Software-based mass spectral enhancement to remove interferences from spectra of unknowns.

Gas chromatography-mass spectrometry data from the analysis of complex environmental samples were converted into ASCII text and imported into a personal computer spreadsheet. A macro was written to perform mass spectral enhancement by statistical and mathematical procedures to separate the spectra of compounds of interest from interfering mass spectral responses, such as those of broadly eluting hydrocarbons. The extracted mass spectra were compared to reference spectra, with the result that usually 80-90% of the ions common to those in the reference spectra were successfully extracted by using this method. This procedure improved mass spectral quality and the ability of the data system to perform successful library searches. The fitted quality parameters showed systematic improvements after the data were subjected to the spectral enhancement procedures. These procedures could help to identify unknowns by separating their spectra from other signals, such as those of background aliphatic hydrocarbons.

Perinatal toxicity of endrin in rodents. I. Fetotoxic effects of prenatal exposure in hamsters.

The potential of the insecticide endrin to induce fetal toxicity was determined in hamsters exposed to the compound on either day 8 or days 5--14 of gestation. Endrin was administered by oral gavage as a solution in corn oil. Doses used included 0.5--10.0 mg/kg on day 8 and 0.75 to 3.5 mg/kg/day on days 5--14. Exposure to a single dose of endrin resulted in significant incidences of fused ribs and meningoencephaloceles at levels of 5 mg/kg or greater. No significant effects were noted in either maternal mortality and weight gain or in fetal mortality or weight gain. The administration of multiple doses of endrin resulted in few fetal defects, although a significant dose-related increase in fetal mortality and decrease in fetal weight was seen. Significant maternal lethality and weight reductions were noted at doses of 1.5 mg/kg/day or greater. At sacrifice, maternal liver and fetal tissues were collected and subsequently analyzed for endrin and a major metabolite, 12-ketoendrin. Endrin was found to cross the placenta and 20 ppb were found in fetuses from litters exposed to 2.5 mg/kg/day. Maternal livers from this dose group contained an average of 2500 pbb of endrin.

Formation of nitro musk adducts of rainbow trout hemoglobin for potential use as biomarkers of exposure.

The high use of nitro musk xylene (MX) and musk ketone (MK) as fragrances, and their persistence and bioaccumulation potential make them ubiquitous environmental contaminants. The 4-amino-MX (AMX) and 2-amino-MK (AMK) metabolites have been detected in trout fish hemoglobin (Hb) samples by gas chromatography-ion trap-mass spectrometry (GC-MS). Twelve Hb samples prepared from rainbow trout that were exposed to MX and MK, over a period of 24 and 72 h, were analyzed. Amino metabolites were liberated by basic hydrolysis and extracted from the fish Hb into n-hexane. The extract was concentrated, analyzed, and spiked with a standard solution (80 pg/microl) of AMX or AMK and reanalyzed. Concentrations of AMX from 10 to 25 ng/g were detected in Hb from fish taken 24 and 72 h after MX exposure. At 24 and 72 h after MK exposure, the concentration of AMK was found to be 25-51 ng/g and 9.5-25 ng/g, respectively. Concentrations of AMK in Hb from two of the three trout were substantially lower after 72 h compared with 24 h exposure. The AMX and AMK metabolites were not detected in four control samples. Average recoveries exceeding 89 and 86% could be achieved for AMX and AMK, respectively, with a coefficient of variation (CV) around 5%.

Identification of polybrominated biphenyls in the adipose tissues of the general population of the United States.

Hexabromobiphenyl has been identified by gas chromatography/mass spectrometry (GC/MS) in pooled extracts of adipose tissue samples collected from the general population of the conterminous United States. Mass spectra derived from tissue extracts subjected to gel permeation chromatography were compared with those obtained from an authentic PBB mixture containing 2,4,5,2',4',5'-hexabromobiphenyl as the principal component. GC retention times and unique characteristics of the mass spectrum permitted confirmation of identity of the hexabromo isomer. Levels in one tissue sample were determined to be in the 1 to 2 ppb range.

Determination of a bound musk xylene metabolite in carp hemoglobin as a biomarker of exposure by gas chromatography-mass spectrometry using selected ion monitoring.

Musk xylene (MX) is widely used as a fragrance ingredient in commercial toiletries. Identification and quantitation of a bound 4-amino-MX (AMX) metabolite was carried out by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). Detection of AMX occurred after the cysteine adducts in carp hemoglobin (Hb), derived from the nitroso metabolite, were released by alkaline hydrolysis. The released AMX metabolite was extracted into n-hexane. The extract was preconcentrated by evaporation and analyzed by GC-SIM-MS. The concentration of AMX metabolite was found to range from 6.0 to 30.6 ng/g in the carp Hb, collected from the Las Vegas Wash and Lake Mead, NV areas. The presence of an AMX metabolite in the carp Hb was confirmed when similar mass spectral features and the same retention time of the AMX metabolite were obtained for both standard AMX and carp Hb extract solutions. In the nonhydrolyzed and reagent blank extracts, the AMX metabolite was not detected.

Chemical analysis of human blood for assessment of environmental exposure to semivolatile organochlorine chemical contaminants.

A chemical method for the quantitative analysis of organochlorine pesticide residues present in human blood was scaled-up to provide increased sensitivity and extended to include organochlorine industrial chemicals. Whole blood samples were extracted with hexane, concentrated, and analyzed without further cleanup by gas chromatography with electron capture detection. The methodology used was validated by conducting recovery studies at 1 and 10 ng/g (ppb) levels. Screening and confirmational analyses were performed by gas chromatography/mass spectrometry on samples collected from potentially exposed residents of the Love Canal area of Niagara Falls, New York and from volunteers in the Research Triangle Park area of North Carolina for 25 specific semivolatile organochlorine contaminants including chlorobenzene and chlorotoluene congeners, hexachloro-1,3-butadiene, pesticides, and polychlorinated biphenyls as Aroclor 1260. Dichlorobenzene, hexachlorobenzene, and beta-hexachlorocyclohexane residues fell in the range of 0.1 to 26 ppb in a high percentage of both the field and volunteer blood samples analyzed. Levels of other organochlorine compounds were either non-detectable or present in sub-ppb ranges.

The recognition of diazinon, an organophosphorus pesticide, when found in samples in the form of decomposition products.

The contents of a bottle, from which a human being was reported to have drunk and which were believed responsible to an organophosphorus poisoning, were submitted for chemical analysis. Initial screening by gas chromatography with phosphorus, sulfur, and nitrogen specific detectors failed to identify any intact organophosphorus pesticide. Mass spectrometric techniques were applied to the identification. Field ionization, field desorption, chemical ionization, exact mass measurements at high resolution, and GC/low resolution mass spectrometry were used to help define the qualitative and partial quantitative nature of the sample components. Results of this study were consistent with the virtually complete conversion of the pesticide, diazinon [Chemical Abstracts reference number 333-41-5], into a mixture of at least twenty-six chemically distinct products or impurities. The most abundant chemical compounds found in the sample included: 2-isopropyl-4-methyl-6-hydroxypyrimidine [2814-20-2]; 2-isopropyl-4-methyl-6-mercaptopyrimidine; 6,6'-dithiobis-(2-isopropyl-4-methylpyrimidine); 6,6'-dithiobis-(2-isopropyl-4-methylpyrimidine); 4-ethoxy-2-isopropyl-6-methylpyrimidine [72799-31-6]; 4-thioethoxy-2-isopropyl-6-methylpyrimidine; triethylphosphorothiolate and triethylphosphorothiolate. Also found were several potent acetylcholinesterase inhibitors: monothionotetraethylpyrophosphate; dithionotetraethylpyrophosphate [3689-24-5]; tetraethylpyrophosphate. Model decomposition studies verified the formation of these compounds. These results were then used to identify compounds in two other samples.

Two acute human poisoning cases resulting from exposure to diazinon transformation products in Egypt.

Two spraymen working in public health occupations in Alexandria, Egypt, experienced acute toxicity resulting from exposure to diazinon. Symptomatology was similar to that previously reported for exposure to parathion or other organophosphorus insecticides. Plasma and red blood cell cholinesterase activity values were determined in blood samples obtained from both individuals at various times after the incident. Cholinesterase activity showed a marked reduction up to 18 days after exposure. Blood cholinesterase activity recovered to approximately 90% of the normal level of activity 28 days after the poisoning incident in one individual. This activity recovered to about the same level in the other individual, but after only 20 days from the poisoning date. Experimental results suggested that this acute toxicity resulted from unsuitable storage conditions of the emulsifiable concentrate formulation of diazinon. The diazinon that was applied was stored in "tin" containers made of tin-plated sheet steel. The emulsifiable concentrate (60%) was not in compliance with the World Health Organization's standard specifications regarding the emulsion stability tests because of the presence of crystals in the emulsifiable concentrate. A sample of this crystalline material was analyzed. Gas chromatographic analysis combined with mass spectrometric techniques failed to identify intact diazinon in samples of that material. The sample represented virtually complete conversion of diazinion into transformation products. Sulfotepp and monothiono-TEPP were two of the identified products in the sample, both of which are much more toxic than diazinon.

Ion abundance criteria for gas chromatographic/mass spectrometric environmental analysis.

Mass and intensity calibration of gas chromatograph/mass spectrometer (GC/MS) responses is an important quality assurance issue for chemical analysis. Ion abundance calibration with decafluorotriphenylphosphine (DFTPP) was applied in 1975 to standardize quadrupole spectra to resemble the ion abundances that were obtainable from magnetic sector mass spectrometers. Modern quadrupole mass spectrometers provide significantly greater high-mass sensitivity than allowed under the 1975 study. Thus, those recommendations were reevaluated with 2 approaches. First, an interlaboratory study was conducted using 15 different gas chromatography/mass spectrometry (GC/MS) systems. Second, the U.S. Environmental Protection Agency Contract Laboratory Program (EPA-CLP) quality assurance data base was searched and over 6500 DFTPP tune results were plotted and evaluated. Based on these approaches, updated ion abundance criteria recommendations have been developed, which contemporary instruments can meet, and which meet data quality objectives regarding identification and quantitative analysis of analytes.

Use of the 'ortho effect' for chlorinated biphenyl and brominated biphenyl isomer identification.

The 'ortho effect', observed for chlorinated biphenyls (PCBs) and brominated biphenyls (PBBs) having the 2,2', 2,2',6 or 2,2',6,6' halogens, can be combined with GC retention index for isomer specific identifications by gas chromatography/mass spectrometry (GC/MS). This technique reliably allows accurate structure assignments for environmental monitoring without the use of multiple GC determinations that employ different chromatographic phases. Validation of the ortho effect for 129 PCBs and PBBs is reported, including a survey of all PCB mass spectra in the EPA/NIH mass spectral database. Presence or absence of ortho effect and reduction in magnitude for 2,2', 6,6' substitution may be related to the formation of a planar, bridged halonium ion intermediate upon electron ionization in the mass spectrometer.

Fungal transformations of triparanol.

Fungal transformations of triparanol, a hypercholesterolemic drug, were studied in Lagenidium giganteum and Lagenidium callinectes. The products were identified by combined gas chromatography-mass spectrometry. Two metabolites were observed from each organism; only one of the metabolites was found in both organisms.

Capillary electrophoresis and capillary electrochromatography of organic pollutants.

Capillary electrophoresis (CE) has a unique capability for separation of analytes of environmental concern, particularly those that are more polar and ionic, based on the complementary separation principle of electrophoresis. In the past few years, CE has been selectively used to analyze various classes of compounds having current or potential environmental relevance. This review outlines the current status of CE for the determination of environmental pollutants, based predominantly on research results published from the beginning of 1997 to early 1999. Covered are environmental pollutants of all types except pesticides and inorganics. Certain naturally produced toxins are also covered because of their significant impacts upon human health and the environment. CE methods, as with all methods, must be judged on their ability to provide approaches that are reliable, sensitive, selective, and rapid, while meeting "green chemistry" initiatives for pollution prevention. We also compare CE methods to benchmark environmental techniques involving gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), and high performance liquid chromatography (HPLC).

Correlation of structure with retention index for chlorinated dibenzo-p-dioxins.

The method presented here allows calculation of the retention indices for the chlorinated dibenzo-p-dioxins under a specific set of experimental conditions, using a limited data set. This technique provides a simple way to obtain retention index data for those isomer standards not readily available. Thus, the technique can aid in structure assignment of specific congeners whether obtained from synthesis or found in environmental monitoring efforts. These calculations have proved highly successful in checking gas chromatographic retention data for internal consistency.

Determination of elemental compositions from mass peak profiles of the molecular ion (m) and the m + 1 and m + 2 ions.

The relative abundances of M + 1 and M + 2 ions help to identify the elemental composition of the molecular ion (M). But scan speed, sensitivity, and resolution limitations of mass spectrometers have impeded determination of these abundances. Mass peak profiling from selected ion recording data (MPPSIRD) provided faster sampling and enhanced sensitivity, which permitted use of higher resolution. M + 2 profiles having only a few percent of the ion abundance of M were monitored at 20 000 resolution. The relative abundances, exact masses, and shapes of M, M + 1, and M + 2 mass peak profiles were determined. By applying five criteria based on these quantities, elemental compositions were determined even for ions too large (up to 766 Da) to be uniquely assigned from their exact mass and accuracy limits alone. A profile generation model (PGM) was written to predict these resolution-dependent quantities by considering all M + 1 and M + 2 ions for each candidate composition. The model also provided assurance that no other compositions were possible. Characterization of the M + 1 and M + 2 profiles by MPPSIRD and the PGM greatly expanded the practical ability of high-resolution mass spectrometry to determine elemental compositions.

Cycloartenol-derived sterol biosynthesis in the Peronosporales.

Selected species of the order Peronosporales, which are unable to epoxidize squalene and thus synthesize sterols, are able to metabolize exogenous cycloartenol to lanosterol and in some organisms to fucosterol, ergosterol, and cholesterol. Lanosterol was less effectively utilized but some ergosterol and cholesterol were yielded. Fucosterol was very efficiently metabolized by most species to ergosterol, Delta(7)-ergostenol, Delta(5)-ergostenol, cholestanol, and cholesterol. Several unknown sterols were observed in most trials. These data suggest a vestigial sterol synthetic pathway derived from cycloartenol, followed by possible isomerization to lanosterol and then to other sterols.

PCB metabolism in rats following prolonged exposure to Aroclor 1242 and aroclor 1016.

Several mono- and dihydroxy metabolites of di-, tri, and tetrachlorobiphenyl have been identified in the urine of rats fed prolonged diets of Aroclor 1016 or Aroclor 1242. Combined gas chromatography-mass spectrometry was used for characterization of the metabolic products.

Field disposal of methyl parathion using acidified powdered zinc.

The degradation of methyl parathion in soil with various amounts of acidified powdered zinc under field conditions was studied. Treatment was progressively more effective with increasing amounts of zinc. Disappearance of parent compound was followed for 2 1/2 years. The expected conversion product aminomethyl parathion and its N-methyl derivative were formed. In addition, N,N-dimethylamino, and the azo and azoxy condensation products were characterized by high resolution mass spectrometry. Aminomethyl parathion was shown to be identical to an authentic standard. The other specific positional isomers were considered likely, but were not proven by mass spectrometry. Structure elucidation was made with high resolution mass spectrometry, using the direct insertion probe, and with gas chromatography/low resolution mass spectrometry.