Low Resolution Electron Impact Mass Research Articles

Biocatalytic degradation of selected tobacco chemicals from mainstream cigarette smoke using Croton megalocarpus seed husk biochar

BackgroundMainstream cigarette smoke contains a complex array of toxic chemicals which can cause irreparable harm to the lungs and most organs in the biological landscape. Attempts to reduce harmful by-products in mainstream cigarette smoke have received little attention although various researchers have proposed the use of catalysts, zeolites and filter modifications. In this study, the bio-degradation of selected tobacco chemicals in a commercial cigarette (MM-R) and a local cigarette (RR-M) is investigated.MethodologyCroton megalocarpus (C. megalocarpus) seed husk was ground into powder before pyrolysis at 550 °C to form biochar. The cigarette filter was treated with C. megalocarpus seed husk biochar as an adsorbent in order to degrade tobacco chemicals such as benzene and phenol. Specially designed smoking apparatus consistent with standard procedures for cigarette smoking was used to simulate cigarette smoking. Model tobacco chemicals—benzene and phenol—were characterized using low-resolution electron impact mass spectra on a liquid chromatograph hyphenated to a mass spectrometer. The overall concentration of tobacco chemicals with puff time was screened using a UV–visible spectrometer.ResultsThe rate constants for the removal of benzene from treated MM-R and RR-M cigarettes were 0.123,{mathrm{s}}^{-1} and 0.0759,{mathrm{s}}^{-1}, respectively, while the rate constants for the removal of phenol from the model cigarettes were 0.125,{mathrm{s}}^{-1} and 0.163,{mathrm{s}}^{-1}, respectively. For MM-R and RR-M cigarettes, the per cent reduction for benzene was 14.79 and 19.88 while that of phenol was 10.62 and 25.80, respectively. The reduction of benzene at 15,mathrm{s} puff time for MM-R cigarette was 55.91{%} while the reduction of phenol at the same puff time is 37.25{%}. Also, the reduction in the concentration of benzene and phenol for RR-M model cigarettes was 22.89{%} and 66.19{%}, respectively, at the same puff time. The UV–Vis data show overall reduction in tobacco chemicals with increase in residence time.ConclusionThe results reported in this study showed that C. megalocarpus seed husk biochar is a promising biocatalyst that can be incorporated into the cigarette filter in order to degrade tobacco chemicals in mainstream cigarette smoke. This is a very important finding towards harm reduction and tobacco reform policy.

Identification and characterization of a long-chain N-acyl homoserine lactone from Rhizobium sp. isolated from Zea x mays rhizosphere

The microbiological study of maize rhizosphere (Zea x mays) cultivated in Brazil led to the isolation of a bacterium, which was identified as Rhizobium sp. based upon 16 S rRNA analysis. The chemical study of fractions obtained from bacterium extract allowed the identification of the compound N-(3-oxo-tetradec-7-enoyl)-homoserine lactone (1) using uni and bidimensional nuclear magnetic resonance spectroscopy (NMR), gas chromatography coupled to low resolution electron impact mass spectrometry (GC–MS), and ultra-high resolution Qq-time-of-flight mass spectrometry (UHR-QqTOF-MS). Biological assays with the strains Agrobacterium tumefasciens A136 and Chromobacterium violaceum CV026 were also performed and showed negative results, corroborating the hypothesis of production of only the long chain acyl homoserine lactone (AHL) 1, and the lack of presence of short or medium chain homologues, as observed by instrumental GC–MS and NMR analyses. The chemotaxonomic relevance of the presence of long chain AHL in Rhizobiaceae was discussed.

Polybrominated diphenyl ether congeners in the young-of-the-year bluefish, Pomatomus saltatrix, from several nursery habitats along the US Atlantic coastline

Spatial trends of polybrominated diphenyl ether (PBDE) congeners were examined by using high resolution gas chromatography – low resolution electron impact mass spectrometry (GC-EIMS) in 414 samples of young-of-the-year (YOY) bluefish (Pomatomus saltatrix) collected from a total of 29 nursery habitats along the US Atlantic coastline from Massachusetts to Florida. Of the 26 target PBDE congeners, BDE-47 (4 Br), BDE-100 (5 Br), BDE-49 (4 Br), BDE-99 (5 Br), and BDE-154 (6 Br) were the five most frequently detected congeners in the order of decreasing importance. The sum of the concentrations of five major PBDE congeners, referred to as ΣPBDEs, varied between estuaries and also among samples from a given estuary. ΣPBDEs were lowest in YOY bluefish from Vineyard Sound, Nantucket Sound, Great Bay, Delaware Bay, Lynnhaven Bay, Cape Lookout, and Crescent Beach, with maximum ΣPBDE concentrations below 10ng/g wet weight. ΣPBDEs in three bluefish samples from Stamford Harbor were detected at relatively high to unusually high concentrations of 69.1, 205, and 561ng/g wet weight. ΣPBDE values for other Stamford Harbor bluefish were generally low. Highest PBDE concentrations were detected in the vicinity of industrial and urban locations within the New York – New Jersey metropolitan complex. Among them, bluefish from Newark Bay were generally the most contaminated with an average ΣPBDE value of 56.6±30.8ng/g wet weight. ΣPBDEs in bluefish from Newark Bay were numerically greater than ΣPBDEs in bluefish from all locations, however these differences were not statistically significant. Modest to good correlations between ΣPBDEs and lipids were observed for YOY bluefish from Buzzards Bay, Upper New Bedford Harbor, Lower New Bedford Harbor, Outer New Bedford Harbor, Providence Harbor, Housatonic River, Norwalk Harbor, Little Neck Bay, Newark Bay, Sandy Hook Bay, Great Bay, Delaware Bay, Patuxent River and Crescent Beach. Poor correlations between ΣPBDE and lipids were observed for bluefish from other estuaries. ΣPBDEs were not always correlated with fish length or weight. ΣPBDEs in YOY bluefish along the US Atlantic coastline modestly paralleled ΣPBDEs in mussels and oysters, from not exact but geographically loosely similar locations, reported in the NOAA Mussel Watch Program. A number of researchers who used the high resolution mass spectrometry reported additional PBDE congeners. Although PBDE congeners we report do appear to be the prominent congeners in these studies, it is likely that the comparisons will be skewed in certain instances.

Matching Structures to Mass Spectra Using Fragmentation Patterns: Are the Results As Good As They Look?

Three programs were assessed for their ability to predict mass spectral fragmentation patterns for all constitutional isomers of an experimental low-resolution electron impact mass spectrum (EI-MS), given the molecular formula, and use this information to identify the "correct structure". MOLGEN 3.5 was used to generate the structures, while all spectra were extracted from the NIST database. The commercial programs Mass Frontier and ACD MS Manager, as well as MOLGEN-MSF (developed by the University of Bayreuth) were used to generate mass spectral fragments. MOLGEN-MSF was used to generate "match values" to compare the different programs and their ability to identify the "correct structure". Although high match values could be achieved with certain settings, the ranking of the correct structure relative to other constitutional isomers was not significantly better than the results published previously and in some cases significantly worse. Furthermore, all programs showed bias toward specific structures, which changed significantly with minor changes to the program settings. Thus, advances in mass spectral fragment prediction have not necessarily improved computer aided structure elucidation (CASE) from EI-MS and indicate that caution must be used when confirming the identity of a compound only based on the match between its predicted fragments and the mass spectrum.

Raman spectroscopic and structural studies of indigo and its four 6,6′-dihalogeno analogues

The Raman and electron impact mass spectra of synthetic indigo and its four 6,6'-dihalogeno analogues are reported and discussed. The influence of varying the halogen on these Raman spectra is considered. Particular emphasis is laid on distinguishing indigo from 6,6'-dibromoindigo and differentiating between the dihalogenocompounds, so as to develop protocols for determining whether artefacts are coloured with dyes of marine or terrestrial origin and whether such artefacts are dyed with genuine "Tyrian Purple" or with dihalogenoindigo substitutes that do not contain bromine. The value of even low resolution electron impact mass spectrometry in a forensic context as a means of identifying authentic 6,6'-dibromoindigo and distinguishing it from its dihalogenoanalogues is emphasised

Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L−1 or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.

Identification of Bromohydrins in Ozonated Waters

Because ozonation is becoming a popular alternative to chlorination for disinfection of drinking water and little is known about the potential adverse health effects of ozonation disinfection by-products (DBPs), we have sought to identify ozone DBPs, particularly brominated organics, which are of principal concern due to their anticipated toxicity. Using gas chromatography coupled (independently) to low-resolution electron-impact mass spectrometry (LR-EI-MS), high-resolution EI-MS, chemical ionization MS (with 2% ammonia in methane), and Fourier transform infrared spectrometry, we have identified a series of bromohydrins and related compounds detected in extracts of an ozonated natural water sample that was artificially enhanced with bromide. The bromohydrins, which constituted the majority of by-products in the samples we studied, were detected but could not be identified by GC/LR-EI-MS, the technique used almost exclusively for environmental monitoring. A key to identifying the bromohydrins was the manifestation of intramolecular hydrogen bonding in the gas-phase IR spectra. Many of the by-products had two chiral centers, and both diastereomers were present and were separated by GC. In most cases, the IR spectra also permitted us to distinguish between diastereomers. We interpreted the IR and EI-MS spectra of several representative compounds in detail, and gave peak assignments for all that were identified. Molecular mechanics calculations and an experimental determination of the enthalpy change for conversion of free and hydrogen-bound conformers for a representative bromohydrin were used to verify the IR interpretations.

Carboxylic anhydrides-orthoesters —novel reagent systems for derivatization of aminoalkanephosphonic acids for characterization by gas chromatography and mass spectrometry. III

Studies of the derivatization of aminoalkanephosphonic acids by means of carboxylic anhydrides-trialkyl orthoester systems are reported. Gas chromatographic separations of mixtures of derivatized 1-aminoalkane-phosphonic acids and low-resolution electron impact mass spectra for the derivatives studied are presented.

Multispectral Identification of Chlorine Dioxide Disinfection Byproducts in Drinking Water

This paper discusses the identification of organic disinfection byproducts (DBPs) at a pilot plant in Evansville, IN, which uses chlorine dioxide as a primary disinfectant. Unconventioal multispectral identification techniques (gas chromatograpby combined with high- and low-resolution electron-impact mass spectrometry, low-resolution chernical ionization mass spectrometry, and Fourier transform infrared spectroscopy) were used to identify more than 40 DBPs in finished water at a chlorine dioxide pilot plant in Evansville, IN. Treatment variations included the use of liquid versus gaseous chlorine dioxide and the use of residual chlorine

Orthoformates as reagents for derivatization of aminoalkanephosphonic acids for characterization by gas chromatography—mass spectrometry

Studies of the derivatization of aminoalkanephosphonic acids by trialkyl orthoformates are reported. Gas chromatographic retention data and low-resolution electron impact mass spectra for the derivatives are presented.

Multispectral identification of alkyl and chloroalkyl phosphates from an industrial effluent

Multispectral techniques (gas chromatography combined with low and high resolution electron-impact mass spectrometry, low and high resolution chemical ionization mass spectrometry, and Fourier transform infrared spectroscopy) were used to identify 13 alkyl and chloroalkyl phosphates in a water sample taken from the effluent of a plant that manufactures fire-retardant chemicals. Of the 13 phosphates identified, only 4 were located in library mass spectral data bases; thus, techniques other than conventional low resolution electron-impact mass spectrometry with data base matching were required. Several of the identified phosphates are commonly used fire retardants; however, three exhibited chemical structures different from those of the commercially manufactured fire retardants and the reactants used in their synthesis.

Microcomputer program for determining elemental compositions of unknown organic compounds from low-resolution electron impact mass spectra

Tenhosaari, A., 1990. Microcomputer program for determining elemental compositions of unknown organic compounds from low-resolution electron impact mass spectra. Chemometrics and Intelligent Laboratory Systems, 8: 167-171. A new microcomputer program has been developed for the determination of elemental compositions (gross formulae) of unknown organic compounds from low-resolution electron impact mass spectra. The program generates all possible formulae within given limits, and tests how well they correspond to the observed spectrum by simultaneously matching isotope patterns of all ions in the spectrum to the theoretically calculated isotope patterns. The program offers an alternative method to accurate mass determination with high-resolution mass spectroscopy, when elemental compositions of unknown compounds are to be determined.

Plasticizers as contaminants in commercial ethanol.

A batch of 95% ethanol caused unusually strong disordering of biomembranes, which could be detected either by fluorescence anisotropy in synaptosomal membranes or by electron paramagnetic resonance spectroscopy in erythrocyte membranes. The contaminated batches of ethanol were visibly fluorescent when evaporated on filter paper. The adulterants were separated by capillary gas chromatography and the ubiquitous pollutant dioctylphthalate was identified by its low resolution electron impact mass spectrum. The remaining peaks, which were not recognized by any of the available mass spectral libraries, were identified by high resolution electron impact and chemical ionization mass spectrometry and low resolution tandem mass spectrometry using fast atom bombardment ionization; they were triethylene glycol esters and aryl phosphates. All the contaminants are industrial plasticizers. Distillation resulted in loss of the strong disordering properties of the alcohol.

Mass Spectrometry in the Structural Studies of Oligosaccharides

Abstract On the basis of the reported low-resolution electron impact (EI) mass spectral decomposition patterns of a few underivatlsed simple disaccnarides1-3 and the results of a high-resolution electron impact mass spectrum of a model disaccharide β-methyl pachybioside,4 a common fragmentation pathway of such compounds could be worked out. Using the derived standard decomposition pathways, structure of a novel tetrasaccharide, orthenthose, has been elucidated as oleandrose tetrasaccharide.

Application of mass spectrometry in the regulatory analysis of pesticides and industrial chemicals in food and feed commodities.

During regulatory analysis of pesticides and industrial chemicals, compounds are frequently encountered which cannot be readily identified by gas chromatography alone on two or more stationary phases. Such incurred unknown analytical responses are examined by gas chromatography mass spectrometry, particularly if they have been shown to contain P, S, N or halogen via specific gas chromatography detectors. Seven case histories are presented to illustrate the analytical approach adopted to structurally elucidate such compounds at the ppm level. These examples demonstrate the potential complementary combination provided by low resolution electron impact and chemical ionization mass spectrometry in structural determinations.

Effect of substituents on the relative abundance of two main fragments in the electron impact mass spectra of substituted 2-(N,N-dimethylamino)ethyl phenyl phenylphosphonates

Low resolution electron impact mass spectra of the title compounds at 70 eV show only two main peaks: m/z 71 [C 4H 9N] +· and m/z 58 [C 3H 8N] +. The relative intensity of the peaks changes when the substituent is changed at 4-position of either phenyl ring. Unexpectedly deviation from linear correlation was observed between log(71/58) and the σ p (or σ p +) parameter, indicating change in the fragmentation mechanism. The results are also examined in the light of the decomposition of the neutral molecules in solution and the 31P chemical shifts of the respective oxalates.

Primary structure of a chloramphenicol acetyltransferase: mass spectrometric studies.

Low resolution electron impact mass spectrometry has been used as a major tool in the sequencing of a chloramphenicol acetyltransferase (mol. wt 25 668). Mass spectrometric data from mixtures of peptides from elastase, chymotryptic and subtilisin digests have defined 83% of the protein sequence. Several, previously unrecognized, peptide fragmentation pathways are reported.

Fragmentation of dihydro‐ and tetrahydro‐1,5‐benzothiazepines under electron impact

AbstractThe fragmentation mechanisms of dihydro‐ and tetrahydro‐1,5‐benzothiazepines under electron impact have been studied in detail using high resolution mass spectrometry, metastable decompositions and deuterium labelling techniques. Both kinds of the benzothiazepines possess high stability. The [MSH]+ and the cyclic benzothiazole ions derived from the fragmentation and severe skeletal rearrangement of the molecular ion comprised the main features of the spectra. Some doubly charged ions were noticed in the low resolution electron impact mass spectra.

A new technique for determining the hydride transfer stereospecificity of nicotinamide adenine dinucleotide-linked oxidoreductases: Electron impact and field desorption mass spectrometry

The stereospecificity of nicotinamide adenine dinucleotide-linked oxidoreductases can be determined directly without additional purification and with high sensitivity by low-resolution electron impact mass spectrometry and low-resolution field desorption mass spectrometry. The ease and reliability of this new technique is demonstrated by studying the hydride transfer stereospecificity of lactate dehydrogenase from pig heart (known to be A-specific) and glutamate dehydrogenase from beef liver (known to be B-specific). In addition the stereospecificity of glutamate dehydrogenases from duckweed ( Lemna minor) was found to be B-specific. The sample quantity of the unpurified products needed is about 1 μg. The time required for one mass spectrometric determination was about 30 min.

A mass spectrometric strategy for the rapid screening of homologous proteins: Studies on a pseudomonas azurin

We describe a mass spectrometric strategy for the rapid screening of homologous proteins. The method involves non-specific enzymic digestion followed by a single ion-exchange purification step. Mixtures of peptides are then sequenced by low resolution electron impact mass spectrometry. Peptides are aligned by homology with a type sequence thus obviating the necessity for obtaining overlap information. The procedure, which is rapid and reliable, is illustrated by work on a Pseudomonas azurin.