Speciation of arsenic compounds in fish and oyster tissues by capillary electrophoresis-inductively coupled plasma-mass spectrometry

A capillary electrophoresis-inductively coupled plasma-mass spectrometric (CE-ICP-MS) method for the speciation of six arsenic compounds, namely arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine is described. The separation has been achieved on a 70 cm length x 75 microm ID fused-silica capillary. The electrophoretic buffer used was 15 mM Tris (pH 9.0) containing 15 mM sodium dodecyl sulfate (SDS), while the applied voltage was set at +22 kV. The arsenic species in biological tissues were extracted into 80% v/v methanol-water mixture, put in a closed centrifuge tube and kept in a water bath, using microwaves at 80 degrees C for 3 min. The extraction efficiencies of individual arsenic species added to the sample at 0.5 microg As/g level were between 96% and 107%, except for As(III), for which it was 89% and 77% for oyster and fish samples, respectively. The detection limits of the species studied were in the range 0.3-0.5 ng As/mL. The procedure has been applied for the speciation analysis of two reference materials, namely dogfish muscle tissue (NRCC DORM-2) and oyster tissue (NIST SRM 1566a), and two real-world samples.     

Roxarsone and transformation products in chicken manure: determination by capillary electrophoresis-inductively coupled plasma-mass spectrometry

The determination of the animal feed additive roxarsone (3-nitro-4-hydroxyphenylarsonic acid) and six of its possible transformation products (arsenite, arsenate, monomethylarsonate, dimethylarsinate, 3-amino-4-hydroxyphenylarsonic acid, and 4-hydroxyphenylarsonic acid) in chicken manure was investigated using capillary electrophoresis-inductively coupled plasma-mass spectrometry (CE-ICP-MS). Initial method development was conducted using ultraviolet (UV) detection for ruggedness and time efficiency. Separation of these seven arsenic species was effected using a 20 mM phosphate buffer at pH 5.7. The CE-ICP-MS limits of detection in terms of As for each of the species was in the low microg.L(-1) range, corresponding to absolute detection limits in the range 20-70 fg As (based on a 23 nL injection). Overall, the method developed in this study provides high selectivity and low limits of detection (1-3 microg.L(-1) or low-ppb, based on As), uses small sample volume (low nL), and produces minimal wastes.     

Investigation of Cr(III) hydrolytic polymerisation products by capillary electrophoresis-inductively coupled plasma-mass spectrometry

The development of a new method for the determination of Cr(III) hydrolytic polymerisation products using capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) is described. The results indicate that CE-ICP-MS can be used to separate and detect monomeric and polymeric Cr(III) species. The various species migrate through the capillary at a rate proportional to their equilibrium distribution, which is dictated by the solution pH, metal ion concentration and ageing period. In general, the data suggest that the relative mobility follows the order trimer>dimer>monomer. The experimentally determined speciation shows a good qualitative agreement with that described in the literature. Independent confirmation of the presence of polymeric Cr(III) species was performed by ionspray mass spectrometry.     

Fast speciation analysis of iodophenol compounds in river waters by capillary electrophoresis-inductively coupled plasma-mass spectrometry with off-line solid-phase microextraction

An analytical methodology for the fast separation and determination of iodophenol species in natural water samples was developed using capillary electrophoresis (CE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Based on the element-specific and highly sensitive detection provided by ICP-MS, the methodology has been applied to the analysis of 2-iodophenol, 4-iodophenol, and 2,4,6-triiodophenol. The use of solid-phase microextraction (SPME), after proper optimization, improved the signal by a factor of 100 leading to detection limits in the sub microg.L(-1). Different desorption conditions of iodophenol compounds from the SPME microfiber were studied to achieve the optimum preconcentration factor and best analytical performance. Different CE conditions were studied to achieve complete baseline separation of iodophenols in short migration times. Three different CE buffer systems were evaluated using ICP-MS detection. A buffer solution containing 20 mmol.L(-1) 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and an applied potential of +22 kV were finally selected leading to a maximum separation time of 6.6 min. A relative standard deviation (%RSD) of about 5.0% for ten consecutive determinations was obtained. Finally, the speciation methodology developed was utilized for the determination of iodophenol compounds in natural water samples.     

Determination of technetium-99 in aqueous samples by isotope dilution inductively coupled plasma-mass spectrometry

An isotope dilution/inductively coupled plasma mass spectrometric method (ID/ICP-MS) for measuring the concentration of technetium-99 in aqueous samples was developed at the Savannah River Technology Center (SRTC). The procedure is faster than radiometric tecniques, is less subject to interferences, and has equal or better detection limits. It is currently being used to measure the concentration of⁹⁹Tc in samples of Savannah River water collected in the vicinity of the Savannah River Site. In this method one liter samples of water are spiked with⁹⁷Tc. After equilibration, the technetium is extracted from the sample with a chromatographic resin. Interfering elements, molybdenum and ruthenium, are either not retained by the resin or are washed off with, dilute nitric acid. The technetium is then eluted with more concentrated nitric acid, and the⁹⁹Tc/⁹⁷Tc ratio in the eluant is measured with an ICP-MS. The⁹⁹Tc concentration in the original sample is calculated from the⁹⁹Tc/⁹⁷Tc ratio. The chemical recovery of the extraction procedure is greater than 90%. The detection limit of the instrument, taken as three times the background counts atm/z=99, is 0.6 part per trillion (ppt). The detection limit of the procedure, taken as three times the standard deviation of several reagent blank analyses, is 0.33 pCi/l.     

Dispersion effects of laminar flow and spray chamber volume in capillary electrophoresis-inductively coupled plasma-mass spectrometry: a numerical and experimental approach

Band broadening related to laminar flow and spray chamber dead volume is a potential problem in flow injection (FI)-inductively coupled plasma-mass spectrometry (ICP-MS). We studied these two dispersion effects with a sheath flow capillary electrophoresis (CE)-ICP-MS interface. A numerical model was used to simulate advection diffusion processes in the CE-capillary and dispersion in the spray chamber. Experimental results of FI with this CE-ICP-MS interface agree well with numerical modeling results. Dispersion due to laminar flow depends strongly on capillary diameter and analyte diffusion coefficient and to a lesser extent on laminar velocity and capillary length and typically amounts to one order of magnitude peak width increase. Three spray chambers of 5, 20 and 150 ml dead volume showed an increase in band broadening and peak tailing with increasing dead volume. The use of standard Scott-type spray chambers (>90 ml volume) increases peak widths by 5-10 s regardless of injection time. The use of a low dead volume spray chamber is recommended for experiments where resolution is critical. The modeling approach can be extended to the coupling of other flow injection techniques, like micro-LC and nano-LC with ICP-MS.     

Determination of fission products in nuclear samples by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS)

Determination of fission products and of their isotopic composition is of high importance for the characterisation and complete inventory of nuclear fuels. Radiometric and mass spectrometric methods, which are currently used, enable only an incomplete determination of the fission products. Radiometric methods cannot be applied to all fission products and mass spectrometric methods are hindered by the existence of isobaric interferences, therefore a previous chemical separation is required before mass spectrometric analysis. Capillary electrophoresis (CE) has been coupled with inductively coupled plasma mass spectrometry (both ICP-QMS and ICP-SFMS). Typical detection limits of 6 ng/mL and 4 pg/mL for caesium as well as 8 ng/mL and 7 pg/mL for lanthanides have been obtained by CE-ICP-QMS and CE-ICP-SFMS, respectively. In addition to these very low detection limits, the procedures present the advantages to be fast (6 min for caesium and 13 min for lanthanides, respectively), to require a low microliter range sample volume and a nanoliter range injection volume. The radiation dose for the personnel as well as the volume of nuclear liquid wastes generated during the measurements are consequently reduced.The procedures have been applied to nuclear samples from PUREX process and leachates from MOX fuels.     

Complexation of europium and uranium by humic acids analyzed by capillary electrophoresis-inductively coupled plasma mass spectrometry

Investigations of the mobility of radioactive and nonradioactive substances in the environment are important tasks for the development of a future disposal in deep geological formations. Dissolved organic matter (DOM) can play an important role in the mobilization of metal ions due to complexation. In this study, we investigate the complexation behavior of humic acid (HA) as a model substance for DOM and its influence on the migration of europium as homologue for the actinide americium and uranium as the principal component of nuclear fuel. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For the study, 0.5 mg·L?1 of the metals and 25 mg·L?1 of (purified Aldrich) HA and an aqueous solution sodium-perchlorate with an ionic strength of 10 mM at pH 5 were used. CE-ICP-MS clearly shows the different speciation of the triple positively charged europium and the double positively charged uranyl cation with HA.     

Platinum metallodrug-protein binding studies by capillary electrophoresis-inductively coupled plasma-mass spectrometry: characterization of interactions between Pt(II) complexes and human serum albumin

Characterizing how platinum metallocomplexes bind to human serum albumin (HSA) is essential in evaluating anticancer drug candidates. Using cisplatin as a reference complex, the application of capillary electrophoresis (CE) to reliably assess drug/HSA interactions was validated. Since this complex is small compared to the size of the protein, the binding response could only be recognized when applying CE coupled to a (platinum) metal-specific mode of detection, namely inductively coupled plasma-mass spectrometry (ICP-MS). This coupling allowed for confirmation of a specific affinity of cisplatin and novel Pt complexes to HSA, measurement of the kinetics of binding reactions, and determination of the number of drug molecules attached to the protein. As the cisplatin/HSA molar ratio increased, the reaction rate became faster with a maximum on the kinetic curve appearing at about 50 h of incubation at 20 times excess of cisplatin. The reaction was characterized as a pseudo-first order reaction with the rate constant k = 0.003 min(-1) at 37 degrees C. When incubated with a 20-fold excess of cisplatin, HSA bound up to 10 mol of Pt per mol of the protein. This is indicative for a strong metal-protein coordination occurring at several HSA sites other than the only protein cysteine residue. Structural analogs of cisplatin, bearing aminoalcohol ligands, showed comparable protein binding reactivity and stoichiometry but a common equilibrium was not reached even after one week of incubation. Also apparent was a two-step mechanism of the binding reaction. Results demonstrated the suitability of CE-ICP-MS as a rapid assay for high-throughput studying of drug/HSA interactions.     

The potential and challenges of elemental speciation by capillary electrophoresis-inductively coupled plasma mass spectrometry and electrospray or ion spray mass spectrometry

Capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICP-MS) and electrospray (ES) or ion spray (IS) mass spectrometry (MS) are recently introduced techniques for elemental speciation. Both techniques have the potential for rapid elemental speciation with low detection limits. Examples of the use of CE-ICP-MS for elemental speciation of positive, neutral and negative species are discussed. Issues in interfacing CE and ICP-MS are considered briefly. The potential advantages and disadvantages of laminar flow in CE-ICP-MS are examined. Potential difficulties in CE-ICP-MS including loss of sample, chemical matrix effects and changes in speciation during separation are discussed. The interpretation of ES or IS-MS spectra and analysis of complex mixtures are considered. Calibration and chemical matrix effects are assessed. Potential pitfalls of interpreting bare metal ion spectra as elemental analysis are discussed. The need for fundamental understanding of the processes that control ES and IS-MS signals is examined. High conductivity samples currently present difficulties for CE-ICP-MS or ES and IS-MS.     

Sectional power-law correction for the accurate determination of lutetium by isotope dilution multiple collector-inductively coupled plasma-mass spectrometry

In this study, we employ a sectional power-law (SPL) correction that provides accurate and precise measurements of ¹⁷⁶Lu/¹⁷⁵Lu ratios in geological samples using multiple collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS). Three independent power laws were adopted based on the ¹⁷⁶Lu/¹⁷⁶Yb ratios of samples measured after chemical chromatography. Using isotope dilution (ID) techniques and the SPL correction method, the measured lutetium contents of United States Geological Survey rock standards (BHVO-1, BHVO-2, BCR-2, AGV-1, and G-2) agree well with the recommended values. Results obtained by conventional ICP-MS and INAA are generally higher than those obtained by ID-TIMS and ID-MC-ICP-MS; this discrepancy probably reflects oxide interference and inaccurate corrections.     

Effect of glycerol on micelle formation by ionic and nonionic surfactants at 25 degrees C

The effect of glycerol on the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and of the ethoxylated nonionic surfactant Brij 58 has been investigated by various experimental techniques. For both surfactants the critical micellar concentration (cmc), determined by surface tension measurements, is almost unaffected by the presence of glycerol in the mixture; only at high glycerol concentrations (>/=20% w/w) does the cmc significantly increase. The area per surfactant molecule at the air-solution interface, A, increases with increasing glycerol weight percentage, w(g). Fluorescence quenching measurements indicate that the presence of glycerol induces a lowering of the aggregation number of both surfactants. The glycerol intradiffusion coefficient has been measured by the pulsed-gradient spin-echo NMR technique as a function of glycerol content at constant surfactant concentration. It is almost unaffected by the presence of the surfactants, indicating that no direct glycerol-surfactant interaction occurs in the mixture. The surfactant intradiffusion coefficient has been also measured. In the case of CTAB, it increases with increasing glycerol concentration, a reflection of the decreased aggregation number. For Brij 58, in spite of the lowering of the aggregation number, the surfactant intradiffusion coefficient decreases with increasing glycerol concentration, suggesting an increase of the intermicellar interaction. The experimental evidence shows that for both surfactants the micellization is affected by the presence of glycerol through an indirect, solvent-mediated mechanism. In the case of CTAB, the main effect of glycerol is a lowering of the medium dielectric constant, which enhances the electrostatic interactions in solution. In the case of Brij 58, the results can be interpreted in terms of a salting-out effect according to which glycerol competes with the surfactant for water molecules, causing a dehydration of the surfactant ethoxylic headgroup.     

Study of the binding equilibrium between Zn(II) and HSA by capillary electrophoresis-inductively coupled plasma optical emission spectrometry

A new method has been developed for following the interaction between zinc ion and human serum albumin (HSA) by capillary electrophoresis-inductively coupled plasma optical emission spectrometry. Under optimized experimental conditions, the detection limit (3σ) for free Zn²⁺ ion was found to be 1.34 μM by running 11 replicates of the reagent blank. The RSD was less than 3% and the recovery was more than 98.13%. The linear range of zinc ion concentration was between 5.1 μM and 0.3 M. The measured Zn(II)-HSA combination values of n₁ and K₁ for primary binding of Zn²⁺ to HSA were 1.09 and 2.29 × 10⁵ L mol⁻¹, respectively. The measured values of n₂ and K₂ for the non-specific binding of Zn²⁺ to HSA were 8.96 and 6.65 × 10³ L mol⁻¹, respectively. This new method allows rapid analysis of a small amount of sample, simple operation, while avoiding long periods of dialysis and eliminating interference from other metal ions. This method provides a reliable and convenient new way for studying interactions between metal ions and biomolecules.     

Determination of phosphorylation sites in lipooligosaccharides from Pseudoalteromonas haloplanktis TAC 125 grown at 15 degrees C and 25 degrees C by nano-electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Lipooligosaccharides (LOSs) are macromolecules present on the external cellular membrane of Gram-negative bacteria, structurally made of two distinct regions, lipid A and Core. By varying their growth temperature, bacteria such as psychrophiles change the phosphorylation distribution of the LOSs produced. The level of phosphorylation and the phosphate group positions in LOSs produced by the extremophile psychrophilic bacterium Pseudoalteromonas haloplanktis TAC 125, grown at 15 degrees C and 25 degrees C, were investigated by nano-electrospray ionization quadrupole time-of-flight mass spectrometry (nanoESI-QTOF-MS) and tandem mass spectrometry (MS/MS). The samples, obtained by phenol/chloroform/petroleum ether (PCP) extraction of dried cells, were treated with hydrazine at 37 degrees C in order to reduce the heterogeneity by removal of the ester-linked fatty acid moieties. The molecular ion distributions in these LOS fractions were investigated in negative ion mode. Based on these data it was postulated that the sample grown at 25 degrees C contained four phosphate groups while that at 15 degrees C contained three. In order to determine phosphorylation sites in sugar chains, the samples were submitted to low collision energy MS/MS for sequencing. In the sample with three phosphates, one was found to be linked to the tetrasaccharide Core region, more precisely to position C-4 of the Kdo unit. The two remaining phosphate groups were both linked to the 2-acylamide-2-deoxy-D-glucopyranose of the lipid A moiety, and two possible distributions could be postulated on the basis of the fragmentation pattern obtained; in the first case both phosphate groups are linked as a pyrophosphate moiety to position C-1 of the proximal glucosamine (reducing residue), while in the second case one phosphate is linked to position C-1 of the proximal glucosamine and the other to position C-4' of the distal glucosamine (non-reducing residue). This distribution was also found in the lipid A moiety of the tetraphosphorylated sample grown at 25 degrees C, which bears two phosphate groups on the Core region, one on position C-4 of the Kdo and the other on position C-7 or C-8 of the same residue. The phosphate locations were derived from the intra-ring cleavage ions of sugar moieties in the LOSs obtained by an optimized CID procedure using negative ion QTOF-MS/MS.     

浊点萃取-电感耦合等离子体质谱法测定植物样品中的痕量铂与钯

建立了浊点萃取电感耦合等离子体质谱法测定植物样品中痕量铂与钯的方法,方法检出限分别为0.17 ng/g和0.10 ng/g,样品加标回收率在85%～110%之间。利用建立的方法对采自北京环路旁的植物样品进行了测定,铂与钯含量范围分别为0.35～5.35 ng/g和1.95～10.85 ng/g,钯的含量普遍高于铂的含量。     

Determination of tin in environmental samples by graphite furnace atomic absorption and inductively coupled plasma-mass spectrometry

Summary Methods for the determination of total Sn in environmental samples (waters, animal tissue, plant material, sediments and coal fly ash), by graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS) have been developed and evaluated.Noble metals (Ag, Au, Pd, Pt, Rh) under reducing conditions were studied as matrix modifiers for the determination of Sn by GFAAS. The maximum ashing temperature (1400°C), highest sensitivity and the best absolute detection limit (4 pg) were achieved when Pd was used in the presence of hydroxylamine hydrochloride. The achievable sensitivity depended strongly on the chemical composition of the matrix.Both GFAAS and ICP-MS appeared to be equally sensitive techniques for the direct determination of Sn in waters, though ICP-MS was a more convenient and sensitive technique for the determination of Sn in digested biological and geological materials.

---

Bestimmung von Zinn in Umweltproben durch Graphitrohr-AAS und ICP-MS

     

电感耦合等离子体质谱(ICP-MS)法测定地质样品中Cu和Zn的干扰研究

电感耦合等离子体质谱(ICP-MS)法标准模式测定地质样品中Cu和Zn时,样品溶液中Ti在高温下易形成TiO⁺和TiOH⁺产生离子重叠干扰,使测定值偏离真值而影响测定结果。采用氢氟酸-高氯酸-硝酸消解、王水复溶样品,通过多级在线校正⁴⁶Ti¹⁶O⁺,消除TiO⁺和TiOH⁺离子重叠干扰,研究了单质Ti与⁴⁶Ti¹⁶O⁺、质荷比63、64、65、66离子间存在的关系,建立了一种电感耦合等离子体质谱(ICP-MS)法测定地质样品中Cu和Zn的分析方法。结果表明：单质Ti对Cu和Zn产生的干扰值与其质量浓度呈非简单的正相关性,TiO⁺产生的干扰离子质荷比65离子强度比63高,质荷比64离子强度比66高;⁴⁶Ti¹⁶O⁺对质荷比63、66离子干扰增量值与单质Ti质量浓度变化无关;^6...     

电感耦合等离子质谱法测定染铅猪仔的血铅、尿铅含量

利用电感耦合等离子质谱法测定染铅猪仔的血铅、尿铅含量.铅元素校正曲线的相关系数达到0.9999,方法检出限为0.08 μg/L.用冻干牛血铅、镉成分分析标准物质和冻干人尿铅成分分析标准物质验证了方法的准确性和重复性,分析结果表明,测定值与标准值基本吻合,测定值的相对标准偏差＜3.4％.用此方法分析了染铅猪仔不同时段的血...