An impregnated filter sampling approach for determination of hydrogen cyanide in air by a kinetic-fluorimetric micellar method

Abstract

A new hydrogen cyanide collecting device based on the use of borosilicated micro-fibreglass filters impregnated with sodium hydroxide was proposed and its performance assessed. It was used for the determination of hydrogen cyanide in air by a kinetic-fluorimetric method within the 5–600 ng ml^–1 range. The proposed method is based on the catalytic effect of cyanide on the oxidation of pyridoxal-5′-phosphate (PALP) by dissolved oxygen in the cationic micellar medium afforded by dodecyltrimethylammonium bromide (DTAB). The reaction was monitored by measuring the fluorescence of the oxidation product [4-pyridoxic acid 5-phosphate (PAP)]. The improved sensitivity provided by DTAB micelles was due to an increase in the quantum yield of PAP when it was concentrated on the DTAB micellar surface, resulting in an apparently increased reaction rate. The relative standard deviation for 50 ng ml^–1 of cyanide was 1.7%. Common interferences, such as those arising from carbon dioxide, nitrogen oxides (NO_x) and sulfur oxides (SO_x), were found not to affect the hydrogen cyanide determination. The interference from hydrogen sulfide could be detected (e.g. the kinetic curve recorded showed an induction period) and amended.