Food and Drug Administration, Center for Food Safety and Applied Nutrition, Washington, DC 20204.
Sulphites in various forms have been added to foods for centuries. Their use became an issue of concern when certain sensitive individuals exhibited adverse reactions to sulphite residues in foods. Analytical methods were developed to monitor these compounds at the regulatory limit of 10 ppm. In this report, analytical methods for determining sulphites in foods are reviewed, along with a critique of their chemistry and procedural schemes. An assessment of the key features of each method category is presented together with some comparative data. The classification scheme used is based upon the fact that determination of the sulphite content of a food is influenced more by the treatment and cleanup of the test solution than by the final determinative step. Based on a 60-year database, the Monier-Williams procedure still remains the method of choice.
Meat Sci. 2012 Feb ;90 (2):304-8 21843918
Investigation on the presence of sulphites in fresh meat preparations: estimation of an allowable maximum limit.
Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Via Manfredonia 20, Foggia, Italy. email@example.com
Sulphiting agents are commonly used food additives. They are not allowed in fresh meat preparations. In this work, 2250 fresh meat samples were analysed to establish the maximum concentration of sulphites that can be considered as "natural" and therefore be admitted in fresh meat preparations. The analyses were carried out by an optimised Monier-Williams Method and the positive samples confirmed by ion chromatography. Sulphite concentrations higher than the screening method LOQ (10.0 mg · kg(-1)) were found in 100 samples. Concentrations higher than 76.6 mg · kg(-1), attributable to sulphiting agent addition, were registered in 40 samples. Concentrations lower than 41.3 mg · kg(-1) were registered in 60 samples. Taking into account the distribution of sulphite concentrations obtained, it is plausible to estimate a maximum allowable limit of 40.0 mg · kg(-1)(expressed as SO(2)). Below this value the samples can be considered as "compliant".
Rudolf Krska, Adam Becalski, Eric Braekevelt, Terry Koerner, Xu-Liang Cao, Robert Dabeka, Samuel Godefroy, Ben Lau, John Moisey, Dorothea F K Rawn, Peter M Scott, Zhongwen Wang, Don Forsyth
Food Research Division, Bureau of Chemical Safety, Food Directorate, Health Canada, Ottawa, ON, Canada.
This article covers challenges and trends in the determination of some major food chemical contaminants and allergens, which-among others-are being monitored by Health Canada's Food Directorate and for which background levels in food and human exposure are being analyzed and calculated. Eleven different contaminants/contaminant groups and allergens have been selected for detailed discussion in this paper. They occur in foods as a result of: use as a food additive or ingredient; processing-induced reactions; food packaging migration; deliberate adulteration; and/or presence as a chemical contaminant or natural toxin in the environment. Examples include acrylamide as a food-processing-induced contaminant, bisphenol A as a food packaging-derived chemical, melamine and related compounds as food adulterants and persistent organic pollutants, and perchlorate as an environmental contaminant. Ochratoxin A, fumonisins, and paralytic shellfish poisoning toxins are examples of naturally occurring toxins whereas sulfites, peanuts, and milk exemplify common allergenic food additives/ingredients. To deal with the increasing number of sample matrices and analytes of interest, two analytical approaches have become increasingly prevalent. The first has been the development of rapid screening methods for a variety of analytes based on immunochemical techniques, utilizing ELISA or surface plasmon resonance technology. The second is the development of highly sophisticated multi-analyte methods based on liquid chromatography coupled with multiple-stage mass spectrometry for identification and simultaneous quantification of a wide range of contaminants, often with much less requirement for tedious cleanup procedures. Whereas rapid screening methods enable testing of large numbers of samples, the multi analyte mass spectrometric methods enable full quantification with confirmation of the analytes of interest. Both approaches are useful when gathering surveillance data to determine occurrence and background levels of both recognized and newly identified contaminants in foods in order to estimate human daily intake for health risk assessment.
Highly sensitive and stable electrochemical sulfite biosensor incorporating a bacterial sulfite dehydrogenase.
Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, 4072, Australia.
This paper describes a highly sensitive electrochemical (voltammetric) determination of sulfite using a combination of Starkeya novella sulfite dehydrogenase (SDH), horse heart cytochrome c (cyt c), and a self-assembled monolayer of 11-mercaptoundecanol (MU) cast on a gold electrode. The biosensor was optimized in terms of pH and the ratio of cyt c/SDH. The electrocatalytic oxidation current of sulfite increased linearly from 1 to 6 microM at the enzyme-modified electrode with a correlation coefficient of 0.9995 and an apparent Michaelis constant (K(M,app)) of 43 microM. Using an amperometric method, the low detection limit for sulfite at the enzyme-modified electrode was 44 pM (signal-to-noise ratio = 3). The modified electrode retained a stable response for 3 days while losing only ca. 4% of its initial sensitivity during a 2 week storage period in 50 mM Tris buffer solution at 4 degrees C. The enzyme electrode was successfully used for the determination of sulfite in beer and white wine samples. The results of these electrochemical analyses agreed well with an independent spectrophotometric method using Ellman's reagent, but the detection limit was far superior using the electrochemical method.
Development of a new analytical method for the determination of sulfites in fresh meats and shrimps by ion-exchange chromatography with conductivity detection.
Marco Iammarino, Aurelia Di Taranto, Marilena Muscarella, Donatella Nardiello, Carmen Palermo, Diego Centonze
Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Via Manfredonia 20, 71100 Foggia, Italy.
An accurate and reliable analytical method, based on ion chromatography and suppressed conductivity detection, has been developed and validated for the quantitative determination of sulfites in fresh meats and shrimps. The chromatographic separation was accomplished by using an anion-exchange column eluted with sodium carbonate and sodium hydroxide. The optimized step-change elution, followed by column re-equilibration at the initial mobile phase composition, guaranteed a good resolution even toward endogenous interfering peaks, and an excellent retention time repeatability (1.1%, n=6). Good results in terms of sample extract stability, recovery efficiency were achieved with an extraction solvent mixture based on sodium hydroxide, fructose and EDTA. The method validation, performed by an in-house model according to Decision 657/2002/EC and Regulation 882/2004/EC, provided excellent results with respect to linearity (correlation coefficient up to 0.9998), limits of detection and quantification (2.7 and 8.2 mg kg(-1), respectively, expressed as SO(2)), expanded measurement uncertainty (below 10%), recovery values (ranging from 85% to 92%) and repeatability (down to 8%), demonstrating the conformity of the proposed method with the European directives. Finally, by major changes ruggedness studies, the method applicability to the quantitative analysis of cow hamburger, pork and horse sausage, and shrimps was demonstrated.
Electrocatalytic sulfite biosensor with human sulfite oxidase co-immobilized with cytochrome c in a polyelectrolyte-containing multilayer.
Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Golm, Germany.
An efficient electrocatalytic biosensor for sulfite detection was developed by co-immobilizing sulfite oxidase and cytochrome c with polyaniline sulfonic acid in a layer-by-layer assembly. QCM, UV-Vis spectroscopy and cyclic voltammetry revealed increasing loading of electrochemically active protein with the formation of multilayers. The sensor operates reagentless at low working potential. A catalytic oxidation current was detected in the presence of sulfite at the modified gold electrode, polarized at +0.1 V (vs. Ag/AgCl 1 M KCl). The stability of the biosensor performance was characterized and optimized. A 17-bilayer electrode has a linear range between 1 and 60 microM sulfite with a sensitivity of 2.19 mA M(-1) sulfite and a response time of 2 min. The electrode retained a stable response for 3 days with a serial reproducibility of 3.8% and lost 20% of sensitivity after 5 days of operation. It is possible to store the sensor in a dry state for more than 2 months. The multilayer electrode was used for determination of sulfite in unspiked and spiked samples of red and white wine. The recovery and the specificity of the signals were evaluated for each sample.
J AOAC Int. ;90 (4):1090-7 17760347
Determination of added sulfites in dried garlic with a modified version of the optimized Monier-Williams method.
The optimized Monier-Williams method is slightly modified so that it could be applied for determining sulfite content in dried garlic. Dried garlic sample is directly acidified in a reactor at a pH below 3. At this pH level, the alliinase enzyme activity is irreversibly blocked, and the sulfur-containing amino acids such as alliin (the most abundant) present in dried garlic cannot be transformed into corresponding thiosulfinates such as allicin, which is absent in dried garlic. This prevents allicin from reacting with added sulfites and being probably converted to S-allyl thiosulfate, which is not volatile and has no taste. It is found that at a pH below 2.4 and at boiling water temperature, allicin produces sulfur dioxide in adequate quantity to explain the false-positive results when utilizing the optimized Monier-Williams method with allicin suppression for unsulfited dried garlic samples. Finally, when garlic samples are stabilized in a phosphoric acid buffer at a final pH around 2.4, no sulfite is produced during the Monier-Williams distillation, which is further proof there are no naturally occurring sulfites in unsulfited dried garlic under these mild conditions.
J AOAC Int. ;86 (3):544-50 12852574
Determination of sulfite in dried garlic by reversed-phase ion-pairing liquid chromatography with post-column detection.
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 5100 Paint Branch Pkwy, College Park, MD 20740, USA. firstname.lastname@example.org
A method is described for determining sulfite in dried garlic. Garlic is extracted with an HCl solution to inhibit the formation of allicin, which interferes with the determination of sulfite. After cleanup of the extract on a C18 solid-phase extraction column, sulfite is converted to hydroxymethylsulfonate (HMS) by adding formaldehyde and heating to 50 degrees C. HMS is determined by reversed-phase ion-pairing liquid chromatography with post-column detection. The post-column reaction system consists of the addition of KOH to convert HMS to sulfite ion, followed by the addition of 5,5'-dithiobis(2-nitrobenzoic acid) to produce 5-mercapto-2-nitrobenzoic acid which is detected spectrophotometrically at 450 nm. Background levels in unsulfited dried garlic equivalent to < 20 ppm SO2 were found. Recoveries of HMS from spiked garlic averaged 94.8% with a coefficient of variation of 3.8%. Sulfite was found in 13 of 21 samples of dried garlic produced in China, with sulfite ranging from 114 to 445 ppm. Sulfite was found in 60% of commercial dried garlic products purchased locally. The suitability of the Monier-Williams method for determining sulfite in garlic is discussed.
Scuola Diretta a Fini Speciali in Tecnica Enologica, Università di Padova, Viale XXVIII Aprile 22, Conegliano (TV)-31015, Italy.
The EC official method of total SO2 analysis in grape juice was modified in 1990. The main improvements concerned the amount and concentration of H3PO4 used during the distillation to recover the combined SO2 and the standardization of the distillation time at 15 min. This comparative study evaluated the total SO2 level of 12 grape juices determined by five methods, including distillation, iodimetric and enzymatic-based methods. Attention was focused on the total SO2 legal limit of 10 mg/l fixed in Europe for grape juice. Analysis of variance disclosed a significant difference among the total SO2 content in grape juices determined by five methods. Each analytical method showed limits in relation of their ability to release the combined SO2. In particular, the SO2 bonded to phenolic compounds is partially released at low pH in the acidified juice leading to higher results.
ASAIO J. ;39 (3):M590-5 8268606
Formaldehyde, sodium hypochlorite, and metabisulphite are equally effective as sterilants for central delivery systems.
Department of Medicine, Thomas Jefferson College of Medicine, Thomas Jefferson University, Philadelphia, PA 19107.
Sterilants are used to disinfect reverse osmosis (RO) thin film composite membranes or peripheral loop water delivery systems. Formaldehyde (4.0% weight/volume) and metabisulphite (1.0%) were used to sterilize the RO and peripheral loop, and sodium hypochlorite (0.5%) was used to sterilize the peripheral loop with only acid/alkaline treatment of the RO; each sterilant was evaluated for 4 months. Sanitization at the machine was with sodium hypochlorite or glutaraldehyde. Quantitative RO processed water (weekly) and dialysate (4-6 from each station during the period of each sterilant) cultures were obtained. AAMI standards were used (< 200 CFU/ml RO water;< 2,000 CFU/ml dialysate). Bacterial growth exceeded Association for the Advancement of Medical Instrumentation (AAMI) limits in 16% of RO water and 4.7% of dialysate samples, but repeat cultures invariably failed to confirm initial abnormal results. Chi-square analysis showed no differences among sterilants. No difference among sterilants was noted in arithmetic or log10 mean colony counts. Sporadic low level gram positive and gram negative organism growth occurred with all sterilants. Continued "sterility" that met AAMI standards was obtained for 1 year, first with metabisulphite and then with acid/alkaline RO and sodium hypochlorite loop treatment. It is concluded that all three sterilants are effective for disinfection of hemodialysis delivery systems. Sodium hypochlorite is recommended because of its safety advantages and readily available test of adequate removal.
Department of Chemistry, Cleveland State University, OH 44115, USA.
An estimated 500,000 individuals in the US, mostly steroid-dependent asthmatics, suffer severe adverse reactions to sulfites in foods, beverages, and pharmaceutical products. In an attempt to understand the pathogenesis of sulfite hypersensitivity, we have developed an assay for the determination of total serum sulfite by utilizing:(a) reductive release of serum protein-bound sulfite;(b) derivatization of free sulfite with monobromobimane;(c) separation of sulfite-bimane from thiol-bimanes by reversed-phase HPLC; and (d) quantitation of sulfite-bimane by fluorescence detection. The detection limit of this assay was 0.44 mumol/L serum sulfite. The intra- and interassay CVs for total serum sulfite at 5.4 mumol/L were 8.1% and 22.0%, respectively. The standard addition method was used to determine total serum sulfite in normal subjects. More than 70 samples were prepared in 2-3 h, followed by automated overnight analysis. The mean concentrations (+/- SD) of total serum sulfite in female (n = 41) and male (n = 35) donors were 4.63 +/- 2.33 and 5.16 +/- 2.68 mumol/L, respectively (not statistically significant: P = 0.368). The combined mean concentration of total sulfite in both sexes was 4.87 +/- 2.49 mumol/L. There was no correlation between total serum sulfite and total serum cysteine, cysteinylglycine, homocysteine, subject age, serum cobalamin, or serum folic acid. The reference range (mean +/- 2 SD) for total serum sulfite in normal subjects is 0-9.85 mumol/L.
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A method is described for the determination of ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) in paprika and chili powder. Ethoxyquin is extracted from the spice with hexane and partitioned into 0.3N HCl. After adjusting the solution to pH 13-14, ethoxyquin is extracted into hexane, and the hexane layer is evaporated to dryness. An acetonitrile solution of the residue is then analyzed by reverse phase high pressure liquid chromatography with detection at 254 nm. The mobile phase is water-acetonitrile with ammonium acetate buffer. Recoveries from samples fortified at 50, 100, and 200 ppm averaged 92% with a coefficient of variation of 2.3%. The method was applied to a number of commercial samples of paprika and chili powder. Ethoxyquin was found in paprika samples at levels up to 63 ppm and in chili powder samples at levels up to 20 ppm.
Gas chromatographic determination of sorbitol, mannitol, and xylitol in chewing gum and sorbitol in mints.
A method has been developed for determination of sorbitol, mannitol, and xylitol in chewing gum and sorbitol in mints. Chewing gum is partitioned between methylene chloride and water; the mint is simply dissolved in water. The aqueous extract is dried and the residue is derivatized with pyridine-acetic anhydride to form the corresponding peracetates. The derivatives are quantitated by gas chromatography using a 9 ft x 2 mm column packed with 10% Silar 10C on Chromosorb W/AW. Average recoveries of these sugar alcohols ranged from 96 to 102%.
Liquid chromatographic determination of aspartame in dry beverage bases and sweetener tablets with confirmation by thin layer chromatography.
A liquid chromatographic method is described for the determination of aspartame in dry beverage bases and sweetener tablets. The sample was mixed with the mobile phase, the pH was adjusted to within +/- 0.1 pH unit of the mobile phase, and the sample was diluted to volume with the mobile phase. The solution was filtered and a 10 microL aliquot was injected onto a C18 reverse phase column. Aspartame was quantitated with an ultraviolet detector. Recoveries of aspartame ranged from 94 to 111%. The dry beverage bases contained 5-13% aspartame and the sweetener tablets contained 19% aspartame. The presence of aspartame was confirmed by using thin layer chromatography.
The Monier-Williams distillation procedure has a long history of successful use for determining sulfite in fruit products and wine; however, a systematic evaluation of its accuracy and precision with other food matrices has not been undertaken. We found that the Monier-Williams distillation yielded greater than 90% recovery of sulfite added to foods such as table grapes, hominy, dried mangoes, and lemon juice. Less than 85% recovery was obtained with broccoli, soda crackers, cheese-peanut butter crackers, mushrooms, and potato chips. These results may, in fact, accurately reflect the residual levels of sulfite if a portion of the sulfite undergoes irreversible reaction with some food components. Analysis of commercial food products gave sulfite levels ranging from 1400 ppm in dried apple slices to 25 ppm in cream sherry.
The chemical transformations of BHT and BHA in the deep-fat frying of potatoes were studied. Approximately 80% of the BHT and its associated decomposition products was lost from the lard after six batches of french fries. This may have been due to steam distillation caused by the water boiled out of the potatoes. In contrast, 80% of the radiocarbon introduced as radiolabelled BHA was retained by the frying medium even after 12 batches of french fries. The concentration of intact BHA decreased to undetectable levels after four batches. Because of the complexity of the products formed in the heated fats, studies were undertaken on the thermolysis of a hydroperoxy derivative of BHT, 2,6-di-tert-butyl-4-hydroperoxy-4-methylcyclohexa-2,3-dienone+++(HBHT). The product mixture, which was identified by mass spectrometry and gas chromatography-mass spectrometry, included BHT, 2,6-di-tert-butyl-4-hydroxy-4-methylcyclohexa-2,5-dienone and 3,5-di-tert-butyl-4-hydroxybenzaldehyde. Elemental compositions of other unidentified products were determined by high-resolution mass spectrometry.
Sulphite stabilization and high-performance liquid chromatographic determination: a reference method for free and reversibly bound sulphite in food.
Food and Drug Administration, Division of Food Chemistry and Technology, Washington, DC 20204.
A high-performance liquid chromatographic (HPLC) post-column reactor combination has been developed for the determination of sulphite (free and reversibly bound) in 15 different foods. The foods were treated with a pH 5.1 buffered aqueous 2% formaldehyde solution to convert the labile sulphite to the relatively stable hydroxymethylsulphonate. Reverse-phase ion-pairing HPLC with a post-column detector consisting of an initial reaction with KOH followed by colorimetric reaction with Ellman's reagent buffered at pH 6.3 were used for separation and quantitation. The photometric detector at 412 nm quantitated the strongly absorbing 3-carboxy-4-nitrothiophenolate anion, the product of the sulphite reaction with Ellman's reagent. The recovery at levels of 5-100 ppm as sulphur dioxide was greater than 90% by reverse isotope dilution assay. Repetitive analysis of a single grape juice extract containing 20 ppm SO2 showed a relative standard deviation of 2.2%.
B R Hillery, E R Elkins, C R Warner, D Daniels, T Fazio, P Balazs, M H Bosquez, R Chaddha, S Cordes, K Couture
National Food Processors Association, Washington, DC 20005.
A collaborative study was conducted of the Food and Drug Administration (FDA)-optimized Monier-Williams method for determining sulfites in foods. Twenty-one industry and government laboratories participated in the study, which was jointly sponsored by the National Food Processors Association and FDA. Familiarization samples were shipped to each collaborator. Collaborators were permitted to proceed to the main study only after they demonstrated ability to perform the method to ensure that the study tested the performance of the method itself and not that of the individual laboratories. The study design involved 3 food matrixes (hominy, fruit juice, and protein [seafood]). Each matrix was prepared at 3 sulfite levels--the regulatory level, half the regulatory level, twice the regulatory level--and as a blank. All test samples were analyzed as blind duplicates, which gave each collaborator a total of 24 test portions. Collaborative recoveries gave a reproducibility (among-laboratories) coefficient of variation that ranged from 15.5 to 26.6% for sulfite determined as SO2 by weight in the 3 foods at the 10 ppm level. The optimized Monier-Williams method has been approved interim official first action to replace the AOAC modified Monier-Williams method, 20.123-20.125.
Division of Food Chemistry and Technology, US Food and Drug Administration, Washington, DC 20204.
A survey of sulphite levels in a variety of foods including dried fruit, dried mashed potatoes, shrimp, canned mushrooms and fruit juices has been conducted. The levels found ranged from 0 ppm in orange juice to 3722 ppm as sulphur dioxide in dried fruit. The foods were analysed by the optimized Monier-Williams procedure.
Studies on Inflammation: XIII. Carbohydrate Metabolism, Local Acidosis, and the Cytological Picture in Inflammation.
Elemental Research Branch (HFS-338), US Food and Drug Administration, Washington, DC 20204, USA.
Br concentration in bread for baked bread products was shown to be linearly proportional to the amount of Br added per kg of flour used to make the product. Br concentration in bread can be used to help identify those bread products with the greatest likelihood of containing bromate residues. Instrumental neutron activation analysis was used to determine Br in test portions of bread products from commercial bakeries, homemade bread, flour, and unbaked dough. High performance liquid chromatography was used to determine the bromate residue in selected test portions.
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Flavonoids: chemical properties and analytical methodologies of identification and quantitation in foods and plants.
Eleonora Corradini, Patrizia Foglia, Piero Giansanti, Riccardo Gubbiotti, Roberto Samperi, Aldo Lagana
Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
Flavonoids have been recognised as one of the largest and most widespread groups of plant secondary metabolites, with marked antioxidant properties. The general name flavonoid refers to a class of more than 6500 molecules based upon a 15-carbon skeleton. In this paper a general overview of flavonoids, their classification, structures and analytical methods for their determination is presented.
Anal Bioanal Chem. 2010 Mar 17;: 20232061
Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan.
Hair has been focused on for its usability as an alternative biological specimen to blood and urine for determining drugs of abuse in fields such as forensic and toxicological sciences because hair can be used to elucidate the long intake history of abused drugs compared with blood and urine. Hair analysis consists of several pretreatment steps, such as washing out contaminates from hair, extraction of target compounds from hair, and cleanup for instrumental analysis. Each step includes characteristic and independent features for the class of drugs, e.g., stimulants, narcotics, cannabis, and other medicaments. In this review, recently developed methods to determine drugs of abuse are summarized, and the pretreatment steps as well as the sensitivity and applicability are critically discussed.
Departament de Química Analítica, Facultat de Química, Universitat de Barcelona, c/Martí i Franquès 1-11, 08028, Barcelona, Spain, email@example.com.
In this paper, European food safety legislation is presented, and special attention is devoted to monitoring residues of veterinary drugs in foodstuffs of animal origin. After a short review of the state of the art of analytical methodology for antibiotic residue analysis, the paper focuses on validation of analytical methods, with Decision 657/2002/EC as reference document. Finally, the main issues of the quality control of the analytical data, i.e. analysis of reference materials and participation in proficiency tests, are briefly addressed.
Department of Environmental Toxicology, University of California at Davis, One Shields Avenue, Davis, California 95616, USA. firstname.lastname@example.org
An analytical method was developed for the determination of eleven agrochemicals [abamectin (as B1a), bifenazate, bifenthrin, carfentrazone-ethyl, cymoxanil, hexythiazox, imidacloprid, mefenoxam, pymetrozine, quinoxyfen, and trifloxystrobin] in dried hops. The method utilized polymeric and NH2 solid phase extraction (SPE) column cleanups and liquid chromatography with mass spectrometry (LC-MS/MS). Method validation and concurrent recoveries from untreated dried hops ranged from 71 to 126% for all compounds over three levels of fortification (0.10, 1.0, and 10.0 ppm). Commercially grown hop samples collected from several field sites had detectable residues of bifenazate, bifenthrin, hexythiazox, and quinoxyfen. The control sample used was free of contamination below the 0.050 ppm level for all agrochemicals of interest. The limit of quantitation and limit of detection for all compounds were 0.10 and 0.050 ppm, respectively.
Analysis of flonicamid and its metabolites in dried hops by liquid chromatography-tandem mass spectrometry.
Department of Environmental Toxicology, University of California at Davis, One Shields Avenue, Davis, California 95616, USA. email@example.com
An analytical method was developed for the determination of the neo-nicotinoid insecticide flonicamid ( N-cyanomethyl-4-trifluoromethylnicotinamide) and its metabolites N-(4-trifluoronicotinoyl) glycine (TFNG), 4-trifluoronicotinic acid (TFNA), and 4-trifluoromethylnicotinamide (TFNA-AM) in dried hops. The method utilized C18 and polymeric solid phase extraction (SPE) column cleanups, liquid-liquid partitioning, and liquid chromatography (LC) with mass spectrometry (MS/MS). Method validation and concurrent recoveries from untreated dried hops ranged from 66 to 119% for all compounds over five levels of fortification (0.005, 0.02, 0.2, 2.0, and 4.0 ppm). Flonicamid-treated hop samples collected from three field sites had the following residues: flonicamid levels of 0.561-2.85 ppm, TFNA levels of 0.302-0.470 ppm, TFNA-AM levels of 0.038-0.177 ppm, and TFNG levels of 0.098-0.204 ppm. Untreated hop samples from all fields had residues <0.005 ppm for flonicamid, TFNA, TFNA-AM, and TFNG. The limit of quantitation and limit of detection for all compounds were 0.005 and 0.0025 ppm, respectively.
University of Zaragoza, Department of Animal Production and Food Science, Veterinary Faculty, C/Miguel Servet 177, 50013 Zaragoza, Spain.
The application of high resolution gas chromatography in combination with low resolution mass spectrometry with electron ionization and MS/MS detection (HRGC-MS/MS) is tested for its use in the analysis of PCDD/Fs in infant formulas. Development of the analytical method was based upon EPA directrices and international recommendations. Calibration linearity was tested and average relative response for any native and labelled compound over the five-point calibration range below 14% was found. The precision and accuracy of the proposed analytical procedure are also presented. Results obtained are in agreement with EPA criteria. The method is applied to the analysis of a number of initial and follow-on milk based infant formulas. In general, HRGC-MS/MS constitutes an interesting method for the analysis of dioxins in such matrices.
Chromatography Laboratory, Research Centre for Biomolecules, CIBIMOL, CENIVAM, Industrial University of Santander, Carrera 27, Calle 9, Bucaramanga, Colombia.
Recent advances in the development of analytical methods based on headspace/solid-phase micro-extraction (HS/SPME) of natural aroma compounds are reviewed, with special emphasis on increasing reproducibility. Representative examples of applications of HS/SPME to the determination of components at trace levels, strategies for fiber selection, and improvement of SPME sampling conditions are presented. Examples of applications to quality control and sample classification, based on aroma profiling were selected to highlight the use of multivariate statistical methods.
Department of Physical Chemistry, Faculty of Pharmacy, Charles University, 501 65 Hradec Králové, Czechoslovakia.
The analytical applications of the hydrolysis of 1,4-benzodiazepines to the corresponding benzophenone derivatives are reviewed according to the analytical methods used for their final determination. The scope and limitations of the individual methods for the hydrolysis products are discussed: Colour reactions, photometry, fluorimetry, thin-layer chromatography, gas chromatography and high-performance liquid chromatography. Published data on the kinetic parameters and mechanisms are summarized in an attempt to explain the problems involved in exploiting this reaction for analytical applications.
Potentiality of gas chromatography-triple quadrupole mass spectrometry in vanguard and rearguard methods of pesticide residues in vegetables.
Department of Analytical Chemistry, University of Almería, 04071 Almería, Spain.
A new analytical strategy for the screening and confirmation/quantification of multiclass pesticide residues in vegetables has been established and validated. No complicated sample preparation was needed, but only a simple and rapid extraction using ethyl acetate and sodium sulfate, which required no cleanup. The approach is based on the use of the triple quadrupole (QqQ) mass spectrometry (MS) as detection system in gas chromatography (GC). In a first step, a GC-QqQ-MS screening method, which monitors only one MS/MS transition by compound, allows the identification of approximately 130 pesticides in 11.6 min. In this way, the differentiation between negative and potentially nonnegative samples is carried out. In the second step, the nonnegative samples are reanalyzed by the GC-QqQ-MS confirmation/quantification method, which monitors two or three MS/MS transitions by compound. Confirmation of pesticides was based on the comparison of intensity ratios for the main ions in samples with those obtained on the same day from the standard in a matrix containing the pesticides at a preestablished concentration level. Quantification of the identified and confirmed pesticides was based on the addition standard method, which avoids matrix effect. The proposed analytical strategy allowed a reliable identification and confirmation of the target pesticides at trace levels, reducing analysis time and increasing sample throughput in routine analytical laboratories.
Validation of an analytical methodology for determination of oxytetracycline and tetracycline residues in honey by HPLC with fluorescence detection.
Group of Bromatology, Centre of Pharmaceutical Studies, Faculty of Pharmacy, University of Coimbra, 3000 Coimbra, Portugal. firstname.lastname@example.org
An analytical method for the determination of OTC and TC residues in honey was developed. Sample treatment involves an extraction in EDTA-McIlvaine buffer, followed by a solid-phase cleanup step. With regard to the cleanup procedure, different SPE cartridges were evaluated and the results presented. The method was validated according to the guidelines laid down by the 2002/657/EC European Decision parameters: decision limit (Cc alpha) and detection capability (CC beta) were 20 and 21 microg/Kg and 49 and 50 microg/Kg for OTC and TC, respectively, and recoveries of OTC and TC from spiked samples, at three fortification levels, were higher than 87% for both compounds. The analytical method was applied to 57 honey samples.