Synthesis of mixed coating with multi-functional groups for in-tube hollow fiber solid phase microextraction-high performance liquid chromatography-inductively coupled plasma mass spectrometry speciation of arsenic in human urine

A novel method based on in-tube hollow fiber-solid phase microextraction (in-tube HF-SPME) on-line coupled with ion pair reversed phase high performance liquid chromatography (IP-RP-HPLC)-inductively coupled plasma mass spectrometry (ICP-MS) was developed for arsenic speciation. Partially sulfonated poly(styrene) (PSP) and mixed-sol of 3-mercapto propyltrimethoxysilane (MPTS) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AAPTS) were prepared and immobilized in the pores and the inner surface of polypropylene hollow fiber (HF). The prepared MPTS-AAPTS/PSP immobilized HF was characterized by FT-IR spectroscopy and scanning electron microscope (SEM). With arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC) as model arsenic species, a series of factors that influence the extraction of target arsenic species by in-tube HF-SPME, including pH value, sample volume and flow rate, elution conditions and interference of co-existing ions were investigated in details, and the conditions for subsequent HPLC-ICP-MS determination were also optimized. Under the optimal conditions, the sampling frequency was 6.5 h⁻¹, the detection limits for six target arsenic species were in the range of 0.017-0.053 μg L⁻¹ with the relative standard deviations (c(As(V),MMA)=0.1 μg L⁻¹, c(As(III),DMA,AsB,AsC)=0.5 μg L⁻¹, n=5) ranging in 3.1-8.7%, and the enrichment factors were varied from 4 to 19-fold. To validate the accuracy of this method, certified reference materials DORM-2 (dogfish) and CRM No. 18 (human urine) were analyzed, and the determined values were in good agreement with the certified values. The proposed method was also successfully applied for arsenic speciation in human urine samples, and the recoveries for the spiked samples were in the range of 92.6-107%. The self-designed in-tube HF-SPME-HPLC-ICP-MS system shows high efficiency and good stability, and the proposed method is sensitive and suitable for simultaneous speciation of organic and inorganic arsenic species (including anions and cations) in biological samples.