Quantification of Cr in Natural Sparkling Mineral Waters by Inductively Coupled Plasma-Mass Spectrometry

Natural sparkling mineral water contains high concentrations of HCO₃^- (about 1500 mg/L) and CO₂(about 400 mg/L) and the concentration of Cr is equal to or lower than the detection limit of Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Moreover, it is easy to form the polyatomic ion ⁴⁰Ar¹²C, which interferes with the determination of ⁵²Cr in the water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Therefore, it is not possible to accurately quantify Cr in natural sparkling mineral water by ICP-MS. In this paper, a new method is described to quantify Cr in natural sparkling mineral water. The water is heated to 100℃ for 2 minutes, cooled to room temperature, and the acidity of the samples is adjusted to 5% (volume ratio) with nitric acid，which promotes HCO₃^- and H⁺ reactions to generate CO₂ gas, thus being rapidly released. The interference of ⁴⁰Ar¹²C on ⁵²Cr is eliminated by this pretreatment of the natural sparkling mineral water, and the accurate determination of Cr in the water was conducted by ICP-MS. The detection limit of this method is 0.23 ng/mL. The results were satisfactory with the recoveries from 92.3% to 93.7%. This method is not only simple and practical, but can also be used to simultaneously and accurately quantify Ni, Cu, As, Cd and Pb in the water samples by ICP-MS. Its precision and accuracy meet the requirements of natural mineral water analysis.