Determining Ppb Mercury Concentrations Using a Spark-Source Mass Spectrometer Sample Changer

Abstract

A probe-type sample changer has been added to a spark-source mass spectrometer enabling the rapid determination of ppb levels of mercury by isotope dilution. The technique has also been used for determining Cd, Hg, and Zr in samples of air, water, and urine.     

Microanalyzer for biomonitoring lead (Pb) in blood and urine

Biomonitoring of lead (Pb) in blood and urine enables quantitative evaluation of human occupational and environmental exposures to Pb. State-of-the-art ICP–MS instruments can only analyze metals in laboratories, resulting in lengthy turnaround times, and they are expensive. In response to the growing need for a metal analyzer capable of on-site, real-time monitoring of trace toxic metals in individuals, we developed a portable microanalyzer based on flow-injection/stripping voltammetry (ASV), and validated the system using rat blood and urine spiked with known amounts of Pb. Fouling of electrodes by proteins often prevents the effective use of electrochemical sensors in biological matrices. Minimization of such fouling was accomplished with suitable sample pretreatment and by establishing turbulent flow of blood and urine containing Pb onto the electrode inside the microanalyzer, which resulted in no apparent electrode fouling even when the samples contained 50% urine or 10% blood by volume. No matrix effect was observed for the voltammetric Pb signals, even when the samples contained 10% blood or 10% urine. The microanalyzer offered linear concentration ranges relevant to Pb exposure levels in humans (0–20 ppb in 10% blood samples, 0–50 ppb in 50% urine samples). The device showed excellent sensitivity and reproducibility; Pb detection limits were 0.44 ppb and 0.46 ppb, and % R.S.D. was 4.9 and 2.4 in 50% urine and 10% blood samples, respectively. It gave similar Pb concentrations in blood and urine to those measured by ICP–MS. It offered high throughput (3 min per sample) and economical use of samples (60 μL per measurement) as well as low reagent consumption (1 μg of Hg per measurement), thus minimizing environmental concerns associated with mercury use. Since it is miniaturized, the microanalyzer is portable and field-deployable. Thus, it shows much promise as the next-generation analyzer for the biomonitoring of toxic metals.     

关于冷原子吸收法测定尿汞影响因素探讨

介绍了对尿汞快速测定法的改进，用消泡剂磷三丁酸消除尿中泡沫，并讨论了尿汞测定的最佳条件，本法的相对标准偏差为４．８－９．０％，回收率９４－１０１％。     

Detection of trace levels of trichothecene mycotoxins in human urine by gas chromatography-mass spectrometry

A method is described for the simultaneous detection of the trichothecene mycotoxins T-2, HT-2, T-2 tetraol, diacetoxyscirpenol, 15-monoacetoxyscirpendiol, scirpentriol, nivalenol and deoxynivalenol, in human urine. Samples were extracted from Clin Elut columns and cleaned up using reversed-phase Sep-Pak C18 cartridges. Trichothecenes were derivatised as their heptafluorobutyryl esters, and detected by gas chromatography-mass spectrometry-selected-ion monitoring using electron impact ionisation. The method was validated by the analysis of 22 urine samples, spiked and submitted "blind" for analysis by another laboratory. An alternative gas chromatography-mass spectrometry method using negative ion chemical ionisation is also described and a preliminary comparison of the two methods made. The methods enabled levels down to 1 ppb to be detected, with confirmation of identity at levels between 2 and 5 ppb, depending on the toxin.     

Determination of Mercury in Geological Materials by Continuous-Flow,Cold-Vapor,Atomic Absorption Spectrophotometry

Abstract

To determine mercury in geological materials, samples are digested with nitric acid and sodium dichromate in a closed teflon vessel. After bringing to a constant weight, the digest is mixed with air and a sodium chloride-hydroxylamine hydrochloride-sulfuric acid solution and then Hg(II) is reduced to Hg with stannous chloride in a continuous flow manifold. The mercury vapor is then separated and measured using cold vapor atomic absorption spectrophotometry (CV-AAS). For a 100 mg sample the limit of detection is 20 parts per billion (ppb) Hg in sample. To obtain a 1% absorption signal, the described method requires 0.21 ppb Hg solution (equal to 16 ppb in sample). Precision is acceptable at less than 1.2% RSD for a 10 ppb Hg aqueous standard. Accuracy is demonstrated by the results of the analysis of standard reference materials. Several elements do interfere but the effect is minimal because either the digestion procedure does not dissolve them (e.g., Au or Pt) or the; are normally of low abundance (e.g., Se or Te).     

Determination of Gentian Violet in human urine and poultry feed by high performance liquid chromatography with electrochemical detection using a carbon fibre microelectrode flow cell

A sensitive and relatively selective high performance liquid chromatographic method for the determination of Gentian Violet (GV) in human urine and chicken feed is described. The method is based on solid-phase extraction, with subsequent reversed-phase chromatographic separation on a cyano column and amperometric detection using a carbon fibre microelectrode flow cell operated at + 1.3 V. The peak currents were directly proportional to GV concentration over the concentration range 1-30 ppb (for urine samples analysis) and 1-20 ppm for poultry feed analysis. Using this method, the minimum detectable concentration was estimated to be 0.5 ppb. The method was applied successfully to the determination of GV in human urine and in chicken feed, and it was concluded that the method could be applied to the quantitative analysis of GV in the presence of its major metabolite, leuco GV. In the proposed procedure, the occurrence of matrix effects during urine analysis was significant. The electrochemical pretreatment regime described in this paper was used to overcome these effects. Recovery studies were performed on both the human urine and chicken feed samples. The recovery of GV ranged from 92 to 96% in both matrices, with a relative standard deviation of less than 5.5%.     

Residue screening for the beta-agonists clenbuterol, salbutamol and cimaterol in urine using enzyme immunoassay and high-performance liquid chromatography.

The antibody for enzyme immunoassay was raised against clenbuterol-diazo-BSA, and salbutamol-carboxymethyl ether-biocytin was used as a label. Procedural blanks from 500 negative urine samples were always less than 0.2 ppb salbutamol or less than 0.02 ppb clenbuterol equivalents, and a residue level of 1 ppb was detected with good reliability. After treatment of veal calves with anabolic dosages, residue levels in urine amounted to 10-200 ppb clenbuterol or salbutamol. beta-Agonists were separated by high-performance liquid chromatography on LiChrospher RP-Select B columns, and acidic methanol-buffer or acetonitrile-buffer mobile phases. Combinations of high-performance liquid chromatography and enzyme immunoassay were used for confirmation.     

Transient isotachophoresis of highly saline trace metals under strong electroosmotic flow conditions

Transient isotachophoresis (TITP) is usually performed under low-electroosmotic flow (EOF) conditions using a coated capillary or a low pH background electrolyte. We used a bare fused-silica capillary for TITP stacking of anionic complexes of some heavy metals under high-EOF conditions (pH 9.0). The sample component chloride as a leading electrolyte induced stacking by an isotachophoretic mechanism and the complexing agent 4-(2-pyridylazo) resorcinol (PAR) acted as a terminating electrolyte. The optimized background electrolyte was composed of 150 mM N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 127 mM triethylamine, and 0.1 mM PAR at pH 9.0. The strong EOF at pH 9.0 pulled the analytes against their mobilities toward the outlet side, allowing a separation in the normal polarity mode. The stacking efficiency, reproducibility, analysis time, and sample loading capacity in coated and bare capillaries were compared. The stacking efficiency and reproducibility were higher and the analysis time was shorter in the coated capillary. However, a larger volume of a sample could be injected in the bare capillary to achieve detection limits comparable to those for the coated one without compromising the resolution between the analyte peaks. The limits of detection (S/N = 3) were in the sub-ppb range for the selected metals (Fe2+, 0.3 ppb; Ni2+, 0.16 ppb; and Zn2+, 0.8 ppb) in a standard saline sample with 250 mM NaCl matrix. The proposed method was successfully applied to the analysis of reference urine samples and human urine samples.     

Capillary electrophoresis of trace metals in highly saline physiological sample matrices

Trace metal ions in highly saline samples such as urine were determined with capillary electrophoresis (CE) without desalting or off-line preconcentration. By mixing with a dye, 4-(2-pyridylazo) resorcinol (PAR), the metal ions were converted into anionic complexes having strong absorbance near 500 nm. A large volume of the metal-PAR complex sample solution injected into a coated capillary was stacked isotachophoretically and separated under a reverse potential. The salt anion (chloride) and PAR in the sample matrix acted as the leading and terminating electrolytes, respectively. In a sample containing a 250 mM NaCl matrix, more than 400-fold enhancement in the absorbance detector response was realized compared to the normal CE injection mode. Combination of the dye complexation and isotachophoretic stacking provided excellent detection limits (S/N = 3) for three trace metal ions in the low ppb range (Fe(2+), 0.7 ppb, Ni(2+), 0.4 ppb; Zn(2+), 1.2 ppb) with absorbance detection. The migration time reproducibility was excellent (relative standard deviations: standard samples < 1%, urine samples approximately 1%). The proposed method is convenient and fast, and the sample analysis can be completed within 20 min.     

Development of a multi-component chemically reactive detection conjugate for the determination of Hg(II) in water samples

Mercury ions (Hg(II)) are considered highly toxic and hazardous element even at low levels. The contamination of Hg(II) is a global problem. To develop selective and sensitive technique for the detection of Hg(II) has attracted considerable attention. In this study, a multi-component chemically reactive detection conjugate for determination of Hg(II) has been synthesized and a competitive format assay was proposed. In the technique, the chemically reactive capture conjugate was coated on the plate. The reactive detection conjugate was then captured by the capture conjugate. TMB solution was added and catalyzed by HRP molecules immobilized on AuNPs. Finally, the developed enzymatic signal was measured at 450 nm. The linear range of the assay was 0.35–350 ppb with a detection limit of 0.1 ppb. The average recoveries of Hg(II) from mineral water, tap water and lake water were 100.03%, 103.13% and 102.03%, respectively. All coefficients of variation (CVs) were less than 10%. The results are closely correlated with those from inductively coupled plasma mass spectrometry (ICP-MS), which indicated that the developed technique is a reliable method for and sensitive detection of Hg(II) in water samples.     

Voltammetric detection of lead(II) and mercury(II) using a carbon paste electrode modified with thiol self-assembled monolayer on mesoporous silica (SAMMS)

The anodic stripping voltammetry at a carbon paste electrode modified with thiol terminated self-assembled monolayer on mesoporous silica (SH-SAMMS) provides a new sensor for simultaneous detection of lead (Pb2+) and mercury (Hg2+) in aqueous solutions. The overall analysis involved a two-step procedure: an accumulation step at open circuit, followed by medium exchange to a pure electrolyte solution for the stripping analysis. Factors affecting the performance of the SH-SAMMS modified electrodes were investigated, including electrode activation and regeneration, electrode composition, preconcentration time, electrolysis time, and composition of electrolysis and stripping media. The most sensitive and reliable electrode contained 20% SH-SAMMS and 80% carbon paste. The optimal operating conditions were a sequence with a 2 min preconcentration period, then a 60 s electrolysis period of the preconcentrated species in 0.2 M nitric acid, followed by square wave anodic stripping voltammetry from -1.0 V to 0.6 V in 0.2 M nitric acid. The areas of the peak responses were linear with respect to metal ion concentrations in the ranges of 10-1500 ppb Pb2+ and 20-1600 ppb Hg2+. The detection limits for Pb2+ and Hg2+ were 0.5 ppb Pb2+ and 3 ppb Hg2+ after a 20 min preconcentration period.     

Determination of zeranol and beta-zearalanol in calf urine by immunoaffinity extraction and gas chromatography-mass spectrometry after repeated administration of zeranol

A method for the determination of zeranol and its metabolite beta-zearalanol in bovine urine is described. It has been applied to samples from calves given multiple subcutaneous doses of zeranol. Samples were extracted with immunoaffinity columns containing antibodies raised against zeranol and were analysed by gas chromatography-mass spectrometry. The immunoaffinity columns were prepared by coupling immunoglobulin G fractions obtained from rabbit antisera with a Sepharose matrix. The immunizing agent was carboxybutylzeranol coupled to bovine serum albumin. Gas chromatography-mass spectrometry was performed in the negative-ion chemical ionization mode, after derivatization of the compounds to their pentafluorobenzyl ethers, and allowed detection of analytes with a sensitivity of 0.01 ppb in spiked urine. The derivatization method and the gas chromatographic determination were also applied to the similar compounds zearalanone, zearalenone and beta-zearalenol. A synthesis of dideuterated zeranol and beta-zearalanol by isotopic exchange is described. These deuterated analogues had an isotopic purity of more than 99% and were used for quantitation of zeranol and beta-zearalanol by isotope dilution mass spectrometry. The recoveries of zeranol and beta-zearalanol, using the immunoaffinity columns, were determined after extraction from spiked urine and were 84 and 64%, respectively. The urines of treated calves were collected for several days after treatments and were analysed after hydrolysis with beta-glucuronidase and arylsulphatase. The samples showed variable but generally decreasing concentrations of zeranol and beta-zearalanol. The levels of beta-zearalanol ranged from less than 0.01 to 98 ppb and were 1.2-3.2 times higher than those of zeranol.     

Detection of trace levels of thiodiglycol in blood, plasma and urine using gas chromatography-electron-capture negative-ion chemical ionisation mass spectrometry

A sensitive method has been developed for the detection and quantitative determination of thiodiglycol in blood, plasma and urine. Samples were extracted from Clin Elut columns and cleaned up on C18 Sep-Pak cartridges (blood, plasma) or Florisil Sep-Pak cartridges (urine). Tetradeuterothiodiglycol was added to the sample prior to extraction as internal standard. Thiodiglycol was converted to its bis-(pentafluorobenzoate) derivative and analysed by capillary gas chromatography-electron-capture negative-ion chemical ionisation mass spectrometry using selected ion monitoring. Levels of thiodiglycol down to 1 ng/ml (1 ppb) could be detected in 1-ml spiked blood and urine samples; calibration curves were linear over the range 5- or 10-100 ng/ml. Blood and urine samples from a number of control subjects were analysed for background levels of thiodiglycol. Concentrations up to 16 ng/ml were found in blood, but urine levels were below 1 ng/ml.     

Highly sensitive multiresponsive chemosensor for selective detection of Hg2+ in natural water and different monitoring environments

A new chemosensor RF1 that combines a ferrocene unit and a rhodamine block via the linkage of a carbohydrazone binding unit was designed and prepared for the highly selective detection of Hg (2+) in natural water. This chemosensor displays great brightness and fluorescence enhancement following Hg (2+) coordination within the limit of detection for Hg (2+) at 1 parts per billion (ppb). The fluorescence intensities are nearly proportional to the amount of Hg (2+) at the ppb level. It is capable of distinguishing between the safe and the toxic levels of inorganic mercury in drinking water. Hg (2+)-binding also arouses the absorption of the rhodamine moiety in RF1 significantly with the chromogenic detection limit for Hg (2+) at 50 ppb. The conventional UV-vis spectroscopic method thus has the potential to provide the critical information about the mercury hazard assessment for industrial wastewater discharging. The obvious and characteristic color change of the titration solution from colorless to pink upon the addition of Hg (2+) demonstrates that RF1 can be used for "naked-eye" detection of Hg (2+) in water. The Hg (2+) complexation also causes a significant shift of the redox potential about the ferrocene/ferrocenium couple. The electrochemical responses provide the possibility to quantitative analysis of Hg (2+) at the parts per million (ppm) level. Preliminary investigations in natural water samples including seawater and freshwater indicate that RF1 offers a direct and immediate Hg (2+) detection in complex media, pointing out its potential utility in environment monitoring and assessment. The responses of RF1 are Hg (2+) specific, and the chemosensor exhibits high selectivity toward Hg (2+) over other Group 12 metals, alkali, alkaline earth metals, and most of the divalent first-row transition metals. The RF1-Hg (2+) complex is successfully isolated and the Hg (2+)-binding is reversible. The crystal structure and spectral properties of its congener RF2 that contains one ferrocene group and two rhodamine 6G moieties were also investigated for a comparison.     

Determination of two oxy-pyrimidine metabolites of diazinon in urine by gas chromatography/mass selective detection and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry

An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.     

Sol-gel titania-coated needles for solid phase dynamic extraction-GC/MS analysis of desomorphine and desocodeine

Novel sol-gel titania film coated needles for solid-phase dynamic extraction (SPDE)-GC/MS analysis of desomorphine and desocodeine are described. The high thermal stability of titania film permits efficient extraction and analysis of poorly volatile opiate drugs. The influences of sol-gel reaction time, coating layer, extraction and desorption time and temperature on the SPDE needle performance were investigated. The deuterium labeled internal standard was introduced either during the extraction of analyte or directly injected to GC after the extraction process. The latter method was shown to be more sensitive for the analysis of water and urine samples containing opiate drugs. The proposed conditions provided a wide linear range (from 5-5000 ppb), and satisfactory linearity, with R(2) values from 0.9958 to 0.9999, and prominent sensitivity, LOQs (1.0-5.0 ng/g). The sol-gel titania film coated needle with SPDE-GC/MS will be a promising technique for desomorphine and desocodeine analysis in urine.     

Spectrofluorimetric determination of trace amounts of Ga(III) in aluminium and biological samples with 1-(2-pyridylazo)-2-naphthol in sodium dodecyl sulphate micellar medium

Summary A spectrofluorimetric method is proposed for the determination of gallium with 1-(2-pyridylazo)-2-naphthol as derivative reagent in sodium dodecyl sulphate micellar medium. Sensitivity is increased by a factor of 20 with respect to that obtained in 20% ethanol medium. The stoichiometry of the complex is 11. Optimum working conditions are about pH 4, 0.3% sodium dodecyl sulphate and absence of ethanol. The calibration graph is linear in the range 5–400 ppb of Ga(III) with a variation coefficient of 1.5% at 210 ppb of Ga for 10 replicates, and detection limit is 0.8 ppb. Main interferences are from copper and cobalt. Results obtained in the determination of Ga(III) in urine and aluminium samples show the validity of the method proposed.

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Spektrofluorimetrische Bestimmung von Spuren Ga(III) in Aluminium und biologischen Proben mit 1-(2-Pyridylazo)-2-naphthol in micellarem Natriumdodecyl-sulfatmedium

     

Determination of mercury in urine of Mexican dentists

Mercury levels in the urine of Mexican dentists were determined by instrumental neutron activation analysis. A control group with no suspicion of contamination by mercury was also studied. Acid digestion was used for samples treatment and the presence of ²⁰³Hg was determined by gamma spectroscopy. The ranges of mercury concentration found in urine were: for the dentists group from 0.19 to 11.56 mg Hg/l, with a mean value of 3.16 mg Hg/l and standard deviation of 2.74 mg Hg/l, and for the control group from 0.03 to 0.05 mg Hg/l with a mean value of 0.04 mg Hg/l and standard deviation of 0.01 mg Hg/l. The mercury levels found in urine of dentists are associated with several exposure factors which appear to be positively correlated to its concentration, such as years of dental practice, amalgamation techniques, etc.     

Activation analysis of selenium in cancer research

The method described in a previous work to separate trace amounts of selenium in organic samples without using a carrier, based on the adsorption on active carbon filters of the complex formed with ammonium pyrrolidindithiocarbamate (APDC) at pH 1.5–2, has been applied to urine samples from 15 females patients suffering from cervical uterine cancer. With this type of sample the method reaches a maximum sensitivity (few ppb) with a good statistical variation (±12%). Since the highest concentration of selenium in human tissues is found in the kidney, and the elimination of this element is mainly by the urine, the method seems to be a powerful tool in the research about the human metabolism of selenium. This paper shows a possible relation of selenium concentration in human urine and the evolution time of cervical uterine cancer, in spite of limits imposed by the statistical error plus the inhomogeneity of the sample.     

Determination of Mercury with a Miniature Sensor for Point-of-care Testing

In developing countries, subsistence gold mining entails mixing metallic mercury with crushed sediments to extract gold. In this approach, the gold−mercury amalgam is heated to evaporate mercury and obtain gold. Thus, the highly volatile mercury can be absorbed through inhalation, resulting in adverse health effects. Urinalysis can be used to detect mercury, which is excreted in urine and feces, and correlate exposure with toxic effects. The current gold standard analytical methods are based on fluorescence or inductively coupled plasma mass spectrometry methods, but are expensive, time consuming, and are not easily accessible in countries where testing is needed. In this work, we report on a miniature electrochemical sensor that can rapidly detect mercury in urine at levels well below the US Biological Exposure Index (BEI) limit of 50 ppb (μg/L). The sensor is based on a thin-film gold electrode and anodic stripping voltammetry electroanalytical approach. The sensor successfully detected mercury at trace levels in urine, with a limit of detection of ∼15 ppb Hg in the linear range of 20–80 ppb. With the low-cost disposable sensors and portable instrumentation, it is well suited for point-of-care applications.