Comparison of indirect and direct quantification of esters of monochloropropanediol in vegetable oil.

The presence of fatty acid esters of monochloropropanediol (MEs) in food is a recent concern raised due to the carcinogenicity of their hydrolysable moieties 2- and 3-monochloropropanediol (2- and 3-MCPD). Several indirect methods for the quantification of MEs have been developed and are commonly in use until today, however significant discrepancies among analytical results obtained are challenging their reliability. The aim of the present study was therefore to test the trueness of an indirect method by comparing it to a newly developed direct method using palm oil and palm olein as examples. The indirect method was based on ester cleavage under acidic conditions, derivatization of the liberated 2- and 3-MCPD with heptafluorobutyryl imidazole and GC-MS determination. The direct method was comprised of two extraction procedures targeting 2-and 3-MCPD mono esters (co-extracting as well glycidyl esters) by the use of double solid phase extraction (SPE), and 2- and 3-MCPD di-esters by the use of silica gel column, respectively. Detection was carried out by liquid chromatography coupled to time of flight mass spectrometry (LC-ToF-MS). Accurate quantification of the intact compounds was assured by means of matrix matched standard addition on extracts. Analysis of 22 palm oil and 7 palm olein samples (2- plus 3-MCPD contamination ranged from 0.3 to 8.8 µg/g) by both methods revealed no significant bias. Both methods were therefore considered as comparable in terms of results; however the indirect method was shown to require less analytical standards, being less tedious and furthermore applicable to all type of different vegetable oils and hence recommended for routine application.

Determination of seven glycidyl esters in edible oils by gel permeation chromatography extraction and liquid chromatography coupled to mass spectrometry detection.

A method based on a gel permeation chromatography (GPC) extraction procedure combined with an additional cleanup by solid-phase extraction (SPE) on silica gel and liquid chromatography-mass spectrometry (LC-MS) detection has been validated for the analysis of seven glycidyl esters (GEs) including glycidyl laurate, myristate, palmitate, stearate, oleate, linoleate, and linolenate in various edible oils. This method was conjointly developed and validated by two different laboratories, using two different detection systems, a LC time of flight MS (LC-ToF-MS) and a LC triple-quadrupole MS (LC-MS/MS). The extraction procedure allowed targeting low contamination levels due to a highly efficient matrix removal from the 400 mg oil sample loaded on the GPC column and is suitable for routine analysis as 24 samples can be extracted in an automated and reproducible way every 12 h. GPC extraction combined with SPE cleanup and LC-MS/MS detection leads to a limit of quantification in oil samples between 50 and 100 µg/kg depending on the type of glycidyl ester. Recoveries ranged from 68 to 111% (average = 93%). Quantification was performed by automated standard addition on extracts to compensate matrix effects artifacts. To control recoveries of each sample four isotopically labeled GEs ((13)C(3) or (13)C(4)) were included in the method.

Semiquantitative analysis of 3-butenyl isothiocyanate to monitor an off-flavor in mustard seeds and glycosinolates screening for origin identification.

The present paper describes the development of an analytical method for the semiquantitative analysis of 3-butenyl isothiocyanate in mustard seeds, this compound being linked to an undesirable (at least for the European palate) off-flavor. 3-Butenyl isothiocyanate is one of the enzymatic degradation products of gluconapin, a member of the glucosinolate family of compounds. A headspace-gas chromatography-mass spectrometry (HS-GC-MS) method has been developed for the rapid analysis of 3-butenyl isothiocyanate in mustard seeds. The cross-check of this HS-GC-MS method has been made on the basis of the analysis of the native gluconapin using liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF-MS). Both techniques gave comparable results. The HS-GC-MS method was kept as the method of choice as it is rapid and solvent-free. Because yellow mustard seeds do not normally contain gluconapin, its presence in such seeds above the limit of detection was already considered as a criterion for potentially problematic mustard batches. However, "organoleptically" acceptable brown mustard seeds already contained measurable amounts of gluconapin and had to be differentiated from mustard seeds containing nonacceptable levels of gluconapin, as it is typically the case for brown mustard originating from the Indian subcontinent. Thus, a 3-butenyl isothiocyanate content "cut point" has been established to discriminate between batches. This limit could then be applied for the acceptance or rejection of mustard seed batches. In addition, LC-TOF-MS screening of mustard seeds from different geographic origins showed the heterogeneity of the glucosinolate profile and the difficulty to find good origin markers.

Direct determination of recombinant bovine somatotropin in plasma from a treated goat by liquid chromatography/high-resolution mass spectrometry.

Recombinant bovine somatotropin (rbST) is used in dairy cattle to enhance milk production. Despite the ban on this hormone in some countries, especially in Europe, there is so far no method available for the direct detection of rbST either in milk or in plasma. An analytical strategy has been developed to analyze rbST in plasma, including a purification procedure based on a precipitation with ammonium sulphate, followed by a solid-phase extraction (SPE)-based clean-up on C4 sorbent and precipitation with cold methanol. The hormone was then digested with trypsin and analyzed by liquid chromatography/high-resolution mass spectrometry (LC/HRMSn) on a linear ion trap coupled with an Orbitrap. The tryptic N-terminal peptide, specific to the difference between the endogenous and recombinant form of the somatotropin, was fragmented and product ions were analyzed at high mass resolution. Applying this approach to goat plasma allowed the direct detection of 10 ng mL(-1) of rbST in fortified samples. It also showed the presence of rbST in plasma collected from a goat treated with the hormone, even 2 days after administration. These results are of a great interest in the field of somatotropin control and undoubtedly constitute a first step in the development of a method for the detection of rbST not only in bovine plasma, but also in other biological matrices such as milk.

Rapid determination of furan in heated foodstuffs by isotope dilution solid phase micro-extraction-gas chromatography--mass spectrometry (SPME-GC-MS).

An analytical method is reported to determine trace amounts of furan in several different commercial foodstuffs that are subjected to thermal treatment. The SPME-GC-MS method is rapid and robust, and entails the following steps: addition of deuterated furan to the sample, sodium chloride-assisted extraction into the headspace, cryofocussing, and finally fibre desorption and GC-MS analysis. Furan is quantified by the use of an external calibration curve, achieving a decision limit (CC alpha) and detection capability (CC beta) of 17 pg and 43 pg, respectively, as absolute furan concentration in a 10 ml headspace vial. The method is applicable to a wide variety of foods, including fruits juices, baby foods in jars, canned foods, pet food, coffee and coffee substitutes. Typical amounts of furan found in selected foodstuffs range from about 1 microg kg(-1) (fruit juice) to 110 microg kg(-1) (baby food containing cooked vegetables). In-house validation data show good precision and accuracy of the method, with a typical repeatability of between 5 and 16% in different food matrices, and trueness determined in orange juice and coffee as 87 and 93%, respectively. Moreover, the measurement uncertainty has been evaluated for two matrices (fruit juice and coffee). Studies on short-term stability of furan in certain foods are also presented, and show that the furan content decreases in food while heating for preparation or reconstitution.

Quantitative determination of four nitrofuran metabolites in meat by isotope dilution liquid chromatography-electrospray ionisation-tandem mass spectrometry.

A confirmatory method based on isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the low-level determination of residues of four nitrofuran veterinary drugs in meat, e.g., furazolidone, furaltadone, nitrofurantoin, and nitrofurazone. The procedure entails an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2-nitrobenzaldehyde (NBA) imine-type derivatives. Liquid-liquid extraction and clean-up on a polymeric solid phase extraction cartridge are then performed before LC-MS/MS analysis by positive electrospray ionisation (ESI) applying multiple reaction monitoring of three transition reactions for each compound. Reliable quantitation is obtained by using one deuterated analogue per analyte (d4-NBA derivative) as internal standard (IS). Validation of the method in chicken meat was conducted following the European Union (EU) criteria for the analysis of veterinary drug residues in foods. The decision limits (CCalpha) were 0.11-0.21 microg/kg, and the detection capabilities (CCbeta) 0.19-0.36 microg/kg, thus below the minimum required performance limit (MRPL) set at 1 microg/kg by the EU. The method is robust and suitable for routine quality control operations, and more than 200 sample injections were performed without excessive pollution of the mass spectrometer or loss of LC column performance.

Analysis of dyes in illicit pills (amphetamine and derivatives).

The determination of dyes present in illicit pills is shown to be useful and easy-to-get information in strategic and tactical drug intelligence. An analytical strategy including solid-phase extraction (SPE) thin-layer chromatography (TLC) and capillary zone electrophoresis equipped with a diode array detector (CZE-DAD) was developed to identify and quantify 14 hydrosoluble, acidic, synthetic food dyes allowed in the European Community. Indeed, these may be the most susceptible dyes to be found in illicit pills through their availability and easiness of use. The results show (1) that this analytical method is well adapted to small samples such as illicit pills, (2) that most dyes actually found belong to hydrosoluble, acidic, synthetic food dyes allowed in the European Community, and (3) that this evidence turns out to be important in drug intelligence and may be assessed into a Bayesian framework.

In-depth mechanistic study on the formation of acrylamide and other vinylogous compounds by the maillard reaction.

The formation of acrylamide was studied in low-moisture Maillard model systems (180 degrees C, 5 min) based on asparagine, reducing sugars, Maillard intermediates, and sugar degradation products. We show evidence that certain glycoconjugates play a major role in acrylamide formation. The N-glycosyl of asparagine generated about 2.4 mmol/mol acrylamide, compared to 0.1-0.2 mmol/mol obtained with alpha-dicarbonyls and the Amadori compound of asparagine. 3-Hydroxypropanamide, the Strecker alcohol of asparagine, generated only low amounts of acrylamide ( approximately 0.23 mmol/mol), while hydroxyacetone increased the acrylamide yields to more than 4 mmol/mol, indicating that alpha-hydroxy carbonyls are much more efficient than alpha-dicarbonyls in converting asparagine into acrylamide. The experimental results are consistent with the reaction mechanism based on (i) a Strecker type degradation of the Schiff base leading to azomethine ylides, followed by (ii) a beta-elimination reaction of the decarboxylated Amadori compound to afford acrylamide. The beta-position on both sides of the nitrogen atom is crucial. Rearrangement of the azomethine ylide to the decarboxylated Amadori compound is the key step, which is favored if the carbonyl moiety contains a hydroxyl group in beta-position to the nitrogen atom. The beta-elimination step in the amino acid moiety was demonstrated by reacting under low moisture conditions decarboxylated model Amadori compounds obtained by synthesis. The corresponding vinylogous compounds were only generated if a beta-proton was available, for example, styrene from the decarboxylated Amadori compound of phenylalanine. Therefore, it is suggested that this thermal pathway may be common to other amino acids, resulting under certain conditions in their respective vinylogous reaction products.

Improved sample preparation to determine acrylamide in difficult matrixes such as chocolate powder, cocoa, and coffee by liquid chromatography tandem mass spectroscopy.

An improved sample preparation (extraction and cleanup) is presented that enables the quantification of low levels of acrylamide in difficult matrixes, including soluble chocolate powder, cocoa, coffee, and coffee surrogate. Final analysis is done by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) using d3-acrylamide as internal standard. Sample pretreatment essentially encompasses (a) protein precipitation with Carrez I and II solutions, (b) extraction of the analyte into ethyl acetate, and (c) solid-phase extraction on a Multimode cartridge. The stability of acrylamide in final extracts and in certain commercial foods and beverages is also reported. This approach provided good performance in terms of linearity, accuracy and precision. Full validation was conducted in soluble chocolate powder, achieving a decision limit (CCalpha) and detection capability (CCbeta) of 9.2 and 12.5 microg/kg, respectively. The method was extended to the analysis of acrylamide in various foodstuffs such as mashed potatoes, crisp bread, and butter biscuit and cookies. Furthermore, the accuracy of the method is demonstrated by the results obtained in three inter-laboratory proficiency tests.