Ionic liquid as ion-pairing reagent for liquid–liquid microextraction and preconcentration of arsenic species in natural waters followed by ETAAS

Abstract

A simple and highly efficient microextraction methodology was developed for arsenate [As(V)], arsenite [As(III)] and organic arsenic (i.e., DMA and MMA) preconcentration and determination based on the novel use of tetradecyl(trihexyl)phosphonium chloride ionic liquid (CYPHOS Ò IL 101) as an ionpairing reagent. As(V) species was selectively separated by forming As(V)-molybdate heteropoly acid [As(V)-MHPA] complex with molybdenum, followed by ion-pairing reaction with CYPHOS Ò IL 101 and microextraction in chloroform. Arsenic detection was performed by electrothermal atomic absorption spectrometry (ETAAS). Under optimum conditions, the analyte extraction efficiency was 99% and yielded a preconcentration factor of 125 with only 5.00 mL of sample. The detection limit was 0.002 mg L À1 as As(V). The relative standard deviation (RSD) for six replicate measurements at 1.5 mg L À1 of As were 4.1%, 4.9% and 5.0% for As(V), As(III) and total organoarsenicals, respectively. The proposed methodology was successfully applied for As speciation analysis in several types of water samples.

Aggregation Behavior of Several Ionic Liquids in Molecular Solvents of Low Polarity—Indication of a Bimodal Distribution

“…ILs have been shown to homogenize and thus activate rhodium catalysts in the hydrogenation of liquid organic reactants in which they were dissolved at dilute concentrations . Low‐dielectric solvents such as chloroform (CHCl 3 ) are being used with ILs, for example, for morphology studies on the pores of hybrid organic–inorganic materials, as co‐solvents for chemical reactions, and for liquid–liquid microextraction . Therefore, there is a growing need for understanding dilute solutions of ILs in molecular solvents.…”

“…[16] Low-dielectric solvents such as chloroform (CHCl 3 )a re being used with ILs, for example, for morphologys tudies on the pores of hybrid organic-inorganic materials, [17] as co-solvents for chemical reactions, [18] and for liquid-liquidm icroextraction. [19] Therefore, there is ag rowingn eed for understanding dilute solutions of ILs in molecular solvents. Despite this need, these solutionsa re not well understood [20] because studies of nonaqueouselectrolyte solutionsw ould normally involve either low-molecular-weight alcohols or polar solvents such as acetonitrile or acetone, [21][22][23] and not solvents ofl ow polarity because of the extremely low solubility of traditional mineral salts in such media.…”

“…The structure and dynamics of ion pairing and aggregation is studied by concentration-and temperature-dependent measurements of 1 Ha nd 19 Fs elf-diffusion coefficients, viscosity,a nd conductivity for the following five solutions: 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C n mim][NTf 2 ], n = 2, 4, 6) in dichloromethane (CH 2 Cl 2 ), and [C 6 mim][NTf 2 ]i n tetrahydrofuran (THF) and chlorobenzene( C 6 H 5 Cl). The temperature dependenceofthese properties at constantILconcentrations follows the Arrhenius law for all five solutions.…”

Atomic spectrometry update. Elemental speciation

“…79 The As V species was selectively separated by forming As V -molybdate heteropoly acid complex with molybdenum, followed by ion-pairing reaction with tetradecyl(trihexyl) phosphonium chloride and microextraction in chloroform. Arsenic detection was performed by ETAAS.…”

Vapor generation – atomic spectrometric techniques. Expanding frontiers through specific-species preconcentration. A review

“…Since only few atomic spectrometric techniques are selective for the determination of species, sample pretreatments becomes a prominent feature that enables the possibility to discriminate between total content of a trace element and the content of each individual chemical form in which it occurs. The quantitation of individual forms of an analyte is termed speciation analysis (specific-species determination); and most analytical methods employed for speciation involve the hyphenation of an atomic spectrometric detector with a separation technique namely chromatography (LC or GC) [7,12,[16][17][18][19][20][21][22][23][24], capillary electrophoresis (CE) [25][26][27], solid phase extraction (SPE) [13,[28][29][30][31][32][33][34][35][36][37], liquid-liquid extraction (LLE) with its variants [38][39][40][41][42][43], among others. The vapor generation is thus a derivatization step after the separation process that preconcentrate further the analyte(s) with considerable improvements in selectivity [6].…”