Reverse flow injection spectrophotometric for determination of aluminium(III)

A reverse flow injection analysis (rFIA) spectrophotometric method has been developed for the determination of aluminium(III). The method was based on the reaction of Al(III), quercetin and cetyltrimethylammonium bromide (CTAB), yielding a yellow colored complex in an acetate buffer medium (pH 5.5) with absorption maximum at 428 nm. The rFIA parameters that influence the FIA peak height have been optimized in order to obtain the best sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and Al(III) concentrations were obtained over the concentration range of 0.02-0.50 mg L⁻¹ with a correlation coefficient of 0.9998. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.007 and 0.024 mg L⁻¹, respectively. The repeatability was 1.10% (n = 11) for 0.2 mg L⁻¹ Al(III). The proposed method was applied to the determination of Al(III) in tap water samples with a sampling rate of 60 h⁻¹. Results obtained were in good agreement with those obtained by the official ICP-MS method at the 95% confidence level.     

A dispersive liquid-liquid microextraction procedure for determination of boron in water after ultrasound-assisted conversion to tetrafluoroborate

A novel, simple and green procedure is presented for the determination of boron. The method is based on ultrasound-assisted conversion of boron to tetrafluoroborate anion and the formation of an ion pair between BF₄⁻ and Astra Phloxine reagent (R), followed by dispersive liquid-liquid microextraction of the ion pair formed and subsequent UV-vis spectrophotometric detection. The conversion of boron to tetrafluoroborate anion is performed in an acidic medium of 0.9 mol L⁻¹ H₂SO₄ in the presence of 0.1 mol L⁻¹ F^- by means of 10 min of ultrasonication. The extraction of the ion pair formed between BF₄⁻ and R (1 × 10⁻⁴ mol L⁻¹ R) is carried out by dispersive liquid-liquid microextraction using 0.5 mL of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as dispersive solvent) in a ratio of 1:1:2. The absorbance of the coloured extracts obeys Beer's law in the range 0.22-18.7 mg L⁻¹ of B(III) at 553 nm wavelength. The limit of detection calculated from a blank test (n = 10) based on 3 s is 0.015 mg L⁻¹ of B(III). The method was applied to the determination of boron in mineral waters.     

A green analytical procedure for flow-injection determination of nitrate in natural waters

Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange column for separation of nitrate from interfering species. The proposed method employs only one reagent (HClO₄) in a minimum amount (equivalent to 18 μL concentrated acid per determination), and allowed nitrate determination within 0.50-25.0 mg L⁻¹, without interference of up to 200.0 mg L⁻¹ humic acid; 1.0 mg L⁻¹ NO₂⁻; 200.0 mg L⁻¹ PO₄³⁻; 75.0 mg L⁻¹ Cl⁻; 50.0 mg L⁻¹ SO₄²⁻ and 15.0 mg L⁻¹ Fe³⁺. The detection limit (99.7% confidence level) and the coefficient of variation (n = 20) were estimated as 0.1 mg L⁻¹ and 0.7%, respectively. The results obtained for natural water samples were in agreement with those achieved by the reference method based on nitrate reduction with copperized cadmium at the 95% confidence level.     

Sensitive determination of fluoride in biological samples by gas chromatography–mass spectrometry after derivatization with 2-(bromomethyl)naphthalene

A gas chromatography–mass spectrometric method was developed in this study in order to determine fluoride in plasma and urine after derivatization with 2-(bromomethyl)naphthalene. 2-Fluoronaphthalene was chosen as the internal standard. The derivatization of fluoride was performed in the biological sample and the best reaction conditions (10.0 mg mL⁻¹ of 2-(bromomethyl)naphthalene, 1.0 mg mL⁻¹ of 15-crown-5-ether as a phase transfer catalyst, pH of 7.0, reaction temperature of 70 °C, and heating time of 70 min) were established. The organic derivative was extracted with dichloromethane and then measured by a gas chromatography–mass spectrometry. Under the established condition, the detection limits were 11 μg L⁻¹ and 7 μg L⁻¹ by using 0.2 mL of plasma or urine, respectively. The accuracy was in a range of 100.8–107.6%, and the precision of the assay was less than 4.3% in plasma or urine. Fluoride was detected in a concentration range of 0.12–0.53 mg L⁻¹ in six urine samples after intake of natural mineral water containing 0.7 mg L⁻¹ of fluoride.     

Development of method for the speciation of inorganic iron in wine samples

In this paper, we proposed a procedure for the determination of iron(II) and total iron in wine samples employing molecular absorption spectrophotometry. The ligand used is 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) and the chromogenic reaction in absence or presence of ascorbic acid (reducing agent) allows the determination of iron(II) or total iron, respectively. The optimization step was performed using a multivariate technique (Box Behnken design) involving the factors pH, acid ascorbic concentration and reaction time.The method allows the determination of iron(II) and iron(III) in wine samples, with limits of detection and quantification 0.22 and 0.72 μg L⁻¹, respectively. The precision expressed as relative standard deviation (R.S.D.) was 1.43 and 0.56% (both, n = 11) for content of iron(II) in wine samples of 1.68 and 4.65 mg L⁻¹, and 1.66 and 0.87% (both, n = 11) for content of total iron in wine samples of 1.72 and 5.48 mg L⁻¹.This method was applied for determination of iron(II) and total iron in six different wine samples. In these, the iron(II) content varied from 0.76 to 4.65 mg L⁻¹ and from 1.01 to 5.48 mg L⁻¹ for total iron. The results obtained in the determination of total iron by Br-PADAP method were compared with those that were performed after complete acid digestion in open system and determination of total iron employing FAAS. The method of regression linear was used for comparison of these results and demonstrated that there is no significant difference between the results obtained with these two procedures.     

Highly selective flow injection spectrophotometric determination of gold based on its catalytic effect on the oxidation of variamine blue by potassium iodate in aqueous N,N-dimethylformamide medium

A highly selective and simple flow injection method is reported for the determination of Au(III) in jewel samples. The method is based on the catalytic effect of Au(III) on the oxidation of 4-amino-4′-methoxydiphenylamine hydrochloride (Variamine Blue B base, VB) by KIO₃. The colored reaction product was monitored spectrophotometrically at 546 nm. A volume fraction of 40% N,N-dimethylformamide (DMF) greatly enhances the selectivity of the method. The chemical (pH and concentrations of reagents) and instrumental variables (sample injection volume, reagents flow rates, reaction coil length) affecting the determination were studied and optimized. Under the selected values, the analyte could be determined in the range of 0.1-12.0 mg L⁻¹ (r = 0.9997), at a sampling rate of 120 h⁻¹. The proposed assay was precise (s_r = 0.8% at 5.0 mg L⁻¹ Au(III), n = 12) and adequately sensitive with a 3σ limit of detection of 0.03 mg L⁻¹. The method was successfully applied to the analysis of jewel samples. The obtained results were favorably compared to flame atomic absorption spectrometry (FAAS) used as a reference method.     

Automatic microdistillation flow-injection system for the spectrophotometric determination of fluoride

An automatic flow-injection (FI) system including on-line separation by microdistillation and spectrophotometric detection has been developed for the determination of trace amounts of fluoride. This ion was separated from sample matrix by distillation in the presence of sulfuric and phosphoric acids, and was subsequently determined with spectrophotometry based on the mixed-ligand complex of lanthanum(III)-fluoride-alizarin complexone. The proposed FI system has high sampling frequency (20 samples h⁻¹), small sample size (600 μl) and the dynamic range of 0.05-15 mg l⁻¹ with relative standard deviations of below 1.2%. Interfering ions such as aluminum(III) and iron(III) was effectively eliminated. The method was successfully applied to the determination of fluoride in industrial drainage after water treatment.     

Determination of arsenic based on quenching of CdS quantum dots fluorescence using the gas-diffusion flow injection method

A sequential injection analysis system for determination of arsenic based on hydride generation and fluorescence quenching of mercaptoacetic acid capped cadmium sulfide quantum dots (CdS-MAA QDs) is described. The generated arsine diffused across the PTFE membrane in a gas-diffusion unit and subsequently interacted with CdS-MAA QDs. The parameters affecting the arsine generation and the fluorescence quenching of QDs were studied. Under the optimum conditions, it was observed that a increase in the concentration of As(III) corresponded well to a decrease in fluorescence intensity according to the Stern-Volmer relationship. The extent of quenching was dependent on the concentration of arsenic in the range of 0.08-3.20 mmol L⁻¹, with the detection limit of 0.07 mg L⁻¹. The precision (%RSD) from eight replicates of the determination of As(III) 1.0 mg L⁻¹ was found to be 1.4%. The proposed method was applied to the determination of arsenic in ground water samples with satisfactory recoveries.     

The development of sequential injection analysis coupled with lab-on-valve for copper determination

A sequential injection analysis (SIA) using lab-on-valve with air segmentation and spectrophotometric detection was designed for copper(II) determination. It is based on the reaction of copper(II) and 2-carboxy-2′-hydroxy-5′-sulfoformazyl benzene (Zincon) in a weak alkaline solution between the air zones. Beer's Law was obeyed over the range of 0.1-2.0 mg L⁻¹ copper(II) with a correlation coefficient 0.9985 and a slope of 0.2893 absorbance unit/mg L⁻¹. The relative standard deviation was 2.0% for a series of 10 measurements of 0.5 mg L⁻¹ copper(II) solution. The detection limit (3 S/N) and the limit of quantification (LOQ) were 0.05 and 0.17 mg L⁻¹ respectively. This method has been successfully applied to determination of copper(II) in wastewater with a sample throughput of 120 h⁻¹. The method is superior to the batchwise method in that it provides fully automation, rapidity, less reagents and sample consumption with little waste generation.     

Sequential injection methodology for carbon speciation in bathing waters

A sequential injection method (SIA) for carbon speciation in inland bathing waters was developed comprising, in a single manifold, the determination of dissolved inorganic carbon (DIC), free dissolved carbon dioxide (CO₂), total carbon (TC), dissolved organic carbon and alkalinity. The determination of DIC, CO₂ and TC was based on colour change of bromothymol blue (660 nm) after CO₂ diffusion through a hydrophobic membrane placed in a gas diffusion unit (GDU). For the DIC determination, an in-line acidification prior to the GDU was performed and, for the TC determination, an in-line UV photo-oxidation of the sample prior to GDU ensured the conversion of all carbon forms into CO₂. Dissolved organic carbon (DOC) was determined by subtracting the obtained DIC value from the TC obtained value. The determination of alkalinity was based on the spectrophotometric measurement of bromocresol green colour change (611 nm) after reaction with acetic acid. The developed SIA method enabled the determination of DIC (0.24–3.5 mg C L⁻¹), CO₂ (1.0–10 mg C L⁻¹), TC (0.50–4.0 mg C L⁻¹) and alkalinity (1.2–4.7 mg C L⁻¹ and 4.7–19 mg C L⁻¹) with limits of detection of: 9.5 μg C L⁻¹, 20 μg C L⁻¹, 0.21 mg C L⁻¹, 0.32 mg C L⁻¹, respectively. The SIA system was effectively applied to inland bathing waters and the results showed good agreement with reference procedures.     

Evaluation of alternate lines of Fe for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry

The usefulness of the secondary line at 252.744 nm and the approach of side pixel registration were evaluated for the development of a method for sequential multi-element determination of Cu, Fe, Mn and Zn in soil extracts by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). The influence of side pixel registration on the sensitivity and linearity was investigated by measuring at wings (248.325, 248.323, 248.321, 248.329, and 248.332 nm) of the main line for Fe at 248.327 nm. For the secondary line at 252.744 nm or side pixel registration at 248.325 nm, main lines for Cu (324.754 nm), Mn (279.482 nm) and Zn (213.875 nm), sample flow-rate of 5.0 mL min⁻¹ and calibration by matrix matching, analytical curves in the 0.2-1.0 mg L⁻¹ Cu, 1.0-20.0 mg L⁻¹ Fe, 0.2-2.0 mg L⁻¹ Mn, 0.1-1.0 mg L⁻¹ Zn ranges were obtained with linear correlations better than 0.998. The proposed method was applied to seven soil samples and two soil reference materials (IAC 277; IAC 280). Results were in agreement at a 95% confidence level (paired t-test) with reference values. Recoveries of analytes added to soil extracts containing 0.15 and 0.30 mg L⁻¹ Cu, 7.0 and 14 mg L⁻¹ Fe, 0.60 and 1.20 mg L⁻¹ Mn, 0.07 and 0.15 mg L⁻¹ Zn, varied within the 94-99, 92-98, 93-101, and 93-103% intervals, respectively. The relative standard deviations (n = 12) were 2.7% (Cu), 1.4% (Fe - 252.744 nm), 5.7% (Fe - 248.325 nm), 3.2% (Mn) and 2.8% (Zn) for an extract containing 0.35 mg L⁻¹ Cu, 14 mg L⁻¹ Fe, 1.1 mg L⁻¹ Mn and 0.12 mg L⁻¹ Zn. Detection limits were 5.4 μg L⁻¹ Cu, 55 μg L⁻¹ Fe (252.744 nm), 147 μg L⁻¹ Fe (248.325 nm), 3.0 μg L⁻¹ Mn and 4.2 μg L⁻¹ Zn.     

Determination of glucose using a coupled-enzymatic reaction with new fluoride selective optical sensing polymeric film coated in microtiter plate wells

The determination of glucose in beverages is demonstrated using newly developed fluoride selective optical sensing polymeric film that contains aluminum (III) octaethylporphyrin (Al[OEP]) ionophore and the chromoionophore ETH7075 cast at the bottom of wells of a 96-well polypropylene microtiter plate. The method uses a dual enzymatic reaction involving glucose oxidase enzyme (GOD) and horseradish peroxidase (HRP), along with an organofluoro-substrate (4-fluorophenol) as the source of fluoride ions. The concentration of fluoride ions after enzymatic reaction is directly proportional to the glucose level in the sample. The method has a detection limit of 0.8 mmol L⁻¹, a linear range of 0.9-40 mmol L⁻¹ and a sensitivity of 0.125 absorbance/decade of glucose concentration. Glucose levels in several beverage samples determined using the proposed method correlate well with a reference spectrophotometric enzyme method based on detection of hydrogen peroxide using bromopyrogallol red dye (BPR). The new method can also be used to determine H₂O₂ concentrations in the 0.1-50 mmol L⁻¹ range using a single enzymatic reaction involving H₂O₂ oxidation of 4-fluorophenol catalyzed by HRP. The methodology could potentially be used to detect a wide range of substrates for which selective oxidase enzymes exist (to generate H₂O₂), with the high throughput of simple microtiter plate detection scheme.     

Sensitive and ultra-fast determination of arsenic(III) by gas-diffusion flow injection analysis with chemiluminescence detection

A novel chemiluminescence gas-diffusion flow injection system for the determination of arsenic(III) in aqueous samples is described. The analytical procedure involves injection of arsenic(III) samples and standards into a 0.3 mol L⁻¹ hydrochloric acid carrier stream which is merged with a reagent stream containing 0.2% (w/v) sodium borohydride and 0.015 mol L⁻¹ sodium hydroxide. Arsine, generated in the combined carrier/reagent donor stream, diffuses across the hydrophobic Teflon membrane of the gas-diffusion cell into an argon acceptor stream and then reacts with ozone in the flow-through chemiluminescence measuring cell of the flow system. Under optimal conditions, the method is characterized by a wide linear calibration range from 0.6 μg L⁻¹ to 25 mg L⁻¹, a detection limit of 0.6 μg L⁻¹ and a sample throughput of 300 samples per hour at 25 mg L⁻¹ and 450 samples per hour at 25 μg L⁻¹.     

Sequential injection method for the direct spectrophotometric determination of bismuth in pharmaceutical products

A spectrophotometric method is reported for the determination of bismuth in pharmaceutical products using sequential injection analysis. Methylthymol blue (MTB) was used as a color forming reagent and the absorbance of the Bi(III)-MTB complex was monitored at 548 nm. The various chemical and physical variables that affected the reaction were studied. A linear calibration graph was obtained in the range 0.0-75.0 mg l⁻¹ Bi(III) at a sampling frequency of 72 h⁻¹. The reagent consumption was considerably reduced compared to conventional flow injection systems, as only 150 μl of MTB were consumed per run. The precision was very satisfactory (s_r=0.5%, at 50.0 mg l⁻¹ Bi(III), n=12) and the limit of detection, c_L, was 0.250 mg l⁻¹. The developed method was applied successfully to the analysis of various pharmaceutical products containing Bi(III). The relative errors e_r, were <1.5% in all cases and were evaluated by comparison of the obtained results with those found using atomic absorption spectrometry as the reference method.     

A flow injection procedure based on solenoid micro-pumps for spectrophotometric determination of free glycerol in biodiesel

A flow system designed with solenoid micro-pumps is proposed for fast and greener spectrophotometric determination of free glycerol in biodiesel. Glycerol was extracted from samples without using organic solvents. The determination involves glycerol oxidation by periodate, yielding formaldehyde followed by formation of the colored (3,5-diacetil-1,4-dihidrolutidine) product upon reaction with acetylacetone. The coefficient of variation, sampling rate and detection limit were estimated as 1.5% (20.0 mg L⁻¹ glycerol, n = 10), 34 h⁻¹, and 1.0 mg L⁻¹ (99.7% confidence level), respectively. A linear response was observed from 5 to 50 mg L⁻¹, with reagent consumption estimated as 345 μg of KIO₄ and 15 mg of acetylacetone per determination. The procedure was successfully applied to the analysis of biodiesel samples and the results agreed with the batch reference method at the 95% confidence level.     

Alternative method for measurement of albumin/creatinine ratio using spectrophotometric sequential injection analysis

A simple, automatic and practical system for successive determination of albumin and creatinine has been developed by combining sequential injection analysis (SIA) and highly sensitive dye-binding assays. Albumin detection was based on the increase in the absorbance due to complex formation between albumin and eosin Y in acidic media. The absorbance of the complex was monitored at 547 nm. For the creatinine assay, the concentration of creatinine was measured by reaction with alkaline picrate to form a colored product which absorbs at 500 nm. The influences of experimental variables such as effects of pH, reagent concentration, standard/sample volume and interferences were investigated. Under optimal conditions, the automated method showed linearity up to 20 mg L⁻¹ for albumin and 100 mg L⁻¹ for creatinine. The 3σ detection limits were 0.6 and 3.5 mg L⁻¹ for albumin and creatinine, respectively, and the relative standard deviations (n = 10) were 2.49% for 20 mg L⁻¹ albumin, and 3.14% for 20 mg L⁻¹ creatinine. Application of the proposed method to the direct analysis of urinary samples yielded results which agreed with those obtained from the Bradford protein assay and a creatinine enzymatic assay according to a paired t-test. The results obtained should be a step towards developing a fully automated and reliable analytical system for clinical research, which requires direct determination of albumin and creatinine and/or its ratios.     

New procedure of selected biogenic amines determination in wine samples by HPLC

A new procedure for determination of biogenic amines (BA): histamine, phenethylamine, tyramine and tryptamine, based on the derivatization reaction with 2-chloro-1,3-dinitro-5-(trifluoromethyl)-benzene (CNBF), is proposed. The amines derivatives with CNBF were isolated and characterized by X-ray crystallography and ¹H, ¹³C, ¹⁹F NMR spectroscopy in solution. The novelty of the procedure is based on the pure and well-characterized products of the amines derivatization reaction. The method was applied for the simultaneous analysis of the above mentioned biogenic amines in wine samples by the reversed phase-high performance liquid chromatography. The procedure revealed correlation coefficients (R²) between 0.9997 and 0.9999, and linear range: 0.10–9.00 mg L⁻¹ (histamine); 0.10–9.36 mg L^-1 (tyramine); 0.09–8.64 mg L⁻¹ (tryptamine) and 0.10–8.64 mg L⁻¹ (phenethylamine), whereas accuracy was 97%–102% (recovery test). Detection limit of biogenic amines in wine samples was 0.02–0.03 mg L⁻¹, whereas quantification limit ranged 0.05–0.10 mg L⁻¹. The variation coefficients for the analyzed amines ranged between 0.49% and 3.92%. Obtained BA derivatives enhanced separation the analytes on chromatograms due to the inhibition of hydrolysis reaction and the reduction of by-products formation.     

On-line preconcentration and speciation analysis of Cr(III) and Cr(VI) using baker's yeast cells immobilised on controlled pore glass

A study was undertaken to evaluate Saccharomyces cerevisiae as a substrate for the biosorption of Cr(III) and Cr(VI) aiming to the selective determination of these species in aqueous solutions. The yeast cells were covalently immobilised on controlled pore glass (CPG), packed in a minicolumn and incorporated in an on-line flow injection system. The effect of chemical and physical variables affecting the biosorption process was tested in order to select the optimal analytical conditions for the Cr retention by S. cerevisiae. Cr(III) was retained by the immobilised cells and Cr(VI) were retained by CPG. The speciation was possible by selective and sequential elution of Cr(III) with 0.05 mol L⁻¹ HCl and 2.0 mol L⁻¹ HNO₃ for Cr(VI). The influence of some concomitant ions up to 20 mg L⁻¹ was also tested. Quantitative determinations of Cr were carried out by means of inductively coupled plasma optical emission spectrometry (ICP OES). Preconcentration factors of 12 were achieved for Cr(III) and 5 for Cr(VI) when 1.7 mL of sample were processed reaching detection limits of 0.45 for Cr(III) and 1.5 μg L⁻¹ for Cr(VI). The speciation of inorganic Cr in different kinds of natural waters was performed following the proposed method. Spiked water samples were also analysed and the recoveries were in all cases between 81 and 103%.     

Application of manganese(IV) dioxide microcolumn for determination and speciation of nitrite and nitrate using a flow injection analysis-flame atomic absorption spectrometry system

A flow injection (FI) method with flame atomic absorption spectrometry (FAAS) detection was developed for the determination and speciation of nitrite and nitrate in foodstuffs and wastewaters. The method is based on the oxidation of nitrite to nitrate using a manganese(IV) dioxide oxidant microcolumn where the flow of the sample through the microcolumn reduces the MnO₂ solid phase reagent to Mn(II), which is measured by FAAS. The absorbance of Mn(II) are proportional to the concentration of nitrite in the samples. The injected sample volume was 400 μL with a sampling rate of analyses was 90 h⁻¹ with a relative standard deviation better than 1.0% in a repeatability study. Nitrate is reduced to nitrite in proposed FI-FAAS system using a copperized cadmium microcolumn and analyzed as nitrite. The calibration curves were linear up to 20 mg L⁻¹ and 30 mg L⁻¹ with a detection limit of 0.07 mg L⁻¹ and 0.14 mg L⁻¹ for nitrite and nitrate, respectively. The results exhibit no interference from the presence of large amounts of ions. The method was successfully applied to the speciation of nitrite and nitrate in spiked natural water, wastewater and foodstuff samples. The precision and accuracy of the proposed method were comparable to those of the reference spectrophotometric method.     

Non-chromatographic speciation of toxic arsenic in fish

A rapid, sensitive and economic method has been developed for the direct determination of toxic species of arsenic present in fish and mussel samples. As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined by hydride generation-atomic fluorescence spectrometry using a series of proportional equations without the need of a chromatographic previous separation. The method is based on the extraction of arsenic species from fish through sonication with HNO₃ 3 mol l⁻¹ and 0.1% (m/v) Triton and washing of the solid phase with 0.1% (m/v) EDTA, followed by direct measurement of the corresponding hydrides in four different experimental conditions. The limit of detection of the method was 0.62 ng g⁻¹ for As(III), 2.1 ng g⁻¹ for As(V), 1.8 ng g⁻¹ for MMA and 5.4 ng g⁻¹ for DMA, in all cases expressed in terms of sample dry weight. The mean relative standard deviation values (R.S.D.) in actual sample analysis were: 6.8% for As(III), 10.3% for As(V), 8.5% for MMA and 7.4% for DMA at concentration levels from 0.08 mg kg⁻¹ As(III) to 1.3 mg kg⁻¹ DMA. Recovery studies provided percentages greater than 93% for all species in spiked samples. The analysis of SRM DORM-2 and CRM 627 certified materials evidenced that the method is suitable for the accurate determination of arsenic species in fish.