Direct determination of zinc in plasma by graphite furnace atomic absorption spectrometry using palladium/magnesium and EDTA matrix modification with high temperature pyrolysis
High prevalence of zinc deficiency stemming from malnutrition, gastrointestinal diseases and low dietary intake accounts for detection of zinc in plasma being a frequently requested clinical pathology assay. Serum and plasma zinc determination by graphite furnace atomic absorption spectrometry (GFAAS) has previously been hampered by significant interfering species and intolerance to high pyrolysis temperatures. In this Technical Note, we report a GFAAS method developed to overcome these restrictions by employing two matrix modifiers and a high pyrolysis temperature. Serum and plasma samples were diluted twenty times with an Antifoam/Triton-X-100 diluent and measured against aqueous standards similarly diluted, without the use of Zeeman correction. Interference from chloride was eliminated using a combination of two matrix modifiers: a magnesium/palladium mixture combined with 1% (w/v) aqueous ethylenediaminetetraacetic acid (EDTA). This allowed a pyrolysis temperature of 1000 °C to be used, which resulted in the complete removal of chloride interference. The accuracy of the method was verified by direct comparison with inductively coupled plasma-mass spectrometry (ICP-MS) and flame atomic absorption spectrometry (FAAS); analysis of a commercial reference material (Seronorm); and by analytical recovery studies.