Method for screening barley and wheat samples for mercury.

Abstract

AbstractA flameless atomic absorption method on undigested crushed grain samples was used for screening large numbers of samples in Iraq in 1972 in an outbreak of methylmercury epidemy which occurred after the misuse of seed wheat treated with methyl‐mercury fungicide. In the standard procedure 1 g of crushed grain was added to a reaction vessel with 1 ml of 1% cysteine, 20 ml of 1% saline and 10 ml of 16 N‐H2SO4. Methylmercury and all the other forms of mercury were converted to atomic mercury by the combined SnCl2–CdCl2 reagent after the addition of 20 ml 45% NaOH. Atomic mercury was moved from the reaction vessel through the gas cell of a mercury vapour meter by an air pump. Deflection on the scale of the mercury vapour meter was recorded and by use of standard additions to the same sample mercury contents were calculated. It was found that from crushed grain approximately 60% of the mercury was released compared with estimations carried out on digests necessitating the use of a correction factor for quantitation. This screening technique which does not need elaborate instruments, special skill and care, made it possible for two people to screen approximately 30 samples per hour and to overcome the emergency situation which had been presented by the large number of wheat stocks suspected of containing methylmercury.