In 2007, it was determined that melamine, ammeline, ammelide, and cyanuric acid (abbreviated as MARC for melamine and related contaminants) had been added to wheat gluten and rice protein that were subsequently incorporated into pet food. The consumption of food tainted by MARC compounds was implicated in numerous instances of renal failure in cats and dogs. A method for the analysis of MARC compounds in kidney tissue using high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) has been developed. MARC analytes were extracted by homogenization of kidney tissue in 50/40/10 acetonitrile/water/diethylamine. The homogenate was centrifuged, and an aliquot of supernatant was diluted with acetonitrile, concentrated, and fortified with a stable isotope-labeled analogue of melamine. Analytes were detected using atmospheric pressure chemical ionization and multiple reaction monitoring. Quantitation of positive samples was performed using the internal standard method and five-point calibration curves ranging between 50 and 1000 ng/mL of each analyte. The method was validated by analysis of replicate kidney tissue samples fortified with the individual analytes and by analysis of kidney samples fortified with melamine cyanurate powder at two different concentrations. This method was successfully used for routine postmortem diagnosis of melamine toxicosis in animals. Melamine was also detected by this method in paraffin-embedded tissue from animals suspected to have died of melamine toxicosis.

This study examines the processes of dilution, degradation, and sorption to plant foliage of organophosphate (OP) pesticides during the summertime in an air corridor originating in the southern Central Valley of California and moving into the nearby Sierra Nevada mountains. Residues of chlorpyrifos, methidathion, and their oxons were examined in air and pine needles at three sites in the southern Sierra to delineate the role these processes play in the atmospheric fate of these residues. At the site closest to the Central Valley, we found relatively high levels of parent OPs and oxons in needle and air samples. At higher elevations needles contained lesser amounts of OP residues and at lower frequency, while air primarily contained the oxon form. With increasing elevation the ratio of thion to oxon form of chlorpyrifos in air decreased from 1.85 to 0.46 indicating that atmospheric oxidation was occuring. Based on the amounts of foliar deposition found, we estimate that during summer months nearly 16 kg of chlorpyrifos and its oxon may enter Sequoia National Park plant foliage. We deduce that for airborne OP insecticides, foliar deposition is a significant summertime fate process, along with atmospheric degradation and dilution.

A method combining QuEChERS extraction, ultra-high pressure liquid chromatography and full scan high resolution mass spectrometry was evaluated for its use in screening for chemical residues and contaminants in animal-related food matrices. The method was evaluated by analysis of multiple replicates of whole milk, muscle tissue, liver tissue and corn silage. Analytes tested included plant alkaloids, carbamate and organophosphate pesticides, and several types of veterinary drugs. A database containing the chemical formula for each analyte was used to calculate accurate mass-to-charge ratios for expected pseudo-molecular ions. This information, as well as retention times, was used to identify analytes. Of 118 compounds chosen for analysis, 86 were detectable in all fortified replicates of at least one matrix at levels ranging from 1.0 to 5000 ng/g. Variability of response, as measured in % relative standard deviation of peak areas over seven replicate fortified sample analyses, was found to differ among the classes of analytes, ranging from <10% to >100%. Retention times were stable and analytes were routinely detected at measured mass-to-charge ratios within 2 ppm of their theoretical mass-to-charge ratios. These results indicate that the combination of generic extraction and chromatographic procedures with full scan high resolution mass spectrometry can serve as a useful method for screening complex matrices.

Organophosphorus nerve agents are among the most toxic organic compounds known and continue to be a threat for both military and terrorist use. We have developed an isotope-dilution gas chromatography-tandem mass spectrometric (GC-MS-MS) method for quantitating the urinary metabolites of the organophosphorus nerve agents sarin (GB), soman (GD), VX, Russian VX (RVX), and cyclohexylsarin (GF). Urine samples were acidified, extracted into ether-acetonitrile, derivatized by methylation with diazomethane, and analyzed by GC-MS-MS. The limits of detection were less than 1 micro g/L for all analytes.