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

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 cy anide in air by a kinetic-fluorimetric method within the 5-600 ng ml(-1) ra nge. The proposed method is based on the catalytic effect of cyanide on the oxidation of pyridoxal-5'-phosphate (PALP) by dissolved oxygen in the cati onic micellar medium afforded by dodecyltrimethylammonium bromide (DTAB). T he reaction was monitored by measuring the fluorescence of the oxidation pr oduct [4-pyridoxic acid 5-phosphate (PAP)]. The improved sensitivity provid ed 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 apparent ly increased reaction rate. The relative standard deviation for 50 ng ml(-1 ) of cyanide was 1.7%. Common interferences, such as those arising from car bon dioxide, nitrogen oxides (NOx) and sulfur oxides (SOx), were found not to affect the hydrogen cyanide determination. The interference from hydroge n sulfide could be detected (e.g, the kinetic curve recorded showed an indu ction period) and amended.