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PubMed2002

Characterization and origin identification of 2,4,6-trinitrotoluene through its by-product isomers by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

The by-products of industrial 2,4,6-trinitrotoluene (TNT), including isomers of trinitrotoluene, dinitrotoluene, trinitrobenzene and dinitrobenzene were investigated using liquid chromatography-mass spectrometry (LC-MS), in order to build a profile for the characterization of TNT samples from various origins. LC-MS with atmospheric pressure chemical ionization, in the negative-ion mode, was found to be the most suitable method for this study. The characterization of TNT by the by-product profile was demonstrated on a variety of TNT samples.

Atmospheric Pressure↗
PubMed2002

Atmospheric pressure chemical ionization studies of non-polar isomeric hydrocarbons using ion mobility spectrometry and mass spectrometry with different ionization techniques.

The ionization pathways were determined for sets of isomeric non-polar hydrocarbons (structural isomers, cis/trans isomers) using ion mobility spectrometry and mass spectrometry with different techniques of atmospheric pressure chemical ionization to assess the influence of structural features on ion formation. Depending on the structural features, different ions were observed using mass spectrometry. Unsaturated hydrocarbons formed mostly [M - 1]+ and [(M - 1)2H]+ ions while mainly [M - 3]+ and [(M - 3)H2O]+ ions were found for saturated cis/trans isomers using photoionization and 63Ni ionization. These ionization methods and corona discharge ionization were used for ion mobility measurements of these compounds. Different ions were detected for compounds with different structural features. 63Ni ionization and photoionization provide comparable ions for every set of isomers. The product ions formed can be clearly attributed to the structures identified. However, differences in relative abundance of product ions were found. Although corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra detected are complex and differ from those obtained with 63Ni ionization and photoionization.

Atmospheric Pressure↗
PubMed2000

Determination of rice herbicides, their transformation products and clofibric acid using on-line solid-phase extraction followed by liquid chromatography with diode array and atmospheric pressure chemical ionization mass spectrometric detection.

A simultaneous method for the trace determination of acidic, neutral herbicides and their transformation products in estuarine waters has been developed through an on-line solid-phase extraction method followed by liquid chromatography with diode array and mass spectrometric detection. An atmospheric pressure chemical ionization (APCI) interface was used in the negative ionization mode after optimization of the main APCI parameters. Limits of detection ranged from 0.1 to 0.02 ng/ml for 50 ml of acidified estuarine waters preconcentrated into polymeric precolumns and using time-scheduled selected ion monitoring mode. Two degradation products of the acidic herbicides (4-chloro-2-methylphenol and 2,4-dichlorophenol) did not show good signal response using APCI-MS at the concentration studied due to the higher fragmentor voltage needed for their determination. For molinate and the major degradation product of propanil, 3,4-dichloroaniline, positive ion mode was needed for APCI-MS detection. The proposed method was applied to the determination of herbicides in drainage waters from rice fields of the Delta del Ebro (Spain). During the 3-month monitoring of the herbicides, 8-hydroxybentazone and 4-chloro-2-methylphenoxyacetic acid were successively found in those samples.

Atmospheric Pressure↗
PubMed2001

Monitoring of antifouling agents in water samples by on-line solid-phase extraction-liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An automatic method for determining diuron, irgarol 1051, folpet and dichlofluanid in seawater samples have been developed. This method is based on the on-line coupling of solid-phase extraction (SPE) with a highly crosslinked polymeric sorbent, LiChrolut EN, to liquid chromatography followed by atmospheric pressure chemical ionization (APCI) and mass spectrometry. The operational parameters affecting the APCI interface have been studied in both positive and negative ionization modes. The use of LiChrolut EN in the SPE produced recoveries of over 85% for all the compounds when 100 ml of seawater sample was preconcentrated. Calibration was carried out in both ionization modes and in full-scan and selected-ion monitoring (SIM). The method allowed all the analytes to be detected at 5 ng l(-1) in SIM acquisition mode except folpet, which, because of its low response, could only be detected at 250 ng l(-1). The method was used to analyse water samples taken from five different marina and fishing ports along the coast of Tarragona, Catalonia (Spain), over a 5-month period. Diuron and irgarol 1051 were detected and quantified in most samples at concentration levels ranging from 27 to 420 ng l(-1) for diuron and from 15 to 511 ng l(-1) for irgarol 1051.

Atmospheric Pressure↗
PubMed2000

Negative atmospheric pressure chemical ionisation low-energy collision activation mass spectrometry for the characterisation of flavonoids in extracts of fresh herbs.

The flavonoid composition of commonly eaten fresh herbs such as dill, oregano and parsley was analysed by combined LC, MS and low-energy collision induced dissociation (CID) MS-MS. Negative atmospheric pressure chemical ionisation (APCI) MS and MS-MS were used to provide molecular mass information and product-ion spectra of the glycosyl compounds. The most prominent fragment was found to arise from the aglycone ion, which provides molecular mass information about the glycosyl substituent and the aglycone. Product-ion spectra of the aglycone verified the identity by comparison with product-ion spectra of authentic standards. Methoxylated flavonoids provide characteristic fragmentation, i.e., loss of *CH3, which add to the usefulness of the method for identifying unknown flavonoids. Negative-mode APCI-MS is thus demonstrated to be a good alternative to the commonly employed positive mode operation.

Atmospheric Pressure↗
PubMed2024

Simulation and experimental study of a cold atmospheric pressure plasma and comparison of efficiency in boosting recombinant Endoglucanase II production in Pichia pastoris.

Recombinant proteins are essential in various industries, and scientists employ genetic engineering and synthetic biology to enhance the host cell's protein production capacity. Stress response pathways have been found effective in augmenting protein secretion. Cold atmospheric pressure plasma (CAP) can induce oxidative stress and enhance protein production. Previous studies have confirmed the applicability of CAP jets on Phytase and green fluorescent protein (GFP) production in Pichia pastoris hosts. This study investigates the effect of CAP treatment on another valuable recombinant protein, Endoglucanase II (EgII), integrated into the Pichia pastoris genome. The results demonstrated that plasma induction via two different ignition modes: sinusoidal alternating current (AC) and pulsed direct current (DC) for 120, 180, and 240 s has boosted protein secretion without affecting cell growth and viability. The AC-driven jet exhibited a higher percentage increase in secretion, up to 45%. Simulation of plasma function using COMSOL software provided a pattern of electron temperature (Te) and density distribution, which determine the plasma cocktail's chemistry and reactive species production. Furthermore, electron density (ne) and temperature were estimated from the recorded optical spectrum. The difference in electron properties may explain the moderately different impressions on expression capability. However, cell engineering to improve secretion often remains a trial-and-error approach, and improvements are, at least partially, specific to the protein produced.

Plasma Gases↗
PubMed2003

Determination of lincomycin and tylosin residues in honey using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An analytical method for the determination of residues of the antibiotic drugs lincomycin and tylosin in honey was developed. The procedure employed a solid-phase extraction for the isolation of lincomycin and tylosin from diluted honey samples. The antibiotic residues were subsequently analyzed by reversed-phase HPLC with atmospheric pressure chemical ionization mass spectrometric detection. Average analyte recoveries for lincomycin and tylosin ranged from 84 to 107% in replicate sets of honey samples fortified with drug concentrations of 0.01, 0.5, and 10 microg/g. The method detection limits were determined to be 0.007 and 0.01 microg/g for lincomycin and tylosin, respectively.

Atmospheric Pressure↗
PubMed2004

Quantitative measurement of different ceramide species from crude cellular extracts by normal-phase high-performance liquid chromatography coupled to atmospheric pressure ionization mass spectrometry.

Normal-phase high-performance liquid chromatography (NP-HPLC) coupled to atmospheric pressure ionization mass spectrometry (APCI-MS) allows quantitative analysis of endogenous ceramide and dihydroceramide species from crude lipid extracts. Qualitative information for the species comes from observation of differences in chromatographic and mass spectrometric behavior between species (Pettus et al. Rapid Commun. Mass Spectrom. 2003; 17: 1017-1026). Quantitative analysis is achieved by (1) use of a synthetic internal standard as an extraction and injection control, (2) lack of salt adduction, ion suppression, or other matrix effects in APCI mode, and (3) consistent fragmentation and ionization of external standards across the physiologically relevant concentration range found in endogenous lipid samples. Application to the analysis and quantitation of ceramide and dihydroceramide from various cell lines is demonstrated. The results from APCI-MS analysis corroborate and enhance information acquired from use of the diacylglycerol kinase assay for total ceramide measurement. This technique readily allows simultaneous quantitation of ceramide and dihydroceramide species.

Animals↗
PubMed2002

Analysis of protein ions in the range 3000-12000 Th under partial (no discharge) atmospheric pressure chemical ionization conditions using ion trap mass spectrometry.

A new approach, based on the use of atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-ITMS), but without a corona discharge, was investigated for application to creating and monitoring protein ions. It must be emphasized that APCI is not usually used in protein analysis. In order to verify the applicability of the proposed method to the analysis of proteins, two standard proteins (horse cytochrome c and horse myoglobin) were analyzed. A mixture of the two proteins was also analyzed showing that this novel approach, based on the use of APCI, can be used in the analysis of protein mixtures.

Animals↗
PubMed2002

Analysis of peptides using partial (no discharge) atmospheric pressure chemical ionization conditions with ion trap mass spectrometry.

A novel approach, based on the use of atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-ITMS) conditions, but without using corona discharge, was used to analyze peptides. The proposed method was applied to three standard peptides (bombesin, trityrosine and tyrosine-glycine-glycine) as well as peptides obtained through enzymatic digestion of two standard proteins (horse cytochrome c and horse myoglobin).

Air Pressure↗
PubMed2004

On-line atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry.

A new technique is presented for the coupling of atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) mass spectrometry with liquid delivery systems. Mass measurements of polymers and peptides are demonstrated using a co-dissolved matrix, e.g. alpha-cyano-4-hydroxycinnamic acid (HCCA). Improvements in terms of sensitivity are achieved by optimizing the shape und control of the exit capillary and by using a laser (355 nm) at a 1 kHz repetition rate. Two calibration experiments promise a good applicability of the presented coupling method for quantitative measurements. The limit of detection achieved so far is 500 nM for peptides in methanol solution containing 25 mM HCCA.

Animals↗
PubMed2005

[Spectrum of dielectric barrier discharge at atmospheric pressure intensified by mixing a little argon].

In this paper, the spectrum of dielectric barrier discharge at atmospheric pressure was measured by using the special setup with two water electrodes. The variation of spectrum was studied when a little argon was mixed. Nitrogen molecular spectrum (C3 IIu(v' = 0 ) --> B3 IIg(v" = 0-4)) and nitrogen atomic spectrum(4d(4) D7/2 --> 3p(4)P1/2(0)) were found in the range of 300-800nm. After a little argon was mixed, the breakdown voltage of discharge obviously decreased. The spectral line intensities of nitrogen molecules and nitrogen atoms increased. The full width at half maximum (FWHM) of spectral line was obviously broadened. Because Stark broadening is a linear function of electron density, it can be seen that electron density increased after a little argon was mixed with the air, which caused the probability of excitation collision of N2 and N with electrons to increase, and the number of N2 and N excited to higher excitation state to increase. So the intensity of spectrum was intensified.

English Abstract↗
PubMed2005

Absolute method for the assay of oleuropein in olive oils by atmospheric pressure chemical ionization tandem mass spectrometry.

Oleuropein (OLP, 1), the active ingredient present (i) in food integrators extracted from olive leaves, (ii) in table olives, and (iii) in extra virgin olive oils is a nutraceutical whose health benefits have been widely documented. A new analytical method for its assay, which is based on the utilization of atmospheric pressure chemical ionization tandem mass spectrometry and on the use of a synthetic labeled analogue, the 4-trideuteriocarboxyoleuropein (2), as an internal standard, is presented. The results obtained with extra virgin olive oils from different cultivars and different Italian regions are discussed.

Atmospheric Pressure↗
PubMed2005

Determination of the sum of malachite green and leucomalachite green in salmon muscle by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry.

A sensitive method for the determination and confirmation of the sum of malachite green (MG) and leucomalachite green (LMG) in salmon muscle has been developed. It is based on the use of an oxidative pre-column reaction which converts LMG into MG previous to liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry (LC-APCI-MS) analysis. The determination of both compounds together constitutes a good screening method to confirm the presence of this kind of residue, taking into account that the combined signals will provide a gain of sensitivity. The detection limit, determined for spiked salmon samples using the confirmatory ion m/z 313, was 0.15 microg/kg. The recoveries determined at a spiking level of 2 microg/kg were 85 and 70% for LMG and MG, respectively, with respective relative standard deviations of 1.3 and 3.1%.

Aniline Compounds↗
PubMed2006

Liquid chromatography on porous graphitic carbon with atmospheric pressure photoionization mass spectrometry and tandem mass spectrometry for the analysis of glycosphingolipids.

The study of several structural variations (the length, the degree of unsaturation and hydroxylation of the alkyl chains, the number and nature of osidic residues) helped understand the behaviour of neutral glycosphingolipids (GSLs) on porous graphitic carbon stationary phase (PGC). Atmospheric pressure photoionization mass spectrometry (APPI) and tandem mass spectrometry were used to perform the detection and the identification of molecular species in positive mode where [M+H](+) and [M-H(2)O+H](+) ions provided structural information on the fatty acid and the sphingoid base. The retention of GSLs increased with the hydrocarboneous volume of their alkyl chains and with the number of osidic residues in agreement with hydrophobic properties and polar retention effect of graphite, respectively. The presence of polar groups, such as OH-group or double bond within alkyl chains, decreased their retention. The coupling of chromatography on PGC with APPI tandem mass spectrometry detection appeared a powerful technique to discriminate isobaric molecules. Isobaric solutes differing by the position of two double bonds or by the repartition of hydrocarboneous skeleton were discriminated according to their chromatographic comportment or their mass spectrum, respectively. Among isobaric molecules, only few structures differing by the nature of osidic residue were not discriminated (i.e. glucosylceramide and galactosylceramide with similar ceramide skeleton were co-eluted and no difference in mass spectra was observed).

Atmospheric Pressure↗