Determination of As, Cd, Pb and Se in DORM-1 dogfish muscle reference material using alkaline solubilization and electrothermal atomic absorption spectrometry with Ir+Rh as permanent modifiers or Pd+Mg in solution

In this work, tetramethylammonium hydroxide (TMAH) was used to solubilize the DORM-1 dogfish muscle certified reference material as a model substance for the determination of As, Cd, Pb and Se by electrothermal atomic absorption spectrometry (ET AAS). The sample was mixed with a small amount of TMAH and heated to 60 °C for 10 min in a water bath. After dissolution, As and Se were determined using palladium and magnesium nitrates as a chemical modifier added in solution. For Cd and Pb, best results were obtained with a mixture of 250 μg of each of iridium and rhodium as permanent modifiers. In both cases, the calibration was performed with aqueous solutions in 0.2% v/v HNO₃. The temperature program for each analyte was optimized using pyrolysis and atomization curves established with the fish reference material. The detection limits in dry samples and the characteristic mass values were: Cd 0.005 μg g⁻¹ and 0.9 pg; Pb 0.04 μg g⁻¹ and 7.6 pg; As 0.4 μg g⁻¹ and 13 pg and Se 0.6 μg g⁻¹ and 20 pg, respectively. Results from the determination of these elements in the DORM-1 certified fish reference material were within the 95% confidence interval of the certified values.     

Effect of irradiation on anti-nutrients (total phenolics, tannins and phytate) in Brazilian beans

The Brazilian bean varieties Phaseolus vulgaris L. var. Carioca and Vigna unguiculata (L.) Walp var. Macaçar were irradiated with doses of 0.5, 1.0, 2.5, 5.0 and 10 kGy and subsequently stored at ambient temperature for 6 months. The anti-nutrients phenolic compounds, tannins and phytate were determined to be 0.48 mg g⁻¹ dry basis, 1.8 mg g⁻¹ dry basis and 13.5 μmol g⁻¹ dry basis in the raw non-irradiated Carioca beans and 0.30 mg g⁻¹ dry basis, 0.42 mg g⁻¹ dry basis and 7.5 μmol g⁻¹ dry basis in the raw non-irradiated Macaçar beans. After soaking and cooking a higher content of phenolic compounds and a lower phytate content was observed in both bean varieties. Tannin content was not affected by soaking and cooking of Carioca beans, but higher after soaking and cooking of Macaçar beans. Using radiation doses relevant for food did not effect the content of the anti-nutrients under investigation in both bean varieties.     

Determination of pentachlorophenol in wastewater irrigated soils and incubated earthworms

The analyses of low pentachlorophenol (PCP) in soils and earthworms require a sensitive and reliable analytical method. In this paper, several derivatization methods and extraction solvents were compared systematically. The derivatization reagents included acetic anhydride, 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr) and diazomethane. Hexane, acetone, hexane–acetone (1:1), dichloromethane and methanol were used as the extraction solvents. PFBBr derivatization showed the highest sensitivity. The derivatization parameters of PFBBr including the amount of PFBBr, the power and irradiation time of microwave were optimized. As a result, 200 μl of PFBBr (10%) at 150 W of microwave oven for 30 min achieved the best result. The PFBBr derivatization method had the detection limit of 0.07 μg l⁻¹ of PCP. Extraction by a mixture of hexane and acetone (1:1) showed the best recoveries. The recommended method was used to determine the low PCP in soils irrigated by wastewater and earthworms incubated in the corresponding soils. The concentrations of PCP in soils were in the range of 1.38–179 ng g⁻¹, while those in earthworms were 11.2–262 ng g⁻¹. The recoveries of the surrogate standard (trichlorophenol) ranged from 81.1% to 107%, demonstrating the merit of the method.     

Optimisation of sample treatment for arsenic speciation in alga samples by focussed sonication and ultrafiltration

A procedure for arsenic species fractionation in alga samples (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) by extraction is described. Several parameters were tested in order to evaluate the extraction efficiency of the process: extraction medium, nature and concentration (tris(hydroxymethyl)aminomethane, phosphoric acid, deionised water and water/methanol mixtures), extraction time and physical treatment (magnetic stirring, ultrasonic bath and ultrasonic focussed probe). The extraction yield of arsenic under the different conditions was evaluated by determining the total arsenic content in the extracts by ICP-AES. Arsenic compounds were extracted in 5 mL of water by focussed sonication for 30 s and subsequent centrifugation at 14,000 × g for 10 min. The process was repeated three times. Extraction studies show that soluble arsenic compounds account for about 65% of total arsenic.

An ultrafiltration process was used as a clean-up method for chromatographic analysis, and also allowed us to determine the extracted arsenic fraction with a molecular weight lower than 10 kDa, which accounts for about 100% for all samples analysed.

Speciation studies were carried out by HPLC–ICP-AES. Arsenic species were separated on a Hamilton PRP-X100 column with 17 mM phosphate buffer at pH 5.5 and 1.0 mL min⁻¹ flow rate. The chromatographic method allowed us to separate the species As(III), As(V), MMA and DMA in less than 13 min, with detection limits of about 20 ng of arsenic per species, for a sample injection volume of 100 μL. The chromatographic analysis allowed us to identify As(V) in Hizikia (46 ± 2 μg g⁻¹), Sargassum (38 ± 2 μg g⁻¹) and Chlorella (9 ± 1 μg g⁻¹) samples. The species DMA was also found in Chlorella alga (13 ± 1 μg g⁻¹). However, in Laminaria alga only an unknown arsenic species was detected, which eluted in the dead volume.     

Investigation of equilibration and uncertainty contributions for the determination of inorganic mercury and methylmercury by isotope dilution inductively coupled plasma mass spectrometry

The mass fractions of Hg and methylmercury, in two certified reference materials, NIST2710 and DORM-2, have been determined by total and species-specific isotope dilution analysis (IDA), respectively, and uncertainty budgets for each analysis calculated. The mass fraction of Hg in NIST2710 was determined by ID using multicollector sector field inductively coupled plasma mass spectrometry (MC-SF-ICP-MS) whilst the mass fraction of methylmercury in DORM-2 was determined using HPLC coupled with quadrupole ICP-MS.

The extent of equilibration between the spike and the particulate bound mercury compounds was studied temporally by monitoring the ²⁰⁰Hg:¹⁹⁹Hg isotope amount ratio and by determining the total amount of Hg in the liquid phase. For the NIST2710 complete equilibration was only achieved when concentrated HNO₃ in combination with a microwave digestion was employed, and good agreement between the found (31.7±4.0 μg g⁻¹, expanded uncertainty k=2) and certified (32.6±1.8 μg g⁻¹) values was obtained. For DORM-2 complete equilibration of methylmercury between the liquid and solid phases was achieved when using 50:50 H₂O:CH₃OH (v/v) and 0.01% 2-mercaptoethanol as the solvent. Even though only 50% of the analyte was extracted into the liquid phase, complete equilibration was achieved, hence, the found methylmercury mass fraction (4.25±0.47 μg g⁻¹, expanded uncertainty k=2) was in good agreement with the certified value (4.47±0.32 μg g⁻¹).     

Determination of arsenic, lead, selenium and tin in sediments by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry using Ru as permanent modifier and NaCl as a carrier

A procedure for the determination of As, Pb, Se and Sn in sediment slurries by electrothermal vaporization inductively coupled plasma mass spectrometry is proposed. The slurry, 1 mg ml⁻¹, is prepared by mixing the sample ground to a particle size 50 μm with 5% v/v nitric and 1% v/v hydrofluoric acids in an ultrasonic bath. The slurry was homogenized with a constant flow of argon in the autosampler cup, just before transferring an aliquot to the graphite furnace. The tube was treated with Ru as a permanent modifier, and an optimized mass of 1 μg of NaCl was added as a physical carrier. The pyrolysis temperature was optimized through pyrolysis curves, and a compromised temperature of 800 °C was used; the vaporization temperature was 2300 °C. The effect of different acid concentrations in the slurry on the analyte signal intensities was also evaluated. The accuracy of the method was assured by the analysis of certified reference sediments MESS-2, PACS-2 and HISS-1 from the National Research Council Canada, SRM 2704 and SRM 1646a from the National Institute of Standards and Technology and RS-4 from a round robin test, using external calibration with aqueous standards prepared in the same medium as the slurries. The obtained concentrations were in agreement with the certified values according to the Student's t-test for a confidence level of 95%. The detection limits in the samples were: 0.17 μg g⁻¹ for As; 0.3 μg g⁻¹ for Pb; 0.05 μg g⁻¹ for Se and 0.28 μg g⁻¹ for Sn. The precision found for the different sediment samples, expressed as R.S.D. was 1–8% for As, 2–9% for Pb, 6–12% for Se and 3–8% for Sn (n=5).     

Preconcentration and speciation of chromium in a sequential injection system incorporating dual mini-columns coupled with electrothermal atomic absorption spectrometry

A procedure for chromium preconcentration and speciation with a dual mini-column sequential injection system coupled with electrothermal atomic absorption spectrometry (ETAAS) was developed. At pH 6, the sample solution was firstly aspirated to flow through a Chlorella vulgaris cell mini-column on which the Cr(III) was retained. The effluent was afterwards directed to flow through a 717 anion exchange resin mini-column accompanied by the retention of Cr(VI). Thereafter, Cr(III) and Cr(VI) were eluted by 0.04 mol L^− 1 and 1.0 mol L^− 1 nitric acid, respectively, and the eluates were quantified with ETAAS. Chemical and flow variables governing the performance of the system were investigated. By using a sampling volume of 600 µL, sorption efficiencies of 99.7% for Cr(III) and 99% for Cr(VI) were achieved along with enrichment factors of 10.5 for Cr(III) and 11.6 for Cr(VI), within linear ranges of 0.1–2.5 µg L^− 1 for Cr(III) and 0.12–2.0 µg L^− 1 for Cr(VI). Detection limits of 0.02 µg L^− 1 for Cr(III) and 0.03 µg L^− 1 for Cr(VI) along with RSD values of 1.9% for Cr(III) and 2.5% for Cr(VI) (1.0 µg L^− 1, n = 11) were obtained. The procedure was validated by analyzing a certified reference material of GBW08608 and further demonstrated by chromium speciation in river and tap water samples.     

Determination of chlorophenoxy acid herbicides and their esters in soil by capillary high performance liquid chromatography with ultraviolet detection, using large volume injection and temperature gradient

A simple method for the simultaneous determination of chlorophenoxy acid herbicides and their esters in soil is presented. Compounds studied are: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB), 2,4-dichlorophenoxyacetic-1-butyl ester (2,4-D-1-butyl ester), and 2,4-dichlorophenoxyacetic-1-methyl ester (2,4-D-1-methyl ester).

The chromatographic analysis was carried out by HPLC, after ultrasonic extraction, on a C₁₈ packed capillary column with temperature gradient, large injection volumes and UV detection at 232 nm. Samples were spiked with amounts between 2.5 and 6.0 μg g⁻¹ of each herbicide; recoveries obtained were between 72 and 97% (n=3 for each spiked level) and detection limits were between 0.3 and 0.5 μg g⁻¹.

Application of this procedure to the analysis of herbicides in ester and acid forms showed the effectiveness of the methodology proposed.     

Atomic absorption spectrophotometric determination of trace copper in waters, aluminium foil and tea samples after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

An atomic absorption spectrophotometric method for the determination of trace copper after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been developed. This chelate is adsorbed on the adsorbent in the pH range 1–8. The copper chelate is eluted with 5 ml of 0.1 mol l⁻¹ potassium cyanide and determined by flame atomic absorption spectrometry (FAAS). The selectivity of the proposed procedure was also evaluated. Results show that iron(III), zinc(II), manganese(II) and cobalt(II) at the 50 μg l⁻¹ level and sodium(I), potassium(I), magnesium(II), calcium(II) and aluminium(III) at the 1000 μg l⁻¹ level did not interfere. A high enrichment factor, 200, was obtained. The detection limit (3σ) of copper was 0.34 μg l⁻¹. The precision of the method, evaluated by seven replicate analyses of solutions containing 5 μg of copper was satisfactory and the relative standard deviation was 1.7%. The adsorption of copper onto Ambersorb 572 can formally be described by a Langmuir equation with a maximum adsorption capacity of 14.3 mg g⁻¹ and a binding constant of 0.00444 l mg⁻¹. The accuracy of the method is confirmed by analysing tomatoes leaves (NIST 1573a) and lead base alloy (NBS 53e). The results demonstrated good agreement with the certified values. This procedure was applied to the determination of copper in waters (tap, river and thermal waters), aluminium foil and tea samples.     

A liquid chromatographic method, with fluorometric detection, for the determination of enrofloxacin and ciprofloxacin in plasma and endometrial tissue of mares

The aim of this work was to develop and validate a simple and sensitive analytical method for determining enrofloxacin (EFX) and ciprofloxacin (CFX) in equine plasma and endometrial tissue samples, as a precursor to conducting pharmacokinetic/pharmacodynamic studies on equine endometritis This was achieved in the form of a liquid chromatographic procedure, with fluorometric detection, which also gave good separation of other fluoroquinolones including marbofloxacin (MFX), danofloxacin (DFX) and ofloxacin (OFX). Analytes were separated on a C₁₈ reversed phase column using an acidified mobile phase. The exact composition of the mobile phase differed for plasma (16% acetonitrile:methanol [13:1,v/v] 84% water containing 0.4% triethylamine and 0.4% phosphoric acid [35%]) and endometrial tissue (14% acetonitrile, 86% water, without methanol) samples. EFX and CFX were both detected at excitation and emission wavelengths of 294 and 500 nm, respectively. Prior to chromatography, EFX and CFX were purified by solid phase extraction from plasma, and a combination of solvent/solid phase extraction from endometrial tissue.

Mean absolute recoveries for EFX and CFX from plasma were 94.1 and 78.0%, respectively, and from endometrial tissue, 78.0 and 57.8%, respectively, with a percentage residual standard deviation (%R.S.D.) <10% in each case. Mean relative recoveries for EFX and CFX from plasma were 91.3 and 119.4%, respectively, and from endometrial tissue, 80.2 and 108.0%, respectively, with a %R.S.D. <20% in each case.

Standard curves constructed using blank plasma and endometrial tissue samples, spiked with authentic EFX and CFX in the ranges 0.005–10.0 μg mL⁻¹ and 0.05–10.0 μg g⁻¹, respectively, all showed acceptable linearity with correlation coefficients, r² ≥ 0.977. Mean intra- and inter-day precision (expressed as %R.S.D.) was <6 and <13%, respectively, with an associated accuracy (expressed as percentage relative error, %R.E.) of <20% for both analytes in both matrices. Acceptable precision and accuracy was also demonstrated at the pre-assigned LOQs of 0.005 μg mL⁻¹ for both EFX and CFX in plasma, and 0.05 μg g⁻¹ for both drugs in endometrial tissue. EFX and CFX were stable in both plasma and endometrial tissue for at least 60 days at −20 °C.     

Analytical procedures for improved trace element detection limits in polar ice from Arctic Canada using ICP-SMS

Analytical procedures have been developed for the reliable determination of 19 trace elements (Ag, Al, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mn, Pb, Rb, Sb, Sc, Sr, Tl, U, V, Zn) in ice samples at pg g⁻¹ and fg g⁻¹ concentrations using ICP-sector field mass spectrometry (ICP-SMS). Concentrations of most elements in the high purity water and doubly distilled HNO₃ employed were distinctly lower than previously reported values. The accuracy of the results was carefully evaluated using the certified water reference material SLRS-4. Contributions of unwanted trace elements due to acidification of the ice samples (0.5% HNO₃) to the total element budget amounted to only 0.001 pg g⁻¹ for Bi, 0.34 pg g⁻¹ for Cr, 0.2 pg g⁻¹ for Fe, 0.004 pg g⁻¹ for Pb, 0.00015 pg g⁻¹ for U and 0.0025 pg g⁻¹ for V: compared to the concentrations of the metals in ice these are negligible. The use of a detergent (0.05%) in the rinsing solution (0.5% HNO₃), helped to reduce memory effects by 59–98%, depending on the element considered; this resulted in shorter washing times between samples (i.e. 1 min) and improved analysis time. Adopting strict clean room procedures, the detection limit for Pb (0.06 pg g⁻¹) is a factor of ten lower than the current state-of-the-art. Compared to previous studies, the improved LODs obtained here for other trace elements amount to 2× (Ag), 4× (Sb), 5× (Ba), 6× (Cu, Mn, U), 9× (Bi), 13× (Cd), 18× (Fe) and 21× (V). The developed analytical protocols were successfully applied to the determination of selected trace elements in age-dated ice samples from the Canadian High Arctic. The toxic trace element Tl (median: 0.16 pg g⁻¹; range: 0.03–1.32 pg g⁻¹) and the lithogenic reference element Sc (0.53 pg g⁻¹; 0.06–2.9 pg g⁻¹) have been determined in a polar ice core for the first time.     

Multi-elemental analysis of non-food packaging materials by inductively coupled plasma-time of flight-mass spectrometry

Commercial non-food packaging materials of four different matrices (paper, low density polyethylene (LDPE), polyethylene-polypropylene (PE-PP) and high density polyethylene (HDPE)) were examined for the content of Cr, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, Hg, Tl, Pb and U. The examined samples (0.17–0.35 g) were digested in HNO₃ and H₂O₂ (papers, LDPE and PE-PP) and in HNO₃, H₂SO₄ and H₂O₂ (HDPE) using microwave assisted high pressure system. The inductively coupled plasma-time of flight-mass spectrometry (ICP-TOFMS) has been employed as the detection technique. All measurements were carried out using internal standardization. Yttrium and rhodium (50 ng g⁻¹) were used as internal standards. The detection and quantification limits obtained were in the range of 0.005 ng g⁻¹ (⁵²Cr) to 0.51 ng g⁻¹ (⁶⁶Zn) and 0.015 μg g⁻¹ (⁵²Cr) to 2.02 μg g⁻¹ (⁶⁶Zn) of dry mass, respectively. The evaluated contents (mg kg⁻¹) of particular elements in the examined materials were as follows: 0.22–219; <1.05–9.03; 1.25–112; <2.02–449; <0.98–<1.30; <0.36–2.06; <0.29–113; <0.22–44.1; <0.06–57.4; <0.66–<0.88; <0.08–0.24; <0.13–1222 and <0.08–0.44 for Cr, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, Hg, Tl, Pb and U, respectively.     

Analytical procedures for the determination of selected major (Al, Ca, Fe, K, Mg, Na, and Ti) and trace (Li, Mn, Sr, and Zn) elements in peat and plant samples using inductively coupled plasma-optical emission spectrometry

A simple, robust and reliable analytical procedure for the determination of Al, Ca, Fe, K, Li, Mg, Mn, Na, Sr, Ti, and Zn in peat and plant materials by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed. A microwave heated high pressure autoclave was used to digest powdered sample aliquots (approximately 200 mg) with different acid mixtures including nitric acid (HNO₃), tetrafluoroboric acid (HBF₄) and hydrogen peroxide (H₂O₂). The optimized acid mixture for digestion of plant and peat samples consisted of 3 mL HNO₃ and 0.1 mL HBF₄, in addition to H₂O₂ which was sub-boiled into the PTFE digestion tubes during heating of the autoclave. Using HNO₃ alone, recoveries of Al and Ti were too low by 40 and 160%, respectively, because HNO₃ could not fully liberate the analytes of interest from the silicate fraction of the plant and peat matrix. However, for all other elements (such as Mn, Sr, and Zn), the use of HBF₄ was less critical. The accuracy of the analytical procedure developed was evaluated with peat and plant reference materials of different origin and composition. The ICP-OES instrument was optimized using solutions of plant reference materials considering RF power, nebulizer pressure, auxiliary gas flow and rinse time. Scandium was used as an online internal standard (IS) as it provided accurate results and showed less than 3% drift in sensitivity over time which was lower compared to other potential IS such as Rh (20%) and In (6%). The combination of most sensitive and less sensitive wavelengths allowed to obtain low detection limits and highest possible dynamic range. The achieved procedure detection limits ranged from 0.05 μg g⁻¹ (Li) to 15 μg g⁻¹ (Ca) and allowed a precise quantification of all elements. Comparative X-ray fluorescence spectrometric measurements of solid peat and plant samples generally agreed well with results obtained by digestion/ICP-OES. To overcome interferences caused by Na, K, and Li, a solution of 10 μg g⁻¹ CsCl₂ was successfully used as an ionization buffer. The good agreement between the found and certified concentrations in plant and peat reference materials indicates that the developed analytical procedure is well suited for further studies on the fate of major elements in plant and peat matrices.     

Supported liquid membranes for the determination of vanillin in food samples with amperometric detection

A supported liquid membrane system has been developed for the extraction of vanillin from food samples. A porous PTFE membrane is impregnated with an organic solvent, which forms a barrier between two aqueous phases. The analyte is extracted from a donor phase into the hydrophobic membrane and then back extracted into a second aqueous solution, the acceptor. The determination (100–1400 μg ml⁻¹ vanillin) was performed using a PVC-graphite composite electrode versus Ag/AgCl/3MKCl at +0.850 V placed in a wall-jet flow cell as amperometric detector. The solid sample is directly placed in the membrane unit without any treatment, and the analyte was extracted from the sample, passes through the membrane and conduced to the flow cell by the acceptor stream. The limit of detection (3σ) was 44 μg ml⁻¹. The method was applied to the determination of vanillin (9–606 μg g⁻¹) in food samples.     

Analysis of acrylamide in coffee and dietary exposure to acrylamide from coffee

An analytical method for analysing acrylamide in coffee was validated. The analysis of prepared coffee includes a comprehensive clean-up using multimode solid-phase extraction (SPE) by automatic SPE equipment and detection by liquid chromatography tandem mass spectrometry using electrospray in the positive mode. The recoveries of acrylamide in ready-to-drink coffee spiked with 5 and 10 μg l⁻¹ were 96±14% and 100±8%, respectively. Within laboratory reproducibility for the same spiking levels were 14% and 9%, respectively. Coffee samples (n = 25) prepared twice by coffee machines and twice by a French Press Cafetière coffee maker contained 8±3 μg l⁻¹ and 9±3 μg l⁻¹ acrylamide. Five ready-to-drink instant coffee prepared twice contained 8±2 μg l⁻¹. Hence, the results do not show significant differences in the acrylamide contents in ready-to-drink coffee prepared by coffee machine, French Press or from instant coffee. Medium roasted coffee contained more acrylamide (10 μg l⁻¹) than dark roasted coffee (5 μg l⁻¹). Males aged 35–45 years, drinking on average 1.1 l coffee per day are exposed to the highest doses of acrylamide from coffee. The dietary intake of acrylamide from coffee comprises, on an average, 10 μg day⁻¹ for males and 9 μg day⁻¹ for females aged 35–45 years. Probabilistic modelling of the exposure of Danish consumers (all adults) to acrylamide from coffee shows a mean exposure of 6.5 μg day⁻¹ and a 95 percentile of 18 μg day⁻¹.     

Determination of mercury in soils and sediments by graphite furnace atomic absorption spectrometry with slurry sampling

A graphite furnace atomic absorption spectrometric procedure for the determination of mercury is presented, in which the samples are suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4% m/v) and potassium permanganate (3%) are incorporated, in the order specified, and aliquots are directly introduced into the graphite furnace. A fast heating programme with no conventional pyrolysis step is used. The detection limit for mercury in a 125 mg ml⁻¹ suspension is 0.1 μg g⁻¹. Calibration is performed by using aqueous standards. The reliability of the procedure is proved by analysing certified reference materials.     

8-Hydroxyquinoline anchored to silica gel via new moderate size linker: synthesis and applications as a metal ion collector for their flame atomic absorption spectrometric determination

The silica gel modified with (3-aminopropyl-triethoxysilane) was reacted with 5-formyl-8-hydroxyquinoline (FHOQ_x) to anchor 8-quinolinol ligand on the silica gel. It was characterised with cross polarisation magic angle spinning (CPMAS) NMR and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and used for the preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry. The surface area of the modified silica gel has been found to be 227 m² g⁻¹ and the two pKa values as 3.8 and 8.0. The optimum pH ranges for quantitative sorption are 4.0–7.0, 4.5–7.0, 3.0–6.0, 5.0–8.0, 5.0–8.0, 5.0–8.0 and 4.0–7.0 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 2.5 mol l⁻¹ HCl or HNO₃. The sorption capacity for these metal ions is in range of 92–448.0 μmol g⁻¹ and follows the order Cd3, NaCl, NaBr, Na₂SO₄ and Na₃PO₄, glycine, sodium citrate, EDTA, humic acid and cations Ca(II), Mg(II), Mn(II) and Cr(III) in the sorption of all the seven metal ions are reported. The preconcentration factors are 150, 250, 200, 300, 250, 300 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively and t_1/2 values <1 min except for Ni. The 95% extraction by batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than sorption capacity. In river water samples all these metal ions were enriched with the present ligand anchored silica gel and determined with flame atomic absorption spectrometer (R.S.D.≤6.4%). Cobalt contents of pharmaceutical samples (vitamin tablet) were preconcentrated with the present chelating silica gel and estimated by flame AAS, with R.S.D.1.4%. The results are in the good agreement with the certified value, 1.99 μg g⁻¹ of the tablets. Iron and copper in certified reference materials (synthetic) SLRS-4 and SLEW-3 have been enriched with the modified silica gel and estimated with R.S.D.<5%.     

Determination of arsenic in gold by flow injection inductively coupled plasma mass spectrometry with matrix removal by reductive precipitation

Arsenic was determined in gold by flow injection hydride generation inductively coupled plasma-mass spectrometry following a batch mode reductive precipitation removal of the interfering gold matrix. A solution of potassium iodide, L-ascorbic acid, and hydrochloric acid was used as the reluctant. The recovery of gold by precipitation and filtration was 99 ± 3%. The detection limit for arsenic in gold was 55 ng g⁻¹ in the solid. The concentration of arsenic that was determined in the Royal Canadian Mint gold sample FAU-10 was 29.7 μg g⁻¹ in the solid; this value was indistinguishable, with 95% confidence, from values determined at the Royal Canadian Mint by graphite furnace atomic absorption spectrometry and by inductively coupled plasma-mass spectrometry. The standard deviation for four replicate determinations of the arsenic in FAU-10 was 0.972 μg g⁻¹ in the solid.     

Titanium as a chemical modifier for the determination of cobalt in marine sediments

The determination of cobalt in marine sediments by electrothermal atomic absorption spectrometry was studied using no modifier and magnesium and titanium as modifiers. Titanium is one of the major sediment constituents, which widely affects the cobalt determination and it was studied as a chemical modifier since it was the only concomitant that increased the cobalt signal in the concentration range usually found in sediments. The performance of Mg and Ti as chemical modifiers was compared relative to maximum pyrolysis and atomization temperatures, linear calibration range, sensitivity and matrix effects. The pyrolysis curves showed that the analyte could be stabilized up to 1400 °C when either Ti or Mg(NO₃)₂ was present, while only 1000 °C could be used in the absence of a modifier. The optimum atomization temperature was 2500 °C in all cases. Analytical curves were compared using no modifier, 5 μg Ti and 100 μg Mg(NO₃)₂ as modifiers, and the linear range found was up to approximately 4 ng Co whether a modifier was used or not. With Ti as a chemical modifier, analytical curves for cobalt in aqueous solution and in a synthetic matrix resulted in the same sensitivity (m₀=55 pg), whereas the use of Mg led to characteristic mass values of 59 and 72 pg in aqueous solution and in a synthetic matrix, respectively, showing some matrix effect. The detection limits (3σ, n=10) were 0.4 μg g⁻¹ using no modifier and 0.3 μg g⁻¹ with Ti as a modifier in the original matrix. A reference estuarine sediment NIST 1646 with a non-certified content of 10.5 μg g⁻¹ Co was analyzed and the found value of 10.9±2.4 μg g⁻¹, (n=3), using Ti as chemical modifier and calibration against aqueous standards, was in good agreement with the recommended value.     

Determination of phenols in water by on-line solid-phase disk extraction and liquid chromatography with electrochemical detection

Poly(styrene-divinylbenzene) (PS-DVB) membrane extraction disks were used as sorbents for the on-line solid phase extraction of 13 phenols (nitro and chlorophenols) in river and tap waters. Determination was performed by liquid chromatography with electrochemical detection (LC-ED). An acetate buffer-acetonitrile-methanol mixture as mobile phase and amperometric detection at +1100 mV were used. High water volumes, up to 250 ml, can be preconcentrated without loss of phenols (recoveries between 80% and 100%) except for the more polar ones. Moreover, detection limits between 0.01 and 0.1 μg l⁻¹ in tap water and between 0.1 and 1.0 μg⁻¹ in river water were obtained. The method has been applied to the analysis of two river water samples.