Sample introduction system for nonsegmented continuous flow analysis

Abstract: Sample injection system for nonsegmented, continuous flow analysis comprising an inlet channel (2), an analyzer channel (3) and a carrier stream channel (4), connected in a confluence point (1), an aspirating pump (6) in the analyzer channel, a carrier stream pump (5) in the carrier stream channel with a higher capacity than the aspirating pump (6), and an analyzer (7). In a first step prior to the sample injection, the carrier stream pump (5) forwards carrier stream to the confluence point (1), the aspirating pump (6) sucks carrier stream from the confluence point (1), and an outflow of carrier stream drains through the inlet channel (2). In a second step, the carrier pump (5) is stopped, the inlet end (10) of the inlet channel (2) is brought in contact with the sample solution (14), and the aspirating pump (6) sucks sample into the inlet channel (2) and the analyzer channel (3). In the third step, the carrier pump (5) is restarted, whereby the sample in the analyzer channel (3) is aspirated into the analyzer (7), and all the sample in the inlet channel (2) is pressed out into the waste (8). The analyzer (7) may be a flow-through detector, dialyzer, or any other apparatus for analysis. The performance can also be made as a multi-channel system for simultaneous analysis of several components in different analyzers. In the above embodiments, the sample container must be connected and disconnected at precisely defined times. In order to avoid this, a second channel (17) can be added to the carrier pump (5) to make a double channel, the second channel (17) being connected to an outlet (16) from the inlet channel (2). The sample passes through the analyzer (7) and exits through the aspirating pump (6). By instead connecting the second channel (17) of the double channel pump to the analyzer channel (3) at a point between the analyzer (7) and the aspirating pump (6), the sample can be sucked in through the analyzer (7) and after analysis be forced back the same way.

Description: The successful operation of any flow injection analysis (FIA) system requires injection of a well-defined sample zone into the analyzer channel, where the zone disperses in a controlled manner on its way towards and through the detector to be measured upon (cf US Patents 4 022 575, 4 177 677, 4 224 033, 4 314 824, 4 227 973, 4 315 754 and 4 399 225, 4 399 102 and 4 597 298). The injection devices designed for this purpose so far can be divided into two categories: (a) volume based injection; and (b) time based injection, or a combination thereof. In category (a) the injection is based on the physical entrapment of sample solution into a geometrically well-defined volumetric cavity and subsequent transfer (injection) of the thus formed sample zone into a nonsegmented carrier stream (cf the above-mentioned FIA monograph and US Patents 4 177 677 and 4 224 033). Category (b) is based on aspiration of sample solution at a constant flow rate for a fixed period of time into a well-defined section of a flow-through channel, a volumetric channel, from where the metered sample zone is injected into a nonsegmented carrier stream by a combination of hydrostatic and hydrodynamic forces - the so called hydrodynamic injection procedure (cf US Patent 4 597 298 and DE-A-3 242 848). DE-A-3 242 848 describes a hydrodynamic sample injection system. It comprises a first confluence point connected to three channels: a sample channel with a sample source and a possible sample pump; a carrier channel with a carrier source and a carrier pump; and a volumetric conduit; and a second confluence point connected to the other end of the volumetric conduit; to an analyzer channel with an analyzer pump; and to a waste channel with a possible waste pump. The sample amount is determined by the volume of the volumetric channel. Injection systems for gas chromatography are disclosed by Posposil, US-A-4 464 940 for injection of gases. Such systems, however, cannot be used for incompressible liquids. The purpose of the present invention is to obtain a simplified and improved development of the hydrodynamic injection approach, which is based on the use of a confluence point at which a well-defined sample zone is formed by means of the alternate motion of sample and carrier streams. The invention concerns a sample flow injection analysis system for nonsegmented continous flow analysis (FIA) comprising pumping devices, three liquid through channels connected at a single confluence point and a detector the three channels connected to the confluence point being a sample inlet channel with an inlet end and a sample source connectable thereto; a carrier channel with a carrier pump and a source for the carrier solution; and an analyzer channel with an aspirating pump and the detector, the carrier pump being in the form of a two-channel pump constituting said carrier pump and a further pump with its one channel being said carrier channel and its other channel being a further channel which is arranged from a branch point in the sample inlet channel to the further pump and from there to a drain. The invention further concerns a sample flow injection analysis system for nonsegmented continous flow analysis (FIA) comprising pumping devices, a first, a second, and a third liquid-through channel connected at a single confluence point, and a detection device, the first liquid-through channel being a sample inlet channel with a sample source connectable thereto, the second liquid-through channel being an analyzer channel with an aspirating pump and a detector for determination of substances in the sample, said analyzer channel having a branch point between the analyzer and the aspirating pump, connected to a carrier channel with a carrier pump and a source for the carrier solution; and the third liquid-through channel being a branch sample channel connected to a further pump and from there to a drain, the carrier pump and the further pump forming a two-channel pump with its one channel being said carrier channel and its other channel being said branch sample channel. The invention also concerns a method of injecting a sample at nonsegmented continous flow analysis, using a confluence point connecting three channels, i.e. a sample inlet channel with a movable source for the sample; a carrier channel with a carrier pump having a pumping rate x and a source for the carrier solution; and an analyzer channel with an aspirating pump having a pumping rate y and a detector for determination of substances in the sample, which method is characterized in that the pumping rate x > y and that in a first STEP prior to the injection of the sample, the carrier pump pumps carrier solution to the confluence point, the aspirating pump aspirates part of the carrier solution and the remainder of the carrier solution goes to a waste through the sample inlet channel, in a second STEP the sample source is contacted with the sample inlet channel, the carrier pump is stopped and the aspirating pump aspirates sample through the sample inlet channel past the confluence point and into the analyzer channel in a predetermined amount, and in a third STEP the carrier pump is started again, and the sample amount in the analyzer channel which has passed the confluence point is aspirated into the detector and determined. The invention further concerns a method of injecting a sample at nonsegmented continous flow analysis, using a confluence point connecting three channels, i.e. a sample inlet channel with a movable source for the sample, an analyzer channel with an aspirating pump having a pumping rate y and a detector for determination of substances in the sample, said analyzer channel having a branch point, between the analyzer and the aspirating pump, connected to a carrier channel with a carrier pump having a pumping rate x and a source for the carrier solution; and a branch sample channel with a further pump having a pumping rate z, the carrier pump and the further pump forming a two-channel pump with its first channel being said carrier channel and its second channel being said branch sample channel, which method is characterized in that the pumping rate z > x > y and that in a first STEP all the pumps are operating with the sample source being either connected or disconnected to the sample inlet channel, the carrier pump pumping carrier solution into the system, the aspirating pump sucking out part of the carrier solution and the further pump sucking the remainder of the carrier solution through the analyser to the confluence point and pumping out a mixture of carrier solution and sample or air, in a second STEP the sample source is connected to the sample inlet channel, the two-channel pump is stopped and the aspirating pump sucks sample inte the sample inlet channel past the confluence point, into the analyzer channel, through the detector, where it is analyzed, and in a third STEP the two-channel pump is started again and the carrier solution is forced through the carrier channel to the branch point, the part of the carrier solution not being suckt out through the aspirating pump passing through the analyzer channel and forcing the sample back through the detector to the confluence point and from there out through the branch sample channel. Figs. 1A-C, 2, 3 and 4 show various embodiments of the hydrodynamic injection system according to the invention. The principle is best explained by reference to Figs. 1A, 1B and 1C, where 1 is the confluence point; 2 is the inlet channel; 3 is the analyzer channel; 4 is the carrier stream channel; 5 is the carrier stream pumping device; 6 is the analyzer channel pumping device; 7 is the analyzer situated in the analyzer channel; 8 is the waste receptacle; 9 is the sample source; 10 is the inlet end of the inlet channel; 11 is the reservoir of the carrier stream fluid; 12 is the waste outlet for the analyzer channel; 13 is the carrier solution; 14 is the sample solution; and 15 is the injected sample zone. The operational cycle of the system comprises three sequential steps, each of which is represented in Figs. 1A-C, details being as follows. STEP 1 (Fig. 1A), i.e. prior to injection of sample solution; Pump P1(5) pumps carrier stream solution 13 towards the confluence point 1 at a higher volumetric pumping rate than pump P2(6) which by its mode of action aspirates the liquid of the analyzer channel 3, that is, pumps away from the confluence point, resulting in a positive outflow of carrier stream solution through the inlet channel 2 and via 10 into waste 8, while sections 3 and 7 concurrently are filled with carrier stream solution flowing towards waste 12. STEP 2 (Fig. 1B), i.e. sample aspiration: Pump P1(5) is stopped and the column of carrier stream solution 13 in the carrier stream channel 4 is held still, while pump P2 is maintained operating thereby aspirating sample solution 14 from container 9 which now has been moved into contact with inlet end 10. STEP 3 (Fig 1C), i.e. sample injection: While pumping by P2(6) is maintained, pumping by pump P1(5) is resumed and sample source 9 is withdrawn. Thus, all sample solution 14 to the left of the confluence point 1 is forced in countercurrent fashion from the sample inlet into waste 8, while all sample solution in the form of an injected sample zone 15 to the right of the confluence point 1 is aspirated, followed by carrier stream solution 13, through the analyzer channel 3 and into the analyzer 7 for further treatment and measurement. As both pumps P1 and P2 continue pumping, all sample material is eventually expelled from the system either via the inlet channel 10 or via the Pump P2(6), through the channel 3, the analyzer 7 and the waste outlet 12, and the system is thus reestablished for the next sampling period, being now, in fact, in STEP 1 again. While the explanation given above describes the principles of the new, proposed mode of injection, it should be noted that variations on this theme are possible. For instance, if a sample is too concentrated to be processed by the analyzer 7, an additional dilution may be executed at the confluence point 1 by decreasing - during the duration of STEP 2 - the pumping rate of the inflowing carrier stream below the aspiration rate of pump P2(6), instead of stopping P1 entirely. Furthermore, if the carrier stream would contain a reagent with which the sample solution should be mixed for the purpose of an intended chemical reaction, which is to be subsequently monitored in the analyzer 7, an effective mixing can thus be obtained during the passage of material through channel 3 to the analyzer 7. The analyzer 7 may be a flow-through detector, or may even comprise a system of channels, detectors, dialyzer, or gas diffusion and pumping units - the only restriction being that the net inflow rate fulfills the conditions stipulated above, i.e. the flow rate through the analyzer 7 is governed solely by the aspiration flow rate of pump P2(6). It is of interest to mention that the counter-current movement of liquid through channel 2 may be used with advantage if the sampled liquid contains particulate matter which has to be removed prior to automated assay. By placing a filtering device at position 10, particles may be retained on the filter during aspiration of the sample and discarded during the subsequent discharge period (STEP 3). It is important to emphasize that the repetitive movements of sample solution 14 at the inlet end 10 must be executed in harmony with the countercurrent movement of liquid through channel 2 in such a way that under no circumstances air will enter the analyzer channel 3. For operation of the injection system in that case where pump P1(5) is stopped during the sampling period (STEP 2), the injected sample volume S v can be calculated from the stopped time interval T of pump P1(5) and the aspiration rate Q of pump P2(6) and by correcting for the expelled sample liquid contained within the inlet channel 2 of volume l v , i.e.: S v = (T.Q) - l v . A modified process is illustrated in Fig 2. The same reference numerals have been used for components corresponding to those in Fig 1. In this embodiment the timing of the mechanical connection and disconnection of the sample container to and from the channel 2 must be precise. The pumping rate for incoming carrier solution is designated x and that for outgoing analyzed sample and carrier solution is designated y, where x is greater than y. In STEP 1, the system is washed with carrier solution. Both pumps 5 an 6 are in operation and the sample channel 2 is opened freely to the drain. In STEP 2, the pump 5 is stopped, the sample container 9 is connected and the sample 9 is drawn through the channel 2, and a predetermined quantity is drawn past the point of confluence 1. In STEP 3, the pump 5 is started, the sample container 9 is disconnected and the carrier solution breaks the sample stream at the confluence point 1 and thus delimits the measured sample quantity which is then sucked through the channel 3 to the analyzer 7. In the channel 2, the remaining sample is forced out and replaced by carrier solution. In the embodiment shown in Fig 3, the sample 14 need not be disconnected at any specific point in time. At a branch point 16 in the sample channel 2, there is a branch channel 15 which leads to the pump 17 and from there to the drain. The pump for the carrier solution is in the form of a double channel peristaltic pump 5,17. The pump rates for pumps 5, 6 and 17 are x, y and z, wherein z > x > y. Since peristaltic pumps with a certain pulsation are used here, a filter 18 is placed in the channel 3 to prevent any air or particles from entering the analyzer 7. In STEP 1, all of the pumps are operating, and the sample container 9 can be connected or disconnected. The pump 5 pumps carrier solution into the system, pump 6 pumps carrier solution and any sample residue out, and pump 17 pumps out a mixture of carrier solution and sample or air. In STEP 2, the pump 5,17 is stopped, and pump 6 sucks sample into the channel 2 and a certain predetermined quantity of sample past the confluence point 1 in channel 3. The sample container 9 is connected during this step. In STEP 3, the pump 5,17 is restarted, and pump 5 pumps carrier solution through the channel 4 into channels 3 and 2 forcing the measured sample quantity through the detector 7 where analysis takes place. The pump 17 pumps via branch point 16 and channel 15 out carrier solution from channel 2, and sample solution, if the sample container is still connected, or air, if it has been removed. Fig 4 shows an embodiment where the sample is sucked into the coil and the analyzer, and after measuring is sucked back the same way. The pump rates are for 5, 6 and 17, x, y and z, respectively, wherein z > x > y. In STEP 1, all of the pumps are operating, and the sample container can be connected. The channels are rinsed of previous samples by the carrier solution. In STEP 2, the pump 5,17 is stopped while pump 6 continues to operate. The sample is sucked from the sample container 9 through the channel 2 past the point of confluence 1 through the coil 15 and the analyzer 7 and past the branch point 16. The time interval for STEP 2 can also be adjusted so that only a portion of the sample passes through the analyzer 7. In STEP 3, the pump 5,17 starts and carrier solution flows through channel 4 to the branch point 16, and from there a portion is sucked out to the drain by pump 6 while the rest forces the sample back through the analyzer 7 and the coil 19, past the confluence point 1, through the channel 15 and out to the drain. Since the pump rate z is greater than x - y, sample 14, or air if the sample container is removed, will be sucked up via the channel 2, the confluence point 1, and in mixture with the carrier solution through channel 15 and pump 17 to the drain. The filter in this embodiment can be left out or placed after the coil 19. Reagent can be added together with the carrier flow or separately through a coupled dozing device. The advantages of the new injection system may be summarized as follows: (1) No moving parts in contact with the handled liquids. (2) Lesser mechanical complexity than in any valving system. (3) Ideally suited for microminiaturization. (4) Ideally suited for integration into microconduits, which without any mechanical moving parts are easy to make, inexpensive and disposable. (5) The sample volume - and the sample dispersion - is adjusted by timing sequences rather than by adjusting the volume of a cavity in a valve, that is, electronic computer control rather than mechanical control of the dispersion is exerted. (6) Less complex than "classical" hydrodynamic injection - only two pumping tubes are required, and the streams do not have to be balanced. (7) Countercurrent operation of the inlet part of the system, and/or the detector, allowing clean-up and/or filtration.

Claims: A sample flow injection analysis system for non-segmented continous flow analysis (FIA) comprising pumping devices (5,6), three liquid through channels connected at a single confluence point and a detector (7) the three channels connected to the confluence point being a sample inlet channel (2) with an inlet end (10) and a sample source (9) connectable thereto; a carrier channel (4) with a carrier pump (5) and a source (11) for the carrier solution (13); and an analyzer channel (3) with an aspirating pump (6) and the detector (7), characterized in that the carrier pump is in the form of a two-channel pump (5,17) constituting said carrier pump (5) and a further pump (17) with its one channel being said carrier channel (4) and its other channel being a further channel (15) which is arranged from a branch point (16) in the sample inlet channel (2) to the further pump (17) and from there to a drain. A sample flow injection analysis system according to Claim 1, characterized in that the sample source (9) is a container or a continuously flowing stream. A sample flow injection analysis system according to Claim 1, characterized in several analyzer channels (3) from the confluence point (1), each with a separate detection device (7). A sample flow injection analysis system for non-segmented continous flow analysis (FIA) comprising pumping devices, a first, a second-, and a third liquid-through channel connected at a single confluence point, and a detection device, the first liquid-through channel being a sample inlet channel (2) with a sample source (9) connectable thereto, the second liquid-through channel being an analyzer channel (3) with an aspirating pump (6) and a detector (7) for determination of substances in the sample, characterized in that said analyzer channel (3) has a branch point (16) between the analyzer (7) and the aspirating pump (6), the branch point being connected to a carrier channel (4) with a carrier pump (5) and a source (11) for the carrier solution (13); and in that the third liquid-through channel is a branch sample channel (15) connected to a further pump (17) and from there to a drain, the carrier pump (5) and the further pump (17) forming a two-channel pump (5, 17) with its one channel being said carrier channel (4) and its other channel being said branch sample channel (15). A sample flow injection analysis system according to anyone of Claims 1-4, characterized by a device for dozing reagent to the system for reaction with the sample. A method of injecting a sample at nonsegmented continous flow analysis, using a confluence point (1) connecting three channels, i.e. a sample inlet channel (2) with a movable source (9) for the sample (14); a carrier channel (4) with a carrier pump (5) having a pumping rate x and a source (11) for the carrier solution (13); and an analyzer channel (3) with an aspirating pump (6) having a pumping rate y and a detector (7) for determination of substances in the sample, characterized in that the pumping rate x > y and in a first STEP prior to the injection of the sample, the carrier pump (5) pumps carrier solution to the confluence point (1), the aspirating pump (6) aspirates part of the carrier solution and the remainder of the carrier solution goes to a waste (8) through the sample inlet channel (2), in a second STEP the sample source (9) is contacted with the sample inlet channel (2), the carrier pump (5) is stopped and the aspirating pump (6) aspirates sample (14) through the sample inlet channel (2) past the confluence point (1) and into the analyzer channel (3) in a predetermined amount, and in a third STEP the carrier pump (5) is started again, and the sample amount in the analyzer channel (3) which has passed the confluence point (1) is aspirated into the detector (7) and determined. A method according to Claim 6, characterized in that in the second step the carrier pump (5) is not stopped completely, but its pumping rate is reduced so that x < y, whereby the sample flowing past the confluence point (1) into the analyzer channel (3) is diluted with carrier. A method according to Claim 6, characterized in that the carrier pump (5) is made as a two-channel pump (5,17) constituting said carrier pump (5) and a further pump (17) with its first channel being said carrier channel (4) and its second channel being a further channel (15) which is arranged from a branch point (16) in the sample inlet channel (2) to the further pump (17), said further pump 17 operating at a pumping rate z, where z > x > y, and that in the first STEP all the pumps are operating with the sample source (9) being either connected or disconnected to the sample inlet channel (2), the carrier pump (5) pumping carrier solution into the system, the aspirating pump (6) sucking out carrier solution and the further pump (17) pumping out a mixture of carrier solution and sample or air, in the second STEP the sample source (9) is connected to the sample inlet channel (2), the two-channel pump (5, 17) is stopped and the aspirating pump (6) sucks sample inte the sample inlet channel (2) and a certain predetermined amount of sample is forced past the confluence point (1) and into the analyzer channel (3), and in the third STEP the two-channel pump (5,17) is started again and the carrier solution is forced past the confluence point (1) thus cutting off the predetermined amount of sample from the confluence point and pushing it through the detector (7) where it is analyzed. A method of injecting a sample at nonsegmented continous flow analysis, using a confluence point (1) connecting three channels, i.e. a sample inlet channel (2) with a movable source (9) for the sample (14), an analyzer channel (3) with an aspirating pump (6) having a pumping rate y and a detector (7) for determination of substances in the sample, said analyzer channel (3) having a branch point (16), between the analyzer (7) and the aspirating pump (6), connected to a carrier channel (4) with a carrier pump (5) having a pumping rate x and a source (11) for the carrier solution (13); and a branch sample channel (15) with a further pump (17) having a pumping rate z, the carrier pump (5) and the further pump (17) forming a two-channel pump (5, 17) with its first channel being said carrier channel (4) and its second channel being said branch sample channel (15), characterized in that the pumping rate z > x > y and that in a first STEP all the pumps are operating with the sample source (9) being either connected or disconnected to the sample inlet channel (2), the carrier pump (5) pumping carrier solution into the system, the aspirating pump (6) sucking out part of the carrier solution and the further pump (17) sucking the remainder of the carrier solution through the analyser to the confluence point (1) and pumping out a mixture of carrier solution and sample or air, in a second STEP the sample source (9) is connected to the sample inlet channel (2), the two-channel pump (5, 17) is stopped and the aspirating pump (6) sucks sample inte the sample inlet channel (2), past the confluence point (1), into the analyzer channel (3), through the detector (7), where it is analyzed, and in a third STEP the two-channel pump (5,17) is started again and the carrier solution is forced through the carrier channel (4) to the branch point (16), the part of the carrier solution not being sucked out through the aspirating pump (6) passing through the analyzer channel (4) and forcing the sample back through the detector (7) to the confluence point (1) and from there out through the branch sample channel (15). A method according to anyone of Claims 6-9, characterized in that reagent is dozed into the system for reaction with the sample.

Inventors: HANSEN ELO HARALD, RUZICKA JAROMIR, HANSEN, ELO HARALD, RUZICKA, JAROMIR
Applicants: BIFOK AB
Application year: 1986
Main classification: G01N35
IPC codes: G01N35