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PubMed2006

Trace mycotoxin analysis in complex biological and food matrices by liquid chromatography-atmospheric pressure ionisation mass spectrometry.

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are growing on agricultural commodities. Their frequent presence in food and their severe toxic, carcinogenic and estrogenic properties have been recognised as potential threat to human health. A reliable risk assessment of mycotoxin contamination for humans and animals relies basically on their unambiguous identification and accurate quantification in food and feedstuff. While most screening methods for mycotoxins are based on immunoassays, unambiguous analyte confirmation can be easily achieved with mass spectrometric methods, like gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). Due to the introduction of atmospheric pressure ionisation (API) techniques in the late 80s, LC/MS has become a routine technique also in food analysis, overcoming the traditional drawbacks of GC/MS regarding volatility and thermal stability. During the last few years, this technical and instrumental progress had also an increasing impact on the expanding field of mycotoxin analysis. The aim of the present review is to give an overview on the application of LC-(API)MS in the analysis of frequently occurring and highly toxic mycotoxins, such as trichothecenes, ochratoxins, zearalenone, fumonisins, aflatoxins, enniatins, moniliformin and several other mycotoxins. This includes also the investigation of some of their metabolites and degradation products. Suitable sample pre-treatment procedures, their applicability for high sample through-put and their influence on matrix effects will be discussed. The review covers literature published until July 2006.

Aflatoxins↗
PubMed2001

Use of atmospheric pressure ionization mass spectrometry in enantioselective liquid chromatography.

Recent advances in mass spectrometry have rendered it an attractive and versatile tool in industrial and academic research laboratories. As a part of this rapid growth, a considerable body of literature has been devoted to the application of mass spectrometry in studies involving enantioselectivity, molecular recognition, and supramolecular chemistry. In concert with separation techniques such as capillary electrophoresis and liquid chromatography, mass spectrometry allows rapid characterization of a large array of molecules in complex mixtures. A majority of these findings have been made possible by the introduction of 'soft-ionization' techniques such as electrospray ionization interface. Other techniques such as atmospheric pressure chemical ionization mass spectrometry have been widely used as a rugged interface for quantitative liquid chromatography-mass spectrometry. Herein, we present a brief overview of the above techniques accompanied with several examples of enantioselective capillary electrophoresis- and liquid chromatography-mass spectrometry in drug discovery and development. Although the emphasis of this article is on quantitative enantiomeric chromatography-mass spectrometry, we envisage that similar strategies are adaptable in qualitative studies.

Atmospheric Pressure↗
PubMed2005

Determination and characterization of organic explosives using porous graphitic carbon and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A new LC-MS method for the determination and characterization of three groups of commonly used organic explosives (nitroaromatic compounds, cyclic nitroamines and nitrate esters) was developed using a porous graphitic carbon (PGC) (Hypercarb) column. Twenty-one different explosive-related compounds--including 2,4,6-trinitrotoluene, its by-products and its degradation products--were chromatographically separated in a single analysis. This efficient separation facilitates the identification of the manufacturer of the explosive using the identified analytes as a fingerprint. A final, conclusive identification of the analytes can be obtained using LC-MS equipped with an atmospheric pressure chemical ionization (APCI) interface. Solvent effects on chromatographic behaviour were investigated, as were the effects of solvent mixtures and mobile phase additives. The number and the relative positions of the nitro groups within analyte molecules influence their order of elution; these effects were investigated. The data thus generated can be interpreted to support a hypothesis concerning the retention mechanism of nitro-containing compounds when using PGC. Limits of detection ranged from 0.5 to 41.2 ng. The new methodology described herein improves the sensitivity and selectivity of explosive detection. The effectiveness of the method is demonstrated by the analysis of soil samples containing explosives residue from test fields in Sweden and Afghanistan.

Atmospheric Pressure↗
PubMed2000

Direct identification and quantitation of prednisone in the presence of overlapping hydrocortisone by liquid chromatography with electrospray and atmospheric-pressure chemical-ionisation mass spectrometry.

The paper describes the application of liquid chromatography interfaced to a triple quadrupole mass spectrometer utilising the multiple reaction monitoring (MRM) mode. The technique was shown to provide detection limits lower than 0.01% for the analysis of prednisone in the presence of hydrocortisone. Prednisone was mixed in concentrations from 0.500 to 0.0005 ppm (corresponding to 1% to 0.001% of the hydrocortisone concentration). These solutions were assayed using MRM observing the product ion transitions of 359.2-->147.1 and 359.2-->171.2 and was shown to be capable of detecting co-eluting impurities at concentrations of less than 0.001% of the major component. The assay of prednisone was shown to be linear over the range 0.500-0.0005 ppm with a correlation coefficient of 0.999 and a precision of 6.9% at the concentration of 0.005 ppm. The analysis was carried out using both atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI) as an interface. However, for these compounds APCI provided significantly more sensitive data compared to ESI.

Atmospheric Pressure↗
PubMed2004

Approach to highly efficient dechlorination of PCDDs, PCDFs, and coplanar PCBs using metallic calcium in ethanol under atmospheric pressure at room temperature.

Detoxification of highly toxic polychlorinated aromatic compounds such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and dioxin-like compounds such as coplanar polychlorinated biphenyls (co-PCBs) under mild conditions (atmospheric pressure and room temperature) was achieved by a simple stirring operation for 24 h using metallic calcium in ethanol, without any tedious decomposition procedures and harsh conditions such as high temperature and/or high pressure. Metallic calcium can be kept stable under atmospheric conditions for a long period as compared to metallic sodium since the surface is coated with CaCO3, which is formed in the contact with air. Moreover, ethanol, which is one of the safest solvents for humans, acts not only as a solvent but also as an accelerator due to its ablility to remove the carbonated coating. This decomposition method for PCDDs, PCDFs, and co-PCBs therefore is one of the most economical and environmentally friendly detoxification methods with respect to the input energy and safety of reagents used. Concentration for each isomer of PCDDs, PCDFs, and co-PCBs was reduced in 98.32-100% conversions by treatment in ethanol at room temperature. The toxicity equivalency quantity (TEQ), which was measured by the HRGC-HRMS analysis, for the total residues of isomers was reduced from 22,000 to 210 pg TEQ/mL of hexane (conversion: 99.05%) at room temperature. By refluxing over 24 h, the conversion increased up to 99.45%.

Benzofurans↗
PubMed2003

Determination of biogenic amines as dansyl derivatives in alcoholic beverages by high-performance liquid chromatography with fluorimetric detection and characterization of the dansylated amines by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A sensitive high-performance liquid chromatographic method for the simultaneous determination of 11 biogenic amines has been developed. The method involves addition of an internal standard (1,7-diaminoheptane), pre-column dansylation of the amines and subsequent solid-phase extraction of the derivatives through C18 cartridges. The dansylamides were separated on an Inertsil ODS-3 column (250 x 4 mm I.D., 5 microm) using a 35-min gradient elution with a binary system of acetonitrile-water, a flow-rate of 1 ml min(-1) and fluorescence detection at excitation and emission wavelengths of 320 and 523 nm, respectively. The identity of the dansyl derivatives was confirmed by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. Linearity of derivatization was obtained for concentrations ranging from 0.008 to 40.0 mg l(-1). The within- and between-day relative standard deviations ranged from 0.2 to 7.6% and 0.3 to 8.6%, respectively. The overall process was successfully applied to identify and quantify biogenic amines in white-, red- and Retsina Greek wines and Greek beers, after treatment with polyvinylpyrrolidone.

Alcoholic Beverages↗
PubMed2006

Computer-assisted interpretation of atmospheric pressure chemical ionization mass spectra of triacylglycerols.

Current lipidomics approaches require simple and rapid algorithms enabling the interpretation of mass spectra of lipids. Most lipids are complex mixtures of related components in which the composition of the aliphatic fatty acid chains varies from one molecule to the next. Triacylglycerols (TAGs) are an example of such a lipid class. Fatty acid chains are the only parts of the molecule to change from one species to another. Fatty acids, and consequently also TAGs, can be characterized by two parameters; the number of carbon atoms and the number of double bonds. All calculations reflecting relations among ions in the spectra can be easily made using these parameters. An algorithm for the automated interpretation of TAGs from atmospheric pressure chemical ionization mass spectra (TriglyAPCI) is presented in this paper. The algorithm first identifies diacylglycerol fragments and molecular adducts. In the next step, relations among the ions are searched and possible TAG structures are suggested. Individual features of the algorithm are described in detail and the software performance is demonstrated for the liquid chromatography/mass spectrometric (LC/MS) analysis of TAGs isolated from the termite Prorhinotermes canalifrons.

Algorithms↗
PubMed2004

A digital ion trap mass spectrometer coupled with atmospheric pressure ion sources.

In a digital ion trap (DIT), the quadrupole trapping and excitation waveforms are generated by the rapid switching between discrete d.c. voltage levels. As the timing of the switch can be controlled precisely by digital circuitry, the approach provides an opportunity to generate mass spectra by means of a frequency scan in contrast to the conventional voltage scan, thus providing a wider mass range of analysis. An instrument has been constructed which employs a 'non-stretched' ion trap and the field fault around the aperture of the end-cap electrode can be corrected electronically using a field-adjusting electrode. The ion trap was coupled with electrospray ionization (ESI) and atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) sources to demonstrate the capability of the digital method. AP-MALDI mass spectra of singly charged ions with mass-to-charge ratios upto 17 000 Th were generated using a trapping voltage of only 1000 V. Forward and reverse mass scans at resolutions up to 19 000 and precursor ion isolation at resolutions up to 3500 with subsequent tandem mass spectrometric analysis were demonstrated. The method of generating the digital waveforms and period scan is described. Discussion of the issues of mass range, scan speed, ion trapping efficiency and collision-induced dissociation efficiency are also provided.

Animals↗
PubMed2001

Liquid chromatography-UV determination and liquid chromatography-atmospheric pressure chemical ionization mass spectrometric characterization of sitosterol and stigmasterol in soybean oil.

A narrow-bore HPLC-UV method was developed for the analysis of two of the more abundant naturally occurring phytosterols in vegetable oils: sitosterol and stigmasterol. The method enabled detection of the compounds at a concentration of 0.42 microg/ml and quantitation at concentrations of 0.52 and 0.54 microg/ml for sitosterol and stigmasterol, respectively. An excellent linearity was determined over two orders of concentration magnitude (r2 0.999-1.000) and verified by applying the Mandel fitting test (p>0.099) and the lack-of-fit test (p>0.057) performed at the 95% confidence level. A good intra-day precision ranging from 0.15 to 1.16% was calculated at two concentration levels (2 and 100 microg/ml). The inter-day reproducibility was verified on 3 different days by performing an homoscedasticity test and analysis of variance. A solid-phase extraction method was developed on silica cartridges for the isolation of phytosterols from soybean oil providing recovery values of 101+/-9 and 106+/-7% for sitosterol and stigmasterol, respectively. Good accuracy of the method was statistically demonstrated since no matrix effect was found for both the analytes. The developed method was applied to the quantitative assay of phytosterols in a soybean oil sample (61+/-5 mg/100 g of stigmasterol and 118+/-4 mg/100 g sitosterol). The HPLC-atmospheric pressure chemical ionization MS technique enabled the identification of stigmasterol, sitosterol and campesterol in the oil sample.

Atmospheric Pressure↗
PubMed2000

Comparison of various liquid chromatographic methods involving UV and atmospheric pressure chemical ionization mass spectrometric detection for the efficient trace analysis of phenylurea herbicides in various types of water samples.

The performance of mass spectrometric (MS) detection and UV detection in combination with reversed-phase liquid chromatography without and with the use of coupled column RPLC (LC-LC) has been compared for the trace analysis of phenylurea herbicides in environmental waters. The selected samples of this comparative study originated from an inter-laboratory study. For both detection modes, a 50 mm x 4.6 mm I.D. column and a 100 mm x 4.6 mm I.D. column packed with 3 microm C18 were used as the first (C-1) and second (C-2) column, respectively. Atmospheric pressure chemical ionization mass spectrometry was performed on a magnetic sector instrument. The LC-LC-MS analysis was carried out on-line by means of direct large volume (11.7 ml) injection (LVI). The performance of both on-line (LVI, 4 ml of sample) and off-line LC-LC-UV (244 nm) analysis was investigated. The latter procedure consisted of a solid-phase extraction (SPE) of 250 ml of water sample on a 500 mg C18 cartridge. The comparative study showed that LC-LC-MS is more selective then LC-LC-UV and, in most cases, more sensitive. The LVI-LC-LC-MS approach combines direct quantification and confirmation of most of the analytes down to a level of 0.01 microg/l in water samples in less then 30 min. As regards LC-LC-UV, the off-line method appeared to be a more viable approach in comparison with the on-line procedure. This method allows the screening of phenylurea's in various types of water samples down to a level of at least 0.05 microg/l. On-line analysis with LVI provided marginal sensitivity (limits of detection of about 0.1 microg/l) and selectivity was sometimes less in case of surface water samples. Both the on-line LVI-LC-LC-MS method and the LC-LC-UV method using off-line SPE were validated by analysing a series of real-life reference samples. These samples were part of an inter-laboratory test and contained residues of herbicides ranging from 0.02 to 0.8 microg/l. Beside good correlation between the methods the data agreed very well with the true values of the samples.

Atmospheric Pressure↗
PubMed2006

Procedure for increasing the detection responses of estrogens in LC-MS based on introduction of a nitrobenzene moiety followed by electron capture atmospheric pressure chemical ionization.

A practical procedure for determining estrogens in biological fluids has been studied using liquid chromatography-electron capture atmospheric pressure chemical ionization-mass spectrometry combined with derivatization. Among the commercially available reagents (4-nitrobenzoyl chloride, 2,4-dinitrofluorobenzene, 4-nitrobenzenesulfonyl chloride and 4-nitrobenzyl bromide), 4-nitrobenzenesulfonyl chloride was of the most practical use; it rapidly and quantitatively reacted with estrogens and increased the detection responses by 8-23 times. The derivatization method allowed the reproducible and accurate quantification of serum and urine estrone and estradiol of a pregnant woman, which is useful for diagnosis of the fetoplacental function, with small amounts (10 mul) of sample and a simple pretreatment procedure. Tatsuya Higashiis Associate Professor of the Laboratory of Clinical Analytical Sciences (Professor Kazutake Shimada's research group) at the Graduate School of Natural Science and Technology of Kanazawa University. He received the Japan Society for Analytical Chemistry Award for Young Scientists in 2003 and the Pharmaceutical Society of Japan Award for Young Scientists in 2006. His current research interests are the development of methods for increasing sensitivity in LC-MS to detect and characterize trace amounts of biologically active steroids, such as estrogens, androgens and neuroactive steroids.

Chromatography, Liquid↗
PubMed1999

Analysis of high-molecular-mass polycyclic aromatic hydrocarbons in environmental samples using liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) with molecular masses higher than 300 u were analysed using LC-atmospheric pressure chemical ionization (APCI) MS in extracts of environmental samples from Hamilton, Canada including zebra mussels from Hamilton Harbour, air particulate and coal tar. The LC-APCI-MS profiles of three molecular mass classes of PAHs (326 u, 350 u and 374 u) were compared to identify potential sources of PAH contamination in Hamilton Harbour. The Hamilton air particulate profile was also compared with an urban air reference standard (NIST SRM 1649) from Washington, DC, USA. Profiles of all extracts were similar and suggested an environmental predominance of PAHs within the three isomeric molecular mass classes studied. However, PAHs of molecular mass 326 u and 350 u were detected in extracts of coal tar and zebra mussels from Hamilton Harbour but were not detected in Hamilton air. These results indicated that some high-molecular-mass PAHs may be characteristic of contamination by coal tar.

Air Pollutants↗
PubMed2000

Quantitative analysis of levamisole in porcine tissues by high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry.

This work presents the development and the validation of an LC-MS-MS method with atmospheric pressure chemical ionization for the quantitative determination of levamisole, an anthelmintic for veterinary use, in porcine tissue samples. A liquid-liquid back extraction procedure using hexane-isoamylalcohol (95:5, v/v) as extraction solvent was followed by a solid-phase extraction procedure using an SCX column to clean up the tissue samples. Methyllevamisole was used as the internal standard. Chromatographic separation was achieved on a LiChrospher 60 RP-select B (5 microm) column using a mixture of 0.1 M ammonium acetate in water and acetonitrile as the mobile phase. The mass spectrometer was operated in MS-MS full scanning mode. The method was validated for the analysis of various porcine tissues: muscle, kidney, liver, fat and skin plus fat, according to the requirements defined by the European Community. Calibration graphs were prepared for all tissues and good linearity was achieved over the concentration ranges tested (r>0.99 and goodness of fit <10%). Limits of quantification of 5.0 ng/g were obtained for the analysis of levamisole in muscle, kidney, fat and skin plus fat tissues, and of 50.0 ng/g for liver analysis, which correspond in all cases to half the MRLs (maximum residue limits). Limits of detection ranged between 2 and 4 ng/g tissue. The within-day and between-day precisions (RSD, %) and the results for accuracy fell within the ranges specified. The method has been successfully used for the quantitative determination of levamisole in tissue samples from pigs medicated via drinking water. Moreover the product ion spectra of the levamisole peak in spiked and incurred tissue samples were in close agreement (based on ion ratio measurements) with those of standard solutions, indicating the worthiness of the described method for pure qualitative purposes.

Animals↗
PubMed2000

Part-per-trillion level determination of antifouling pesticides and their byproducts in seawater samples by off-line solid-phase extraction followed by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A new method for the simultaneous determination of antifouling pesticides and some of their byproducts such as dichlofluanid, diuron and its byproducts [demethyldiuron and 1-(3,4-dichlorophenyl)urea], (2-thiocyanomethylthio)ben: zothiazole, chlorothalonil, Sea-nine 211, Irgarol 1051 and one of its byproducts (2-methylthio-4-tert.-butylamino-s-triazine) in seawater was developed. The extraction of these compounds from the filtered seawater samples was performed off-line with different solid-phase extraction sorbents using (I) a 500 mg graphitized carbon black cartridge (ENVI-Carb) and (II) 200 mg polymeric cartridges (LiChrolut EN and Isolute ENV+) and passing 500 ml of the sample through these cartridges. The detection was carried out by reversed-phase high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry both in the negative and positive ion modes. The recovery ranged from 76 to 96% for the whole antifouling group with the ENVI-Carb cartridges and the detection limit was at the part-per-trillion level except for TCMTB. The method utilizing the polymeric cartridge proved to be very useful, time saving and with good recoveries when only Irgarol and its byproduct, Sea-nine 211 and diuron and its byproducts, have to be analyzed. The different cartridges were applied to the analysis of these pesticides in different marinas of the Catalan coast; diuron, dichlofluanid, Sea-nine 211, Irgarol as well as demethyldiuron and the Irgarol byproduct being the must ubiquitous pollutants. Maximum concentration levels were 2-3.5 microg/l of diuron and Sea-nine 211, respectively.

Atmospheric Pressure↗
PubMed2005

Rapid characterization of Bacillus spores targeting species-unique peptides produced with an atmospheric pressure matrix-assisted laser desorption/ionization source.

New and improved strategies are eagerly sought for the rapid identification of microorganisms, particularly in mixtures. Mass spectrometry remains a powerful tool for this purpose. Small acid-soluble proteins (SASPs), which are relatively abundant in Bacillus spores, represent potential biomarkers for species characterization. Despite sharing extensive sequence homology, these proteins differ sufficiently in sequence for discrimination between species. This work focuses on the differences in sequence between SASPs from various Bacillus species. Compilation of SASP sequences from protein database searches, followed by in silico trypsin digestion and analysis of the resulting fragments, identified several species-specific peptides that could be targeted for analysis using mass spectrometry. This strategy was tested and found to be successful in the characterization of Bacillus spores both from individual species and in mixtures. Analysis was performed using an ion trap mass spectrometer with an atmospheric pressure MALDI source. This instrumentation offers the advantage of increased speed of analysis and accurate precursor ion selection for tandem mass spectrometric analysis compared with vacuum matrix-assisted laser desorption/ionization and time-of-flight instruments. The identification and targeting of species-specific peptides using this type of instrumentation offers a rapid, efficient strategy for the identification of Bacillus spores and can potentially be applied to different microorganisms.

Amino Acid Sequence↗
PubMed1999

Separation and identification of polar degradation products of benzo[a]pyrene with ozone by atmospheric pressure chemical ionization-mass spectrometry after optimized column chromatographic clean-up.

The environmental relevance of oxidized degradation products of polycyclic aromatic hydrocarbons (PAHs) increases due to enhanced combustion of organic matter and fossil fuels. For PAHs consisting of more than three condensed aromatic rings, soot aerosols are the main carrier, on the surface of which they can react with trace gases like ozone. In this study the clean-up procedure and analysis of ozonized benzo[a]pyrene (B[a]P) was optimized. B[a]P and its degradation products were preseparated into three fractions. Different reversed-phase materials were evaluated for high-performance liquid chromatographic separation. Among these, a phenyl-modified silica material proved best-suited and the chromatographic separation was optimized on this material. For the detection of separated degradation products, liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) was used. With this method, 29 components could be characterized. Besides the three known main degradation products (B[a]P-1,6-dione, B[a]P-3,6-dione, B[a]P-6,12-dione, B[a]P-4,5-dione and 4-oxa-benzo[d,e,f]chrysene-5-one (B[def]C-lactone), were identified for the first time with the help of reference substances. B[def]C-lactone is known as a substance with a mutagenic potential similar to B[a]P. Several other compounds could be tentatively identified.

Atmospheric Pressure↗