DETERMINATION OF TIN IN INDIUM-PHOSPHIDE BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY AND INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Two independent methods for the determination of tin in tin-doped indi um phosphide were developed and compared. The electrothermal atomic ab sorption spectrometry (ETAAS) method utilized both platform atomizatio n and a chemical modifier composed of orthophosphoric acid and magnesi um nitrate. The detection limit (6s(b)) is 5.0 mug g-1 for a 250 mg sa mple. The inductively coupled plasma mass spectrometry (ICP-MS) method monitored the Sn-120 isotope and a typical detection limit (6s(b)) of 0.5 mug g-1 for a 20 mg sample was obtained. The observed range is 0. 2-0.75 mug g-1 depending on the instrumental stability and response. T he matrix effect was investigated in both methods, and the results ind icated that matrix-matched calibration standards should be used. Indiu m phosphide wafers, obtained from a single crystal grown from a tin-do ped melt, were analysed by using both methods to determine the tin con tent and the change in concentration along the crystal. Results having means that did not differ significantly (P=0.05) were achieved. Both the ETAAS and ICP-MS techniques were useful in determining tin in the tin-doped InP, however ICP-MS without internal standardization was les s precise. When real samples containing 35-149 mug g-1 of Sn were anal ysed, the relative standard deviation was in the range 12.9-4.3% for I CP-MS and 3.4-2.0% for ETAAS.