Residue Analysis, Direct Potentiometric Method for Chloride Ion Applied to Residues of Chlorinated Insecticides

Abstract

The quantitative determination of chlorinated-insecticide residues in treated foodstuffs by total chlorine methods is expedited and simplified by the exploitation of an unusually sensitive direct potentiometric method for chloride ion. This method uses a pH meter and a silver-silver chloride vs. calomel electrode system, and responds reproducibly to as little as 0.02 p.p.m. of chloride ion. With the equipment and procedures recommended, the useful range, without concentration or dilution stages, appears to be from 0.02 p.p.m. to 10,000 p.p.m.

Continuous Chloride-Ion Combustion Method Applied to Determination of Organochlorine Insecticide Residues.

“…Other Factors. As discussed by Helmkamp et al (6) and as mentioned earlier, certain inorganic ions interfere in this method. Also, precision temperature control at the sensor electrode is essential by virtue of the Nernst equation.…”

“…to approximately 0.01 p.p.m. One total organic chloride method (4,6) consists of producing hydrogen chloride gas by combustion, trapping this gas in a dilute solution of sodium carbonate-containing chloridefree nitric acid to suppress the ultimately interfering (4,6) carbonate ion, and measuring the chloride ion concentration by simple direct potentiometry with a silver-silver chloride vs. slow leak calomel electrode system. Amounts of original insecticides are then calculated from their percentage Mack, and Childs and the pathway suggested in the present study is the principal rate-determining step reported here.…”

“…(4) Kharasch, N., Potempa, S. J., Wehrchloride compositions. This combustion chloride (1,4,6,9,11) direct potentiometric method (4, 6) is more advantageous (1,4,6,9) than the usual wet oxidation and other combustion (8) techniques for handling large numbers of samples routinely. The only two operating disadvantages of the so-called "manual" method (1,4,6,9) involve the two components of the union of combustion (1,4,9) with direct potentiometry (4,6): manually controlled combustions, which require up to 23 minutes each, can result in lost samples from incomplete burning or from too-rapid burning, and the transfers and other operations in "batchwise" direct potentiometry readily lead to inadvertent contamination by extraneous chloride ion in the laboratory atmosphere (inadequately cleaned glassware, etc.)…”

“…(5) Kice, J. L., Venier, C. G., Tetrahedron Letters 48, 3629 (1964). (6) Lenz, G. R., Martell, A. E., Biochemistry 3, 745 (1964). (7) Ldvtrup, S., Compt.…”

Potentiometric Measurement of pCl. Application to Determination of Chloride in Sweat, Urine, and Miscellaneous Solutions

“…The potentiometric determination of chloride has been studied with a concentration cell employing two silver-silver chloride electrodes (S, 11,24). A simpler and more direct potentiometric measurement of chloride has been the object of recent investigations (5,14,16). Chanin (5) used a cell with a silver-silver chloride indicator electrode and a mercury-mercurous sulfate reference electrode.…”