Micro flow injection ICP-MS analysis of high matrix samples: an investigation of its capability to measure trace elements in iron meteorites

Abstract

The coupling of a micro-flow injection sample introduction system to a highly versatile quadrupole ICP-MS (FI-ICP-MS) has been demonstrated to achieve accurate and precise trace element measurements for several iron meteorites. Measurements were made for the trace siderophile elements, Ru, Au, Rh, Pd, Ir, Pt, Ga, Cr, Cu and Re, where results present good agreements for most metals to duplicate samples also measured by a sector-field ICP-MS (ICP-SFMS). A major advantage for trace element measurements by flow-injection ICP-MS is the added flexibility to increase the total dissolved solids (TDS) concentrations of the working solutions above the 2000 μg g⁻¹ ICP-MS limit. The FI-ICP-MS technique used in this study allowed the sample digests to be measured directly, where the TDS concentrations were 2.5 times the above limit. The data generated clearly demonstrate that the micro-flow inputs of the high matrix material never overloaded the plasma or compromised on instrument performance. Without the need for extra dilutions a better detection capability for most elements was found in comparison to those made by the ICP-SFMS, where all method detection limits were below 0.1 μg g⁻¹, apart from Ru and Ga. Furthermore, it was evident from the reduced sample preparation time, together with measurement times of less than 7 minutes per sample, that the FI-ICP-MS analysis was a much more rapid technique. The accuracy of the FI-ICP-MS technique was tested from the measurement of two synthetic iron meteorites. A selection of elements, including Cr, Ga, Ru, Ir and Re, gained absolute error values better than ±5%, where Re, the analyte with the lowest concentration, reported the lowest absolute error, with a value of less than ±1%. Precision, determined from two times the relative standard deviation of repeat measurements of the synthetic solutions (n = 7), gained values less than 10% for all elements.