Quantitative determination of chlorine by glow discharge quadrupole mass spectrometry in Zr–2.5Nb alloys

Abstract

Direct determination of chlorine in Zr–2.5Nb alloys down to parts per billion levels has been carried out by use of a glow discharge quadrupole mass spectrometer (GD-QMS). The ³⁵Cl isotope was used for quantification. The relative sensitivity factor (RSF) for chlorine in zirconium matrix (with a ³⁵Cl isotope) was determined using a zirconium matrix standard disc of known concentration of chlorine (155 ± 5 mg kg⁻¹) determined by turbidimetry. The concentrations of chlorine obtained using GD-QMS and by pyrohydrolysis-ion chromatography showed a good agreement, indicating the validity of the RSF value determined. Under optimised conditions the detection limit for chlorine (for 20 ms integration time and 140 points) was found to be 22 µg kg⁻¹ and the internal precision for the measurements was typically 1% RSD for mg kg⁻¹ levels and 10% RSD for µg kg⁻¹ levels. Determination of chlorine above 3 mg kg⁻¹ can also be done using the ³⁷Cl isotope. However, below 3 mg kg⁻¹ the interference due to the molecular ion, ³⁶Ar¹H⁺, starts dominating on the ³⁷Cl ion signal.