bluuebunny/crossref_metadata_2025 huggingface dataset:
Update on Validation of Microbiological Methods by AOAC INTERNATIONAL
Authors: Andrews Wallace H
Published: February 2020

An update is presented of the microbiological methods validated by AOAC since 1983. A sequential listing of the microbiological methods adopted first action between 1939 and 1993 gives the permanent new numbers of each, as introduced in Official Methods of Analysis, 15th Edition. Consideration is given to the expanded applicability of approved methods with respect to food matrix; the predominance of methods for the detection, identification, and serological testing of Salmonella spp.; and the procedures for coliforms and Escherichia coli, which were most frequently approved between 1973 and 1993. The substantial increase in validation of test kits is discussed, and categories of methods for the modification of test kits already approved are defined.
Extraction of Light Filth from Whole Wheat Flour, Flotation Method: Collaborative Study
Authors: Glaze Larry E , Bryce John R
Published: February 2020

An additional extraction/flotation method for the determination of light filth in whole wheat flour was validated through a collaborative study. A 50 g test portion is boiled in a 3% HCI solution. The mixture is washed with hot tap water on a No. 230 sieve. Then the residue is boiled in iso-propanol, transferred to a No. 230 sieve, and washed again. The residue is transferred to a Wildman trap flask using 40% isopropanol. The filth is isolated by flotation in mineral oil and a mixture of Tween 80 and Na4EDTA in 40% isopropanol. Average recoveries by 8 collaborators were 88.8 and 91.7% for insect fragments and rat hairs, respectively. The extraction/flotation method for determination of light filth in whole wheat flour has been adopted first action by AOAC INTERNATIONAL as an additional procedure to the AOAC Official Method 941.16, Filth in Grain Products.
Application of Gas Chromatography/Matrix Isolation/Fourier Transform Infrared Spectroscopy to the Identification of Pyrrolizidine Alkaloids from Comfrey Root (Symphytum officinale L.)
Authors: Mossoba Magdi M , Lin Hubert S , Andrzejewski Denis , Sphon James A , Betz Joseph M , Miller Lee J , Eppley Robert M , Trucksess Mary W , Page Samuel W
Published: February 2020

This paper demonstrates that pyrrolizidine alkaloids (PAs) extracted from comfrey root grown in Washington State (USA) can be identified by gas chromatography/matrix isolation/Fourier transform infrared (GC/MI/FTIR) spectroscopy. Infrared spectral bands observed in the fingerprint region were unique even for closely related structures. The identities of the 4 major components, intermedine, lycopsamine, 7-acetylintermedine, and 7-acetylly-copsamine, were confirmed by comparison with standards. Confirmation was also obtained by using the established techniques of electron ionization and positive ion chemical ionization gas chro-matography/mass spectrometry. The infrared spectra observed for the components of the root extract were consistent with known structures of specific PAs. The identities of the minor components, sym-phytine and its isomers symlandine and/or sym-viridine, in the same extract were not confirmed.
Determination of Cholinesterase Activity in Brain and Blood Samples Using a Plate Reader
Authors: Tor Elizabeth R , Holstege Dirk M , Galey Francis D
Published: February 2020

A rapid method is described for the quantitative determination of cholinesterase activity in large batches of blood and brain samples. The technique is an adaptation of the Ellman procedure for a 96-well microtiter plate reader. Ten samples can be analyzed simultaneously in 5 min, with all calculations, including statistical analysis, done automat- ically. The method detection limit is 0.1 μM/mL/min for blood and 0.1 μM/g/min for brain samples. The procedure has been applied to the routine analyses of samples presented to the veterinary diagnostic laboratory. Method performance, quality control, and normal ranges of cholinesterase activity in live- stock and other animals are described.
Enzyme-Linked Immunoassay for Detection of Listeria monocytogenes in Dairy Products, Seafoods, and Meats: Collaborative Study
Authors: Curiale Michael S , Lepper Wendy , Robison Barbara
Published: February 2020

A collaborative study was conducted to evaluate Listeria-TekTM, an enzyme-linked immunosorbent assay (ELISA) for detection of Listeria monocytogenes and other Listeria spp. in foods. The present ELISA method was compared to the U.S. Food and Drug Administration culture method for detection of L. monocytogenes in dairy products and seafoods and to the U.S. Department of Agriculture Food Safety and Inspection Service method for detection of L. monocytogenes in meats. Replicate samples of 6 food types (frankfurters, roast beef, Brie cheese, 2% milk, raw shrimp, and crab meat) inoculated with L. monocytogenes and uninoculated control samples were analyzed by the collaborators. L. monocytogenes was identified in 593 samples by the ELISA method and in 574 samples using culture procedures. Identical results were obtained for 506 positive samples and 419 negative samples using the ELISA and culture methods for an overall agreement rate of 85.6%. The enzyme-linked immunoassay for detection of L. monocytogenes in dairy, seafood, and meat products has been adopted first action by AOAC INTERNATIONAL.
Multifunctional Column Coupled with Liquid Chromatography for Determination of Aflatoxins B1, B2, G1, and G2 in Corn, Almonds, Brazil Nuts, Peanuts, and Pistachio Nuts: Collaborative Study
Authors: Trucksess Mary W , Stack Michael E , Nesheim Stanley , Albert Richard H , Romer Thomas R
Published: February 2020

An AOAC/IUPAC collaborative study was conducted to evaluate the effectiveness of a multifunctional column for the determination of aflatoxins. The test portion is extracted with acetonitrile–water (9 + 1), the extract is filtered, and the filtrate is passed through the column. The aflatoxins in the eluate are determined by reversed-phase liquid chromatography after derivatization with trifluoroacetic acid. Naturally contaminated corn, almonds, Brazil nuts, peanuts, and pistachio nuts spiked with total aflatoxins at 5,10,20, and 30 ng/g were sent to 12 collaborators in the United States, Denmark, France, Japan, and Switzerland. Eleven collaborators completed the study. Average recoveries of total aflatoxins for each spike level for the various commodities (excluding Brazil nuts at 5 ng/g) were 93,97,95, and 95%, respectively; the repeatability relative standard deviation (RSDr) ranged from 6.0 to 23.2% and the reproducibility relative standard deviation (RSDR) ranged from 12.0 to 69.4%. The multifunctional column coupled with a liquid chromatographic method for determination of aflatoxins in corn, almonds, Brazil nuts, peanuts, and pistachio nuts has been adopted first action by AOAC INTERNATIONAL.
Rapid Screening of Pharmaceuticals by Thin-Layer Chromatography: Analysis of Essential Drugs by Visual Methods
Authors: Kenyon Allen S , Flinn Paul E , Layloff Thomas P
Published: February 2020

A method for rapidly screening pharmaceuticals by thin-layer chromatography has been designed for use in areas with limited resources and by operators with limited training. An apparatus for performing the analysis in a plastic bag under equilibrium conditions was designed. Results can be reproduced by different operators and in different locations. The analysis can be performed without electricity or in a remote area, away from a laboratory. It is especially suited for field use in developing countries. The method is low cost, maintenance-free, fast, and reliable; it also uses limited volumes of solvents. The analyses can be performed without weighing if reference materials can be supplied in tablet form, provided the drug content is listed and only one unit is required for each analysis. All procedures were developed for the analysis of drugs from a partial list of essential drugs established by the World Health Organization. Three drugs were selected and prepared in the form of reference tablets. Comparisons with the analyses of the drugs in standard dosage forms were made by using reference tablets and primary USP standards. Comparable results were obtained, proving that the screening process can be conducted by using reference tablets and without weighing either the sample or the reference. The method has been successfully demonstrated and used in Swaziland, by high school teachers in the United States, and by personnel from the Ministry of Health in Saudi Arabia. Personnel can be trained in a short time to perform screening analysis of drugs.
Determination of pH of Soils by Different Methods: Collaborative Study
Authors: Kalra Yash P
Published: February 2020

Fifty-three laboratories (including author’s) from Canada, India, Israel, and the United States participated in a collaborative study for the measurement of pH of different types of soils. A method with 2 alternative procedures was used for pH measurements of mineral soils (alternative I for soils containing less than 17⋊ organic carbon and alternative II for soils with variable salt content), a second method was used for saline-sodic soils, and a third method was used for organic soils (soils containing at least 17⋊ organic carbon). The pH was measured potentiometricaIly. The methods were selected by the Soil Science Society of America, S889 Committee on Coordination of Official Methods of Soil Analysis. Each laboratory used all 4 procedures to analyze 10 blind duplicate samples per procedure. The repeatability relative standard deviation values (RSDr) were 1.45–7.80% for mineral soils tested by the alternative 1,0.95–6.91% for mineral soils tested by the alternative II, 0.74–7.09% for saline-sodic soils, and 0.73–4.66% for organic soils. The corresponding reproducibility relative standard deviation (RSDR) values were 2.67–10.75%, 2.03–7.54%, 2.45–9.93%, and 2.15–6.32%. Repeatability and reproducibility data indicated that the results are within acceptable levels. The 3 methods for pH measurements of mineral, saline-sodic, and organic soils were adopted first action by AOAC INTERNATIONAL.
Babcock Bottle Certification Appparatus Performance Evaluation
Authors: Lynch Joanna M , Barbano David M , Houghton George , Fleming J Richard
Published: February 2020

The use and performance of a computer-controlled apparatus for certification of Babcock bottles used for payment testing were evaluated. The apparatus delivered mercury into the bottle neck using a syringe mounted on a motorized pump. Syringe movement and the collection and calculation of data were controlled by computer. The apparatus was evaluated using four 8% milk bottles (total volume 1.600 mL; bottles rejected if deviation was ≥0.008 mL) and four 50% short-neck cream bottles (total volume 5.000 mL; bottles rejected if deviation was ≥0.050 mL). Six milk and 5 cream bottle trials were conducted; each bottle was read 5 consecutive times for each trial. As a percentage of the rejection criteria, average repeatability was 5–6% and reproducibility was 9–10%. These values were similar for both types of bottles. The evaluation of the apparatus demonstrated acceptable within- and between- days performance in relation to the rejection criteria and volumes measured. Because the apparatus creates a closed system during certification, an additional experiment was conducted with 50% short-neck cream bottles to determine the effect of internal pressure within a bottle on volume estimates. Four trials were conducted, as previously described, using 4 control and 4 experimental bottles. Volume between the 0 and 50% marks (5 mL) was determined. Holes were drilled in the experimental bottles to eliminate internal pressure for the final 2 trials. The estimated volume of bottles under pressure was 0.0054 ± 0.0012 mL greater than without internal pressure (i.e., about 11% of the rejection criteria). We concluded that any pressure effect was small relative to other factors that affect volume determination.
Detection of Bixin, Lycopene, Canthaxanthin, and β-Apo-8′-Carotenal in Products Derived from Red Pepper
Authors: Mínguez-Mosquera M Isabel , Hornero-Méndez Dámaso , Garrido-Fernández Juan
Published: February 2020

An analytical method using either thin layer or liquid chromatography is proposed for the detection of 4 pigments (bixin, lycopene, canthaxanthin and (β-apo-8′-carotenal) that can be used fraudulently to intensify the natural color of products derived from red pepper (oleoresins, paprika, paprika paste, etc.)- Similarly, the addition of other colorant natural products containing some of these pigments as major pigments (such as tomato for lycopene and Bixa orellana seeds for bixin) can be detected. The method proposed can also be used to control the aforementioned pigments in their natural sources as well as in food products.
Postcolumn Derivatization Liquid Chromatographic Method for Paralytic Shellfish Toxins
Authors: Oshima Yasukatsu
Published: February 2020

More than 20 analogues of saxitoxin occur naturally. An accurate analytical method applicable to all saxitoxins is required because of the recent findings that decarbamoyl toxins and C (N-sulfocarbamoyl- 11-hydroxysulfate) toxins are metabolites of marine animals or major products of some dinoflagellate species. Almost all the toxins could be determined by ion-interaction chromatography on a silica-based reversed-phase (C8) column with postcolumn periodate oxidation and fluorescence detection. Toxin groups of different net charges were separately determined by isocratic elution using different mobile phases. For determination of the saxitoxin group (net charge, 2+) and the gonyautoxin group (net charge, 1+), use of 1-heptanesulfonate as counterion, with or without acetonitrile in the mobile phase, resulted in resolution of decarbamoyl toxins from their carbamate analogues. C toxins having both M-sulfocarbamoyl and 11-hydroxysulfate moieties on the same molecule were completely resolved using the tetrabutylammonium ion. High sensitivity with detection limits ranging from 20 to 110 fmol were achieved as a result of reduced band broadening and optimized reaction conditions. For applications to biological matrixes, a cleanup procedure using a C18 solid-phase extraction cartridge was effective in preventing false peaks. When applied to low-toxicity shellfish, the liquid chromatographic method gave higher values than the standard mouse bioassay, because of underestimation by the bioassay.
Liquid Chromatographic Determination of Residual Isocyanate Monomers in Plastics Intended for Food Contact Use
Authors: Damant Andrew P , Jickells Sue M , Castle Laurence
Published: February 2020

A liquid chromatographic (LC) method was developed for the analysis of 10 isocyanates in polyurethane articles and laminates intended for food use. Residual isocyanates are extracted by dichloromethane with concurrent derivatization by 9-(methylaminomethyl)anthracene. The resultant derivatives are analyzed by reversed-phase LC with fluorescence detection. Separation of the isocyanates was studied and optimized. Quantitation uses 1-naphthyl isocyanate as internal standard and standard addition to the food package. Validation demonstrated the method to have good precision (± 2–5%) and recovery (83–95%) for samples spiked with isocyanates at 0.1 mg/kg. The limit of detection was 0.03 mg/kg. Analysis of 19 commercial polyurethane or laminate food packages demonstrated that the method was not prone to interferences. Residues of diphenylmethane-4,4′-diisocyanate were detected in 5 packages and ranged from 0.14 to 1.08 mg/kg.
Adulteration of Soluble Coffee with Coffee Husks and Parchments
Authors: Prodolliet Jacques , Bruelhart Melene , Blanc Maurice B , Leloup Valerie , Cherk Genevieve , Donnelly Catherine M , Viani Rinantonio
Published: February 2020

Commercial soluble coffee can be adulterated with coffee husks or parchments. Xylose is a good tracer for this type of mispractice. The analysis of total xylose in a wide selection of green beans and the assessment of its fate during processing allowed the derivation of a maximum total xylose limit of 0.40%, above which a soluble coffee should be considered as adulterated. Out of the 700 commercial soluble coffees analyzed, 81 exhibited a total xylose level above this limit. Of the samples with total xylose level lower than the limit, 99% displayed concentrations in free mannitol and total glucose below 0.30 and 2.10%, respectively.
Homogeneous Sample Preparation of Raw Shrimp Using Dry Ice
Authors: Bunch Elaine A , Altwein Diane M , Johnson Lloyd E , Farley Joyce R , Hammersmith Amy A
Published: February 2020

Sample homogeneity is critical to accurate and reproducible analysis of trace residues in foods. A method of uniform sample preparation using dry ice is described for shrimp. Other sample preparation techniques for raw shrimp produce nonhomogeneous samples. Sample homogeneity was determined through analysis of chloramphenicol added to intact tiger or white shrimp prior to sample preparation. Simulated chloramphenicol residue levels were 50, 15, 10, and 5 ppb. No significant differences were noted when analyses of shrimp inoculated with chlor-amphenicol prior to sample preparation with dry ice were compared with analyses of shrimp spiked after grinding with dry ice. Grinding shrimp with dry ice produced samples with homogeneous chloramphenicol residues. This technique should be applicable to other tissues and vegetable products.
LC-Receptorgram: A Method for Identification and Quantitation of β-Lactams in Milk by Liquid Chromatography with Microbial Receptor Assay
Authors: Zomer Eliezer , Quintana Julio , Saul Steven , Charm Stanley E
Published: February 2020

A rapid determinative method was developed for identification and quantitation of common β-lactam drugs (e.g., amoxicillin, ampicillin, cephapirin, penicillin G, ceftiofur, and cloxacillin) in milk. This method combines the advantages of liquid chromatography (LC) with the selectivity and sensitivity of a microbial receptor assay. This LC-receptorgram procedure identifies and quantitates β-lactams at 10 ppb or lower within 3 h. A simple purification scheme, using solid-phase extraction, gave recoveries ranging from 50% for amoxicillin to 80-90% for other β-lactams. Individual drugs were separated by LC using a reversed-phase C8 column and an isocratic buffer system containing methanol (35%) in phosphate buffer (50 mM, pH 6.0). The Charm II quantitative procedure was used to detect (5-lactams in the LC fractions. In a blind study of raw milk fortified with β-lactams, the coefficients of variance for quantitation of 6 β-lactams at the safe levels ranged from 4.1 to 13%. The confidence level for selectivity was greater than 99%, and for detection of positives at safe levels, it was 95% or greater. Analysis of 6 β-lactams in incurred samples showed that all 6 drugs are depleted to below 10 ppb in less than 48 h. Incurred samples with cephapirin and ceftiofur contained active metabolites, in addition to parent drug, that were detected by the LC-receptorgram. In market milk samples that screened positive in routine testing programs, penicillin G, cephapirin, and ceftiofur were identified by the LC-receptorgram as the most common contaminants. In several samples containing cephapirin or ceftiofur, an active metabolite was detected in addition to the parent drug. Only the parent drug was detected for other β-lactams.
Determination of Long-Life Radiocesiums Cs-134 and Cs-137 in Food by γ-Ray Spectrometry: Interlaboratory Study
Authors: Beuaars Paul R , van Duk Remmelt , Geertsen Jos A M , Nootenboom Hans
Published: February 2020

A gamma-ray spectrometric method for the determination of cesium-134 and cesium-137 in food was studied collaboratively in 13 laboratories, using 8 samples (including 4 blind duplicates) consisting of heather honey, milk, and mixed dried herbs. Low resolution, shielded Tl-activated Nal scintillation detectors were used to measure Cs-137 in the photon energy range 516 to 714 keV and Cs-134 in the range 716 to 880 keV. Results were generally acceptable and no outliers were identified for any sample results. The method worked well in the absence of “fresh” fission products. The method was less appropriate for radiocesium determinations where the activity concentration was <100 Bq/kg at a counting time of 900 s or where the Cs-137/Cs-134 activity-ratio was larger than 10. The accuracy of mean measurements of both isotopes (relative to reference measurements made in one laboratory using a high resolution GeLi detector) was in the range of 98 to 103%. For all samples analyzed, the repeatability relative standard deviation (RSDr) values varied from 4.3 to 11.7% for 2 Cs-134 levels ranging from 121 to 337 Bq/kg and from 2.0 to 7.3% for 4 Cs-137 levels ranging from 210 to 1130 Bq/kg, whereas the reproducibility relative standard deviation (RSDR) values for these levels ranged from 10.7 to 14.9% for Cs-134 and from 4.1 to 7.4% for Cs-137.
Liquid Chromatographic Analysis of Sucrose Polyester in Salad Dressing by Evaporative Light-Scattering Mass Detection
Authors: Chase G William , Akoh Casuvmr C , Eitenmiller Ronald R
Published: February 2020

A liquid chromatographic (LC) method is described for analysis of sucrose polyester (SPE) in salad dressings. SPE is separated from acylglycerols by gel permeation chromatography. The elution time window for SPE was determined with an evaporative light-scattering mass detector. The SPE fraction is collected and quantitated by C18 reversed-phase chromatography with a ternary gradient. The gradient consists initially of 45.5% methylene chloride, 52.5% acetonitrile, and 2.0% isopropyl alcohol. After 5 min, the ratios change to 98.0% methylene chloride and 2.0% isopropyl alcohol and remain unchanged for the next 6 min. The gradient then reverts back to initial conditions and is ready for another injection after a total run time of 17 min. Sucrose octaacetate was used as an internal standard to simplify quantitation. The mean (n = 3) recovery of SPE was 92.4 ± 2.6%. Reversed-phase LC precision was determined by performing 6 replicate analyses of Italian dressing. The mean recovery ± standard deviation and coefficient of variation were 261 ± 9.5 mg SPE/g and 3.6%, respectively.
Quantitation of Cyfluthrin in Liquid and Solid Formulations by Reversed-Phase Liquid Chromatography: Collaborative Study
Authors: Harbin Donald N
Published: February 2020

A liquid chromatographic (LC) method has been developed for quantitation of cyfluthrin (Baythroid®, Tempo®) in liquid and solid formulations. Cyfluthrin is a synthetic pyrethroid insecticide. Samples are dissolved in acetonitrile and analyzed by reversedphase LC with decanophenone as an internal standard. Seventeen laboratories from 7 countries participated in a collaborative study of the method. Each collaborator was provided with reference standard, internal standard, and matched pair samples of Tempo 20 wettable powder, Tempo 2 emulsifiable concentrate, and Tempo 2 flowable liquid formulations. Collaborators were instructed to use peak area measurements for quantitation. Relative standard deviations for reproducibility (RSDR) were 0.78,0.98, and 2.32, respectively. The LC method for determination of cyfluthrin in pesticide formulations has been adopted first action by AOAC INTERNATIONAL.
Determination of Ractopamine Hydrochloride in Swine and Turkey Tissues by Liquid Chromatography with Coulometric Detection
Authors: Turberg Michael P , Macy Thomas D , Lewis Jerry J , Coleman Mark R
Published: February 2020

A liquid chromatographic (LC) method is described for determination of ractopamine hydrochloride (LY031537) in swine and turkey tissues. Liver, kidney, muscle, and fat samples were homogenized in methanol. An aliquot of the extract was evaporated, diluted with water, and buffered to pH 10.5 ± 0.5 with sodium carbonate to convert ractopamine hydrochloride to a free base. The free base was extracted from the buffered sample with ethyl acetate. The extract was further purified on a Bond Elut acid-washed silica solid-phase extraction cartridge. After converting the free base back to the salt form with pH 4.5 buffer, analytical separation and quantitation of ractopamine hydrochloride was performed on an IBM C18 column with coulometric detection at +600 mV. The limit of detection of the method was approximately 0.5 ppb as determined in swine liver. Overall recovery levels ranged between 75 and 100% for samples of liver, kidney, muscle, and fat fortified at 1 to 100 ppb. The coefficients of variation ranged from 2 to 18% for samples fortified at 1 to 100 ppb.
Simultaneous Determination of Multiple Tetracycline Residues in Milk by Metal Chelate Affinity Chromatography: Collaborative Study
Authors: Carson Mary C , Breslyn Wayne ,   Collaborators:, Carmany J , Cross S , Farrington W H , Hahn A , Jaworski J , Lansdon P , Li M , Pearson D , Polli R , Shepherd E , Singh D , Sundlof S , Tieso T , Wagner R , Wentworth J , Wilson B
Published: February 2020

To meet federal and state regulatory needs, a liquid chromatographic (LC) method with ultraviolet (UV) detection was developed for determination of 7 tetracyclines at 30 ng/mL in milk. Raw milk samples are defatted, acidified, and centrifuged to remove proteins, and tetracyclines are specifically absorbed from the milk by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns. Tetracyclines are removed from these columns with EDTA-containing buffer, and extracts are further cleaned by ultrafiltration. Finally, extracts are concentrated and analyzed simultane ously by using on-line concentration. This method was validated in a collaborative study that involved 11 laboratories, including the authors’ laboratory. Each laboratory was asked to prepare and analyze known control and fortified milk samples, as well as 18 coded blind samples. Eight laboratories completed all analyses. Average interlaboratory recoveries for the known fortified samples ranged from 59% (methacycline at 15 ng/mL) to 78% (oxytetracy cline at 60 ng/mL). Average recovery for each of 7 residues at 30 ng/mL were between 60 and 110%, meeting single-residue guidelines for accuracy set by the U.S. Food and Drug Administration. Reproducibility relative standard deviation (RSDR) for the known fortified samples varied from 11 to 39%, with 6 of 7 residues at the 30 ng/mL level having RSDR values at or below 20%. Seven of 8 laboratories correctly identified blind control milk samples and all 28 residues present in blind samples. The metal chelate affinity—LC method for determination of multiple tetracycline residues in milk has been adopted first action by AOAC INTERNATIONAL.
Determination of D-Malic Acid in Apple Juice by Liquid Chromatography: Collaborative Study
Authors: Eisele Thomas A ,   Collaborators:, Adadevoh K , Anderson G , Brause A , Briesmeister D , Burke J , Cherix G , Ellis C , Hendricks S , Ho C T , Huang C J , Iuliano T , Kline L , Knapp C , Krueger D , Terwel L
Published: February 2020

Eleven laboratories collaboratively studied a liquid chromatographic (LC) method for determination of D-malic acid in apple juice. The mobile phase consisted of 16 mM L-valine and 8 mM copper acetate adjusted to pH 5.5 with NaOH. The UV detector was set at 330 nm, and a single reversed-phase LC column was used. Seven paired samples containing various amounts of D-malic acid ranging from 0 to 188 mg/100 mL of 12 Brix pasteurized apple juice were tested by each collaborator. Repeatability and reproducibility coefficients of variation ranged from 1.0 to 3.5% and 7.7 to 11.7%, respectively, within the range of 26 to 188 mg D-malic acid/100 mL of 12 Brix apple juice. The collabora tive study results demonstrated that the method could quantitate the economic adulteration of ap ple juice with DL-malic acid at lower levels than those reported with previous methods. The LC method for determination of D-malic acid in apple juice has been adopted first action by AOAC INTERNATIONAL.
Liquid Chromatographic Assay of Tylosin in Animal Feeds
Authors: Houglum Joel E , Tasler Mary K
Published: February 2020

A liquid chromatographic (LC) method is described for the assay of tylosin (tylosin A, tylosin B, and tylosin-urea adduct [TUA]) in animal feeds at approximately 4-200 g/ton. Samples are extracted with an equal mixture of methanol and 0.1 M pH 8 phosphate buffer. An acidic alumina column cleanup step is used prior to reversed-phase LC. Determination is accomplished with UV detection at 280 nm. A15 cm C8 column is used for sample concentration. Elution is performed at 1.5 mL/min with a gradient containing an increasing methanol concentration with 0.5% acetic acid and tetramethylammonium chloride (5 g/L) as the aqueous portion. Baseline separation of tylosin B, TUA, and tylosin A is achieved with retention times of approximately 7.4, 9.3, and 10.7 min, respectively. Conversion factors of 1.0 and 1.2 are used to convert peak areas of tylosin B and TUA, respectively, to tylosin A equivalent as an alternative to standards being used for these components of some feeds. The precision of the procedure ranged from a coefficient of variation (CV) of 1.6% for tylosin A at 94 g/ton to a CV of 11.3% for TUA at 10 g/ton. The average percent recovery of spiked feed extracts was100.4-102.2% for the 3 tylosin components. A correlation with the microbiological assay is presented for 12 feeds, 1 premix, and 1 injectable tylosin product.
Determination of Amoxicillin in Catfish and Salmon Tissues by Liquid Chromatography with Precolumn Formaldehyde Derivatization
Authors: Ang Catharina Y W , Luo Wenhong , Hansen Eugene B , Freemana James P , Thompson Harold C
Published: February 2020

A liquid chromatographic (LC) method with fluorescence detection was developed for analysis of amoxicillin in catfish and salmon tissues. The tissue was extracted with phosphate buffer (pH 4.5), followed by trichloroacetic acid (TCA) precipitation of proteins and solid-phase (C18) extraction. Trace amounts of nonpolar interfering substances present after solid-phase extraction were removed by ether liquid-liquid extraction. The extract was reacted with formaldehyde and TCA at 100°C for 30 min. A fluorescent derivative was extracted with ether, concentrated, and analyzed by reversed phase LC with fluorescence detection. Average recoveries of amoxicillin spiked at 2.5-20 ppb were >80% for catfish and >75% for salmon muscle tissue, with coefficients of variation of <6%. Limits of detection (LOD) and quantitation (LOQ) for catfish tissue were 0.5 and 1.2 ppb, respectively. LOD and LOQ for salmon muscle tissue were 0.8 and 2.0 ppb, respectively.
Determination of Benzocaine in Rainbow Trout Plasma
Authors: Bernardy Jeff A , Coleman Kathleen S , Stehly Guy R , Gingerich William H
Published: February 2020

A liquid chromatographic method is described for analysis of benzocaine (BZ), a proposed fish anesthetic, in rainbow trout plasma. Mean recoveries of BZ from plasma samples fortified at 44–10 100 ng/mL were 96–100%. The method detection limit is 10 ng/mL, and the limit of quantitation is 37 ng/mL. Acetylation of BZ occurs in whole blood after storage at room temperature (i.e., 21 °C) for 10 min. However, no acetylation of BZ was detected in plasma samples held at room temperature for 4 h. Mean method precision for plasma samples with incurred BZ residue is similar to that for fortified samples in the same concentration range (relative standard deviations of 0.9 and 1.2%, respectively).
Liquid Chromatographic Determination of Fumonisins B1, B2, and B3 in Corn: AOAC–IUPAC Collaborative Study
Authors: Sydenham Eric W , Shephard Gordon S , Thiel Pieter G , Stockenström Sonja , Snijman Petra W , Van Schalkwyk Dirk J ,   Collaborators:, Castegnaro M , Kamimura H , Lauren D R , Miller J D , Nawaz S , Pascale M , Pittet A , Savard M E , Schillack V R , Scudamore K , Sizoo E A , Smith W A , Stack M E , Ueno Y , Viljoen C C , Visconti A , van der Westhuizen L
Published: February 2020

A liquid chromatographic (LC) method for simultaneous determination of fumonisins B1 (FB1), B2 (FB2), and B3 (FB3) in corn was subjected to a collaborative study involving 12 participants from 10 countries, in which the accuracy and reproducibility characteristics of the method were established. Mean analyte recoveries from corn ranged from 81.1 to 84.2% for FB1 (at a spiking range of 500 to 8000 ng/g), from 75.9 to 81.9% for FB2 (at a spiking range of 200 to 3200 ng/g), and from 75.8 to 86.8% for FB3 (at a spiking range of 100 to 1600 ng/g). The valid data were statistically evaluated after exclusion of outliers. Relative standard deviations for within-laboratory repeatability ranged from 5.8 to 13.2% for FB1, from 7.2 to 17.5% for FB2, and from 8.0 to 17.2% for FB3. Relative standard deviations for between-laboratory reproducibility varied from 13.9 to 22.2% for FB1, from 15.8 to 26.7% for FB2, and from 19.5 to 24.9% for FB3. HORRAT ratios, calculated for the individual toxin analogues, ranged from 0.75 to 1.73. The LC method for determination of fumonisins B1, B2, and B3 in corn (at concentrations of 800–12800 ng total fumonisins/g) has been adopted by AOAC INTERNATIONAL.
Gas Chromatographic Determination of Propionic Acid and Sorbic Acid Contents of Rye Bread: Interlaboratory Study
Authors: Beljaars Paul R , Van Dijk Remmelt , Verheuen Peter J J , Anderegg Marcia J P T ,   Collaborators:, Bos H , van Dijk R , van Drunen G , van Ede K , Hoekstra A , Huijbregtse P A , Koopmans H , Koot Y , Ottink S , Rondags T M M , Schakel D
Published: February 2020

An interlaboratory study of the gas chromatographic (GC) determination of propionic acid and sorbic acid in rye bread was conducted. Homogenized test portions were extracted with a diethyl ether-phosphoric acid solution. Extracts were analyzed by capillary GC with flame ionization detection. Valeric acid and heptanoic acid were used as internal standards for propionic acid and sorbic acid, respectively. Six rye bread samples (3 blind duplicates) with propionic acid and sorbic acid at 3 concentration levels varying from 0.09 to 0.41% (w/w) were analyzed singly according to the proposed procedure by 11 laboratories. For all samples analyzed, repeatability relative standard deviations varied from 3.4 to 3.9% for propionic acid and from 1.7 to 3.0% for sorbic acid. Reproducibility relative standard deviations ranged from 5.0 to 8.0% for propionic acid and from 5.1 to 5.9% for sorbic acid. Average calculated recoveries from rye bread prepared from spiked dough were 100-101% for propionic acid and 101-106% for sorbic acid for 3 concentration levels.
Liquid Chromatographic Determination of Tocopherols and Tocotrienols in Margarine, Infant Foods, and Vegetables
Authors: Konings Erik J M , Roomans Harry H S , Beljaars Paul R
Published: February 2020

A liquid chromatographic (LC) method was developed for determination of tocopherols and tocotrienols in foods. Tocopherols and tocotrienols were released after saponification of test portions for 40 min at 80°C, followed by extraction with hexane-ethyl acetate. After evaporation of the organic solvents, the extract was injected into the LC system. Separation of individual tocopherols and tocotrienols was satisfactory. Some interferences were encountered from tocomoneols, tocodienols, 2-tert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol, (BHT), and plastochromanol-8. The response of the LC system was linear over a range of 0-10 μg/mL for tocopherols and tocotrienols. The detection limit for these compounds was 0.1 μg/mL. Repeatabilty relative standard deviation values for tocopherols and tocotrienols in margarine, infant formula, and broccoli (concentration range, 0.11-22 mg/100 g) varied from 1.3 to 6.4%. Recoveries ranged from 91 to 105%.
Comparison of Babcock and Ether Extraction Methods for Determination of Fat Content of Cream: Collaborative Study
Authors: Lynch Joanna M , Barbano David M , Fleming J Richard
Published: February 2020

A modified Mojonnier ether extraction method for determination of the fat content of cream was developed based on the method for milk (AOAC Official Method 989.05). The cream Babcock method (AOAC Official Method 920.111 B-C) was modified to harmonize with the milk Babcock method (AOAC Official Method 989.04) and to clarify procedural details. Using the AOAC collaborative study format, 10 laboratories tested 9 pairs of blind duplicate heat-treated cream samples with a fat range of 30-45% using both methods. The statistical performance (invalid and outlier data removed) was as follows: mean % fat = 37.932, sr = 0.125, sR = 0.151, RSDr = 0.330, RSDR = 0.398, r = 0.354, and R = 0.427 for the ether extraction method. For the Babcock method, mean % fat = 38.209, sr = 0.209, SR = 0.272, RSDr = 0.548, RSDR = 0.712, r = 0.592, and R = 0.769. Average test results for fat from the Babcock method were 0.277% (absolute fat) greater than for the Mojonnier ether extraction method. The difference between methods, as a percentage of the average fat content of the samples, was 0.73%. This agrees with differences observed between the 2 methods for milk when 10 to 17 laboratories tested 7 milk samples in blind duplicate at bimonthly intervals over a 4-year period (average difference 0.029% fat, 0.78% as a percentage of average fat content). The Mojonnier ether extraction and Babcock methods for fat in cream have been adopted by AOAC INTERNATIONAL. The new Babcock method replaced the AOAC Official Method 920.111 B-C.
Simultaneous Determination of 2,4-D, Dicamba, and Mecoprop in Soil Leachates by Gas Chromatography with Electron Capture Detection
Authors: Hong Moo-Ki , Kim Myung-Chul , Smith Albert E
Published: February 2020

Capillary gas chromatography (GC) with electron capture detection (ECD) and mass selective detection (MSD) was used for simultaneous determination of 2,4-dichlorophenoxyacetic acid (2,4-D), 3,6-dichloro-2-methoxybenzoic acid (dicamba), and (±)2-(4-chloro-2-methylphenoxy)propanoicacid (mecoprop) extracted from soil leachates. The 2,2,2-trif luoroethanol (TFE) esters of the acid analytes were synthesized by using H2SO4 as the catalyst. Efficiency of derivatization and instrumental molecular response were compared for herbicides methylated with boron trifluoride-methanol (14%, w/v), H2S04-methanol (33%, v/v), and diazomethane. The molecular integrity of TFE-2,4-D, TFE-dicamba, and TFE-mecoprop in the mixture was confirmed by GC-MSD. The TFE-esterification efficiency was maximized by adjusting the volume of H2SO4, the reaction time, and the reaction temperature. Optimal efficiency for the herbicide mixture was obtained by adding 1 m└ H2SO4 and 1 m└ TFE to the dried extract and allowing the reaction to proceed at 22�C for 8 h or by adding 0.5 m└ H2SO4 and 1 m└ TFE at 60°C for 120 min. Maximum esterification efficiency required an increased temperature and a decreased reaction time. The sensitivity of GC-ECD was about 2-20 times greater in determining TFE esters than in determining methyl ester derivatives. The herbicides were extracted simultaneously from soil leachates previously spiked with the analytes and esterified to TFE derivatives. Herbicide recovery, peak resolution, and detector sensitivity were excellent without column cleanup procedures.
Determination of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Fatty Fish by Tandem Solid-Phase Extraction Cleanup
Authors: Schenck Frank J , Calderon Lori , Podhorniak Lynda V
Published: February 2020

A rapid, multiresidue solid-phase extraction (SPE) technique for determination of organochlorine pesticide and polychlorinated biphenyl (PCB) residues in nonfatty fish was modified for use with fatty fish. In the modified procedures, samples are extracted with acetonitrile, and the extract is cleaned up with both C18 and Florisil SPE columns. Residues are determined by gas chromatography with electron capture detection. The original method was modified for use with fatty fish by reducing the amount of tissue extracted and by using an improved Florisil SPE cleanup. Recovery data are presented for 24 fortified organochlorine pesticide residues (0.12 ppm) and 3 fortified PCB residues (0.80 ppm) from flounder, bluefish, and shad samples, which contained 0.8,5.4, and 22.6% fat, respectively. For the 3 types of fish, recoveries of 23 of 24 fortified organochlorine pesticide residues ranged from 55 to 129%, and recoveries of 3 fortified PCB residues ranged from 55 to 104%. There were no significant differences in recovery based on fish species and/or fat content for the majority of residues studied. This SPE method and the official AOAC method yielded comparable results for fish containing incurred organochlorine residues.
Sources of Error in Vitamin A Analysis
Authors: Thiex Nancy , Smallidge Robert , Beine Robert
Published: February 2020

Potential sources of error in analysis of vitamin A in animal feed and pet food are discussed. Errors arising during sample handling and preparation and those due to standards, calibration, sample size, hydrolysis, extraction, evaporation, detection, equipment calibration, and isomerization are addressed. Quality control practices are recommended, and safety considerations are outlined. A summary of systematic and random errors is provided.
Rapid Quantitative Screening Assay of Trace Benzimidazole Residues in Milk by Liquid Chromatography
Authors: Fletouris Dimitrios , Botsoglou Nickos , Psomas Ioannis , Mantis Antonios
Published: February 2020

A simple, rapid, and sensitive liquid chromatographic (LC) assay for quantitative screening of albendazole 2-aminosulfone, albendazole sulfoxide, oxibendazole, oxfendazole, albendazole sulfone, p-hydroxyfenbendazole, albendazole, mebendazole, fenbendazole sulfone, and fenbendazole residues in milk was developed. Samples are made basic (pH 10) and extracted with ethyl acetate. Extracts are partitioned with water, evaporated to dryness, reconstituted with mobile phase, and analyzed isocratically by ion-pair reversed-phase LC at 292 nm. Overall recoveries ranged from 79 to 100%. Linearity was excellent in the fortification range examined (5.3–200 ng/mL). Precision data, based on within- and between-days variations, suggested an overall relative standard deviation of 2.0 to 5.8%. The method was successfully used to quantitate albendazole and fenbendazole and metabolites in milk from 2 drug-treated dairy cows.
Detection of DSP-Toxins, Okadaic Acid, and Dinophysis Toxin-1 in Shellfish by Serine/Threonine Protein Phosphatase Assay
Authors: Honkanen Richard E , Mowdy Don E , Dickey Robert W
Published: February 2020

A relatively rapid protein phosphatase-based assay was developed for detecting okadaic acid in extracts of shellfish, using oysters (Crassostrea virginica) as a model. The assay has good sensitivity, detecting okadaic acid in crude methanolic extracts of oysters at ≥4 ng/mL (≥0.1 ng/assay). Assay accuracy for detecting toxic shellfish was validated through a series of spike recovery experiments. In more than 320 assessments, all oysters containing toxic amounts of okadaic acid (≥0.2 μg/g) were detected. Results of analysis of the same extract by phosphatase assay and liquid chromatography gave very high correlation.
Stoichiometric Determination of Hydroperoxides in Oils by Fourier Transform Near-Infrared Spectroscopy
Authors: Dong Jun , Kangming Ma , Van De Voort Frederick R , Ismail Ashraf A
Published: February 2020

A rapid Fourier transform near-infrared (FT-NIR) spectroscopic method was developed for quantitative determination of the peroxide values (PVs) of edible oils. The method is based on the stoichiometric reaction of triphenylphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). Calibration standards were prepared by adding randomized amounts of TPPO and TPP to peroxide-free high-erucic-acid rapeseed (HEAR) to produce a calibration matrix spanning the concentrations of TPPO and residual TPP in oils having PVs in the range 0-100 after complete reaction of the hydroperoxides with added TPP. A partial-least-squares (PLS) calibration model for predicting PV was developed by using the NIR spectral region from 4710 to 4540 cm-1, where TPP and TPPO both absorb. The resulting PLS calibration was linear, the cross-validation having a standard deviation (SD) of 1.36 PV over the analytical range. The method was validated by comparing the PLS-predicted PVs of oils spiked with tert-butyl hydroperoxide (TBHP) and those of naturally oxidized HEAR oils with the results obtained by using the American Oil Chemists’ Society (AOCS) iodometric procedure. The FT-NIR PV method correlated very well (SD = 1.20) with the reference AOCS method for TBHP-spiked oil samples. Similar results were obtained for naturally oxidized HEAR oil, with a standard deviation of the difference for reproducibility of ±1.11 PV for both methods. The analysis consists of adding about 0.04 mL TPP stock solution to 1 g oil, shaking, recording the spectrum, and using the PLS calibration to predict PV. Because of its simple and rapid stoichiometric reaction and its excellent correspondence to the iodometric method, the FT-NIR method provides a simple and alternative means of measuring PV. The FT-NIR method avoids the solvent and reagent disposal problems associated with the AOCS method and can be readily auto mated by appropriate programming of the FTIR spectrometer. Thus, it provides a simple and rapid analytical technique for determining PVs of fats and oils.
Enzyme Immunoassay for Direct Determination of Microcystins in Environmental Water
Authors: Nagata Satoshi , Tsutsumi Tomoaki , Hasegawa Akihiro , Yoshida Fuyuko , Ueno Yoshio , Watanabe Mariyo F
Published: February 2020

An enzyme-linked immunosorbent assay (ELISA) was developed for direct quantitation of microcys- tins (MCs), a group of freshwater cyanobacterial toxins. An anti-MC monoclonal antibody exhibiting broad cross-reactivity to major MC derivatives was used. The detection limit and linear range of the ELISA standard curve with microcystin-(leucine-ar-ginine) (MCLR), a variant of MCs, were 20 and 20–500 pg/mL, respectively. For analysis of MC released from cyanobacterial cells, water sample filtered through a glass fiber filter was applied directly to ELISA. For analysis of total MC (released MC plus intracellular MC), intracellular toxin was extracted by freeze-thawing twice before filtration. Mean recovery of MCLR added to tap water and toxin-free environmental water was 101%, with a coefficient of variation (CV) of 7.3% at toxin levels of 20–500 pg/mL. Mean recovery of MCLR added to toxin-free cyanobacterial extracts was 93%, with a CV of 12.5% at toxin levels of 50–500 pg/mL. At 20 pg/mL, an increasing matrix effect on assay variance was observed; therefore, both released MC and total MC were measured in the range 50–500 pg/ mL. Comparative studies with a liquid chromatographic (LC) method showed that the ELISA gives a reliable correlation with LC for analysis of MC in water extracts of natural blooms and cultured cyanobacterial cells (r = 0.98). The ELISA was applied to water samples collected from lakes and ponds in Japan. In 4 of 13 and 12 of 17 samples, 81–800 pg released MC/mL and 64–94 000 pg total MC/mL were detected, respectively. By LC separation followed by the ELISA analysis, the presence of MCLR, microcystin-arginine-arginine, and micro-cystin-tyrosine-arginine were confirmed in 4 ELISA-positive samples selected randomly. The newly developed ELISA is a reliable and powerful method for mass monitoring of MC levels in environmental water.