Aminopolycarboxylate chelants (APCs) are extremely useful for a variety of industrial applications, including the treatment of toxic metal-contaminated solid waste materials.Because non-toxic matrix elements compete with toxic metals for the binding sites of APCs, an excess of chelant is commonly added to ensure the adequate sequestration of toxic metal contaminants during waste treatment operations. The major environmental impacts of APCs are related to their ability to solubilize toxic heavy metals. If APCs are not sufficiently eliminated from the effluent, the aqueous transport of metals can occur through the introduction of APCs into the natural environment, increasing the magnitude of associated

23A combination of solid phase extraction (SPE) columns was used for selective separation 24 of water-soluble arsenic species: arsenite, arsenate, monomethylarsonic acid (MMA) and 25 dimethylarsinic acid (DMA). The SPE columns, namely AnaLig TE-01 (TE-01), AnaLig 26 AN-01 Si (AN-01) and AnaLig As-01 PA (As-01), contain immobilized macrocyclic material 27 as the sorbent and commonly known as molecular recognition technology (MRT) gel. The 28 retention, extraction and recovery behavior of the MRT gel SPE columns were studied at pH 29 4-10. Fortified deionized water spiked with 100 µM of arsenic species were treated at the 30 flow rate of 0.2 mL min -1 . HNO 3 (1.0 and 6.0 M) was used as eluent to recover the retained 31 arsenic species from TE-01 and AN-01 SPE columns. Arsenic species retained in the As-01 32 column were eluted with HNO 3 (0.1 M) followed by NaOH (2.0 M). Likely interference from 33 the various coexisting ions (Na (10 mM) were negligible. Quantitative separation of As(III), As(V), MMA and DMA was 35 achieved based on the differences in extraction and recovery behavior of the MRT gel SPE 36 columns with pH for different arsenic species. Complexation between arsenic species and 37MRT gel is the core phenomenon of the proposed technique as the complexation of MRT 38 gels is expected to be stronger than the resin-based separation processes. MRT gel SPE 39 columns are advantageous as compared with other reported SPE columns in terms of its 40 performance with As(III). Effortless regeneration and unaltered separation performance of 41 the sorbent materials for more than 100 loading and elution cycles are other sturdy 42 characteristics to consider the MRT gel SPE columns for sensitive and selective arsenic 43 species separation. 44 45 Keywords: Solid phase extraction; Molecular recognition technology gel; water-soluble 46 arsenic; selective separation; pH 47 3 Introduction 48Arsenic, a ubiquitous toxic trace element, has raised a major toxicological and 49 environmental concerns (WHO, 2001). The concentration levels, oxidation and binding states, 50 ionic and molecular forms and metabolic pathways of As vary strongly in different 51 environmental compartments, food chains and ultimately in humans (Mandal and Suzuki, 52 2002). Widespread human exposure to high levels of As is reported to occur via drinking 53 water and contaminated water irrigated food causing both cancerous and non-cancerous 54 health effects (Karim, 2000;Rahman et al., 2008). 55Arsenite (oxidation state + III), arsenate (oxidation state + V), monomethylarsonic acid 56 (MMA) and dimethylarsinic acid (DMA) are common water-soluble arsenic species existing 57 in natural water systems-a major pathway of arsenic ingestion to humans (Smedley and 58 Kinniburgh, 2002). Arsenic toxicity in human depends strongly on its chemical form. As(III) 59 is 10 times more toxic than As(V) while almost 70 times more toxic than the methylated 60 forms, MMA and DMA (Squibb and Fowler, 1983). As(III), having successive acid 61 dissociation ...