Hydride Generation Process Research Articles

Speciation analysis of Sb(III) and Sb(V) by hydride generation-smartphone colorimetric system using metal organic framework as substrate

A portable and easy-use analytical system was established for speciation analysis of inorganic antimony (Sb(III) and Sb(V)) based on hydride generation-smartphone colorimetric method. Metal organic framework (Ag-MOF) was served as substrate here. Sb(III) was transformed to stibine (SbH3) during hydride generation process, SbH3 was then transported and reacted with Ag-MOF in reaction bottle, leading to its color turn to black from light gray, the variance was then distinguished by visual and smartphone mode. A detectable limit as low as 0.01 μg/mL can be readout by smartphone mode. Besides, citric acid was used as masking reagent for speciation analysis of Sb(III) and Sb(V). Several real environmental water samples were further detected using this colorimetric system and recoveries for those samples were 90–106 %. The potential application of this method for rapid and field analysis of inorganic antimony was further demonstrated by analysis of a certified reference water sample (BWZ6657-2016B).

In situ formation of silver nanoparticles via hydride generation: A miniaturized/portable visual colorimetric system for arsenic detection in environmental water samples

A miniaturized/portable visual colorimetric system based on hydride generation headspace solid phase extraction (HG-HS-SPE) was proposed for arsenic detection by naked eyes. As(III) was transformed into AsH3via hydride generation process, the volatile AsH3 was introduced into reaction bottle and reacted with AgNO3 subsequently. Silver nanoparticles (Ag NPs) were generated in situ, resulting in the color changed from white to black, it could be readout by naked eyes or a smartphone application (color extraction, for RGB readout). The interferences from 9 common ions and 10 conventional hydride generation elements were discussed, the results demonstrated that the proposed method exhibit a good anti-interference. The proposed visual colorimetric method was further applied to seven water samples and their spiked samples, and a certified reference water sample (GBW08605) for demonstrating its accuracy and applicability.

A simple and rapid head space-single drop microextraction-‘spectro-pipette’ (HS-SDME-SP) method for the on-site measurement of arsenic species in natural waters

Arsenic (As) is a ubiquitous element in the environment while its toxicity and chemical properties are highly associated with its chemical form. High quality As speciation data in environmental matrices are thus desirable for understanding its biogeochemistry. Here we present a simple and novel head space-single drop microextraction-spectro-pipette (HS-SDME-SP) method for the on-site measurement of As species in natural waters. Arsine was generated and separated from the sample matrix by borohydride-based hydride generation, which was further extracted into a stable, hanging 5 μL microdroplet on the tip of a spectro-pipette. With the spectro-pipette, the microvolume of extractant is easily handled while gas–liquid absorption, redox and chromogenic reactions and in situ absorbance measurement can be carried out in a single step. The speciation analysis of As(III) and As(V) was achieved by utilizing their different pH requirement for reduction and arsine generation in the hydride generation process. Although the proposed method is a simple sensor based assay, it is sensitive, robust and reliable; the limit of detection (3 × S/N) was 0.1 nM, RSDs for 25 nM As(III) were < 2.0% (n = 10) and results were comparable with the commonly used hydride generation atomic fluorescence spectrometry (HG-AFS) method and in good agreement with two certified reference materials (surface freshwater and seawater). The proposed method is easy to operate, the device is light and portable (1.1 kg) and is practical for the measurement of trace inorganic As species in the field.

Development of a microfluidic membraneless vaporization flow system for trace analysis of arsenic.

A new design of a membraneless vaporization (MBL-VP) unit coupled with a specific flow system is presented for the determination of arsenic at trace levels using a hydride generation process. The MBL-VP unit contains two concentric conical reservoirs, with the outer cone selected as the donor reservoir. The volume of the outer donor reservoir is thereby greater than the acceptor volume, necessary for holding sufficient sample and reagents for the generation of arsine gas by reaction between As(iii) and sodium borohydride under acidic conditions. The arsine gas diffuses into the narrow headspace and is absorbed by an aliquot of 150 μL of mercuric chloride acceptor solution. The resulting reaction produces hydronium ions which is monitored by the absorbance change at 530 nm of the methyl orange indicator added in the acceptor solution. To decrease the detection limit, the aspiration and removal of the donor plug, comprising the sample, borohydride and acid, into and out of the donor cone are repeated several times, while the acceptor solution is kept unchanged. As a result, analysis of arsenic was achieved in the range of 10 to 100 μg L-1 with a detection limit of 8 μg L-1. Application to surface water was investigated. Percent recoveries of spiked surface water samples were in the range of 94-110%. For comparison of total arsenic (As(iii) and As(v)), the results obtained from the developed method are not statistically different from the ICP-OES method.

In situ preconcentration of lead by dielectric barrier discharge and its application to high sensitivity surface water analysis

A novel dielectric barrier discharge (DBD) reactor was utilized to in situ enrich and atomize lead in gas phase. The structure of DBD reactor was optimized to broaden the acidity window of plumbane generation from 1% to 3.5%, bringing better analytical stability and practicability deriving from hydride generation process. For the first time DBD proved effective in lead preconcentration and broadening the acidity window of plumbane generation. Pb can be trapped quantitatively (~100%) on the quartz surface of DBD tube under O2-containing atmosphere and released (~100%) under H2-containing atmosphere. The absolute detection limit (LOD) for Pb was 4.1 pg (injection volume = 1.2 mL), and the linear (R2 > 0.999) range was 0.05–100 μg/L. The results were in good agreement with those of certified reference materials (CRMs), and spiked recoveries for surface water samples were 99–104% with 2–8% RSD. By gas phase analyte enrichment, the proposed method reduced absolute LOD by 10 times. It was deduced that plumbane was changed to lead oxide species trapped on the quartz tube surface and then released, and transported in form of atoms to the detection zone.

In–spray chamber hydride generation by multi–mode sample introduction system (MSIS) as an interface in the hyphenated system of high performance liquid chromatography and inductivity coupled plasma optical emission spectrometry (HPLC/HG–ICP–OES) in arsenic species determination

The paper presents a new usage of a commercial in–spray chamber hydride generator, Multi–mode Sample Introduction System (MSIS) as a connector of high pressure liquid chromatography and inductivity coupled plasma optical emission spectrometry (HPLC/HG–ICP–OES). This hyphenated technique was applied in a determination of inorganic and organic arsenic species. The optimization of a hydride generation process in MSIS and a chromatographic separation (using anion–exchange HPLC column with phosphate buffer as a mobile phase) were carried out compositely. The method allowed to determine three arsenic forms, As(III), As(V) and dimethylarsinate (DMA) within 400s of a single analysis. The obtained limits of detection (LODs) were 2.08 μg L−1 for As(III); 6.97 μg L−1 for As(V); 6.15 μg L−1 for DMA and precision 2.7%, 4.8%, and 5.7%, respectively, for 100 μg L−1. The described method was used for environmental and food samples analyses.

A digitally controlled rotating field plasma source for analytical spectrometry

A highly flexible technology for constructing plasma sources based on the rotating field concept and the digitally controlled modulation of plasma heating is presented with the plasma source operating at audio and ultrasonic frequency adjustable in the 6–100 kHz range and powered in the 50–250 W range. The device allows for the production of non-stationary plasma discharge sustained by a rotating electric field produced within 5 electrodes positioned in the plane around the axis, while the plasma is temporarily stretched between at least two electrodes. A stable symmetrical low-flow helium discharge is formed at atmospheric pressure operating at total gas consumption of 100–1500 mL min−1 and it is self-igniting. The plasma fundamental parameters can be easily controlled in the wide range including He excitation temperature, OH rotational temperature and electron number density between 2200 and 3300 K, 850 and 1600 K, and 0.6 and 2.0 × 1014 cm−3, respectively. Therefore, the excitation power of the source may be controlled by variations of the pulse width, frequency, commutation mode and gas flow rate. The device is shown to be useful for atomic emission spectrometric determination of hydride forming elements and mercury at the ng mL−1 level. The excess of hydrogen produced in the hydride generation process can be tolerated by the helium plasma. Also, the plasma can be stably operated with argon, air and nitrogen.

Computational Modelling of the Hydride Generation Reaction in a Tubular Reactor and Atomization in a Quartz Cell Atomizer

In this study, we present a model whereby the centre of the atomization channel is shown to be the optimal location for the spectrometric data acquisition in a quartz cell atomizer. The study aims to explore the hydride generation technique which is normally coupled with efficient thermal source to apply determination of heavy metals in water samples via spectrometric analysis. The arsenic hydride generation process and the atomization of the generated hydride in a quartz cell atomizer were studied analytically as model case studies. The hydride generation (HG) process was analyzed by adopting two hypotheses, the nascent hydrogen and formation of intermediate hydroboron species, where the results based on the second hypothesis are found to be more realistic for design purposes. Moreover, the release of the generated hydride from the liquid phase and their transport to the gas phase is simulated in a helical tubular section, in which the actual tubular section length required for separation is deduced. The analytical results have been verified experimentally by measuring the signal intensity for the free arsenic atoms against several reaction tube lengths, in which increasing the tubular section length from 12 cm to 100 cm results in signal amelioration by no more than 6.6%. Furthermore, the atomization of the hydride and the distribution of the generated free atoms are deduced in two configurations of tubular quartz atomizers. The results obtained from both studied cases illustrate that a high concentration of the free analyte atoms is generated in the first part of the atomization channel, saturates to a maximum in a position at the atomizer centre, and dissipates at the inside wall of the tubular atomizer before reaching the atomizer outlet edge, which is found to be in total agreement with the current understanding of atomization mechanism in tubular atomizer and emphasizes the fact that the centre of the quartz cell atomizer is the best location for the spectrometric data acquisition.

Speciation of inorganic arsenic in a sequential injection dual mini-column system coupled with hydride generation atomic fluorescence spectrometry

The separation and speciation of inorganic arsenic(III) and arsenic(V) are facilitated by employing a novel sequential injection system incorporating two mini-columns followed by detection with hydride generation atomic fluorescence spectrometry. An octadecyl immobilized silica mini-column is used for selective retention of the complex between As(III) and APDC, while the sorption of As(V) is readily accomplished by a 717 anion exchange resin mini-column. The retained As(III)–PDC complex and As(V) are effectively eluted with a 3.0 mol L −1 hydrochloric acid solution as stripping reagent, which well facilitates the ensuing hydride generation process via reaction with tetrahydroborate. With a sampling volume of 1.0 mL and an eluent volume of 100 μL for both species, linear ranges of 0.05–1.5 μg L −1 for As(III) and 0.1–1.5 μg L −1 for As(V) are obtained, along with enrichment factors of 7.0 and 8.2, respectively. Precisions of 2.8% for As(III) and 2.9% for As(V) are derived at the concentration level of 1.0 μg L −1. The practical applicability of the procedure has been demonstrated by analyzing a certified reference material of riverine water (SLRS-4), in addition to spiking recovery in a lake water sample matrix.

Hydride generation activity of arsenosugars and thioarsenicals

The major arsenosugar compounds have been reported to be hydride-generation-active, however to a lesser extent in comparison with the inorganic arsenicals. We report here for the first time the identity and quantity of the volatile arsenicals generated by As-sugar-SO(3), As-sugar-SO(4), dimethylarsinoyl acetic acid and dimethylarsinoyl ethanol. Only one major volatile compound was identified for all four compounds studied: dimethylarsine. This means that the As-C bond to the longer carbon chain was cleaved during the hydride-generation process. Theoretical calculations at the RHF/6-31G(d,p) ab initio level confirm that this As-C bond is much weaker than the As-CH(3) bonds. Furthermore, it was revealed that the sulphur analogue of dimethylarsinic acid (DMAS ) is hydride-generation-active at pH 7 in contrast to dimethylarsinic acid, despite the fact that arsenic is also pentavalent. This has been substantiated by the calculation of the change in susceptibility of the arsenic towards nucleophilic attack when oxygen is replaced by sulphur. Hence, DMAS can easily be mistaken for a trivalent arsenic species.

Application of a wall-stabilized argon plasma arc for the determination of some volatile hydride-forming elements

Volatile hydrides of As, Se, Sb and Sn, produced by a continuous manifold hydride generator, have been swept with argon and injected into the plasma of home-made direct current wall-stabilized argon plasma arc via one of its stabilizing segments. The arc burns in argon with an arc current of 20 A and a cathode-anode voltage of 40 V. Measurements were carried out using a 1 m focal length computer-controlled monochromator (Jobin Yvon 1000R) equipped with a holographic grating having 2400 grooves mm − 1 . Optimal values of the experimental variables that give the highest value of intensity ratio of line-to-background were determined. These are: plasma gas flow rate 1.0 l min − 1 , carrier gas flow rate 0.35 l min − 1 for As and Sb and 0.6 l min − 1 for Se and Sn, concentration of nitric acid used for acidification of the sample 2 M for As and Sb, 0.5 M for Se and 0.1 M for Sn and sodium borohydride concentration: 1.5% for As and Se and 2% for Sb and Sn. Chemical interference of some transition elements that affect the hydride generation process and a trial to mask their interference effect were investigated. Calibration curves were linear and limits of detection calculated on the base of 3 σ of the background were found to be as low as 3.9, 6.8, 9.8 and 13.2 ng ml − 1 for As, Se, Sb and Sn, respectively. Finally, the analytical applicability of the arc device was tested by the determination of As in four lake sediment samples, LKSD 1, LKSD 2, LKSD 3 and LKSD 4, of the Centre for Mineral and Energy Technology, Ottawa, Ontario, Canada, which have been analyzed for As using atomic absorption spectrometry (AAS). The results were in good agreement with those obtained by AAS.

Effect of operating conditions on excitation temperature and electron number density in axially-viewed ICP-OES with introduction of vapours or aerosols

The combined effect of the power and the carrier gas flow rate on excitation temperature, electron number density, ionic-to-atomic line intensity ratios and departure from local thermal equilibrium has been studied in an axially-viewed plasma with introduction of different amounts of wet aerosols, partially desolvated aerosols or dry vapours, according to empirical modelling and experimental design methods. Under robust conditions (1500 W and a carrier gas flow rate of 0.7–0.85 L min−1), an increase in water loading led to an improvement in the plasma excitation properties, while desolvation caused degradation. In contrast, under non-robust conditions, the plasma was no longer able to tolerate an increase in water loading and desolvation resulted in an improvement in the plasma characteristics. The hydrogen formed during the hydride generation process significantly improved the plasma excitation properties, regardless of the conditions. In this instance, the plasma characteristics were primarily affected by the reductant concentration, which determined the amount of hydrogen generated, and by the carrier gas flow rate, which controlled its residence time within the plasma. In contrast, there was no relevant change in the plasma excitation conditions due to systematic variation of HCl concentration from 0.1 to 6 M.

Arsenic speciation in water samples containing high levels of copper: removal of copper interference affecting arsine generation by continuous flow solid phase chelation

A simple continuous flow method is proposed to eliminate copper interference in arsenic speciation by hydride generation, based on the selective retention of this interfering ion in an iminodiacetate chelating resin previous to the hydride generation process. The arsines generated were cold trapped and measured by ICP/OES. The proposed method allows about 98% of the copper present in the samples to be removed. Minor co-retention of As(V) was observed as a result of electrostatic interaction between the arsenate anion and the nitrogen of the iminodiacetate group of the chelating resin Muromac A-1, the charge distribution of which is modified when copper is chelated. The species As(III), MMA and DMA were not retained in the microcolumn, probably because these species are mainly in the molecular form at the working pH value (4.5). In synthetic samples containing 50 microg l(-1) of each arsenic species together with 100 mg l(-1) copper, the recoveries obtained were: As(V) 97.6%, As(III) 100%, MMA 99.8%, and DMA 99.9%. The method was applied to arsenic speciation in river water samples containing high levels of copper.

Flow injection electrochemical hydride generation of hydrogen selenide on lead cathode: critical study of the influence of experimental parameters.

A flow injection system for the determination of selenium by electrochemical hydride generation and quartz tube atomic absorption spectrometry is described. The generator consists of an electrolytic flow-through cell with a concentric arrangement and a packed cathode made of particulated lead. The influences of sample flow rate, carrier gas flow rate and electrolysis current on the hydrogen selenide generation have been critically studied. Both sample flow rate and electrolysis current play important roles in the efficiency of the hydride generation process. A characteristic mass of 2.4 ng and a concentration detection limit of 17 microg l(-1) were obtained for a sample volume of 420 microl.

Spectroscopic characterization of low power argon microwave-induced plasma with gaseous species produced from ethanol–water solutions in continuous hydride generation process

Low power microwave-induced argon plasma generated by resonant TE 101 rectangular cavity was investigated upon introduction of volatile species formed in the reaction with sodium tetraborohydrate(III) in hydrochloric acid–ethanol solution. The molecular emission bands of OH and CH were used for rotational temperature ( T rot) determination, while the atomic emission lines of Ar, H and Sb were applied for excitation temperature ( T exc) measurement. Assuming a Boltzmann distribution, the temperatures were calculated with the aid of the least squares method. Electron number density ( n e) derived from Stark broadening of the H β line was found to be between 2.5×10 15 and 0.57×10 15 cm −3. The detection limits (DL) were determined for Hg and Sb. The influence of ethanol concentration in analyte solution and microwave power on measured parameters, was investigated. The results showed that T rot(OH) increased from 2970 to 3820 K while T rot(CH) decreased from 6100 to 4540 K with ethanol concentration in the solution, ranging from 10 to 90%. Under the same experimental conditions the excitation temperature for Ar, H and Sb varied in the following ranges: 5670–4800, 6190–3950 and 10500–7390 K, respectively. It was observed that element DL were significantly influenced by the presence of ethanol in the sample solution. The DL values for Hg and Sb were, as follows: 0.5–11 and 5.3–35 μg l −1, respectively.

On the transport of some metals into inductively coupled plasma during hydride generation process

Transport process of Ca, Cd, Co, Cr, Cu, Fe, Mn, Mg, Ni, Zn and Ti during continuous flow hydride generation in the system with phase separation was investigated using inductively coupled plasma atomic emission spectrometry. The effect of HCl and HNO 3 (for concentrations from 0.01 to 5.0 mol l −1) and arsenic on transport efficiency of the metals into plasma was examined. It was observed that not only Cd but also Cu transport in a form of volatile species was significant. The present study also indicated the formation of Co, Cr, Fe and Ni volatile species during hydride generation reaction. Possibility of spectral interferences between Cd, Cu and Fe lines on the one side and As and Bi lines on the other side was analysed and discussed.

Antimony biomethylation by Scopulariopsis brevicaulis: characterization of intermediates and the methyl donor

The filamentous fungus Scopulariopsis brevicaulis biomethylates inorganic antimony(III) compounds to trimethylstibine, that can be detected in culture headspace gases. Dimethylantimony and trimethylantimony species have been detected in the medium of these cultures, but the origin of these species was controversial. We now show that the dimethylantimony species is a true intermediate on the pathway to trimethylstibine (rather than arising from trimethylstibine oxidation or as an analytical artifact) because no dimethylantimony species are formed on trimethylstibine oxidation, as determined by using HG–GC–AAS. Furthermore, the dimethylantimony and trimethylantimony species can be separated, by using anion exchange chromatography, and so the dimethylantimony species is not an analytical artifact, formed during the hydride generation process. The antimony biomethylation mechanism was further probed by measuring incorporation of the methyl group, from 13 CD 3 - l-methionine and CD 3- d-methionine, into methylantimony species and, for comparison, into methylarsenic species. The percentage incorporation of the labeled methyl group into methylarsenic and methylantimony species was not significantly different. The incorporation from 13 CD 3 - l-methionine was 54% and 47% for antimony and arsenic, respectively. The incorporation from CD 3- d-methionine was 20% and 16% for antimony and arsenic, respectively. It appears that the biomethylation of arsenic and antimony occur by very similar, perhaps identical, mechanisms.

The effect of six reaction media on the determination of bismuth at trace levels in environmental samples by hydride generation and inductively coupled plasma-atomic emission spectrometry

An investigation was carried out to explore the effect of hydrochloric, tartaric, citric, oxalic, acetic and sulfosalicylic acids on the hydride generation of Bi at trace levels in a continuous flow system in conjunction with inductively coupled plasma atomic emission spectrometric detection. The operating conditions (chemical and physical parameters) and the concentrations of the acids studied were evaluated for the efficient generation of BiH3 (bismuthine). Kinetic information about the decomposition process of BiH3 was also obtained. Analytical figures of merit including detection limits, precision and linear dynamic ranges are given for the six acids employed. The detection limits for Bi ranged between 0.3 and 0.7 µg l–1 depending on the acid used to generate BiH3. Compared with conventional continuous nebulization, the present coupling gives a sensitivity increase of approximately two orders of magnitude. The interfering effect of transition metals (Cd, Co, Cu, Cr, Fe, Mn, Ni, Zn), other hydride-forming elements (As, Ge, Pb, Sb, Se, Sn, Te) and Hg on the Bi signal using the different acids studied was evaluated. Tartaric acid is the most suitable reaction medium, in terms of efficiency in the hydride generation process and in the control of interferences. The proposed method was applied to the determination of Bi in certified reference materials (fresh water, silicate) and real environmental samples (iron ore and coal fly ash).

Comparative study to evaluate the effect of different acids on the determination of germanium by hydride generation–inductively coupled plasma atomic emission spectrometry

A comparative study was performed to evaluate the effect of hydrochloric, tartaric, citric, oxalic, acetic and sulfosalicilic acids on the hydride generation of germanium at trace levels in a continuous flow system and inductively coupled plasma atomic emission spectrometry (ICP–AES) detection. The operating conditions (chemical and physical parameters) and the concentrations of the acids studied have been optimized for the generation of GeH 4 (germane). Analytical figures of merit including detection limits, precisions and linear dynamic ranges are given for the six acids employed. The detection limits for Ge ranged between 0.096 and 0.295 μg l −1 depending on the acid used to generate germane. Compared to a conventional continuous nebulization, the present coupling gives a sensitivity increase of a factor of approximately two orders of magnitude. The interferent effect of transition metals (Cd, Co, Cu, Cr, Mn, Ni, Zn), other hydride forming elements (As, Bi, Pb, Sb, Se, Sn, Te) and Hg upon Ge signal using the different acids studied were evaluated. Tartaric acid is the most suitable reaction medium, in terms of efficiency in the hydride generation process and in reduction of interferences. Besides, it allows for less strict control of the pH at which the generation of germane takes place. The proposed method was applied to the determination of Ge in coal fly ashes.

Characteristics of the atomic fluorescence signals of arsenic in speciation studies

The behaviour of the arsenic hydrides, generated after the speciation of AsIII (arsenite), MMAs (monomethylarsonate) and DMAs (dimethylarsinate), in an atomic fluorescence cell was investigated. The efficiency of the hydride generation process was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) after sampling the liquid drain of the gas–liquid separator and by a gas chromatograph with mass spectrometric detection (GC-MS) for the analysis of the sampling gas of the separator. The different concentrations at which the fluorescence signal reaches a maximum were determined for each As species.