Simultaneous determination of monofluoroacetate, difluoroacetate and trifluoroacetate in environmental samples by ion chromatography

Direct aqueous injection of the fluoroacetate anion in potable water for analysis by liquid chromatography tandem mass-spectrometry

Sodium fluoroacetate or Compound 1080 is a rodenticide registered in the United States for use in livestock protection collars. The collars are employed to control predation on herd animals (i.e., killing of cattle by wolves or coyotes). Sodium fluoroacetate is acutely toxic to humans and has potential to cause mass casualties if used to intentionally contaminate water systems. The U.S. Environmental Protection Agency (EPA) is responsible for characterization and remediation if such an incident occurs in the civilian sector. In support of that goal, EPA has published the Selected Analytical Methods for Remediation and Recovery (SAM) document that provides sampling and analysis methods for many hazardous chemicals such as sodium fluoroacetate. Ideal SAM methods require limited sample preparation steps and utilize widely available equipment to ensure the ability for maximum laboratory participation in a large-scale response. The present paper describes a direct aqueous injection (DAI) method for liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis of the fluoroacetate anion (FAA) in potable water. Sample preservation and filtration are the only pre-processing steps required. FAA is chromatographically separated on an octylsilane (C8) reversed phase column. Separation is attributed to ion-exchange interactions. Electrospray ionization (ESI) in negative mode and detection by tandem mass spectrometry follow. FAA presence was confirmed by two fragment ions in the correct ratio, and use of a labeled standard allowed for quantitation by isotope dilution. FAA detection and quantitation limits were 0.4 μg/L and 2 μg/L, respectively. Four different drinking water utilities provided water samples from varying locations across the U.S. All the water samples were fortified with FAA and tested to evaluate analyte stability and the robustness of the method.

Application of a fluorescent derivatization reagent 9-chloromethyl anthracene on determination of carboxylic acids by HPLC

A simple and sensitive high-performance liquid chromatography (HPLC) method is proposed for the analysis of some carboxylic acids in food samples and the environment. The use of 9-chloromethyl anthracene as a fluorescence-labeling reagent has been investigated. The derivatization reagent reacts with unitary carboxylic acids and tetrabutylammonium bromide as a catalyst within 50 min in acetonitrile to give esters, which can be separated by HPLC employing fluorescence detection at λ(ex) = 365 and λ(em) = 410 nm. The optimum conditions for derivatization, fluorescence detection and chromatographic separation are established. The method shows good sensitivity, with a detection limit from 0.18 to 2.53 pmol, and good linearity between 1-250 nmol/mL of each analyte. The practical applicability of the method was demonstrated by analyzing samples that were spiked with the acid standards, environment and food samples.

The fate of the chemical warfare agent during DNA extraction

Forensic laboratories do not have the infrastructure to process or store contaminated DNA samples that have been recovered from a crime scene contaminated with chemical or biological warfare agents. Previous research has shown that DNA profiles can be recovered from blood exposed to several chemical warfare agents after the agent has been removed. The fate of four toxic agents, sulfur mustard, sodium 2-fluoroacetate, sarin, and diazinon, in a lysis buffer used in Promega DNA IQ extraction protocol was studied to determine if extraction would render the samples safe. Two independent analytical methods were used per agent, selected from GC-MS, 1H NMR, 19F NMR, (31)P NMR, or LC-ES MS. The methods were validated before use. Determinations were carried out in a semi-quantitative way, by direct comparison to standards. Agent levels in the elution buffer were found to be below the detectable limits for mustard, sarin, sodium 2-fluoroacetate or low (<0.02 mg/mL) for diazinon. Therefore, once extracted these DNA samples could be safely processed in a forensic laboratory.

Contactless conductivity detection of sodium monofluoroacetate in fruit juices on a CE microchip

Rapid and quantitative determination of sodium monofluoroacetate in diluted fruit juices (dilution 1:9 v/v in deionized water) and tap water was performed by microchip CE, using contactless conductivity detection. A separation buffer consisting of 20 mM citric acid and histidine at pH 3.5 enabled the detection of the monofluoroacetate (MFA) anion in diluted apple juice, cranberry juice, and orange juice without lengthy sample pretreatments. The analyte was very well separated from interfering anionic species present in juices and tap water. LODs in diluted juices and tap water were determined to be 125, 167, 138, and 173 microg/L for tap water, apple juice, cranberry juice, and orange juice, respectively, based upon an S/N of 3:1. Taking into account the dilution factor, the LODs for juice samples range from 1 to 2 mg/L, which is adequate for monitoring the toxicity of MFA in these juice beverages and tap water. The calibration curves for MFA in diluted fruit juices were linear over the range of 500 microg/L to 80 mg/L. The total analysis time for detecting the MFA anion in fruit juices was less than 5 min, which represents a considerable reduction in analysis time compared to other analytical methods currently used in food analysis.

Separation mechanism and determination of flavanones with capillary electrophoresis and high-performance liquid chromatography

To probe separation mechanism and determination with capillary zone electrophoresis (CZE) and liquid chromatography (LC), nine compounds with identical flavanone skeleton were studied. Optimum separation of LC was attained with gradient of acetonitrile and 5mM phosphate buffer (pH 6.9). For CE, electrolyte buffer was 4.5mM SDS in 32mM sodium tetraborate buffer (pH 9.2). The distinguishing feature in this work was successful separation of monohydroxyl stereoisomers by CZE. Polarity is generally increased with hydroxyl groups. In a separation mechanism study, polarity would be reduced by intramolecular hydrogen bond between hydroxyl of C5 and carbonyl group of C4. Comparison of the retention results among monohydroxyl flavanones shows polarity with hydroxyl at C6 the least, and that at C4' and C7 nearly equal. Also, elution order of flavones and flavanones would be adverse due to the hydroxyl at C3 in LC. From the numerical value pK(a) of flavanone, the C7-OH is the smallest, and two hydroxyl groups in an adjacent position is always less than the unique one caused by forming a stable 5-membered ring. Investigation of separation mechanism yield only the effect of constituent but also reasonable explanation for contradictory results between Wulf and our laboratory, this due to the hydroxyl at C3.

Rapid quantitative and qualitative confirmatory method for the determination of monofluoroacetic acid in foods by liquid chromatography–mass spectrometry

A rapid quantitative method and a qualitative confirmatory method for the determination of monofluoroacetic acid (MFA) in complex food matrices are presented. The quantitative method utilizes a water extraction, solid phase extraction clean-up and liquid chromatography-mass spectrometry (LC-MS) for determination of MFA. This method showed a high degree of specificity, detecting MFA in all of the spiked samples, while none of the unfortified samples tested positive for MFA. Spike recoveries were high in all matrices analyzed, varying from 85 to 110%, and comparable at low (2mg/L) and high (20mg/L) spiking levels. Repeatability tests at the low spiking levels yielded RSDs of less than 5% for all matrices analyzed. The qualitative confirmatory method developed is conceptually different from the quantitative method, ensuring that both methods would not be subject to the same interferences. The method uses the formation of the hydrazide of MFA through derivatization with 2-nitrophenylhydrazine. This derivatization is well established for the determination of carboxylic acids, but this is the first application to the determination of MFA. The derivatization yield was matrix dependent, however the limit of detection (LOD) (0.8microg/L) was sufficient to confirm the presence of MFA in all spiked matrices. Repeatability tests at the low spiking levels yielded RSDs of approximately 7% for all matrices analyzed.

Determination of trace levels of total fluorine in water using combustion ion chromatography for fluorine: a mass balance approach to determine individual perfluorinated chemicals in water

Perfluorinated compounds (PFCs) such as perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have received worldwide attention because of their environmental persistence and widespread distribution. Because of the lack of robust analytical methods and standards to detect all of the PFCs, and their precursors and metabolic intermediates, a mass balance approach involving the determination of total fluorine (TF), followed by fractionation of samples to separately determine inorganic and organic fluorine, is needed. In this study, we have developed a method to determine low microg/L levels of total fluorine (TF) in seawater samples. Further, seawater samples were fractionated into organic and inorganic fractions by extraction with organic solvents, which were then analyzed for TF, extractable organic fluorine (EOF) and inorganic fluorine (IF; i.e., fluoride). Concentrations of known perfluorinated compounds (PFCs) including PFOS and PFOA were also determined in water samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to enable calculation of the fraction of fluorine that is contributed by PFCs to TF. A major proportion of fluorine in seawater was in the form of fluoride (>90% in locations not affected by direct discharges). Nevertheless, within the organofluorine fraction, a major percentage (60-90%) of fluorine still remains unknown in water samples, suggesting the occurrence of other fluorinated acids in addition to known perfluorinated acids. Further studies are needed to identify and quantify the unidentified organofluorines in seawater. Mass balance analysis of total organic fluorine (TOF) and EOF is important, if we are to understand transport and fate of fluorinated compounds in the environment, and if we are to identify the sources of unidentified fluorinated compounds.