Automatic Analysis Apparatus And Method

Abstract

An automatic analysis apparatus includes an indexible table supporting a plurality of liquid sample containers, a stationary reagent liquid container, two off-take tubes, one tube insertable in a presented thereto sample container, the other tube insertable in the reagent container, means for concurrently inserting both tubes repeatedly into their respective containers to provide a flowing stream of segments of liquid sample interspersed by air segments, and a similar stream of segments of reagent. These streams are merged to form stream of liquid and air segments, which stream of liquid and air segments is passed through the sight passageway of a flow cell of a colorimeter. A recorder is coupled to the colorimeter, and may be rendered operational when the sight passageway of the flow cell is fully occupied by liquid.

Description

This invention relates to improved method and apparatus for automatic quantitative analysis of a stream of separate discrete liquid samples especially, but not limited to, the quantitative analysis of blood and other body fluids with respect to known substances therein.

The primary object of the present invention is to improve the precision of quantitative analysis of the samples of liquid. We have discovered that this important object can be accomplished by utilizing as much as possible liquid conduits, such as Teflon tubing, which have non-wetting surfaces instead of wettable surfaces, and by washing the flow cell between the passage of successive samples therethrough with one or more bubbles of air or other gas which is inert to the liquid transmitted through the conduits and through the flow cell, whereby contamination of one sample by another is prevented or is negligible. Further, the sample liquid which is transmitted through the flow cell during the analysis operation, at which time a record of the analysis is made, has a volume at least as large and preferably larger than the volume of the flow cell, so that there is no air in the flow cell when the liquid analysis operation is being performed. More specifically, while one or more segments or bubbles of the air or other gas are introduced into the liquid stream for separating one sample from another in the apparatus and for washing the conduits and the flow cell, it is unnecessary to remove said bubbles before transmission of the treated liquid samples through the flow cell, since the segmentation of the liquid stream by air bubbles is such that a sufficient volume of the treated sample liquid is devoid of air bubbles to enable its analysis as it flows through the flow cell. By reason of the provision of a volume of non-segmented treated liquid sample sufficiently large for analysis, namely, a volume of treated liquid sample at least as large as the volume of the flow cell, blending of segments of the same liquid sample and the need for removal of a comparatively large number of air bubbles are obviated.

Another object of the invention is to provide an apparatus and method of automatic quantitative analysis of a series of liquid samples in a flowing stream in such manner that the quantitative determination in the analysis of each sample is indicated substantially instantaneously during the flow of the treated sample through the flow cell, to the extent that the recorder is able to provide such substantially instantaneous recording, so that the trace on the recorder chart has a square wave form.

In a herein-disclosed preferred embodiment, the apparatus of our invention generally comprises automatic, sample supply means for the provision of the said sample and reagent streams, means to mix the said streams to promote the desired reactions between the said samples and the reagent, and means to automatically analyze the resultant, reacted samples with respect to the relative quantities of predetermined constituents contained therein. The said sample supply means are generally similar to those disclosed in the copending U.S. Pat. No. 3,230,776 to J. Isreeli et al., granted Jan. 25, 1966, and comprise readily interchangeable, indexable carrier means for supporting a plurality of individual liquid sample containers. Separate receptacle means are stationarily positioned laterally of the said carrier means to provide a supply of a suitable reagent for mixing with the said samples to enable the automatic quantitative analysis of the latter with respect to predetermined constituents thereof. First and second liquid take-off means are positioned adjacent the carrier means and above the said reagent receptacle, respectively, and are operative twice, in unison, through the medium of interconnected electromechanical control means as each container is indexed into alignment with the said first take-off means, to concomitantly withdraw two spaced portions of the liquid from the said container and two, correspondingly spaced, suitable quantities of reagent from the said reagent receptacle, respectively, for supply to the said mixing means in the said sample and reagent streams referred to hereinabove. The said mixing means comprise a junction block for the joinder of the two streams, and a mixing coil, each of which is constructed of a material of natural anti-wetting properties to inhibit contamination of one sample by the residue of a preceding sample; while the said automatic analysis means comprise colorimetric analysis apparatus and analysis result recording means operatively associated therewith.

The above and other objects, features and advantages of our invention are believed made clear by the following detailed description thereof taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a top plan view, with parts in section and portions cut away for purposes of illustration, of the sample supply means of the apparatus in our invention;

FIG. 2 is a vertical sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is an isometric projection of the sample and reagent take-off means of our invention in a first position thereof;

FIG. 4 is an enlarged top plan view of the sample and reagent take-off means of our invention in a second position thereof;

FIG. 5 is a cross sectional diagram of the sample and reagent supply lines illustrating the relative positions therein of the respective, correspondingly spaced, sample and reagent streams; and

FIG. 6 is a diagrammatic illustration of the apparatus of our invention.

Referring now to the drawings, and particularly to FIGS. 1-4, the sample supply means of the herein-disclosed preferred embodiment of our invention comprise essentially a housing 11; with indexable turntable assembly 12, turntable drive means 13, sample and reagent take-off assemblies 14 and 16, respectively, take-off assembly actuating mechanisms 17, timing mechanism 18, and reagent receptacle 20, positioned thereon or therewith in the depicted manner.

In the operation of the sample supply means, a plurality of liquid-sample containing cups 23 are mounted as shown in a generally circular array upon the turntable assembly 12 and successively positioned in turn thereby, through the operation of the turntable drive mechanism 13, to positions in alignment with the sample take-off assembly 14. As each said cup is indexed into the said aligned position, the respective sample and reagent take-off assemblies are actuated, by actuating mechanism 17 under the control of timing mechanism 18, with the former functioning to withdraw a portion of the sample from the said cup, and the latter functioning to withdraw a suitable quantity of reagent of corresponding extent, from the reagent receptacle 20. The respective sample and reagent take-off assemblies are then momentarily withdrawn from the said sample cup and reagent receptacle, and then returned thereto for the withdrawal therefrom of a second portion of the same sample from the same sample cup, and another suitable quantity of reagent of corresponding extent from the reagent receptacle. At the conclusion of this second sample and reagent withdrawal, the sample take-off assembly 14 is withdrawn from the said sample cup, and the turntable assembly 12 indexed one cup position to present the next succeeding sample cup in position for withdrawal of the two sample portions therefrom by the said sample take-off assembly 14. Operation continues in this manner until two separate portions of each of the samples have been withdrawn from each of the sample cups in the manner described above. Alternatively, the reagent take-off assembly 16 may be eliminated and the reagent supplied as a constant stream thereof as described hereinbelow.

Turning now in greater detail to the structure of the sample supply means, the turntable assembly 12 comprises a generally circular plate 21 incorporating a generally circular array of cup mounting holes formed adjacent the periphery thereof. The sample cups 23 are removably positioned within these holes by insertion therewithin and include canted bottom portions, in the manner made clear in FIG. 2, whereby any appreciable quantity of liquid within the cup will tend to accumulate at the outer cup edge for convenient removal therefrom by the take-off assembly 14.

The turntable plate 21 is detatchably secured, in a manner made clear in the said co-pending Isreeli et al. application referred to hereinabove, to rotatable support shaft 24, whereby rotation of the said shaft will result in corresponding rotation of the said plate. A Geneva gear plate 32, including notches 35 formed therein as shown, is also secured to the said support shaft, whereby driven rotation of the said Geneva gear plate will result in correspondingly driven rotation of the said support shaft and turntable plate, respectively.

The Geneva gear plate 32 is in turn driven by the engagement therewith of Geneva cam 34 in the manner made clear by FIGS. 1 and 2. The configuration of the said cam 34 is such that every complete revolution thereof will function, in a well-known manner, to advance the Geneva gear plate 32 one notch and then maintain the plate stationary as positioned until the leading edge 36 of the cam driving portion 30 enters the next succeeding notch 35 to repeat the driving process. There is one notch 35 formed in the periphery of Geneva gear plate 32 for each of the array of sample cup mounting holes formed on turntable plate 21, whereby may be appreciated that each complete revolution of Geneva cam 34 will function to advance the turntable plate 21 one sample cup position to in turn index a new sample cup into alignment with the sample take-off means 14. The Geneva cam 34 is fixedly mounted as shown upon drive shaft 37 of drive motor 38, and is rotatably driven thereby to drive the Geneva gear plate 32 and turntable plate 21 as described hereinabove.

A drive gear 39 is also fixedly secured to the motor drive shaft 37, and a driven gear 41 mounted for rotation adjacent thereto and enmeshed therewith as shown, whereby rotation of gear 39 will result in driven rotation of gear 41. A connecting link 42 is pivotally attached as shown adjacent the periphery of driven gear 41 in the manner indicated at 44 in FIG. 1. In the hereindisclosed preferred embodiment, the relative sizes of gears 39 and 41, respectively, are chosen so that one complete revolution of gear 39 will result in two complete revolutions of gear 41.

Each complete revolution of gear 41 results in turn, through the action of connecting link 42 and take-off assembly support post 81 in the manner made clear in the said copending Isreeli et al. application referred to hereinabove, in the movement of the sample and reagent take-off assemblies 14 and 16, respectively, from the positions thereof depicted in solid lines in FIG. 3 to the positions thereof depicted in phantom in the said Figure, and back to the first-mentioned position thereof. Thus may be understood whereby one complete revolution of motor drive shaft 37 will result first in the advancement of turntable plate 21 one cup position, through the action of Geneva cam 34 and Geneva gear plate 32, followed by two successive movements of the take-off assemblies 14 and 16 from the positions thereof depicted in solid lines in FIG. 3 to the positions thereof depicted in phantom in the said Figure, and back to the first-mentioned positions thereof.

The sample take-off assembly 14 comprises a metal crook 75, shaped as shown, with sample supply line 76, preferably of polyethylene tubing, extending therethrough. The reagent takeoff assembly 16 comprises a metal crook 77, shaped as shown, with reagent supply line 78, preferably of polyethylene tubing, extending therethrough. Each of the metal crooks 75 and 77 extend as shown through holes provided therefor in the crook support bar 79 and are maintained properly positioned therewithin by set screws 80 bearing thereagainst. The said crook support bar 79 is in turn positioned atop crook support post 81 and movable therewith, whereby movement of the said support post will result in corresponding movement of the inlet end of the sample and reagent lines 76 and 78, respectively, between the respective positions thereof depicted in FIG. 3. A slot 82 is provided as shown in the housing 11 to enable movement of the crook support post 81 relative thereto. Generally speaking, it may be noted that the respective take-off assemblies 14 and 16 are each movable, through the movement of support post 81, in the same vertical plane. The reagent receptacle 20 is positioned as shown in any convenient manner on the housing 11, as, for example, by attachment screws 83 extending therebetween. The said receptacle comprises hollow interior portions 89 and 90 with inlet and outlet conduits, 85 and 86, respectively, extending therefrom. A dam 87 extends as shown in FIG. 1 between the said hollow interior portions of the receptacle whereby reagent may enter the receptacle through inlet 85, spill over the dam 87 and flow from the receptacle through outlet 86. Outlet 86 is of larger internal diameter than inlet 85 whereby may be appreciated that the reagent will never overflow from the said receptacle, or accumulate to any appreciable degree within hollow interior portion 90 thereof.

In a first position of the respective sample and reagent take-off assemblies, i.e., that depicted in solid lines in FIG. 3, the inlet end of sample-supply line 76 is exposed to the atmosphere in the space immediately adjacent the reagent receptacle 20, while the inlet end of reagent supply line 78 is exposed to the atmosphere within the hollow interior portion 90 of the said receptacle. Thus, with reduced pressure conditions maintained in the said lines in the manner described in detail herein below, air only will be aspirated through the said lines with the said assemblies thusly positioned. In a second position of the said take-off assemblies, i.e., that depicted in phantom in FIG. 3, and normally in FIGS. 2 and 4, the inlet end of the sample supply line 76 is positioned within the sample liquid in the cup 23 positioned in alignment therewith, while the inlet end of the reagent supply line 78 is positioned within the reagent contained within hollow interior portion 89 of the receptacle. Thus, reduced pressure conditions within the said supply lines will result in the aspiration of liquid sample through the former, and reagent through the latter. Since the said supply line inlet ends always move in unison as made clear above, it may be understood whereby the extent, taken along the respective axes of the lines, of sample and reagent, or air, quantities aspirated thereby will always correspond.

The timing mechanism 18 comprises a timing cam 102 driven at constant speed by a non-illustrated, constant speed timer motor through shaft 104. Notches 105 and 107 are formed as shown in the periphery of the timing cam. A two-position switch 106 is positioned as shown on the housing 11 adjacent the timing cam, and includes a switch actuator 108 which extends into contact with the periphery of the cam in such a manner that the said switch is moved to one position thereof when actuator 108 rides on the un-notched periphery of the cam, and to the second position thereof when the said actuator rides within one of the notches 105 or 107. The extent and placement of the said notches 105 and 107 control, through switch 106 and operatively associated control circuitry not illustrated or described in detail in this application, the operation of the drive motor 38 and thus of the turntable and respective sample and reagent take-off assemblies. This control circuitry, and the manner of operation thereof, is described in detail in the said copending Isreeli et al. application. Suffice, however, for purposes of this application to note that, in accordance with the presently preferred form of the invention, the entry of switch actuator 108 into a notch will result in the movement of the sample and reagent take-off assemblies to the positions thereof depicted in solid lines in FIG. 3, whereby air only will be aspirated through the respective sample and reagent supply lines 76 and 78 during the entire time that actuator 108 remains in a notch 105 or 107. Further, the entry of the switch actuator into notch 105 will result in the advancement of the turntable plate 21 one cup position, through the action of Geneva cam and plate 34 and 32, to position a new sample cup in alignment with sample take-off assembly 14. Conversely, when actuator 108 rides out of either notch 105 or 107 on to the unnotched periphery of the timing cam, this will result in the movement of the sample and reagent take-off assemblies to the positions thereof depicted in FIG. 2, whereby sample will be aspirated through the sample supply line 76 and reagent through the reagent supply line 78.

Referring now to FIG. 5, the sample supply line 76 and reagent supply line 78 are depicted in cross section to illustrate the corresponding extent and placement of the respective air, sample, and reagent segments aspirated therethrough through the use of a timing cam 102 of the general configuration depicted in FIG. 1. Segment S of sample and R of reagent represent respectively the end of the second-aspirated segments of a preceding sample, and the correspondingly aspirated reagent segment. Air segments A.sub.1 would then be aspirated through the sample and reagent supply lines as the switch actuator 108 rode within timing cam notch 105 to position the sample and reagent take-off assemblies in the manner depicted in solid lines in FIG. 3 in the manner set forth above. Concurrently therewith, the turntable plate 21 would be advanced one cup position to present a new sample cup 23 in alignment with the sample take-off assembly 14. As switch actuator 108 rides out of notch 105 onto the unnotched peripheral portion 109 of the timing cam 102, the sample and reagent take-off assemblies are moved to the positions thereof depicted, for example, in FIG. 2 whereby the first-aspirated segment S.sub.1, of the new sample, and the correspondingly aspirated reagent segment R.sub.1 are provided. As cam portion 109 completes its travel beneath actuator 108, the latter rides into notch 107 whereby the respective take-off assemblies are again returned momentarily to the positions thereof depicted in solid lines in FIG. 3 and segments of air A.sub.2 aspirated therethrough. As soon as actuator 108 rides out of notch 107 onto the un-notched portion 112 of the timing cam, the respective take-off assemblies are returned to the position thereof of FIG. 2. Since no movement of the turntable plate 21 occurred during the aspiration of air segments A.sub.2, the same sample cup 23 is still in alignment with the sample take-off assembly 14, whereby the second-aspirated segment S.sub.2 of the said sample, and the correspondingly aspirated reagent segments R.sub.2, are provided. The entire process is then repeated as the switch actuator reenters notch 105 to return the take-off assemblies to the positions thereof of FIG. 3 to aspirate air segments A.sub.3, advance the turntable another cup position to position a new sample cup 23 in alignment with the sample take-off assembly, whereby the first and second-aspirated segments S.sub.4 and S.sub.5 of the new sample, and the correspondingly aspirated reagent segments R.sub.4 and R.sub.5, spaced as shown by air segments A.sub.4, may be provided in the same manner. In accordance with the presently preferred form of the invention, reagent supply line 78 is chosen of greater inner diameter than the sample supply line 76, whereby each of the reagent segments will be of greater volume than the correspondingly aspirated sample segment, although of the same lateral extent within the said supply lines.

In FIG. 6 a proportioning pump is indicated diagrammatically at 130, and may be of the nature disclosed in U.S. Pat. No. 2,893,324. The said pump comprises resiliently flexible pump tubes 132 and 134 which are connected as shown to the sample and reagent supply lines 76 and 78, respectively, and have substantially the same internal diameters as the said lines. In pumps of this nature, the said pump tubes are compressed progressively along their lengths by non-illustrated rollers which are moved in compressing engagement with the tubes longitudinally thereof. The relative quantities of fluids pumped through the said tubes may thus be understood to depend upon the respective internal diameters thereof since the tubes are longitudinally compressed, at the same linear speed, by the said rollers.

The pump tubes are connected as shown by lines 136 and 138 to flow passages 142 and 144 of junction block 140. The said junction block is preferably of a material of very tight molecular structure with natural non-wetting properties, as for example "Kel-F," whereby the formation of a residue of a sample flowing therethrough which could contaminate the next succeeding sample, is effectively inhibited. Flow passages 142 and 144 merge within the junction block into flow passage 146, whereby may be understood the manner in which the correspondingly aspirated sample and reagent segments, described above in conjunction with the description of FIG. 5, may be joined together to form a larger segment of sample and reagent. This joining together of the said correspondingly aspirated sample and reagent segments of course requires that the flow path lengths from the inlet ends of the respective sample and reagent supply lines, to the juncture of flow passages 142 and 144 at flow passage 146, be substantially equal because the said segments flow through the said supply lines and pump tubes at the same velocity as described above. To this effect, reagent supply line 78 is depicted as somewhat curved to illustrate the need for the equalization of the said flow path lengths.

A mixing coil 150, preferably of Teflon for the same non-wetting reasons discussed above, is provided and connected to flow passage 146 of the junction block 140 by line 148 extending therebetween. The said mixing coil may, if desired, be placed in a heating bath, and functions to thoroughly mix, and promote the desired reaction between, the combined sample and reagent segments resulting from the juncture of flow passages 142 and 144 in the junction block.

Colorimetric analysis apparatus are generally indicated at 159 and comprise a source of light 156, collimating lenses 157 and 158, optical filter 160, flow cell 154, light responsive detecting means 162, and a chart recorder operative to record analysis results connected to the detecting means through line 164. In accordance with a presently preferred form of our invention, the said colorimetric analysis apparatus may be similar to those disclosed in U.S. Pat. No. 3,031,917.

The said flow cell 154 is connected to the outlet of the mixing coil 150 by line 152, whereby the reacted sample segments may be flowed therethrough for colorimetric analysis, and the results thereof by stylus 167 on recorder chart 168 in a manner made clear in the said U.S. Pat. No. 3,031,917.

The supply of each sample in two separate segments functions to effectively inhibit the contamination of a sample by the residue of a preceeding sample. Thus, with further reference to FIGS. 5 and 6, it may be understood whereby sample segment S.sub.1 will function to remove any residue from segment S of the preceeding sample from the interior walls of sample supply line 76, pump tube 132, connecting line 136, and flow passage 142 of the junction block 140. After combination of sample segment S.sub.1 and reagent segment R.sub.1 in flow passage 146 of the junction block, the resultant combined sample and reagent segment S.sub.1 R.sub.1 will function to remove any residue of the preceeding combined segment SR from flow passage 146, connecting line 148, mixing coil 150, connecting line 152, and flow cell 154. Thus may be understood whereby the smaller or first-aspirated segment of each sample, and the air segments provided on either side thereof, function as cleansing agents to prevent the contamination of the succeeding larger, second-aspirated segment of the same sample, by the residue of a preceeding sample remaining in the apparatus. Thus, the supply of a segment of a wash liquid after each sample, or of additional air to further segment each sample or wash liquid segment to increase the cleansing power thereof, is made unnecessary. Further, the elimination of the air segmentation of each sample segment makes unnecessary the provision of means to remove the air prior to the introduction of the sample segment to the flow cell for the colorimetric analysis thereof.

In accordance with a presently preferred form of our invention, it is only the larger, or second-aspirated segment of each sample, as for example sample segments S.sub.2 or S.sub.5 of FIG. 5, which are subjected to colorimetric analysis for analysis result recording purposes; the smaller or first-aspirated sample segments, and adjacent air segments, being provided primarily for the cleansing effect thereof as described above. To this effect, switch means 175 may be provided, if preferred, in electrical line 164 and controlled, as indicated, by the operation of the sample supply assembly, to complete the circuit from the detecting means 162 to the chart recorder 166 only when a said larger or second-aspirated sample segment, mixed and reacted of course with the correspondingly aspirated reagent segment, flows through the flow cell. Alternatively, the supply of power to the colorimetric analysis apparatus as a whole may be effected only when a larger sample segment flows through the flow cell.

In the analysis operation, there is no air or other gas in the flow cell and during that operation the volume of sample liquid, treated for colorimetric analysis, which is transmitted through the flow cell, is at least as large as and preferably larger than the volume of the flow cell. Each volume of reagent-treated sample liquid is in an intermediate position in the flowing stream between a leading gas bubble and a trailing gas bubble as the stream flows through the conduit to the flow cell for said analysis operation, and said gas bubbles are disposed, respectively, between said volume of treated sample liquid and a down stream portion of the same treated sample liquid and between said volume of treated sample liquid and an upstream portion of the same treated sample liquid. During the flow of this volume of reagent-treated liquid sample, free of air or other gas, through the flow cell, the quantitative indication of the analysis by the trace of the recorder stylus on the chart paper reaches its peak value almost instantaneously, i.e., as fast as the stylus can move, so that the continuous trace on the chart paper, corresponding to the seriatim analyses of a series of treated sample liquids in the stream, is of a square wave form.

The use of an air-segmented supply of reagent is especially desirable in cases wherein the available quantity of each sample is very limited, as for example in the case of automatic analysis on the blood of infants. In these cases, since the supply of sample is small, the internal diameter of sample supply line 76 must also be small whereby it becomes quite difficult to introduce sufficient air through the said supply line to properly separate the respective sample segments through to the analysis apparatus after the combination thereof with the reagent. Thus, the major portion of the air for sample segment separation is introduced as the air segments in the reagent supply line 78 as described above.

In cases, however, wherein the available quantity of each sample is not strictly limited, it is possible to use a sample supply line 76 of sufficient internal diameter to provide air segments of sufficient extent to properly separate the sample segments, even after the mixture thereof with reagent. In such cases, the air segmenting of the reagent supply stream is not necessary whereby the reagent take-off assembly 16 may be eliminated and the inlet end of reagent supply line 78 merely submerged in any convenient source of reagent, as, for example, reagent receptacle 20, and a continuous stream of reagent supplied through the said supply line, pump tube 134 and connecting line 138, to flow passages 144 and 146 of the junction block 140 for combination therewithin with the respective air and sample segments supplied thereto through connecting line 136.

It will be understood that all of the tubing except the resiliently compressible pump tubes, here indicated at 132 and 134, are made of Teflon which, as is well known, is non-wetting. This non-wetting characteristic is maintained permanent in the operation of the apparatus by the absence of wetting agents in the sample liquids and by the omission from the sample treating reagents of any wetting agent. As the pump tubes are comparatively small in length as well as in internal diameter and are made of Tygon, there is no significant residual deposit of sample on the inner surfaces of the pump tubes, especially since each sample which flows through the pump tube is followed by one or more bubbles of air or other gas inert to the sample liquid as above indicated.

While we have shown and described the preferred embodiment of the invention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described, and that certain changes in the form and arrangement of parts and in the specific manner of practicing the invention may be made without departing from the underlying idea or principles of this invention within the scope of the appended claims.

Claims

1. A method of automatic quantitative analysis of a plurality of liquid samples each disposed in a respective container, wherein said samples are off-taken by an off-take device and are transmitted successively as a flowing stream to an analytical device including a flow cell having a sight passageway, said method including:

for each sample container in succession, coupling said off-take device to such sample container, and in alternation therewith, to a source of an inert fluid immiscible with said liquid samples, thereby to off-take a segment of each of said liquid samples and intermediate segments of the inert fluid;

transmitting said segments of the liquid samples and inert fluid as a flowing stream to said analytical device; and

passing said flowing stream including segments of both the liquid samples of inert fluid through the sight passageway of the flow cell, the volume of at least one homogeneous portion of each liquid sample being at least

2. A method according to claim 1 comprising the further steps of:

dividing each liquid sample by further inclusions of said inert fluid which is immiscible with the liquid sample, and

introducing said further inclusions of said inert fluid in the liquid samples immediately at the point of introduction of the liquid samples

3. A method according to claim 1 wherein the liquid samples are stored in respective sample containers and are withdrawn therefrom by an off-take tube coupled to a pump means, comprising the further steps of:

alternately immersing and withdrawing said off-take tube into and from a same sample container to expose said off-take tube to the atmosphere

4. A method according to claim 2 comprising the further steps of:

dividing each liquid sample into a leading segment of relatively short length and a following segment of relatively long length, said following segment having a volume at least equal to the volume of the sight passageway of the flow cell,

said leading segment providing a conduit cleansing function and said

5. A method according to claim 3 comprising the further steps of:

combining a flowing stream of reagent liquid with said flowing steam of liquid samples, and

before such combination, dividing said flowing stream of reagent with inert fluid segments such that upon combination the inert fluid segments in both

6. Apparatus for the automatic quantitative analysis of a plurality of liquid samples each disposed in a respective container, comprising:

an indexible table for supporting said sample containers,

off-take means including an off-take tube coupled to a pump means,

means for intermittently indexing said table to sequentially present each of such containers to said off-take means,

means for inserting said off-take tube into a presented thereto container and alternatively exposing said off-take tube to the atmosphere;

whereby said pump means draws through said off-take tube a flowing stream of successive liquid samples spaced apart by intermediate segments of air;

colorimeter means including a flow cell having a sight passageway and associated means for analyzing liquid samples passing through the sight passageway of the flow cell; and

conduit means for passing the flowing stream of successive liquid samples spaced apart by intervening segments of air through the sight passageway

7. Apparatus for the automatic quantitative analysis of a plurality of liquid samples, said apparatus comprising:

a colorimeter including a flow cell having a sight passageway and an inlet and an outlet through which liquid samples are transmitted for the quantitative analysis thereof in respect to the same known ingredient in each sample,

conduit means for the passage of the liquid samples through the sight passageway of said flow cell,

means for introducing a sample treating liquid and a segmentizing, inert, immiscible, fluid into said conduit and thereby forming in said conduit means at a location upstream of said flow cell a fluid stream containing segments of treated sample liquid spaced from each other in the direction of stream flow by intervening immiscible fluid segments,

said conduit means having an outlet connected to said inlet of said flow cell and devoid of other openings downstream of said upstream location to pass said fluid stream including treated liquid samples and said immiscible fluid segments through said sight passageway of said flow cell for analysis of said treated liquid samples with said accompanying cleansing of the sight passageway by said segmentizing fluid; and

means for measuring the optical density of said treated liquid samples

8. Apparatus according to claim 7 wherein said flow cell has a sight passageway, and said colorimeter further includes means for providing a signal indicative of the optical density of said treated liquid samples passing through said sight passageway;

a chart recorder coupled to said signal providing means; and

means for interrupting the operation of said recorder except when said sight passageway is fully occupied by a treated liquid sample, the volume of said treated liquid sample being at least equal to the volume of said

9. Apparatus according to claim 6 wherein said colorimeter further includes means for providing a signal responsive to the optical density of the contents of said sight passageway;

a chart recorder coupled to said signal providing means, and

means for interrupting the operation of said recorder except when said sight passageway is fully occupied by a sample liquid segment, the volume of said sample liquid segment being at least equal to the volume of said

10. A method of automatic quantitative analysis of a plurality of liquid samples each disposed in a respective container, wherein said samples are off-taken by an off-take device and are transmitted successively as a flowing stream to an analytical device including a colorimeter having a flow cell with a sight passageway, said method including:

for each sample container in succession, coupling said off-take device to such sample container, and in alternation therewith, to a source of an inert gas immiscible with said liquid samples, thereby to off-take a segment of each of said liquid samples and intermediate segments of the inert gas;

transmitting said segments of the liquid samples and inert gas as a flowing stream to said analytical device;

passing said flowing stream including segments of both the liquid samples and inert gas through the sight passageway of the flow cell, the volume of at least one homogeneous portion of each liquid sample being at least equal to the volume of the sight passageway of the flow cell;

measuring the optical density of the liquid samples passing through the sight passageway of the flow cell; and

interrupting the operation of said recorder except when said portion of each sample having a volume at least equal to the volume of the sight

11. A method of automatic quantitative analysis of a plurality of liquid samples each disposed in a respective container, wherein said samples are off-taken by an off-take device and are transmitted successively as a flowing stream to an analytical device including a flow cell having a sight passageway, said method including:

for each sample container in succession, coupling said off-take device to such sample container, and in alternation therewith, to a source of an inert gas immiscible with said liquid samples, thereby to off-take a segment of each of said liquid samples and intermediate segments of the inert gas;

transmitting said segments of the liquid samples and inert gas as a flowing stream to said analytical device;

passing said flowing stream including segments of both the liquid samples and inert gas through the sight passageway of the flow cell, the volume of at least one homogeneous portion of each liquid sample being at least

12. A method according to claim 11 comprising the further steps of:

dividing each liquid sample by further inclusions of said inert gas which is immiscible with the liquid sample, and

introducing said further inclusions of said inert gas in the liquid samples immediately at the point of introduction of the liquid samples into the

13. A method according to claim 12 wherein the liquid samples are stored in respective sample containers and are withdrawn therefrom by an off-take tube coupled to a pump means, comprising the further steps of:

alternately immersing and withdrawing said off-take tube into and from a same sample container to expose said off-take tube to the atmosphere between successive immersions into a same sample container.