Electrochemical hydride generation for the determination of hydride forming elements by atomic fluorescence spectrometry

The determinations of As, Bi, Ge, Sb and Se were performed by atomic fluorescence spectrometry following their electrochemical hydride generation. An electrochemical hydride generator based on a screw-thread seal arrangement, working in a continuous flow mode was used. The effects of cathode material, shape and area of material, catholyte, sample flow rate, applied current, catholyte solution concentration and interference of transition metals on signal intensity were studied. Five kinds of materials including lead, graphite, copper, tungsten and platinum with different shapes were tested as cathode materials. The signal obtained from a 3-dimensional electrode was higher than that from a 2-dimensional electrode under the same conditions. The signal intensity of Ge in HNO₃ medium within a narrow concentration range of 0.05–0.10 mol L^{− 1} was stronger than that in other acidic medium, such as HCl and H₂SO₄. However, the signal intensity of Ge was rapidly decreased with HNO₃, HCl and H₂SO₄ concentration increasing, and then reached approximately zero. In general, limits of detection and a precision were improved using a graphite cathode in H₃PO₄ medium. The analysis of the reference materials showed good agreement with the certified values for As, Bi, Ge, Sb and Se. The method was successfully applied in the determination of As, Bi, Ge, Sb and Se in traditional Chinese medicine samples.     

Characterisation of a hydraulic high-pressure sample introduction assisted flow injection-inductively coupled plasma time-of-flight mass spectrometry system and its application to the analysis of biological samples

A flow injection (FI) method was developed using hydraulic high-pressure nebulization as a sample introduction system, coupled to inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of 19 elements. The operating conditions of the system (analyte flow rate, heating and cooling temperatures of the desolvation module, carrier gas flow rate) for the simultaneous determination of 19 analytes were optimised. The optimum parameters of the sample introduction system were found to be 1.4 ml min⁻¹ and 1.35 l min⁻¹ for the analyte solution and nebulizer flow rates, respectively. A compromised condition for heating and cooling stage temperatures of 170 and −5 °C was chosen. The detection limits were compared to those obtained by using ICP-TOFMS with alternative sample introduction techniques e.g. conventional nebulization, flow injection chemical hydride generation (FI-CHG) and the obtained results were comparable or better than those resulting from alternative sample introduction. Applying the optimised conditions the simultaneous determination of Ag, As, Ba, Cd, Co, Cu, Ga, In, Li, Mn, Mo, Pb, Sb, Se, Sn, Sr, Tl, V and Zn was carried out. Absolute detection limits (3σ) in the range of 2-750 pg and precision between 0.5 and 9.6% from five replicate measurements of 10 ng ml⁻¹ multielemental sample solutions were achieved by using a 200 μl sample loop. The developed method was applied for the analysis of certified reference materials of biological origin (TORT-2 “Lobster Hepatopancrease”, BCR-422 “Cod Muscle” and IAEA MA-B-3/TM “Fish Homogenate”), and the results showed good agreement with the certified values.     

Flow injection on-line preconcentration coupled to hydride generation atomic fluorescence spectrometry for ultra-trace amounts of cadmium determination in seawater

A simple flow injection on line separation and preconcentration system coupled to hydride generation atomic fluorescence spectrometry (HG-AFS) was developed for ultra-trace cadmium determination in seawater. With the sample pH kept at 3.0, the preconcentration of cadmium on the inner walls of the knotted reactor was carried out based on the retention of cadmium complex with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one. A 0.2 mol L⁻¹ HCl was introduced to elute the retained analyte complex and merge with KBH₄ solution for HG-AFS detection. Under the optimal experimental conditions, an enhancement factor of 12 was obtained with a sample consumption of 12.0 mL. The limit of detection was 3.2 ng L⁻¹ with a sample frequency of 24 h⁻¹. The developed method was validated by the analysis of cadmium in certified reference materials, and was applied to the determination of cadmium in four seawater samples with R.S.D. of around 10%. Correspondence: Hong Wu, Department of Chemistry, Xuzhou Normal University, Xuzhou 221116, P.R. China     

Optimization of selenium determination in plant samples by hydride generation and axial view inductively coupled plasma atomic emission spectrometry

The use of hydride generation coupled with axial view inductively couple plasma atomic emission spectrometry was presented for the determination of selenium in plant samples. The chemical factors affecting potentially the hydride generation efficiency (hydrochloric acid, sodium borohydride and sodium hydroxide concentrations) were assessed through investigation of chemical interference, accuracy and repeatability. The accuracy of measurements was not affected by elements present in high concentration in the plant matrix (K, Ca, Mg, and P). No interference was also observed with transition metals. Using a real sample (maize) with standard additions, decreases of recoveries were sometimes observed for 0.1% (m/v) NaOH, and attained 13.8% in the most unfavourable case. The final accuracy of the method was verified by using two certified reference materials: CRM 402 (white clover) and CRM 279 (sea lettuce). No statistically significant differences were obtained between the measured concentrations and the certified values. The optimized method was found sensitive (detection limit 0.15 μg l⁻¹), reliable and repeatable (R.S.D. between 1.3% and 4.0%).     

Electrochemical hydride generation atomic absorption spectrometry for determination of cadmium

An electrolytic hydride generation system for determination of another hydride forming element, cadmium, by catholyte variation electrochemical hydride generation (EcHG) atomic absorption spectrometry is described. A laboratory-made electrolytic cell with lead-tin alloy as cathode material is designed as electrolytic generator of molecular hydride. The influences of several parameters on the analytical signal have been evaluated using a Plackett-Burman experimental design. The significant parameters such as cathode surface area, electrolytic current, carrier gas flow rate and catholyte concentration have been optimized using univariate method. The analytical figures of merit of procedure developed were determined. The calibration curve was linear up to 20 ng ml⁻¹of cadmium. The concentration detection limit (3σ, n = 8) of 0.2 ng ml⁻¹ and repeatability (relative standard deviation, n = 7) of 3.1% were achieved at 10.0 ng ml⁻¹. It was shown that interferences from major constituents at high concentrations were significant. The accuracy of method was verified using a real sample (spiked tap water) by standard addition calibration technique. Recovery of 104% was achieved for Cd in the spiked tap water sample.     

Determination of As, Sb, Bi and Hg in water samples by flow-injection inductively coupled plasma mass spectrometry with an in-situ nebulizer/hydride generator

A simple and very inexpensive in-situ nebulizer/hydride generator was used with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of As, Sb, Bi and Hg in water samples. The application of hydride generation ICP-MS alleviated the sensitivity problem of As, Sb, Bi and Hg determinations encountered when the conventional pneumatic nebulizer was used for sample introduction. The sample was introduced by flow injection to minimize the deposition of solids on the sampling orifice. The elements in the sample were reduced to the lower oxidation states with L-cysteine before being injected into the hydride generation system. This method has a detection limit of 0.003, 0.003, 0.017 and 0.17 ng ml⁻¹ for As, Bi, Sb and Hg, respectively. This method was applied to determine As, Sb, Bi and Hg in a CASS-3 nearshore seawater reference sample, a SLRS-2 riverine water reference sample and a tap water collected from National Sun Yat-Sen University. The concentrations of the elements were determined by standard addition method. The precision was better than 20% for most of the determinations.     

Ultratrace-level radium-226 determination in seawater samples by isotope dilution inductively coupled plasma mass spectrometry

An improved and novel sample preparation method for ²²⁶Ra determination in liquid samples by isotope dilution inductively coupled plasma sector field mass spectrometry using laboratory-prepared ²²⁸Ra tracer has been developed. The procedure involves a selective preconcentration achieved by applying laboratory-prepared MnO₂ resin followed by cation exchange chromatographic separation. In order to completely eliminate possible molecular interferences, medium mass resolution (R = 4,000) combined with chemical separation was found to be a good compromise that enhanced the reliability of the method. The detection limit of 0.084 fg g⁻¹ (3.1 mBq kg⁻¹) achieved is comparable to that of the emanation method or alpha spectrometry and is suitable for low-level environmental measurements. The chemical recovery of the sample preparation method ranged from 72 to 94%. The proposed method enables a rapid, accurate and less labor-intensive approach to routine environmental ²²⁶Ra determination than the radioanalytical techniques conventionally applied.     

Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge,As, Cd,Sb, Hg and Bi in cosmetic lotions

A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v l-cysteine, 0.5 μg mL⁻¹ Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng  g⁻¹ for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.     

Liquid chromatography with time-of-flight mass spectrometry for simultaneous determination of chemotherapeutant residues in salmon

Liquid chromatography with time-of-flight mass spectrometry (LC-TOF-MS) method has been developed for simultaneous confirmation by accurate mass measurement and quantitative determination of antibiotics (enrofloxacin, oxolinic acid, flumequine, erythromycin), fungicides (malachite green MG, leucomalachite green LMG) and parasiticide (emamectin benzoate) residues in edible portion of salmon. Confirmation of chemotherapeutant residues has been based on the system of identification points (IPs) established in the Commission Decision 2002/657/EC concerning the use of mass spectrometry (MS) techniques. A validation study on matrix is presented evaluating accuracy in terms of precision (λ_ppm 0.83-1.15) and trueness (0.22-0.70 Da). Limits of detection (LODs) and limits of quantification (LOQs) were in ranges of 1-3 and 3-9 μg/kg, below the maximum residue limits (MRLs) established in current EU legislation (100-200 μg/kg) for these chemotherapeutants. Considering the EU guidelines, decision limits (CCα) and detection capabilities (CCβ) were determined (ranges of 103-218 and 107-234 μg/kg, respectively) for authorised substances. For no authorised compounds (MG and LMG), LODs were 2 and 1 μg/kg, respectively, but exceed the MRPL (minimum required performance limit) established in the legislation which corresponds to the sum of MG and LMG (2 μg/kg). Acceptable intra-day and inter-day variability, in terms of relative standard deviation (R.S.D.) of the analytical method, were obtained (2-15%). Linearity was demonstrated from the LOQs of the analytes to 600 μg/kg (r > 0.9991). The method has involved an extraction procedure based on solid-liquid extraction (SLE) with recoveries higher than 80% for most target chemotherapeutants, with exception of enrofloxacin (40%).     

Determination of tin in soil by continuous hydride generation and inductively coupled plasma mass spectrometry

A method was investigated for the determination of Sn in soil samples by KOH fusion followed by continuous hydride generation coupled with inductively coupled plasma mass spectrometry (HG-ICP-MS). Sample solutions in 3.0 M HCl were mixed in line with a solution of 2.4% NaBH₄ and 0.25 M KOH to generate stannane gas. The mixture was delivered continuously to a gas/liquid separator and the stannane gas was introduced into a Perkin-Elmer Sciex Elan 6000 ICP-MS for concentration measurements. A method detection limit of 0.45 mg/kg was sufficient for Sn levels commonly found in soil samples. Sn concentrations as low as 2.5 mg/kg were reproducibly measured in soil samples. Sample results by HG-ICP-MS agreed within ±17% relative difference to results by instrumental neutron activation analysis (INAA) and within ±6% relative difference to results by KOH fusion followed by inductively coupled plasma optical emission spectroscopy (ICP-OES).     

Multiple injection technique for the determination and quantitation of insulin formulations by capillary electrophoresis and time-of-flight mass spectrometry

This paper describes an efficient CE-UV-ESI-TOF/MS method for the determination and quantitation of intact insulin (INS) in a pharmaceutical formulation. The CE conditions were optimized to avoid the adsorption of proteins onto the capillary wall. Particular attention was paid regarding the choice of the internal standard (IS). A strategy based on multiple injections was selected and the methodology was validated according to international guidelines. The optimized method was applied with success to the analysis of INS formulations obtained from regular and parallel markets.     

Development of a new electrochemical hydride generator with tungsten wire cathode for the determination of As and Sb by atomic fluorescence spectrometry

A novel electrochemical hydride generator has been developed for the determination of As and Sb. This newly devised hydride generator is constructed from a flowing electrolytic cell, in which the tungsten wire is selected as cathode. Compared with some cathode material usually used in electrochemical hydride generator, the tungsten cathode is of better interference tolerance, corrosion-resistant and longer working time. The characteristics of the cathode material, hydride generating efficiency and interferences of concomitant have been studied in detail. The detection limits (3σ) of As and Sb in sample solution were 0.10 μg L⁻¹ and 0.15 μg L⁻¹, the precisions for 11 replicate measurements of 20 μg L⁻¹ As and Sb were 1.3% and 1.7%. The electrochemical hydride generator coupled with atomic fluorescence spectrometry has been applied to the determination of total As and Sb in tobacco samples.     

Design and application of a novel integrated electrochemical hydride generation cell for the determination of arsenic in seaweeds by atomic fluorescence spectrometry

An integrated electrochemical hydride generation cell, mainly composed of three components (a gas liquid separator, a graphite tube cathode and a reticulate Pt wire anode), was laboratory constructed and employed for the detection of arsenic by coupling to atomic fluorescence spectrometry. This integrated cell was free of ion-exchange membrane and individual anolyte, with the virtues of low-cost, easy assembly and environmental-friendly. Using flow injection mode, the sample throughput could come to 120 h⁻¹ attributed to the small dimension of the cathode chamber. The operating conditions for the electrochemical hydride generation of arsenic were investigated in detail and the potential interferences from oxygen or various ions were also evaluated. Under the optimized conditions, no obvious oxygen quenching effects were observed. The limit of detection of As (III) for the sample blank solution was 0.2 ng mL⁻¹ (3σ) and the relative standard deviation was 3.1% for nine consecutive measurements of 5 ng mL⁻¹ As (III) standard solution. The calibration curve was linear up to 100 ng mL⁻¹. The accuracy of the method was verified by the determination of arsenic in the reference materials GBW08517 (Laminaria Japonica Aresch) and GBW10023 (Porphyra crispata) and the developed method was successfully applied to determine trace amounts of arsenic in edible seaweeds.     

Simultaneous determination of major to ultratrace elements in geological samples by fusion-dissolution and inductively coupled plasma mass spectrometry techniques

A method has been developed for the simultaneous quantification of major to ultratrace elements in geological samples using quadrupole ICP-MS techniques. The sample preparation involves fusion with LiBO₂ and dilution in HNO₃-HF which allows complete decomposition of refractory minerals and quantification of the elements of interest. The effects of high Total Dissolved Solids (TDS) and Li in the solution are minimized using a matrix-tolerant interface and conditioning the instrument with LiBO₂ solution. The signal drift is moreover controlled using conventional internal standards and specific Drift Correction Standards (DCS). A key issue of the technique is the external calibration using selected Certified Reference Materials (CRM). Depending on the sample type and analytes of interest three optimized programmable modes are used sequentially: Standard, Collision Cell (CCT) and Kinetic Energy Discrimination (KED) mode. The method allows to quantify more than 40 elements in concentrations from tens-of-percent to <0.1 ppm levels during a single experiment. The method has been validated through the analysis of different CRMs with recovery factors of ca. 100% and typical 2σ errors of <10%.     

Rapid isolation of plutonium in environmental solid samples using sequential injection anion exchange chromatography followed by detection with inductively coupled plasma mass spectrometry

This paper reports an automated analytical method for rapid determination of plutonium isotopes (²³⁹Pu and ²⁴⁰Pu) in environmental solid extracts. Anion exchange chromatographic columns were incorporated in a sequential injection (SI) system to undertake the automated separation of plutonium from matrix and interfering elements. The analytical results most distinctly demonstrated that the crosslinkage of the anion exchanger is a key parameter controlling the separation efficiency. AG 1-×4 type resin was selected as the most suitable sorbent material for analyte separation. Investigation of column size effect upon the separation efficiency revealed that small-sized (2 mL) columns sufficed to handle up to 50 g of environmental soil samples. Under the optimum conditions, chemical yields of plutonium exceeded 90% and the decontamination factors for uranium, thorium and lead ranged from 10³ to 10⁴. The determination of plutonium isotopes in three standard/certified reference materials (IAEA-375 soil, IAEA-135 sediment and NIST-4359 seaweed) and two reference samples (Irish Sea sediment and Danish soil) revealed a good agreement with reference/certified values. The SI column-separation method is straightforward and less labor intensive as compared with batch-wise anion exchange chromatographic procedures. Besides, the automated method features low consumption of ion-exchanger and reagents for column washing and elution, with the consequent decrease in the generation of acidic waste, thus bearing green chemical credentials.     

Investigation of electrochemical hydride generation coupled to microwave plasma torch optical emission spectrometry for the determination of arsenic: analytical figures of merit,interference studies and applications to environmentally relevant samples

A continuous flow thin layer electrolysis cell with a Pt cathode in combination with a microwave plasma torch operated with Ar as working gas was used for the optical emission spectrometric determination of As with the hydride technique. Under the optimised conditions the limit of detection (3σ) in the case of the As(I) 228.81 nm emission line was 81 ng mL^?1. Especially the influence of the transition metals Cu(II), Fe(III) and Ni(II), of the hydride forming elements Sb(III), Se(IV) and Sn(II) and of Na on the determination of As was studied. Cu(II) was found to be the strongest interferent, as in the presence of 100 µg mL^?1 of Cu(II) the signal for 3 µg mL^?1 of As was reduced to 4% of the signal without interferent. Sn(II) and Sb(III) were found to yield an increase of the signal for As. L-cysteine and KI/ascorbic acid (1 : 1) at a concentration of 2% were found effective to reduce the interferences of Cu(II), Fe(III) and Ni(II). For a solution containing 3 µg mL^?1 of As and 100 µg mL^?1 of Ni(II) it was shown that in the presence of L-cysteine or KI/ascorbic acid the signal for As was 99% and 94% of the one without interferent, whereas it was only 43% without masking reagents. The procedure could be used for the determination of As in a digested coal fly ash standard reference material (NIST SRM 1633a®) with a certified value of 145 ± 15 µg g^?1 for As. A concentration of 131 ± 15 µg g^?1 was found. Additionally, As could be determined in two process water samples from a copper refinery. It was found that the amount of As determined with ECHG-MPT-OES agrees well with the values determined by FAAS and ICP-OES at the 0.02 and 1.6 g L^?1 level, respectively.     

On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials

We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6–21% for pressed pellets and 3–21% for fused solids were obtained from n = 3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches.     

顺序注射氢化物发生-原子荧光光谱法同时测定硒和砷的研究

建立了一种顺序注射氢化物发生-原子荧光光谱法测定试样中Se和As的方法,同时讨论了共存离子的干扰情况.在最佳实验条件下,Se和As的检出限分别为0.16和0.095 μg/L,加标回收率为92.4%～104.7%.     

Determination of trace elements in human serum by inductively coupled plasma atomic emission spectrometry with flow injection

An analytical method for the simultaneous determination of some trace elements (Au, Fe, Mg, Li, Sr, Zn) in human serum by inductively coupled plasma atomic emission spectrometry (ICP-AES) with flow injection is described. Physical interference caused by the change of sample viscosity is discussed. When 100 μl of serum was injected, the relevant recoveries of > 99% for Li, > 98% for Cu and Mg, > 95% for Fe were obtained for an NIST SRM with R.S.D. > 1.3% using optimized flow injection parameters. The prepared lyophilized control serum for routine analysis in clinical laboratories was analyzed and verified for the validity of the technique employed in this experiment using NIST SRM 909 as a primary reference material.     

等离子体发射光谱法测定矿山水样中硫酸盐的研究

水质中硫酸盐的测定方法很多,但对于成分复杂且盐分很高的矿山水样,传统方法操作繁琐且不环保,本文建立了等离子体发射光谱法测定矿山水样中硫酸盐的方法,样品采用硝酸和盐酸进行加热消解后既可去除硫化物,降低水质的黏度,又可实现多元素同时测定。该方法检出限为0.03mg/L,相对标准偏差为0.1～0.4%(n=6),方法具有方便,快捷,检出限低,精密度、准确度高且线性范围广的优点。