Matthew L. Magnuson

Perchlorate levels in samples of sodium nitrate fertilizer derived from Chilean caliche

Paleogeochemical deposits in northern Chile are a rich source of naturally occurring sodium nitrate (Chile saltpeter). These ores are mined to isolate NaNO3 (16-0-0) for use as fertilizer. Coincidentally, these very same deposits are a natural source of perchlorate anion (ClO4-). At sufficiently high concentrations, perchlorate interferes with iodide uptake in the thyroid gland and has been used medicinally for this purpose. In 1997, perchlorate contamination was discovered in a number of US water supplies, including Lake Mead and the Colorado River. Subsequently, the Environmental Protection Agency added this species to the Contaminant Candidate List for drinking water and will begin assessing occurrence via the Unregulated Contaminants Monitoring Rule in 2001. Effective risk assessment requires characterizing possible sources, including fertilizer. Samples were analyzed by ion chromatography and confirmed by complexation electrospray ionization mass spectrometry. Within a lot, distribution of perchlorate is nearly homogeneous, presumably due to the manufacturing process. Two different lots we analyzed differed by 15%, containing an average of either 1.5 or 1.8 mg g-1. Inadequate sample size can lead to incorrect estimations; 100-g samples gave sufficiently consistent and reproducible results. At present, information on natural attenuation, plant uptake, use/application, and dilution is too limited to evaluate the significance of these findings, and further research is needed in these areas.

Perchlorate uptake by salt cedar (Tamarix ramosissima) in the Las Vegas Wash riparian ecosystem.

Perchlorate ion (ClO4-) has been identified in samples of dormant salt cedar (Tamarix ramosissima) growing in the Las Vegas Wash. Perchlorate is an oxidant, but its reduction is kinetically hindered. Concern over thyroid effects caused the Environmental Protection Agency (EPA) to add perchlorate to the drinking water Contaminant Candidate List (CCL). Beginning in 2001, utilities will look for perchlorate under the Unregulated Contaminants Monitoring Rule (UCMR). In wood samples acquired from the same plant growing in a contaminated stream, perchlorate concentrations were found as follows: 5-6 microg g(-1) in dry twigs extending above the water and 300 microg g(-1) in stalks immersed in the stream. Perchlorate was leached from samples of wood, and the resulting solutions were analyzed by ion chromatography after clean-up. The identification was confirmed by electrospray ionization mass spectrometry after complexation of perchlorate with decyltrimethylammonium cation. Because salt cedar is regarded as an invasive species, there are large scale programs aimed at eliminating it. However, this work suggests that salt cedar might play a role in the ecological distribution of perchlorate as an environmental contaminant. Consequently, a thorough investigation of the fate and transport of perchlorate in tamarisks is required to assess the effects that eradication might have on perchlorate-tainted riparian ecosystems, such as the Las Vegas Wash. This is especially important since water from the wash enters Lake Mead and the Colorado River and has the potential to affect the potable water source of tens of millions of people as well as irrigation water used on a variety of crops, including much of the lettuce produced in the USA.

Speciation of Arsenic Compounds in Drinking Water by Capillary Electrophoresis with Hydrodynamically Modified Electroosmotic Flow Detected Through Hydride Generation Inductively Coupled Plasma Mass Spectrometry With a Membrane Gas–Liquid Separator

Capillary electrophoresis (CE) was used to speciate four environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid and dimethylarsinic acid. Hydride generation (HG) was used to convert the species into their respective hydrides. The hydride species were detected with inductively coupled plasma mass spectrometry. The HG unit utilized a microporous PTFE tube as a gas–liquid separator. The injection mode for CE was electrokinetic in conjunction with the novel use of hydrodynamically modified electroosmotic flow (HMEOF). In HMEOF, the electroosmotic flow is modified by applying hydrodynamic pressure opposite to the direction of the electroosmotic flow. HMEOF provides the capability of injecting increased quantities of analyte by offsetting the electroosmotic flow, which limits conventional electrokinetic injection. In order to correct for imprecisions in the electrokinetic injection in matrices of different ionic strength, the use of a surrogate for the injection of arsenic species was investigated. Germanium was investigated because it forms a hydride and has a low natural occurrence. The separation also utilized HMEOF, which allowed for greater freedom in buffer choice. The detection limits in distilled, de-ionized water were 25, 6, 9 and 58 ppt for the four species listed above, respectively. The detection limit was calculated from 3.14 σ n-1 of seven replicate injections and represents the precision of measuring the ratio of the area of the arsenic peaks to the area of a germanium surrogate peak. Standard addition was used to determine arsenate in drinking water samples. Recoveries of arsenite and arsenate from drinking water samples are reported using germanium as a surrogate to correct for sampling bias of the electrokinetic injection.

Initial Characterization of the Hemolysin Stachylysin from Stachybotrys chartarum

ABSTRACT Stachybotrys chartarum is a toxigenic fungus that has been associated with human health concerns, including pulmonary hemorrhage and hemosiderosis. This fungus produces a hemolysin, stachylysin, which in its apparent monomeric form has a molecular mass of 11,920 Da as determined by matrix-assisted laser desorption ionization–time of flight mass spectrometry. However, it appears to form polydispersed aggregates, which confounds understanding of the actual hemolytically active form. Exhaustive dialysis or heat treatment at 60°C for 30 min inactivated stachylysin. Stachylysin is composed of about 40% nonpolar amino acids and contains two cysteine residues. Purified stachylysin required more than 6 h to begin lysing sheep erythrocytes, but by 48 h, lysis was complete. Stachylysin also formed pores in sheep erythrocyte membranes.

Determination of bromate in drinking waters by ion chromatography with inductively coupled plasma mass spectrometric detection

Abstract Bromate is a disinfection by-product in drinking water, formed during the ozonation of source water containing bromide. An inductively coupled plasma mass spectrometer is combined with an ion chromatograph for the analysis of bromate in drinking waters. Three chromatographic columns are evaluated in terms of detection limits, analysis time and tolerance to potentially interfering inorganic anions. The detection limits for all columns are in the 1–2 μg/l range for the direct analysis of bromate. A 5-min analysis time was achieved using a Dionex AG10 column and 100 mM NaOH as the eluent. Recoveries for bromate in fortified samples containing chloride (1000 ppm) or nitrate (50 ppm) were 96–107%. Recoveries for bromate in fortified samples containing sulfate (1000 ppm) were 91–124%. The R.S.D. values for drinking water analyses are in the 2–6% range. A 1.8-ml sample was preconcentrated on a Dionex AG10 column. This system produced bromate detection limits in the 0.1–0.2 μg/l range. Coupling the AG10 preconcentrator column with an ultrasonic nebulizer produced a detection limit of 50 ppt for bromate. The precision for samples which are preconcentrated is degraded due to an adjacent peak interfering with integration of the bromate peak.

Speciation of Selenium and Arsenic Compounds by Capillary Electrophoresis With Hydrodynamically Modified Electroosmotic Flow and On-line Reduction of Selenium(VI) to Selenium(IV) With Hydride Generation Inductively Coupled Plasma Mass Spectrometric Detection

Capillary electrophoresis (CE) with hydride generation inductively coupled plasma mass spectrometry was used to determine four arsenicals and two selenium species. Selenate (SeVI) was reduced on-line to selenite (SeIV) by mixing the CE effluent with concentrated HCl. A microporous PTFE tube was used as a gas-liquid separator to eliminate the 40Ar37Cl and 40Ar35Cl interference from 77Se and 75As, respectively. The direction of the electroosmotic flow during CE was reversed with hydrodynamic pressure, which allowed increased freedom of buffer choice. For conventional pressure injection, method detection limits for SeIV and SeVI based on seven replicate injections were 10 and 24 pg, respectively. Recoveries of SeIV and SeVI in drinking water were measured.

Speciation of arsenic compounds by ion chromatography with inductively coupled plasma mass spectrometry detection utilizing hydride generation with a membrane separator

Ion chromatography (IC) was used to speciate four of the environmentally significant, toxic forms of arsenic: arsenite, arsenate, monomethylarsonic acid, and dimethylarsinic acid. Hydride generation (HG) was used to convert the species to their respective hydrides. These hydride species were detected with ICP-MS. The gas–liquid separator for the HG unit was based on microporous PTFE tubing. Two novel features which reduce noise are incorporated into the membrane-based HG unit: firstly, gas is added to the liquid stream prior to entering the membrane, and secondly, the flow of carrier gas through the gas–liquid separator forms a ‘feedback’ loop. Absolute detection limits based on 3.14σ from 7 replicates for the four arsenic species listed above were 0.6, 3.1, 1.1, and 0.7 pg, respectively. The overall IC–HG–ICP-MS system produced RSD values of 1–6% over 30 min and 2–6% over a week for the four compounds. Two saline reference materials, NASS-4 and SLEW-2 (National Research Council of Canada), were analysed to determine concentrations of the four arsenic species, and the sum of the arsenic concentration was compared with the certified total arsenic value for each of the reference materials.

Analysis of hydroponic fertilizer matrixes for perchlorate: comparison of analytical techniques.

Seven retail hydroponic nitrate fertilizer products, two liquid and five solid, were comparatively analyzed for the perchlorate anion (ClO4-) by ion chromatography (IC) with suppressed conductivity detection, complexation electrospray ionization mass spectrometry (cESI-MS), normal Raman spectroscopy, and infrared spectroscopy using an attenuated total reflectance crystal (ATR-FTIR) coated with a thin film of an organometallic ion-exchange compound. Three of the five solid products were found by all techniques to contain perchlorate at the level of approximately 100-350 mg kg(-1). The remaining products did not contain perchlorate above the detection level of any of the techniques. Comparative analysis using several analytical techniques that depend on different properties of perchlorate allow for a high degree of certainty in both the qualitative and quantitative determinations. This proved particularly useful for these samples, due to the complexity of the matrix. Analyses of this type, including multiple spectroscopic confirmations, may also be useful for other complicated matrixes (e.g., biological samples) or in forensic/regulatory frameworks where data are likely to be challenged. While the source of perchlorate in these hydroponic products is not known, the perchlorate-to-nitrate concentration ratio (w/w) in the aqueous extracts is generally consistent with the historical weight percent of water soluble components in caliche, a nitrate-bearing ore found predominantly in Chile. This ore, which is the only well-established natural source of perchlorate, is mined and used, albeit minimally, as a nitrogen source in some fertilizer products.

Survey of bottled waters for perchlorate by electrospray ionization mass spectrometry (ESI-MS) and ion chromatography (IC)†

Perchlorate has been identified in ground and surface waters around the USA including some that serve as supplies for drinking water. Because perchlorate salts are used as solid oxidants in rockets and ordnance, water contamination may occur near military or aerospace installations or defense industry manufacturing facilities. This ion has been added to the Environmental Protection Agencys Contaminant Candidate List and the Unregulated Contaminant Monitoring Rule. Concern over perchlorate has prompted many residents in affected areas to switch to bottled water; however, bottled waters have not previously been examined for perchlorate contamination. Should the EPA promulgate a regulation for municipal water systems, US law requires the Food and Drug Administration to take action on bottled water. Methods will therefore be required to determine perchlorate concentrations not only in tap water, but also in bottled waters. Ion chromatography (IC) is the primary technique used for its analysis in drinking water, but it does not provide a unique identification. Confirmation by electrospray ionization mass spectrometry (ESI-MS) can serve in this capacity. The ESI-MS method can be applied to these products, but it requires an understanding of matrix effects, especially of high ionic strength that can suppress electrospray. When using methyl isobutyl ketone (MIBK) as the extraction solvent, the ESI-MS method can reach lower limits of detection of 6 ng ml −1 for some bottled waters. However, dilution required to negate ionic strength effects in mineral waters can raise this by a factor of 10 or more, depending on the sample. Decyltrimethylammonium cation (added as the bromide salt) is used to produce an ion pair that is extracted into MIBK. After extraction, the sum of the peak areas of the ions C10H21NMe3(Br)(ClO4)− (m/z = 380) and C10H21NMe3(ClO4)2− (m/z = 400) is used to quantitate perchlorate. Standard additions are used to account for most of the matrix effects. In this work, eight domestic brands and eight imported brands of bottled water were comparatively analyzed by the two techniques. For comparison, a finished potable water known to contain perchlorate was also tested. None of the bottled waters were found to contain any perchlorate within the lower limit of detection for the IC method. Recoveries on spiked samples subjected to the IC method were ≥98%. Published in 2000 for SCI by John Wiley & Sons, Ltd

Characterization of Cryptosporidium parvum by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

ABSTRACT Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) was used to investigate whole and freeze-thawed Cryptosporidium parvum oocysts. Whole oocysts revealed some mass spectral features. Reproducible patterns of spectral markers and increased sensitivity were obtained after the oocysts were lysed with a freeze-thaw procedure. Spectral-marker patterns forC. parvum were distinguishable from those obtained forCryptosporidium muris. One spectral marker appears specific for the genus, while others appear specific at the species level. Three different C. parvum lots were investigated, and similar spectral markers were observed in each. Disinfection of the oocysts reduced and/or eliminated the patterns of spectral markers.