Determination of thorium and uranium in ultrapure lead by inductively coupled plasma mass spectrometry

A method for the determination of U and Th at sub-ppt levels in high-purity Pb samples using extraction chromatography with ICPMS detection is described. Following acid digestion, uranium and thorium are separated from the lead matrix using UTEVA resin. Sorption and elution procedures were optimized, the potential reusability of the chromatographic resin was evaluated, and a performance comparison between prepacked and freshly prepared UTEVA column was made. Uranium could be eluted with 0.025 M HCl and Th then recovered using 0.5% oxalic acid. Recovery yields for U exceed 80% whereas those for Th were typically 60%. Procedural detection limits of 0.5 and 1.5 pg g(-)(1) were obtained for U and Th, respectively. For purposes of comparison, GD-MS analysis of samples was also performed, yielding results consistent with those generated by ICPMS but with inferior detection power.     

A preconcentration/matrix reduction method for the analysis of rare earth elements in seawater and groundwaters by isotope dilution ICPMS

A simple method of simultaneous preconcentration and matrix reduction was developed for the analysis of rare earth elements (REEs) in seawater and groundwater by ID ICPMS. The method utilizes partitioning of the REEs with solid hydroxides to separate them from soluble matrix species (e.g., Ba2+, NOM, seawater salts). Acidified samples were spiked and equilibrated with an enriched isotope cocktail (142Ce, 145Nd, 161Dy, 171Yb). Aqueous NH3 was then added to the spiked samples to induce the coprecipitation of the REEs with a small fraction of the natural Mg2+ as Mg(OH)2. The samples were centrifuged and the precipitate was rinsed to remove more than 99.8% of the Ba2+ along with the matrix salts. The precipitate was dissolved in 400 microL of 10% HNO3 for ICPMS analysis. The four spiked elements, determined by isotope dilution, served as internal standards for the remaining REEs. Analysis of NASS-4 and NASS-5 seawater reference materials showed good agreement with published values. Calculated limits of detection for a 1.65-g sample ranged from 0.1 pg/g for the light REEs to 0.02 pg/g for the heavy REEs. The reagent blanks ranged from a high of 0.28 pg/sample for Ce to a low of 0.0036 pg/sample for Tb.     

A group separation method for ruthenium, palladium, rhenium, osmium, iridium, and platinum using their bromo complexes and an anion exchange resin.

A new group separation method for Re and PGE (Ru, Pd, Os, Ir, Pt) is described using a novel anion exchange chromatographic resin called TEVA. Re and PGEs are converted into bromo complexes by heating with HF-HBr mixture in a Teflon bomb at 518 K, by in situ-generated Br2 formed by reaction of HBr and HNO3. Distribution coefficients (Kd) of the bromo complexes onto TEVA resin in 0.1 M HBr with heating at 353 K for one night were 2,200, 16,000, 1,600, 5,500, 4,000, and 17,000 for Ru, Pd, Re, Os, Ir, and Pt, respectively, thus allowing 97% recovery of Re and PGEs in 5 mL of solution by 0.1 mL of resin. These strongly bound Re and PGE bromo complexes are stripped and recovered >90% by the following three steps: (i) addition of 6 M HCl at 353 K and 2.2 M HCl-5 M HBr at 353 K; (ii) heating the resin in 6 M HCl at 353 K to convert the bromo complexes into the chloro complexes with weaker affinities to the resin; and (iii) sequential addition of the HCl-HBr mixture at room temperature and 7 M HI. Neither the elution profile nor the recovery yield for a 0.2-g geological sample showed significant changes, indicating minimal matrix effects for the geological samples. Total blanks were < 14 pg for Ru, Pd, and Pt and < 10 pg for Re, Os, and Ir. This new technique, therefore, is suitable for simultaneous determination of subnanogram per gram of Ru, Pd, Re, Os, Ir, and Pt and Os isotope analysis in geological, mineralogical, and environmental samples without direct addition of toxic reagents required in distillation/extraction of Os or oxidizing of Ir.     

An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry

A novel method for the single-step separation of Zr + Hf from all matrix elements of geological samples has been developed for Hf isotopic measurements using multiple collector-ICP-mass spectrometry. The method combines an effective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phosphonate, commercially available as U-TEVA.Spec. Using this simple and rapid procedure, Hf and Zr can be isolated in a single separation step with good recoveries (>90%) and satisfactory blank levels (approximately 55 pg of Hf), so that a subsequent isotopic measurement with ICPMS is possible. An excellent separation from rock-forming constituents is achieved, including those elements (Al, P, Ti, Cr, Fe, Mo, etc.) known to interfere in conventional separation methods based on ion-exchange techniques. The potential of this new method for Hf isotopic analysis is demonstrated by replicate MC-ICPMS measurements of 176Hf/177Hf ratios in seven international reference materials of silicate rocks, spanning a range of Hf contents and bulk compositions.     

Determination of mercury in coal by isotope dilution cold-vapor generation inductively coupled plasma mass spectrometry

A method based on isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICPMS) has been developed for high-accuracy determinations of mercury in bituminous and sub-bituminous coals. A closed-system digestion process employing a Carius tube is used to completely oxidize the coal matrix and chemically equilibrate the mercury in the sample with a 201Hg isotopic spike. The digestates are diluted with high-purity quartz-distilled water, and the mercury is released as a vapor by reduction with tin(II) chloride. Measurements of 201Hg/202Hg isotope ratios are made using a quadrupole ICPMS system in time-resolved analysis mode. The new method has some significant advantages over existing methods. The instrument detection limit is less than 1 pg/mL. The average blank (n = 17) is 30 pg, which is roughly 1 order of magnitude lower than the equivalent microwave digestion procedure. The detection limit in coal is blank limited and is approximately 40 pg/g. Memory effects are very low. The relative reproducibility of the analytical measurements is approximately 0.5% for mercury concentrations in the range 10-150 ng/g. The method has been used to measure mercury concentrations in six coal reference materials, SRM 1632b (77.4 ng/g), SRM 1632c (94.3 ng/g), BCR 40 (433.2 ng/g), BCR 180 (125.0 ng/g), BCR 181 (135.8 ng/g), and SARM 20 (252.6 ng/g), as well as a coal fly ash, SRM 1633b (143.1 ng/g). The method is equally applicable to other types of fossil fuels including both crude and refined oils.     

Diode laser thermal vaporization inductively coupled plasma mass spectrometry

An approach of sample introduction for inductively coupled mass spectrometry (ICPMS), diode laser thermal vaporization (DLTV) is described. The method allows quantitative determination of metals in submicroliter volumes of liquid samples. Laser power is sufficient to induce pyrolysis of a suitable substrate with the deposited sample leading to aerosol generation. Unlike existing sample introduction systems based on laser ablation, it uses a NIR diode laser rather than an expensive high-energy pulsed laser. For certain elements, this sample introduction technique may serve as an alternative to solution analysis with conventional nebulizers. Using a prearranged calibration set, DLTV ICPMS provides rapid and reproducible sample analysis (RSD ~ 10%). Sample preparation is fast and simple, and the prepared samples can easily be archived and transported. The limits of detection for Co, Ni, Zn, Mo, Cd, Sn, and Pb deposited on the preprinted paper were found to be in the range of 0.4-30 pg. The method was characterized, optimized, and applied to the determination of Co in a drug preparation, Pb in whole blood, and Sn in food samples without any sample pretreatment.     

Species-selective analysis by microcolumn multicapillary gas chromatography with inductively coupled plasma mass spectrometric detection.

A glass rod (5-20 cm long, 2 mm o.d.) containing more than 1200 parallel microchannels (< 40 microns i.d.) was converted into a high-resolution (> 100 theoretical plates cm-1) GC column by coating the inside of each channel in a way that compensated for the dispersion of the channel inner diameter. The columns were evaluated for the separation of mixtures of several organometallic (Hg, Sn, Pb) compounds prior to on-line sensitive metalselective detection by ICPMS. Chromatographic separation conditions were optimized to enable a rapid (within a maximum 30 s) multielemental speciation analysis. Absolute detection limits were 0.1 pg for Hg, 0.05 pg for Sn, and 0.03 pg for Pb using the carrier gas flows of approximately 200 mL min-1. The microcolumn multicapillary GC/ICPMS developed was applied to the analysis of a number of environmental samples. The results were validated with certified reference materials for tin (BCR477, PACS-2) and mercury (DORM-1, TORT-1).     

Stability of technetium and decontamination from ruthenium and molybdenum in determination of 99Tc in environmental solid samples by ICPMS

A rapid and efficient method for the determination of (99)Tc in environmental solid samples was developed using chromatographic separation combined with inductively coupled plasma mass spectrometry (ICPMS) measurement. The volatility of technetium during sample ashing and solution evaporation was investigated to establish a reliable sample pretreatment procedure. A novel approach was developed to improve the removal of molybdenum and ruthenium in chromatographic separation using 30% H(2)O(2) pretreatment of the loading solution and extraction chromatographic separation using two serial small TEVA columns. The decontamination factors of more than 4 × 10(4) and 1 × 10(5) are achieved for molybdenum and ruthenium, respectively. Chemical yields of technetium in entire procedure range from 60% to 95% depending on the type and amount of samples, and the detection limit of 0.15 mBq/g for (99)Tc was obtained. The method has been successfully applied for the determination of (99)Tc in environmental solid samples.     

Hydrodynamic chromatography online with single particle-inductively coupled plasma mass spectrometry for ultratrace detection of metal-containing nanoparticles

Nanoparticle (NP) determination has recently gained considerable interest since a growing number of engineered NPs are being used in commercial products. As a result, their potential to enter the environment and biological systems is increasing. In this study, we report on the development of a hyphenated analytical technique for the detection and characterization of metal-containing NPs, i.e., their metal mass fraction, size, and number concentration. Hydrodynamic chromatography (HDC), suitable for sizing NPs within the range of 5 to 300 nm, was coupled online to inductively coupled plasma mass spectrometry (ICPMS), providing for an extremely selective and sensitive analytical tool for the detection of NPs. However, a serious drawback when operating the ICPMS in its conventional mode is that it does not provide data regarding NP number concentrations and, thus, any information about the metal mass fraction of individual NPs. To address this limitation, we developed single particle (SP) ICPMS coupled online to HDC as an analytical approach suitable for simultaneously determining NP size, NP number concentration, and NP metal content. Gold (Au) NPs of various sizes were used as the model system. To achieve such characterization metrics, three calibrations were required and used to convert ICPMS signal spikes into NPs injected, NP retention time on the HDC column to NP size, and ions detected per signal spike or per NP to metal content in each NP. Two calibration experiments were required in order to make all three calibrations. Also, contour plots were constructed in order to provide for a convenient and most informative viewing of this data. An example of this novel analytical approach was demonstrated for the analysis of Au NPs that had been spiked into drinking water at the ng Au L(-1) level. The described technique gave limits of detection for 60 nm Au NPs of approximately 2.2 ng Au L(-1) or expressed in terms of NP number concentrations of 600 Au NPs mL(-1). These were obtained while the 60 nm NPs exhibited a retention time of 771 s at a mobile phase flow rate of 1 mL min(-1).     

Online in-tube solid-phase extraction using a nonfunctionalized PVC tube coupled with ICPMS for in vivo monitoring of trace metals in rat brain microdialysates

We have developed a simple, automatic, online in-tube solid-phase extraction (SPE) method for the preconcentration of trace elements from saline samples. The method takes advantage of the adsorption of trace metal ions onto the interior of a nonfunctionalized PVC tube as a means of separation from the matrix salt. The adsorption of transition metal ions is presumably dominated by Lewis acid/base interactions, which facilitate the formation of metal-PVC complexes. For simultaneous determination of multiple trace metals in the extracellular fluid from the brains of anesthetized rats, we developed an online analytical system comprising microdialysis sampling, the established in-tube extraction procedure, and ICPMS. In the extraction step, the efficiency was optimal when the pH of the sample was adjusted to 8.0 using phosphate buffer. After extraction onto the interior of PVC tube, the adsorbed analytes were eluted with 0.5% HNO 3 prior to online ICPMS measurement. For those elements present in the extracellular fluid at less than nanogram-per-milliliter concentrations (i.e., Cu, Zn, and Mn), a temporal resolution of 12 min was required to collect enough microdialysate to meet the sensitivity requirements of the ICPMS instrument. Noteworthily, because washing and postconditioning the interior of PVC tube are not necessary, a relatively unsophisticated and clean procedure was attained and extremely low detection limits in the range of 5.0 to 510 ng L (-1) were thus obtained for the analysis of Mn, Cu, Zn, Pb, Cd, Ni, and Co in microdialysate samples of 8 microL by ICPMS. To the best of our knowledge, this study is the first to exploit PVC peristaltic tubing as an SPE adsorbent in the laboratory-on-valve mode for online sample treatment and trace metal preconcentration prior to ICPMS measurement. We confirmed the analytical reliability of this method through the analysis of the certified reference material SLEW-3 (estuarine water) and 2670a (human urine) and demonstrated its applicability through simultaneous in vivo monitoring of the basal concentrations and concentration profiles of multiple metal ions in the brain extracellular fluid of a living rat.     

Evaluation of inductively coupled plasma mass spectrometry as an elemental detector for supercritical fluid chromatography

Supercritical fluid chromatography coupled with inductively coupled plasma mass spectrometry shows high potential for the determination at ultratrace levels of organometallic compounds of environmental interest. In this study the determination of organotin compounds at ultratrace levels is demonstrated. In this work a supercritical fluid chromatography/inductively coupled plasma mass spectrometry (SFC/ICPMS) interface was developed. Separation of tetraalkyltin compounds shows detection levels in the subpicogram range (0.034 pg for tetrabutyltin; 0.047 pg for tetraphenyltin). The linear ranges are over 3 orders magnitude (1-1000 pg). The reproducibility of sample injections are better than 5% RSD.     

Direct determination of rare earth elements at the subpicogram per gram level in antarctic ice by ICP-SFMS using a desolvation system

A method, based on inductively coupled plasma sector field mass spectrometry coupled with a microflow nebulizer and a desolvation system, has been developed for the direct determination of rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) down to the subpicogram per gram level (1 pg/g = 10(-12) g g(-1)) in approximately 1 mL of molten Antarctic ice. Contamination problems were carefully taken into account by adopting ultraclean procedures during the sample pretreatment phases. The use of a desolvation system for sample introduction during the analysis greatly reduced spectral interferences from oxide formation; the residual interfering contributions were calculated and subtracted whenever necessary. A matched calibration curve method was used for the quantification of the analytes. Instrumental detection limits ranged from 0.001 pg/g for Ho, Tm, and Lu to 0.03 pg/g for Gd. The precision, in terms of relative standard deviation on 10 replicates, ranged from 2% for La, Ce, Pr, and Lu, up to 10% for Er, Tm, and Yb. This methodology allowed the direct determination of REE in a 1-mL sample of ancient Antarctic ice with concentration ranges between 0.006 and 0.4 pg/g for Tm and 0.9-60 pg/g for Ce.     

Development of an on-line flow injection Sr/matrix separation method for accurate, high-throughput determination of Sr isotope ratios by multiple collector-inductively coupled plasma-mass spectrometry

This work introduces a newly developed on-line flow injection (FI) Sr/Rb separation method as an alternative to the common, manual Sr/matrix batch separation procedure, since total analysis time is often limited by sample preparation despite the fast rate of data acquisition possible by inductively coupled plasma-mass spectrometers (ICPMS). Separation columns containing approximately 100 muL of Sr-specific resin were used for on-line FI Sr/matrix separation with subsequent determination of (87)Sr/(86)Sr isotope ratios by multiple collector ICPMS. The occurrence of memory effects exhibited by the Sr-specific resin, a major restriction to the repetitive use of this costly material, could successfully be overcome. The method was fully validated by means of certified reference materials. A set of two biological and six geological Sr- and Rb-bearing samples was successfully characterized for its (87)Sr/(86)Sr isotope ratios with precisions of 0.01-0.04% 2 RSD (n = 5-10). Based on our measurements we suggest (87)Sr/(86)Sr isotope ratios of 0.713 15 +/- 0.000 16 (2 SD) and 0.709 31 +/- 0.000 06 (2 SD) for the NIST SRM 1400 bone ash and the NIST SRM 1486 bone meal, respectively. Measured (87)Sr/(86)Sr isotope ratios for five basalt samples are in excellent agreement with published data with deviations from the published value ranging from 0 to 0.03%. A mica sample with a Rb/Sr ratio of approximately 1 was successfully characterized for its (87)Sr/(86)Sr isotope signature to be 0.718 24 +/- 0.000 29 (2 SD) by the proposed method. Synthetic samples with Rb/Sr ratios of up to 10/1 could successfully be measured without significant interferences on mass 87, which would otherwise bias the accuracy and uncertainty of the obtained data.     

Direct determination of lead isotopes (206Pb, 207Pb, 208Pb) in arctic ice samples at picogram per gram levels using inductively coupled plasma-sector field MS coupled with a high-efficiency sample introduction system

Adopting strict cleanroom procedures, ice samples from the Canadian High Arctic have been analyzed for Pb concentrations and Pb isotopes (206Pb, 207Pb, 208Pb) using ICP-SMS. The detection limit for Pb (0.06 pg g(-1)) was approximately 2 orders of magnitude lower than the lowest concentration of Pb in the ice samples (range, 4.3-1660 pg g(-1); median, 45 pg g(-1)). Acidification of ice samples with high-purity HNO3 for stabilization purposes contributed only 0.004 pg of Pb g(-1), which is an insignificant source of Pb. Using a new sample introduction system consisting of a heated (140 degrees C) minicyclonic spray chamber and a Peltier cooled condenser (2 degrees C) and by replacing the conventional sample cone with a high-performance cone, signal intensities for Pb were increased by approximately 1 order of magnitude. Thus, it was possible not only to measure Pb isotope ratios directly using ICP-SMS but also to achieve reasonable precision (approximately 0.2%) at low picogram per gram concentrations of total Pb. This precision is comparable to that achievable by thermal ionization mass spectrometry at such low Pb concentrations, but the ICP-SMS requires much less sample volume (approximately 2 mL), needs no sample pretreatment, and therefore is considerably faster and less expensive than the conventional approach. Even though absolute Pb concentrations in two ice samples dating from 1974 and 1852 were very similar (9 and 6 pg g(-1)) their fundamentally different isotopic signature (206Pb/207Pb: 1.169 +/- 0.002 vs 1.147 +/- 0.003) clearly indicates different sources of Pb. The analytical procedures described here, therefore, offer great promise for fingerprinting the predominant sources of atmospheric Pb in polar snow and ice.     

Two trace analytical methods for determination of hydroxylated PCBs and other halogenated phenolic compounds in eggs from Norwegian birds of prey

Two new trace analytical methods are presented for identification and quantification of phenolic compounds in complex biological matrixes such as bird of prey eggs. One method is based on derivatization with methyl chloroformate prior to GC/high-resolution MS (HRMS) analysis in electron impact ionization mode. Alternatively, the underivatized phenolic analytes were separated and detected by HPLC coupled to time-of-flight MS (TOF-MS) in the negative ion electrospray ionization mode. For both methods, the egg samples were homogenized and dried with acidified sodium sulfate, cold column-extracted, and cleaned up by gel permeation chromatography and subsequently a Florisil column. Recovery rates for pentachlorophenol (PCP), tetrabromobisphenol A (TBBPA), and selected hydroxylated PCBs (HO-PCBs) from spiked hen's eggs (spiking level 1 ng/g of wet weight (ww)) were in the range of 56-98% for the HPLC/MS method and 57-108% for GC/MS including derivatization. Typical detection limits of the HPLC/TOF-MS method were 5 pg/g ww (1-2 pg injected) for HO-PCBs and PCP and 20 pg/g ww (3 pg injected) for TBBPA. The GC/HRMS method achieved detection limits of approximately 1 pg/g ww in predatory bird eggs for all analytes (0.2 pg injected for derivatized TBBPA and 0.05 pg injected for derivatized HO-PCBs and PCP). Eight eggs from four different Norwegian predatory bird species were analyzed. The concentrations determined with the two different quantification methods corresponded well with each other. PCP and TBBPA were found in all samples at concentrations up to 1350 and 13 pg/g ww, respectively (GC/HRMS values). A total of 55 penta- to nonachloro-HO-PCB congeners were detected in the eight eggs, 10 of those could be structurally identified. The maximum HO-PCB congener concentration was found for 4-HO-CB 187 in a peregrine falcon egg with estimated 388 pg/g ww. Another peregrine falcon egg was highest contaminated with sum HO-PCBs (estimated 2.1 ng/g ww). This level was 1.2 per thousand of the sum PCBs value for the same egg. Furthermore, indications were found that the HO-PCB congener distribution pattern could be species specific for predatory birds.     

Separation of thorium and uranium from silicate rock samples using two commercial extraction chromatographic resins

A new chemical separation technique to isolate Th and U from silicate rocks was established by using two kinds of commercial extraction chromatographic resins. In the first column procedure, with U/TEVA·spec resin, almost all elements except Th and U were eluted by 4 M HNO(3). Th was then separated by using 5 M HCl, and U was finally isolated by successive addition of 0.1 M HNO(3). A significant amount of Zr still remained in the Th fraction, which was then further purified in the second column stage using TEVA·spec resin. In the second procedure, Zr was eluted first by using 2 M HNO(3), and then Th was collected by 0.1 M HNO(3). Both the Th and U fractions obtained by these procedures were sufficiently pure for thermal ionization mass spectrometric (TIMS) analysis. Recovery yields of Th and U exceeded 90%, and total blanks were <19 pg for Th and <10 pg for U. Our method has advantages over previous methods in terms of matrix effects, tailing problems, and degree of isolation. Since Th and U are effectively separated without suffering any matrix interference from coexisting cations and anions, this technique can be used not only for the analysis of igneous rock samples but also for the analysis of soils, marine sediments, carbonates, phosphates and seawater, groundwater, and surface water.     

Anion-exchange chromatographic separation of Hg for isotope ratio measurements by multicollector ICPMS

A procedure is described for precise Hg isotope ratio measurements by solution nebulization multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Hg was released from geological samples using aqua regia extraction and then separated from other matrix elements with the aid of anion-exchange chromatography using strongly basic Dowex 1-X8 anion-exchange resin. Performance of the chromatographic procedure was evaluated using various types of replacement anions for elution of mercury, including l-cysteine, thiourea, NO3-, and SO42-. A solution of 0.15% l-cysteine in 0.06 M HCl was found to be the most convenient eluent for subsequent MC-ICPMS measurements. The optimized procedure provides separation of Hg from virtually all concomitant matrix elements while maintaining quantitative (>95%) recovery. In addition, band displacement chromatographic experiments were conducted to assess whether the anion-exchange purification can produce Hg isotope fractionation artifacts. No isotope fractionation between the Hg(II)-l-cysteine complex in aqueous solution and Hg ions in the anion-exchange resin was observed. Hg isotope ratio measurements were performed using the bracketing standards approach and on-line correction for instrumental mass discrimination using Tl spiking and normalization to the 205Tl/203Tl ratio. The absence of spectral interference during Hg isotope ratio measurements was verified using a three-isotope plot. Uncertainties of Hg isotope ratio measurements for replication of the entire procedure, expressed as two standard deviations, are better than +/-0.08 per thousand/amu. The described procedure facilitates study of variations in the isotopic composition of Hg in nature.     

Application of isotopically labeled methylmercury for isotope dilution analysis of biological samples using gas chromatography/ICPMS

An isotope dilution (ID) procedure for the determination of methylmercury (MMHg) in biological samples using an inductively coupled plasma mass spectrometer as detector after the capillary gas chromatographic separation (CGC/ICPMS) has been developed. For the first time, open-focused-microwave pretreatment has been used in conjunction with ID. Optimum conditions for the measurement of isotope ratios on the fast transient chromatographic peaks have been established. Mass bias was found to be about 1.5%/mass unit and was corrected by using the simultaneously measured thallium signals at 203Tl and 205Tl. After mass-bias correction, deviation of the theoretical mercury ratio values was found to be as low as 0.2%. Isotope ratio precisions based on the peak areas measurements were 0.3% RSD for 20 pg injected (as Hg absolute). The absolute detection limits were in the range of 20-30 fg for 202Hg and 201Hg. Methylmercury enriched in 201Hg has been synthesized by direct reaction with methylcobalamine. The concentration of the MMHg spike has been measured by reverse isotope dilution with a natural MMHg standard. The capabilities of CGC/ICPMS to measure isotope ratios were used to optimize sample derivatization by aqueous ethylation with NaBEt4 with respect to MMHg degradation pathways and quantitative recovery. The accuracy of the method developed has been validated with biological certified reference materials (CRM-463, DORM-1).     

Simultaneous ultratrace determination of Zr and Nb in chromium matrixes with ICP-dynamic reaction cell MS

A dynamic reaction cell (DRC) has been used to minimize the formation of metal-argide ions in inductively coupled plasma mass spectrometry and applied to the determination of Zr and Nb in Cr-rich samples. The formation of ArCr+ species from the plasma gas and the sample matrix was reduced by ion molecule reactions inside a DRC of the ICPMS used. Hydrogen was used as reaction gas, and the efficiency in the reduction of ArCr+ was similar to that of other plasma-based polyatomic ions as reported in an earlier study. The formation of CrOx+ ions is enhanced when the DRC is operated in pressurized mode. Adjustment of the transmission properties of the band-pass quadrupole to reject precursor ions can be achieved without dramatic decrease of sensitivity but with a significant improvement in the signal/background ratio. Measurements in solutions containing concentrations of up to 2 g/L Cr showed that the determination of Nb and Zr is possible in the nanogram per liter range in such a matrix. The limits of detection for Nb and Zr in pure Cr metal have been estimated at 2 ng/g for Nb and 5 ng/g for Zr. Analysis of basaltic reference samples resulted in very good agreement with previously published data.     

Selective determination of histamine by flow injection analysis

A flow injection analysis (FIA) method for the determination of histamine is described. Control of reaction timing allows exploitation of a transient, chemical-kinetic increase in selectivity that occurs when o-phthalaldehyde reacts with histamine. The molar fluorescence ratio (selectivity) of histamine/histidine reaches a maximum value of 800 in 32 s, precluding the need for separation of histamine from histidine, spermidine, and other potential interferences in biological samples. On-line dilution prevents matrix effects and affords a linear response up to approximately 4.45 mM histamine, or 500 mg of histamine free base/100 g. Under these conditions the detection limit (3 times peak-to-peak baseline noise) is 5.5 pg (corresponding to 0.60 mg of histamine free base/100 g of sample) and throughput is 60 injections per hour. The high sensitivity and high selectivity of the method allow the rapid determination of histamine in fish with minimal sample conditioning and will find application in the determination of endogenous histamine as well, such as in blood plasma and brain tissue.