US 3883414 A
The present invention provides a new device and method for automatically detecting and regulating and/or removing concentrations of various substances in aqueous solutions, such as for example, regulating the degree of pollution of urban rivers or industrial effluents, by electrolyzing the ions of these substances dissolved therein through a flow electrolyte cell; then depositing and condensing or dissolving, automatically and with high accuracy, continuously or discontinuously, according to the respective electrolytic potentials of these substances.
Description (OCR text may contain errors)
United States Patent Fujinaga et a].
[451 May 13, 1975 DETECTOR OF TRACE SUBSTANCE IN WATER Inventors: Taitiro Fujinaga, Kyoto; Katuo Miura, Matsudo, both of Japan Assignee: Shibata Kagaku Kikai Kogyo Kabushiki, Tokyo, Japan Filed: Mar. 27, 1974 Appl. No.: 455,326
Foreign Application Priority Data Mar. 28, I973 Japan 48-34679 US. Cl. 204/195 R; 204/1 T; 222/548 Int. Cl. GOln 27/46 Field of Search 204/1 T, 195 R, 195 H;
References Cited UNITED STATES PATENTS l2/l956 Oflutt et al 204/l T 3,067,384 12/1962 Sorg 204/l95 H 3,4l0,763 ll/l968 Capuano 204/l95 H 3,556,950 l/l97l Dahms 204/195 R Primary ExaminerT. Tung Attorney, Agent, or Firm-Armstrong, Nikaido & Wegner 57 ABSTRACT The present invention provides a new device and method for automatically detecting and regulating and/or removing concentrations of various substances in aqueous solutions, such as for example, regulating the degree of pollution of urban rivers or industrial effluents, by electrolyzing the ions of these substances dissolved therein through a flow electrolyte cell; then depositing and condensing or dissolving, automatically and with high accuracy, continuously or discontinuously, according to the respective electrolytic potentials of these substances.
13 Claims, 14 Drawing Figures gg gm m 1 3% 3,883,414
SHEET 3 BF 5 cmcenrrafion FIG. 5
g v v concentration concen frat/0n SHEET 4 CF 5 time DETECTOR OF TRACE SUBSTANCE IN WATER BACKGROUND OF THE INVENTION Recently pollution of urban rivers and industrial effluents from plants and mines and the like have become increasingly serious. The environmental damage inflicted by heavy metals contained in the polluted water has created a grave public health hazard.
In an effort to prevent such hazards, efforts are being made to control environmental pollution through enactment of industrial effluent control laws, which set water quality standards and pollution standards in general. In connection therewith, conventionally the fol lowing three methods of water quality inspection are presently available:
According to one of these methods, an appropriate color developer is added to the sample to be tested or analysed; the tone and density of the color thus developed are checked against a reference sample. This colorimetric method is called Absorptiometry.
According to another method, the light from a hollow cathode lamp suitable for the sample to be tested, is passed through a hydrogen or acetylene flame. The sample is then continuously sprayed into this same flame, and pollutant substances in the sample become atomic. If one or more pollutants are present, a component of the light from the hollow cathode lamp which has a wavelength specific to that of the pollutant to be detected is absorbed and in consequence the amount of this specific component of light which goes into a detector diminishes. Thus, the content of that sample substance can be determined from the preset gauge line for the wavelength specific to that subtance. This is called Atomic Absorptiometry.
According to a third method, a trace of quick silver (mercury) is dripped into an electrolyte containing the sample to be tested, When a current vs. voltage curve is drawn for the mercury, acting as an electrode, a stepped-curve is obtained showing the potential posi tion representing the substance and the current volume representing the concentration of the substance. From these values, the composition of the substance and its concentration can be known. This is called d-c Polarography. a-c Polarography and Rectangular Wave Polarography are other variations of the Polarography technique.
Under the Japan Industrial Standard JlS-K-OIOZ for analysis of copper, cadmium and lead, the ranges and standard deviation in their quantitative analysis are specified as follows:
2 As seen from this table, Absorptiometry and Polarography are practically on the same level of sensitivity, while Atomic Absorptiometry might be called the most sensitive in view of smallness of sample quantity required.
The Atomic Absorptiometry method, however, is not suitable as a continuous monitor because of the necessity to use a specific light source-lamp for each substance to be detected. The lamps, therefore, have to be switched for each different substance which is very inconvenient. Also, a hot flame of hydrogen or acetylene is needed, posing a safety hazard.
Further, whichever of these methods may be employed, the measurement gives merely data relative to the reference sample, thus one does not obtain absolute values of the substance measured. Moreover, none of these methods can condense and detect within the same device trace quantities of pollutants existing in the sample, nor can it detect the effect of purification of the sample electrolyte, nor can it eliminate irrelevant contents from the sample being tested.
in cases of the first and the third listed methods, the sensitivity to the substance in the sample, as can be readily seen from Table l, is low and the results of measurement are not very accurate.
SUMMARY OF THE INVENTION The present invention provides a new method and apparatus, free from the adverse limitations of conventional means, for high-accuracy quantitative and qualitative analysis of substances, even in minute concentrations dissolved in urban rivers or industrial effluents from plants and mines and of solutions in general which may contain substances desired to be monitored.
above 0.025mg Polargraphy ac above 0.005mg Polargraphy (rect. wave) 3 electrolytes by making the inventive device itself act as a purification means.
Also, according to the present invention, the invention device can be made fully automatic, thereby significantly reducing the time and labor needed for measurement and, in addition, rendering the whole device reliable and safe.
To attain these and other objects, and advantages, according to the present invention a supporting electrolyte containing a sample of the substances to be detected is passed through the inventive apparatus in a flow path comprising succesively from the charging side the following components:
I a flow electrolyte cell equipped with a potentiostat;
2 a sample injector unit; and,
3 a series of one or more flow electrolyte cells each with a potentiostat. The sample injector. with or without electrical connection to the potentiostat of the first occuring of the two (or more) flow electrolyte cells on the sample discharging side (down stream) of the injector is connected to a program-controller. At a point located in the path of the sample-supply means to the sample injector there is installed a flow electrolyte cell, equipped with a potentiostat, having the function of purifying the sample thereby leaving only the desired sub stance in the sample prior to entry of the sample into the sample injector. Hence the electrolyte cell is sometimes referred to hereinafter as a purification cell.
Each of the flow electrolyte cells located downstream of said sample injector in the flow path are connected to a potentiostat capable of superimposing an alternat ing current (ac) on its respective cell.
BRIEF DESCRIPTION OF THE DRAWINGS Reading the following detailed account with reference to the attached drawings will give a full understanding of the invention, its components, and an embodiment thereof. The present invention is susceptible of various modifications or changes in details to comprise other embodiments as well.
In the attached drawings:
FIG. 1 is a comprehensive block diagram illustrating an embodiment of the device according to the present invention FIG. 2 is a sectional view explaining a flow electrolyte cell.
FIG. 3 is a circuit diagram of the flow electrolyte cell employed as a chromatography cell, showing its working principle.
FIG. 4 is a graph showing the comparative state of dissolution of tin and lead in a hard-to-dissolve hydrochloric acid solution in a flow electrolyte cell of the present invention.
FIG. 5 is a graph showing the state oftin and lead dissolved in a flow electrolyte cell of the invention in which a-c is superimposed over the electrolytic potentials of tin and lead.
FIG. 6 is a circuit diagram of a potentiostat used in the present invention as connected to an 11-0 superimposing circuit.
FIG. 7 is an exploded isometric view of a sample injector of the present invention.
FIG. 8 is an illustrative scheme of an electromagnetic valve.
FIG. 9 is a graph showing the state of copper and lead dissolved when the sample concentration has been continuously registered by a recorder using the two flow electrolyte cells on the supporting electrolytedischarging side of the sample injector of the invention, as the detector cell.
FIG. 10 is a graph showing the state of copper and lead dissolved when the sample concentration has been registered discontinuously in the same way as in FIG. 9, with the sample charged at definite intervals.
FIG. 11 illustrates the programming scheme in the case of FIGS. 5 and 10.
FIG. 12 is a graph showing the dissolved states of cadmium, lead and copper as registered by a recorder when a trace sample has been condensed using one of the flow electrolyte cells on the supporting electrolytedischarging side of the sample injector as a chromatography column and where measurement has been made using the other flow electrolyte cell as the detector cell.
FIG. 13 illustrates the programming scheme in the case of FIG. 12.
FIG. 14 illustrates the circuit diagram and working principle of the automatic potential switch circuit in the case of FIG. 13.
DETAILED DESCRIPTION OF THE INVENTION In the figures in the attached drawings, in which a de tailed account of an embodiment of the inventive detector of trace substance in water is given, the same symbols represent the same things.
In FIG. 1, a supporting electrolyte in the supporting electrolyte reservoir I is charged at a constant rate into the flow pipe 2 by a constant-output pump 3 installed in said pipe 2 and then discharged out through a flow meter 4.
In the path of said flow pipe 2, beginning from the side of said constant-output pump 3 there are arranged in succession: a flow electrolyte cell 6 for purification of the supporting electrolyte equipped with a potentiostat 5 (hereafter the cell sometimes being referred to as the filter cell), a sample injector 7, and two flow electrolyte cells 10, ll respectivly provided with potentiostats 8, 9.
The filter cell 6 and the flow electrolyte cells 10, II are structured as shown in FIG. 2, wherein to the two ends of a column membrane 12 made of conventional porous glass are attached non-porous lead terminal col umns WEI and WE2, the column membrane and lead columns being filled with a working electrode 13 composed of glassy carbon grains. Both ends of said terminal columns are blocked with fritter glass, one end having an inlet 14 and the other an outlet 15 for the supporting electrolyte. The outside of the column membrane is wound with, for example, a platinum wire, forming an auxiliary electrode 18, which is housed within but spaced from a casing 21 designed to contain a depolarizing electrolyte, which casing is provided with an inlet 19 and an outlet 20 for the depolarizing electrolyte to enter and discharge. The tip of a salt bridge 23 electrically links with a reference electrode 22 penetrating the casing 21, containing the depolarizing electrolyte, coming close to the column membrane 12, but without reaching it. The lead terminal column WEI and WE2, are each fitted with a working electrode lead wire 24 and 25. The working electrode lead wires, 24, 25, and an auxiliary electrode lead wire 26 are connected to the flow electrolyte cell 10. A reference electrode lead wire 27 is connected to the reference electrode 22 and respectively connected to three potentiostats 5, 8, and 9. The inlet 14 and the outlet 15 for the supporting electrolyte in the filter cell 6 and the flow electrolyte cells 10, ll communicate with the flow pipe 2; and each inlet 19 and outlet 20 for each depolarizing electrolyte in all cells communicate with a common flow pipe 28 for the depolarizer, which will be described later.
The potentiostats 5, 8, 9 serve to give an appropriate potential to the working electrode 13 in reference to the reference electrode 22, thereby controlling the current between the auxiliary electrode 18 and the working electrode 13.
A sample reservoir 29 is constantly supplied with the sample to be analyzed from a pump 30, the excess sample being discharged through a discharge pipe 31 out of the sample reservoir.
The sample solution in the reservoir 29 goes first through an impurity-removing flow electrolyte cell (for purification) 34 equipped with a potentiostat 33 which is installed at a point along sample-supply pipe 32, which pipe then delivers the pure sample to the sample injector 7. Supporting electrolyte is also charged into the sample injector from flow pipe 2 by force ofa constantoutput pump 35, ultimately to mix with the sample, as will be described later. Said potentiostat 33 and said flow electrolyte cell 34 used in this embodiment are of the entirely same constitution as the abovementioned potentiostats 5, 8, 9 and flow electrolyte cells 6, 10, 11. As described later, this process of sample injection may be continuous or discontinuous; in the case of discontinuous injection the sample is dis charged out of the injector device according to a predetermined program. while the supply is suspended.
The sample injector 7 is constituted as shown in FIG. 7. Namely, between two disks of the same profile 36, 37 there is inserted (tightly as to prevent leakage but allow rotation) a sample-supply disk 38 of the same profile with a desired thickness matching the sampling amount as will be later described. A rotatable solenoid coil 39 is fixed-centered to the outside surface of the disk 36 with the solenoid stem 40 extending through the center of the disk 36 and fixed to the center of the samplesupply disk 38. The sample injector is actuated as follows: each time the rotatable solenoid coil 39 receives an electric signal programmed by a programcontroller 54, described later, the solenoid stem 40 and the sample-supply disk 38 rotates by 60.
Three orifices 41, 42, 43 open with 60 spacing at the same location on the same circumference of the two disks 36, 37 while six through-holes 44 open with 60 spacing on the same circumference of the samplesupply disk 38. Thus. every time the sample-supply disk 38 is rotated by 60 by the rotatable solenoid 39 and stem 40, one through-hole 44 of the sample-supply disk 38 comes to align with corresponding orifices of the disks 36, 37. For instance, when the solenoid coil 39 receives an electrical signal the supply disk 38 is rotated by 60 and as a result, through-hole 44 of the sample-supply disk 38 aligns with the orifice 4] of the disk 36 and with the orifice 41 of disk 37. Upon receiving another signal sample-supply disk 38 is rotated by 60 and as a result the through-hole 44, which has so far aligned with the orifice 41 of the disk 36 and of the disk 37, comes to align with the orifice 42 of the disk 36 and of the disk 37.
When the solenoid coil 39 receives another electric singal, in the same way as above the through-hole 44 aligns with the corresponding orifices 43 of both disks 36 and 37. Orifices 41 of both disk 36 and 37 are respectively connected to the sample-supply pipes 32, 32a; the orifices 42 of both said disks are respectively connected to the flow pipes 2, 20 for the supporting electrolyte; and the orifices 43 of both said disks are respectively connected to nitrogen gas-supply pipes 45 and 45a which will be described later.
The sample-supply pipe 32a connected to the orifice 41 of the disk 37 may, if desired, be switched to either sample-supply pipe 32b or through a three-way tube 47 to the flow pipe 2b for the supporting electrolyte, by means of a switching electromagnetic valve 46 manually or automatically by a programcontroller 54 to be described later. The flow pipe 20 connected to the orifice 42 is connected via a three-way tube 47 to the flow pipe 2b; and the nitrogen gas-supply pipe 45a connected to the orifice 43 is connected to an appropriate discharge pipe.
The depolarizing electrolyte in the depolarizing electrolyte reservior 48 is sent by the constant-output pump 49 inserted in the depolarizer flow pipe 28, to the side of the auxiliary electrode 18 of the filter cell 6 and the flow electrolyte cells 10, ll, 34; it goes through the inlet 19 into the depolarizing electrolyte casing 21. After constantly restoring and replenishing the function of the electrolyte for the auxiliary electrode 18, the depolarizing electrolyte continuously flows to the outlet 20, to be discharged out of the device.
The nitrogen gas supplied from a nitrogen gas tank 50 is divided by the 2-way branch off pipe 51 inserted in the nitrogen gas-supply pipe 45. One divided part of the supply passes through the flowmeter 52 for flow rate control and regulation and is then forced into and through the sample reservoir 29, to dispel any dissolved oxygen in the sample solution. The other part of the gas supply divided by the branch-off pipe 51 also passes through a similar flowmeter 53 and, depending on the action of an electromagnetic valve 55 automatically switched by a programcontroller 54, to be described later, serves to force the supporting electrolyte remaining in the through-hole 44 of the samplesupply disk 38 in the sample injector 7 out of that device, or if so programmed it may be into the supporting electrolyte reservoir l, to dispel dissolved oxygen in the supporting electrolyte.
In FIG. 8 the details of the electromagnetic valve are illustrated. Nitrogen gas passing out of the flowmeter 53 normally flows from the nitrogen gas-supply pipe 450 of the flowmeter 53 to the nitrogen gas-supply pipe 45b of the supporting electrolyte reservoir 1; but when the electromagnetic valve 55 receives an electric signal from the program-controller 54, the flow of the nitrogen gas changes from the nitrogen gas-supply pipe 450 of the flowmeter 53 to the nitrogen gas-supply pipe 450 of the sample injector 7.
The potentiostats 8 and 9 are linked to a reporting device, such as a conventional two-pen recorder 56, which makes it possible, with use of the flow electrolyte cells 10, H as the detector cell, to make simultaneous output recordings of both the potentiostats 8, 9 and with use of the flow electrolyte cell 10 as the chromatography cell to make the output recording of only the potentiostat 9.
The sample injector 7, the potentiostat 8 and the electromagnetic valve 55 are linked to the programcontroller 54, which performs the following functions; supplying alternately with the supporting electrolyte. a
constant amount of the sample at constant intervals to the flow pipe 2; successive switching of the electrolyte potential of the potentiostat 8 by the automatic potential switch circuit 57 provided in this controller 54, when the flow electrolyte cell 10 is worked as the chromatography cell; and operating the electromagnetic valve 55 for switching the nitrogen gas.
The constitution of said program-controller 54, which should be selected to suit the intended application of the inventive device will be described by the following description wherein the invention is applied to specific cases:
EXAMPLE 1 In this example, a sample is to be analyzed and the results recorded on a continuous and simultaneous basis, for concentrations of copper and lead.
In this case the program-controller 54 in the device is not used. As a result, electromagnetic valve 55 is in active, thus the nitrogen gas is continuously and exclusively forced into the supporting electrolyte reservoir 1 and the sample reservoir 29.
The potentiostat 5 sets a particular potential such that only the supporting electrolyte flows into the filter cell 6 and no impurities go into the path of the flow pipe 2 downstream of the filter cell 6. Thus, the supporting electrolyte is purified. The potentiostat 8 sets such a potential of the flow electrolyte cell 10 that electrolytic deposition of copper alone takes place continu ously in the flow electrolyte cell 10. The potentiostat 9 sets such a potential of the flow electrolyte cell 11 that satisfactory electrolytic deposition of lead takes place continuously in the flow electrolyte cell 11.
The potentiostat 33 sets such a potential of the flow electrolyte cell 34 that only copper and lead can flow out of said cell; thus the sample is purified with no other substances than copper and lead allowed to go into the sample-supply pipe 32 in the path downstream of the flow electrolyte cell 34.
Thereafter. when the sample is allowed to flow into the supporting electrolyte flow pipe 2 by manually operating the electromagnetic valve 46 of the sample injector 7, both the flow electrolyte cells 10, 11 act together as a detector cell, with the result that the sample concentration. ie, the temporal changes of copper and lead concentrations, as illustrated in FIG. 9, are simultaneously and continuously registered by the two-pen recorder 56.
EXAMPLE 2 This example illustrates application of the invention when a sample is discontinuously analyzed for its copper and lead content and the results recorded.
In this case the program-controller 54 in the device is used, its constitution being illustrated in FIG. 11. A cam 62 is integrally formed on the circumference ofeither of the two disks 60, 61 in this case, say, 60. Both disks are fixed to a shaft 59 of a synchronous motor 58 rotating continuously at uniform speed. The circuit of a microswitch 63 is switched ON" at constant intervals, thereby sending an electrical signal to the solenoid coil 39 of the sample injector 7, and thus the sample supply disk 38 is intermittently rotated by 60. Intermittently, a defined amount of the sample enters through hole 44 of the sample-supply disk 38 by virtue of this intermittent rotation and is carried by the supporting electrolyte in the flow pipe 2 connected to the sample injector 7. Together with the supporting electrolyte, the sample intermittently enters the orifice 42 of the disk 37 and the three-way tube 47 into the flow electrolyte cell 10.
Meanwhile a cam 65 on disk 61 turns the circuit of the mircoswitch 64 to ON" at the same time as the circuit of microswitch 63 is being turned ON by the other disk 60. These cams have the effect of holding said microswitch 64, as well as microswitch 63 ON" for a certain duration, and then turning them OFF. Said microswitch 64 continues sending an electric signal to the electromagnetic valve 55 while its circuit is held ON, during which time the nitrogen gas is forced from the nitrogen gas supply pipe 45 into the through-hole 44 of the sample-supply disk 38, thereby cleaning the through-hole 44 of the residual samples or supporting electrolyte.
The potentiostats 5, 8, 9, 33, setting the same potentials, perform the same functions, as in Example 1. In the operation and device thus described, when the circuit of the synchronous motor 58 is switched to ON" both the flow electrolyte cells I0, 11 act as the detector cell, one of them, i.e., cell 10 electrolytically depositing copper and the other, electrolytically depositing lead. Thus, the variations of copper and lead concentrations at constant intervals as illustrated in FIG. 10 can be simultaneously and continuously registered by the twopen recorder.
EXAMPLE 3 In this example, trace concentrations of copper, lead and cadmium in a sample are first condensed in a first cell and then their respective concentrations detected by means of a second cell and recorded.
in this case the program-controller 54 in the invention is used; its constitution and the constitution of the potentiostat 8 are illustrated in FIGS. 3, l3 and 14. To describe the operation, shaft 67 of the synchronous motor 66 running continuously at uniform speed is coupled to a condensing disk 68, a first electrolytic deposition disk 69, a second electrolytic deposition disk 70 and a third electrolytic deposition disk 71. Upon the circumferences of these disks are integrally formed cams 72 to 75, inclusive, which turn corresponding microswitches 76 to to ON or OFF."
Immediately after the first cam 72 sets the microswitches 76 and 77 to OFF," the next cam 73 sets the next microswitch 78 ON." Immediately after the microswitch 78 is turned OFF" the next cam 74 sets the microswitch 79 to ON. Thus, the microswitches are successively set ON and OFF, but so arranged, however such that no microswitches other than 76 and 77 are set to *ON" simultaneously.
The microswitch 76 is linked to the electromagnetic valve 46 of the sample injector 7; while the electromagnetic valve 46 is receiving an ON"-signal, the sample continues to be carried together with the supporting electrolyte via the flow pipe 2 into the flow electrolyte cell 10.
No electric signal is sent to the solenoid coil 39. The potentionstat 8 has an automatic potential switch cir cuit 57, as illustrated in FIG. 3 and 14 built therein, such that it gives a plus potential to lead terminal column WE2 of the flow electrolyte cell 10 and a minus potential to the lead terminal column WEI, thereby causing a potential gradient in the working electrode 13.
The switching action of the automatic potential switch circuit 57 takes place automatically as the result of the microswitch 77 to 80 being set ON" or OFF" by the disks 68 to 71 which are rotated by the synchronous motor 66.
In FIG. 3 symbol 8] represents a variable directed current source; the right side of the Figure illustrates the working principle of chromatography. In this diagram of the working principle the bottom-most symbols 1, 2, 3, 4 denote the switching order to potential and potential gradient, the arrow in the transverse direction showing the switching direction. The voltage values given up and down respectively indicate the potential changes in the lead terminal column WEI and WEZ.
When, for instance, a sample containing copper, lead and cadmium is analyzed using the potentiostat 8 and the inventive device thus programmed, the synchronous motor 66 is turned ON after the flow electrolytc cell 34 has been given by the potentiostat 33 a potential which permits sample to flow out containing only the three elements copper, lead and cadmium. Thereupon, first the microswitches 76 and 77 go ON, causing the sample to be supplied to the working elec trode 13 of the flow electrolyte cell 10, while at the same time the potentiostat 8 creates in the working electrode 13 the first potential gradient which causes electrolytic deposition of each element. Thus all the el ements are successively electrolytic-deposited with condensation; copper in the vicinity of the lead terminal column WE2, lead at the center, and cadmium in the vicinity of the lead terminal column WEI.
When the next microswitch 78 goes ON and the potentiostat 8 creates in the working electrode the second potential gradient which causes dissolution of cadmium, cadmium is dissolved and carried out of the flow electrolyte cell I0, while lead migrates to the proximity of the lead terminal column WEI and gets electrolytically deposited and copper does so near the lead terminal column WEZ.
When next the microswitch 79 goes ON and the potentiostat 8 creates in the working electrode 13 the third potential gradient which causes dissolution of lead, lead is dissolved and carried out of the flow electrolyte cell It), while copper, migrating to the proximity of the lead terminal column WE], gets electrolytically deposited there.
When further the microswitch 80 goes ON and the potentiostat 8 creates in the working electrode 13 the fourth potential gradient which cause dissolution of copper, copper too is dissolved and carried out of the flow electrolyte cell 10.
Therefore, by using the suceeding flow electrolyte cell II as the detector cell and giving thereto a potential for detection of copper, i.e,, the last element to be detected, by the potentiostat 9, the quantities of electricity corresponding to the condensed amounts of cadmium, lead and copper as illustrated in FIG. I2 can be registered by the recorder 56 and thus the concentrations of the three elements in the sample can be found from the registered quantities of electricity and the flow rate of the sample.
EXAMPLE 4 This example illustrates intermittent analysis of a sample containing many elements wherein there is little difference in the respective electrolytic potential of said elements to accomplish complete separation of these elements and recording their concentrations.
In this case too, the program-controller 54 in the same device is used; its constitution and the constitution of the potentiostat 8 are respectively shown in FIG. 6 and 11.
The units other than the potentiostat 8 are the same as those employed in Example 2 and perform the same functions,
The d-c power supply circuit 82 in the potentiostat 8 is connected to an ac superimposing circuit 83. Thus, the tin and lead dissolving potential, as superimposed with ac, can be applied to the working electrode 13. In FIG. 6, 84 is an ac voltage generator, 85 is a signal control, and 86 is a control amplifier.
When for instance, the supporting electrolyte is hydrochloric acid solution and, using the potentiostat 8 and the device thus programmed, tin and lead contained in the sample can be separately detected. First, a potential at which only the two elements, i.e., tin and lead in the sample can flow out is given by the potentiostat 33 to the flow electrolyte cell 34. Then, the detec tion potential for lead, which is dissolved later, is given by the potentiostat 9 to the flow electrolyte cell 11. Thereafter, the circuit of the synchronous motor 58 is switched ON," thereupon, the microswitch 63 goes ON, causing the sample to be supplied to the working electrode 13 of the flow electrolyte cell 10; at the same time the working electrode l3 receives the tin and lead dissolving potential as superimposed with a-c. Thus the two elements, i.e., tin and lead, while repeating deposition and dissolution within the working electrode 13, gradually flow out of the flow electrolyte cell 10. Since there is a difference between tin and lead in the velocity of deposition and dissolution, that is, in the electrode reaction velocity, at first tin flows out of the flow electrolyte cell 10 and then lead does so. As the succeeding flow electrolyte cell 11 is employed as the detector, the concentrations of these elements can be registered by the recorder 56 in a completely separated condition as illustrated in FIGv 5, though the waveforms of these elements may be overlapped as shown in FIG. 4 when a'c is not superimposed.
Meanwhile, the nitrogen gas cleans the through-hole 44 of the sample-supply disk 38 in the sample injector 7 which has been circulated with the supporting electrolyte.
In this example, no electric signal is given to the electromagnetic switch valve 46 of the sample injector 7. But when the contents of tin and lead in the sample are mere traces and their concentrations can not be detected by the flow electrolyte cell 11 unless they are condensed, the amount sampled by the sample supply disk 38 of the sample injector 7 is found insufficient. In that case, for the purpose of supplying a sufficient amount of the sample to the flow electrolyte cell It], the cam 62 of the disk 60 in the program-controller 54 is desired such as to be able to keep pushing the microswitch 63 for a definite time; and the microswitch 63 is connected to the electromagnetic valve 46 of the sample injector 7.
Further, the working electrode 13 of the flow electrolyte cell 10 is first given such a potential that the two elements can be condensed and accumulated at the working electrode 13. Then the potential is switched by Moreover, quantitative analysis using the present invention is free from the effect of temperature. Being proportional to and dependent upon only the quantity of electricity applied, it is highly accurate and easy to the potentiostat 8 to an a-c superimposed potential at perate. which the two elements can be dissolved. In the device according to the present invention,
A specific construction or embodiment of the device wherein operation of a flow electrolyte cell as a filter according to the present invention and examples of ap' cell proceeds the sample injector in the flow path of the plying this device are described above. Table 2, below, supporting electrolyte, the highly desirable result of pugives the results of analysis, the accuracy of measurerifying the supporting electrolyte is obtained. Since ment, and the time required to accomplish analysis. traces of impurities like heavy metals which cannot TABLE 2 Type of Ions Items Copper Lead Cadmium Sensitivity l X ltl'" mol l X l0 mol l X 10 mol Accuracy I00: 3% 100: 2% 100i 3% Sampled amount [micro syringe) lt] ptl ltlpl ltlul Measuring time less than less than less than (measured by detector) 60 sec. 60 sec. 60 see.
In this case, analysis was made using O.lM- CH COOH and lM-KCI as the supporting electrolyte, lM-KC] as the depolarizing electrolyte, saturated KCl and saturated AgCl as the reference electrode solution, Ag/AgCl as the reference electrode, and taking 10 [.Li each ofthe sample containing singly copper, lead or cadmium. Where analysis was made of samples with contents of only one of these elements, only one flow electrolyte cell 10 was employed following the sample injector 7. When samples containing a plurality of elements were analyzed, as many flow electrolyte cells as the elements contained were employed and even when there was not difference in the accuracy of analysis, the only difference being that the time taken for measure ment increased as much as the number of elements involved.
in terms of sensitivity, the invented device may be said to be on the same level of capacility as atomic absorptiometry, but when it comes to the measuring range it has an outstanding feature of being able to measure over a wide range from less than PPb to percent under the same conditions. Therefore, if this de vice is utilized for analysis of industrial effluent, data can be collected regardless of whether the plant is operating in full capacity, operating at limited capacity or not operating, with significant variations of effluent concentration. because the device has a wide measuring range,
Moreover. since its whole structure consists of electronic circuits and a simple flow system, the invention is characterized by a remarkable feature in that it is highly reliable and safe as for example, a process instrument for work-step analysis or water-quality inspection device for field use, which demands long periods of op erations and its ability to condense a sample of trace concentration to such an extent that it can be detected.
conventionally be eliminated even with use of a special grade reagent can be electrolytically collected and removed out of the supporting electrolyte, a much less expensive reagent can serve as the supporting electro lyte, thus eliminating the need for and extra cost of special-grade reagents.
There is an additonal advantage from the fact that the sample-supply flow path includes a flow electrolyte call as a purification unit, in that the irrelevant substances in the sample can be eliminated and only those relevant to the effluent control or process control can be analyzed and measured.
Additonally, the invention is unique and advantageous in that, with a programcontroller linked to the sample injector, or to the sample injector and the potentiostat for a flow electrolyte cell on the supporting electrolyte-discharing side of the injector, this flow electrolyte cell combination may be utilized as the chromatography cell, or as the detector cell, resulting in a number of industrial advantages such as laborsaving through automation of device, more accurate and easy detection and analysis of trace quantities of substances in the sample to be analysed.
In addition to the above-described embodiments, the invention includes other configurations, arrangements and applications, such as for example, wherein: (l) following the sample injector, flow electrolyte cells are arranged in parallel, and solutions are charged at a definite proportion to find the concentration of the refer ence solution by one flow electrolyte cell and the concentration of references solution containing an element to be detected, by another flow electrolyte cell; thus, by measuring electrically the difference between the two results, the concentration or concentration change of the element can be found from the quantity of electricity thus measured; or, (2) following the sample injector, a number of flow electrolyte cells may be arranged for fractional collection and adjustment of a sample; thus the invention can be utilized as a means of bringing substances of different oxidized degrees to a single oxidized degree. In connection therewith, if the flow electrolyte cell serving for adjustment is followed by some appropriate fraction collector, a system for automatic adjustment, separation and condensation can be constituted. Further, (3), the invention may be applied as means of adjusting the concentration of an unstable compound like bromine water or as means of generating an organic radical, which generates monoanion radical through electrolytic reduction of anthraquinone. Thus the device of the present invention has the merit and advantage of being versatile in application and structure.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
1. A detector system for detecting impurities in water, said system comprising:
a supply means for supplying supporting electrolyte;
b. first flow electrolyte cell means coupled to said supply means for purifying said supporting electrolyte, said first cell means including a casing and a potentiostat means;
c sample injector means including a sample reservoir coupled to said first cell means for injecting a sample containing said impurities into said system;
d at least two additional flow electrolyte cell means, including a second cell means coupled to said sample injector means and a third cell means coupled to said second cell means, said second and third cell means each including a casing and potentiostat means;
e depolarizer electrolyte supply means coupled to said casing of each of said cell means, wherein each said casing includes an auxiliary electrode and the depolarizer electrolyte flows through said casing to contact said auxiliary electrode; and,
f recorder means coupled to the potentiostats of said at least two additonal cell means for recording the output thereof, the output of said potentiostats being indicative of the amount of said impurities in said sample.
2. The detector of claim 1, further including a programcontroller means coupled to said sample injector means and the potentiostat of said second cell means for controlling the flow through said sample injector means and for controlling the potential of said potentiostat.
3. The detector of claim 2, wherein the potentiostat ofsaid second cell includes an automatic switch circuit, said program controller means being coupled thereto and controlling said switch circuit.
4. The detector of claim 3, wherein said switch circuit includes a variable resistor having a slidable tap.
5. The detector of claim 3, wherein said switch circuit includes a variable resistor having a plurality of predetermined resistances.
6. The detector of claim 2 wherein said program con troller means includes a plurality of cam operated switches and a motor means for driving said cam.
7. The detector of claim I, wherein said sample injector means includes a flow electrolyte purification cell having a potentiostat for removing impurities other than said impurities which are detected from said sample.
8. The detector of claim 1, wherein the potentiostat of said second cell is connected to an a-c superimposing circuit means.
9. The detector of claim I, wherein the supply means and said sample reservoir are connected to a nitrogen gas-supply means for dispelling dissolved oxygen therein; and the sample injector means is connected to said nitrogen gas-supply means for forcing out any residual sample solutions and electrolyte thereinv 10. The detector of claim I, wherein said sample injector means injects the sample into the flow of supporting electrolyte.
11. The detector of claim 10, wherein said sample is continuously injected into the flow of said supporting electrolyte.
12. The detector of claim 10 wherein said sample is discontinuously injected into the flow of said supporting electrolyte.
13. The detector of claim 1, wherein said injector means comprises first, second, and third disks, said sec- 0nd disk being positioned between said first and third disks and rotatable with respect thereto wherein each disk has a plurality of aligned holes therein such that a sample is injected from said sample supply means into a hole in said second disk and when said second disk is rotated a predetermined amount of said sample is ejected from said hole into said supporting electrolyte. i i l