Nonthermal optical emission spectrometry for simultaneous and direct determination of zinc, cadmium and mercury in spray.

A nonthermal optical emission spectrometric (OES) system is developed for the simultaneous multi-element determination of zinc, cadmium and mercury, with a dielectric barrier discharge (DBD) microplasma generated on the nozzle of a pneumatic micronebulizer as the excitation source. After solution nebulization, zinc, cadmium and mercury are directly atomized and excited in the spray by a DBD microplasma for performing optical emission. The emission spectra are measured with a charge-coupled device (CCD) spectrometer. Various important parameters governing the analytical performance of the nonthermal OES system are scrutinized, encompassing the conditions of sample solution introduction, microplasma formation, signal collection and matrix matching for DBD-OES detection. With the characteristic emission lines of Zn 213.9 nm, Cd 228.8 nm and Hg 253.7 nm as the analytical lines for quantification, the detection limits for the simultaneous determination of Zn, Cd and Hg are 22, 1.6, and 10 μg L, respectively, and the corresponding linear ranges are 70-6000, 5-1000, and 35-2000 μg L, respectively. The accuracy of the present nonthermal OES system is confirmed by the determination of Zn, Cd and Hg in two certified reference materials, i.e., CRM 176 (city waste incineration ash) and GBW 08608 (water). The proposed nonthermal OES system provides a portable instrument for field analysis in emergency with low cost and low consumption.