Simultaneous multi-element determination of hydride-forming elements by "in-atomiser trapping" electrothermal atomic absorption spectrometry on an iridium-coated graphite tube
J. Murphy et al., Simultaneous multi-element determination of hydride-forming elements by "in-atomiser trapping" electrothermal atomic absorption spectrometry on an iridium-coated graphite tube, J ANAL ATOM, 14(10), 1999, pp. 1593-1600
A simultaneous multi-element approach utilising "in-atomiser trapping" elec
trothermal atomic absorption spectrometry (ETAAS) for As, Bi, Sb and Se was
developed. The approach uses flow injection methodology and hydride format
ion with sodium tetrahydroborate to sequestrate the hydrides of the element
s of interest on an Ir pre-coated graphite tube. Since the efficiency of th
e hydride formation depends on the oxidation state of the analyte, an off-l
ine reduction process was included to ensure that the analyte to be determi
ned was in the most sensitive and favourable oxidation state. Initially fiv
e elements, As, Bi, Sb, Se and Te, were considered for simultaneous "in-ato
miser trappin". The elements were split into two groups reflecting the natu
re of the reducing agent required by each of the elements. Group A consiste
d of As, Bi and Sb and used L-cysteine as the reducing agent, whilst Group
B consisted of Bi, Se and Te and used concentrated HCl as the reducing agen
t. However, Te was later removed from Group B due to problems in identifyin
g a set of compromise conditions which enabled all three elements to be det
ermined simultaneously. Bismuth featured in both groups as it did not requi
re a reduction step. Various tube coatings were considered and Ir and Zr we
re evaluated. Iridium was found to be well suited to this application. The
characteristic masses obtained using this method were 177, 91, 107 and 90 p
g for As, Bi, Sb and Se, respectively, yielding detection limits (500 mu l
sample loop) of 0.82, 0.04, 0.26 and 0.29 mu g l(-1). Precision for analyte
s at the 5 mu g l(-1) level was typically better than 3.5% RSD. The method
was validated by the analysis of two Certified Reference Materials and good
agreement was found with the certified values.