Chemical Ionization Mass Spectrometric Detection Research Articles

Identification of fenthion and temephos and their transformation products in water by high-performance liquid chromatography with diode array detection and atmospheric pressure chemical ionization mass spectrometric detection

Two organophosphorus pesticides, fenthion and temephos were oxidized with N-bromosuccinimide (NBS) in order to obtain the oxidated analogues which are the activated form of the pesticides. Analysis of the non-oxidized solution containing the pesticides, and two oxidized solutions which differed in the amount of NBS added was performed with both LC–diode array detection and NMR to confirm the presence of the degradation products. LC–atmospheric pressure chemical ionization-MS was used to unequivocally identify all the transformation products formed. With this technique it was possible to identify oxo derivatives, sulfoxides and isomers of both fenthion and temephos. Fenthion and its transformation products were characterized with both positive and negative mode of ionization whereas temephos was analyzed at an extraction voltage of 20 V to gain in sensitivity and at 40 V to enhance fragmentation. With both fenthion and temephos, the isomeric forms of these pesticides, the oxons and the sulfoxides eluted before the parental pesticide. It was observed that an increase of NBS produced fenthion sulfoxide oxon and temephos dioxon while the parental pesticides disappeared from these samples. In the case of temephos, the oxidation of this pesticide with NBS reproduce environmental conditions, since these same transformation products were also found in environmental waters that had been treated with temephos.

Determination of pyrrolizidine alkaloids in honey from selected sites by solid phase extraction and HPLC‐MS

A method was developed for the determination in honey of the Ragwort (Senecio jacobaea) derived pyrrolizidine alkaloids jacoline, jacozine, jacobine, seneciphylline and senecionine, combining solid‐phase extraction with high performance liquid chromatography and atmospheric pressure chemical ionization mass spectrometric detection. The method allowed determination of individual alkaloids and offered a considerable improvement in terms of speed, sensitivity and specificity over previous approaches, but was not suitable for determination of jaconine, a minor alkaloid in Ragwort. Instrument calibrations were linear over the range 0.005 to 10.0 μg/ml, equivalent to approximately 0.001 to 2.0 mg/kg in honey with the extraction method used and allowing for observed recoveries. Detection limits in honey were 0.002 mg/kg. Recoveries for most of the alkaloids were between 57 and 70%. The alkaloids have been determined in a number of samples of honey selected after pollen identification and counting. The alkaloids were not detectable in samples containing two grains or less of Ragwort pollen per gram of honey. Samples collected in late July and August contained Ragwort pollen at 15–21 grains/g and total alkaloid concentrations of 0.011–0.056 μg/ kg. Similar contributions to the total were made by jacozine, seneciophylline and senecionine, with jacobine making a larger and jacoline a smaller contribution. Two samples of honey containing Ragwort pollen at 24 and 16 grains/g had total alkaloid concentrations of 0.42 and 1.48 mg/kg respectively (not corrected for recovery). The alkaloid profile in these samples was dominated by seneciphylline and senecionine which together comprised 90–95% of the total. Alkaloids were not detected in retail honeys.

Rate constants for the reactions of CO3−(H2O)n=0–5 + SO2: Implications for CIMS detection of SO2

The rate constants for the CO3−(H2O)n + SO2 reactions were measured for n=0–5 using a variable temperature‐selected ion flow tube. Temperature dependences were measured for n=0–3 over the following temperature ranges: n=0, 158–550 K; n=1, 158–270 K; n=2, 158–193 K; n=3, 158–193 K. The n=4, 5 rate constants were measured exclusively at 158 K. Good agreement is found with previous measurements of the n=0 and 1 rate constants. Expressions are estimated for use in chemical ionization mass spectrometric detection of SO2 in the troposphere.

Rate Coefficients for the Reactions of Some C3 to C5 Hydrocarbon Peroxy Radicals with NO

The rate coefficients for the gas-phase reactions of allyl-, tert-butyl-, cyclopentyl-, and 2-pentylperoxy radicals with NO have been measured at 297 ± 2 K in a flow tube reactor using chemical ionization mass spectrometric (CIMS) detection of the peroxy radical. The hydrocarbon radicals were produced through the dissociation of the parent alkyl iodide in a low-power radio frequency (rf) discharge. The unimolecular decomposition of the c-pentyl radicals in the rf discharge yielded allyl radicals. The peroxy radicals were generated by reacting the hydrocarbon radicals with O2. The rate coefficients were found to be, in units of 10-12 cm3 molecule-1 s-1, 10.5 ± 1.8, 7.9 ± 1.3, 10.9 ± 1.9, and 8.0 ± 1.4 for the reactions of NO with CH2CHCH2O2, t-C4H9O2, c-C5H9O2, and 2-C5H11O2 radicals, respectively. The results of this study together with our previous results for nonsubstituted C1−C3 alkyl peroxy radicals suggest no significant trend in the rate coefficients with size and branching of the radicals. This is in contradiction to some previous studies, which found that the rate coefficients decrease with increasing radical size and complexity. Some implications of this finding for atmospheric chemistry are briefly discussed.

Extraction of maleic hydrazide residues from potato crisps and their determination using high-performance liquid chromatography with UV and atmospheric pressure chemical ionisation mass spectrometric detection

A method was required for the determination of maleic hydrazide residues in potato crisps. A published method for the extraction of the analyte from onions and potatoes was evaluated and found to be inappropriate due to the inability of the extracting solvent to penetrate the oily matrix. A method was developed to overcome this problem; the resulting recovery data (mean=92.9%. R.S.D.=8.3%, n=16) confirmed its efficiency, and was used to analyse 48 retail potato crisp samples. To confirm possible residues identified by screening with HPLC-UV, and HPLC-atmospheric pressure chemical ionization MS method was developed. There was good agreement between the data obtained from the detection techniques ( R 2=0.978, slope=1.11).

Analysis of Genetically Modified Canola Varieties by Atmospheric Pressure Chemical Ionization Mass Spectrometric and Flame Ionization Detection

Abstract Canola oil triacylglycerols from genetically modified canola lines were conclusively identified by reverse phase HPLC coupled with atmospheric pressure chemical ionization mass spectrometric (APCI-MS) detection. APCI-MS is a soft ionization technique, which gave simple spectra for triacylglycerols. Spectral identification of the triacylglycerols was based on the diacylglycerol fragments and on the protonated molecular ion [M+H]+, except trisaturates which gave no [M+H]+. Triacylglycerols were identified and quantitated in normal, high stearic acid and high lauric acid canola varieties by the RP-HPLC/APCI-MS technique. The LC/APCI-MS identification of canola oil triacylglycerols allowed their quantitation by reverse phase HPLC coupled with a commercial flame ionization detector (FID). There was agreement between fatty acid composition obtained by LC/APCI-MS and LC-FID. However, the triacylglycerol resolution obtained by LC/APCI-MS, was superior to LC-FID in the qualitative identification of triacy...

Direct Kinetics Study of the CH3C(O)O2+ NO Reaction Using Chemical Ionization Mass Spectrometry

A direct measurement of the CH3C(O)O2 + NO gas-phase reaction rate coefficient over the temperature range 200−402 K was made using chemical ionization mass spectrometric detection of the CH3C(O)O2 reactant. A significant temperature dependence was observed, and a temperature dependent expression of k(T) = (8.1 ± 1.3) × 10-12 exp{(270 ± 60)/T} cm3 molecule-1 s-1 was determined. The 298 K rate coefficient, k = (2.0 ± 0.3) × 10-11 cm3 molecule-1 s-1, agrees well with results from previous indirect measurements. NO2, CH3, and CO2 were positively identified as products originating from the reaction. The question of whether CH3 and CO2 are direct products of the reaction or result from the thermal decomposition of CH3C(O)O could not be answered. The 298 K rate coefficients for the reactions of SF6-, I-, and O3- with CH3C(O)O2 were measured to be ( ) × 10-10, ( ) × 10-10, and ≥2 × 10-10 cm3 molecule-1 s-1, respectively.

Temperature-dependent kinetics studies of the reactions of C2H5O2 andn-C3H7O2 radicals with NO

The rate coefficients for the gas-phase reactions of C2H5O2 and n-C3H7O2 radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O2, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C2H5 radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C3H7O2 + NO reaction, yielding k298 K = (9.1 ± 1.5) × 10−12 cm3 molecule−1 s−1, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10−12 exp{(380 ± 70)/T} cm3 molecule−1 s−1 and k(T) = (2.9 ± 0.5) × 10−12 exp{(350 ± 60)/T} cm3 molecule−1 s−1 for the reactions of C2H5O2 and n-C3H7O2 radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10−12 cm3 molecule−1 s−1 for C2H5O2 radicals and k = (9.4 ± 1.6) × 10−12 cm3 molecule−1 s−1 for n-C3H7O2 radicals. © 1996 John Wiley & Sons, Inc.

Reaction of Isopropyl Peroxy Radicals with NO over the Temperature Range 201−401 K

The rate constant for the gas-phase reaction of isopropyl peroxy radicals with NO has been measured over the temperature range of 201−401 K using chemical ionization mass spectrometric detection of the peroxy radical. The temperature dependent expression for the rate constant was found to be k(T) = (2.7 ± 0.5) × 10-12 exp{(360 ± 60)/T} cm3 molecule-1 s-1 which gives a rate constant of k = (9.0 ± 1.5) × 10-12 cm3 molecule-1 s-1 at 298 K. This value is a factor 1.8−2.6 higher than previous measurements.

Regioselective analysis of triacylglycerols by lipase hydrolysis

AbstractA modified procedure for the regiospecific analysis of triacylglycerols (TAG) with a 1,3‐specific lipase is described. After partial lipase hydrolysis of the triacylglycerol, the released free fatty acids (FFA) and 1,2(2,3)‐diacylglycerols (DAG) were isolated by thin‐layer chromatography (TLC) and converted to fatty acid methyl esters (FAME). The FAME were analyzed by gas‐liquid chromatography (GLC). The 1,3‐specific lipases used in this study included supported preparations from strains ofMucor miehei andRhizopus oryzae. The method also was applied to the regiospecific analyses of tung nut and Chinese melon seed oil triacyglycerols, both of which contain high proportions of α‐elaeostearic acid. The TAG composition of the oils was substantiated in parallel analysis of the oils by highperformance liquid chromatography with chemical ionization mass spectrometric detection of intact TAG.

Liquid chromatography chloride attachment negative chemical ionization mass spectrometry of diacylglycerol dinitrophenylurethanes

Chloride attachment and electron capture negative chemical ionization mass spectra were determined for the 3,5-dinitrophenyl urethanes of natural diacylglycerols following high-performance liquid chromatography on chiral-phase columns using dichloromethane as a source of chloride. For this purpose a chiral column containing the R(+) naphthylethylamine polymer was eluted with an isocratic mixture of either isooctane-f-butyl methyl ether-isopropanol-acetonitrile 80:10:5:5 (solvent A) containing 1% dichloromethane, or with solvent A (20%) and hexane-dichloromethane-ethanol 40:10:1 (solvent B, 80%). The dinitrophenylurethanes gave electron capture molecular and fragment ions in proportions which varied with the composition of the eluting solvent and the ion source pressure. The chloride attachment fragment ions corresponding to the intact diacylglycerols provided a sensitive method of identification and quantitation of the molecular species of the diacylglycerols under all conditions. The detection of the diacylglycerol dinitrophenylurethanes as the negative chloride attachment fragment ions increased the sensitivity and specificity of analysis of the solutes about 100-fold over positive chemical ionization mass spectrometric detection. The detection limit for the dinitrophenylurethanes of natural diacylglycerols was in the low-nanogram range, with the instrument response being linear over two orders of magnitude. For additional structural characterization the dinitrophenylurethanes were subjected to positive chemical ionization mass spectrometry, which resulted in prominent intensities for the [M - DNPU]+ and [RCO + 74]+ ions, but gave no molecular ions. Quantitative analysis of complex mixtures required calibration of the ionization response.

Identification and determination of propafenone and its principal metabolites in human urine using capillary gas chromatography/mass spectrometry

The capillary gas chromatography/mass spectrometry of trimethylsilyl-trifluoroacetyl, trifluoroacetyl and pentafluoropropionyl (PFP) derivatives of the antiarrhythmic agent propafenone (Rytmonorm), as well as its main metabolites N-despropyl-propafenone and 5-hydroxy-propafenone, have been investigated. Both electron impact and positive isobutane chemical ionization mass spectrometry using the Ion Trap Detector have been evaluated. The presence of propafenone and its co-extracted metabolites in human urine at time intervals after the oral administration of 150 mg Rytmonorm to healthy volunteers was established, and the urinary excretion of propafenone and 5-hydroxy-propafenone was calculated using selective chemical ionization mass spectrometric detection. Only a few per cent of the dose was excreted unchanged in the urine. Large intersubject variabilities had been observed also. The large dynamic range of the Ion Trap Detector and the high correlation coefficients (0.92-0.99) of the calibration curves were striking.

Determination of Organophosphorus Compounds in Mediterranean Coastal Waters and Biota Samples Using Gas Chromatography with Nitrogen-Phosphorus and Chemical Ionization Mass Spectrometric Detection

Abstract An analytical method is described for the determination of organophosphorus compounds in water and biota samples. This includes solvent extraction, a clean up procedure using silica gel and gel permeation chromatography with nitrogen-phosphorus and positive and negative chemical ionization mass spectrometric detection. Organophosphorus compounds were measured in river waters and biota samples (Mytilus galloprovincialis, Mullus barbatus and Gambusia affinis) from the Spanish Mediterranean coast. The results show that phosphates are only found in water samples affected by industrial activities, whereas organophosphorus pesticides, exhibiting higher bioconcentration factors, are found in biota samples.

Chemical ionization mass spectrometric detection in the gas chromatographic analysis of coal tars

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Ammonia and methane chemical ionization mass spectra of acid and carbamate pesticides using direct supercritical fluid injection

The ammonia and methane chemical ionization mass spectra of several carbamate and acid pesticides were obtained utilizing capillary supercritical fluid chromatography (SFC) for introduction. These compounds are generally not amenable to gas chromatography and the supercritical fluid method allows low-temperature separations (using carbon dioxide or nitrous oxide as mobile phases) with highly selective chemical ionization mass spectrometric detection for analysis. Ionization with ammonia produces primarily ammonium adduct ions, [M + 18]+, and protonated molecules, [M + 1]+, for all compounds. More energetic methane chemical ionization produces spectra containing fragment ions characteristic of the pesticide structure. All compounds were analysed under similar chromatographic conditions, with optimization for individual compounds minimized, and detection limits were in the picogram range. Analysis time for all compounds was under five minutes and no mobile phase interferences or thermal degradation was noted.

Occurrence of nitro-pah in the atmosphere in a rural area

By means of gas chromatography with nitrogen sensitive detection and negative ion chemical ionization mass spectrometric detection 7 mononitro-PAH, 9-nitroanthracene, x-nitro-4,5-methylene-phenanthrene, 3-nitrofluoranthene, 1- and 2-nitropyrene, 10-nitrobenz(a)anthracene and 6-nitrobenzo-(a)pyrene have been identied in samples of airborne particulate matter. Furthermore, 8-nitrofluoranthene has been tentatively identified. The amounts of mononitro-PAH are one to two orders of magnitude lower than the most common carcinogenic PAH, as e.g. benzo(a)pyrene. Filter effects have been studied, 9-nitroanthracene can be transformed during sampling at low atmospheric concentrations of NO 2 and photochemical oxidants to 9,10-dinitroanthracene and 10-nitroanthrone.

Microcapillary liquid chromatography in open tubular columns with diameters of 10–50 μm : Potential application to chemical ionization mass spectrometric detection

The theoretical separation efficiency of open microcapillary liquid chromatography (LC) columns, including peak-broadening effects resulting from interphase resistance to mass transfer, has been considered and an expression is derived for the plate height caused by interphase resistance.The use of such columns with internal diameters down to 10 μm is explored for LC separations. The columns were prepared from soft glass tubing and coated with polar and non-polar stationary phases. Several applications in straight phase as well as reversed-phase systems demonstrate the high separation speed (up to 50 effective plates per second). Relatively wide (30–50 μm) and short (1–5 m) columns allow rapid analyses within minutes. Smaller (10–30 μm) and longer (5–25 m) columns yield extremely high plate numbers (up to 5·106), permitting very difficult separations in a reasonable time (2–5 h). The required pressure never exceeds the generally accepted value of 400 bar. Preliminary results obtained with fused silica columns are discussed.Split-injection and addition of make-up mobile phase through the (UV) detector have been applied. In order to avoid undesirable dilution of the sample zones by the make-up liquid, the microcapillaries were directly coupled to a mass spectrometer (in the chemical ionization mode). This technique has yielded promising results.