Direct and simultaneous determination of molybdenum and vanadium in sea-water using a multielement electrothermal atomic absorption spectrometer

Direct and simultaneous determinations of Mo and V in seaemission spectrometry (ICP-AES)26 and mass spectrometry water using a multi-element electrothermal atomic absorption (ICP-MS),27,28 X-ray fluorescence spectrometry,29 cathodic spectrometer (Perkin-Elmer SIMAA 6000) are described. stripping voltammetry (CSV)30 and multi-element electrotherThree kinds of chemical modifier [Mg(NO 3 ) 2 , Pd(NO 3 ) 2 and mal atomic absorption spectrometry (ETAAS).31–36 Each a mixture of both] were tested. A simple calibration curve instrument has its particular advantages and disadvantages. method could be used to determine Mo in sea-water using Pd The most important commercially available multi-element or a mixture of Pd and Mg as the chemical modifier. A instruments for trace elemental determination are ICP-based. standard additions method was used to determine V and to The applicability of ICP-based instruments has been limited determine Mo and V simultaneously in sea-water. The by the difficulty in dealing with samples with high salt concendetection limits were 0.35–0.60 mg l−1 for Mo. The detection trations and the need for relatively large sample volumes. limit for V in this work (0.32–0.51 mg l−1) is much lower than Consequently, separation or preconcentration of the analytes those reported in the literature (18–50 mg l−1), such that direct from the matrix prior to the measurement is necessary. determination of V in unpolluted sea-water (<2 mg l−1) by Although ICP-MS has emerged as a method with a power of ETAAS is possible. The RSDs for the simultaneous detection which is at least comparable to that of ETAAS, the determination of Mo and V in nearshore or open ocean seaMS detector is complex and expensive, which has limited the water are ∏11% using a mixture of Pd and Mg as the widespread use of ICP-MS in routine work. In recent years, chemical modifier. The accuracy of the method for Mo many kinds of multi-element ETAAS instrument have been determination was confirmed by the analysis of two kinds of developed and become commercially available, hence the applicertified reference sea-water. There is no certified value of V cations of ETAAS in multi-element determinations are of great provided for these reference sea-water samples. The interest.31–36 experimentally determined of V concentrations were compared Several papers have appeared concerned with the direct with values reported in the literature. determination of Mo3,4,37,38 and V38–40 in sea-water by ETAAS. The direct determination of Mo in sea-water by ETAAS has