Anal. Cbern. 1980, 52, 1 R-9R
Amperometric, Bipotentiometric, and Coulometr c T tration John T. Stock University of .Connecticut, Storrs, Connecticut 06268
programmable desk calculator can control the whole system (80). Photonietric monitoring has proved useful in automated devices, especially those designed for the determination of C 0 2 or other acidic substances (29, 93. 40, 118, 2 70, 171). Csually, the color change of thymolphthalein or similar indicator provides the prime signal. A single-beam fluorescence detector is an interesting alternative ( 3 0 ) .
This survey covers the period from the previous review (286) through October 1979. The order of treatment is the same as in that review. Unless otherwise specified, potentials are with respect to the saturated calomel electrode (SCE). Various general reviews refer to amperometric titration (21, 161,162, 169). Complexometric titrations in the micromolar range (69) and by use of an oxide electrode (75) have been discussed. A theoretical study of amperometric complexometric titration has shown that the solubility of the complex may be found from the d l l d V character near the equivalence point (256). Although still far less-used than amperometric techniques, bipotentiometric titrimetry has attracted some attention. Titration with polarized electrodes has been reviewed (55) and the amplitude-biased mode of differential electrolytic potentiometry has been appraised (26). Amperometry and coulometry in nonaqueous or essentially nonaqueous systems have been examined by various workers. The coulometric aspects, especially those of nonaqueous acid-base titrimetry, have been briefly reviewed (65). Coulometric methods have been treated in a book (135) and in several general reviews (3, 67,227, 229). Indirect coulometric titration with optical monitoring has been discussed in a survey of spectroelectrochemistry (114). An extensive review of microcoulometric methods for the determination of sulfur, chlorine, and sulfur in organic compounds has appeared (160). The value of the Faraday, of fundamental interest in all branches of coulometry, has been further discussed (71,332,
ACID-BASE REACTIONS Boron has been amperometrically titrated as the H 3 B 0 mannitol complex at a rotating tantalum or graphite an.& 161. Organotin halides have been titrated in i-PrOH with ethanolic KOH (254). Pulse polarographic indication has been used in the coulometric titration of submillimolar concentrations of various acids and bases (144). Coulometric tiIration has been used to study the effect of containment (various glasses, polyethvlene, etc.) on the stability of 1-5 m,M H K O , (304). Precise coulometric titration has been used to assay high-purity KH phthalate (333). Dissolution in boiling H3POl, scrubbing to remove HF and H2S,and potentiometric titration of CO, with electrogenerated BatOH)? are the essential steps in a method for carbonate determination in rocks (273). Heating in a stream of air, then coulometric titration of C 0 2 , has been used to determine carbon in carbonitrides (82). Low concentrations of carbon in BF3 have been determined by combustion ,n oxygen and coulometric titration of C 0 2 (164). Sulfur in geological and biological materials has been determined by coinbustion with V 2 0 5 and iron powder in an oxygen stream, removal of H F and HCI, absorbance in Na2S0,-H202 soluticm and potentiometric coulometric titration of the resulting H,S04 (163). Two-component mixtures of H2Se04,H2Se03,and H2Te0, have been coulometrically titrated to two successive end points (157). Following combustion, coulometric titration of H2S0, plus H2Se03has been used to determine sulfur and selenium in organic substances ( 1 2 ) . Iodometric titration of the same solution is then used to determine the H,SeO,. Essentially nonaqueous dimethglformamide (DMF)ethanolamine (29, 33, 34, 171) and 1-PrOH (118) have been used as absorption-titration solvents for the photometric coulometric titration of CO,. Conversion t o C 0 2 with Schutze’s reagent has allowed the technique to be used for the continuous monitoring of CO in steelworks atmospheres (29). Potentiometric indication has been used in coulometric titration of carboxylic acids in ethanol (207 or aqueous ethanol (133). Biamperometry at bismuth electrodes has been used to monitor the coulometric titration of such acids in Me2COMeOH and in DMF-MeOH media 1130,322, 3.23). Single acids and mixtures of mineral acids have been biamperometrically titrated in Ac20-AcOH that contains quinhydrone (90). The technique has also been used ior the coulometric titration of bases (901. Benzcyclane hydrogen fumarate has been titrated in Ac20-AcOH that contains hydroquinone (95). Aliphatic amines have been coulometrically titrated t o a potentiometric end point in CHCl,
