Review of Fundamental Developments in Analysis
Polarographic Theory, Instrumentation, and Methodology David N. Hurne Massachusetts lnstitute o f Technology, Cambridge, Mass.
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HIS REVIEW, the fifth in the series, follows the general approach of its immediat'e predecessor (70). The literature appearing between mid-1957 and mid-to-late 1959 is surveyed. The most striking event in this period is undoubtedly the award of the Nobel Prize in Chemistry for 1959 to Professor Jaroslav Heyrovskf, the founder of polarography (36). The award is a tribute not only to the achievements of Professor Heyrovsk?, but to the importance of the polarographic method today. The ever-growing literature of polarography shows no sign of slackening its pace, and the annual supplements t o the comprehensive bibliographies founded originally by Heyrovskf and Semerano attest this fact every year (69, 174). The latter bibliography, now compiled by B. Tosini, has had its usefulness enormously increased by the addition of a subject index. NcKenzie (226) has given a general review of polarographic methods, and iMilner and Slee (196) have discussed recent developments. The book edited by Semerano (161) contains a great many worth-while papers and, in addition, an extensive summary of the polarographic characteristics of organic compounds. For a n account of some of the newest methods and developments, many still unpublished, the report on the informal discussion on electroanalytical chemistry which took place at the Boston meeting of the American Chemical Society in April 1959 should be consulted (156).
CLASSICAL POLAROGRAPHY
Instruments a n d Apparatus. T h e prospective purchaser of automatic polarographic apparatus now has a wide choice of instruments to consider. I n t h e United States, t h e E. H. Sargent Co., Chicago, Ill., has added t o its line t h e Model XV, which is comparable in many respects t o t h e familiar XXI b u t is simplified a n d much more compact. T h e Fisher Scientific Co., Pittsburgh, Pa., offers a new model Elecdropode in t h e form of a self-contained unit which, in con-
junction n ith a standard recording potentiometer, serves as a complete automatic polarograph. The Patwin Recording Electro-Polarizer is now marketed by the American Optical Co. Among foreign manufacturers, Radiometer of Copenhagen now calls its polarographs Polariters and besides the familiar PO-3 offers a PO-4 with a 10inch recorder and a built-in accessory circuit which permits the recording of derivative polarograms a t the flick of a switch. Netrohm in Herisau, Switzerland, likewise has a pen-recording polarograph with a built-in derivative circuit. B. Lange of Berlin has an instrument on the market, and the Leybold polarograph is now manufactured and marketed by Atlas-Werke of Bremen. An oscilloscopic polarograph, the Polarotrace, is n o x manufactured by Southern Instruments in England and is distributed in the United States by Standard Scientific Supply Corp., ?;. Y. Based on the single sweep principle of Randles, the instrument performs a current-voltage scan during the last 2 seconds of a 7-second drop life, presenting the result on a high-persistence oscilloscope screen. Both direct and derivative polarogIams may be obtained with this instrument. One of the drawbacks to conventional recording po1arogr:tphs has always been that these instruments recorded currentvoltage rather than current-potential curves. A number of authors have applied themselves to remedying this situation, and Oka (149) has described an automatic correction servomechanism which compensates for the iR drop in the cell system. Kern (89) has further developed Oka's idea and included a correction for the nonlinearity of slidewire voltage which may develop when the currents drawn are appreciable. Peiaker (146, 147) has also given circuits for automatic compensation for iR drop. Pecsok and Jensen (159) have approached the problem in a rlightly different manner by devising a polarograph with an X-Y recorder which measures and records both potential and current simultaneously and continuously. Good results are obtained even in non-
aqueous solutions with resistances as high as 22,000 ohms. Kelley, Jones, and Fisher (87) use a n operational amplifier to control continuously the potential of the dropping electrode with respect to the reference electrode, forcing it to equal the linearly increasing control voltage. Perfectly normal polarograms were obtained with resistances as high as 20 megohms present. The instrument described is also applicable to derivative polarography. Bard (7) has described a remarkably versatile electroanalytical instrument incorporating an X-Y recorder. This multipurpose device can be used for voltammetry (both voltage and current scan polarography), chronopotentiometry, constant current coulometric titration, potentiostatic coulometry, and the recording of titration curves. Licht, Curran, and de Bethune (112) describe a simple circuit for an adapter to convert a traditional photographicrecording polarograph to use R ith a penink potentiometer recorder. Whitnack, Olsen, and Johnson (65) have developed a dual recording system nhich permits auxiliary polarograms to be recorded on 8 l / 2 X 11 inch paper, providing booksize records for filing. Developments in recording polarography have been described in a brief review (2 66). An electronic falling drop timing circuit designed for falling drop densimetry could very well be useful n i t h the dropping mercury electrode (54). Several authors have been concerned with the recording of instantaneous currents from individual drops and McKenzie and Taylor (229) give techniques for converting ordinary pen polarographs for this purpose. Berg and Horn (19) describe the use of a very short period galvanometer, and Sewcomb and Boardman (140) demonstrate the use of an oscilloscope for this purpose. Cells a n d Electrodes. T h e design of cells continues t o stimulate t h e ingenuity a n d several new versions have been described (48, 50,137). Microcells allowing polarography on volumes as small as 0.05 ml. have been proposed by several authors (17, 164) and a thermostated cell for use with the VOL. 32, NO. 5, APRIL 1960
137 R
streaming mercury electrode has been described (18). Perhaps the most interesting cell is one developed for the bloodless determination of arterial oxygen, which is achieved by equilibrating the patient’s finger \vith the supporting electrolyte in a cell specifically designed for t’his purpose (157). The desire to monitor ion exchange effluents polarographically has resu1t)ed in the design of several cells suitable €or use with flowing streanis (%?, 118, 163, 179). A cell and apparatus for automatic: sampling and analysis of radioactive streams were described recently (4). A somewhat similar system involving a proportioning pump for automatic sampling of process streanis has also been proposed (21). Koyania and 1Iichelson ( I O f ) have studied the efficiency of removal of dissolved oxygen as a function of the type of bubbler used. Proper design of the fritted glass bubbler permits it t o remove as much oxygen in 1 minute as n-ould be achieved with a simple capillary bubbler in 45 minutes. The findings are worthy of note by anyone designing polarographic equipment. hIeites and Moros (135) have described a low resistance silver-silver chloride reference electrode for pojarographic work, and other workers (31) have suggested the use of a zinc rod in a pH5.5. buffer for the same purpose. Karchmer (84) has studied rapidly dropping mercury, electrodes for practical analysis. A liorizontal placement of the dropping electrode affects the drop time 1,- a factor of approximately 0.21: and vertical electrodes with scratched or abraded orifices likewise drop much more rapidly than normal electrodes. The currents obtained ?&re muc!>. smaller than those predicted by the I l ‘ k w i t equation, but the rapidly dropping electrode is muell less SURceptible to diPturbance by movement of tlie solutioli tlixi i.q n conventinrial eieiwdi:. The horizoctai dropping plc.ctrode is prob:ibly tlie mo7t useful f(3rci (176jand h:is beeri applied t o the dctericinatior; of 0s:;ger (IC5). It noted t h a t tile Taler r ~ : ~ vofe Orit.iriariri : ~ i i , i K~~lthoff
sewage. Again, these electrodes are iess susceptible to disturbance from motion of the solution and they are said to remain operative longer than ordinary dropping electrodes used in the same media. THEORY
Half-Wave Potentials. 1Ic1Iasters and Schaap (131) have applied an I B l I 650 computer to the high speed calculation by least squares of the best half-wave potential and slope from points on a polarographic wave. Explicit directions are given for setting up the program, and it is claimed that results are obtained n-ith an expenditure of no more than 1 minutes per polarogram. Sewman, Cabral, and Hume ( 2 4 2 ) have pointet! out the usefulness of the concentration-independent potential, E,, of mercury waves in place of the concentration-dependent El 2 . iYyman and Parry (149) have applied the DeFord-Hume ( 4 1 ) method for the polarographic determination of consecutive complex formation cnnstants to anodic Lvaves of mercury in thiourea. 3IcJIasters and Schaap (130) have adapted high speed computer prograniming to least-squares estimation of formation constants of complexes by the DeFord-Hunie method. K i d o and his con-orkers (91, 152) have also developed least-squares treatments of the DeFord-.Hunie method. Tanaka and Kato (270) have studied weak cornples formation ivith the aid of an ausiliary complex-forming ligand. KnryP::’ (99) has gi\-en the n~iutlicmatical I of a metliocl of determining con constants from tlie half-n.ave putex7 tia! of kineticall>- controlled n ayes. Mechanisms of Electrode Reactions. -1 g x a t deal of iiitcrest kiilti art>ivity h a s ccntcred on stiidics of d c t ail e:l i i i w ha 11is m s oi cle c t r c t i j?. i *
given of these potentiostatic and galvanostatic methods. JIasuda, Oka, and Delahay (126) studied rapid electrode reactions by a double-pulse galvanostatic method derived from Gerischer, and Bauer and Elving determined transfer coefficients by a n alternating current method ( 1 6 ) . Grahame (62) has given a detailed account of the development of precise techniqurs for the measurement of the impedance of the electrical double layer and hon these have been used to study the drtails of reversible electrochemical reactions. By the use of an impedance bridge: the impedance of the mercurysolution interface a t the dropping electrode may be measured and the ccpacity and resistance of the interface. 1%-hich are vector components of the impedance, may be determined separately. The analytical applications of this technique paralle! those of alternating current polarography and tensamnietry, which measure the over-all impedance, a scalar quantity. The present technique can, however, in special cases throw light on the reactions themselves. The results have bearing on Lyons’ theory (f16)that the rate of reduction of metal cations a t electrode interfaces depends on the electronic configuration of solvated or complex ions just prior to reduction. Results by the impedance method indicate that isoelectronic ions do not necessarily react at the same rate (63). 3Iarcus (119) has developed a theory of thlrctron transfer processes which
tnkw into account the effect of the double laJ-er ori electrode reactions. and brings out the parallelism of solution .ode reactions. Reiriniuth, d HumnielI:trp, R. D., Shain, I.. J . Am. (931 Kolthoff, I. M., Okinaka, Y., Ibid., C h o u . Soc. 81, 2654 111959). (48) I k ~ u s r ~ kF.. P., Kalous, V., Radi18, 83 (19%). (94) Kolthoff, I. PIT., Okinaka, Y . , J . onirler Polarographics 4, 45 (1957). Am. Chem. SOC.80, 4452 (1958). (49) EIi:i*, 1'. F., Leyboid polarograph. Ber. (95 I Ibzd., 81, 2296 (1959). 5. 123 I 1937). ( 9 6,1 Kolthoff. I. 31.. Okinaka. Y.. FuiiIi., AriAL. nlga,~T., Anal. &him. Acta 18, 2$5 (25) Breiter, M., Delahay, P., Ibid., 81, 2938 (1959). (26) Breiter. M.. Kleinerman. XI..' Delahay, P., Zbid., 80, 5111 (1958). (27) Bresle, %..,Sci. Tools 3, 9 (1956). (28) Ibid.. 4., 33 (1957). . (29) Breykr, B., Rev;. Pure and Appl. Chem. (Australia) 6 , 249 (1956). (30) Briggs, R., Davies, F. S., Dyke, G. IT., Knowles. G.. Chem. & Znd. (London) 1957, 223. ' (31) Briggs, R., Dyke, G. V., Knowles, G., Analyst 83, 304 (1958). (32) Cahan, B. D., Ruetschi, P., J . Electrochem. SOC.106, 543 (1959). (33) Cakeberghe, J. van, Bull. SOC. chim. Belge 60, 3 (1951). (34) Carritt, D. E., Kanwisher, J. W., ~ ~ N A CHEM. L . 31, 5 (1959). (35) CermBk, V., Collection Czechoslov. Chem. Communs. 24, 831 (1959). (36) C'hein. Eng. News 37, 105 (Xov. 9, ~
.
\ - - - - , -
~~
~
\~
.,
J . Phys. Collection
24, 3046
(1958). (97 I Kolthoff, Samhucetti, C. J., J . ilm. Chem, SOC.81, 1516 (1959). (98'1 Koryta, J . , Collection Czechos!oi'. Chem. C o v ~ m u n s .23. 1408 11958).
(54) Fishrr, D. J.) .?SAL. CHEM. 30, 30s ' 1!)68). 155) F'rumkin, A. S . . .Yam d d n Leo-
(115) Lyons, E. H., J . Electrochem. SOC. 101, 363, 376 (1954). (116) Macero, D. J., Rulfs, C. L., J . ilm. Chem. SOC.81, 2944 (1959). (117) Mackfi, J., Chem. listy 52, 980 (1958). (118) Mann. C. K.. ANAL. CBEM. 29. ' 1385 (1957). (119) Marcus, R. A., Can. J . Chem. 37, 155 (1959). (120) hfarkowitz, J. M., Elving, P. J., J . Am. Chem. SOC.81, 3518 (1959). (121) Markowitz, J. M., Elving, P. J., Chem. Rev. 58, 1047 (1958). (122) Martin, K. J., Shnin, I , -4NAL. CHEM.30, 1808 (1958). (123) MaBhiko, Y., Hosoya, S . , Akimoto, M., Bunseki Kagaku 7, 702 (1958). (124) Masuda, H., Bull. Chem. SOC. Japan 26, 342 (1953). (125) Masuda, H., Oka, S., Delahay, P., J . Am. Chem. Soc. 81, 5077 (1959). (126) McKenzie, H. A . , Revs. I ' w e and Appl. Chem. (Australza) 9, 53 (1958) (127) McKenzie. H. A , . Australian J . ' Chkn. 11, 383'(1958). ' (128) Ibid., p. 271. (129) McKenzie, H. A., Taylor, 11. C., Zbid., 11, 260 (1958). (130) Mchlasters, D. L., Schaap, W.B., Proc.Zndiana Acad. Sci. 67. 111 (1958). (131) Zhid., p. 117. (132) hlcMullen, J. J., Hackermann, S., J . Electrochem. SOC.106, 341 (1959). (133) hleites, L., Moros, S. A . , AsAL. CHEV.31, 23 (1959). (134) hIicka, K., Collection C.:echosh. Chem. Communs. 24, 678 (1959). (135) Milner, G. W.C., J . Polurog. SOC. 1, 2 (1958). (136) Milner, G. W. C., Slee, L. J., Ind. Chemisi 33. 494 (1957).
(195S!.
(140) Sewcomhe, R. J., Boardnian, [V., Chem. & Znd. (London) 1955, 1173.
(141) Sewman, L., Cahral, J. De O., Hume, D. N.,J . ilm. Chein. SOC. 80, 1814 (1959). (142) Syman, C. J., Parry, E. I'.! ASAL. CHEM.30, 1255 (1959). (143) Oka, S.,Zbid., 30, 1635 (1958'. (144) Orlemann, E. F.; Iiolthoff, I. >I., J . .4na. Chem. Soc. 64,833 (1942) (1451 Paldus, J., Kouteck$, J . , (~'oliection C'eechoslor. Chem. ("uvzrrtuns. 23, 376
( 1 U h ; Laitiiieri. €1. A.: i i u , C. Ii., FerguFClii, IT. C., . i r ; ~ ~ CHEM. ~. 33; 1266
(1935;. i 109) Laitinen. E.
350 (1VSUl. (68) Heyrovsk?, J.. Chem. Tech. (Rerlin: 9, 2.57 (1957).
(69) €ieyrovsk$. J., Collection C'zechslov. Cheni. Commu,ns. 22, Supp. I (1957); 23,Supp. 1 (1958).
!I..
Subcask?., K. J.,
i-4m.Chrrn. Soc. 80, 2623 !l958!. ( i l L 1 ) Lamhert. F'. L.. ASAL. CLIEM.30. If118 (1958 ( 1 11 Lee, J. K., Atiams. R. S . , Brrcker, C E.. Anal Chzm Acta 17. 321 i1957i. i 1 K ) Licht T S., Curran. D. J., dt, Bethune. A . eJ., ~ X A L CHEW 30,
1>18S(1958)
( l i 5 1 Losew, W. W., Doklcrdy Akad. h auk S.S.S.R. 107.432 (1956) (114 j Love, D. L., Anal. 'Chim'.Acta 18, 72 (1958).
56) Reinmuth, W. E., Roger;.. 1,. 13., Humnielstedt, id E. I,. J . .4n.C'hem. Soc. 81. 2941 :!95G 57) Rooth, G., Sjostcdt 5 , Lniigare, F., Scz. Tools 4, 37 (1957, 581 Sawyer, 1). T., Leorge. R. S., Rhodes, K. C., A 4 ~ ~ Ctimf. 4 ~ . 31,
2 (1959).
VOL 32, NO. 5 , APRil 1960
143 k
(159) Sawyer, D. T., Pecsok, R. L., Jensen, K. K., Ibid., 30, 481 (1958). (160) Schmid, R. W., Reilley, C. N., J. Am. Chem. SOC.80, 2087 (1958). (161) Semerano, G. “Contributi F o r i c i e SperimentaB di Polarogafia, Vol. 111, Consiglio Nazionale delle Recherche, Rome, 1957. (162) Silverman, L., Bradshaw, W. G., ANAL. CHEM.31, 1672 (1959). (163) Stromberg, A. G., Pyshkina, A. A.,
Trudj Komissii Anal. Khim. Akad. Nauk S.S.S.R. 7, 136 (1956). (164) von Sturm, F., J. Polurog. SOC. 1958. ~ . . 28. .
(165)
Sturm, F., Z. anal. Chem. 166,
100 (1959).
(166) Takahashi, T., Siki, E., Tala& 1, 177 (1958). (167) Ibid.. D. 245. (168) Takjh’ashi, T., Shirai, H., Xiki, E., Rept. Inst. Id.Sn’. Univ. Tokyo 8, 123 (1959).
(169) Tamamushi, R., Yamamoto, S., Takahashi, A., Tanaka, N., Anal. Chim. Acta 20, 486 (1959). (170) Tanaka, Tu’., Kato, J., Bull. Chem. SOC.Japan 32, 516 (1959). (171) Tanaka, N., Kodama, M., Nippon Kagaku Zmshi 79,410 (1958). (172) Tanaka, N., Koizumi, T., hfurayama, T., Kodama, M., Sakuma, Y., Anal. Chim.Acta 18, 97 (1958). (173) Tanaka, Tu’., Tamamushi, R., Kodama. hf., Zbid.. 20. 573 (1959). (174) Tosihi, B., Riiera’sci. 28, Supp. A (1958); 29, Supp. A (1959). (175) Tribalat, S., Delafosse, D., Anal. Chim. Acta 19, 74 (1958). (176) Tyler. C. P.. Karchmer.’ J. H.. . ANAL:CHEM.31, 499 (1959). (177) VKek, A. A,, Trans. Faraday SOC. 5 5 , 164 (1959). (178) VlCek, A. A., Collection Czechoslov. Chem. Communs. 24, 181 (1959).
(179) Vodehnal, J., Marhol, IT., Ibid., 24, 1281 (1959). (180) Vojii, V., Chem. listy 52, 335 (1958). (181) Voorhies, J. D., hdams, R. N., ANAL.CHEM.30, 346 (1958). (182) Voorhies, J. D., Furmsn, ?;. H., Ibid., 30, 1656 (1958). (183) Zbid., 31, 381 (1959). (184) Voorhies, J. D., Parsons, J. S., Zbid., 31, 516 (1959). (185) Keaver, R. D., Whitnack, G. C., Anal. Chim. Acta 18, 51 (1958). (186) Weber, J., Colleclzon Czechoslov. Chem. Communs. 24, 1770,3041 (1959). (187) Willeboordse, F., “Polarography in Some Non-Aqueous Solvents,” ZJniversity of Amsterdam, 1950. (188) Yasumori, Y., J . Electrochem. SOC. Japan 24, 309 (195$). (189) Zhvorka, J., Strhfelda, F., Chem. listy 51, 2371 (19.57).
Review of Fundamental Developments in Analysis
Organic Polarography Stanley Wawzonek Sfafe Universify o f lowa, lqwa Cify, lowa
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covers articles which have appeared in Chemical Abstracts and readily available journals during the two-year period ending November 1, 1959. As in the past, duplication and reinvestigations of previous work appear. I n this review special attention is called to such papers only if disagreement in results occurs. This period has seen the aJTarding of the Nobel Prize in chemistry to Jaroslav Heyrovsk? for his work in polarography, and he is to be congratulated on this honor. Noteworthy developments in this period which have helped to expand the field are the work on the oxidation of organic compounds in nonaqueous solvents, the reduction of activated hydroxyl groups, the reduction of carbon black suspensions, and the greater use of chronopotentiometry. Three books (60, 564, 611) dealing with topics in this field have been published. Numerous reviews have appeared on the applications of polarography t o organic systems (190), nonaqueous systems (196), organic chemistry (608), pharmacology (261), and blood chemistry (686). Other articles have covered the determination of organic substances in the atmosphere (183), blood components (68S-685), agricultural pesticides (279), alkaloids (641), organic drugs (252), and essential oils (627). Specialized reviews cover kinetic currents (6721, kinetics of electrode HIS REVIEW
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ANALYTICAL CHEMISTRY
processes (334, 59S), carbonyl compounds (442, 449), studies of important biochemical reactions (697), steric effects in polarography (699), effects of strudture on polarographic behavior (SSS), isolation techniques used prior t o analysis (414), oscillographic I-E curves (64.27, applications of oscillopolarography in pharmaceutical analysis (265), the effects of sui.ients and p H upon the behavior of various compounds (565), and oscillopolarography with alternating current (206). Studies on the use of anhldrous solvents have continued. Data are reported on the behavior of hydrogen chloride in acetone (116) and ether (116), and of tetraalkylammonium salts in acetic acid, acetic anhydride (195), and ethylenediamine (560). Fundamental studies have been made in ethylenediamine (561) and glacial acetic acid (96). The possibility of using ethylenediamine, benzoyl chloride, acetic anhydride, morpholine, and phosphorus oxychloride as solvents has been explored, and the acid chlorides were found to react with mercury (562). The potential of the silver-silver chloride electrode relative to the hydrogen electrode in formic and acetic acids has been determined (437), and t h a t of the mercury anode in the presence of various anions in acetonitrile and dimethylformamide has been studied (179, 180). The halide ions give constant potentials but the perchlorate ion does not. The latter ion,
which is frequently used as a supporting electrolyte, is deposited at the platinum electrode in acetonitrile at very positive potentials and forms a free radical (559). Clod-
-+
CIOl
+e
Clod $- CHaCN HC104 2CHzCN + (CHzCN), -+
+ CHzCN
In studies on supporting electrolytes, methods for purifying tetrabutylammonium iodide by crystallization (586), and tetraalkylammonium salts (363) and ethyl alcohol (696) by electrolytic means, are given. The pH of Britton-Robinson buffers using tetramethylammonium hydroxide in place of sodium hydroxide has been determined (77) and tetramethylammonium phosphate buffers have been compared with the corresponding sodium phosphate buffers (678). I n other work, the catalysis of hydrogen evolution by organic compounds a t the dropping mercury electrode has been investigated (592) and found t o be characteristic only of nitrogen and sulfur-containing materials (592). A patent has been issued for the use of a graphite electrode in the determination of organic compounds (170). REVERSIBLE SYSTEMS
The polarographic behavior of quinones and hydroquinones continues t o be used to test new techniques, electrodes, and solvents in polarography. This system was not reversible at the volt-
