bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Enrichment and Plating Media for Isolating Listeria monocytogenes
Authors: Swaminathan B , Hayes Peggy S , Przybyszewski Vincent A , Plikaytis Brian D
Published: February 2020

We compared selective enrichment broths used by the U.S. Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA), Food Safety and Inspection Service, for their efficiency in the quantitative recovery of Listeria monocytogenes from a naturally contaminated Brie cheese that was obtained as part of an epidemic investigation. Quantitative recovery of Listeria in FDA broth (>2.4 x 10s colony forming units/mL) was significantly better than recovery in USDA broth (9.3 x 103 colony forming units/mL). When USDA broth was supplemented with i>glucose and Phytone (papaic digest of soy protein), its recovery efficiency improved but did not equal that of FDA broth for isolating L. monocytogenes from Brie cheese. A comparison of 4 selective plating media [modified McBride's agar, gum base nalidixic acid agar, lithium chloride-phenylethanol-moxalactam agar (LPM), and acriflavine-ceftazidime agar (AC)] showed that 3 L. monocytogenes strains belonging to serotype l/2a were partially or completely inhibited on LPM and AC agars. One strain of serotype l/2a formed microcolonies on modified McBride's agar after 48 h of incubation
Industry Perspectives on Listeria monocytogenes
Authors: Knight Michael T , Black James F , Wood David W
Published: February 2020

Industry concerns and our ongoing research on Listeria are discussed in this report. Topics include sampling for analysis; sanitizers and their use in manufacturing facilities; precautions on use of the FDA method for Listeria; use of the Vitek Gram Positive Identification Card; and a brief discussion on findings of Listeria in environmental samples taken from the same site at the same time of year in 1986 and 1987.
Sulfamethazine and Sulfathiazole Determination at Residue Levels in Swine Feeds by Reverse-Phase Liquid Chromatography with Post-Column Derivatization
Authors: Smallidge Robert L , Kentzer Elzbieta J , Stringham Kelly R , Kim Eun H , Lehe Connie , Stringham Rodger W , Mundell Elizabeth C
Published: February 2020

Twenty g sample, to which sulfamerazine has been added as internal standard, is extracted with 0.3N HC1 + 1.5% diethylamine in 25% methanol. The sample extract is chilled (to aid clarification), centrifuged, and filtered. The sulfonamides are separated from each other and from co-extracted materials on a C-18 reverse-phase column and detected at 450 nm following post-column derivatization with dimethylaminobenzaldehyde. Two isocratic mobile phases have been tested: (1) acetonitrile-2% acetic acid (17 + 83), with an analysis time of 13 min; and (2) acetonitrile-methanol-2% acetic acid (4 + 16 + 80), with an analysis time of 20 min but an improved analysis for some samples. As many as 40 samples have been analyzed at one time unattended with the aid of an autosampler. A total of about 1500 field samples have been assayed using the method. Method sensitivity is 0.1 ppm for either analyte in a hog finishing feed. Linearity for each of the analytes is satisfactory over a range of 0.4-25 ppm in spiked feeds. Coefficients of variation range from 13% at 0.5 ppm to 2% at 13 ppm as tested over a period of time in naturally contaminated samples. The absolute recovery of sulfamethazine varies with sample matrix, but, in the presence of sulfamerazine as internal standard, recovery has been 96.7-99.7% over the range of 0.1-10 ppm. Sulfamerazine and sulfamoxole were tested for their suitability as internal standards. Sulfamerazine is a good internal standard for sulfamethazine; neither is ideal for sulfathiazole. A recovery factor is necessary for estimating the level of sulfathiazole in feeds when either internal standard is used; however, either standard is satisfactory for correcting for feed matrix variation
Simple and Accurate Method for Determination of Ethylene Chlorohydrin in Dried Spices and Condiments
Authors: Aitkenhead Paul , Vidnes Arne
Published: February 2020

A simple and accurate method is described for the determination of ethylene chlorohydrin (ECH) by using capillary gas chromatography (GC) and flame ionization detection. Acetonitrile-methanol was chosen as the extraction solvent in preference to other solvents because its use reduced the number of compounds detected by the GC system, thus enabling easier identification and quantitation of ECH. The coefficient of variation for the method is 2.7% at 5 ppm, and recovery is good, even for the standard addition of 1 ppm. Fifteen different spices and condiments were analyzed using this method; 20% were identified as positive for ECH. The method also identifies the related compound ethylene bromohydrin (EBH).
Determination of Fat in Raw Milk: Comparison of Mojonnier (Ether
Extraction) and Gerber Method
Authors: Kleyn Dick H , Trout J Richard , Weber Maurice
Published: February 2020

Results are compared for the approved Gerber method that specifies a TC 11.07 mL pipet and 2 modifications that specify a TC 10.77 mL pipet or a weighed 11.125 g sample of milk rather than a pipetted sample. All results were also compared with results obtained with the Mojonnier method for determining the fat content of raw milk. The standard deviation is somewhat lower for the Mojonnier method than for any of the Gerber methods; among the Gerber methods, the standard deviations were lower for the TC 10.77 mL and 11.125 g modifications. It is recommended that one of these modifications replace the current specified TC 11.07 mL pipet method.
Improved Reagent for Detection of Allantoin in Thin-Layer Chromatographic Method for
Urine Stains on Foods and Packaging
Authors: Ferrera Robert S , Boese Jack L , Thrasher Joel J
Published: February 2020

Ten detection reagents known to react with either primary amine groups or indole derivatives were tested to improve sensitivity for allantoin (ALN) and indican (IND) in the official AOAC thin-layer chromatographic method for urine metabolites (44.175-44.177). The lowest levels found using the official method were 500 ng ALN and 6 ng IND. The best reagent was /7-dimethylaminocinnamaldehyde (pDMAC), which yielded intensely colored spots with both compounds. The lowest amounts consistently found were 125 ng ALN and 13 ng IND. pDMAC was also used as an overspray for ALN after the spray specified in the official method, /7-dimethylaminobenzaldehyde (pDMAB), was applied. This resulted in a detection limit of 250 ng. The overspray procedure was incompatible with IND detection, but provided an easy way to gain slightly greater sensitivity for ALN when use of pDMAB gave negative or borderline results. The combined use of pDMAC for ALN, and the official sprays (pDMAB and sodium acetate) for IND, maximized sensitivity for both compounds.
Liquid Chromatographic Method for Determination of Chloridazon in Technical Concentrates
and Formulated Products: Comparison with CIPAC Method
Authors: Sanchez-Rasero F , Heras Pena A
Published: February 2020

A liquid chromatographic method for determination of chloridazon in technical concentrates and formulated products has been developed and compared with the present CIPAC method. The new method uses the same procedures and reagents as does the CIPAC method, but a microbore column and a diode array detector are used instead of a normal-phase column and a single wavelength detector. A technical product, a wettable powder, and a suspension concentrate were analyzed by both methods; the results (g chloridazon/kg) were 836.7 ± 6.3 (RSDr 1.05%) and 822.1 ± 8.2 (RSDr 1.39%); 648.7 ± 7.6 (RSDr 1.64%) and 641.1 ± 6.7 (RSDr 1.45%); and 350.5 ± 5.6 (RSDr 2.24%) and 351.1 ± 4.0 (RSDr 1.57%) by the CIPAC method and the new method, respectively. Although precision, accuracy, and resolution are very similar for the 2 methods, the microbore column, diode array detector, and multichannel integrator specified in the new method give more information on the integration process and on the purity of peaks, and save on operating costs. Therefore, the authors propose that CIPAC methodology use this type of apparatus as soon as it is more generally available in laboratories.
Sensitive Enzyme Immunoassay of Cephalexin Residues in Milk, Hen Tissues, and Eggs
Authors: Kitagawa Tsunehiro , Gotoh Yukio , Uchihara Kazuyo , Kohri Youko , Kinoue Tihoko , Fujiwara Kunio , Ohtani Wataru
Published: February 2020

A sensitive enzyme immunoassay for cephalexin (CEX) was developed using the rabbit antiserum to CEX, Β-D-galactosidase-labeled CEX, and a double-antibody separation method. The immunogen of CEX was prepared by coupling the amino group of CEX to thiol groups introduced into bovine serum albumin by the use of N-(mmaleimidobenzoyloxy) succinimide as a cross-linker. Highly titered antiserum to CEX was produced in rabbits immunized with the immunogen. Enzyme labeling of CEX with Β-D-galactosidase was done by using 7V-(gamma-maleimidobutyryloxy)succinimide as the crosslinker. The limit of detection was 30 ng CEX/mL sample solution. Application of the method to CEX drug residues detected 30 ng/mL in milk, 60 ng/g in egg yolk, and 400 ng/g in hen tissue.
Determination of Seven Artificial Sweeteners in Diet Food Preparations by Reverse-Phase Liquid Chromatography with Absorbance Detection
Authors: Lawrence James F , Charbonneau Claudette F
Published: February 2020

The artificial sweeteners aspartame, saccharin, cyclamate, alitame, acesulfam-K, sucralose, and dulcin are determined in diet soft drinks and tabletop sweetener preparations. Samples are diluted, filtered, and analyzed directly by liquid chromatography on a C-18 reversephase column with a mobile phase gradient ranging from 3% acetonitrile in 0.02M KH2P04 (pH 5) to 20% acetonitrile in 0.02M KH2P04 (pH 3.5). Diet puddings and dessert toppings are extracted with ethanol, filtered, and diluted with mobile phase for analysis. The sweeteners, except sucralose and cyclamate, were detected by UV absorbance at either 200 or 210 nm. Sucralose was determined at 200 nm or by refractive index. Cyclamate was determined after post-column ion-pair extraction. The sweeteners stevioside and talin were not detected. Additives such as caffeine, sorbic acid, and benzoic acid did not interfere.
Gas Chromatographic Determination Of Residue Levels Of The Herbicides Trifluralin, Benefin,
Ethalfluralin, And Isopropalin In Soil With Confirmation By Mass Selective Detection
Authors: West Sheldon D , Weston Jack H , Day Edgar W
Published: February 2020

A method is presented for the simultaneous or individual determination of the dinitroaniline herbicides trifluralin, benefin, ethalfluralin, and isopropalin in soil. The herbicides are extracted with acetonitrile- water (99 + 1), and the extracts are purified with small, disposable Florisil cartridges prior to analysis by gas chromatography using an electron capture detector or a mass selective detector. When electron capture detection is used as the primary detection system, confirmation with selective detection can be obtained using gas chromatography-mass spectrometry with a mass selective detector and a capillary column operated in the split mode. The limit of detection is 0.01 ppm, and recoveries averaged 95-112% for the 4 herbicides in several different soil types fortified at levels of 0.01- 0.33 ppm
Determination of Gold in Animal Tissue by Graphite Furnace
Atomic Absorption Spectrophotometry
Authors: Kehoe Daniel F , Sullivan Darryl M , Smith Randall L
Published: February 2020

Historically, compounds that contain gold have been used to treat conditions such as rheumatoid arthritis in humans. However, understanding of the metabolic fate of gold in biological tissues has been limited by lack of sensitive quantitative methods of analysis. We addressed this problem by developing a graphite furnace atomic absorption (GFAA) spectrophotometric method to measure trace amounts of gold. This method was validated on small samples of beef liver, kidney, and bone. The samples were digested in micro-Kjeldahl flasks with a mixture of sulfuric, perchloric, and nitric acids; the residue was treated with aqua regia and extracted into methylisobutyl ketone (MIBK); levels of gold were then measured by GFAA. All the reagents were of an ultra-pure grade and were monitored for gold content. We established that the linear range of quantitation was from 1 to 2500 ppb. Multiple extractions with MIBK were not necessary to recover all the gold, and, in most cases, use of ultra-pure acids was not necessary. A scan of the extracts by inductively coupled argon plasma atomic emission spectrophotometry revealed no appreciable concentration of elements that would be most likely to interfere with the determination of gold. Average recoveries of gold ranged from 102 to 111%, and the overall coefficient of variation was 5.5%
Determination of Thiamphenicol in Bovine Plasma by Liquid Chromatography
Authors: Felice Lawrence , Abdennebi El Hassane , Ashraf Muhammed
Published: February 2020

A liquid chromatographic method is described for the measurement of thiamphenicol in bovine plasma. The plasma (1 mL) is extracted with ethyl acetate. After the solvent is evaporated under a stream of nitrogen, the residue is reconstituted in methanol-water and analyzed by reverse-phase liquid chromatography with UV detection at 224 nm. The intra-day recoveries for bovine plasma spiked with 5 and 50 μg/mL of thiamphenicol were 102 and 101%, respectively, with coefficients of variation of 2.40 and 0.28%, respectively. The interday recoveries for the 5 and 50 μg/mL samples were 103 and 101%, respectively, with coefficients of variation of 3.40 and 0.94%, respectively. The sensitivity of the method allows quantitation to at least the 100 ng/mL level
Development of Milk Powder Reference Materials Certified for Aflatoxin Mt Content (Part
II): Certification of Milk Powder RM 283
Authors: Van Egmond Hans P , Wagstaffe Peter J
Published: February 2020

The development of a full cream milk powder reference material, certified for its aflatoxin M, content (target concentration: 0.1 fig/ kg), is described. The material (RM 283) was prepared and certified within the Reference Material Programme of the Community Bureau of Reference, along with other members of a series of milk powder reference materials. Homogeneity, evaluated by determining the aflatoxin M, content of 30 units, was found to be acceptable (coefficient of variation of analysis results: 9.1%); stability has been demonstrated in a long-term study. The certification exercise involved 7 laboratories. Calibration, control of recoveries, blank values, and independence of the replicate measurements were emphasized. All sets of results of the certification exercise were accepted for statistical evaluation. A certified value for the aflatoxin M, content: 0.09(+0.04)(-0.02) Mg/kg was derived. The certification of RM 283 completes the series of 4 milk powder reference materials having certified aflatoxin M, contents
Gas Chromatographic-Mass Spectrometric Determination of Epoxidized Soybean Oil
Contamination of Foods by Migration from Plastic Packaging
Authors: Castle Laurence , Sharman Matthew , Gilbert John
Published: February 2020

A method for the quantitative determination of epoxidized soybean oil (ESBO) in foods is described. The procedure involves addition of a diepoxidized fatty acid ester internal standard, followed by lipid extraction from the food and transmethylation under basic conditions. Without further cleanup, the methylated fatty acid epoxides are derivatized to form 1,3-dioxolanes, which are then determined by capillary gas chromatography-mass spectrometry with selected ion monitoring. A detection limit of 2.0 mg/kg of epoxidized soybean oil in foods and a relative standard deviation of 7% have been achieved routinely. The method has been applied successfully to the analysis of cheeses, sandwiches, cakes, and microwave-cooked meals which have been contaminated with ESBO by migration from PVC film.
Disinfectant Testing Using a Modified Use-Dilution Method: Collaborative Study
Authors: Cole Eugene C , Rutala William A , Samsa Gregory P
Published: February 2020

An initial collaborative study of the AOAC use-dilution method (UDM), used for bactericidal disinfectant efficacy testing, demonstrated extreme variability of test results among the 18 laboratories testing identical hospital disinfectants. In an effort to improve the method, 32 changes were made by the UDM Task Force. These changes represented improvements in quality assurance practices and elimination of method variability; however, the basic framework of the method was retained. A second collaborative trial was conducted to determine if the interlaboratory variability of test results could be reduced to an acceptable level using the modified UDM. Twelve of the original 18 laboratories participated in the second study. Each laboratory processed 60 penicylinders (P) for each of the 6 randomly selected, federally registered disinfectants and 3 test organisms {Staphylococcus aureus, Salmonella choleraesuis, Pseudomonas aeruginosa). The number of positive penicylinders (>1 positive P/60 replicates = failure) for the 6 products when P. aeruginosa was used as the challenge organism ranged 1-30, 0-36, 0-15, 0-5, 0-3, and 0-60 for the 3 quaternaries and 3 phenolics, respectively. The results of the variance components analysis for P. aeruginosa and the other 2 organisms showed that the variance components for laboratories were not significantly reduced for any organism in this study. Such interlaboratory variability of results questions the use of the original or the modified UDM for registration purposes
From Parochial to International
Authors: Williams Alex
Published: February 2020

The customers for analytical measurement services have international requirements; they require data of proven validity that will be accepted internationally. This means that well researched and tested analytical methods must gain better international acceptance. The methods should be capable of producing results to the accuracy required by the customer. They need to be supported by the use of appropriate certified reference materials, and the analyst, in reporting results, should give an estimate of the accuracy obtained. In addition, an independent accreditation is needed of the quality assurance procedures of the laboratory to assure customers that the analytical methods have been used correctly.
Methods of Analysis for Toxic Elements in Food Products. 2. Review of USSR Standards on Determinations of Heavy Metals and Arsenic
Authors: Skurikhin Igor M
Published: February 2020

Methods of analysis prescribed by USSR standards for Hg, Pb, Zn, As, Cd, Cu, Fe, and Sn in foods are described: for Hg—colorimetry of tetraiodide mercurate and atomic absorption spectroscopy (AAS); for Pb, Cd, Zn, and Cu—polarography; for Cu—colorimetry with sodium diethyldithiocarbamate and zinc dibenzyldithiocarbamate; for As—colorimetry with silver diethyldithiocarbamate; for Sn— colorimetry with quercetin; and for Fe—colorimetry with o-phenanthroline. All of the methods have the necessary metrological characteristics, including intralaboratory repeatability value (r), interlaboratory reproducibility value (R), minimum quantity of the element to be determined in the analytical test portion (MQSM), and the coefficients that account for mercury and arsenic losses during analysis. Establishing constant r- and R-values for the methods under consideration is expedient because (a) the methods suggested are used for safety purposes; and (b) the optimum amount of the element studied in the test sample is determined, to a certain degree, by the mass of the test portion.
Large-Scale Preparation of Potassium Hydroxide-Modified Silica Gel Adsorbent
Authors: Lebo Jon A , Zajicek Jim L , May Thomas W , Smith Lawrence M
Published: February 2020

A large-scale method, using custom-made apparatus, is described for making potassium hydroxide-modified silica gel. Batches as large as 2.3 kg can be made in 16 man-hours. A smaller-scale version of the method, requiring no specialized apparatus, is also described. The method can be used to integrate this adsorbent into many sampleenrichment procedures.
Derivative Spectrophotometric Determination of Clotrimazole in Single Formulations and in Combination with Other Drugs
Authors: Bedair Mono M , Korany Mohamed A , Elsayed M Abd El-Hady , Fahmy Ossama T
Published: February 2020

First (D1) and second (D2) derivative spectrophotometric methods are presented for the determination of clotrimazole after its acid hydrolysis. Mixtures of clotrimazole with azidamfenicol and dexamethasone have been assayed using D2 measurement at 302 nm after acid hydrolysis for clotrimazole, D1 measurement at 288 nm for azidamfenicol, and D1 measurement at 436 nm after reaction with phenylhydrazinium sulfate for dexamethasone. Reproducible results with relative standard deviations of <2% are obtained. The proposed method has been successfully applied to the analysis of creams, topical solutions, and vaginal tablets.
Liquid Chromatographic Determination of Residual Reactants and Reaction By-Products in Polyethylene Terephthalate
Authors: Begley Timothy H , Hollifield Henry C
Published: February 2020

A precipitation procedure and liquid chromatography (LC) were used to measure the residual reactants and reaction by-products in polyethylene terephthalate (PET) polymers and food packages. The polymer is dissolved in l,l,l,3,3,3-hexafluoro-2-propanol/methyIene chloride and then precipitated with acetone. The filtered solution is evaporated almost to dryness, and the concentrate is diluted with dimethylacetamide for LC analysis. Recoveries for terephthalic acid (TA), bis(2-hydroxyethyl) terephthalate (BHET), and the PET cyclic trimer averaged 95,104, and 98%, respectively. The residual levels of TA, BHET, monohydroxy ethylene terephthalic acid, and the PET cyclic trimer were measured in commercial resins and food packages.
Criteria for the Detection of Analytes in Test Samples
Authors: Ruig Willem G De , Stephany Rainer W , Dijkstra Geo
Published: February 2020

Analytical control must be carried out by validated methods. Validation of methods for all possible situations, i.e., for all kinds of analytes in many different matrixes, by interlaboratory studies of meticulously described methods is unworkable because of the financial burden, the lack of analytical capacity, and the impossibility of standardizing highly sophisticated instrumentation between laboratories. Yet methods, particularly those used in regulatory control, must be validated. To overcome this dilemma, we suggest another approach for validation of quantitative analytical methods, viz., the application of certain "criteria." Such criteria are presented here for a number of analytical methods, including low and high resolution mass spectrometry, infrared spectroscopy, gas and liquid chromatography, thin-layer chromatography, spectrometric detection after TLC and LC, as well as general consideration of the whole analytical procedure. The criteria for a given method must be adopted by a board of experts for that method. Then, once an analysis fulfills the adopted criteria of the applied method, the presence of the investigated analy te can be taken as proved within the limits of ambiguity of the method. The criteria are already incorporated in a European Communities Commission Decision for detecting residues of substances having hormonal or thyrostatic action; criteria are submitted for a Commission Decision on analysis of residues of organic compounds in general.
Mycotoxin Analysis by Fast Atom Bombardment Tandem Mass Spectrometry
Authors: Uyakul Duangchan , Isobe Minoru , Goto Toshio
Published: February 2020

Positive fast atom bombardment tandem mass spectrometry is demonstrated to be an effective technique for determination of crude aflatoxins and sterigmatocystin-related compounds. The molecular ion was selected by the first system and bombarded to produce characteristic daughter ions that could be used to identify mycotoxins in mixtures and with the same molecular weight.
Liquid Chromatographic Determination and Gas Chromatographic-Mass Spectrometric Confirmation of Lasalocid Sodium in Bovine Liver: Interlaboratory Study
Authors: Newkirk David R , Barnes Charlie J
Published: February 2020

An analytical method has been developed that can reliably measure the metabolic marker residue of lasalocid. The method monitors this marker residue in food samples to ensure that the total residue of toxicological concern is not being exceeded. Interlaboratory studies of the liquid chromatographic determinative procedure and the gas chromatographic/mass spectrometric confirmatory procedure for lasalocid sodium at the 0.7 ppm level and higher were successful.
Evaluation of EPA Method 8120 for Determination of Chlorinated Hydrocarbons in Environmental Samples
Authors: Avila, Viorica Lopez , Dodhiwala S N , Milanes June , Beckert Werner F
Published: February 2020

Method 8120 of EPA Manual SW-846 has been evaluated in a singlelaboratory study. Several modifications made to the current method were implemented to allow determination of selected chlorinated hydrocarbons in complex environmental samples. The 2 packed gas chromatographic columns specified in Method 8120 were replaced with 2 megabore fused-silica open tubular columns chemically bonded with trifluoropropylmethyl siloxane and polyethylene glycol, respectively. The list of target compounds was expanded from 15 to 22 to include all possible trichlorobenzenes, tetrachlorobenzenes, and hexachlorocyclohexane (BHC) isomers. The Florisil cleanup procedure was modified to allow quantitative recovery of 20 of the 22 target compounds. A procedure that uses 1 g Florisil disposable cartridges and hexane-acetone (9:1) eluant was developed. This latter procedure gives quantitative recovery of all 22 target compounds from all matrixes tested. The revised method was tested with a variety of sample matrixes. Detection limits for water samples ranged from 1.4 ng/L for hexachlorobutadiene to 1300 ng/L for 2-chloronaphthalene; detection limits for 15 compounds were below 40 ng/L. Because of background contamination, detection limits for soil and sediment samples need to be determined on a case-by-case basis.
Evaluation of Modifications to Extraction Procedures Used in Analysis of Environmental Samples from Superfund Sites
Authors: Valkenburg Cornelius A , Munslow William D , Butler Larry C
Published: February 2020

Recoveries from an aqueous sample of the semi-volatile analytes listed on the EPA Target Compound List (TCL) are compared using 6 different methylene chloride extraction procedures. Four experimental designs incorporating a continuous extraction apparatus are evaluated, and 2 experimental designs using separatory funnel methods are tested. In addition, 2 concentration procedures are compared, and the loss of analytes associated with both extraction and concentration procedures are determined. These studies indicate that the most efficient and economical technique for the extraction of these compounds from an aqueous matrix is a single continuous extraction procedure performed at pH 2.
Amino Acid Rating Method for Evaluating Protein Adequacy of Infant Formulas
Authors: Sarwar Ghulam , Botting Herbert G , Peace Robert W
Published: February 2020

Amino acid profiles and/or protein digestibility (by the rat balance method) were determined for various forms (powder, ready-to-use, liquid concentrate, etc.) of cow's milk- and soy-based infant formulas obtained from 4 manufacturers. The essential amino acid data of the formulas were compared with that of human milk for the calculation of amino acid scores (based on the single most limiting amino acid). The product of amino acid score and total protein (g/100 kcal) was then termed "amino acid rating." Amino acid scores for the milk- and soy-based formulas ranged from 59 to 90 and from 59 to 81%, respectively, due to deficiencies in sulfur amino acids and/or tryptophan. Because of significantly higher total protein contents (g/100 kcal) of soy- (2.65-3.68) and milk-based (2.20-2.95) infant formulas compared to human milk (1.5), the relative amino acid ratings (human milk = 100) for all infant formulas except 2 liquid concentrates (having values of 87%) were above 100%. Values for true digestibility of protein in milk- and soy-based formulas ranged from 87 to 97 and from 92 to 95%, respectively. When corrected for protein digestibility, the relative amino acid ratings for all the milk-based liquid concentrates were below 100% (77-98%).
Visual and Semiquantitative Spectrophotometric ELISA Screening Method for Aflatoxin Bi in Corn and Peanut Products: Follow-up Collaborative Study
Authors: Park Douglas L , Miller Brinton M , Nesheim Stanley , Trucksess Mary W , Vekich Alan , Bidigare Barbara , Mcvey James L , Brown Lois H
Published: February 2020

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, The Netherlands, Switzerland, Tunisia, and the United States. Twelve raw and roasted peanut and corn portions containing various concentrations of natural aflatoxins and supplemented when appropriate with aflatoxin Bi were distributed to participating laboratories for testing. The assay is based on competition between an enzyme-conjugated aflatoxin Bj and (free) aflatoxins in the test sample for aflatoxin-specific antibodies coated onto interior surfaces of microtiter wells. After a wash step to remove all unbound aflatoxins, a substrate added to each well is catalyzed from a colorless to a blue solution by any bound enzyme-conjugated aflatoxin Bj present. The intensity of the color decreases as the amount of free aflatoxin Bt in the test portion increases. Final determination of aflatoxin concentrations can be made by either visual comparison with standard solutions or spectrophotometric comparisons (at 650 nm) to knowns. Overall correlation was good between ELISA and thin-layer chromatographic results for corn and roasted peanut products, with 93 and 98% correct responses for visual and instrumental determinations, respectively. For instrumental determinations of aflatoxin in corn and roasted peanuts in the <20 ng/g range, the relative standard deviations for repeatability (RSDr) were 14.9 and 41.4%, respectively, and the relative standard deviations for reproducibility (RSDR) were 45.7 and 43.5%, respectively. For instrumental determination of >20 ng/g, the respective RSDr and RSDR values were 19.4 and 52.7% for corn and 23.3 and 23.3% for roasted peanuts. For visual determinations in the <20 ng/g range, the respective RSDr and RSDR values for corn were 38.5 and 60.7% and for roasted peanuts 73.7 and 73.7%. The respective RSDr and RSDR values for determinations of >20 ng/g for corn were 13.5 and 59.5% and 24.3 and 57.3% for roasted peanuts. The ELISA method has been approved interim official first action as a screening method to determine the presence or absence of aflatoxin Bt at a concentration of ≥ 20 ng/g in corn and roasted peanuts.
Simulation of Aflatoxin Testing Plans for Shelled Peanuts in the United States and in the Export Market
Authors: Whitaker Thomas B , Dickens W J
Published: February 2020

The 1987 United States aflatoxin testing plan for shelled peanuts was designed with a final accept level of 25 parts per billion (ppb) total aflatoxin. Some of the importers of U.S. peanuts use aflatoxin testing plans with accept levels lower than 25 ppb. For example, the accept level of a testing plan used in The Netherlands is 5 ppb Bi or 10 ppb total aflatoxin. Whenever export lots are re-tested for aflatoxin by an importing country, some lots accepted in the United States will be rejected by the importing country's aflatoxin testing plan. Computer models were developed to determine the effects of decreasing the final accept level of the U.S. testing plan on the number of lots accepted and rejected in the United States and the number of exported lots accepted and rejected by The Netherlands testing plan. Decreasing the final accept level of the U.S. testing plan from 25 to 5 ppb increased the number of lots rejected in the United States by 371% while reducing the number of exported lots rejected by 51%. For every additional 8.3 lots rejected in the United States, one less export lot will be rejected.
Gamma-Ray Spectroscopic Determination of Iodine-131 and Cesium-137 in Foods: Two Collaborative Studies
Authors: Baratta Edmond J , Easterly David G
Published: February 2020

The AOAC method for iodine-131, cesium-137, and barium-140 in milk by gamma-ray spectroscopy (48.025-48.029) was extended to include other foods for the radionuclides iodine-131 and cesium-137. Two collaborative studies were performed to validate this extension. In the first study, a food sample containing 119 pCi ,3,I/kg and 53 pCi 137Cs/kg was sent to each of 45 laboratories for triplicate analyses. For 25 responses, the mean of the reported values was 123.8 pCi/kg for iodine-131, and for 27 responses, the mean was 53.4 pCi/kg for cesium-137. Repeatability (within-laboratory) standard deviations (sr) for iodine-131 and cesium-137 were 4.6 and 3.7 pCi/kg, respectively. Reproducibility (among-laboratories) standard deviations (sR) for iodine-131 and cesium-137 were 12.1 and 6.0 pCi/kg, respectively. In the second study, a food sample containing 25 pCi 13,I/kg and 27 pCi 137Cs/kg was sent to each of 54 laboratories for triplicate analyses. For 21 responses, the mean of the reported values was 25.0 pCi/kg for iodine-131, and for 19 responses, the mean was 28.9 pCi/kg for cesium-137. sr Values were 4.0 and 1.6 pCi/kg for iodine-131 and cesium-137, respectively, and SR values were 5.0 and 2.8 pCi/kg, respectively. The method extension was adopted official first action.
Generic Combustion Method for Determination of Crude Protein in Feeds:
Collaborative Study
Authors: Sweeney Rose A
Published: February 2020

Nine laboratories participated in a collaborative study on determination of crude protein in animal feeds to compare a generically described combustion method with the AOAC mercury catalyst Kjeldahl method (7.015). The combustion method was written in general terms of method principle, apparatus specifications, and performance requirements. The sample set comprised closely matched pairs of feed ingredients and mixed products ranging from 10 to 90% protein. Ten pairs ground to 0.5 mm were the focus of the study; 4 pairs were ground to 1.0 mm for comparison. Nicotinic acid and lysine monohydrochloride were included as standards. Collaborators were instructed to report their results for performance checks using materials supplied. Only one laboratory failed to meet the proposed limits. Seven laboratories used the LECO Model FP-228 analyzer and 2 used the LECO CHN 600 analyzer. For the 0.5 mm pairs, repeatability standard deviations (sr) ranged from 0.09 to 0.58 for the Kjeldahl method and from 0.14 to 0.33 for the combustion method, with a pooled sr value of 0.28 and relative standard deviation (RSDr) of 0.59%. Reproducibility standard deviations (SR) ranged from 0.23 to 0.86 (Kjeldahl) and from 0.30 to 0.61 (combustion), with a pooled sR value of 0.52 and RSDR of 1.10%. Grand means for the samples ground to 0.5 mm were 47.65% protein by the combustion method and 47.41% protein by the Kjeldahl method. For samples ground to 1.0 mm, corresponding values were 31.82 and 31.50% protein. The generic combustion method has been approved interim official first action.
Homogeneity of Meats Prepared for Analysis with a Commercial Food Processor:
Collaborative Study
Authors: Beebe Roberta M , Lay Eric , Eisenberg Sylvan
Published: February 2020

The food processor was evaluated as an alternative to the food chopper and bowl cutter for preparing meat samples for analysis in AOAC procedure 24.001. Samples of 6 meat types—cooked sausage, pork sausage, canned ham, hamburger, water-added ham, and smoked ham—were distributed to 9 laboratories for preparation using a food processor. The resulting 54 samples were sent to a USDA-accredited laboratory for analysis in triplicate for moisture, protein, and fat. Standard deviations and their 95% confidence intervals calculated for the analytical results were compared with USDA Performance Standards. With few exceptions, the upper limits were lower than the Performance Standards and for the exceptions, the intervals included the Performance Standards. By these criteria, the food processor is as effective in preparing homogeneous samples as the preparation procedures used to set the Performance Standards. Collaborators found the processor faster to use and easier to clean than the food chopper. Use of the food processor has received interim approval as an alternative to the food chopper or bowl cutter in AOAC procedure 24.001 for preparing meat samples for analysis.
Precision Parameters of Standard Methods of Analysis for Dairy Products
Authors: Peeler James T , Horwitz William , Albert Richard
Published: February 2020

The available collaborative studies for standard methods of analysis for various constituents of milk and milk products were examined in an attempt to assign specific repeatability and reproducibility precision parameters to these methods. The different collaborative assays for the primary constituents (moisture/solids, fat, protein), the nutritionally important elements (calcium, sodium, potassium, phosphorus), and miscellaneous analytes/physical constants (ash, lactose, salt, freezing point) produced different estimates of the precision parameters for the same method. A suitable summary of the precision estimates from collaborative studies is given by the reproducibility relative standard deviation, RSDR, which is relatively constant within a product and permits comparisons across products. An estimate of the variation of RSDR for an analyte from a number of collaborative studies is presented in terms of the median and 90% interval (the range of the centermost 90% of values). These estimates are only informative when a substantial number of independent studies are available for pooling the independent estimates to form a distribution of RSDR values. The RSDR for the determination of the primary constituents of milk and milk products is characterized by a median RSDR of 1% and a 90% interval of 0.3-3%, with RSDR estimates occasionally occurring below 0.3% and above 4%. These overall estimates appear to be independent of analyte, matrix, and method and apply to concentrations of primary constituents that range from about 2 to 80%. The repeatability relative standard deviation, RSDR, is unstable, although it tends to converge to about 0.5-0.7 X RSDR. Too few collaborative assays are available to characterize RSDR for the determination of certain other constituents (acidity, ash, lactose, salt, and the nutritionally important elements) unless RSDR values for different analytes, methods, and matrixes are pooled on the basis of similar analyte concentrations. When pooled, the RSDR values are generally better than predicted from the Horwitz equation, RSDR (%) = 2 exp (1—0.5 logioC), where C is the concentration expressed as a decimal fraction; all but one of 661 RSDR values are within the upper empirical limit of twice this curve.
Caffeine as Main Interfering Compound in Radioimmunoassay of Aflatoxin Bj in Coffee Samples
Authors: Rauch Pavel , VĺDen Ivan , DavĺDek Tomáś , VelĺŚek Jan , Fukal Ladislav
Published: February 2020

The content of caffeine in coffee extracts prepared for radioimmunoassay of aflatoxin Bi was determined by gas chromatography. The extracts from coffee beans and decaffeinated coffee contained 1.76- 4.60 and 0.71-0.85 g caffeine/kg, respectively. These concentrations of caffeine caused false results in radioimmunoassay of aflatoxin Bi in the range 1.0-2.8 μg/kg for coffee beans and 0.3-0.4 μg/kg for decaffeinated coffee.
Spectrophotometric Method for Measurement of Lactose in Milk and Milk Products by Using Dialysis
Authors: Mistry Vikram V , Hassan Hassan N , Baer Robert J
Published: February 2020

A simple method for measuring lactose in milk and milk products by using dialysis is described. A sample of milk, diluted milk powder, cultured buttermilk, or Cheddar cheese whey is dialyzed against water in a test tube at 45°C for 1.5 h. Lactose from the product is extracted into the water and Teles reagent is added. Absorbance was converted to percent lactose using a standard curve. Lactose obtained by the dialysis method was comparable to results obtained by the ultraviolet enzymatic and infrared methods. The method was not suitable for yogurt, which contains galactose that reacts with the Teles reagent. The new method for lactose measurement is simple and does not require precipitation of proteins, filtration, or centrifugation.
Liquid Chromatographic Method for Determination of Extractable Nitroaromatic and Nitramine Residues in Soil
Authors: Jenkins Thomas F , Walsh Mariannee , Schumacher Patricia W , Miyares Paul H , Bauer Christopher F , Grant Clarence L
Published: February 2020

An analytical method was developed to determine the concentration of nitroaromatic and nitramine residues in soil. Air-dried soil samples are ground with a mortar and pestle and extracted with acetonitrile in an ultrasonic bath. A portion of extract is diluted with aqueous CaCh to flocculate suspended particles, filtered, and analyzed by liquid chromatography. The method provides linear calibration curves over a wide range of concentration. Detection limits ranged from 0.03 to 1.27 ng/g. Recovery of spiked analyte was better than 80% for all analytes tested. Each step in the analytical procedure was optimized using spiked and field-contaminated soils. This optimization included tests to (1) assess the effectiveness and kinetics associated with various extraction methods, solvents, and soil-to-solvent ratios; (2) compare separations achievable using various combinations of reverse-phase columns and eluants; (3) assess analyte recovery and ease of use for various procedures to remove particles from extracts; and (4) document stability of soil extracts and analytical stock and working standards. A ruggedness test and a preliminary assessment at 2 other laboratories indicated that the method was sufficiently rugged to justify a full-scale collaborative test. A comparison of extraction kinetics for spiked soil vs field-contaminated soil revealed very different kinetic behavior, indicating it is unwise to develop extraction procedures based solely on spiked soils.
Formaldehyde Quantitation in Air Samples by Thiazolidine Derivatization:
Factors Affecting Analysis
Authors: Yasuhara Akio , Shibamoto Takayuki
Published: February 2020

A new method for the determination of trace levels of formaldehyde in air was developed and validated. The method is based on the reaction of formaldehyde with cysteamine to form thiazolidine. Air samples containing trace levels of formaldehyde were prepared from paraformaldehyde. The percent yield of formaldehyde from paraformaldehyde was 85.1 ± 1.14%. Air samples were bubbled into an aqueous cysteamine trap. Thiazolidine formed from formaldehyde and cysteamine in the trap was determined by gas chromatography with a fused silica capillary column and a nitrogen-phosphorus detector (NPD). The lowest detection level for thiazolidine was 17.2 pg, equivalent to 5.80 pg formaldehyde. The recovery efficiency of trace gas phase formaldehyde in air was greater than 90%. Formaldehyde levels in ambient laboratory air were 48.9-56.2 ppb (v/v).
Liquid Chromatographic Determination of Sulfite in Grapes and Selected Grape Products
Authors: Perfetti Gracia A , Joe Frank L , Diachenko Gregory W
Published: February 2020

A liquid chromatographic (LC) method is described for the determination of sulfite in grapes and certain grape products. Sulfite is extracted from grapes with aqueous formaldehyde solution buffered at pH 5; free sulfite is converted to hydroxymethylsulfonate (HMS), which is extremely stable at pH 3-7. Subsequent heating to 80°C for 30 min converts reversibly bound forms of sulfite to HMS. The extract is then analyzed by reverse-phase ion-pairing liquid chromatography, using a Cjg column and a mobile phase of aqueous 0.005M tetrabutylammonium ion in 0.05M acetate, pH 4.7, and a flow rate of 1 mL/min. Aqueous KOH is added to the eluate to convert HMS to free sulfite, which is then treated with 5,5'-dithiobis[2-nitrobenzoic acid]. This reaction produces the 3-carboxy-4-nitrothiophenolate anion, which is determined by measurement of electronic absorption at 450 nm. For grapes spiked with HMS at 5-20 ppm (as S02), recoveries ranged from 92 to 112%, with a coefficient of variation of 4.6%. The method was also used to determine sulfite in various grape products. Results were comparable to those obtained by the AOAC official Monier-Williams method.
Honey Protein as Internal Standard for Stable Carbon Isotope Ratio Detection of Adulteration of Honey
Authors: White Jonathan W , Winters Kenneth
Published: February 2020

Using the difference in stable carbon isotope ratio between a honey and its protein fraction permits objective evaluation of possible adulteration of honey with small amounts (7-20%) as well as larger amounts of corn or cane sugar. The present uncertainty in interpretation of results from pure honeys with 5,3C values outside the generally accepted limits for pure honey of —27.5%o to —23.5%o is eliminated; likewise TLC testing to resolve questionable samples with 5n C values between —23.5 and —21.5%o is not needed. Fifty certified samples of pure honey were used to establish criteria for purity, and 38 other samples with δ13C values in the “questionable” or “adulterated” range for the AOAC official method were tested. A difference of 1.0%o or more between honey and protein fractions is proposed to indicate adulteration.
Turbidimetric Microbiological Assay Results Calculated by a BASIC Computer Program
Authors: Anderson Ellen M
Published: February 2020

A BASIC computer program was used to calculate the results of microbiological vitamin assays. The program, which incorporates the official AOAC guidelines for microbiological methods, reduces the uncertainty inherent in manual curve plotting and interpolation and minimizes the human error of repetitive calculations. Because the BASIC programming language is well suited for use on self-contained personal computers, it can be easily adapted by small laboratories
Liquid Chromatographic-Electrochemical Determination of Ethylenethiourea in Foods by Revised Official Method
Authors: Krause Richard T
Published: February 2020

AOAC official method 29.119-29.125 was revised to determine ethylenethiourea (ETU) directly by a liquid chromatographic-electrochemical (LC-EC) determinative technique and to improve ETU recovery. ETU is extracted from food products with a methanolaqueous sodium acetate solution. A portion of the concentrated filtrate is added to a column of diatomaceous earth, and ETU is eluted with 2% methanol in methylene chloride to separate it from food coextractives, which are retained on the column. The eluate is collected in a siliconized flask and evaporated, the residue is dissolved in water, and 20 nL of solution is injected onto an LC graphitized carbon column. ETU is eluted from the LC column with a mobile phase of acetonitrile-aqueous 0.1M phosphoric acid-water (5 + 25 + 70), and the eluted ETU is detected by using an amperometric electrochemical detector equipped with a gold/mercury working electrode. Recovery data were obtained by fortifying 13 food products with ETU: baked potatoes; canned applesauce, mushrooms, creamed spinach, green beans, spinach, and tomatoes; cooked fresh cabbage and frozen collards; fresh celery and lettuce; grape jelly; and powdered sugar cake donuts. Raw celery was found to cause low ETU recoveries. Average percent recoveries of ETU from the other 12 food products were 92 with a standard deviation of 12 for the low (0.05 and 0.1 ppm) fortification levels and 90 with a standard deviation of 6 for the higher (0.5 and 1 ppm) fortification levels. The limits of quantitation were 0.01 and 0.02 ppm for food products with low and high sugar content, respectively.