Elucidating the redox cycle of environmental phosphorus using ion chromatography.

Historically, it was assumed that reactive, inorganic phosphorus present in pristine environments was solely in the form of orthophosphate. However, this assumption contradicts theories of biogenesis and the observed metabolic behavior of select microorganisms. This paper discusses the role of ion chromatography (IC) in elucidating the oxidation-reduction cycle of environmental phosphorus. These methods employ suppressed-IC, coupled with tandem conductivity and electrospray mass spectrometry detectors to identify and quantify phosphorus oxyanions in natural water, synthetic cosmochemical, and biological samples. These techniques have been used to detect phosphite and orthophosphate in geothermal hot springs. Hypophosphite, phosphite, and orthophosphate have been detected in synthetic schreibersite corrosion samples, and termite extract supernatant. Synthetic schreibersite corrosion samples were also analyzed for two poly-phosphorus compounds, hypophosphate and pyrophosphate, and results show these samples did not contain concentrations above the 1.3 and 2.0 µM respective 3σ limit of detection. These methods are readily adaptable to a variety of matrices, and contribute to the elucidation of the oxidation-reduction cycle of phosphorus oxyanions in the environment. In contrast to most studies, these techniques have been used to show that phosphorus actively participates in redox processes in both the biological and geological world.

Ion chromatography detection of fluoride in calcium carbonate.

Fluoride in aquatic systems is increasing due to anthropogenic pollution, but little is known about how this fluoride affects organisms that live in and around aquatic habitats. Fluoride can bioaccumulate in structures comprised of calcium carbonate, such as shells and skeletons of both freshwater and saltwater species as diverse as snails, corals, and coccolithophorid algae. In this article, ion chromatography (IC) techniques are developed to detect and quantify fluoride in a matrix of calcium carbonate. Solid samples are dissolved in hydrochloric acid, pretreated to remove the majority of the chloride ions, and then analyzed using IC. With these methods, the 3σ limit of detection is 0.2 mg of fluoride/kg of calcium carbonate.

Simultaneous detection of H2(+) with larger ions using Fourier transform mass spectrometry.

Laser-induced desorption coupled with Fourier transform mass spectrometry (FTMS) has proven to be a useful technique for the studies of chemical reactions that occur in monolayers adsorbed on solid surfaces. The high sensitivity and ultrahigh mass resolution have been extremely useful in the study of reactions in complex monolayer mixtures made up of molecular species with m/z between 15 and 1000. For studies of hydrocarbon reactions on surfaces, such as would be useful for fundamental studies of catalytic processes on transition metal surfaces, it is extremely useful to be able to detect molecular hydrogen desorbing from a surface simultaneously with higher molecular weight reactants and reaction products. However, simultaneous detection of molecular hydrogen and higher molecular weight species presents a unique challenge for FTMS, as a result not only of the high cyclotron frequency of the H2(+) molecular ion but also as a result of z-ejection and proton- and charge-transfer reactions. We characterize the issues associated with direct simultaneous detection of molecular hydrogen using FTMS and demonstrate the experimental conditions necessary for the simultaneous detection of hydrogen and larger species such as argon and cyclohexane.

Detection of phosphorus oxyanions in synthetic geothermal water using ion chromatography-mass spectrometry techniques.

Recent developments in microbiology suggest that reduced inorganic phosphorus oxyanions, including hypophosphite and phosphite, may be present in nature. These studies have inspired the development of specific and sensitive methods that detect phosphorus oxyanions in natural water. This paper will discuss a new technique that couples suppressed conductivity ion chromatography (Dionex AS17 analytical column and potassium hydroxide eluent) with electrospray mass spectrometry (IC/MS) with limits of detection nearly 200 times lower than those reported using suppressed conductivity detection. The technique was optimized for the detection of hypophosphite, phosphite, and phosphate in a synthetic geothermal water matrix. Samples were pre-treated with silver and sulfonic acid cartridges, and injection loop sizes as large as 800microl were employed to enhance instrument sensitivity. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma limits of detection of 0.011, 0.0020, and 0.029microM for hypophosphite, phosphite, and phosphate, respectively.

Mass spectrometer characterization of halogen gases in air at atmospheric pressure.

We have developed a new interface for a commercial ion trap mass spectrometer equipped with APCI capable of real-time measurements of gaseous compounds with limits of detection on the order of pptv. The new interface has been tested using the detection of Br2 and Cl2 over synthetic seawater ice at atmospheric pressure as a model system. A mechanical pump is used to draw gaseous mixtures through a glass manifold into the corona discharge area, where the molecules are ionized. Analysis of bromine and chlorine in dry air show that ion intensity is affected by the pumping rate and the position of the glass manifold. The mass spectrometer signals for Br2 are linear in the 0.1-10.6 ppbv range, and the estimated 3sigma detection limit is 20 pptv. The MS signals for Cl2 are linear in the 0.2-25 ppbv range, and the estimated 3sigma detection limit is 1 ppbv. This new interface advances the field of analytical chemistry by introducing a practical modification to a commercially available ion trap mass spectrometer that expands the available methods for performing highly specific and sensitive measurements of gases in air at atmospheric pressure.

Detection of hypophosphite, phosphite, and orthophosphate in natural geothermal water by ion chromatography.

Current doctrine states that phosphorus is incorporated into cells in the pentavalent(V) oxidation state as orthophosphate. However, recent studies show that microorganisms contain enzymes used to metabolize reduced forms of phosphorous, including phosphite(III) and hypophosphite(I), which suggests that there is a natural source for these chemical species. This paper will discuss suppressed conductivity ion chromatography methods developed to detect hypophosphite, phosphite, and orthophosphate in a geothermal water matrix containing fluoride, chloride, bromide, nitrate, hydrogen carbonate and sulfate. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma detection limits of 0.83, 0.39, and 0.35 microM for hypophosphite, phosphite, and orthophosphate, respectively.