SHORT COMMUNICATION A SPECTROPHOTOMETRIC METHOD OF DETERMINATION OF ENDOSULFAN (THIODAN) IN AIR

摘要

Airborne endosulfan is sampled in a train of a microfibre glass or cellulore membrane filter and silica gel, desorbed in methanol and saponified with potassium hydroxide to yield sulphur dioxide. The sulphur dioxide released is spectrophotometrically quantified as a red-purple para-rosaniline methyl sulphonic acid produced with acid-bleached para-rosaniline and formaldehyde. The spectrophotometric procedure follows the Beer-Lambert law in the endosulfan concentration range of 2-140 μg and the coefficient of variation (CV) of this method is 6.0%. The sampling efficiency of silica gel for endosulfan vapour at a sampling rate of 11. min~(-1) in the concentration range 0.5-3.0 mg m~(-3) is found to be 99.8% (CV = 4.9%). The desorption efficiency of methanol for endosulfan trapped in silica gel was measured and found to be 9% (CV = 2.0%). The method is free from interference by atmospheric sulphur dioxide.