Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic flourescence spectrometry

Authors: ZHANG, WEIHONG - Chinese Academy Of Agricultural Sciences; QI, YUEHAN - Chinese Academy Of Agricultural Sciences; QIN, DEYUAN - Beijing Titan Instruments Co; LIU, JIXIN - Chinese Academy Of Agricultural Sciences; MAO, XUEFEI - Chinese Academy Of Agricultural Sciences; Chen, Guoying; WEI, CHAO - Chinese Academy Of Agricultural Sciences; QIAN, YONGZHONG - Chinese Academy Of Agricultural Sciences

Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2017
Publication Date: 4/4/2017
Citation: Zhang, W., Qi, Y., Qin, D., Liu, J., Mao, X., Chen, G., Wei, C., Qian, Y. 2017. Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic flourescence spectrometry. Talanta. 170:152-157.

Interpretive Summary: Presence of arsenic in algae is a public concern, especially the highly toxic inorganic form (iAs). In this work, an effective method was developed for iAs analysis that included digestion, reduction, conversion to arsenic bromide, and cleanup by solid phase extraction. Determination was finally performed by hydride generation atomic fluorescence spectrometry. Conditions of these steps were fully investigated and optimized. The method was applied to nine algae samples and achieved 98-103% recovery and 3 parts per billion detection limit.

Technical Abstract: Accurate, stable and fast analysis of toxic inorganic arsenic (iAs) in complicated and arsenosugar-rich algae matrix is always a challenge. Herein, a novel analytical method for iAs in algae was reported, using bromine halogenation and on-line nonpolar solid phase extraction (SPE) followed by hydride generation atomic fluorescence spectrometry (HG-AFS). The separation of iAs from algae was first performed by nonpolar SPE sorbent using Br- for arsenic halogenation. Algae samples were extracted with 1% perchloric acid. Then, 1.5 mL extract was reduced by 1% thiourea, and simultaneously reacted (for 30 min) with 50 uL of 10% KBr for converting iAs to AsBr3 after adding 3.5 mL of 70% HCl to 5 mL. A polystyrene (PS) resin cartridge was employed to retain arsenicals, which were hydrolyzed, eluted from the PS resin with H2O, and categorized as iAs. The total iAs was quantified by HG-AFS. Under optimum conditions, the spiked recoveries of iAs in real algae samples were in the 82–96% range, and the method achieved a desirable limit of detection of 3 ug kg-1. The inter-day relative standard deviations were 4.5% and 4.1% for spiked 100 and 500 ug kg-1 respectively, which proved acceptable for this method. For real algae samples analysis, the highest presence of iAs was found in sargassum fusiforme, followed by kelp, seaweed and laver.