Search

This study demonstrated the utility of negative ion atmospheric pressure ionization mass spectrometry for the routine quantitation of 2,4,5-trichlorophenoxyacetic acid and its glycine and taurine amide metabolites in mouse blood, urine and feces samples. The quantitation of 2,4,5-trichlorophenoxyacetic acid in blood follows a short cleanup procedure and used 2,4,5-trichlorophenoxy-13C6-acetic acid as the stable label isotope diluent. A more extensive cleanup procedure utilizing high-pressure liquid chromatography was required for the determination of 2,4,5-trichlorophenoxyacetic acid and its two metabolites in urine and feces. The glycine amide metabolite was quantitated by the 13C stable isotope diluent method. The taurine amide relied on an initial separation step followed by using a second 2,4,5-trichlorophenoxy-13C6-acetic acid spike fot its isotope diluent. Alkaline hydrolysis of the metabolites, followed by methylation, allowed the methyl ester of 2,4,5-trichlorophenoxyacetic acid to be solely used as the analyte in the negative ion atmospheric pressure ionization mass spectrometry quantitation step.

The mechanism of naphthalene oxidation by the filamentous fungus, Cunninghamella elegans is described. C. elegans oxidized naphthalene predominately to trans-1,2-dihydroxy-1,2-dihydroxy-1,2-dihydronaphthalene. A trans configuration was assigned for the dihydrodiol by nuclear magnetic resonance (NMR) spectroscopy at 500 MHz which showed a large coupling constant (J1,2) of 11.0 Hz. Comparison of the circular dichroism spectrum of the fungal trans-1,2-dihydroxy-1,2-dihydronaphthalene to that formed by mammalian enzyme systems indicated that the fungal dihydrodiol contained 76% (+)-(1S,2S)-dihydrodiol as the predominant enantiomer. Other naphthalene metabolites formed by C. elegans were identified as 1-naphthol, 2-naphthol and 4-hydroxy-1-tetralone. Incubation of C. elegans with naphthalene and 18O2 indicated that the trans-1,2-dihydroxy-1,2-dihydronaphthalene contained one atom of molecular oxygen which indicated a monooxygenase catalyzed reaction while similar incubations with naphthalene and H182O indicated that the other oxygen atom in trans-1,2-dihydroxy-1,2-dihydronaphthalene was derived from water. Mass spectral analysis of the acid-catalyzed dehydration products of the dihydrodiol indicated that the naphthalene dihydrodiol forms via the addition of water at the C-2 position of naphthalene-1,2-oxide. Fungal metabolism of [1-2H]naphthalene yielded 1-naphthol which retained 78% of the deuterium. NMR analysis of the deuterated 1-naphthol indicated an NIH shift mechanism in which deuterium migrated from the C-1 position to the C-2 position. The above results indicate that naphthalene-1,2-oxide is an intermediate in the fungal metabolism of naphthalene and that the fungal enzymes are highly stereo-selective in the formation of trans-1,2-dihydroxy-1,2-dihydronaphthalene.

An analytical method for the quantitation of nanogram to subnanogram amounts of dexamethasone is described. Dexamethasone was isolated from human plasma using a C18-bonded reverse-phase cartridge, purified by subsequent normal-phase HPLC, and the corresponding trimethylsilyl derivative analyzed by gas chromatography-mass spectrometry (GC-MS). The quantitation by isotope-dilution MS was carried out by selected-ion monitoring on the (M + 1)+ ion of the trimethylsilyl derivative of dexamethasone and its stable isotopically labeled diluent, [ 13C6 ,2H3]dexamethasone (681 and 690 m/z, respectively). Methane was used as the GC carrier gas and as the chemical-ionization reagent gas. The sensitivity of the method, judged from the lower limit of detection of the mass spectrometer, was at approximately 100 pg. The inter- and intraassay coefficients of variation (CV) determined at two different concentrations were 3.83 and 3.78% for 2 ng/mL and 2.64 and 1.29% for 5 ng/mL, respectively. Plasma concentration profiles for dexamethasone following a single 1-mg iv and a 2-mg oral dose of dexamethasone administered 24 h apart to two healthy volunteers are presented. The mass fragmentographic method described here is useful for bioavailability and pharmacokinetic studies of the synthetic glucocorticoid.

Trimellitic anhydride has widespread usage in a variety of industrial processes. Inhalation of the airborne dust and fumes generated by these processes is the primary route of occupational exposure leading to a variety of respiratory maladies. Because of its extensive industrial usage and limited toxicological data, trimellitic anhydride was scheduled for toxicological evaluation. Analytical purity certification and chemical characterization of the chemical were required as prerequisites for such toxicological tests. Therefore, a sensitive and specific procedure for the analysis of trimellitic anhydride and its trimellitic acid impurity in admixture was developed. After methylation with diazomethane, the compounds were assayed by gas chromatography using flame ionization detection. Chromatography on 5% SP-2100 yielded two well separated peaks, which were used for quantitation of the parent compounds. Confirmational identity of trimellitic anhydride was determined by direct insertion probe mass spectrometry, while that of the anhydride methyl derivative and trimellitic acid trimethyl derivative was determined by gas chromatography-mass spectrometry.

In toxicological research with hazardous substances (e.g. carcinogens), wastewater effluent from the test facility must be free of such substances before discharge into the environment. An industrial wastewater processing employing adsorbers of carbon and XAD-2 resin is described; however, chemical assays of each batch of treated effluent must certify the absence of all test agents. Elution profiles and adsorption isotherm tests with the test agents vs. the two adsorbents provided the basis for a "marker" technique which should eliminate the necessity to assay for all test agents in each batch of processed effluent. A radionale is presented for periodic introduction of a "marker" (gentian violet) into the primary adsorbers. If detected in the effluent, the "marker", which elutes from the adsorbers before most of the test agents would signal impending depletion of the adsorbent which could then be replaced. Recommendations to modify the industrial wastewater treatment plant and to implement the "marker" technique are presented as cost-effective alternatives to extensive and laborious chemical assays.

Tripelennamine hydrochloride, thenyldiamine hydrochloride, and chlorothen citrate have been used as antihistamines and for the treatment of asthma and bronchitis. Toxicological evaluation of these drugs was scheduled as part of a structure-activity relationship study of antihistamines in rats and mice, because of the paucity of such information. Prerequisite for the evaluation was the development of analytical chemical procedures to certify the concentration, homogeneity, and stability of the drugs in dosed feed, to monitor the urine of laboratory personnel to signal their possible exposure to the drugs, and to monitor the wastewater to ensure that the test agents were not discharged into the environment. A high-pressure liquid chromatographic procedure with fluorescence detection was developed for determination of the three antihistamines in admixture in animal feed, human urine, and wastewater at levels of 500, 10 and 10 ng g , respectively. Data on the partition values and use of a silica gel column to aid in the clean-up of sample extracts from the three substrates are reported for the three test agents. Extraction efficiencies and data concerning the stability of tripelennamine hydrochloride and thenyldiamine hydrochloride in animal feed are presented. Description of a new route for synthesis of chlorothen citrate and ancillary data concerning the gas chromatographic analysis for the three drugs in admixture in animal feed at levels as low as 10 mug g are also reported.

Specific, precise and sensitive methods are described for determining traces of potentially carcinogenic metabolites of Direct Red 2 and Direct Blue 15 in rat and hamster urine and to monitor the urine from workers who may be occupationally exposed to these dyes. This methodology is generally applicable to metabolites of azo dyes based on benzidine or three of its congeners. The benzidine-congener free amines, their mono and diacetylated analogs and alkaline hydrolyzable conjugates were determined after appropriate extraction and hydrolysis by HPLC or EC/GC. Residues of metabolites in rat, hamster, and human urine were determined at levels as low as 1 ppb. Supplementary information is also presented concerning hydrolysis of diacetylated metabolites and the stability of Direct Red 2 and Direct Blue 15 in rat, hamster and human urine.