Abstract
Since H. Bode has recommended the use of brucine as a substitute for stinking pyridine for the spectrophotometric determination of arsenic with silverdiethyldithiocarbamate (Ag-DDTC), this base has preferably used, despite of the low sensitivity. In this paper, the use of cinchonidine, as 0.1 % chloroform solution containing 0.25% Ag-DDTC, was proposed from our study on various organic bases, because of less odor and relatively high sensitivity. The apparent molar extinction coefficient of the colored species is 1.56×104 dm3 mol-1 cm-1 at 510 nm, which is higher than that with brucine and is somewhat lower than that with pyridine. The color developed is stable at least for an hour at room temperature. Amounts of arsenic up to 20 μg are determined by measuring the absorbance at 510 nm and by using a linear calibration curve with good reproducibility, the coefficient of variation being 2% at 10μg level. Cinchonine can also be used as an alternative base.
