title: Application of fast ultrasound water-bath assisted enzymatic hydrolysis--high performance liquid chromatography-inductively coupled plasma-mass spectrometry procedures for arsenic speciation in seafood materials.
abstract: Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40°C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 min). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb™ solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine, AsB; as well as monomethylarsonic acid, MMA; and arsenocholine, AsC) in a single run. Relative standard deviations (n=11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC-ICP-MS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 μg L(-1) (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 μg L(-1) (expressed as arsenic) for AsB. Germanium (5 μg L(-1)) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment.
authors.affiliation: Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, Avenida das Ciencias, s/n, 15782 Santiago de Compostela, Spain. antonio.moreda@usc.es
authors.forename: Antonio
authors.initials: A
authors.lastname: Moreda-Piñeiro
authors.forename: Jorge
authors.initials: J
authors.lastname: Moreda-Piñeiro
authors.forename: Paloma
authors.initials: P
authors.lastname: Herbello-Hermelo
authors.forename: Pilar
authors.initials: P
authors.lastname: Bermejo-Barrera
authors.forename: Soledad
authors.initials: S
authors.lastname: Muniategui-Lorenzo
authors.forename: Purificación
authors.initials: P
authors.lastname: López-Mahía
authors.forename: Darío
authors.initials: D
authors.lastname: Prada-Rodríguez
mesh_terms: D000818:Animals; D001152:Arsenicals / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D002101:Cacodylic Acid; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005399:Fishes; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D016014:Linear Models; D013058:Mass Spectrometry / Q000379:methods*; D008974:Mollusca / Q000737:chemistry; D010434:Pepsin A / Q000737:chemistry; D017747:Seafood / Q000032:analysis*; D052616:Solid Phase Extraction; D013010:Sonication / Q000379:methods*; D013696:Temperature
chemical_list: D001152:Arsenicals; D002101:Cacodylic Acid; D010434:Pepsin A