Simultaneous determination of Cl, Br and I by aerosol-assisted PVG-ICP-MS

Abstract

Simultaneous determination of Cl, Br and I by aerosol-assisted photochemical vapor generation (PVG) with detection by inductively coupled plasma mass spectrometry (ICP-MS) was investigated. The photoreactor comprised a modified cyclonic spray chamber fitted with a central UV source for irradiation of pneumatically generated sample aerosol. A systematic evaluation of variables was conducted, focusing on achieving compromise optimal PVG conditions suitable for simultaneous Cl, Br and I generation. By using a sample medium comprising 1% v v-1 acetic acid containing 20 mg L-1 Cu2+ (as a transition metal mediator), the signal intensities for Cl, Br and I were enhanced by 3-, 40- and 30-fold, respectively, compared to those obtained by conventional pneumatic nebulization (PN). LODs of 4.2 ng mL-1, 6.3 pg mL-1 and 1.9 pg mL-1 were achieved for Cl, Br and I, respectively, with corresponding estimated overall PVG efficiencies of 10, 99 and 90%. In addition to the halides, halate species, i.e., ClO3-, BrO3- and IO3-, were also examined, but poor PVG efficiencies (lower than 5%) were encountered. However, addition of 20 mg L-1 SO32- to the generation medium enhanced response for BrO3- and IO3-, achieving similar values to those obtained from Br- and I-. The impact of NO3‑ (as both HNO3 and KNO3) and NH4OH on generation efficiencies was also investigated. The method was tested by the successful simultaneous determination of total Cl, Br and I in a variety of certified reference materials (CRMs) digested by microwave-induced combustion (MIC), including NRCC DORM-5 - Fish Protein, NIST SRM 1632c - Coal, NIST SRM 1515 - Apple Leaves and NIST SRM 1549 - Non-fat Milk Powder.