Carmen Moscoso-Pérez

Simultaneous pressurized enzymatic hydrolysis extraction and clean up for arsenic speciation in seafood samples before high performance liquid chromatography–inductively coupled plasma-mass spectrometry determination

The feasibility of pressurized conditions to assist enzymatic hydrolysis of seafood tissues for arsenic speciation was novelty studied. A simultaneous in situ (in cell) clean-up procedure was also optimized, which speeds up the whole sample treatment. Arsenic species (As(III), MMA, DMA, As(V), AsB and AsC) were released from dried seafood tissues using pepsin as a protease, and the arsenic species were separated/quantified by anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Variables inherent to the enzymatic activity (pH, temperature and ionic strength), the amount of enzyme (pepsin), and factors affecting pressurization (pressure, static time, number of cycles and amount of dispersing agent, C-18) were fully evaluated. Pressurized assisted enzymatic hydrolysis (PAEH) with pepsin can be finished after few minutes (two cycles of 2 min each one plus 3 min to reach the hydrolysis temperature of 50 °C). A total sample solubilisation is not achieved after the procedure, however it is efficient enough for breaking down certain bonds of bio-molecules and for releasing arsenic species. The developed method has been found to be precise (RSDs lower than 6% for As(III), DMA and As(V); and 3% for AsB) and sensitive (LOQs of 18.1, 36.2, 35.7, 28.6, 20.6 and 22.5 ng/g for As(III), MMA, DMA, As(V), AsB and AsC, respectively). The optimized methodology was successfully applied to different certified reference materials (DORM-2 and BCR 627) which offer certified AsB and DMA contents, and also to different seafood products (mollusks, white fishes and cold water fishes).

Multivariate optimisation of hydride generation procedures for single element determinations of As, Cd, Sb and Se in natural waters by electrothermal atomic absorption spectrometry

Continuous flow hydride generation procedures for As(III), total inorganic As, Cd, total inorganic Sb, Se(IV) and total inorganic Se from sea and hot-spring water samples were optimised by experimental designs. Ir-coated graphite tubes were used as preconcentration and atomisation medium of the hydrides generated. Several factors affecting the hydride generation efficiency were studied. Results obtained from Plackett-Burman designs suggest that sodium borohydride flow rate and reduction coil length, are significant factors for total inorganic arsenic hydride generation. For cadmium hydride generation the significant factors are hydrochloric acid concentration, hydrochloric acid and sodium borohydride flow rates and reduction coil length. For total inorganic antimony hydride generation the factors affecting the hydride generation procedure are hydrochloric acid and potassium iodide concentrations and reduction coil length; finally, pre-reduction coil length and oven temperature for the pre-reduction step are statistically significant factors for total inorganic selenium hydride generation. In addition, the factors studied for the arsenic and selenium hydride generation from As(III) and Se(IV) are not significant. From these studies, the significant variables were optimised by central composite designs. Validation carried out analysis on three reference materials: SLRS-4 (Riverie water), CASS-3 (seawater) and NIST-1643d.

Pressurized liquid extraction followed by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry for arsenic and selenium speciation in atmospheric particulate matter.

This paper describes the development of a chelating solvent-based pressurized liquid extraction (PLE) method for the simultaneous extraction of As and Se species (As(III), As(V), Se(IV) and Se(VI)) in atmospheric particulate matter (PM(10)). The extracted As and Se species were evaluated by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The feasibility of several pressurized chelating solvents was recently investigated to leach As and Se species from atmospheric particulate matter. The best results (high recoveries) were obtained when using EDTA. Experimental design approaches were used to achieve the best compromise conditions for the simultaneous extraction of As and Se species by EDTA-PLE. Analytical performances, such as limits of detection (in the range of 0.01-0.02 ng m(-3)), quantification (in the range of 0.02-0.07 ng m(-3)), and repeatability of the over-all procedure ( approximately 10%) were established. Finally, As and Se species were determined in several atmospheric particulate matter (PM(10)) samples collected in an urban area of A Coruña city (northwest coast of Spain) in 2006. In all the atmospheric particulate matter samples that were analysed, As(V) and Se(IV) (in the range of 0.17-0.60 ng m(-3)) were the major species found.

Determination of organotin compounds in waters by headspace solid phase microextraction gas chromatography triple quadrupole tandem mass spectrometry under the European Water Framework Directive.

The European Union Water Framework Directive (2013/39/EU) sets very restrictive environmental quality standards for 45 priority substances and other pollutants, including organotin compounds (OTCs). Therefore, it is necessary to develop analytical methods in compliance with the environmental quality standard (EQSs) proposed to protect the aquatic environment and humans. The proposed method (HS-SPME-GC-QqQ-MS/MS) allows the determination of OTCs, i.e. monobutyltin (MBT), dibutyltin (DBT) and TBT in water in the range of few ng L(-1). The method is nearly full automated, sensitive and simple; it involves less reagents, reduces waste, and is less-time consuming than traditional methods for OTCs. As such, the procedure connects with the principles of green analytical chemistry. Additionally, good precision (RSD<20%), a very low method quantification limit (MQL) (0.76 ng L(-1) for TBT by using only 10 mL of sample) and excellent linearity (range MQL-20 ng L(-1)) are achieved. Under these conditions, the very restrictive limits for the environmental quality standards (EQS) fixed by the 2013/39/EU Directive are achieved.

As, Bi, Sb and Sn determination in atmospheric particulate matter by direct solid sampling-hydride generation-electrothermal atomic absorption spectrometry

A novel, rapid and simple method by hydride generation-electrothermal atomic absorption spectrometry (HG-ETAAS) after direct As, Bi, Sb and Sn hydrides generation from untreated filters of atmospheric particulate matter (PM(10) and PM(2.5)) was optimised. PM(10) and PM(2.5) were not subjected to any pre-treatment: circular portions between 0.28 and 6.28cm(2) were directly placed into the reaction vessel of a batch mode generation system. A 2(8)x3/64 Plackett-Burman design was used as a multivariate strategy for the evaluation of the effects of several variables affecting the hydride generation, trapping and atomisation efficiencies. Trapping temperature was the most statistically significant variable for As, Bi and Sn. Atomisation temperature was also statistically significant for Sb determination. Optimum values of significant variables were selected by using univariate optimisation approaches. An aqueous calibration method was used throughout. The developed method has been found to be precise with relative standard deviations of 6.2, 5.3, 9.1 and 7.5% for 11 determinations in a filter sample containing 0.7, 1.0, 1.4 and 1.7microg l(-1) for As, Bi, Sb and Sn, respectively. Results obtained by direct solid sampling-HG-ETAAS have been found statistically comparable with those obtained after conventional method based on an acid digestion followed to ICP-MS. Absolute detection limits were 37, 15, 30, and 41ng l(-1) for As, Bi, Sb and Sn, respectively. Detection limits referred to the air volume sampled (in the range of 0.020-0.050ng m(-3)) were low enough for the determination of several hydride-forming elements from PM(10) and PM(2.5) samples collected in a non-polluted suburban area of A Coruña (NW Spain).

Bismuth determination in environmental samples by hydride generation-electrothermal atomic absorption spectrometry.

A hydride generation procedure, via flow injection, coupled to electrothermal atomic absorption spectrometry was optimised for Bi determination in sea water and hot-spring water and acid extracts from coal, coal fly ash and slag samples. The effects of several variables such as hydrochloric acid and sodium tetrahydroborate concentrations, hydrochloric acid and sodium tetrahydroborate flow rates, reaction coil length, trapping and atomisation temperatures, trapping time and the Ar flow rate have been investigated by using a 2(9)*3/128 Plackett-Burman design. From these studies, certain variables (sodium tetrahydroborate concentration and trapping time) showed up as significant, and they were optimised by a 2(2)+star central composite design. In addition, a study of the bismuthine trapping and atomisation efficiency from graphite tubes (GTs) permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide and tantalum carbide were investigated. The results obtained were compared with those achieved by iridium and zirconium-treated GTs. The best analytical performances, with characteristic mass of 35 pg and detection limit of 70 ng l(-1), were achieved by using U-treated GTs. Accuracy were checked using several reference materials: 1643d (Trace Elements in Water), TM-24 (Reference Water), GBW-07401 (Soil) and 1632c (Trace Elements in Coal).

Comparative study of different permanently-treated graphite tubes for the determination of As, Sb, and Se in natural waters by hydride generation-electrothermal atomic absorption spectrometry

Methods for the direct trace determination of As, Sb, and Se in natural waters involving hydride generation, trapping, and atomization of the hydride in a graphite furnace have been developed. Graphite tubes permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide, tantalum carbide, chromium carbide, and vanadium carbide were investigated for the in situ pre-concentration of the hydrides studied. The results obtained were compared with those achieved by iridium, tungstate and zirconium-treated graphite tubes (GT). Trapping on Zr-treated graphite tubes offers the best analytical performances for the hydrides studied, with characteristic masses of 45, 17 and 90 pg for As, Sb, and Se, respectively. In addition, the use of U-treated GTs offers adequate trapping efficiency for arsine; for stibine, the use of Cr3C2-, Cr2O3-, TaC-, VC- and U-treated GTs gives analytical performances similar to the use of Ir- and W-treated tubes. The accuracy was studied using TM-24, 1643d, CASS-3, and SLRS-4 reference materials. The 25 samples could be analyzed per hour.

Use of pressurized hot water extraction and high performance liquid chromatography-inductively coupled plasma-mass spectrometry for water soluble halides speciation in atmospheric particulate matter.

The feasibility of pressurized hot water extraction (PHWE) has been novelty investigated to speed up water soluble halide species (bromide, Br(-); bromate, BrO(3)(-); iodide, I(-) and iodate, IO(3)(-)) leaching from atmospheric particulate matter (PM(10) and PM(2.5)). Total bromine and iodine and total water soluble bromine and iodine have been assessed by inductively coupled plasma-mass spectrometry (ICP-MS). Water-soluble bromine and iodine species were also measured by ICP-MS after anion exchange high performance liquid chromatography (HPLC). Variables inherent to the pressurized hot water extraction process (temperature, modifier concentration, static time, pressure, number of cycles and dispersing agent mass) were fully studied. Results showed that the pressurized leaching procedure can be performed in 9 min (5 min for pre-heating, 2 min of static time, 1 min of purge time, and 1 min of end relief time). The use of diluted acetic acid as a modifier did not improve the target recoveries. Dispersing agent (diatomaceous earth) was not needed, which reduces the time for filling the cells. Water-soluble halides were reached under the following extraction conditions: extraction temperature of 100 °C, pressure of 1500 psi, static time of 2 min and 1 extraction cycle. Optimized HPLC conditions consisted of an isocratic elution with 175 mM ammonium nitrate plus 15% (v/v) methanol as mobile phase (optimum flow rate of at 1.5 mL min(-1)). Analytical performances, such as limits of detection and quantification, repeatability and analytical recoveries of the over-all procedure have been established. Results obtained show water soluble halides accounted for approximately 20.9±1.3 and 11.8±0.6% of the total bromine and total iodine, respectively. A 79 and 89% of bromine and iodine was non-water soluble, which may be organic non-water soluble species. Br(-) and IO(3)(-) were found to be the major species, and they accounted for 100% of the total water-soluble bromine and iodine.

Triphenyltin induces imposex in Nucella lapillus through an aphallic route

Triphenyltin (TPT) was used until recently as a biocide in antifouling systems and nowadays is still applied as an agriculture pesticide in some countries. This compound is known to cause imposex (the imposition of male characters in females of gastropod molluscs) in a very limited number of species, when compared with tributyltin (TBT), the universally recognized imposex-causing agent. In this study, we tested if TPT could induce imposex in females of the dog-whelk Nucella lapillus. Experimental groups of 40 females were injected with a volume of 2μL/g of soft tissue wet weight (ww) of one of the following treatments, using DMSO as a solvent carrier: DMSO (solvent control); 1μg/g ww of TBT (positive control); 0.2, 1 and 5μg/g ww of TPT and a non-injected group (negative control). Concentrations were confirmed in the organism tissues by means of chemical analyses of a pool of 10 specimens at T0 and then after the imposex analysis at T56days. After 8-week trial, results pointed out statistically significant differences between treatments, with both TPT and TBT positively inducing imposex. However, imposex development in TPT-injected females differed from that of TBT, since females that developed imposex presented an aphallic condition (no penis development) while the TBT-treated females developed standard imposex (with penis formation). These results suggest that TPT and TBT act differently in the sequential process of female masculinization, casting new insights about the hypothetical pathways underlying imposex development.

Reliable, rapid and simple method for the analysis of phthalates in sediments by ultrasonic solvent extraction followed by head space-solid phase microextraction gas chromatography mass spectrometry determination

In this work, a new reliable, simple and fast method for the determination of six PAEs in sediments, based on ultrasonic solvent extraction (USE) followed by head space solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry determination (GC-MS), is proposed. The extraction parameters were studied, and the most favourable conditions were selected. The analytical features of the method were calculated: matrix effect, accuracy (ranged from 90% to 111%), repeatability and intermediate precision (RSD <10%), detection and quantification limits of the method (ranged from 0.001µgg-1 (DOP) to 0.142µgg-1 (DEP)), and satisfactory results were obtained. Major advantages of this approach are low consumption of reagents and solvents, no clean-up or evaporation steps were required and minimum sample manipulation. In addition, cross contamination from glassware, solvents and samples is minimized, thus procedural blanks are keeping to a minimum.. The applicability of the proposed method was demonstrated analysing sediment samples from Galician coast (NW Spain). The proposed method allows the application in routine laboratory conditions and its implementation in environmental monitoring studies under the European Water Framework Directive (WFD) and Marine Strategy Framework Directive (MSFD).