Spectroscopic detection of halocarbons using modified Fujiwara reactions

The Fujiwara reaction is the only known reaction for detecting halocarbons spectrophotometrically in the visible region, and it has been conducted with toxic, offensive-smelling pyridine and a strong base such as NaOH. New alternative approaches to conducting the Fujiwara reactions have been developed using solid pyridine derivatives and new bases for the detection of chloroform and carbon tetrachloride. The reactions of these halocarbons with 2,2′-dipyridyl (or 4,4′-dipyridyl) and tetra-n-butylammonium hydroxide (n-Bu4NOH) or potassium tert-butoxide (KO-t-Bu) were found to give colored species with detection limits of 0.17 mg/L for chloroform and 0.50 mg/L for CCl4 (using 2,2′-dipyridyl and n-Bu4NOH). The use of potassium tert-butoxide as the base in the Fujiwara reactions allows for the detection of the halocarbons in systems sensitive to water.