solution. A few approaches in this respect are known in the prior
art.
[0010] For example, the analyte and optionally further constituents
of a standard solution, for example buffers or stabilizers, can be
provided to the user in the form of a highly concentrated stock
solution in a glass or plastic ampoule or bottle. The ampoule
content must be transferred by the user to a volumetric flask, and
a defined volume of a solvent, for example ultrapure water, must
then be added. The advantage of this method is that the analyte is
already present in the ampoule in the required quality and
quantity. The user does not have to be concerned with the purity of
the substances use, and measuring, for example weighing, the
substances of the stock solution used from the ampoule is dispensed
with. Nevertheless, there is a risk that the standard solution thus
prepared does not contain the analyte at the required concentration
since errors in measuring the solvent volume are possible. It can
also happen that the ampoule content is not completely transferred
into the volumetric flask if, for example, drops remain on the
ampoule wall during the transfer. The correct handling of the
ampoules requires trained personnel and corresponding quality
control. Moreover, degeneration of the ampoule content by
photochemically or thermally induced degradation processes cannot
be completely ruled out in this method.
[0011] Reagent solutions comprising various substances which
possibly react with one another under the influence of light and
heat and thus have a limited shelf life, can be divided into a
plurality of solid or liquid components which, when uncombined,
have a long shelf life. This is known, for example, from DE 10 2011
007 011 A1, which describes an analyzer that is configured to
automatically prepare a reagent solution from a plurality of
components shortly before its use in the measuring device. To this
end, the analyzer has a first reservoir with a first reagent
component, a second reservoir with a second reagent component, and
a mixing device for mixing a predetermined quantity of the first
reagent component from the first reservoir with a predetermined
quantity of the second reagent component from the second reservoir
in order to form a predetermined quantity of the reagent solution.
The reagent solution to be prepared, which itself does not have a
long shelf life because its ingredients undergo degradation
reactions, which may be thermally or photochemically induced, in
solution, is thus divided for the purpose of storage into two
reagent components, which in turn can comprise one or more
individual chemical substances that, in the combination present in
the respective reagent components, do not undergo any chemical
decomposition reactions, or undergo chemical decomposition
reactions taking place only very slowly under the conditions
prevailing in the reservoirs.
[0012] According to the same principle, several ampoules, bottles
or bags containing individual components of the solution to be
prepared can be made available to a user for the preparation of
reagent or standard solutions. Although this procedure prevents
premature degeneration of the solutions, it also has the same
disadvantages as the method described above, in which a single
stock solution has to be diluted with solvent by the user.
[0013] The object of the present disclosure is therefore to specify
an improved method for preparing a solution for use with a
measuring device for determining a measurand that depends on a
concentration of at least one analyte in a sample. In particular,
the method should be able to be carried out with little effort by
untrained or only slightly trained personnel and have a low risk of
error.
[0014] This object is achieved by the method of the present
disclosure, which includes calibrating, verifying and/or adjusting
a measuring device for determining a measurand that depends on the
concentration of at least one analyte in a sample. The present
disclosure also includes a method for determining a measured value
of a measurand that depends on the concentration of an analyte in a
sample by means of a measuring device, and a system for preparing a
solution for use with a measuring device for determining a
measurand that depends on a concentration of at least one analyte
in a sample.
[0015] The method of the present disclosure for preparing a
solution for use with a measuring device for determining a
measurand that depends on a concentration of at least one analyte
in a sample includes adding at least one capsule to a predetermined
volume of a liquid comprising a solvent, wherein the capsule has a
wall completely surrounding an interior and at least one substance
accommodated within the interior. The wall of the capsule at least
partially dissolves in the liquid and the substance accommodated in
the interior escapes into the liquid. The method also includes
mixing the substance with the liquid and/or dissolving the
substance in the liquid.
[0016] The substance is protected from contamination, oxygen and
moisture by the wall of the capsule, which completely surrounds the
interior. The capsule wall may also be designed to protect the
substance from light. Prior to the addition of the capsule, the
predetermined volume of the liquid comprising the solvent may also
be stored in a closed and/or sealed manner in a suitable liquid
container, such as a bottle, in order to protect this component
from contamination, oxygen, light and moisture. Unlike the case of
glass or plastic ampoules known from the prior art, the capsule
does not have to be opened and emptied by the user but can be
introduced as a whole into the liquid, where it dissolves at least
partially so that the substance escapes into the liquid and
dissolves therein. The loss of a portion of the substance is thus
completely ruled out in the method according to the present
disclosure, whereas substance can be lost during the opening of the
ampoule and/or remain in the ampoule in a method of the prior art.
Since the user also cannot accidentally come into contact with the
substance enclosed in the capsule in the method according to the
present disclosure, the risk of contamination is also greatly
reduced, as are possible safety risks in the case of toxic or
harmful substances.
[0017] The method permits a highly precise metering of the
substance and can therefore be used for the preparation of any
solutions for use with measuring devices of analytical engineering
and particularly advantageously for the preparation of a standard
solution for the calibration, verification and/or adjustment of
measuring devices. In this application, the substance contains a
predetermined quantity of the at least one analyte. However, the
method is equally suitable for preparing other solutions for the
measuring device, for example for preparing a reagent solution for
carrying out a chemical reaction of a reagent contained in the
reagent solution with the at least one analyte.
[0018] In a particularly advantageous embodiment, the predetermined
volume of the liquid comprising the solvent is provided already
measured in a closed, possibly also sealed, liquid container. In
this case, the method comprises opening the liquid container prior
to adding the capsule. In this embodiment of the method, an error
of the user when measuring the components for the liquid to be
prepared is practically ruled out.
[0019] In one embodiment of the present disclosure, the solution is
a standard solution for calibrating, verifying and/or adjusting the
measuring device, wherein the substance forms a first component of
the standard solution, and wherein the liquid forms a second
component of the standard solution. In this embodiment, the
substance forming the first component may comprise a single
chemical substance, for example the analyte. However, it is also
possible for the substance to be a mixture of a plurality of
chemical species, for example of various ions or molecules.
Similarly, the second component may comprise one or more different
chemical species. The components are advantageously divided in such
a way that the substances present in one of the respective
components do not undergo any chemical (decomposition) reactions or
undergo chemical (decomposition) reactions which take place only
very slowly with one another.
[0020] In a further embodiment, the substance may comprise a
predetermined quantity of the analyte or a reactant which, upon
mixing and/or dissolving the substance in the liquid, undergoes a
chemical reaction which involves at least one second reactant
contained in the liquid and in which the analyte forms as a
reaction product.
[0021] In addition to the analyte or the reactant, the substance
may comprise an extender which is inert to the further constituents
of the solution to be prepared and does not influence the
determination of measured values by the measuring device. Suitable
extenders are, for example, sugar, starch or a silicate.
Advantageously, the extender is soluble in the liquid, but this is
not required. By means of the extender, the analyte or reactant is
present in diluted form in the substance, for example in a ratio of
1:50 or 1:100 or 1:500. As a result, the filling accuracy of the
analyte or reactant in the capsule can be improved. This is
advantageous for the preparation of standard solutions with
particularly low concentrations of the analyte.
[0022] In an alternative embodiment, the solution to be prepared
can be a reagent solution to be added to the sample in order to
measure the measurand, wherein the substance forms a first
component of the reagent solution comprising one or more chemical
substances, and wherein the liquid forms a second component of the
reagent solution comprising one or more chemical substances. The
components are advantageously divided in such a way that the
substances present in one of the respective components do not
undergo any chemical (decomposition) reactions or undergo chemical
(decomposition) reactions which take place only very slowly with
one another.
[0023] In an advantageous embodiment, the wall of the capsule is
formed from a material which does not influence the determination
of the measurand by means of the measuring device. This has the
advantage that the measurement result obtained with the measuring
device is independent of a mass or wall thickness of the capsule so
that production fluctuations in the preparation of capsules for the
method according to the present disclosure do not play any role in
terms of the shape and wall thickness of the individual
capsules.
[0024] If the solvent contained in the liquid is water, the wall of
the capsule can be formed from a water-soluble and/or swellable
material. For example, cellulose, gelatin, agar-agar or carrageenan
may be used.
[0025] The substance may be present in the interior of the capsule
as a solid, in a concentrated solution or bound to a solid phase.
In the latter case, it may be bound to the solid phase by
physisorption or chemisorption.
[0026] As already mentioned, the predetermined volume of the liquid
can be provided in a closed liquid container. In this case, the
capsule can be added to the volume of liquid presented in the
liquid container and mixed with the liquid and/or dissolved in the
liquid in the liquid container. The closed liquid container can be
used for storage and/or transport for the predetermined volume of
the liquid before the solution is prepared. In an advantageous
embodiment, the liquid container can be sealed in the original
state so that it is visible when the liquid container has already
been opened once. After the first opening, the liquid container is
re-closable so that it can serve for storing and transporting the
prepared solution after the liquid has been prepared by adding the
capsule to the liquid in the liquid container.
[0027] In an advantageous embodiment, the closed or sealed liquid
container can contain an agitator body. This agitator body can be
used for stirring or agitating the liquid in order to accelerate
the dissolution of the substance. The agitator body can comprise a
magnet which can be driven by a rotating magnetic field from
outside the liquid container, e.g. by means of a magnetic stirrer
or magnetic mixer, for stirring the liquid. By including the
agitator body already in the closed or sealed liquid container any
accidental contamination of the solution to be prepared by an
agitator body added by a user to the liquid can be avoided.
[0028] The liquid may contain at least one stabilizer for
inhibiting chemical or photochemical degradation reactions in the
prepared solution.
[0029] The present disclosure also relates to a method for
calibrating, verifying and/or adjusting a measuring device for
determining a measurand that depends on a concentration of at least
one analyte in a sample. This method includes preparing at least
one standard solution by means of the method according to any of
the above-described method embodiments, detecting by means of the
measuring device at least one measured value of the measurand in at
least a portion of the standard solution, and calibrating,
verifying and/or adjusting the measuring device using the at least
one measured value.
[0030] The volume of the liquid predetermined in the step of
preparing the standard solution may be presented in a closable or
closed liquid container. In this case, the capsule can be added
directly to the volume of the liquid provided in the liquid
container possibly after the opening of the liquid container, where
applicable, and the substance escaping from the capsule can be
mixed with the liquid and/or dissolved in the liquid in the liquid
container. The liquid container can be closed again after opening
and adding the capsule. This is advantageous if the measuring
device is an automatic analyzer because the liquid container can
serve both as a transport and storage container for the standard
solution and can also be used directly as a standard solution
reservoir in the analyzer. This saves intermediate steps for
transferring the liquid or the prepared standard solution and
avoids loss of liquid.
[0031] The method may also include steps of connecting the liquid
container to a liquid line fluidly connected to a reaction vessel
of the analyzer, metering at least one predetermined volume of the
standard solution contained in the liquid container into the
reaction vessel via a liquid line, and performing a chemical
reaction of the analyte contained in the solution with at least one
reaction partner supplied to the reaction vessel in order to form a
reaction product. Further, the method includes detecting a measured
value dependent on the quantity of the reaction product formed.
[0032] For calibration, verification or adjustment, the method
further includes comparing the measured value with a reference
measured value representing the concentration of the analyte in the
standard solution that is assumed to be correct. This reference
measured value can be determined from the volume of the liquid used
for preparing the standard solution and the quantity of analyte
contained in the capsule.
[0033] The present disclosure also includes a method for
determining by means of a measuring device a measured value of a
measurand that depends on the concentration of an analyte in a
sample liquid. This method is based on the standard addition method
known per se. The capsule which can be used for the above-described
method for preparing a solution, such as a standard solution, can
accordingly also be used for adding a defined quantity of the
analyte to an unknown sample liquid in order to determine an
analyte concentration according to the standard addition
method.
[0034] The method for determining a measured value of the measurand
by means of a standard addition method includes adding a specific
quantity of analyte to the sample liquid or to samples taken from
the sample liquid, wherein the analyte is added in the form of at
least one capsule, wherein the capsule has a wall completely
surrounding an interior and a substance comprising the analyte and
accommodated within the interior, and wherein the wall of the
capsule dissolves at least partially in the sample liquid, and the
substance accommodated in the interior escapes into the sample
liquid and dissolves therein.
[0035] According to one embodiment, the method includes dividing a
sample liquid into at least a first, a second and a third sample,
such as in the same volumes, and detecting by means of the
measuring device a first measurement signal representing the
measurand in the first sample. The method also includes adding to
the second sample at least one first capsule which has a wall
completely surrounding an interior and a substance accommodated
within the interior and comprising at least one predetermined
quantity of the analyte, wherein the wall of the first capsule at
least partially dissolves in the second sample and the substance
accommodated in the interior escapes into the second sample, and
mixing the substance with the second sample and/or dissolving the
substance in the second sample. After adding the at least one first
capsule to the second sample, the method includes, detecting by
means of the measuring device a second measurement signal
representing the measurand in the second sample.
[0036] The method also includes adding at least one second capsule
to the third sample, wherein the wall of the second capsule at
least partially dissolves in the third sample and the substance
accommodated in the interior escapes into the third sample, and
mixing the substance with the third sample and/or dissolving the
substance in the third sample, wherein the quantity of analyte
added to the third sample by addition of the at least one second
capsule differs from the quantity of the analyte added to the
second sample by addition of the at least one first capsule. After
adding the at least one second capsule, the method includes
detecting by means of the measuring device a third measurement
signal representing the measurand in the third sample. Further, the
method includes deriving a measured value of the measurand on the
basis of the first, the second and the third measurement
signal.
[0037] This embodiment is suitable for measuring devices which
consume the sample in order to detect a measurement signal, for
example for the analyzers already mentioned above, which add to a
sample one or more reagents for carrying out a chemical reaction or
which chemically or thermally digest a sample in order to detect a
measurement signal in the sample. A plurality of first capsules may
be added to the second sample and a plurality of second capsules
may be added to the third sample. It is also conceivable that in
each case only one first capsule is added to the second sample and
one second capsule is added to the third sample, in which case the
first and the second capsule contain different quantities of the
analyte.
[0038] The sample liquid is, for example, a liquid water sample,
e.g. drinking water or waste water, in which the wall of the
capsule at least partially dissolves.
[0039] In another embodiment, which is suitable for measuring
devices which do not consume the sample liquid in the measurement,
for example for ion-selective electrodes, conductivity sensors, pH
sensors, or optical or spectrometric probes, the method may include
detecting by means of the measuring device a first measurement
signal representing the measurand in a sample taken from the sample
liquid, and adding to the sample at least one first capsule which
has a wall completely surrounding an interior and a substance
accommodated within the interior and comprising at least one
predetermined quantity of the analyte, wherein the wall of the
capsule at least partially dissolves in the sample and the
substance accommodated in the interior escapes into the sample, and
mixing the substance with the sample and/or dissolving the
substance in the sample.
[0040] The method further includes detecting by means of the
measuring device at least one second measurement signal
representing the measurand in the sample, and adding to the sample
at least one second capsule which has a wall completely surrounding
an interior and a substance accommodated within the interior and
comprising at least one predetermined quantity of the analyte,
wherein the wall of the capsule at least partially dissolves in the
sample and the substance accommodated in the interior escapes into
the sample, and mixing the substance with the sample and/or
dissolving the substance in the sample.
[0041] Thereafter the method includes detecting by means of the
measuring device at least one third measurand signal representing
the measurand in the sample, and deriving a measured value of the
measurand on the basis of the first, the second and the third
measurement signal.
[0042] In this embodiment, the first and the second capsule are
advantageously designed identically and contain the same quantity
of the analyte. However, it is also possible to use capsules which
contain different quantities of the analyte, provided this is taken
into account when deriving the measured value of the measurand.
[0043] In both method embodiments, the measured value of the
measurand can be determined by extrapolation of a function
representing the sequence of the measurement signals or the
sequence of values derived from the measurement signals depending
on the concentration of the analyte, e.g. a best-fit straight
line.
[0044] In all method variants described here, it is possible to
detect more than three measurement signals and to derive therefrom
the measured value of the measurand. For this purpose, further
samples can be prepared with analyte added by adding capsules. In
the case of a measurement without sample consumption, further
measurement signals can be detected with the measuring device after
adding further analyte-containing capsules to the sample. The
further measurement signals can then additionally be used for
determining the best-fit straight line and for determining the
unknown analyte concentration of the sample or sample liquid.
[0045] The present disclosure also relates to a system for
preparing a solution for use with a measuring device for
determining a measurand that depends on a concentration of at least
one analyte in a sample, with the system including at least one
first capsule having a wall completely surrounding an interior and
at least one first substance accommodated within the interior. The
system also includes a liquid container, which may be closed in a
liquid-tight manner, which contains a predetermined volume of a
liquid containing a solvent. The wall may be designed to at least
partially dissolve in the solvent.
[0046] As already mentioned in connection with the above-described
method for preparing a solution for use with a measuring device for
determining a measurand that depends on a concentration of at least
one analyte in a sample, the solution can be, for example, a
standard solution for the calibration, verification and/or
adjustment of the measuring device or another solution to be used
with the measuring device, e.g. a reagent solution to be added to
the sample in order to carry out a measurement.
[0047] As already described in connection with the preparation
method for the solution, the solution to be prepared can be divided
into a plurality of components, wherein one component is formed by
the liquid and one or more further components can be present in the
form of a substance contained in one or more capsules.
[0048] The first substance may form a first component of the
solution, and the liquid may form a second component of the
solution. As already mentioned above in connection with the method,
the two components can each comprise one or more chemical
substances.
[0049] The first substance may comprise a predetermined quantity of
the analyte or of a first reactant which, upon mixing and/or
dissolving the substance in the liquid, undergoes a chemical
reaction which involves at least one second reactant contained in
the liquid and in which the analyte forms as a reaction
product.
[0050] In addition to the analyte or the first reactant, the
substance may comprise an extender which is inert to the further
constituents of the solution to be prepared and also does not
influence the determination of measured values by the measuring
device. Advantageously, the extender is soluble in the liquid, but
this is not required.
[0051] The second reactant may be present in the liquid from the
outset. However, it is also possible for the system to additionally
comprise at least one second capsule which has a wall completely
surrounding an interior and at least one second substance
accommodated within the interior, wherein the wall of the second
capsule is designed to dissolve at least partially in the solvent,
and wherein the second substance comprises the second reactant. In
this case, in order to prepare the solution, both capsules are
added simultaneously or successively to the liquid so that both
reactants dissolve in the liquid. The chemical reaction by which
the analyte is formed then takes place during or after dissolution
of the first and the second reactant in the liquid. The substance
contained in the second capsule may also comprise an inert extender
in addition to the second reactant.
[0052] If the system is configured to prepare a reagent solution to
be added to a sample, the substance contained in the first capsule
may comprise a first substance which is intended for carrying out a
chemical reaction with the analyte.
[0053] The at least one first capsule of the system or all of the
capsules belonging to the system can be enclosed in an outer
packaging in a gas-tight and liquid-tight manner.
[0054] The at least one first capsule of the system or all of the
capsules belonging to the system can be accommodated in a blister
packaging which has a flexible rear wall on which the at least one
first capsule rests and a plastic film molding which is integrally
bonded to the flexible rear wall in such a way that the plastic
film molding and the rear wall form a closed chamber in which the
at least one first capsule is arranged.
[0055] The liquid may be contained in a closed liquid container.
The closure can be secured and/or sealed, for example in such a way
that it is visible when the bottle has already been opened. In an
advantageous embodiment the closed and sealed liquid container can
include an agitator body, which can be used to stir the liquid in
order to accelerate the dissolution of the substance in the liquid.
The agitator body can comprise a magnet, such as a permanent
magnet, which can be driven by means of a magnetic field from
outside the liquid container. As described above, by providing an
agitator body already included in the liquid container of the
system any accidental contamination of the liquid resulting from a
contaminated agitator added to the liquid container by a user is
avoided.
[0056] The components which are packaged in this way and which are
to be brought together to prepare the solution can be marked on the
packaging by the manufacturer. Safety instructions, recommendations
for use, expiry dates or other information on the components and
their use may also be printed on the packaging. This allows
traceability of the prepared solutions. Since the user does not
make any further changes to the composition of the individual
components but only brings them together, quality fluctuations can
be identified on the basis of the identifiers on the packagings and
traced back to the manufacturer of the components. Alternatively or
additionally, the individual capsules may also be marked.
[0057] The liquid may advantageously contain a stabilizer for
inhibiting chemical or photochemical degradation reactions in the
prepared solution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] The present disclosure is explained in further detail below
on the basis of the exemplary embodiments shown in the figures.
They show:
[0059] FIG. 1a shows a schematic representation of a system for
preparing a solution for use with a measuring device according to a
first exemplary embodiment;
[0060] FIG. 1b shows a schematic representation of a capsule of the
system according to FIG. 1a;
[0061] FIG. 1c shows a schematic representation of a blister
packaging with a plurality of capsules of the system shown in FIG.
1a;
[0062] FIG. 2 shows a schematic representation of a measurement
setup for a standard addition method for determining a
concentration of an analyte in a sample of unknown composition;
[0063] FIG. 3 shows a graphical representation of concentration
measured values detected with the measurement setup shown in FIG.
2; and
[0064] FIG. 4 shows a schematic representation of the structure of
an analyzer for determining the concentration of an analyte.
DETAILED DESCRIPTION
[0065] FIGS. 1a and 1b schematically illustrate a system 1 for
preparing a solution for use with a measuring device for
determining a measurand that depends on the concentration of an
analyte in a sample. Such a measuring device is also referred to
below as an analysis measuring device. In the exemplary embodiment
described here, the solution is a standard solution for the
calibration, verification and/or adjustment of an analysis
measuring device. In the example shown here, the system 1 comprises
a closable liquid container 2 with a removable screw cap 3 in which
a liquid 5 is contained, and a capsule 4. The capsule 4 is shown in
FIG. 1b in an enlarged detailed view. The capsule 4 consists of a
wall which completely surrounds an interior and which, in the
exemplary embodiment shown here, is composed of two halves. The
interior contains a substance 6, which is in the form of a solid
powder in the present example. The substance 6 and the liquid 5
contained in the liquid container 2 form two components of the
standard solution to be prepared. Both components can be stored
separately from one another in the system 1.
[0066] In the present example, the substance 6 contains a
predetermined quantity of the analyte, the concentration of which
can be determined by means of the analysis measuring device after
combination with the liquid 5. If the analysis measuring device is,
for example, an analyzer, for example for determining the phosphate
content of a sample, the capsule 4 may contain a phosphate salt.
Optionally, the substance 6 may contain further constituents, for
example an adsorbent which is indifferent to the analysis, for
example diatomaceous earth, or further constituents, such as
stabilizers or buffers or an extender. The liquid 5 contains a
solvent in which the substance 6 is soluble. This solvent can be
water, for example. In addition, the liquid 5 may contain further
constituents, for example stabilizers or buffers. The volume of the
liquid contained in the liquid container is exactly defined. It can
be matched to the quantity of analyte contained in the capsule 4 in
such a way that a specific analyte concentration is produced by
dissolving the substance 6 in the liquid 5. The wall of the capsule
4 is formed of a material which is at least partially soluble in
water and which does not influence the determination of the analyte
by the analysis measuring device. Gelatin, for example, is
suitable.
[0067] In order to prepare the standard solution, the screw cap 3
is removed from the liquid container 2, and the capsule 4 is placed
in the liquid container 2. The liquid container 2 can then be
closed again. The wall of the capsule 4 dissolves in the liquid 5
so that the substance 6 escapes into the liquid 5 and dissolves
therein. In order to accelerate the dissolution of the capsule 4
and the dissolution of the substance 6 in the liquid 5, the liquid
container 2 can be shaken, stirred and/or heated. An agitator body
(not shown) can be included in the closed liquid container 2. For
example, the agitator body can be embodied as a permanent magnet,
so that it can be driven to a rotational movement by a rotating
magnetic field from outside the liquid container 2. The rotating
magnetic field can be provided by a magnetic stirrer.
[0068] The preparation of the standard solution by means of the
system 1 is very simple. The capsule 4 with the predetermined
quantity of the analyte contained in the substance 6 and the liquid
container 2 with the already measured volume of the liquid can be
made available to a user. In this case, the user does not need to
measure the substance quantities used for the preparation of the
standard solution. Since the capsule 4 as a whole is placed in the
liquid 5 already present in the liquid container 2, there is no
risk of errors occurring during the mixing of the components due to
the loss of residues, remaining in a packaging or ampoule, of the
substances used.
[0069] In a variation of the method, it is also possible for two or
more capsules 4 containing the same substance 6 to be dissolved in
the liquid 5 provided in the liquid container 2 in order to obtain
a standard solution of higher concentration. On the other hand, the
prepared standard solution can also be further diluted in a
subsequent step by adding a specific volume of the solvent.
[0070] An advantageous packaging of the capsule 4 of the system 1
shown in FIGS. 1a and 1b is shown in FIG. 1c. Shown schematically
in this case is a blister packaging 7 in which a plurality of
identical capsules 4 are packed together. The capsules 4 in the
example described here contain the same substance 6, each
containing the same predetermined quantity of analyte. In another
embodiment, it is also possible for the capsules contained in the
blister packaging to contain different quantities of the analyte.
It is also possible to mark the packaging or the individual
capsules in order to assign an individual serial number and an
individual substance quantity to each capsule. The label may also
be machine-readable (e.g. a barcode). Traceability may thereby be
optimized. The blister packaging 7 has a flexible rear wall on
which the capsules 4 rest. The rear wall can consist, for example,
of cardboard or a metal foil. The capsules 4 are fixed by a plastic
film molding which is integrally bonded in an edge region to the
flexible rear wall so that the plastic film molding and the rear
wall form a gas-tight chamber for each of the capsules 4 in each
case. The capsules 4 are thus protected from oxygen and moisture,
for example.
[0071] A plurality of variations of the exemplary embodiment
described here is conceivable: The system and method described here
can also be used, for example, for preparing solutions other than
standard solutions, such as for preparing reagent solutions for an
analyzer. In the example described here, only a single capsule is
used. However, it is also possible that the solution to be prepared
is prepared from more than two different components. For example,
two or more capsules with different substances can be dissolved in
a predetermined quantity of a liquid. A corresponding system
suitable for this method comprises a single blister packaging 7 in
which all the capsules to be used are combined. The liquid
container 2 with the liquid 5 does not necessarily have to be
provided as a package with the capsules 4. In a variation of the
exemplary embodiment, it is also possible for the user to measure
the liquid 5 during the preparation of the standard solution and to
present it in a container before adding the capsule 4.
[0072] FIG. 2 schematically shows a measurement setup for
determining a measurand that depends on the concentration of an
analyte in a sample according to the standard addition method. The
measurement setup comprises a measuring device 10 with a probe 11
and a measurement transducer 12 connected to the probe 11. A
container 13 contains a liquid sample 14 of unknown composition.
The probe 11 dips into the sample 14 in order to detect measured
values. In the present exemplary embodiment, the probe 11 is an
ion-selective electrode for measuring ammonium. It produces a
measuring voltage that depends on the ammonium concentration in the
sample and outputs it to the measurement transducer 12 for further
processing. In order to carry out a standard addition method, a
plurality of capsules 4 can now be added successively to the
sample, each containing a substance having a predetermined quantity
of the analyte, in this case an ammonium salt. After each capsule 4
is added and dissolved, a new measurement signal is detected. This
measurement signal characteristic is shown in FIG. 3. In the
diagram, the concentration c of the sample is plotted on the
abscissa and the measurement signal S (here: measuring voltage)
supplied by the measuring device 10 is plotted on the ordinate. The
measurement signal plotted at cu was detected in the sample without
addition. The measurement signal plotted at concentration c1 was
detected after addition to the sample and dissolution of a first
capsule 4, the measurement signal plotted at concentration c2 was
detected after addition to the sample and dissolution of a further,
identical capsule 4, and the measurement signal plotted at
concentration c3 was detected after addition to the sample and
dissolution of a third identical capsule. By linear regression, a
best-fit straight line can be determined based on the measuring
points detected for the concentrations c1, c2, c3, and the zero
point and the value of cu based thereon can be determined by
extrapolation of the straight line.
[0073] The method described here with reference to FIG. 2 is
suitable for measurements according to the standard addition method
with measuring devices which do not consume the sample during the
measurement. These are, for example, electrochemical sensors, such
as potentiometric or amperometric sensors, e.g. ion-selective
electrodes or pH sensors, conductivity sensors or photometric or
spectrometric measuring probes.
[0074] On the other hand, measurements with analyzers are carried
out while consuming the sample. In this case, the sample liquid to
be examined is divided into a plurality of individual samples, and
a measurement signal corresponding to the measurement signal at the
unknown concentration cu is detected with a first sample. In each
case, different quantities of the analyte or analytes are added to
further samples by respectively adding a different number of
identical capsules 4 to the individual parts of the sample. The
analyzer can then detect further measurement signals with the
further samples. The obtained measurement signals are then plotted
completely analogously to the diagram shown in FIG. 3, and a
best-fit straight line is determined and extrapolated. The value of
the unknown concentration cu can be determined by the
extrapolation.
[0075] FIG. 4 shows an analyzer 100 which uses two standard
solutions for calibration and/or adjustment prepared according to
the method described in connection with FIGS. 1a and 1b. The
analyzer 100 is connected to a sample receiver 21 containing a
sample liquid from which it removes a sample in each case in order
to detect a measured value of a measurand that depends on the
concentration of an analyte. The analyzer has a measuring cell 22
which is connected to the sample receiver 21 via a fluid line 23.
The analyzer further comprises a first liquid container 24 which
contains a reagent solution. The liquid container 24 is connected
to the measuring cell 22 via a further liquid line 25. Lastly, the
analyzer 100 has two further liquid containers 2.1 and 2.2, each
containing a standard solution. The liquid container 2.1 contains
the analyte in a first concentration, and the liquid container 2.2
contains the analyte in a second concentration different therefrom.
Both liquid containers 2.1, 2.2 are fluidly connected to the
measuring cell 22.
[0076] The standard solutions contained in the liquid containers
2.1, 2.2 were prepared by adding one or more capsules 4 to a
fixedly predetermined volume of a liquid 5 already presented in the
liquid containers 2.1, 2.2 and by at least partially dissolving in
the liquid 5 the capsule wall and the substance contained therein
and containing the analyte. The same liquid volume was presented in
both liquid containers 2.1, 2.2 in the present example. In order to
produce a higher concentration in the liquid container 2.2, a
larger number of capsules 4 was added to the liquid volume. After
the standard solutions have been prepared, the liquid containers
2.1 and 2.2, which were originally used as storage containers for
the liquid 5, now serve as reservoirs of the analyzer and are
connected to its measuring cell 22 via fluid lines 28, 29.
[0077] In addition to the fluid lines 23, 28, 29, 25, the analyzer
100 comprises valves and/or pumps for transporting the sample, the
standard solutions and the reagent solution (not shown in FIG. 4).
The analyzer 100 has an electronic control and measuring system 26
for controlling the valves and pumps and for detecting and
processing measured values. The measuring cell 22 has a sensor 27
which is designed to carry out a photometric measurement in a
liquid contained in the measuring cell 22, and to output detected
measurement signals to the electronic control and measuring system
26.
[0078] In order to detect a measured value, the electronic control
and measuring system 26 transports a sample from the sample
receiver 21 into the measuring cell 22 and adds a predetermined
quantity of the reagent solution contained in the liquid container
24 to the sample via the fluid line 25. A chemical reaction takes
place in the liquid mixture thus formed, which results in a
reaction product. By means of the sensor 27, the electronic control
and measuring system 26 detects a measurement signal of the sensor
27 that depends on the concentration of the reaction product and
determines a measured value of the measurand based on the
measurement signal. After the measured value has been determined,
the spent liquid is discharged again from the measuring cell 22 via
a discharge line 30.
[0079] The measured value of the measurand is determined from the
measurement signal by means of a calibration function which assigns
measured values to values of the measurement signal. The
calibration function can be checked (calibrated or verified) or
adapted (adjusted) from time to time by means of the standard
solutions. For this purpose, the electronic control and measuring
system 26 can transport standard solution from the liquid container
2.1 or the liquid container 2.2 into the measuring cell 22 instead
of a sample from the sample receiver 21 and detect a measured value
of the measurand in a completely analogous manner as described
above for the sample. A calibration, verification or adjustment can
be carried out on the basis of a comparison of the reference value
of the measurand that is known for the standard solutions and
assumed to be correct with the measured value determined by the
electronic control and measuring system. Since the standard
solutions in the liquid containers 2.1 and 2.2 are prepared
according to the simple and little error-prone method described
above, the calibration, verification and adjustment of the analyzer
with these standard solutions is also little error-prone and allows
reliable measurement operation with little maintenance effort.
* * * * *