Determination of zinc in diet and faeces by acid extraction and atomic absorption spectrophotometry

A simple acid extraction procedure for sample preparation of diet and faeces for zinc analysis by flame atomic absorption spectrophotometry is evaluated. About 0.5 g of homogenized diet or faeces was mixed with 6 ml 1 mol/l hydrochloric acid. After 24 h, 4 ml chloroform and 2 ml methanol was added to dissolve fatty components and reduce surface tension. The samples were centrifuged and the supernatants analysed. The sensitivity of the method was 1.7 mumol per 1000 g. The coefficient of intra-assay variation was for faeces 1.7% (n = 20), for diet 2.1% (n = 25). The coefficient of inter-assay variation was for faeces 4.7% (n = 24), for diet 4.9% (n = 20). Recovery of known amounts of zinc added to faeces was 99.7 +/- 3.1% (n = 50). Recovery of zinc added to diet was 98.9 +/- 2.9% (n = 47). A good agreement was found between zinc determinations by the acid extraction method and by a method of acid digestion.