Dispersive liquid–liquid microextraction and microsample injection system coupled with inductively coupled plasma-mass spectrometry for inorganic arsenic speciation in natural waters

Abstract

A method was developed for inorganic arsenic speciation analysis of water samples by a microsample injection system coupled with inductively coupled plasma mass spectrometry (MIS-ICP-MS) following a validated dispersive liquid–liquid microextraction (DLLME). Prior to DLLME speciation analysis, a simple robust microsample injection system was successfully adapted to ICP-MS. A sampling volume of 90 µL provided almost the same signals as the signals obtained by means of a conventional continuous nebulization sampling system for the ICP-MS instrument. After DLLME, the final solution was injected into nebulizer of ICP-MS using the microsample injection system. Under the optimized conditions, the analyte from only 5.0 mL water sample was concentrated by a factor of 48 with detection limits reaching 0.0031 µg L⁻¹ for arsenic. The calibration curve had a linear range of 0.0084–0.0800 µg L⁻¹ (r ²= 0.999). The relative standard deviations (RSD, n = 6) were <4%. The proposed method was applied to the speciation of inorganic arsenic in various water samples with satisfactory results. The determination of arsenite and total As in river, pond, tap and bottled water samples was acheived by the standard addition method. The recoveries for spiked As(III) and As(V) from understudied water samples were in the range of 95–108%.

Keywords:

• arsenic
• speciation
• dispersive liquid–liquid microextraction
• microsample injection
• inductively coupled plasma mass spectrometry
• water samples

Acknowledgement

L. Elçi is grateful for the financial support of The Scientific and Technological Research Council of Turkey (TUBITAK).