SRM 1643e Research Articles

Ligandless cloud point extraction for trace nickel determination in water samples by flame atomic absorption spectrometry

A very simple and ligandless cloud point extraction (CPE) methodology has been developed for the preconcentration of trace amounts of nickel as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The method is based on the extraction of nickel at pH 10 by using non-ionic surfactant polyethyleneglycol mono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Several variables affecting the extraction efficiency were investigated and optimized. The limit of detection (LOD) and limit of quantification (LOQ) values of nickel for the preconcentration of 50 mL of aqueous solution were 0.5 µg L-1 and 1.6 µg L-1, respectively. The relative standard deviation (RSD) for six replicate determinations at 50 and 80 µg L-1 of Ni were 2.67% and 1.97%, respectively. The calibration graph using the preconcentration system for nickel was linear with a correlation coefficient r = 0.9941. To validate the proposed method a standard reference material NIST SRM 1643e (trace elements in water) was analyzed and the result was in good agreement with the certified value. The proposed method was successfully applied to determination of trace amounts of nickel in water samples

Open-channel chip-based solid-phase extraction combined with inductively coupled plasma-mass spectrometry for online determination of trace elements in volume-limited saline samples

In this study, we used an automated online chip-based solid-phase extraction (SPE)–inductively coupled plasma-mass spectrometry (ICP-MS) system for analyzing trace elements in small-volume saline samples (∼15 μL). The proposed method involved the adsorption of trace metal ions in the interior of a functionalized poly(methyl methacrylate) (PMMA) channel in order to separate these ions from saline matrices. The adsorption of transition metal ions was presumably dominated by the surface complexation between the carboxylate moieties in the interior of the PMMA channel and the metal ions, which facilitated the formation of metal–carboxylate complexes. The components of the proposed online analytical system used for the simultaneous detection of multiple trace metals in saline samples involved microdialysis (MD) sampling, an established chip-based SPE procedure, and ICP-MS. The SPE–ICP-MS hyphenated system was optimized, and then, the analytical reliability of this system was further confirmed by using it to analyze the certified reference materials—SRM 2670 (human urine) and SRM 1643e (artificial saline water). The satisfactory analytical results indicated that the proposed on-chip SPE device could be readily used as an interface for coupling the MD probe with the ICP-MS system. The dramatically reduced consumption of chemicals and “hands-on” manipulations enabled the realization of a simplified and relatively clean procedure with extremely low detection limits in the range of 5.86–76.91 ng L −1 for detecting Mn, Co, Ni, Cu, and Pb in 15-μL samples by ICP-MS. The effectiveness of an online MD–chip-based SPE–ICP-MS technique for continuous monitoring of trace elements in a simulated biological system was also demonstrated. To the best of our knowledge, this is the first paper to report the direct exploitation of a PMMA chip as an SPE adsorbent for online sample pretreatment and trace metal preconcentration prior to ICP-MS measurement.

Preconcentration of trace elements from water samples on a minicolumn of yeast (Yamadazyma spartinae) immobilized TiO2 nanoparticles for determination by ICP-AES

A trace element preconcentration procedure is described utilizing a minicolumn of yeast (Yamadazyma spartinae) immobilized TiO2 nanoparticles for determination of Cr, Cu, Fe, Mn, Ni and Zn from water samples by inductively coupled plasma atomic emission spectrometry. The elements were quantitatively retained on the column between pH 6 and 8. Elution was made with 5% (v/v) HNO3 solution. Recoveries ranged from 98±2 (Cr) to 100±4 (Zn) for preconcentration of 50mL multielement solution (50μgL−1). The column made up of 100mg sorbent (yeast immobilized TiO2 NP) offers a capacity to preconcentrate up to 500mL of sample solution to achieve an enrichment factor of 250 with 2mL of 5% (v/v) HNO3 eluent. The detection limits obtained from preconcentration of 50mL blank solutions (5%, v/v, HNO3, n=11) were 0.17, 0.45, 0.25, 0.15, 0.33 and 0.10μgL−1 for Cr, Cu, Fe, Mn, Ni and Zn, respectively. Relative standard deviation (RSD) for five replicate analyses was better than 5%. The retention of the elements was not affected from up to 500μgL−1 Na+ and K+ (as chlorides), 100μgL−1 Ca2+ (as nitrate) and 50μgL−1 Mg2+ (as sulfate). The method was validated by analysis of freshwater standard reference material (SRM 1643e) and applied to the determination of the elements from tap water and lake water samples.

Determination of Germanium and Tin and Inorganic Tin Species by Hydride Generation in Situ Trapping Flame Atomic Absorption Spectrometry

The analytical performances of a coupled hydride generation, integrated atom trap (HG-IAT) atomizer flame atomic absorption spectrometry (FAAS) system were evaluated for determination of Ge and Sn and inorganic tin species in environmental samples. Germanium and tin hydrides were atomized in air-acetylene flame-heated IAT. A new design of HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube) permitting construction of an “integrated trap” was investigated. For the estimation of Sn(II) and Sn(IV) concentrations in samples, the difference between the analytical sensitivities of the absorbance singnals obtained for tin hydride without and with previous treatment of samples with L-cysteine could be used. The concentration of Sn(IV) was calculated by the difference between total Sn(tot) and Sn(II). An improvement in limit of detection was achieved compared with that obtained using any of the aforementioned atom trapping techniques separately. The concentration limits of detection were 25 and 8 ng mL−1 for Ge and Sn, respectively. For a 2 min in situ preconcentration time, sensitivity enhancement, compared to FAAS, were 10 and 14 folds for Ge and Sn, respectively, using hydride generation atom trapping technique. The sensitivity can be further improved by increasing the collection time. The relative standard deviations (RSDs) are of the order of 5–10% for this hyphenated technique. The designs studied include slotted tube, single silica tube, and integrated atom trap water-cooled atom traps. The accuracy of this method was tested by analyses of BCS-CRM No.346 (Alloy), GBW 07302 (Stream Sediment), PACS-1 (Marine Sediment), NBS SRM 1633a (Coal Fly Ash), and NIST SRM 1643e (Trace Element in Water) certified reference materials. Agreement between analytical results and certified values for the test elements Ge and Sn (in the range of 1.7–91.0 µg g−1) were in agreement with recommended values. The measured Ge and Sn contents in five referenced materials were in satisfactory agreement with the certified values. The hyphenated technique was applied for germanium and tin determination in coal fly ash, soil, sediment, garlic, sewage, and river water.

Analytical Evaluation of an Integrated Ultrasonic Nebulizer-hydride Generator System for Simultaneous Determination of Hydride and Non-hydride Forming Elements by Microwave Induced Plasma Spectrometry

ABSTRACT The commercial ultrasonic nebulizer NOVA-DUO (ultrasonic nebulizer dual capillary system USN/DCS) has been evaluated for the simultaneous determination of classical hydride forming (As, Bi, Ge, Sb, Se, Sn) and conventional non-hydride forming (Ba, Ca, Fe, Li, Mg, Sr) elements by microwave induced plasma-optical emission spectrometry (MIP-OES). Simultaneous mixing and nebulization of the two solutions (acidified sample and reductant) on the piezoelectric transducer, with the possibility of flow rate adjustment, permits a wide variation of sensitivity. The hydrides and aerosols were rapidly transported via a stream of Ar carrier to a MIP for simultaneous multi-element determination by OES. A univariate approach and simplex optimization procedure was used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the USN/DCS observed at 11 µL min−1 flow rate. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of standard deviation of the blank (LOD, 3σblank criterion, peak height) were 1.3, 5.9, 6.6, 1.8, 3.6, 2.6, 41, 8.1, 11, 7.5, 9.2, and 12 ng mL−1 for As, Bi, Ge, Sb, Se Sn, Ba, Ca, Fe, Li, Mg, and Sr, respectively. The method offers relatively good precision (RSD ranged from 9 to 13%) for liquid analysis and microsampling capability. Interference effects by transition metals have been shown to be corrected by the addition of thiourea, as a pre-reducing agent and masking agent. The accuracy of the method was verified by the use of certified reference materials (NRCC DOLT-2, NRC GBW 07302, NIST SRM 2710, NIST SRM 1643e) and by aqueous standard calibration technique. All results obtained for reference materials were in agreement with certified values at 95% confidence level by Student t-test.

The Investigation of a Novel Indicator System for Trace Determination and Speciation of Selenium in Natural Water Samples by Kinetic Spectrophotometric Detection

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by p-nitrophenylhydrazine at pH 3.0. The generated bromine, <TEX>$Br_2$</TEX> or <TEX>$Cl_2$</TEX> plus <TEX>$Br_2$</TEX> in 0.1 M NaCl (or NaBr) environment efficiently decolorized Calmagite and the reaction was monitored spectrophotometrically at 523 nm as a function of time. In this indicator reaction, bromide acted as an activator for the catalysis of selenium (IV) and a reducing agent for selenium (VI) at pH 3.0, which allowed the determination of total selenium. The fixed time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the calibration graph are linear in the range 1 - 35 <TEX>${\mu}gL^{-1}$</TEX> of Se(IV) for the fixed time method at <TEX>$25^{\circ}C$</TEX>. The detection limit based on statistical <TEX>$3S_{blank}$</TEX>/m-criterion was 0.215 <TEX>${\mu}gL^{-1}$</TEX> for the fixed time method (7 min). All of the variables that affect the sensitivity at 523 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The RSDs for ten replicate measurements of 5, 15 and 25 <TEX>${\mu}gL^{-1}$</TEX> of Se(IV) and Se(VI) was changed between 2.1 - 4.85%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

Speciation and determination of ultra trace amounts of inorganic tellurium in environmental water samples by dispersive liquid–liquid microextraction and electrothermal atomic absorption spectrometry

A simple and powerful method has been developed for the rapid and selective determination of Te(IV) and Te(VI), employing dispersive liquid–liquid microextraction combined with electrothermal atomic absorption spectrometry using palladium as permanent modifier. Under acidic conditions pH 1, only Te(IV) can form a complex with ammonium pyrrolidine dithiocarbamate (APDC) and therefore be extracted into fine droplets of carbon tetrachloride (extraction solvent) which are dispersed with ethanol into the water sample solution. After centrifugation, Te(IV) was determined in the sedimented organic phase while Te(VI) remained in the aqueous phase. Total inorganic tellurium was determined after the reduction of the Te(VI) to Te(IV). Te(VI) was calculated as the difference between the measured total inorganic tellurium and Te(IV) content. The effective parameters for improving the efficiency of microextraction process were investigated by using experimental and central composite designs. Under optimal conditions the enrichment factor was 125 and the calibration graph was linear in the range of 0.015–1 ng mL −1 with detection limit and characteristic mass of 0.004 ng mL −1 and 0.033 pg, respectively. The relative standard deviation for 0.5 ng mL −1 of tellurium measurement was 3.6% ( n = 6) at ash and atomization temperature, 900 and 2600 °C, respectively. The recoveries of spiked Te(IV) and Te(VI) to the environmental water samples were 89.6–101.3% and 96.6–99.1%, respectively. The accuracy is also evaluated by applying the proposed method to certified reference material (NIST SRM 1643e), for which the result was in a good agreement with the certified values reported for this CRM (95% confidence level).

Method development for simultaneous multi-element determination of hydride forming elements (As, Bi, Ge, Sb, Se, Sn) and Hg by microwave induced plasma-optical emission spectrometry using integrated continuous-microflow ultrasonic nebulizer-hydride generator sample introduction system

Abstract The analytical potential of a coupled continuous-microflow ultrasonic nebulizer dual capillary system (µ-USN/DCS)–Ar/He mixed gas microwave induced plasma-optical emission spectrometry (MIP-OES) has been evaluated for the purpose of determination of hydride forming elements (As, Bi, Ge, Sb, Se, Sn) and a vapor element (Hg). A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the µ-USN/DCS observed at a 15 µL min− 1 flow rate. At flows of ≤ 15 µL min− 1, solvent loading in the plasma is sufficiently low to make desolvation unnecessary. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 1.2, 5.4, 6.3, 1.8, 3.3, 2.4 and 3.0 ng mL− 1 for As, Bi, Ge, Sb, Se, Sn and Hg, respectively. The method offers relatively good precision (RSD ranged from 8 to 11%) for liquid analysis and microsampling capability. Interference effects by transition metals have been shown to be corrected by the addition of thiourea, as a pre-reducing agent and masking agent. The accuracy of the method was verified using certified reference materials (DOLT-2, GBW 07302, SRM 2710, and SRM 1643e) and by the aqueous standard calibration technique. The measured contents of elements in reference materials were in satisfactory agreement with the certified values.

Determination of Cr(VI) and Cr(III) species in parenteral solutions using a nanostructured material packed-microcolumn and electrothermal atomic absorption spectrometry

A sequential on-line preconcentration and separation system for Cr(VI) and Cr(III) species determination was developed in this work. For this purpose, a microcolumn filled with nanostructured α-alumina was used for on-line retention of Cr species in a flow-injection system. The method involves the selective elution of Cr(VI) with concentrated ammonia and Cr(III) with 1 mol L −1 nitric acid for sequential injection into an electrothermal atomic absorption spectrometer (ETAAS). Analytical parameters including pH, eluent type, flow rates of sample and eluent, interfering effects, etc., were optimized. The preconcentration factors for Cr(VI) and Cr(III) were 41 and 18, respectively. The limit of detection (LOD) was 1.9 ng L −1 for Cr(VI) and 6.1 ng L −1 for Cr(III). The calibration graph was linear with a correlation coefficient of 0.999. The relative standard deviation (RSD) was 8.6% for Cr(VI) and 6.1% for Cr(III) ( c=10 μg L −1, n=10, sample volume=25 mL). Verification of the accuracy was carried out by analysis of a standard reference material (NIST SRM 1643e “Trace elements in natural water”) with a reported Cr content of 20.40±0.24 μg L −1. Using the proposed methodology the total Cr content, computed as sum of Cr(III) and Cr(VI), in this SRM was 20.26±0.96 μg L −1. The method was successfully applied to the determination of Cr(VI) and Cr(III) species in parenteral solutions. Concentration of Cr(III) species was found to be in the range of 0.29–3.62 μg L −1, while Cr(VI) species was not detected in the samples under study.

Flow injection solid phase extraction electrothermal atomic absorption spectrometry for the determination of Cr(VI) by selective separation and preconcentration on a lab-made hybrid mesoporous solid microcolumn

A lab-made hybrid mesoporous solid was employed in a flow injection solid phase extraction electrothermal atomic absorption spectrometric (FI–SPE–ETAAS) system for the selective retention of Cr(VI). The solid was prepared by co-condensation of sodium tetraethylortosilicate and 3-aminopropyltriethoxysilane by sol–gel methodology and one-pot synthesis and characterized by Fourier transform infrared spectroscopy, X ray diffraction spectroscopy, and scanning electronic microscopy. Adsorption capacities at different pH values of both, Cr(VI) and Cr(III), were also measured in order to obtain the optimum retention for Cr(VI) with no interference of Cr(III). The maximum capacity of adsorption (4.35 mmol g − 1) was observed for pH values between 2–3, whilst Cr(III) was found to remain in solution (adsorption capacity = 0.007 mmol g − 1). Then, a microcolumn (bed volume: 7.9 µL) was filled with the solid and inserted in the FI–ETAAS system for analytical purposes. Since the analyte was strongly retained by the filling in the anionic form, 0.1 mol L − 1 hydroxylammonium chloride in 1 mol L − 1 hydrochloric acid was selected as eluent due to its redox characteristics. In this way, the sorbed Cr(VI) was easily released in the cationic form. The enrichment factor (EF) was found as a compromise between sensitivity and sample throughput and a value of 27 was obtained under optimized conditions: pH 2, sample loading 2 mL min − 1 (60 s), elution flow rate 0.5 ml min − 1 (eluent volume: 75 μL). Under optimized conditions the limit of detection for Cr(VI) was 1.2 ng L − 1, the precision, expressed as RSD was 2.5%, the sample throughput 21/h, and the microcolumn lifetime was over 300 adsorption/desorption cycles. Cr(III) determination was also performed by simply measuring its concentration at the end of the column and after Cr(VI) retention by the mesoporous solid. Applications of the methodology to the determination of Cr(VI) in deionized, osmosis, mineral, effluent and river waters showed very good results. Validation was performed by means of recovery studies as no certified materials were available for Cr(VI). Total chromium determinations, obtained by the sum of Cr(III) and Cr(VI) concentrations, were validated using NIST, SRM 1643e certificate reference material (Trace Element in Natural Water).

Simple and selective determination of arsenite and arsenate by electrospray ionization mass spectrometry

Arsenic pollution of public water supplies has been reported in various regions of the world. Recently, some cancer patients are treated with arsenite (As III); most Japanese people consume seafoods containing large amounts of negligibly toxic arsenic compounds. Some of these arsenic species are metabolized, but some remain intact. For the determination of toxic As III, a simple, rapid and sensitive method has been developed using electrospray ionization mass spectrometry (ESI-MS). As III was reacted with a chelating agent, pyrrolidinedithiocarbamate (PDC, C 4H 8NCSS –) and tripyrrolidinedithiocarbamate-arsine, As(PDC) 3, extracted with methyl isobutyl ketone (MIBK). A 1 μL aliquot of MIBK layer was directly injected into ESI-MS instrument without chromatographic separation, and was detected within 1 min. Arsenate (As V) was reduced to As III with thiosulfate, and then the total inorganic As was quantified as As III. This method was validated for the analysis of urine samples. The limit of detection of As was 0.22 μg L −1 using 10 μL of sample solution, and it is far below the permissible limit of As in drinking water, 10 μg L −1, recommended by the WHO. Results were obtained in < 10 min with a linear calibration range of 1–100 μg L −1. Several organic arsenic compounds in urine did not interfere with As III detection, and the inorganic As in the reference materials SRM 2670a and 1643e were quantified after the reduction of As V to As III.

Ionic liquid-based single drop microextraction combined with electrothermal atomic absorption spectrometry for the determination of manganese in water samples

Room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C 4MIM][PF 6], was used as an alternative to volatile organic solvents in single drop microextraction-electrothermal atomic absorption spectrometry (SDME-ETAAS). Manganese was extracted from aqueous solution into a drop of the ionic liquid after complextaion with 1-(2-thiazolylazo)-2-naphthol (TAN) and the drop was directly injected into the graphite furnace. Several variables affecting microextraction efficiency and ETAAS signal, such as pyrolysis and atomization temperature, pH, TAN concentration, extraction time, drop volume and stirring rate were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.024 μg L −1 and 30.3, respectively. The relative standard deviation (RSD) for five replicate determinations of 0.5 μg L −1 Mn(II) was 5.5%. The developed method was validated by the analysis of a certified reference material (NIST SRM 1643e) and applied successfully to the determination of manganese in several natural water samples.

Determination of Urine Luck in urine using electrospray ionization tandem mass spectrometry

A simple, rapid and sensitive method using tandem mass spectrometry (MS-MS) has been developed for the determination of chromate Cr6+ in urine. Cr6+ is a substantial component of Urine Luck, which is used to conceal the presence of drugs in urine. Cr6+ was complexed with diethyldithiocarbamate (DDC) and extracted with isoamyl alcohol in the presence of citric acid. Then a 1-μl aliquot of isoamyl alcohol containing Cr-DDC complex was directly injected into an MS-MS instrument without chromatographic separation. The quantification was performed using selected reaction monitoring at m/z 363.8 of product ion CrO(DDC)2 + obtained by collision-induced dissociation from the precursor ion, CrOH(DDC)3 + at m/z 513.1. This method was validated with the analysis urine samples obtained from volunteers. A linear calibration curve could be obtained in the range of 0.18–100 ng/ml. The limits of detection and quantification of Cr6+ were 0.05 and 0.18 ng/ml, respectively, using only 10 μl of urine. Results could be obtained in less than 10 min for a sample. After oxidation of Cr3+ to Cr6+, near 100% recovery was confirmed using standard reference materials such as SRM 2670a (low level and high level) and SRM 1643e. The most outstanding advantage of this ESI-MS-MS method is that it gives excellent product ion mass spectra for identification of Cr6+.

A novel fiber-packed column for on-line preconcentration and speciation analysis of chromium in drinking water with flame atomic absorption spectrometry

A novel on-line preconcentration and determination system based on a fiber-packed column was developed for speciation analysis of Cr in drinking water samples prior to its determination by flame atomic absorption spectrometry (FAAS). All variables involved in the development of the preconcentration method including, pH, eluent type, sample and eluent flow rates, interfering effects, etc., were studied in order to achieve the best analytical performance. A preconcentration factor of 32 was obtained for Cr(VI) and Cr(III). The levels of Cr(III) species were calculated by difference of total Cr and Cr(VI) levels. Total Cr was determined after oxidation of Cr(III) to Cr(VI) with hydrogen peroxide. The calibration graph was linear with a correlation coefficient of 0.999 at levels near the detection limit and up to at least 50 μg L −1. The relative standard deviation (R.S.D.) was 4.3% ( C = 5 μg L −1 Cr(VI), n = 10, sample volume = 25 mL). The limit of detection (LOD) for both Cr(III) and Cr(VI) species was 0.3 μg L −1. Verification of the accuracy was carried out by the analysis of a standard reference material (NIST SRM 1643e “Trace elements in natural water”). The method was successfully applied to the determination of Cr(III) and Cr(VI) species in drinking water samples.

A new solid-phase extraction method for the determination of Cu(II) and Fe(III) in various samples by flame atomic absorption spectrometry using N-benzoyl-N-phenylhydroxylamine

A novel column solid phase extraction method was developed for the determination of Cu(II) and Fe(III) in various samples by flame atomic absorption spectrometry (FAAS) after preconcentration as their N-benzoyl-N-phenylhydroxylamine complexes on Amberlite XAD-1180 resin. Elution was performed with 1 mol L−1 HCl in acetone. The effects of some analytical parameters such as pH, amount of reagent, eluent type, concentration and volume, flow rate of sample and elution solutions, volume of the sample solution and matrix interference were investigated. The recoveries of Cu(II) and Fe(III) under optimum conditions were ≥95%. A good relative standard deviation (≤2.0%), a good preconcentration factor (50) and low detection limits (0.82 μg L−1 for Cu and 1.05 μg L−1 for Fe) were obtained. The accuracy of the procedure developed was confirmed by determining the analytes in three certified reference materials (TMDA-54.4 fortified lake water, SRM 1643e trace elements in water, SRM 1568a rice flour) and the analysis of spiked water samples. The results showed a good agreement with the certified values. The method was applied to the determination of the analytes in water (sea water, dam water, lake water and waste water), vegetable, rice and spices samples.

Application of electrospray ionization tandem mass spectrometry for the rapid and sensitive determination of cobalt in urine

Recently, cobalt (Co) is reported to be taken as a supplement by athletes for improving anaerobic performance. For the diagnosis of abuse, the limit of detection (LOD) of Co in the analysis should be lower than the concentrations of Co in plasma and urine of normal persons. A simple, rapid and sensitive method has been developed for the determination of Co in urine. Co was complexed with diethyldithiocarbamate (DDC) and extracted with isoamyl alcohol in the presence of citric acid. The detection of Co was achieved by injecting a 1-μL aliquot of isoamyl alcohol containing Co–DDC complex directly into an electrospray ionization tandem mass spectrometric (ESI-MS–MS) instrument without chromatographic separation. The quantification was performed using selected reaction monitoring at m/ z 291 of the product ion Co(C 4H 10NCS) 2 + which was produced by collision-induced dissociation from the precursor ion Co(DDC) 2 + at m/ z 355. ESI-MS–MS data were obtained in less than 10 min with an LOD of 0.05 μg L −1 and a linear calibration range of 0.1–100 μg L −1 using 10 μL of urine. The procedure was validated with certified reference materials (SRM 2670a and SRM 1643e). This method is suitable for the analysis of Co in the laboratories already equipped with an ESI-MS–MS instrument.

Determination of total antimony and inorganic antimony species by hydride generation in situ trapping flame atomic absorption spectrometry: a new way to (ultra)trace speciation analysis

The analytical performance of non-chromatographic coupled hydride generation, integrated atom trap (HG-IAT) atomizer flame absorption spectrometry (FAAS) systems were evaluated for the speciation analysis of antimony in environmental samples. Antimony, using formation of stibine (SbH3) vapors were atomized in an air–acetylene flame-heated IAT. A new design of HG-IAT-FAAS hyphenated technique that would exceed the operational capabilities of existing arrangements (a water-cooled single silica tube, double-slotted quartz tube or an “integrated trap”) was investigated. For the estimation of Sb(III) and Sb(V) concentrations in samples, the difference between the analytical sensitivities of the absorbance signals obtained for antimony hydride without and with previous treatment of samples with L-cysteine can be used. The concentration of Sb(V) was calculated by the difference between total Sbtot and Sb(III). A dramatic improvement in detection limit was achieved compared with that obtained using either of the atom trapping techniques, presented above, separately. This novel approach decreases the detection limit down to low pg mL–1 levels. The concentration detection limit, defined as 3 times the blank standard deviation (3sigma), was 0.2 ng mL–1. For a 120 s in situ pre-concentration time (sample volume of 2 mL), sensitivity enhancement compared to flame AAS, was 550 fold for Sb, using hydride generation-atom trapping technique. The sensitivity can be further improved by increasing the collection time. The precision, expressed by RSD, was 8.0% (n = 6) for Sb. The designs studied include slotted tube, water-cooled single silica tube and integrated atom traps. Reference and real sample materials were analyzed. The accuracy of the method was verified by the use of certified reference materials (NIST SRM 2704 Buffalo River Sediment, SRM 2710 Montana Soil, SRM 1633a Coal Fly Ash, SRM 1575 Pine Needles, SRM 1643e Trace Elements in Water) and by aqueous standard calibration technique (solutions). The measured Sb content, in reference materials, were in satisfactory agreement with the certified values. The hyphenated technique was applied for antimony determinations in soil, sediment, coal fly ash, sewage and river water.

Determination of tellurium at ultra-trace levels in drinking water by on-line solid phase extraction coupled to graphite furnace atomic absorption spectrometer

In this paper, two time-based flow injection (FI) separation pre-concentration systems coupled to graphite furnace atomic absorption spectrometry (GFAAS) for tellurium determination are studied and compared. The first alternative involves the pre-concentration of the analyte onto Dowex 1X8 employed as packaging material of a micro-column inserted in the flow system. The second set-up is based on the co-precipitation of tellurium with La(OH) 3 followed by retention onto XAD resins. Both systems are compared in terms of limit of detection, linear range, RSD%, sample throughput, micro-columns lifetime and aptitude for fully automatic operation. The features of the Dowex system are: 37% efficiency of retention and an enhancement factor of 42 for a pre-concentration time of 180 seconds (sample flow rate = 3 ml min − 1 ) with acetic acid elution volumes of 80 μl. The detection limit (3 s) is 7 ng l − 1 and the relative standard deviation ( n = 7200 ng l − 1 ) is 5.8%. The analytical performance of the XAD system is: 72% efficiency of retention and an enhancement factor of 25 for a pre-concentration time of 180 s (sample flow rate = 3 ml min − 1 ) with nitric acid elution volumes of 300 μl. The detection limit is 66 ng l − 1 and the relative standard deviation ( n = 7200 ng l − 1 ) is 8.3%. Applications to the determination of tellurium in tap water and the validation of the analytical methodology employing SRM 1643e as certified reference material are shown.

Simultaneous on-line pre-concentration and determination of trace metals in environmental samples by flow injection combined with inductively coupled plasma mass spectrometry using silica gel modified with niobium(V) oxide

This work presents the development of an on-line pre-concentration system for simultaneous determination of Cd, Cu, Ni, V, Zn, Co and Pb in aqueous environmental samples and detection by inductively coupled plasma mass spectrometry. The system is based on cationic retention of the analytes onto a mini-column filled with silica gel modified with niobium(V) oxide. The effects of chemicals and flow variables have been investigated. The optimized operating conditions, selected as a compromise between sensitivity and analytical frequency were: sample pH 7.0, sample flow rate of 6.0 mL min −1, eluent flow rate of 2.0 mL min −1, and eluent (HNO 3) concentration of 2.5 mol L −1. The relative standard deviation ( n = 7), enrichment factor and linear working range were 0.8–4.5%, 23.3–37.2 and 0.05–25.0 μg L −1, respectively. Limits of detection were between 0.01 and 0.03 μg L −1. The accuracy of the proposed method was checked with certified materials (NASS-4, NASS-5, CASS-4 and SRM 1643e). Values obtained were in accordance with those reported for the certified materials. Recovery was found to be in the range of 90–110% for a suit of water samples with variable matrices (seawater, tap water and ground water) collected in Florianopolis, Brazil.

Introducing wet aerosols into the static high sensitivity ICP (SHIP)

A demountable design of the static high sensitivity ICP (SHIP) for optical emission spectrometry is presented, and its use as an excitation source with the introduction of wet aerosols was investigated. Aerosols were produced by standard pneumatic sample introduction systems, namely a cross flow nebulizer, Meinhard nebulizer and PFA low flow nebulizer, which have been applied in conjunction with a double pass and a cyclonic spray chamber. The analytical capabilities of these sample introduction systems in combination with the SHIP system were evaluated with respect to the achieved sensitivity. It was found that a nebulizer tailored for low argon flow rates (0.3-0.5 L min(-1)) is best suited for the low flow plasma (SHIP). An optimization of all gas flow rates of the SHIP system with the PFA low flow nebulizer was carried out in a two-dimensional way with the signal to background ratio (SBR) and the robustness as optimization target parameters. Optimum conditions for a torch model with 1-mm injector tube were 0.25 and 0.36 L min(-1) for the plasma gas and the nebulizer gas, respectively. A torch model with a 2-mm injector tube was optimized to 0.4 L min(-1) for the plasma gas and 0.44 L min(-1) for the nebulizer gas. In both cases the SHIP system saves approximately 95% of the argon consumed by conventional inductively coupled plasma systems. The limits of detection were found to be in the low microgram per litre range and below for many elements, which was quite comparable to those of the conventional setup. Furthermore, the short-term stability and the wash out behaviour of the SHIP were investigated. Direct comparison with the conventional setup indicated that no remarkable memory effects were caused by the closed design of the torch. The analysis of a NIST SRM 1643e (Trace Elements in Water) with the SHIP yielded recoveries of 97-103% for 13 elements, measured simultaneously.