Study on S2 emission response from sulphur-containing amino acids in molecular emission cavity analysis

Several factors which affect S2 emission response from sulphur-containing amino acids are investigated by molecular emission cavity analysis. It is found that multi-peaked responses observed from the amino acids result from heterogeneous gasification of the sample rather than formation of non-volatile compounds. A portion of the sample in a cavity is rapidly gasified by contact with flame gases and the others are slowly and thermally decomposed with temperature rise of the cavity. Thus, sample gasification processes are mainly discussed on the basis of several effects on the emission response, such as sample location within the cavity, addition of acids or bases, cavity temperature and flame composition. It is suggested that the amphoteric property of amino acids suppresses the rapid gasification process by contact with flame gases. Temporary condensed water on the cavity surface on introduction into a flame significantly affects the emission response from the amino acids and a mechanism for the effect is discussed.