Continuous Flow Hydride Generation Research Articles

Spray assisted preconcentration method combined with HPLC – Continuous flow hydride generation – FAAS for inorganic arsenic speciation in olive oil samples

Speciation analysis of arsenic in edible oils is an important topic in terms of the assessment of its risks for human health and the quality of edible oils. In this study, high performance liquid chromatography – continuous flow hydride generation – flame atomic absorption spectrometry (HPLC-CFHG-FAAS) system after vortex assisted reverse phase spray-based fine droplet formation liquid phase microextraction (VA-RP-SFDF-LPME) method was proposed to qualify/quantify arsenite and total arsenic. Limit of detection (LOD) and limit of quantification (LOQ) for arsenite were calculated as 2.86 µg kg–1 (as As) and 9.52 µg kg–1 (as As), respectively. After the extraction/preconcentration process, a prereduction was carried out in the presence of 0.010 mol/L HCl (containing 0.39% L-cysteine) with heat (90 ± 5 oC) for the determination of total arsenic content while arsenite was directly determined via the developed system. Recovery for arsenite and total inorganic arsenic were in the range of 91.5 – 120.4% and 90.0 – 104.4%, respectively. The developed method is proposed for the analysis of olive oil samples containing inorganic arsenic species. This is the first study to carry out the inorganic arsenic speciation in olive oil by HPLC-CFHG-FAAS system after the preconcentration of the species by the VA-RP-SFDF-LPME system. For the matrix including arsenite and arsenate, the developed method can be safely used to find the concentration of both species accurately.

Dynamic thin-film microextraction method using cellulose platforms modified with silver nanoparticles for preconcentration of volatile hydride-forming elements prior to inductively-coupled plasma mass spectrometry determination

In this work, a novel preconcentration method was developed for As, Sb and Bi following trapping of their volatile hydride derivatives onto cellulose-based platforms modified with Ag nanoparticles for ultrasensitive determination by inductively-coupled plasma mass spectrometry (ICP-MS). A continuous flow hydride generation system was coupled to a gas-liquid separation unit integrated with the preconcentration platform. AsH3, SbH3 and BiH3 were retained onto the silver nanoparticles (AgNPs) modified cellulose substrate upon catalytic decomposition. After a 10 min preconcentration time, enrichment factors of 16, 9 and 26 for As, Sb and Bi were obtained, respectively. These values can be increased when needed by a factor of three applying a preconcentration time of 30 min. Elution of analytes trapped onto AgNPs with 0.1 M HNO3 (As, Sb) or 1 M HNO3 (Bi) was performed and metal content in the eluates was measured by ICP-MS. Detection limits of 15, 2 and 1 ng/L for As, Sb and Bi were obtained, respectively. Repeatability values expressed as relative standard deviation (%) was in the range of 1.2–2.7%. Other hydrides tried (i.e. SeH2 and TeH2) did not provide suitable performance owing to inefficient desorption from the cellulose substrate. Simulated water matrices mimicking the major composition of freshwater, seawater, wastewater and groundwater were analyzed, recoveries being in the range of 80–106%.

Concentrations of mercury and other elements in ewes’ milk: Effect of lactation stage

There is an increased production and demand for ewes’ milk in the Republic of Croatia, as well as globally. There is also a growing concern about its quality, since milk from farm animals may become contaminated with mercury and other toxic elements. Thus, the aim of this paper is to determine the influence of lactation stage on the ewes’ milk quality in western Croatia by considering concentrations of mercury and other elements in ewes’ milk. The research was conducted on 36 Travnik pramenka sheep during different lactation stages. The digested milk samples were analysed with continuous flow hydride generation technique by using inductively coupled plasma mass spectrometry. Samples were taken during 40th, 80th and 120th d of lactation. Yield and quality of ewes’ milk was within lactation curve. As lactation progressed, significantly lower concentrations of Hg (on 80th d compared to 40th d) and of Cd (120th d compared to 80th d) were noted, and Hg on 120th d was below the detection limit. Concentrations of Ca and Cu were lower on the 120th d compared to 40th d, while P, Mg, Fe, Zn, Mn, and Se were lower on the 80th and 120th d compared to the 40th d. Concentrations of K, Mo, and Cr differed among all stages of lactation. Regarding toxic elements, the observed low concentrations of Hg, Co, Cd and As suggest that ewes’ milk in western Croatia is safe for human or animal consumption.

Trace Determination of Germanium by Continuous Flow Hydride Generation Laser-Induced Fluorescence Spectrometry

A continuous flow hydride generation laser-induced fluorescence (HG-LIF) spectrometry technique has been investigated for performing trace determination of germanium (Ge). Hydride generation of Ge is performed using reagent concentrations of 2 M H3PO4 and 0.5% NaBH4 and fluorescence detection is performed using tunable dye laser radiation at 253.323 nm for Ge excitation with fluorescence measured at 303.907 nm. The HG-LIF approach provides a linear response for Ge in the concentration range from 1.0 to 50 ng mL−1 and a limit of detection of 0.1 ng mL−1. Replicate measurements at 10 ng mL−1 have a relative standard deviation of 0.1% (n = 8). Measurements of Ge in different sample matrices have demonstrated the effectiveness of thiourea and ascorbic acid as masking agents that compensate for samples containing interfering ions. The determinations of the Ge content in reference water samples, fly ash samples, and supplement capsules demonstrate that the HG-LIF approach has feasibility for measuring Ge in different sample matrices at environmentally relevant concentrations.

Multivariate optimization of a digestion procedure for bismuth determination in urine using continuous flow hydride generation and atomic fluorescence spectrometry

A sensitive method has been developed for the determination of bismuth in urine using continuous flow hydride generation and atomic fluorescence spectrometry (HG AFS). The conditions for bismuth hydride generation as well as some instrumental parameters were optimized using univariate methodology. Experimental conditions for sample digestion using nitric acid, hydrogen peroxide and a reflux system by “cold finger” were optimized employing a two-level full factorial design and a Box-Behnken design. Nitric acid used during sample preparation showed a negative effect on Bi determination by HG AFS, and a drying step was required after digestion. The established conditions for sample digestion allowed a low residual carbon content. Thus, the proposed method, using 5mL urine, allowed bismuth determination with limits of detection and quantification of 0.02 and 0.08μgL−1, respectively. Accuracy was assessed by the spike/recovery test using urine samples and the recoveries obtained varied from 91and 97%. Precision expressed as relative standard deviation (RSD) was lower than 10%. This method was satisfactorily applied for the determination of bismuth in five urine samples. The bismuth contents found ranged from 0.30 to 0.66μgL−1.

Effect of lactation stage on the concentration of essential and selected toxic elements in milk of Dubrovačka ruda - Croatian endangered breed

The aim of the present study was to determine the lactation stage effect on the concentration of essential and selected toxic elements in the sheep’s milk of Dubrovacka ruda. The research was conducted with 23 sheep, average age of 4 years, of 3rd lactation, while the milk samples were taken during the early (60th day), middle (90th day) and late (120th day) lactation stage. The sheep were selected according to uniformed body development, adequate health status, body condition, equable age (4 years), parity (3rd lactation), stage of lactation (±7 days) and litter size (single). Sheep were reared on the extensive Mediterranean pastures, reared indoors afterwards, fed with hay ad libitum and feed mixtures in average 0.5 kg/day. Milk sample was collected during morning milking from each sheep. The digested samples were analyzed with continuous flow hydride generation technique using inductively coupled plasma for Ca, Mg, K, P, Na, Cu, Fe, Zn, Mn, Ni, Mo, Co, Cr, Cd and Pb concentrations. Significant increase of Mg, Na, Se, Mn, Mo and Cd concentrations were found in milk as well as decrease of K concentration during the lactation. Although the concentration of Ca, Cu, Cr and As in milk during the lactation is increased, the differences between the lactation stages were not observed. Concentrations of P, Fe, Ni, Pb and Hg in milk of Dubrovacka ruda did not differ during the lactation. The low concentrations of Cr, Cd, Pb, As, Hg in milk indicate the safety for consumers and preserved environment of Dubrovnik-Neretva County.

Strategy of Sample Preparation for Arsenic Determination in Mineral Fertilizers

A method for determination of arsenic in mineral fertilizers by continuous flow hydride generation atomic absorption spectrometry (CF-HG-AAS) was developed by using diluted acid and digester block with perfluoroalkoxy (PFA) tubes to sample preparation. An additional sample preparation procedure using microwave-assisted digestion was evaluated and compared with the proposed procedure. A full factorial design was applied to investigate the effect of the variables and the best conditions found were 7 mol L−1 HNO3 + 30% (m/m) H2O2 as reagents, 4 h of digestion and concentration of reagents diluted 1:1. The effect of concomitants on the analytical signal of arsenic was investigated and no one significant interference was observed, with recoveries ranged from 97 to 103%. The accuracy of proposed method was evaluated by certified reference material (NIST SRM 695) and recovery of 95% was obtained. The arsenic concentration (8.9 ± 0.2 mg kg−1) found in the fertilizer is below of maximum concentration established by Brazilian legislation.

Improvement in thallium hydride generation using iodide and Rhodamine B

A continuous flow hydride generation atomic absorption spectrometry (CF-HG-AAS) system was used to study the enhancement effect of different substances for conventional chemical HG of thallium. At room temperature, the acidified sample solution containing the respective enhancement reagent merged with the aqueous NaBH4 solution. The generated thallium hydride was stripped from the eluent solution by the addition of a nitrogen flow and thereafter the bulk phases were separated in a gas–liquid separator. The main factors under study were concentration and type of enhancement reagent (Te, iodide added as KI, Rhodamine B, malachite green and crystal violet) and acid (HCl, H2SO4 or HNO3). Other parameters affecting the thallium hydride generation, such as: NaBH4 concentration, carrier gas flow rate, length of reaction-mixing coil and reagents flow rates, were studied and optimized. Among the enhancement reagents tested, the combination of Rhodamine B and iodide produced the best results. A linear response was obtained between the detection limit (LOD (3σ)) of 1.5μgL−1 and 1000μgL−1. The RSD% (n=10) for a solution containing 15μgL−1 of Tl was 2.9%. The recoveries of thallium in environmental water samples by spiking the samples with 10 and 20µgL−1 of Tl were in the 97.0–102.5% range. The accuracy for Tl determination was further confirmed by the analysis of a water standard reference material (1643e form NIST, USA). Finally, it was demonstrated that malachite green and crystal violet showed similar enhancement effect like Rhodamine B for thallium HG.

Understanding the effects of potassium ferricyanide on lead hydride formation in tetrahydroborate system and its application for determination of lead in milk using hydride generation inductively coupled plasma optical emission spectrometry

To understand the formation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system, the intermediate products produced in the reaction of lead(II) and NaBH4 in the presence of K3Fe(CN)6 were studied. The produced plumbane and elemental lead were measured through continuous flow hydride generation (HG)-inductively coupled plasma optical emission spectrometry (ICP OES) and X-ray diffraction spectrometry techniques, respectively. Based on the experimental results, the explanations can be depicted in the following steps: (1) plumbane and black lead sediment (black Pb) are formed in the reaction of lead(II) and NaBH4; (2) the black Pb is oxidized by K3Fe(CN)6 to form Pb2[Fe(CN)6], which further reacts with NaBH4 to form more plumbane and black Pb; and (3) another round starts in which the produced black Pb from the step 2 is then oxidized continuously by K3Fe(CN)6 to form more Pb2[Fe(CN)6] complex, which would produce more plumbane. In short, the black Pb and Pb2[Fe(CN)6] complex are the key intermediate products for the formation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system. Based on the enhancement effect of potassium ferricyanide and potassium ferrocyanide, a method was developed to analyze lead in milk with HG-ICP OES technique. The detection limit of the method was observed as 0.081 μg L(-1). The linearity range of lead was found between 0.3 and 50,000 μg L(-1) with correlation coefficient of 0.9993. The recovery of lead was determined as 97.6% (n=5) for adding 10 μg L(-1) lead into the milk sample.

Chemical Generation of Arsane and Methylarsanes with Amine Boranes. Potentialities for Nonchromatographic Speciation of Arsenic

The efficiency of chemical generation of arsanes from inorganic arsenic, monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA), to arsane, AsH3, monomethylarsane, CH3AsH2 (MMA), and dimethylarsane, (CH3)2AsH (DMA), has been investigated in different reaction media with the aim to better elucidate the mechanisms controlling their generation process and to find the experimental conditions to implement a nonchromatographic arsenic speciation analytical method, which is based on the selective determination of some arsenic species. Studies were performed by continuous flow hydride generation coupled with atomic spectrometry (CF-HG-AS), using different reductants such as borane-ammonia (AB), borane-tert-butylamine (TBAB), and sodium tetrahydridoborate (THB) in HCl and HClO4 media, in the presence or absence of L-cysteine (Cys). The efficiency of HG processes for MMA and DMA is mainly controlled by the reactivity of the substrates with the borane, which could be strongly influenced by the formation of ion couples. The protonation of arsane did not play a significant role in the employed reaction system. By taking advantage of the different reactivity pattern of As species in selected generation conditions, DMAA and MMAA could be selectively determined in 0.5 and 10 M HClO4 solutions, respectively, in the presence of Cys, with AB as the reducing agent. The presence of Cys as a masking agent and the peculiar reducing properties of AB ensured a good control of interferences, as far as it has been observed for Co(II), Ni(II), Cu(II), Fe(II), Fe(III). The overall time needed to complete the prereduction step has been verified for MMAA and DMAA at different acidities in order to achieve the best selectivity. The selective determination of DMAA with AB/Cys in HClO4 has been optimized and applied to certified reference materials (CRMs) of natural waters CASS-4, SLRS-4, and NASS-4 (NRCC). The estimation of DMAA concentration allows us to correct the concentration of As(III) for the interference of DMAA in the selective determination of As(III) according to a selective HG method recently reported.

Flow‐Through Potentiometric Sensors for Alizarin Red S Dye and Their Application for Aluminum Determination

AbstractNovel selective and sensitive poly (vinyl chloride) membrane sensors are developed for measuring alizarin red S (AR) based on the use of aliquate 336, MgIIphthalocyanine (MgPc), CuIIphthalocyanine (CuPc) and FeII phthalocyanine (FePc) plasticized poly (vinyl chloride) membrane. The sensors display Nernestian response with slopes of ‐50.6 ± 0.6 , ‐37.4 ± 0.5 , ‐37.7 ± 0.8 and ‐35.0 ± 0.7 mV decade−1 over the range of 5.2 × 10−6 to 1 × 10−2 mol L−1 for all of them and detection limits of 5.9 × 10−7, 1.9 × 10‐−6 2.3 × 10−6 and 1.9 × 10−6 mol L−1 for aliquate, MgPc, CuPc and FePc membrane based sensor, respectively. The sensors exhibit long life span, long term potential stability, high reproducibility, fast response and good discrimination ability towards alizarinate ion in comparison with many other anions. A tubular detector based on aliquate, MgPc, CuPc and FePc was further developed and coupled to a flow‐injection system for alizarin (AR) determination. Under optimized conditions, the linearity range is 1.0 × 10−5‐ 1.0 × 10−1 mol L−1, with a slope of ‐52.1 ± 0.8, 20.9 ± 0.7, 23.6 ± 0.4 and 25 ± 1.1 mV decade−1 and a reproducibility of ± 0.8 mV (n = 6) for aliquate, MgPc, CuPc and FePc membrane based sensors, respectively. The sensor based on aliquate is further utilized for a potentiodynamic quantification of aluminum in sludge samples and deodorants. The buffered solution of alizarin was allowed to react in a flow system with aluminum. The calibration curve of Al was found to be linear over a concentration range of 0.1 to 1.8 and 1.0 ‐ 40 μg mL−1 with a slope = 16.9 (r2 = 0.993) and 1.76 (r2 = 0.994) mV (μg/mL)−1 and a detection limit of 0.08 and 0.5 μg mL−1 for 10−4 and 10−3 mol L−1 AR− as a carrier, respectively. The method was successfully used for determining aluminum in sludge samples and deodorants. The data agree fairly well the nominal values and with results obtain by continuous flow hydride generation inductively coupled plasma (ICP) method.

Nickel-aluminum layered double hydroxide as a nano-sorbent for the solid phase extraction of selenium, and its determination by continuous flow HG-AAS

We have used a nano-structured nickel-aluminum layered double hydroxide (Ni-Al LDH) for the extraction of trace levels of selenium prior to its determination by continuous-flow hydride generation atomic absorption spectrometry. Extraction is based on the adsorption of Se(IV) anions on the Ni-Al-nitrate LDH, and/or their exchange with the nitrate anions in the LDH interlayer. The effects of pH value, amount of nanosorbent, eluent type and concentration, sample volume and flow rate were optimized. No appreciable matrix effects were observed. Under optimum conditions, the limit of detection (defined as three times the standard deviation of the blank signal divided by the slope of the calibration plot) is 10 pg mL−1, and the relative standard deviation is 2.8 %. The sorption capacity and preconcentration factor are 10 mg g−1 and 33, respectively. The method was successfully applied to the determination of Se(IV) in tap water, river water, well water, wastewater and oyster tissue (certified reference material, CRM 1566b).

Optimization of chemical and instrumental parameters in hydride generation laser-induced breakdown spectrometry for the determination of arsenic, antimony, lead and germanium in aqueous samples

A laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1mgL−1, 1.0mgL−1, 1.3mgL−1 and 0.2mgL−1 were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.

Fast Sequential Determination of As and Sb, Bi and Pb by Continuous Flow Hydride Generation Atomic Absorption Spectrometry

In this study, two methods were developed for the sequential determination of As and Sb, Bi and Pb using fast sequential continuous flow hydride generation atomic absorption spectrometry. Limits of detection obtained for As and Sb were 0.15 and 0.16 μg L−1 and for Bi and Pb were 0.60 and 0.77 μg L−1, respectively. Arsenic, Sb, and Bi were free from the influence of possible interferents in the levels investigated, but Pb showed a significant analytical signal decrease when Co, Cu, Fe, Ni, and HNO3 were presented in the solutions. The methods were applied to the analysis of water from the Tiete River (Sao Paulo State, Brazil), sea water from Praia Grande—Ubatuba (Sao Paulo State), chicken feed, trace elements in water (NIST 1643e), and trace metals in drinking water (HPS TMDW). The obtained recoveries varied from 88 (for As) to 116 % (for Bi).

Optimization of Continuous Flow Hydride Generation Inductively Coupled Plasma Optical Emission Spectrometry for Sensitivity Improvement of Bismuth

Experimental variables in continuous flow hydride generation inductively coupled plasma-optical emission spectrometry (CF-HG-ICP-OES) were optimized for determination of bismuth. Concentrations of NaBH4, HCl, and NaOH, flow rates of NaBH4, sample solution, waste and carrier argon, radio frequency power, lengths of reaction, and stripping coils were optimized to obtain lower detection limits. Under optimum conditions, the detection limit was calculated as 0.16 ng mL−1, and the calibration plot was linear between 1.0–50.0 ng mL−1. An improvement in detection limit of 5.75 times by CF-HG-ICP-OES was reached vs. ICP-OES. Relative standard deviation (RSD) for ten replicate measurements of 10.0 ng mL−1 Bi was calculated as 3.9%. Effect of possible interferic ions on Bi signal was evaluated. Accuracy of method was verified by using a standard reference material, SRM 1643e. Results found for Bi were in satisfactory agreement with certified values. The proposed method was then employed to determine trace concentration of Bi in milk samples. Bi amounts in samples were found in the range from lower than the quantitation limit to 14.5 ng mL−1, whereas Bi concentrations were lower than the detection limit in three samples.

Method development and optimization for the determination of selenium in bean and soil samples using hydride generation electrothermal atomic absorption spectrometry

The present investigation is the first part of an initiative to prepare a regional map of the natural abundance of selenium in various areas of Brazil, based on the analysis of bean and soil samples. Continuous-flow hydride generation electrothermal atomic absorption spectrometry (HG-ET AAS) with in situ trapping on an iridium-coated graphite tube has been chosen because of the high sensitivity and relative simplicity. The microwave-assisted acid digestion for bean and soil samples was tested for complete recovery of inorganic and organic selenium compounds (selenomethionine). The reduction of Se(VI) to Se(IV) was optimized in order to guarantee that there is no back-oxidation, which is of importance when digested samples are not analyzed immediately after the reduction step. The limits of detection and quantification of the method were 30ngL−1 Se and 101ngL−1 Se, respectively, corresponding to about 3ngg−1 and 10ngg−1, respectively, in the solid samples, considering a typical dilution factor of 100 for the digestion process. The results obtained for two certified food reference materials (CRM), soybean and rice, and for a soil and sediment CRM confirmed the validity of the investigated method. The selenium content found in a number of selected bean samples varied between 5.5±0.4ngg−1 and 1726±55ngg−1, and that in soil samples varied between 113±6.5ngg−1 and 1692±21ngg−1.

Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China

Organic matter plays an important role in the transport and precipitation of germanium (Ge) in coal-hosted Ge deposits. In this paper, Ge isotopes of coal samples and their combustion products were analyzed in order to investigate the potential use of Ge isotopes as tracers of Ge sources and enrichment mechanisms in coal. Germanium isotopic composition of various samples (mainly Ge-rich lignite) from the Lincang Ge deposit, Yunnan, Southwest China was analyzed using a continuous flow hydride generation system coupled to a Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) and the standard-sample bracketing approach. Variations of 74 Ge/ 70 Ge ratios are expressed as δ 74 Ge values relative to NIST SRM 3120a Ge standard solution. Ge-rich lignite samples show large Ge isotopic fractionation ( δ 74 Ge values range from − 2.59‰ to 4.72‰), and their δ 74 Ge values negatively correlate with Ge concentrations. Lignite samples with low Ge concentrations (< 500 ppm) tend to show positive δ 74 Ge values, while δ 74 Ge values of lignite samples with high Ge concentrations (> 1000 ppm) are close to zero or negative. Along stratigraphic sections, Ge is mainly concentrated in the top or the bottom of the coal seam, such that high values of δ 74 Ge are usually found in the middle part of the coal seam. Interlayered hydrothermal chert and limestone samples in Ge-rich coal seams also show moderate fractionation ( δ 74 Ge values range from − 0.14‰ to 2.89‰ and from 0.55‰ to 1.87‰, respectively). The overall variations of δ 74 Ge values of Ge-rich lignite and organic-rich chert samples can be well described by a Rayleigh fractionation model, indicating that preferential enrichment of light Ge isotopes in coal in an open system might be the main factor controlling Ge fractionation in Ge-rich lignite. The germanium isotopic composition of hydrothermal chert (and possibly limestone) might also record the competitive fractionation produced by precipitation of quartz and sorption of coal. Elevated Ge concentrations and/or δ 74 Ge values of some chert, limestone, sandstone, and claystone samples may be attributed to the mixing with Ge-rich organic matter. Furthermore, similar to the fractionation of Zn, Cd and Hg isotopes observed between refinery dust or gas and slag, high temperature coal combustion also fractionates Ge isotopes, with the Ge isotopic compositions of soot being distinctly lighter (up to 2.25 per mil) than those of cinder. The distinct enrichment of potential hazardous elements (i.e., Pb, Cd, and As) and Ge in soot after coal combustion, as well as the common enrichment of Ge in sulfide minerals (e.g. sphalerite), highlights the possibility of using Ge isotopes as useful tracers of sources of heavy metal pollution caused by high temperature industrial processes (coal combustion and Pb-Zn refining) in the environment.

Determination of As and in mineral waters by fast sequential continuous flow hydride generation atomic absorption spectrometry.

In this study, a novel analytical method which consists of a combination of Fast Sequential Flame Atomic Absorption Spectrometry (FS-FAAS) and Continuous Flow Hydride Generation Atomic Absorption Spectrometry (CF-HGAAS) is proposed. The method developed was employed for the sequential determination of As and Sb at sub-μg L-1 levels in bottled mineral waters. A strong enhancement in the analytical throughput was obtained when compared with the traditional mono-element CF-HGAAS with a quartz tube atomizer (QTA). Variables which would affect the method performance such as Ar flow rate, HCl and NaBH4 concentrations as well as delay and integration time were optimized. A flame atomic absorption spectrometer working in fast sequential mode was used in all experiments. After just 20 s of read delay, As and Sb were sequentially determined in 6 s (3 s each element). A 26-2 fractional factorial design was employed for studies of potential interferents with transition metals that could be present in mineral water samples. Limits of detection obtained for As and Sb were 0.15 and 0.14 μg L-1, respectively. The accuracy of the proposed method was checked by the use of 2 certified reference materials: Trace elements in water (NIST 1643e) and Trace metals in drinking water (HPS TMDW). Good agreement between certified and found concentrations was observed. Finally, As and Sb were determined in commercial bottled mineral water samples. Adequate sensitivity, high throughput and minimization of reagents and sample consumption are the attractive features of this new method.

Continuous flow hydride generation laser induced fluorescence spectrometry for trace determination of lead in water and sediment samples

Continuous flow hydride generation coupled with laser induced fluorescence spectrometry (HG-LIF) has been used for the determination of Pb in aqueous samples. Lead hydride is generated in K3Fe(CN)6-HCl medium using NaBH4 as the reducing agent. Parameters such as acidity and the concentrations of oxidising and reducing agents have been studied in order to obtain the highest sensitivity. Laser excitation of Pb has been performed at 283.306 nm and fluorescence has been detected at 365 nm and 405.8 nm. The limit of detection calculated for the optimised conditions (1% K3Fe(CN)6 in 0.3% Oxalic Acid, 0.055 mol L−1 HCl, 1% NaBH4 in 0.1% NaOH) is 0.3 ng mL−1. However, a significant Pb background was observed for blank measurements, which degraded the limit of detection. The limit of detection that is estimated for a Pb free blank was determined by detuning the laser to a wavelength of 282.806 nm and was found to be 0.45 pg mL−1. Method repeatability is 3.5% RSD at the 10 ng mL−1 level. The accuracy of this method has been evaluated by analysis of a water reference material. The results obtained for a multielement standard determined using the HG-LIF approach have been found to be in agreement with those obtained by using a comparison ICP-AES approach. The HG-LIF approach has been applied to the measurement of Pb in a contaminated sediment sample material. The results of this study demonstrate that a small tunable laser system combined with hydride generation sample introduction can be used to measure Pb with high sensitivity, precision and selectivity in different sample matrices.

Development of a continuous flow hydride generation laser-induced breakdown spectroscopic system: Determination of tin in aqueous environments

The design, construction and optimization studies of a continuous flow hydride generation laser-induced breakdown spectroscopic system, HG-LIBS, for the determination of tin in aqueous environments is presented. Optimization of the Laser Induced Breakdown Spectroscopy (LIBS) signal with respect to carrier gas flow rate, analyte, acid (HCl) and reductant (NaBH 4) concentrations and flow rates was performed by using spectral emission intensity from the neutral Sn(I) line at 284.0 nm under atmospheric pressures. With flow rates of 5.0 mL/min for NaBH 4 and 2.5 mL/min for HCl, optimum NaBH 4 and HCl concentrations were determined as 2.0% (w/v) and 1.0% (v/v), respectively. The hydride generation efficiency of the system was tested for tin hydride, stannane (SnH 4), by inductively coupled plasma mass spectrometer (ICP-MS). It was found that higher than 99% of the analyte was released into the gaseous phase. Upon optimization, the minimum detectable Sn concentration was found as 0.3 mg/L in water samples. That corresponds to more than two orders of increase in sensitivity compared to methods that employ common sample introduction techniques in liquids analysis by LIBS. Over 90% recoveries were obtained from spiking experiments with river, tap and drinking water samples. Results illustrate potential use of the continuous flow HG-LIBS system for monitoring of Sn concentrations in aqueous environments.