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4196866 
Journal Article 
Simultaneous Polarographic Determination of Parathion and Paraoxon. Catalytic Hydrolysis of Parathion by Palladium(II) 
Hernandez Mendez, J; Carabias Martinez, R; Sanchez Martin, J 
1986 
Yes 
Analytical Chemistry
ISSN: 0003-2700
EISSN: 1520-6882 
NIOSH/00194060 
58 
9 
1969-1972 
A proposed method for the simultaneous polarographic determination of parathion (56382) and paraoxon (311455) was described. Fifty milliliters of a sample containing parathion and paraoxon in a 30:70 solution of methanol and water buffered to pH 8.0 with an acetic-acid/acetate buffer were placed in a polarographic cell thermostated at 25 degrees-C. Nitrogen was bubbled through the cell for 15 minutes to remove the oxygen. Polarograms were recorded at voltages between 0.0 and 2.0 volts using a pulse amplitude of -50 millivolts (mV) and a scan rate of 4mV per second with mercury drop, platinum, and saturated calomel electrodes. Paraoxon was determined from its reduction peak. Divalent palladium at a concentration of 1.0x10(-4) molar was then added. The palladium catalyzed the hydrolysis of parathion to p-nitrophenol which was determined polarographically or amperometrically by measuring the peak at pH 8.0 or 9.25. Parathion and paraoxon could be simultaneously determined with an acceptable error in samples having parathion/paraoxon ratios greater than 1:45 and paraoxon/parathion ratios greater than 1:70. Experiments leading to optimization of the procedure were described. The authors conclude that the method can determine parathion and paraoxon with an acceptable margin of error as long as the parathion/paraoxon ratio is greater than 1:45 and the paraoxon/parathion ratio is greater than 1:70. For lower ratios they recommend that only the predominant species be determined.