bluuebunny/crossref_metadata_2025 huggingface dataset:
Multitest System for Biochemical Identification of Salmonella, Escherichia coli, and Other Enterobacteriaceae Isolated from Foods: Collaborative Study
Authors: Keelan Susan L , Flowers Russell S , Robison Barbara J
Published: February 2020

Nine laboratories evaluated the ability of the MICRO-ID test system to correctly identify members of the Enterobacteriaceae. A total of 78 isolates representing 11 genera of enterics that had been previously isolated from foods were used in the collaborative study. The collaborators streaked each isolate on plate count agar and incubated the plates overnight at 35°C to check purity of the isolates. Then they proceeded with the method in which an isolated colony is transferred to a plate count agar slant and is incubated 18-24 h at 35°C. Growth from the slant is emulsified in 3.5 mL physiological saline to a density comparable to a McFarland No. 2 tube and is then used to inoculate the test (MICRO-ID) strip. The strip is incubated 4 h at 35°C and the reactions are read and recorded. Isolates are identified by using an octal code and the test kit manual. The system correctly identified 98.8% of the Salmonella isolates, 97.7% of the E. coli isolates, and 84.6% of the other 9 enteric genera tested. The system has been approved interim official first action as an alternative to conventional biochemical tests (1) for presumptive generic identification of foodborne Salmonella and for screening and elimination of non-Salmonella isolates; (2) for identification of E. coli from foods; and (3) for presumptive generic identification of other Enterobacteriaceae isolated from foods.
Gas Chromatographic Method for Determination of Fenitrothion in Fenitrothion Technical and in Formulated Products: Collaborative Study
Authors: Mount Dwight L , Churchill Frederick C
Published: February 2020

A gas chromatographic (GC) method for determination of fenitrothion in fenitrothion technical and formulated products has been subjected to a collaborative study with 7 participating laboratories. Formulations are extracted with chloroform containing dibutyl sebacate as an internal standard and are analyzed by gas chromatography using an OV-210 column. Collaborators were furnished matched pairs of technical product and water-dispersible powder and emulsifiable concentrate formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 0.54, 1.00, and 1.56%, respectively, for technical fenitrothion, water-dispersible powders, and emulsifiable concentrates. The method has been approved interim official first action as an alternative to the present official first action AOAC method 6.A19-6.A24, which uses a polyphenyl ether, 6 ring (PPE-6R) column packing and fluoranthene as internal standard.
Application of ^-Nuclear Magnetic Resonance Spectroscopic Method for Quinidine to
Simultaneous Determination of Quinidine and Dihydroquinidine in Quinidine Sulfate Tablets
Authors: Hanna George M , Lau-Cam Cesar A
Published: February 2020

Based on the structural differences between quinidine and dihydroquinidine, a 'H-nuclear magnetic resonance spectroscopic method previously reported for quinidine drug substance was modified and shown to be applicable to the quantitative determination of both compounds in quinidine sulfate tablets. Deuterated chloroform was used as the solvent and hexamethylcyclotrisiloxane served as an internal standard. The average recovery and standard deviation of quinidine sulfate (calculated as the sum of quinidine sulfate plus dihydroquinidine sulfate) from synthetic formulations was 98.94 ± 0.43% (n = 10). Five lots of 200 mg tablets of quinidine sulfate from one commercial source were found to contain from 92.9 to 95.8% quinidine sulfate, and from 1.1 to 7.0% dihydroquinidine sulfate
Reverse-Phase Liquid Chromatographic Analysis of Cephalosporins
Authors: Ting Susan
Published: February 2020

A simple and rapid reverse-phase liquid chromatographic method was developed for the qualitative and quantitative analysis of 13 cephalosporin compounds. A mixture of cefaclor, cefadroxil, cefamandole nafate, cefamandole sodium, cefazolin, cefoperazone, cefotaxime, cefoxitin, ceftizoxime, cephalothin, cephalexin, cephapirin, and cephradine was resolved into its components in raw material and dosage form samples by using a Clg column, a methanol-water-acetic acid (30 + 70 + 0.1) mobile phase, and a UV detector set at 254 nm. The proposed method is suited both for the determination of cephalosporins in a wide variety of commercial dosage forms and for the investigation of related compounds and other impurities in samples of 7 of the cephalosporins
Spectrofluorometric Assay of Thiamine Hydrochloride in Injections and Multivitamin
Preparations
Authors: Mohamed Abdel-Maboud I , Hussein Samiha A , El-Shabouri Salwa R
Published: February 2020

A spectrofluorometric method is described for the determination of thiamine hydrochloride. The method is based on formation of a fluorescent product by oxidation of thiamine HC1 with 2,3,5,6-tetrabromo- l,4-benzoquinone in aqueous acetonitrile solution. The reaction product is stable for at least 6 h and shows excitation and emission maxima around 355 and 420 nm, respectively. The method is highly selective for thiamine HC1 in the presence of other B vitamins. Thiamine HC1 can be determined at concentrations as low as 20-160 ng/ mL of the final solutions. When the method was applied to the determination of thiamine HC1 added to some commercially available multivitamin preparations, recoveries were 98.78-99.98%
FDA Total Diet Study, April 1982-April 1984, Dietary Intakes of Pesticides, Selected
Elements, and Other Chemicals
Authors: Gunderson Ellis L
Published: February 2020

The U.S. Food and Drug Administration conducts the Total Diet Study to determine dietary intakes of selected pesticides, industrial chemicals, and elements (including radionuclides). The current study, which reflects significant redesign implemented in April 1982, involves retail purchase of foods representative of the "total diet" of the U.S. population, preparation for "table-ready" consumption, and individual analyses of 234 items depicting the diets of 8 population groups. The dietary revision was based on 2 nationwide food consumption surveys. The data presented represent 8 food collections (also termed "market baskets") in regional metropolitan areas during the 2-year period. Dietary intakes of over 100 analytes are presented for the 8 population groups, which range from infants to elderly adults. Intakes of selected population groups are compared with representative previous findings. As in the past, average daily intakes are within acceptable limits
Class Definition and Mixture Class Definition by Means of Construction of Convex Hull Boundaries: Application to Analysis for Animal Fat Adulteration
Authors: Thielemans Anne , Brabander Hubert De , Massart Desire L
Published: February 2020

A visual classification technique based on the construction of convex hull boundaries in combination with a principal component analysis is described. This combined technique was evaluated in the situation in which a distinction has to be made between 2 pure animal fat classes and the corresponding mixture class. In the first instance, a principal component analysis is carried out to ensure the 2-dimensional and thus visual aspect of the technique. Convex hulls are then constructed in the 2-dimensional principal component plane to delimit the boundaries of the different classes to be defined. The effectiveness of the constructed hull boundaries in the definition of class-membership was investigated by means of the classification of different simulated test samples. The results show that, at least for the tested applications, the technique is valid, although some false positive classifications occur. The detection of outliers especially seemed to pose problems. Therefore, some propositions are made of how to refine the developed hull technique to enhance the classification results.
Methods of Analysis for Toxic Elements in Food Products. 3. Limit of Determination of Methods for Assuring Safety
Authors: Skurikhin Igor M
Published: February 2020

To evaluate the suitability of the analytical methods used in determining food safety, a new metrological characteristic "MQS" is suggested. MQS is defined as the absolute minimum quantity in micrograms of a substance that can be determined in a test solution (solubilized test portion). MQS accounts for 2 factors: (a) the necessity for a reliable determination of ML (maximum permitted level, i.e., regulatory tolerance), and (b) the optimum quantity of test portion of a food product to be analyzed, and thus assists in evaluating the suitability of a method to assure food safety. The MQS of 8 toxic elements in any food are As, 3; Cd, 0.5; Cu, 20; Fe, 50; Hg, 0.2; Pb, 4; Sn, 200; Zn, 100fig. To characterize the applicability of any given method, the specific minimum limit of determination, MQSM, must be established for each method. The method in question may be used to control food safety only if MQSM is less than MQS. MQSM values are given for the common polarographic and colorimetric methods for determining these elements.
Immunodiffusion Screening Method for Detection of Motile Salmonella in Foods: Collaborative Study
Authors: Flowers Russell S , Klatt Mary Joan
Published: February 2020

A collaborative study was performed to validate the performance of the 1-2 TEST® for detection of motile salmonellae in foods. Detection is based on observation of an immobilized band of cells. Twentythree laboratories participated in the study. The 1-2 TEST (immunodiffusion test) was compared with the standard culture procedure (BAM/AOAC; FDA Bacteriological Analytical Manual) for detection of Salmonella in 6 food types: ground black pepper, soy flour, dried whole egg, milk chocolate, nonfat dry milk, and raw deboned turkey. Uninoculated and inoculated samples were included in each food group analyzed. After the tests on the 6 foods were completed, analysis of the data for turkey and soy flour showed that certain collaborators obtained data inconsistent with the data from the majority of collaborators. No specific method deviations to account for the inconsistencies were reported by those collaborators, so the collaborative testing of these 2 foods was repeated. Analysis of data for pepper, chocolate, nonfat dry milk, dried whole egg, and the second set of soy flour and turkey indicated 96.1% agreement between the BAM/AOAC and immunodiffusion test methods. The false negative rates for the immunodiffusion test and BAM/AOAC methods were 3.6 and 1.7%, respectively. There was no significant difference in the productivity of the immunodiffusion test and BAM/AOAC method at the 5% level for any of the 6 foods. The immunodiffusion screening method has been approved official first action for detection of motile Salmonella in food
Purification of Cyclopiazonic Acid by Liquid Chromatography
Authors: Peterson Robert E , Shannon Gail M , Shotwell Odette L
Published: February 2020

A purification procedure for cyclopiazonic acid has been developed, using sequential preparative and semi-preparative liquid chromatography. Crude cyclopiazonic acid (324 mg) was extracted from a 1 L fermentation medium with chloroform-methanol (80 + 20), dried, dissolved in chloroform, and chromatographed on an oxalic acid/ silica preparative column with chloroform-methanol (99 + 1) as the eluant. A semi-preparative oxalic acid/silica column and chloroform- methanol (99.5 + 0.5) were then used for rechromatography of the partially purified cyclopiazonic acid. This second chromatographic treatment yielded fractions from which cyclopiazonic acid was readily crystallized (106.7 mg; 33% recovery). Analytical chromatography was developed using an amino column in an ion-exchange mode, with a methanol-phosphate buffer eluant. Response was linear from 10 to 800 μg/injection of standard solutions. Cyclopiazonic acid chemically binds sodium from soda-lime vials.
Liquid Chromatographic Determination of Aflatoxins, Ochratoxin A, and Zearalenone in Grains, Oilseeds, and Animal Feeds by Post-Column Derivatization and On-Line Sample Cleanup
Authors: Chamkasem Narong , Cobb William Y , Latimer George W , Salinas C , Clement B A
Published: February 2020

A liquid chromatographic method using on-line sample cleanup, reverse flow analytical column loading, gradient elution, and postcolumn derivatization with iodine permits direct, rapid determination of aflatoxins B1, B2, G1, and G2, as well as ochratoxin A and zearalenone. Limits of quantitation are 5 ppb for the aflatoxins and ochratoxin A and 30 ppb for zearalenone. This procedure performs well as a multimycotoxin screen for cereal grains and oilseeds, with more limited success in complete animal feeds.
Determination of 2,3?7,8-Tetrachlorodibenzo-p-Dioxin in Fish, Using Electron Capture Gas Chromatography with Confirmation by Mass Spectrometry: Interlaboratory Study
Authors: Fehringer Norbert V , Walters Stephen M , Niemann Richard A
Published: February 2020

An interlaboratory study of the determination of 2,3,7,8-tetrachlorodibenzo- p-dioxin (2,3,7,8-TCDD) in fish was conducted by 6 analysts in 4 laboratories using high resolution gas chromatography with electron capture detection (HRGC-EC) for quantitative screening analysis. Samples consisted of 3 Great Lakes channel catfish homogenates containing different levels of bioincurred 2,3,7,8-TCDD; 1 of these was prepared in duplicate and another was prepared both with and without standard 2,3,7,8-TCDD fortification for a total of 5 samples per set. All methods used included addition of 1,3,7,8-TCDD surrogate (to correct for procedural losses) followed by ethanolic KOH digestion and hexane extraction. Certain cleanup steps used, including sulfuric acid washing and multidimensional column liquid chromatographic procedures, varied among laboratories. Mean HRGC-EC results for the bioincurred residues were 56.6, 25.2, and 7.7 pg/g (ppt) with corresponding relative standard deviations (RSDs) of 9.1,18.6, and 53.2%. Average determination of standard 2,3,7,8- TCDD from the fortified sample (corrected for surrogate recoveries averaging 74.6%) was 106% of the added amount (30.9 pg/g) with 11.0% RSD. HRGC-multiple ion detection mass spectrometry (MS), monitoring 12 ions, was used for confirmation. With the exception of several results from 1 analyst, HRGC-MS and HRGC-EC quantitations were in good agreement. All but 1 result reported met all of the MS ide ntity criteria.
Sampling in the Analytical Scheme
Authors: Garfield Frederick M
Published: February 2020

The general principles of sampling in the analytical scheme, sampling definitions, and sampling planning are considered. Statistical considerations are stressed with attention to sampling by attributes and variables and the use of sampling control charts. Sampling techniques, records and chain-of-custody procedures, sample handling, laboratory sampling, and sample preparation for analysis, as well as reasons and causes of sampling errors, are discussed.
Simple, Rapid, and Portable Chromatographic Tetrazolium Reduction Method for Detection of Potassium Cyanide in Medicinal Drugs and Confectionery
Authors: Bhagyalakshmi Kamasala , Kumar Nanguneri V Nanda
Published: February 2020

A simple, rapid, and portable paper chromatographic method for detection of potassium cyanide in medicinal drugs and a few confectionery samples is described. Potassium cyanide is extracted in methanol and concentrated. Acetone-water-1.5% EDTA (4 + 5.5 + 0.5) mixture is used as the solvent system for paper chromatography. The KCN chromatograms appear as pink spots on paper due to reduction of the chromogenic salt 2-(4-iodophenyl)-3-(4-nitrophenyl)-5- phenyl tetrazolium chloride; phenazonium methosulfate is a catalyst. Microgram amounts of KCN can be separated and detected in the laboratory or the marketplace because of the simplicity of the method.
Liquid Chromatographic Determination of Miconazole Nitrate in Creams and Suppositories
Authors: Tyler Theodore A , Genzale Judith A
Published: February 2020

A rapid method has been developed for the determination of miconazole nitrate in creams and suppositories. The sample is dissolved in ethanol, diluted in acetonitrile-water (1 + 1), and injected onto a C18 column. The mobile phase consists of 55% acetonitrile, a triethylammonium phosphate buffer, and an ion-pairing agent. The total run time is less than 4 min, and the active ingredient is determined using absorbance detection at 214 nm. The mean recovery of miconazole from spiked placebo samples was 99.7 ± 0.7% for the cream samples at the 2% level and 98.8 ± 0.3% for the suppository samples at the 4% level.
Improved Turbidimetric Assay of Tylosin in Premix and Animal Feeds Not Containing Urea
Authors: Coleman Mark R
Published: February 2020

A turbidimetric method is described for the determination of tylosin in premix and animal feeds not containing urea. This method includes several modifications of existing tylosin turbidimetric and AOAC plate assays to remove interferences from the feed, to concentrate low levels of tylosin, and to reduce the variability of the assay results. An acidic alumina column cleanup step has been incorporated into the method to remove interferences from feed ingredients. A disposable C18 column was used to concentrate the tylosin from low-level feeds, and the use of a larger analytical sample size has decreased the variability of the assay results. Average recoveries of tylosin added to chicken and swine rations were 98 and 101%, respectively.
Determination of Iodine Value by Bromine/Instrumental Neutron Activation Analysis
Authors: Iskander Felib Y
Published: February 2020

A new microanalytical method has been developed to measure iodine value (IV) of oils and fats. Bromine vapor was used to saturate the ethylenic double bonds, and reacted bromine was determined by instrumental neutron activation analysis. The method was applied to measure the iodine values of 7 commercially available vegetable oils: almond oil, sunflower oil, peanut oil, soy oil, sesame oil, corn oil, and olive oil. No significant difference was observed between the iodine value determined by the proposed method and that determined by an officially approved (Hübl) method. Bromine measurements can be performed up to 150 days after bromination with no significant variation in iodine value; thus, availability of an irradiation facility on the premises is not a limitation. No corrosive and toxic reagents are required, and the method is faster than the official methods. The method is also applicable to measuring iodine values of free or esterified fatty acids.
Determination of Fluoroacetate in Biological Matrixes as the Dodecyl Ester
Authors: Burke Daniel G , Lew Dennis K T , Cominos Xenophon
Published: February 2020

A new method for the quantitative determination of fluoroacetate in biological samples was applied to a number of avian samples. Fluoroacetate is isolated as its potassium salt by ion-exchange chromatography and directly converted to its dodecyl ester, using a novel derivatization procedure. The ester is quantified by capillary gas chromatography with a flame ionization detector for the range 1.0-10.0 μg/ g and by selected ion monitoring GC/mass spectrometry for the range 0.01-1.00 μg/g. Recoveries from 1 g chicken muscle were about 80%. The method was applied to the determination of fluoroacetate in the crop, stomach, liver, heart, intestine, and breast muscle of 5 Zebra finches (Peophila guttata) that had been fed millet containing 9 μg/g of sodium fluoroacetate. Despite a wide variation in dose, the levels in organs and tissues were approximately 1 μg/g except for heart tissue which was about 2 μg/g. The presence of interfering peaks at low levels necessitated the use of selected ion monitoring GC/MS when sample weights were less than 1 g or when levels were less than 1 μg/ g. Samples can be analyzed within hours of receipt; therefore, the method is suitable for routine use in a diagnostic laboratory.
Rapid Gas Chromatographic Method Using Nitrogen-Phosphorus Detection for N-Nitrosodimethylamine in 2,4-D and MCPA Herbicide Formulations
Authors: Scharfe Ronald R , Mclenaghan Charles C
Published: February 2020

A simple and rapid analytical method has been developed for the determination of JV-nitrosodimethylamine (NDMA) in amine salts of phenoxy herbicide formulations of 2,4-D and MCPA, plus mixtures of these with mecoprop and dicamba amine salts. Sample preparation consists of direct extraction using pre-packed disposable extraction tubes eluted with dichloromethane followed by cleanup on a disposable silica gel mini-column using ethyl acetate as eluting solvent. Samples are injected on-column for gas chromatography with a Megabore fused silica column; the NDMA is measured by a thermionic specific detector (TSD) that is selective for nitrogen-phosphorus (NP). A detection limit of 0.1 μg/mL was easily attainable without any concentration step because the solvent volume is minimal. TSD and thermal energy analyzer (TEA) results have been compared and confirmed by gas chromatography/mass spectrometry. Recovery studies were performed as well as a reproducibility study on one of the 2,4-D formulations.
Effect of Commercial Processing on Pesticide Residues in Selected Fruits and Vegetables
Authors: Elkins Edgar R
Published: February 2020

Commercial food processing operations such as washing, blanching, and cooking remove major portions of the pesticide residues that are currently permitted on the raw agricultural crop. These unit operations are reviewed for selected products, along with degree of residue removal at each step. For example, washing plus peeling removes 99% of carbaryl and malathion residues from tomatoes. Washing removes 83% of benomyl residue from tomatoes and further processing reduces the residue by 98% in tomato puree and catsup. Even in the most concentrated fraction from tomatoes (tomato paste), residues were below the initial level in the raw product.
Liquid Chromatographic-Electrochemical Detection Screening Procedure for Six Nitro-Containing Drugs in Chicken Tissues at Low ppb Level
Authors: Parks Owen W
Published: February 2020

A screening procedure is described for the detection of furazolidone, nitrofurazone, aklomide, zoalene, nitromide, and sulfanitran residues in a single extract of chicken liver, breast, or thigh muscle at the low ppb level. The method includes extraction of tissue with chloroformethyl acetate-dimethyl sulfoxide (50 + 50 + 0.8), adsorption on neutral alumina, and subsequent elution of the residues with pH 6.0 phosphate buffer-methanol (1 + 1). Eluants are separated on a 25 cm, 5 fim Cj8 column with pH 6.0 phosphate buffer-methanol (57.5 + 42.5) as mobile phase. The drugs are detected with an electrochemical detector in the reductive mode at -0.8 V. Mean recoveries from all tissues ranged from 76.5% for nitrofurazone to 97.1% for zoalene.
Determination of iV-Methylcarbamate Pesticides in Liver by Liquid Chromatography
Authors: Ali Sher M
Published: February 2020

A liquid chromatographic (LC) method using a 2-step purification technique for the simultaneous determination of 10 carbamates in bovine, swine, and duck livers has been developed. Carbamates are extracted from liver samples with methylene chloride. After evaporation, the residues from the extract are dissolved in methylene chloride- cyclohexane (1 + 1) and cleaned up by gel permeation chromatography. The eluate containing carbamate residues is evaporated to dryness, reconstituted in methylene chloride, further purified by passing it through an aminopropyl Bond Elut extraction cartridge, and analyzed by liquid chromatography using post-column derivatization with orthophthalaldehyde and fluorescence detection. Excitation and emission are set at 340 and 418 nm, respectively. Liver samples for beef, pork, and duck were fortified with 5, 10, and 20 ppb of mixed carbamate standards. The average of 10 recoveries of 10 carbamates at all 3 levels of fortification was greater than 80% with coefficients of variation less than 17%.
Comparison Evaluation of Liquid Chromatographic and Bioassay Methods of Analysis for Determination of Paralytic Shellfish Poisons in Shellfish Tissues
Authors: Salter Julia E , Timperi Ralph J , Hennigan Laura J , Sefton Lynda , Reece Hilary
Published: February 2020

A liquid chromatographic (LC) method was compared with the AOAC mouse bioassay method (18.086-18.092) for determination of paralytic shellfish toxins in shellfish tissues. Shellfish samples were collected from Massachusetts coastal waters as part of a state surveillance program, and extracts of shellfish meat were analyzed for toxins by using both analytical methods. Overall correlation of the LC and bioassay methods is good (r = 0.943), but for samples with toxicities < 100 jug saxitoxin/100 g shellfish meat, the correlation is significantly less (r = 0.531). Limits of detection are 10 fig saxitoxin/ 100 g shellfish meat and 40 fig saxitoxin/100 g shellfish meat for the LC and bioassay methods, respectively. Analytical capacity of the LC method is limited to 12 samples/person-day compared with 30 samples/ person-day for the bioassay. Sampling capacity of the LC method could be increased by using a fluorescence detector with a wider response range, which would eliminate the need for dilution of concentrated samples.
Net Contents of Packaged Beer: Summary of Collaborative Study
Authors: Gales Peter W
Published: February 2020

The net contents of packaged food and beverage products is a matter of regulatory concern. In the case of alcoholic beverages, net contents are regulated by various federal, state, and local agencies. With such a variety of controlling agencies, standardized and uniform methods are essential to avoid undue confusion. Collaborative studies were initiated within the American Society of Brewing Chemists in 1985 to determine the most appropriate methods for the determination of net contents of packaged beer. The work was completed in 1987. After collaborative testing of 5 methods over the 2-year period (ASBC JOURNAL (1987) 45, 114-117), 3 of the methods were found suitable: (1) total contents of cans of known tare weight; (2) total contents of bottles and cans by calculation from measured net weight; (J) deliverable contents of bottles and cans from measured net weight. These methods, which are recommended for adoption by AOAC, have been approved interim official first action.
Determination of Citrus Red No. 2 in Orange Peel by Liquid Chromatography Cynthia Hope And Russell Connors
Authors: Hope Cynthia , Connors Russell
Published: February 2020

A liquid chromatographic (LC) method is described for determina-tion of the color additive Citrus Red No. 2 in orange peel. The dye is extracted with petroleum ether using a Soxhlet-type apparatus. The extract is evaporated almost to dryness and the residue is dissolved in acetonitrile. Liquid chromatographic analysis is carried out, isocrati-cally, on an Ultrasphere ODS C18 column with acetonitrile-water (90 + 10) as mobile phase and detection at 504 nm. Recoveries from dried orange peel fortified at 3 levels ranged from 93 to 103%; recoveries from fresh orange peel ranged from 87 to 102%.
Comparison of Two Methods for Determination of Total Solids Content of Milk:
Collaborative Study
Authors: Clark Jenny L , Barbano David M , Dunham Chapman E
Published: February 2020

Ten laboratories analyzed 9 pairs of blind duplicate raw milk samples for total solids. A direct forced air oven method (4 h at 100°C) and a modification of the AOAC predry method (16.032) were used. Preliminary evaluation of the modified AOAC method indicated that blank determinations were necessary. Total solids content ranged from 12.0 to 14.6%. Average repeatability standard deviations (sr) of the direct forced air oven and modified AOAC methods were 0.019 and 0.017, respectively. Average reproducibility standard deviations (SR) of the direct forced air oven and the modified AOAC methods were 0.042 and 0.047, respectively. Average repeatability relative standard deviations (RSDr) for the direct forced air oven and the modified AOAC methods were 0.149 and 0.136%, respectively; average reproducibility relative standard deviations (RSDR) were 0.327 and 0.370%, respectively. Mean repeatability values (r) and reproducibility values (R) were 0,054 and 0.118 for the direct forced air oven method and 0.049 and 6.133 for the modified AOAC method, respectively. The mean test result of the direct forced air oven method (12.7293%) was comparable to that for the modified AOAC method (12.7273%). The modification of AOAC method 16.032 and the direct forced air oven method have been approved interim official first action.
Determination of Methyl Bromide in Foods by Headspace Capillary Gas Chromatography with Electron Capture Detection
Authors: Page Denis B , Avon Richard J
Published: February 2020

Methyl bromide (MB, bromomethane) is determined in a variety of foods by headspace capillary gas chromatography with electron capture detection. The comminuted food sample as an aqueous sodium sulfate slurry is equilibrated with stirring for 1 h at room temperature before a 1 mL headspace aliquot is removed and injected using a modified on-column syringe needle. Methyl bromide is cryogenically focussed at —60°C and then eluted by temperature programming. The procedure requires blending of soft samples, e.g. raisins, prunes, or oranges, and ultrasonic homogenization of hard samples, e.jv wheat, cocoa beans, corn, or nuts, with portions of water and ice so the final temperature of the food-water slurry is < 1°C. A 20 g aliquot (4 g food) is then added to a cold headspace vial containing 4 g sodium sulfate. Losses of MB during a 3.5 min ultrasonic homogenization of wheat were 11% at 0.95 ppb and 4.4% at 4.8 ppb. For flour, cocoa, and finely divided spices, which do not require blending, 4 g is added to the cold headspace vial containing 16 mL cold water and 4 g sodium sulfate. Studies show that comminution of wheat or peanuts must be carried out to release MB trapped within the food so the headspace equilibrium can be attained in 1 h as well as to obtain homogenous samples and representative sampling. No interferences were noted with the above foods or with many grain-based baking mixes analyzed. Detection limits were shown to be generally dependent on the approximate lipid content of the food and ranged from 0.15 to 0.65 ppb (5% full scale deflection). Repeatability CVs for spiked or incurred MB in flour, wheat, and parmesan cheese at 0.60-96 ppb were < 6.8%.
Chemical Characterization and Bioavailability of Phosphorus in Water-Insoluble Fractions of Three Mono-Ammonium Phosphate Fertilizers
Authors: Sikora F J , Dillard E F , Copeland J P , Mullins G L
Published: February 2020

Elemental impurities in mono-ammonium phosphate (MAP) fertilizers, such as Fe, Al, Ca, Mg, and F, result in compounds other than NH4H2PO4. The phosphorus availability of the impurity compounds was determined in 3 commercial MAP fertilizers produced from North Carolina, Florida, and Idaho phosphate rocks. Soluble compounds, including NH4H2PO4, were washed out of the fertilizers, and the water-insoluble fraction was collected. The North Carolina, Florida, and Idaho MAP fertilizers contained 13, 16, and 17% waterinsoluble fractions, respectively. Availability of phosphorus in each MAP fertilizer and water-insoluble fraction was determined in a greenhouse pot study using sorghum-sudangrass {Sorghum bicolor) as the test crop. There were no differences in dry matter weights or phosphorus uptake between reagent grade MAP and each MAP fertilizer. Lower dry matter weights and phosphorus uptake were produced from the water-insoluble North Carolina, Florida, and Idaho fractions (NC > FL > ID). Chemical analysis and characterization with optical microscopy, infrared spectroscopy, and X-ray diffractometry indicated 77.3,73.8, and 73.6% NH4H2PO4 in the North Carolina, Florida, and Idaho MAP fertilizers, respectively. MgAl(NH4)2H(P04)2F2, AINH4HPO4F2, and FeNH4(HP04)2 were identified as water-insoluble phosphorus compounds. There was a significant negative correlation between the percent phosphorus present as MgAl(NH4)2H(P04)2F2 and the phosphorus availability. Increased crystallinity of the various water-insoluble compounds also contributed to reduced phosphorus availability.
Hydrophobic Grid Membrane Filter/MUG Method for Total Coliform and E s c h e r ic h ia c o li Enumeration in Foods: Collaborative Study
Authors: Entis Phyllis
Published: February 2020

Twenty-four laboratories participated in a collaborative study to validate a hydrophobic grid membrane filter (HGMF) method incorporating the use of 4-methylumbelliferyl-/?-D-glucuronide (MUG) for enumeration of total coliform and Escherichia coli bacteria in foods by comparing its performance against the AOAC 3-tube MPN method (46.013-46.016). Raw milk, raw ground poultry, whole egg powder, cheese powder, and ground black pepper were included in the study. The total coliform methods did not differ significantly, except that the 3-tube method detected a significantly higher level of total coliforms than did the HGMF method in the ground black pepper. Conversely, the HGMF/MUG E. coli method detected significantly higher numbers of E. coli present in the egg powder, cheese powder, and ground black pepper samples, while not differing significantly from the 3-tube method for the raw milk and raw ground poultry samples. The overall confirmation rate of MUG-positive colonies isolated using the HGMF method was 99.5%. The hydrophobic grid membrane filter/MUG method has been adopted official first action as an additional method to AOAC official final action method 46.030-46.034.
Determination of Aflatoxin Concentrations in Peanut Butter by Enzyme-Linked Immunosorbent Assay (ELISA): Study of Three Commercial ELISA Kits
Authors: Patey Alan L , Sharman Matthew , Wood Roger , Gilbert John
Published: February 2020

Sixteen United Kingdom analytical laboratories participated in an evaluation of 3 commercially available enzyme-linked immunosorbent assay (ELISA) kits for analysis of aflatoxin in peanut butter. Each laboratory was sent 3 sets of 10 randomly numbered samples of peanut butter. Each set consisted of 5 pairs of undisclosed duplicates. Four of the sets of duplicates were naturally contaminated butters with “target” aflatoxin values (estimated by liquid chromatography) between 8 and 81 fig/kg. The fifth pair was a blank peanut butter containing approximately 3 fig/kg of total aflatoxins. A statistical treatment of the results of the study is presented, together with discussion of the relative merits of the different kits.
Determination of Linuron in Potatoes Using Capillary Column Gas Chromatography/Mass Spectrometry
Authors: Mattern Gregory C , Singer George M , Louis Judy , Robson Mark , Rosen Joseph D
Published: February 2020

A convenient method for the determination of the JV-methyl,iVmethoxy- phenylurea herbicide (linuron) in potatoes has been developed. The herbicide is extracted from potatoes using a slightly modifled Luke multiresidue procedure. The extract is analyzed directly by gas chromatography with cold on-column injection, using an ion trap mass spectrometer in the chemical ionization mode as the detector. Quantitation is performed using p-bromonitrobenzene as the internal standard. The limit of detection is 0.1 ppm. Recoveries of linuron in potatoes averaged 112 ± 6% at the 0.5 ppm level, and 110 ± 2% at the 0.2 ppm level. No linuron residues were found in 25 potato samples that were analyzed by this method. Two other iV-methyl,iV-methoxyphenylurea herbicides, metobromuron and chlorbromuron, are also sufficiently stable to be determined by this method, but the N,Ndialkyl- phenylurea herbicides neburon, diuron, and monuron are too thermally unstable and degrade in the gas chromatograph.
Enzymatic Hydrolysis of Biological and Environmental Samples as Pretreatment for Analysis
Authors: Forsyth D S , Iyengar J R
Published: February 2020

Four commercially available proteases were tested, in conjunction with a lipase, for efficacy in hydrolyzing 3 tissue substrates: cod fillet, chicken egg, and bovine liver. Enzymatic hydrolysis of tissues minimizes the formation of emulsions during liquid-liquid extraction and does not accelerate the decomposition of acid- or base-labile analytes. Recovery of hexane and benzene phases from the hydrolysates was also evaluated. Protease from Streptomyces griseus combined with lipase from Candida cylindracea (available commercially) produced the highest percent hydrolysis (relative to classical acid hydrolysis) in all 3 tested tissues (60-95%) and the greatest recovery of hexane (100%) and benzene (92-100%) solvent phases.
Determination Of Total Sulfite In Shrimp, Potatoes, Dried Pineapple, And White Wine By Flow Injection Analysis: Collaborative Study
Authors: Sullivan John J , Hollingworth Thomas A , Wekell Marleen M , Meo Victor A , Saba Haytham H , Etemad-Moghadam Ali , Eklund Cheryl , Phillips John G , Gump Barry H
Published: February 2020

A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution Is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce S02 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but Interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm S02 and 10% for samples at >50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of ≥5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.
Comparison of Three Liquid Chromatographic Methods with FDA Optimized Monier- Williams Method for Determination of Total Sulfite in Foods
Authors: Lawrence James F , Chadha Rajinder K , Menard Cathie
Published: February 2020

Three liquid chromatographic (LC) methods employing amperometric detection were compared with the collaboratively studied FDA optimized Monier-Williams distillation method for the determination of total sulfite in 5 food types. The foods included lemon juice, white wine, instant mashed potatoes, golden raisins, and onion flakes. Two of the LC methods (one employing headspace sampling and the other direct injection) used ion-exchange chromatography with a basic mobile phase (pH about 10.8) and a glassy carbon electrode; the third (employing direct injection) used ion-exclusion chromatography with an acidic mobile phase (pH about 2) and a platinum electrode. All 4 methods produced similar results for the wine, lemon juice, and raisins. Results were different for instant mashed potatoes and onion flakes. The headspace- LC method and direct ion-exclusion LC method, both of which employed an alkaline sample extraction, yielded significantly higher values for sulfite in instant potatoes than did the other 2 methods. A large interfering peak with both direct LC methods prevented quantitation of sulfite in the onion flakes. All methods can detect sulfite as low as about 1 jtg/g in 4 of 5 food types examined.
Factors Influencing Optimization of Diffusion Assays for Antibiotics
Authors: Brady Marietta Sue , Katz Stanley E
Published: February 2020

Agar nutrient content, cylinder charge volume, thickness (volume) of the agar layer, and incubation temperature were 4 factors varied to determine their effect(s) on the optimization of the cylinder-plate diffusion assay. Chlortetracycline was the pilot antibiotic and Bacillus cereus was used as the assay organism. Zones of inhibition were larger when the incubation temperature was lower than that which was commonly used and/or when the nutrient level was decreased; the zones were smaller when the incubation temperature was raised and/or when an increased nutrient level was used. The thickness (volume) of the assay layer played the most important role; the thinner the layer the less the effect the cylinder charge volume had on the zone diameter. The slopes of the response lines were minimally affected by cylinder charge volume. For a 7 mL assay layer per standard Petri plate, cylinder charge volumes ranging from 150 to 250 μL had little effect on zone diameter. The linearity of the response line was unaffected by assay layer thickness (volume), nutrient level, temperature of Incubation, or cylinder charge volume. As long as the conditions for the assay were standardized, there were no discernible effects on recoveries or potencies.
Outgrowth of Naturally Occurring Clostridium botulinum in Vacuum-Packaged Fresh Fish
Authors: Lilly Timothy , Kautter Donald A
Published: February 2020

A total of 1074 test samples of commercial, domestic, vacuum- packaged fresh fish were studied to determine whether spoilage occurs before the products become toxic from naturally occurring Clostridium botulinum spores. The products were incubated for 12 days at 12°C (mild abuse). After incubation, they were tested for botulinal toxin and evaluated for organoleptic acceptability. Even when only marginally acceptable to laboratory personnel, none of the 1074 test samples were positive for C. botulinum toxin. Thus, the fish either contained no C. botulinum spores, or the spores were unable to grow out and produce toxin before spoilage made the product marginally unacceptable.
Determination of Ten N-Nitrosoamino Acids in Cured Meat Products
Authors: Pensabene John W , Fiddler Walter
Published: February 2020

A rapid, sensitive, and accurate solid-phase extraction method was developed for the measurement of 10 N-nitrosoamino acids (NAAs) in cured meat products. In the procedure, the comminuted meat was mixed with sulfamic acid and Celite, and then added to a glass column containing anhydrous sodium sulfate. The column was washed with pentane, and the NAAs were eluted with ethyl acetate. The eluate was concentrated, then derivatized with diazomethane followed by acetic anhydride-pyridine reagent. The NAA methyl esters and their acylated hydroxy derivatives were separated by gas chromatography on a DB-5 fused silica capillary column and quantitated with a thermal energy analyzer, a chemiluminescence detector specific for nitric oxide derived from the thermal denitrosation of nitrosamines. Recovery of 10 of the NAAs exceeded 75% at the 10 ppb level. The method is applicable to a wide range of cured meat products.
Dry Rehydratable Film for Enumeration of Total Aerobic Bacteria in Foods: Collaborative Study
Authors: Curiale Michael S , Sons Therese , Mcallister J Sue , Halsey Barbara , Fox Terrance L
Published: February 2020

A rehydratable dry-film plating procedure for aerobic plate counts has been compared to the standard agar plate method (966.23B and C, 15th ed.; 46.014-46.015, 14th ed.) in a collaborative study by 12 laboratories. Each laboratory analyzed the normal microflora of 3 samples in duplicate for 6 products. The aerobic plate counts ranged from 1.0 X 103 to 1.0 X 108 cfu/g. The products were flour, nuts, frozen raw shrimp, spice, frozen raw ground turkey, and frozen and refrigerated vegetables. Repeatability standard deviations of the 2 methods did not differ significantly for 13 of 18 test samples. For 1 shrimp and 2 turkey samples, the dry-film method had lower repeatability variances (P < 0.05) and for 1 spice sample the agar method had lower repeatability variances (P < 0.05). Relative standard deviations of repeatability were between 1.7 and 15.5% for the dry-film method and 1.2 and 16.0% for the agar method. Relative standard deviations of reproducibility ranged from 2.4 to 23.4 % for the dry-film method and 2.3 to 18.8% for the agar method. The dry rehydratable film method has been adopted official first action for determination of the aerobic plate count.
Improved Spectrophotometric Determination of Cyclopiazonic Acid in Poultry Feed and Corn
Authors: Chang-Yen Ivan , Bidasee Keshore
Published: February 2020

An improved visible spectrophotometric method has been developed for cyclopiazonic acid in poultry feed and corn. The method Is based on the reaction of cyclopiazonic acid with Ehrlich reagent and detection at 580 nm. Reaction conditions were optimized with respect to reaction and measurement times and acid and Ehrlich reagent concentrations. Calibration curves were linear from 1 to 20 μg cyclopiazonic acid in 3 mL Ehrlich reagent, with a lower detection limit of 0.08 mg/kg for 50 g samples of poultry feed and corn. Recoveries from 50 g samples of poultry feed spiked with cyclopiazonic ranging from 0.16 to 1.20 mg/kg averaged 93.8%. Moldy corn and poultry feed samples analyzed by this method contained between 1 and 4 mg/kg cyclopiazonic acid.
Rapid Screening Method for Deoxynivalenol in Agricultural Commodities by Fluorescent Minicolumn
Authors: Gordon William C , Gordon Linda J
Published: February 2020

A rapid screening procedure based on the selective adsorption of deoxynivalenol (DON) from extracts of wheat and corn has been developed. DON is extracted from the sample with acetonitrile-water (85 + 15) and partially purified on a preparative minicolumn. Solvent is evaporated and the residue is dissolved in toluene-acetone (95 + 5) and chromatographed on a novel detector minicolumn which selectively adsorbs DON. A blue fluorescence is produced when the column is heated 5 min at 100°C. The procedure is capable of detecting DON at ≥ 500 ng/g. Forty-three wheat samples, contaminated with DON at 60-6300 ng/g, were assayed by gas chromatography-mass spectroscopy (GC-MS) of the heptafluorobutyryl derivative of DON and by the selective adsorption procedure. Comparison of results showed 9 1% agreement between data from the 2 methods. Selective adsorption assays were positive for all samples that were ≥ 500 ng/g by GC-MS (no false negatives) and were negative for 85 % of samples < 500 ng/g (4/27 false positives). These four samples contained > 200 ng/g by GC-MS. Samples of wheat (64), corn (23), soybeans (8), and sorghum (6) were extracted and extracts were assayed by thin-layer chromatography and the selective adsorption procedure. Selective adsorption assays agreed with TLC results.
Gas Chromatographic-Electron Capture Detection Method for Determination of 29 Organochlorine Pesticides in Finished Drinking Water: Collaborative Study
Authors: Lopez-Avila Viorica , Wesselman Raymond , Edgell Kenneth
Published: February 2020

A joint U.S. Environmental Protection Agency/AOAC interlaboratory method validation study was conducted on EPA Method 508, Determination of Chlorinated Pesticides in Water by Gas Chromatography with an Electron Capture Detector, to determine the mean recovery and precision for analyses of 29 pesticides in reagent water and finished drinking water. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with 29 pesticides at 6 concentration levels, as 3 Youden pairs. Eleven volunteer laboratories extracted the spiked test waters with methylene chloride, performed a solvent exchange with methyl ferf-butyl ether, and analyzed an aliquot of each extract by gas chromatography with electron capture detection. Results were analyzed using an EPA computer program, Interlaboratory Method Validation Study (IMVS), which measured recovery and precision for each of the 29 pesticides and compared the performance of the method between water types. Method 508 was judged acceptable for all analytes tested. Only 3 analytes (α-chlordane, 4,4′-DDE, and methoxychlor) exhibited practical significant matrix effects. The method has been adopted official first action.