Determination of ng/ml levels of sulphide by a chemiluminescent reaction.

Sulphide (0.1 ng/ml) is determined by measuring the chemiluminescence given by its oxidation in aqueous solution by hydrogen peroxide, catalysed by peroxidase. The detection limit is 0.05 ng/ml. Several other, rather less sensitive, systems are also described. Sulphite and thiocyanate, which depress the emission, are masked with formaldehyde.