U.S. patent number 3,783,696 [Application Number 05/206,442] was granted by the patent office on 1974-01-08 for automatic volume control pipet.
Invention is credited to Charles M. Coleman.
United States Patent |
3,783,696 |
Coleman |
January 8, 1974 |
AUTOMATIC VOLUME CONTROL PIPET
Abstract
An automatic filling capillary pipet having a tubular body
defining an elongated bore having a fluid entry end. The interior
surface of the tubular body having a first zone with hydrophobic
means for resisting wetting by aqueous liquids. The tubular body
interior surface having a second zone which is hydrophilic with
respect to aqueous fluids. Introduction of an aqueous fluid into
the elongated bore will effect retention therein of a predetermined
volume of aqueous fluid proportional to the cross section of the
bore and the length of the second zone. In one embodiment the
hydrophobic first zone originates at a position spaced from the
fluid entry end and the hydrophilic second zone is disposed between
the first zone and the fluid entry end. In another embodiment a
hydrophobic third zone is disposed intermediate the hydrophilic
second zone and the fluid entry end.
Inventors: |
Coleman; Charles M.
(Pittsburgh, PA) |
Family
ID: |
22766402 |
Appl.
No.: |
05/206,442 |
Filed: |
December 9, 1971 |
Current U.S.
Class: |
73/864.02;
141/94; 138/DIG.3; 138/45; 138/46; 138/146; 141/31; 141/98;
604/207; 422/922; 422/514 |
Current CPC
Class: |
B01L
3/021 (20130101); Y10S 138/03 (20130101) |
Current International
Class: |
B01L
3/02 (20060101); B01l 003/02 (); G01f 023/02 ();
G01f 019/00 () |
Field of
Search: |
;141/18,31,94,98 ;23/292
;128/233 ;73/425.4P,425.6,426 ;138/146,DIG.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Morse, Jr.; Wayne A.
Attorney, Agent or Firm: Silverman; Arnold B.
Claims
I claim:
1. An automatic filling capillary pipet comprising
a unitary tubular body having an elongated bore and a fluid entry
end,
the interior surface of said tubular body having a first zone with
hydrophobic means for resisting wetting by aqueous fluids,
said tubular body interior surface having a second zone which is
hydrophilic with respect to aqueous fluids,
said hydrophobic first zone originating at a position spaced from
said fluid entry end,
said hydrophilic second zone being disposed between said first zone
and said fluid entry end,
said hydrophobic means including a coating on the interior surface
of said first zone of a material selected from the group consisting
of silicones, fluorocarbons and hydrocarbons,
graduation means disposed adjacent the abutting edges of said first
and second zones, and
at least one of said hydrophobic means and said hydrophilic means
being a substantially continuous coating on said tubular body
interior, whereby introduction of an aqueous fluid into said
elongated bore will effect retention therein of a predetermined
volume of said aqueous fluid related to the inner cross section of
said bore in said second zone and the length of said second zone
and said fluid volume being less than the full volume of said
elongated bore.
2. An automatic filling capillary pipet comprising
a unitary tubular body having an elongated bore and a fluid entry
end,
the interior surface of said tubular body having a first zone with
hydrophobic menas for resisting wetting by aqueous fluids,
said tubu ar body interior surface having a second zone which is
hydrophilic with respect to aqueous fluids,
said hydrophobic first zone originating at a position spaced from
said fluid entry end,
said hydrophilic second zone being disposed between said first zone
and said fluid entry end,
a third zone disposed intermediate said second zone and said fluid
entry end having hydrophobic means, whereby said second zone will
retain a predetermined volume of an aqueous fluid intermediate said
first and third zones at a position spaced from said fluid entry
end,
said hydrophobic means in said first and third zones being an
internal coating of a material selected from the group consisting
of silicones, fluorocarbons and hydrocarbons, and
at least one of said hydrophobic means and said hydrophilic means
being a substantially continuous coating on said tubular body
interior, whereby introduction of an aqueous fluid into said
elongated bore will effect retention therein of a predetermined
volume of said aqueous fluid related to the inner cross section of
said bore in said second zone and the length of said second zone
and said fluid volume being less than the full volume of said
elongated bore.
3. An automatic filling capillary pipet comprising
a tubular body composed of glass and having an elongated bore and a
fluid entry end,
the interior surface of said tubular body having a first zone with
hydrophobic means for resisting wetting by aqueous liquids,
said tubular body interior surface having a second zone which is
hydrophilic with respect to aqueous fluids,
said hydrophobic first zone originating at a position spaced from
said fluid entry end,
said hydrophilic second zone being disposed between said first zone
and said fluid entry end,
a third zone disposed intermediate said second zone and said fluid
entry end having hydrophobic means,
said hydrophobic means in said first and third zones being an
internal coating of a material selected from the group consisting
of silicones, fluorocarbons and hydrocarbons,
said hydrophobic coatings in said first and third zones being
substantially coextensive with said zones,
first calibration means disposed adjacent the abutting edges of
said first and second zones, and second calibration means disposed
adjacent the abutting edges of said second and third zones, whereby
introduction of an aqueous fluid into said elongated bore will
effect retention in said second zone of a predetermined volume of
said aqueous liquid related to the inner cross section of said bore
in said second zone and the length of said second zone.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an automatic filling capillary pipet
which is adapted to receive a predetermined volume of an aqueous
liquid without requiring manual effort to precisely align the
liquid upper level with a pipet calibration line.
2. Description of the Prior Art
In numerous laboratory uses small diameter or micro-tubular pipets
are emloyed in order to receive and transfer relatively small
quantities of liquid. These pipets are frequently composed of
tubular galss and provided with at least one volume indicating
graduation in order to permit the receipt and discharge of a
precisely measured volume of fluid. Liquid is frequently introduced
into the pipet by suction as by a dropper type bulb or suction hose
attached to the upper end thereof. Also, liquid is frequently
introduced into the pipet by capillary action such as is
encountered in withdrawing blood from a finger puncture in a
patient.
One of the difficulties encountered in conventional pipets is the
need to precisely monitor the inward flow of the fluid into the
pipet. Inward flow must be terminated at the precise moment when
the meniscus of the liquid in the pipet is positioned at the
desired calibration line on the pipet in order to insure receipt
and delivery of a specific predetermined volume of the fluid. This
procedure is, of necessity, relatively slow, cumbersome and
somewhat inefficient and requires a high degree of skill on the
part of the user. In view of the rapid acceleration in the annual
volume of clinical laboratory tests which employ pipets coupled
with the need to maintain or improve the accuracy of such tests and
the need to free skilled laboratory personnel for other
responsibilities, there remains a substantial need for an automatic
control pipet which is easy to operate, even in the hands of
relatively unskilled individuals.
There remains, therefore, a need for a pipet which is adapted to
automatically and rapidly transfer a precise predetermined quantity
of liquid into the hollow interior without involving manual
technique and human measurement coupled with all of the resultant
undesirable features.
SUMMARY OF THE INVENTION
The above-described need has been met by the present invention. The
present invention provides an automatic filling capillary pipet
which has an elongated tubular body provided with a fluid entry
end. The interior surface of the tubular body has a first zone with
hydrophobic means for resisting wetting by aqueous fluids. The
interior surface also has a second zone which is hydrophilic with
respect to aqueous fluids. As a result, introduction of an aqueous
fluid into the elongated bore through the fluid entry end will
result in retention of a volume of fluid which is proportionate to
the cross section of the tubular body bore and the length of the
second zone. In one form of the invention the hydrophobic first
zone originates at a position spaced from the fluid entry end and
the hydrophilic second zone originates at or adjacent the fluid
entry end and extends continuously to the first zone. Graduation or
calibration means may be provided intermediate the first and second
zones.
In another embodiment of the invention a third zone which has
hydrophobic means is interposed between the second zone and the
fluid entry end. This results in a predetermined volume of the
aqueous fluid being received intermediate the first and third
zones.
In one preferred form of the invention the hydrophobic means is a
coating of material selected from the group consisting of
silicones, fluorocarbons and hydrocarbons.
It is an object of this invention to provide an automatic filling
capillary pipet which is adapted to receive and retain for
subsequent discharge a predetermined volume of an aqueous fluid
without the need for manual control.
It is another object of this invention to provide a disposable
capillary pipet which is adapted to both "to contain" and "to
deliver" pipet deliveries.
It is another object of this invention to provide an automatic
filling capillary pipet wherein the volume which will automatically
be received and retained in the pipet may be precisely determined
and be employed for a wide range of volumes.
These and other objects of the invention will be more fully
understood from the following description of the invention, on
reference to the illustrations appended hereto.
BREIF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a form of capillary pipet of this
invention.
FIG. 2 is a cross sectional illustration of the capillary pipet of
FIG. 1 taken through 2--2 of FIG. 1.
FIG. 3 is a cross sectional illustration of the pipet of FIG. 1
taken through 3--3 of FIG. 1.
FIG. 4 is an elevational view of a modified form of pipet of this
invention .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates generally to automatic filling pipets
of various types. For convenience of reference herein, the term
"capillary pipet" will be used to refer generically to various
forms of pipets regardless of whether or not they are to be filled
by capillary action. The terms "aqueous fluid" and "aqueous liquid"
as used herein shall refer to fluids which have a substantial
percentage of water on a volume basis and the use of such terms
shall expressly include blood and urine, as well as chemically
modified blood and urine specimens and other fluids having a
substantial water concentration.
Referring now more specifically to FIG. 1 throug 3, there is shown
an elongated capillary pipet which has a tubular body 2 defining an
elongated bore 4. The tubular body 2 has a fluid entry opening 6 at
one end and a venting opening 8 at the other end. The tubular body
2 has a first zone 12 which has hydrophobic means for resisting
wetting by aqueous fluids. Intermediate the first zone 12 and the
fluid entry opening 6 is a second zone 14 which has a surface which
is hydrophilic with respect to aqueous fluids. The elongated bore 4
in the second zone 14 preferably has an average internal diameter
of about 0.1 to 1.5 millimeters. In the form illustrated a
graduation mark 16, which may conveniently be a mark applied to the
exterior surface of the tubular body 2 or a line etched into the
same, indicates the line of division between first zone 12 and
second zone 14.
In the form illustrated in FIGS. 1 through 3, the tubular body is
composed of glass and second zone 14 need not be coated as the
surface is naturally hydrophilic with respect to aqueous fluids.
First zone 12 is provided with a continuous interior coating 20
which consists of a material which is hydrophobic with respect to
aqueous fluids. While the coating material may be any suitable
hydrophobic material, the preferred materials are those selected
from the group consisting of silicones, fluorocarbons and
hydrocarbons. Among the hydrocarbons which may be economically
employed is petroleum jelly. Also, chloro or alkoxy silanes such as
methyl trichlorosilanes or methyl trimethoxysilanes, for example,
may be used to siliconize the first zone 12. The interior coating
in zone 12 should be substantially continuous and may be of any
thickness which maintains adequate continuity for the coating to
function in a hydrophobic fashion and yet maintains the opening in
longated bore 4 sufficiently to permit venting therethrough. If
desired, the edge of capillary pipet adjacent fluid entry opening 6
may be coated with a hydrophobic material in order to resist
adherence of superfluous fluid to the tube edge.
One convenient means of applying the hydrophobic coating to zone 12
is to provide a solution of the coating material and immerse the
pipet in the solution to the precise depth to which coating is
desired. The fluid solution, for example, may be methyl
trimethoxysilane in water or methyl trichlorosilane in a suitable
organic solvent, such as toluene. The pipet may then be removed and
permitted to dry.
In using the pipet shown in FIGS. 1 through 3, one may rely on
capillarity to introduce the aqueous fluid into the pipet. In
effecting aqueous fluid introduction, the fluid entry opening 6 is
placed in contact with the aqueous fluid desired to be introduced
into the pipet interior. The fluid will automatically advance to
graduation marker 16, preferably by capillarity, and will not be
retained above the marker 16 as the fluid will not wet the surface
of first zone 12. As a result, the fluid will instantaneously and
automatically enter and be retained within the pipet interior in a
precisely controlled volume determined by the length of second zone
14 and the interior cross sectional dimension of second zone 14. In
this fashion, the time consuming and somewhat inaccurate human
dependent approach to pipet filling is dispensed with and efficient
reliable automatic volume recipt is insured.
The pipet shown in FIGS. 1 through 3 may be employed in a "to
contain" pipet delivery. In this form of delivery, when it is
desired to transfer the blood or other aqueous fluid, the aqueous
fluid can be washed out of the pipet by means of the liquid into
which the transferred aqueous lfuid is to be received.
Another approach to the general embodiment shown in FIG. 1 is to
employ a tubular material which is generally hydrophobic such as a
plastic, and permit the material to serve as the first zone while
the interior of the second zone is treated in order to render it
hydrophilic. For example, the interior of the second zone of a
plastic tube might be oxidized to render it hydrophilic.
Referring now to FIG. 4, another embodiment of the invention will
be considered. In this form of the invention the pipet has an
elongated tubular body 30 generally similar to that of the pipet of
FIG. 1. Tubular body 30 has a fluid entry opening 32 and a venting
opening 34. The body interior surface, which will generally be
circular in cross section, has a first zone 36 which has
hydrophobic means, a second zone 38 which is hydrophilic and a
third zone 40 which is also hydrophobic. In this form of the
invention an aqueous liquid entering fluid entry opening 32 will
travel upwardly to second zone 38 and be retained therein. It is
noted that a graduation mark 42 separates first zone 36 from second
zone 38. Similarly, a graduation mark 44 separates second zone 38
from third zone 40. The volume of fluid retained within the pipet
tubular body 30 will be proportionate to the length of second zone
38 and the interior cross sectional dimension of second zone
38.
The pipet shown in FIG. 4 may be used in a "to deliver" type pipet
delivery. In this form of delivery the predetermined volume of
aqueous fluid which is retained within second zone 38 may be
transferred into a receiving vessel by blowing into one end,
generally venting opening 34 of tubular body 30. In this fashion,
the predetermined precise volume of aqueous fluid is received
within the pipet interior in automatic fashion and is effectively
delivered.
As was true with the first embodiment of the invention, if desired
the tube may be composed of a naturally hydrophobic material with
second zone 38 being treated to establish a hydrophilic surface. In
view of the location of second zone 38, however, it will generally
be more convenient to employ a tube composed of a hydrophilic
material. Also, it will be appreciated that with all embodiments of
this invention the naturally hydrophilic or naturally hydrophobic
zones of a pipet may be treated in order to improve these desired
characteristics within specific zones.
While the pipet of this invention is not dimensionally limited, it
whould be noted that it is particularly suitable for use with
micro-capillary pipets which have an average internal diameter in
the liquid retaining zones of less than about 2 millimeters and
preferably have an average internal diameter in these zones of
about 0.1 millimeter to 1.5 millimeters and are used in receiving
volumes of liquids of about 1 to 100 microliters. The average
internal diameter range of about 0.1 to 1.5 millimeters is
preferred for maximum precision and increased repeatability of
meniscus contour, with further improvement being obtained as the
diameter is reduced within this range.
It should also be noted that while the examples herein described
have referred expressly to gass and plastic pipets and these are
the preferred materials, the invention is not so limited and other
materials and combinations of materials may be employed.
While for purposes of simplicity of illustration the pipets shown
have a substantially continuous transverse internal bore dimension
throughout their longitudinal extent, if desired variations in
cross sectional dimension at various locations may be provided. A
small bore intake tube with or without a capillary tip, for
example, may be employed. Also, a small bore upper portion may be
provided if desired.
It will, therefore, be appreciated that the automatic volume
control capillary pipet of this invention is adapted to eliminate
the undesirable and relatively slow and inaccurate human
participation in volume control and provide for simple, automatic
precise introduction and retention of a predetermined volume of an
aqueous fluid. This may be accomplished in an economical fashion
with simple chemical treatment of a portion or all of the pipet
interior. The invention is particularly suited for use with
disposable small bore pipets including capillary glass pipets.
Also, no special equipment is required for the use of the pipets,
nor is specialized skill required as the human factor has been
substantially completely eliminated. Finally, the system is readily
adapted for use in conventional discharge techniques and
accelerates the sampling and analytical testing processes.
Whereas particular embodiments of the invention have been described
above for purposes of illustration, it will be evident to those
skilled in the art that numerous variations of the details may be
made without departing from the invention as defined in the
appended claims.
* * * * *