Determination of perchlorate at parts-per-billion levels in plants by ion chromatography

A method for the analysis of perchlorate in plants was developed, based on dry weight, and applied to the analysis of plant organs, foodstuffs, and plant products. The method reduced greatly the ionic interferences in water extracts of plant materials. The high background conductivity, due to the plant matrix, was reduced sufficiently to allow quantitation of perchlorate with little or no matrix interference. Ion chromatography (IC) on a microbore AS16 anion-exchange column and a conductivity detector was used for separation and detection of perchlorate from the ionic plant extract. The extract was heated to precipitate proteins, centrifuged, exposed to alumina, and filtered through a cartridge filled with divinylbenzene to yield a water clear extract for IC analysis, even from highly colored solutions. Heating the extract and treatment with alumina reduced substantially the ionic content of the extracts without loss of perchlorate.     

Preconcentration/preelution ion chromatography for the determination of perchlorate in complex samples

The determination of perchlorate in complex matrices by ion chromatography (IC) with an online preconcentration and preelution technique is discussed. The method was applied to different sample types containing large concentrations of matrix anions that would otherwise interfere with analysis via conventional IC. The present approach was highly effective in removing most of the matrix anions and was thus resistant to the interferences commonly encountered in a high ionic strength background. Method performance was evaluated by analyzing for low-level perchlorate in synthetic high ionic strength solutions, tissue extracts, and hydroponic nitrate fertilizer samples. Not only is it easier to practice the present method compared to USEPA Method 314.0, but for most of these samples the present approach provided equal to or better recovery of perchlorate than Method 314.0. With a sample of specific conductance 12,650 μS cm⁻¹, for example, the present method provided a perchlorate recovery of 101% at the 25 μg L⁻¹ level versus 89% by EPA Method 314.0. Method detection limits of perchlorate in hydroponic fertilizer samples with this method (130-190 μg kg⁻¹) are the lowest thus far reported.     

Quantitative analysis of perchlorate in extracts of whole fish homogenates by ion chromatography: comparison of suppressed conductivity detection and electrospray ionization mass spectrometry

The perchlorate anion (ClO ₄ ^– ) is an anthropogenic contaminant of increasing concern in water supplies, and has been shown to disrupt thyroid activity. Most perchlorate analyses are currently carried out by ion chromatography (IC) with suppressed conductivity detection (SCD). While this procedure has been demonstrated to provide acceptable performance for analysis of water samples, the determination of perchlorate in high-conductivity aqueous extracts of plant or animal material is not readily accomplished by IC-SCD unless lengthy cleanup protocols are applied. With the addition of electrospray ionization mass spectrometry (ESI-MS) to IC, it was hypothesized that the interference imposed by various ionic species could be significantly reduced without the need for purification; however, the analysis of perchlorate in relatively unpurified extracts of biologically derived homogenates by IC-ESI-MS has not previously been described in the literature. The research presented here represents a comparison of the capabilities of IC-SCD and IC-ESI-MS to detect perchlorate in reagent water and in crude extracts of perchlorate-exposed fish (threespine stickleback, Gasterosteus aculeatus). ESI-MS was found to compare favorably to SCD for the detection of perchlorate in deionized water, and to exceed SCD performance in perchlorate analysis of fish-derived extracts.     

A cleanup method for perchlorate determination in urine

There is increasing concern about perchlorate exposure because of perchlorate's potential effects on organisms as a thyroid hormone disruptor, as well as its contamination of the environment being much more widespread than previously thought. Perchlorate is excreted primarily into urine, therefore, evaluating perchlorate residues in urine should be a reasonable approach for determining exposure and if successful could be used as an effective biomarker of perchlorate exposure. Since the presence of ions and other biomolecules in matrices like urine usually confounds accurate determination of perchlorate by ion chromatography, it is necessary to develop efficient methods for perchlorate determination in these matrices. We developed a method that reduces the background signal of urine, which is typically the problem with the analysis of biological fluids and tissues by ion chromatography. Relatively high recovery of perchlorate was shown. In cow urine samples spiked with perchlorate at 2.5, 10, and 100 μg/L, perchlorate recoveries were 67% ± 2.5, 77% ± 3.6, and 81% ± 1.7 (mean ± S.D.), respectively. In addition, the detection limit was as low as 12.6, 12.3, and 18.7 μg/L in cow, vole, and human urine samples, respectively.     

Analytical methods for selected emerging contaminants in human matrices—a review

Emerging contaminants are a broad category of chemicals, previously unknown or unrecognized as being of concern, but which, because of their potential health effects associated with human exposure, are under increasing scrutiny. To accurately measure their levels in biological matrices, specific and sensitive analytical methods have recently been developed. We have reviewed here the methods used for analysis of selected emerging organic contaminants, for example metabolites of organophosphate triesters, metabolites of new phthalates or phthalate substitutes, perchlorate, organic UV filters, and polycyclic siloxanes, in human matrices. Although the use of new techniques and approaches has been emphasized, we also acknowledge methods previously used for other contaminants and adapted for the emerging contaminants listed above. In all cases, chromatography and mass spectrometry were the techniques of choice, because of their selectivity and sensitivity for measurements at ng?g^?1 levels. Critical issues and challenges have been discussed, together with recommendations for further improvement in particular cases (e.g. metabolites of phthalates or their substitutes). In particular, the use of labeled internal standards, the availability of certified reference materials, and the need for interlaboratory comparison exercises are key aspects of further development of this field of research.

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.     

Considerations involved with the use of semipermeable membrane devices for monitoring environmental contaminants

Semipermeable membrane devices (SPMDs) are used with increasing frequency, and throughout the world as samplers of organic contaminants. The devices can be used to detect a variety of lipophilic chemicals in water, sediment/soil, and air. SPMDs are designed to sample nonpolar, hydrophobic chemicals. The maximum concentration factor achievable for a particular chemical is proportional to its octanol-water partition coefficient. Techniques used for cleanup of SPMD extracts for targeted analytes and for general screening by full-scan mass spectrometry do not differ greatly from techniques used for extracts of other matrices. However, SPMD extracts contain potential interferences that are specific to the membrane-lipid matrix. Procedures have been developed or modified to alleviate these potential interferences. The SPMD approach has been demonstrated to be applicable to sequestering and analyzing a wide array of environmental contaminants including organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dioxins and dibenzofurans, selected organophosphate pesticides and pyrethroid insecticides, and other nonpolar organic chemicals. We present herein an overview of effective procedural steps for analyzing exposed SPMDs for trace to ultra-trace levels of contaminants sequestered from environmental matrices.     

Optimization of operating conditions for the determination of perchlorate in biological samples using preconcentration/preelution ion chromatography

Perchlorate originates as a contaminant in the environment from the use of salts in the manufacture of solid rocket fuels and munitions. Monitoring potential perchlorate contamination in the environment is of interest, however, very few analytical methods have been developed for perchlorate determination in biological samples. Analysis of complex samples by ion chromatography is complicated by matrix components that can interfere with perchlorate determination. However, a recently developed preconcentration/preelution (PC/PE) ion chromatography method has demonstrated the capability to analyze certain complex samples such as high salinity water, milk, and hydroponic fertilizers. The ability of this method to reduce sample background and lower detection limits in ion chromatography for various biological samples was evaluated in this study. The PC/PE method was applicable to the analysis of kidneys, livers, zebrafish, quail eggs, lettuce, and urine. Optimal operating conditions were determined for each matrix. Ranges of optimal wash volumes were shorter when 15 mM NaOH prewash solutions were used compared with 10mM and good recovery was achieved for most matrices with an injection period > or =60s. Prewash solution concentration did not appear to significantly affect matrix background. The PC/PE method was capable of reducing sample background when compared to EPA Method 314.0, which resulted in detection limits, with the exception of zebrafish and urine, that were two-fold lower than those achieved with EPA Method 314.0.     

Stability of low levels of perchlorate in drinking water and natural water samples

Perchlorate ion (ClO₄⁻) is an environmental contaminant of growing concern due to its potential human health effects, impact on aquatic and land animals, and widespread occurrence throughout the United States. The determination of perchlorate cannot normally be carried out in the field. As such, water samples for perchlorate analysis are often shipped to a central laboratory, where they may be stored for a significant period before analysis. The stability of perchlorate ion in various types of commonly encountered water samples has not been generally examined—the effect of such storage is thus not known. In the present study, the long-term stability of perchlorate ion in deionized water, tap water, ground water, and surface water was examined. Sample sets containing approximately 1000, 100, 1.0, and 0.5 μg l⁻¹ perchlorate ion in deionized water and also in local tap water were formulated. These samples were analyzed by ion chromatography for perchlorate ion concentration against freshly prepared standards every 24 h for the first 7 days, biweekly for the next 4 weeks, and periodically after that for a total of 400 or 610 days for the two lowest concentrations and a total of 428 or 638 days for the high concentrations. Ground and surface water samples containing perchlorate were collected, held and analyzed for perchlorate concentration periodically over at least 360 days. All samples except for the surface water samples were found to be stable for the duration of the study, allowing for holding times of at least 300 days for ground water samples and at least 90 days for surface water samples.     

Mass spectrometry applied to the analysis of estrogens in the environment

Environmental analytical chemistry has recently changed focus from analysis of non-polar, persistent contaminants (e.g. polychlorinated biphenyls and dioxins) to more polar and labile compounds that interfere with biological processes. For example, natural and synthetic estrogens and their metabolites have been detected in sewage treatment plant effluents at nanogram/liter concentrations that are similar to those at which both total sex reversal and intersex (containing both testes and ova) is induced in fish exposed to these compounds in laboratory experiments. The development of techniques for the analysis of natural and synthetic estrogens in biological fluids (i.e. serum and urine) has been a priority in the biomedical field. However, the recent recognition that estrogen hormones are contaminants in the environment that may contribute to endocrine disruption has focused attention on the need for highly sensitive and specific techniques that are applicable for trace analysis in complex environmental matrices. Three optimized mass spectrometric protocols have been developed for the determination and quantitation of steroid hormones in environmental matrices using gas chromatography/tandem mass spectrometry (GC/MS/MS), liquid chromatography/mass spectrometry selected ion monitoring, (LC/MS - SIM) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The advantages and disadvantages of each method are presented.     

Selective method for the analysis of perchlorate in drinking waters at nanogram per liter levels, using two-dimensional ion chromatography with suppressed conductivity detection

The United States Environmental Protection Agency (EPA) collected drinking water occurrence data for perchlorate in the Unregulated Contaminant Monitoring Regulation (UCMR 1; 2001-2005) using EPA Method 314.0. To address the interest in increasing sensitivity and selectivity for the analysis of perchlorate, three new methods, EPA Methods 314.1, 331.0 and 332.0, were subsequently published by EPA for the analysis of perchlorate in drinking water. In 2006, an automated two-dimensional ion chromatography (2D-IC) method for measuring perchlorate with suppressed conductivity detection was developed. Two-dimensional IC is essentially an automated "heart-cutting", column concentration and matrix elimination technique. In the first dimension, a large sample volume is injected onto a first separation column and the separated matrix ions are diverted to waste while the analyte(s) of interest are selectively cut, trapped and concentrated in a concentrator column. In the second dimension, the contents from the concentrator column are eluted onto a second analytical column for separation and quantitation of the analyte(s) of interest. Incorporation of two columns with different affinities for the analyte(s) in a single analysis can provide comparable selectivity and superior sensitivity to a method using second column confirmation in a second separate analysis step. Use of this approach led to the development of a new, highly sensitive and selective 2D-IC, suppressed conductivity method with a Lowest Concentration Minimum Reporting Level (LCMRL) of 55 ng/L for perchlorate in drinking water samples. This new method has comparable sensitivity and selectivity and is simpler and more economical than IC-mass spectrometric (MS) or IC-MS-MS techniques. The method is now being prepared for publication as EPA Method 314.2.     

Determination of perchlorate in drinking water by ion chromatography using macrocycle-based concentration and separation methods

Macrocycle-based ion chromatography provides a convenient, reliable method for the determination of perchlorate ion, which is currently of great interest to the environmental community. This study shows that effective perchlorate determinations can be made using standard conductimetric detection by combining an 18-crown-6-based mobile phase with an underivatized reversed-phase mobile phase ion chromatography (MPIC) column. One unique feature of this method is the flexibility in column capacity that is achieved through simple variations in eluent concentrations of 18-crown-6 and KOH, facilitating the separation of target analyte anions such as perchlorate. Using a standard anion exchange column as concentrator makes possible the determination of perchlorate as low as 0.2 ug/L in low ionic strength matrices. Determination of perchlorate at the sub-ug/L level in pure water and in spiked local city hard water samples with high background ion concentrations can be achieved this way. However, like other IC techniques, this method is challenged to achieve analyses at the ug/L level in the demanding high ionic strength matrix described by the United States Environmental Protection Agency (EPA) (1,000 mg/L chloride, sulfate and carbonate). We approached this challenge by use of the Cryptand C1 concentrator column, provided by Dionex Corporation, to effectively preconcentrate perchlorate while reducing background ion concentrations in the high ionic strength matrix. The retention characteristics of the concentrator column were studied in order to maximize its effectiveness for perchlorate determinations. The method makes possible the determination of perchlorate at the 5 ug/L level in the highest ionic strength matrix described by the EPA.     

Determination of inorganic ions in drinking water by ion chromatography

Ion chromatography (IC) is now a well established methodology for the analysis of ionic species. The technique is applicable to the determination of a wide range of solutes in many sample types, although the determination of inorganic ions in drinking water continues to be the most widely used application of ion chromatography. Many regulatory and standard organizations, such as ASTM, AOAC, ISO, and US EPA, have approved methods of analysis based upon IC, most of which have been published within the last 10 years. Recent developments in the field of IC, such as the use of higher capacity columns, larger loop injections, more complex sample preparation and detection schemes, have been incorporated into new approved methods to allow the determination of inorganic contaminants, such as bromate, perchlorate, and chromate, at low μg/l levels in drinking waters. IC appears certain to remain an important technique for drinking water analysis and new methods based on IC will continue to be developed as more inorganic contaminants become regulated at lower limits in the future.     

Matrix interference free determination of perchlorate in urine by ion association-ion chromatography-mass spectrometry

Quantitative measurement of perchlorate in biological fluids is of importance to assess its toxicity and to study its effects on the thyroid gland. Whenever possible, urine samples are preferred in toxicologic/epidemiologic studies because sample collection is non-invasive. We present here a pretreatment method for the determination of perchlorate in urine samples that lead to a clean matrix. Urine samples, spiked with isotopically labeled perchlorate, are exposed to UV to destroy/decompose organic molecules and then sequentially treated with an H⁺-form cation exchange resin to remove protolyzable compounds, with ammonia to raise the pH to 10-11 and finally passed through a mini-column of basic alumina to remove the color and other organic matter. After filtration through a 0.45 μm syringe filter, the sample thus prepared can be directly injected into an ion chromatograph (IC). We use ion association-electrospray ionization-mass spectrometry (ESI-MS) to detect and quantify perchlorate. The proposed sample preparation method leads to excellent limits of detection (LOD's) for perchlorate since there is essentially no dilution of sample and the matrix effects are eliminated. Results of urine samples from both men and women volunteers are reported for perchlorate, as well as for iodide and thiocyanate, which are generally present at much higher concentrations and for which a “dilute and shoot” approach is adequate. The limit of detection (S/N = 3) for iodide, thiocyanate and perchlorate by the present method was 0.40, 0.10 and 0.080 μg l⁻¹, respectively.     

Identification and determination of inorganic anions in real extracts from pre- and post-blast residues by capillary electrophoresis

Fast, selective, and sensitive analysis of inorganic anions is compulsory for the identification of explosives in post-blast or environmental samples. For the last twenty years, capillary electrophoresis (CE) has become a valuable alternative to ion chromatography (IC) for the analysis of inorganic-based explosives because of its low running costs and its simplicity of use. This article focuses on the development and validation of a CE method for the simultaneous analysis of 10 anions (chloride, nitrite, nitrate, thiosulphate, perchlorate, chlorate, thiocyanate, carbonate, sulphate, and phosphate) which can be found in post-blast residues, plus for the first time azide anion, possibly present in the composition of detonators, and the internal standard (formate) in 20 min total runtime. Intermediate precisions were 2.11% for normalized areas and 0.72% for normalized migration times. Limits of detection close to 0.5 ppm for all anions were obtained with the use of preconcentration techniques, thanks to a fast and simple sample preparation allowing the analysis of a large variety of matrices with the developed generic CE method. The matrix effects were statistically studied for the first time in the explosive field for different matrices, containing interfering anions and cations, sometimes at high levels. In fact, no significant matrix effect occurred (tests with blank matrix extracts of soil, cloth, glass, plastic, paper, cotton, and metal). Finally, analyses of real post-blast residues and real detonator extracts were performed. The CE results were compared with those obtained with the IC method used routinely and showed excellent correlation.     

Rapid detection of perchlorate in groundwater using capillary electrophoresis

Summary Perchlorate is a groundwater contaminant originating from facilities that manufacture and test solid rocket fuel. A new technology, capillary electrophoresis, has the potential to measure perchlorate rapidly and inexpensively in water samples. With its speed and simplicity, this method would complement existing methods. The perchlorate anion is routinely detected in water samples using high performance ion exchange chromatography, a very sensitive yet time consuming and expensive method. In this work, the parameters for detection of perchlorate are optimized to permit detection of 0.400 mgL⁻¹ perchlorate in a standard solution. The usefulness of this technology is demonstrated for measuring perchlorate in several ground-water samples from the Western United States. The results demonstrate that CE can be used to rapidly screen environmental samples for perchlorate at intermediate to high levels (greater than 0.400 mgL⁻¹). This technique allows faster, easier screening of potential contamination sites and could complement the use of ion exchange chromatography for groundwater testing.     

Investigating the antimony determination in environmental samples by NAA

In recent years, environmental concerns regarding antimony have grown considerably due to anthropogenic processes that have resulted in increasing concentration of Sb in the environment, and also because of its impacts and possible adverse effects to living organisms. Several techniques have been used, to obtain reliable results for Sb, since Sb is present at low level concentration, requiring analytical instrumentation with low detection limits. The neutron activation analysis (NAA) technique has a high metrological level for the determination of several elements in different matrices. However, Sb determination in environmental and biological samples presents some analytical difficulties due to its low concentrations and gamma ray spectrum interferences. The objective of this research was to study on Sb determination in environmental reference materials by NAA. Ten environmental reference materials were selected and analyzed using long period irradiation at IEA-R1 research nuclear reactor. The induced gamma activities of ¹²²Sb and ¹²⁴Sb were measured. Relative errors of the results demonstrated that the accuracy depends mainly on Sb radioisotope measured, the decay time for counting and the sample composition.     

Simultaneous determination of trace oxyhalides and haloacetic acids using suppressed ion chromatography-electrospray mass spectrometry

A new analytical procedure for the simultaneous determination of trace oxyhalides and haloacetic acids (HAs) in drinking water and aqueous soil extracts is described. The method uses micro-bore ion chromatography (IC) coupled with suppressed conductivity (SC) and electrospray ionization mass spectrometric detection (ESI-MS). The IC-SC-ESI-MS system included a secondary flow of 100% MeOH, which was added to the column eluate (post-suppressor) and resulted in a significant increase in sensitivity for all analytes. All ESI-MS parameters were optimized for HA analysis and sensitivity quantitatively compared to suppressed conductivity. Full analytical performance characteristics for the developed method are presented for monochloro-, monobromo-, dichloro-, dibromo-, trichloro-, bromochloro, chlorodifluoro-, trifluoro-, dichlorobromo- and dibromochloroacetic acid, as well as the oxyhalides iodate, bromate, chlorate and perchlorate. In the case of the HAs, an optimised 25-fold SPE preconcentration method meant all analytes could be readily detected well below the USEPA 60 μg/L regulatory limit using conductivity and/or ESI-MS. The IC-ESI-MS method was applied to the determination of oxyhalides and HAs in both soil extracts and drinking water samples. Soil samples were extracted using ultra pure water with subsequent determination of perchlorate at 1.68 μg/g of soil. A drinking water sample containing HAs was preconcentrated using LiChrolut EN solid phase extraction cartridges with subsequent sulphate and chloride removal. Total HAs were determined at 13 μg/L.     

Rapid Methods in Analytical Chemistry

This article presents the most recent research in analytical chemistry concerning the development of rapid methodologies covering the period from 2009 up until today. In this context, different useful analytical methods have been developed based mainly on typical techniques such as gas chromatography, liquid chromatography, mass spectrometry, electrophoresis, electroanalytical chemistry, and biosensors. The analytical features of these methods have allowed the analysis of samples of different natures, such as environmental, food, pharmaceutical, and biological type, in which wide classes of analytes are promptly determined. The main advantages of these methods are included and discussed in this review regarding novelty, rapidity, sensitivity, selectivity, and costs. It is concluded that the development of rapid methods is still a growing trend in analytical chemistry and that gas- and liquid-chromatography mainly coupled to different modes of mass spectrometry are the most common analytical techniques applied today. Regarding the matrices analyzed, most of the methods have been developed for food analysis, followed by biological and environmental matrices.     

The Effect of Temperature on GPC for the Separation of PCBs from Transformer Oil and Subsequent Analysis by GC-MSD

Abstract

The analysis of PCBs often involves lengthy and expensive cleanup procedures to remove interferences associated with environmental sample matrices. Gel permeation chromatography (GPC) has proven to be a useful tool in removing many of these interferences from environmental samples, especially from difficult matrices such as oils, lipids and sediments. This paper describes the effect of temperature upon the GPC column in separating PCBs from transformer oil and its implication on GC-MS analysis.