bluuebunny/crossref_metadata_2025 huggingface dataset:
Taurine Analysis in Milk and Infant Formulae by Liquid Chromatography: Collaborative Study
Authors: Woollard David C , Indyk Harvey E ,   Collaborators:, Angyal G , Borbon J , Chase W , Coors U , Davis P , Edwards M , Ellis C , Gore W , Gossard J , Hischenhuber C , Jagodic M , Kerr M , Kmec D , McMahow A , Myers M , Rajamohan R , Saito K , Sullivan D , Tsalkani N , Walker E , Welton K , Wo C , Zaugg S
Published: February 2020

A collaborative study was conducted on a liquid chromatographic (LC) method for determination of taurine in infant formula and milk powders. Twenty laboratories participated in the analysis of 8 blind duplicates over the range of approximately 3–60 mg/100 g sample. The method involved protein removal, conversion to the dansyl-derivative, and isocratic LC separation with UV and/or fluorescence detection. Following outlier treatment, overall mean RSDR has been estimated at 7.00% for sup. plemented products with a HORRAT value of 1.1. The poorer precision at endogenous levels establishes a lower limit of determination of about 5 mg/100 g. An overall mean RSDr:RSDR value of 0.7 for all products demonstrated acceptable performance.
Gas Chromatographic Determination of Cyprodinil, Fludioxonil, Pyrimethanil, and Tebuconazole in Grapes, Must, and Wine
Authors: Cabras Paolo , Angioni Alberto , Garau Vincenzo L , Minelli Elizabeth V
Published: February 2020

A rapid and simple gas chromatographic method for determinating cyprodinil, fludioxonil, pyrimethanil, and tebuconazole in grapes, must, and wine is described. An on-line microextraction method was used with a one-step extraction–partition procedure. Nitrogen–phosphorus and mass spectrometric detectors were used, because of their low sensitivity and high selectivity. Because of high selectivity of detector, no cleanup was necessary and the extract was concentrated 5 times. Recoveries from fortified grapes, must, and wine ranged from 93 to 110%. Limits of determination were 0.05 mg/kg for cyprodinil and pyrimethanil and 0.10 mg/kg for fludioxonil and tebuconazole.
International Proficiency Testing of Analytical Laboratories for Foods and Feeds from 1990 to 1996: The Experiences of the United Kingdom Food Analysis Performance Assessment Scheme
Authors: Key Pauline E , Patey Alan L , Rowling Simon , Wilbourn Anne , Worner Fiona M
Published: February 2020

The Food Analysis Performance Assessment Scheme (FAPAS) organized by a Secretariat of the UK Ministry of Agriculture, Fisheries, and Food has checked the proficiency of analytical laboratories for foods and feeds from 1990 to 1996. FAPAS was started for UK laboratories but was expanded worldwide at the request of analysts in other countries who did not have a home-based scheme. Thirteen thousand homogeneity-checked test materials were issued, covering a very wide range of analytes, including pesticides, toxins, veterinary drug residues, trace and nutritional elements, food colors, preservatives, sweeteners, alcohol congeners, fatty acids, nitrate, and proximate analysis. Participants returned 85% of requested data, and 47 000 z- score proficiency assessments were made, of which 81% were satisfactory. Evidence is presented of improvements in overall analytical ability with increased participation in proficiency testing in the areas of proximate analysis; organochlorine pesticide analysis; and lead, mercury, and acesul- fame-K analyses. Little improvement was shown in other analytical areas such as calcium analysis. Overall accuracies for analysis of specific pesticides and specific trace elements in the circulated test materials were compared.
New Trends in Food Microbiology: an AOAC INTERNATIONAL Perspective
Authors: Andrews Wallace H
Published: February 2020

The paper discusses 5 major trends in food microbiology from an AOAC INTERNATIONAL perspective. The first trend, and perhaps the one with the greatest impact on food microbiology during the past 10 years, is the introduction of the rapid test kit. The development of these kits is a result of attempts to expedite, simplify, miniaturize, and automate methods. The second trend is the introduction of new method validation programs. AOAC INTERNATIONAL offers 2 alternatives to method validation by collaborative study: the Test Kit Performance Tested Method Program and the Peer-Verified Method Program. The third trend is the increasing use of microbiological reference materials. Applications of reference materials and of certified reference materials is addressed. The fourth trend is the evolving international character of not just AOAC INTERNATIONAL but other recognized scientific organizations as well. An attempt at method harmonization is one important consequence of this evolving internationalism. Moreover, there is a growing trend toward sharing of microbiological expertise on a global scale, reflecting our ever-shrinking geographical differences. The fifth trend is the implementation and increasing use of the Hazard Analysis Critical Control Point (HACCP) concept. The nature of the HACCP program and its influence on microbiological testing of the finished product are described.
Fructans in Foods and Food Products, Ion-Exchange Chromatographic Method: Collaborative Study
Authors: Hoebregs Hubert ,   Collaborators:, Balis P , De Vries J , Eekelen J v , Farnell P , Gray K , Goedhuys B , Hermans M , Heroff J , van Leeuwen M , Li B W , Martin D , Pieters M , Quemener B , Roomans H , Slaghek T , Thibault J-F , van der Waal W , de Wit D
Published: February 2020

Nine collaborating laboratories assayed 6 blind duplicate pairs of food samples containing the fructans inulin or oligofructose. The 6 sample pairs ranged from low (4%) to high levels (40%). Following the proposed method, the samples were treated with amyloglucosidase and inulinase enzymes and the released sugars were determined byion exchange chromatography. Repeatability standard deviation ranged from 2.9 to 5.8%; reproducibility standard deviation ranged from 4.7 to 11.1%. The ion-exchange chromatographic method for determinationof fructans in food and food products has been adopted first action by AOAC INTERNATIONAL (997.08)
Performance Evaluation of Direct Forced-Air Total Solids and Kjeldahl Total Nitrogen Methods: 1990 through 1995
Authors: Lynch Joanna M , Barbano David M , Healy Patrick A , Fleming J Richard
Published: February 2020

Results from collaborative studies of the performance of the direct forced-air oven-drying method for determination of milk total solids content (AOAC Method 990.20) and the Kjeldahl total nitrogen method for determination of milk total nitrogen content (AOAC Method 991.20) were published in 1989 and 1990, respectively. Method performance was characterized by using the harmonized ISC7IUPAC/ AOAC guidelines for method validation, and the methods now have final action status. During1990 through 1995, the split sample collaborative study format was used to monitor the performance of these methods as part of a multilaboratory quality assurance program. Seven blind duplicate milk materials were sent from a central laboratory onceevery 2 months to participating laboratories. Data were analyzed with the same statistical procedures used in the original collaborative studies. Compared with the original collaborative study, the repeatability and reproducibility of the oven-drying method improved over time. For the Kjeldahl total nitrogen method, within-laboratory repeatability improved slightly, whereas between-laboratory reproducibility was similar to but not always as good as in the original study. The results demonstrate that the statistical protocol for collaborative studies can be used effectively as the basis for a multilaboratory quality assurance program and that the method performance achieved in a collaborative study can be maintained and even improved with time.
Determination of Residues of Alachlor and Related Herbicides in Crops by Liquid Chromatography with Electrochemical Detection
Authors: Nortrup David A
Published: February 2020

A method is described for determining residues of 3 acetamide herbicidesalachlor [2-chloro-N(2,6- diethylphenyl)-N(methoxymethyl)acetamide], acetochlor [2-chloro-N(2-ethyl-6-methylphenyl)-N (ethoxymethyl)acetamide), and butachlor [2-chloro-N(2,6-diethylphenyl)-N(butoxymethyl)- acetamide)by liquid chromatography (LC). Currently no published method determines metabolites from all 3 herbicides in crops. Strong-base hydrolysis after extraction of a test portion with water-acetonitrile results in the formation of 2,6- diethylaniline (DEA) and 2-(1-hydroxyethyl)-6-ethylaniline from alachlor metabolites, 2-ethyl-6-methylaniline and 2-(1-hydroxyethyl)-6-methylaniline from acetochlor metabolites, and DEA from butachlor. The anilines are isolated by steam distillation, partitioned with Supelclean ENVI-Chrom P solid-phase extraction columns, and methylated prior to LC analysis. The limit of quantitation of aniline moieties is about 0.01 ppm. Recoveries of 0.01- 0.40 ppm aniline moieties are generally 74-103%, with relative standard deviations of 2.2 to 14.0%.
Liquid Chromatographic Method for Determining the Concentration of Bisazir in Water
Authors: Scholefield Ronald J , Slaght Karen S , Allen John L
Published: February 2020

Barrier dams, traps, and lampricides are the techniques currently used by the Great Lakes Fishery Commission to control sea lampreys {Petromyzon marinug) in the Great Lakes. To augment these control techniques, a sterile-male-release research program was initiated at the Lake Huron Biological Station. Male sea lampreys were sterilized by intraperitoneal injection of the chemical sterilant P,P-bis(1-aziridinyl)-Nmethylphosphinothioic amide (bisazir). An analytical method was needed to quantitate the concentration of bisazir in water and to routinely verify that bisazir (>25 μg/L) does not persist in the treated effluent discharged from the sterilization facility to Lake Huron. A rapid, accurate, and sensitive liquid chromatographic (LC) method was developed for determining bisazir in water. Bisazir was dissolved in Lake Huron water; extracted and concentrated on a C18 solid-phase extraction column; eluted with methanol; and quantitated by reversed-phase LC using a Cis column, amobile phase of 70% water and 30% methanol (v/v), and UV detection (205 nm). Bisazir retention time was 7-8 min; total run time was about 20 min. Method detection limit for bisazir dissolved in Lake Huron water was about 15 μg/L. Recovery from Lake Huron water fortified with bisazir at 100 μg/L was 94% (95% confidence interval, 90.2-98.2%).
Comparative Study of Colorimetric and Fully Automated Enzyme-Linked Immunoassay System for Rapid Screening of Listeria spp. in Foods
Authors: Kerdahi Khalil F , Istafanos Philip F
Published: February 2020

Two enzyme-linked immunoassay (ELISA) systems for rapid screening of Listeria spp. were compared for their use in analysis of spiked foods regulated by the U.S. Food and Drug Administration. The Tecra Listeria kit is a 48 h visual ELISA that detects Listeria spp. through colorimetry. It has been approved for first action by AOAC INTERNATIONAL.The Vitek immunodiagnostic assay system for Listeria (\i\D AS LIS) is a fully automated 48 h ELISA that detects Listeria spp. by immunofluorescence. Fifty-two food samples were artificially contaminated with high (11-42 colony-forming units [cfu]/25 g food) and low (2-8 cfu/25 g food) levels of L monocytogenes and screened by the 2 protocols. Unspiked samples were also assayed as negative controls. Six unspiked samples werefound positive for Listeria spp. by both methods: 3 were identified as L. monocytogenes and 3 as L. innocua by official methods. Both ELISA methods detectedall spiked samples. One unspiked sample was assayed positive by Tecra and negative by VIDAS LIS. No Listeria spp. were recovered when the sample was tested by the conventional method. Nointerference due to background fluorescence of food matrixes was observed in the VIDAS LIS method. Results suggest a modified VIDAS LIS preenrichment medium may be used in place of the VIDAS standard medium in the protocol.
Stability of Sulfonamide Antibiotics in Spiked Pig Liver Tissue During Frozen Storage
Authors: Thomas George K , Millar Roderick G , Anstis Peter W
Published: February 2020

A bulk portion of homogenized pig liver tissue was spiked at room temperature with 0.2 mg/kg (twice the Australian maximum residue limit) of each of sulfathiazole, sulfachlorpyridazine, sulfadimidine (sulfamethazine), sulfaquinoxaline, and sulfadimethoxine. After subsampling and packaging, selected individual packaged units were tested to confirm homogeneity of the prepared material. The material was stored frozen at -20°C and analyzed in replicate by liquid chromatography on 11 sampling dates over a period of about 6 months. Analytical data were plotted on a log-linear scale and subjected to linear regression on the basis of firstorder kinetics for the decay. Storage stabilities (decay half-lives at -20°C) calculated from the mean slope of regression lines were sulfadimethoxine, 567 days; sulfadimidine, 457 days; sulfachlorpyridazine, 312 days; sulfathiazole, 291 days; and sulfaquinoxaline, 271 days. Significant depletion (65% loss) of residue was observed for sulfaquinoxaline during preparation of spiked bulk liver tissue. An extension of the study to measure the storage stability of sulfaquinoxaline under accelerated decay conditions (refrigerator temperature, 4°C) showed it to be relatively unstable, with a decay half-life of 11 days. Results demonstrate the need for both regulatory agencies and testing laboratories to be aware of potential errors associated with improper transport, storage, and handling of tissue samples submitted for antibiotic testing.
Determination of Tilmicosin in Bovine and Porcine Sera by Liquid Chromatography
Authors: Moran John W , Turner James M , Coleman Mark R
Published: February 2020

A liquid chromatographic (LC) assay is described for determining tilmicosin in bovine and porcine blood sera. Tilmicosin is isolated from the serum matrix and purified by solid-phase extraction with C18 sorbent. Sample is analyzed by LC using a gradient system with a phenyl reversed-phase column that separates tilmicosin from the matrix in 30 min. Tilmicosin is measured by UV absorbance at 280 nm. Validation of assay included evaluation of accuracy, precision, linearity, specificity, sensitivity, range, and sample stability. The method has a limit of quantitation of 0.1 ppm and a validated range of 0.1 to 10.0 ppm. Recoveries were 91–95% for bovine serum and 85–93% porcine serum. The limit of detection was 0.05 (μg/mL. Limits of detection and quantitation were based on 3 and 6 times the baseline noise of control serum samples, respectively. Relative standard deviations of precision samples (n = 6) were 2% or less for both sera. The method has better specificity and analysis time than previous microbiological methods for tilmicosin in sera.
Survival and Detection of Shigella flexneri in Vegetables and Commercially Prepared Salads
Authors: Rafii Fatemeh , Lunsford Pamala
Published: February 2020

The normal bacterial microflora of 4 commercially prepared salads (coleslaw, crab salad, carrot salad, and potato salad) and 3 vegetables (green pepper, onion, and cabbage) were evaluated. Twenty-eight species of bacteria, including potential pathogens, were isolated. The foods were artificially inoculated with an avirulent mutant strain of Shigella flexneri 5 (pHS1059) to develop a method for the rapid detection of Shigella spp. Bacteria were separated from insoluble and particulate salad ingredients by filtration through shark skin filter paper and by low speed centrifugation. S. flexneri survived at 4°C in all salads for at least 11 days and up to 20 days in crab salad. The polymerase chain reaction (PCR), using primers for amplification of a 118-base pair DNA fragment from the virulence-associated spa region, present in all Shigella spp., was used to detect S. flexneri in filtrates from salads inoculated with S. flexneri 5 (pHS1059). DNA was amplified from all of the artificially contaminated salads and vegetables except green pepper. After 3–5 days of storage, the PCR also amplified S. flexneri DNA from salads that had been enriched with nutrients to increase the number of bacteria. Green peppers contained a PCR inhibitory substance that was attenuated by dilution and enrichment before the PCR. No amplification of DNA was observed in foods to which S. flexneri had not been added.
Effects of Salt and Serum on the Sporicidal Activity of Liquid Disinfectants
Authors: Sagripanti Jose-Luis , Bonifacino Aylin
Published: February 2020

This study compares the effects of various concentrations of salt or serum in the killing of Bacillus subtilis spores by either glutaraldehyde, sodium hypochlorite, cupric ascorbate, hydrogen peroxide, peracetic acid, formaldehyde, or phenol. Salt affected only glutaraldehyde, its sporicidal activity increasing with an increase in concentration of sodium bicarbonate or sodium chloride. The sporicidal activity of glutaraldehyde was minimal when the concentrations of aldehyde groups and lysine residues from protein were similar. We present an equation describing the effect of serum on spore survival as a function of glutaraldehyde concentration that fits the data with a regression coefficient of 0.9. Cupric ascorbate and peracetic acid were inhibited by serum, but this effect was linked to a rise in pH. Sodium hypochlorite was the agent most sensitive to protein, with its sporicidal activity nearly disappearing in the presence of 2% serum or an equivalent amount of purified protein.
Supercritical Fluid Extraction of Polychlorinated Biphenyls and Organochlorine Pesticides from Freeze-Dried Tissue of Marine Mussel, Mytilus eduli
Authors: Yoo Wesley J , Taylor Larry T
Published: February 2020

Supercritical fluid extractions (SFEs) of 21 polychlorinated biphenyls (PCBs) and 8 organochlorine pesticides (OCPs) from freeze-dried mussel tissue are compared with traditional Soxhlet extractions. The aim was to determine the efficacy of supercritical CO2 to extract these 2 classes of lipophilic compounds. A spike study to determine the feasibility of on-line cleanup by inclusion of an inert matrix (activated alumina) in the extraction vessel showed that the chemical integrity of the PCBs was not compromised, whereas some DDTs were decomposed to their respective metabolites. Relatively long static extraction time, higher density, and lower temperature yielded quantitative recoveries of PCBs from freeze-dried mussel tissue with good reproducibilities. Recoveries of OCPs were nonquantitative and highly variable. Finally, the efficacy of fluoroform (CHF3) as an alternative supercritical fluid to selectively extract PCBs and OCPs was studied. Fluoroform yielded nonquantitative and variable recoveries of PCBs and OCPs, but its use eliminated the need for in situ alumina to retain coextracted lipids from the matrix.
A Bridging Study Between Liquid Chromatography and Microbial Inhibition Assay Methods for Determining Amoxicillin Residues in Catfish Muscle
Authors: Ang Catharina Y W , Luo Wenhong , KiessLing Connie R , Mckim Karen , Lochmann Rebecca , Walker Calvin C , Thompson Harold C
Published: February 2020

A bridging study was conducted to establish the correlation between a liquid chromatographic (LC) method and a microbial inhibition (Ml) method for analysis of amoxicillin residues in catfish muscle. The LC procedure involved precolumn derivatization with formaldehyde followed by LC separation with fluorescence detection. The Ml procedure used Bacillus stearothermophilus as the test organism and was validated in this study before the bridging investigation. The 2 methods were compared for determination of both fortified and incurred samples. No significant differences were found between the methods when all data were included in statistical computations. The linear correlation of LC means versus Ml means had a slope of 0.972 and a negligible intercept (1.0 ng/g), with a correlation coefficient of 0.9962. LC was more specific and showed better sensitivity than Ml for amoxicillin residues at ≤10 ng/g. For practical purposes, values obtained by the 2 methods can be considered equivalent.
X-Ray Fluorescence Determination of Manganese in FD&C Blue No. 1
Authors: Hepp Nancy M
Published: February 2020

An X-ray fluorescence (XRF) method was developed for determining manganese in FD&C Blue No. 1 from simply prepared pressed pellets. Results were compared with those of atomic absorption spectroscopy (AAS) of acid-digested or ashed samples. Levels of manganese determined by XRF and AAS were equivalent. The limit of detection (3σ) for the XRF method was 3µg manganese/g dye. The 95% confidence interval at the specification level was 100 ± 10 μg manganese/g dye
Direct 24-Hour Presumptive Enumeration of Escherichia coli 0157:H7 in Foods Using Hydrophobic Grid Membrane Filter Followed by Serological Confirmation: Collaborative Study
Authors: Entis Phyllis ,   Collaborators:, Bryant D , Bryant J , Bryant R G , Inami G , Cholensky J S , Garcia G R , Ramsey S M , Courtney T , Pruett W P , Dagdag E B , Davis-DeBella P E , San Diego , Humes L M , Lau D , Watson J , Erickson J , Hayes M , Ingham S , Sage J , Jirele K , Zuroski K , Kelley G , Lerner I , Patel D R , Peery D A , Simpso S , Zachary C
Published: February 2020

abstract

Fifteen laboratories took part in a collaborative study to validate a method for enumerating Escherichia coli 0157:H7. The method is based on use of a hydrophobic grid membrane filter and consists of 24 h presumptive enumeration on SD-39 Agar and serological confirmation to yield a confirmed E. coli 0157:H7 count. Six food products were analyzed: pasteurized apple cider, pasteurized 2% milk, cottage cheese, cooked ground pork, raw ground beef, and frozen whole egg. The test method produced significantly higher confirmed count results than did the reference method for milk, pork, and beef. Test method results were numerically higher than but statistically equivalent to reference method results for cheese, cider, and egg. The test method produced lower repeatability and reproducibility values than did the reference method for most food/inoculation level combinations and values very similar to those of the reference method for the remaining combinations. Overall, 94% of presumptive positive isolates from the test method were confirmed serologically as E. coli 0157:H7, and 98% of these were also biochemically typical of E. coli 0157:H7 (completed test). Corresponding rates for the reference method were 69 and 98%, respectively. On the basis of the results of this collaborative study and the precollaborative study that preceded it, it is recommended that this method be adopted official first action for enumeration of E. coli 0157:H7 in meats, poultry, dairy foods, infant formula, liquid eggs, mayonnaise, and apple cider
Stability of Organic Pollutants During Microwave-Assisted Extraction from Solid Matrixes
Authors: Lopez-Avila Viorica , Young Richard , Beckert Werner F
Published: February 2020

abstract

A stability study was conducted for 95 semivolatile organics listed in U.S. Environmental Protection Agency Method 8250 (this number includes 6 surrogate compounds). These compounds were spiked into solvent only [hexane-acetone (1 +1), methylene chloride-acetone (1 +1), toluenemethanol (10 + 1), and methyl ferf-butyl ether], solvent/dry soil suspensions, and solvent/wet soil suspensions [20% water (w/w)] and heated with microwave energy in closed vessels at 50° or 145° C for 5 or 20 min. For comparison and to determine nitrogen blowdown losses, spiked solvent samples that had not been exposed to microwave energy were concentrated by the blowdown technique and analyzed for each of the spiked compounds. Hexane-acetone (1+1) seems to be the best for the compounds and matrixes investigated, with recoveries > 80%, except for basic compounds and benzoic acid in the solvent/dry soil suspension experiments. Increasing extraction time from 5 to 20 min did not increase recoveries; in fact, recoveries of neutral compounds decreased slightly at the longer extraction time. Increasing the temperature from 50° to 145° C decreased recoveries of basic compounds by about 10%. Recoveries of basic compounds, of benzoic acid (and probably other organic acids as well), and at least to some extent of phenolic compounds from the solvent/wet soil suspensions were higher than those for solvent/dry soil suspensions.
Solid-Phase Extraction Cleanup for Ivermectin in Liver Tissue
Authors: Reising Kyle P , Benedetto Nrffer Migdal Di
Published: February 2020

abstract

Extraction of liver tissue with organic solvent produces coextractants with compounds of interest. The solid-phase extraction (SPE) cleanup of liver tissue developed for ivermectin removes nonpolar coextractants. Liver extract that has been reduced to dryness is reconstituted in 0.5 mL acetonitrile. The mixture is passed through 0.1 g C18 SPE column, and the eluate is collected. The column is eluted further with 2 mL acetonitrile. Combined eluates are derivatized with 1-methylimidazole and trifluoroacetic anhydride, and the ivermectin derivative is determined by liquid chromatography with fluorescence detection.
Occurrence of β2- Adrenergic Agonist Residues in Urine of Animal Meat Producers in Portugal
Authors: Ramos Fernando , Castilho M Conceicāo , Da Silveira M Irene Noronha
Published: February 2020

abstract

Between January 1,1991, and December 31,1993, bovine urine was collected for analysis of β2-adrenergic agonist residues. A multiresidue method was developed that was capable of detecting clenbuterol, clenpenterol, clenproperol, mabuterol, mapenterol, bromobuterol, tulobuterol, and salbutamol through enzyme-linked immunosorbent assay, liquid chromatography (LC) with photodiode array detection, and gas chromatography with mass detection in electron impact mode with selective-ion monitoring. Among 1031 samples, 24 contained clenbuterol and 1 contained salbutamol. The results confirm that clenbuterol is the β2-adrenergic agonist most used as bovine growth promoter in Portugal.
Comparison of Six Methods for Determining Aged Phosphine Residues in Wheat
Authors: Allen Sylvia E , Ren Yong-Lin , Desmarchelier James M
Published: February 2020

abstract

Phosphine (PH3) residues on wheat were determined by gas chromatography (GC) in a blind experiment using 6 methods to assess whether results from different methods are comparable. For one method, 2 different chromatographic conditions also were used. Samples were fumigated for 7 days and aired for 2 or 7 days to obtain "aged" residues. The methods involved determination of PH3 in the headspace over aqueous acidified acetone plus wheat (method a), over ground wheat (method b), over ground wheat plus headspace concentrations over ground wheat in acetone after transfer to another flask (method c), over ground wheat in acetone (method d), over whole wheat after microwave heating (method e), and over water after dilution of 0.5 ml_ aqueous acetone leachate with 10 ml_ buffered sodium sulfate solution (method f). For each method, gas-tight flasks and syringes were used. Data to support new methods c, d, and f are discussed. Each procedure correctly identified the order of PH3 residues as highest, medium, and absent. Quantitative results from all methods were similar, except that results from method b were on average 44% lower than the average results from other procedures. Thus each method, except method b, is suitable for determination of PH3 residues. The relative advantages of each procedure are discussed.
Use of AOAC INTERNATIONAL Method Performance Statistics in the Laboratory
Authors: Lynch Joanna M
Published: February 2020

abstract

Method performance statistics are included with many AOAC methods and are estimates of precision or variability. These statistics can provide useful guidelines as to the degree of precision that can be achieved when a method is used routinely. Indeed, defining method performance in a practical, meaningful, and standardized way is one of the goals of the AOAC Official Methods program. This paper gives some guidelines for understanding and interpreting AOAC method performance statistics for practical use in the laboratory
Uncertainty—A Chemist's View
Authors: Horwitz William
Published: February 2020

Complete characterization of the performance of analytical methods requires an evaluation of the halo of uncertainty bracketing the reported result. Achieving a satisfactory estimate of this uncertainty is more important than how this estimate is produced. Enumeration of all conceivable error components—the so-called error budget approach— is one way to estimate the uncertainty, but it is not the only way. In fact, when applied to analytical chemistry this approach is likely to (1) overlook important variables and double count others, {2) avoid considering unknown and unknowable interactions and interferences, and {3) adjust for missing variables with an uncontrollable "Type B" component. The problem is one of experimental design. Alternative and more efficient ways of estimating uncertainty in analytical chemistry include the Youden ruggedness procedure, accompanied by a bonus of optimization, and the all-encompassing interlaboratory method-performance trial.
Repeatability and Reproducibility Estimates from Collaborative Studies Based on Total Concentration of Trace Analytes
Authors: Mcclure Foster D
Published: February 2020

In the process of validating a given analytical method for the total concentration of a trace analyte, the precision indicators, repeatability and reproducibility, are obtained from a collaborative study of the method based on a standard one-way completely randomized model. This report discusses the shortcomings of the statistical models used in such studies, defines the component makeup for estimates of the repeatability and reproducibility variances based on these models, and considers suggestions offered as new policy regarding method performance based on total concentration.
Specificity of the BAX Polymerase Chain Reaction System for Detection of the Foodborne Pathogen Listeria monocytogenes
Authors: Stewart Diana , Gendel Steven M
Published: February 2020

The polymerase chain reaction (PCR) can be used for rapid and specific detection of foodborne pathogens. One commercial kit, the Qualicon BAX system uses PCR to detect Listeria monocytogenes in enrichment cultures derived from food and environmental samples. The specificity and sensitivity of the BAX system for detecting L. monocytogenes were characterized by using both pure and mixed cell cultures, and optimal conditions for production of cell lysates were determined. The BAX system was highly specific for L. monocytogenes, and no interference was seen in the presence of either other Listeria species or microbes from other genera. The assay detected L. monocytogenes at 105- 106 colony-forming units/mL. This sensitivity is adequate for detecting viable cells after enrichment but prevents false-positive signals from nonviable cells.
Liquid Chromatographic Determination of Ivermectin in Feed
Authors: Doherty Stephen J , Fox Allen , Fink David W
Published: February 2020

An analytical method for determining ivermectin in feed at 0.50- 3 ppm is presented. The method is based on liquid chromatographic measurement after sample preparation by adsorption chromatography on alumina and solid-phase extraction. Two complete, final, finished medicated feeds and the corresponding control feeds used in their preparation were analyzed. Recoveries from feeds fortified at 50-150% of the 2 ppm ivermectin use concentration also were determined. Mean recoveries from replicate analyses ranged from 90 to 100%, and coefficients of variation (CVs) were less than 4.5%. No significant interferences were found in control feeds. The pooled distribution of individual analytical results (n = 100) gave a mean recovery of 100%, a recovery range of 90-111%, and an overall CV of 5.5%. Resolution of the total variance into its 2 components gave a withinlaboratory CV of 4.1% and a between-laboratory CV of 3.4%. There was no significant difference in recoveries among laboratories, days, concentrations, and feed base or between fortified and medicated feeds (P > 0.2)
Liquid Chromatographic Determination of Five Benzoylurea Insecticides in Fruit and Vegetables
Authors: Gamón Miguel , Saez Adolfo , Pelegrí Rosa , Peris Inmaculada , De La Cuadra Josá G , Coscollá Ramón
Published: February 2020

A liquid chromatographic (LC) method was developed to determine 5 benzoyl ureas—diflubenzuron, hexaflumuron, teflubenzuron, flufenozuron, and lufenuron—in peppers, tomatoes, eggplants, cucumbers, and oranges. Preparation of samples involve extraction with acetone and partitioning into dichloromethane-petroleum ether. A portion of this extract is cleaned up with a solid-phase extraction aminopropyl disposable column. With LC analysis using an RP-8-DB microbore column, acetonitrilewater (70 + 30, v/v) as mobile phase, and photodiode array detection at 254 nm, recovery and repeatability data were collected for the 5 benzoylureas on 4 vegetables and citrus in the range 0.04-2.0 mg/kg. Validated limits of detection and quantitation were 0.01 and 0.04 mg/kg, respectively. The method is reliable for routine analysis of vegetables and fruits
Double Calibration (External Calibration and Stable Isotope Dilution) for Determining Selenium in Plant Tissue by Hydride Generation Inductively Coupled Plasma Mass Spectrometry
Authors: Zhang Ling-Su , Combs Sherry M
Published: February 2020

Both external calibration (EC) and stable isotope dilution (SID) calibration are reliable methods for determining selenium by hydride generation inductively coupled plasma mass spectrometry (HG-ICP-MS), but they are rarely used simultaneously. Because these methods are independent of each other, they could be used simultaneously to test each other and to evaluate data quality directly. A double calibration approach using EC and SID simultaneously was developed to evaluate data quality directly for analysis of Se in plant tissue by HG-ICP-MS. Natural Se was used for EC. 77Se-enriched Se (0.004 μg; 77Se = 94.38%) was spiked to 0.5 g sample for SID (78Se or 82Se isotope used as reference isotope). Sample preparation and measurement was not doubled, because one spiked sample served for both EC and SID. All samples were digested with acid and heat, selenate was reduced to selenite, and selenite was measured by HG-ICP-MS. The Se determined by SID corresponded to that determined by EC with a concentration ratio of 1.02 ± 0.08 (n = 207 alfalfa samples). The measured Se in 8 reference materials also agreed well with certified values. The study showed that the double calibration approach was a direct way to evaluate data quality. This approach should be applicable to other multiisotope elements
Assay of Oxytetracycline in Animal Feeds by Liquid Chromatography with Fluorescence Detection
Authors: Houglum Joel E , Larson Richard D , Mutchler Darrel L , Wetzler Luann
Published: February 2020

A liquid chromatographic (LC) method is described to assay oxytetracycline (OTC) in feeds at gram-perton and gram-per-pound levels. Complete feeds and premixes are extracted with acid-methanol, according to AOAC Method 957.23B(i). Extracts are filtered and quantitated by LC using a C18 column and fluorescence detection with excitation at 390 nm and emission at 512 nm. The mobile phase (1.5 mL/min) uses a methanol gradient with an initial hold time of 1 min at 15% methanol followed by an increase to 35% methanol over 8 min. The aqueous component contains CaCI2, disodium ethylenediamine tetraacetate, and sodium acetate buffered to pH 6.5. Recovery of spiked samples averaged 101.6% (coefficients of variation, 0.1- 2.4%), and the limit of detection was 1 g/ton. Results correlated closely with those obtained by using AOAC microbiological Method 968.50 and with another LC method using ultraviolet detection. OTC and epi-OTC elute at approximately 7.4 and 4.8 min, respectively. No interference was observed from several drugs and other antibiotics often used in feeds in combination with OTC
High-Performance Liquid Chromatographic Method for the Determination of Moniliformin in Corn
Authors: Munimbazi Célestin , Bullerman Lloyd B
Published: February 2020

A high-performance liquid chromatographic method using UV absorption was developed for determining moniliformin in corn. The toxin was extracted with water containing 1 % tetrabutylammonium hydrogen sulfate (w/v). Paired moniliformin was partitioned into dichloromethane, which was evaporated to dryness at 50 C. The residue was dissolved in water and applied to a disposable stronganion exchange solid-phase extraction tube. Adsorbed moniliformin was eluted from the tube with 0.05M sodium dihydrogen phosphate monohydrate (pH 5). It was determined by ion-pair reversed-phase chromatography and UV measurement at 229 nm. The minimum detectable amount of pure moniliformin was 0.25 ng/injection (signal-to-noise ratio = 3:1). The detector response was linear from 0.25 to at least 20 ng. The limit of determination was 0.025 μg/g corn. Recoveries of moniliformin from corn spiked at 0.025,0.05,0.25, and 1.0 μg/g averaged 96.5,96.2, 97.2, and 97.8% respectively
Performance Tested Method Certification of BAX™ for Screening/Salmonella: A Case Study
Authors: Mrozinski Peter M , Betts Roy p , Coates Scott
Published: February 2020

This report details the independent laboratory study of the BAX™® for Screening/Salmonella assay to complete AOAC Performance Tested Method certification. The performance of the BAX system was compared with those of BAM culture methods on food samples inoculated with Salmonella. This study validated product claims. Performance Tested Method status was granted for the screening assay.
Liquid Chromatographic Determination of Sugar Alcohols in Beverages and Foods after Nitrobenzoylation
Authors: Nojiri Shuko , Saito Kazuo , Taguchi Nobuo , Oishi Mitsuo , Maki Toshio
Published: February 2020

Use of p-nitrobenzoyl chloride (PNBC) to form an ultraviolet-absorbing derivative was attempted to determine the sugar alcohols meso-erythritol, xyli-tol, D-sorbitol,and D-mannitol by liquid chromatography (LC). LC determination of derivatives was performed on an ODS column with acetonitrile–water (65 + 35) as mobile phase. Calibration curves were linear in the concentration range 0.01–100 μg/mL. Method sensitivity is 10 to 1000 times higher than that of LC with refractive index detection and gas chromatography with flame ionization detection. Recoveries of sugars added to various foods at 0.1 and 1% ranged from 91 to 102% for meso-erythritol, 75 to 115% for xylitol, 81 to 105% for D-sorbitol, and 81 to 108% for D-mannitol.
Determination of Submicrogram-per-Liter Concentrations of Caffeine in Surface Water and Groundwater Samples by Solid-Phase Extraction and Liquid Chromatography
Authors: Burkhardt Mark R , Soliven Paul P , Werner Stephen L , Vaught Deborah G
Published: February 2020

A method for determining submicrogram-per-liter concentrations of caffeine in surface water and groundwater samples has been developed. Caffeine is extracted from a 1 L water sample with a 0.5 g graphitized carbon-based solid-phase cartridge, eluted with methylene chloride-methanol (80 + 20, v/v), and analyzed by liquid chromatography with photodiode-array detection. The single-operator method detection limit for organic-free water samples was 0.02 μg/L. Mean recoveries and relative standard deviations were 93 ± 13% for organic- free water samples fortified at 0.04 μg/L and 84 ± 4% for laboratory reagent spikes fortified at 0.5 μg/L. Environmental concentrations of caffeine ranged from 0.003 to 1.44 μg/L in surface water samples and from 0.01 to 0.08 μg/L in groundwater samples.
Analysis of a Mixture of Polychlorinated Biphenyls and Chlorinated Pesticides in Human Serum by Column Fractionation and Dual-Column Capillary Gas Chromatography with Electron Capture Detection
Authors: Najam Allah R , Korver Margaret P , Williams Cynthia C , Burse Virlyn W , Needham Larry L
Published: February 2020

An analytical method is presented for precise identification and quantitation of 29 specific polychlorinated biphenyl (PCB) congeners and 15 chlorinated pesticides in human serum. Analyte surrogates PCB 30, PCB 204, 2,2′,4,4′,5,5′-hexa-bromo-biphenyl, perthane, α-hexachiorocyclohexane, and dichlorobenzophenone were added to each sample. The serum was extracted with an organic solvent and separated by adsorption chromatography into 3 elution fractions for high-resolution gas chromatographic analysis. Each fraction was analyzed by dual-column capillary chromatography followed by electron capture detection. Two capillary columns, DB-5 and DB-1701, with different polarities were used to increase selectivity for each analyte. Quantitation was performed by selecting 2 sets of calibration standard mixtures and 1,2-di-chloronaphthalene as an internal standard. Mean recoveries ranged from 39 to 126% for selected analytes and from 31 to 88% for surrogates. Detection limits for specific congeners and pesticides are reported. Typical chromatographic profiles of calibration standard mixtures, as well as a human sample, are illustrated. Verification of each analyte is assessed, and results of analyses of selected human samples and quality control criteria used to ensure data validity also are presented.
Recent Advances in Thin-Layer Chromatography of Pesticides
Authors: Sherma Joseph
Published: February 2020

Advances in the use of thin-layer chromatography (TLC) and high-performance TLC (HPTLC) for separation, detection, and qualitative and quantitative determination of pesticides, other agrochemicals, and related compounds are reviewed for the period 1996–1998. Analyses are covered for avariety of food, biological, and environmental samples and for residues of various pesticides, including insecticides, herbicides, and fungicides, belonging to different chemical classes. References on formulation analysis, hydrophobicity studies, and use of TLC and thin-layer radiochromatography for studies of pesticide metabolism, degradation, uptake, and related studies also are included.
Determination of Oxytetracycline, Tetracycline, and Chlortetracycline in Milk by Liquid Chromatography with Postcolumn Derivatization and Fluorescence Detection
Authors: Pena Angelina L S , Lino Celeste M , Silveira Irene N
Published: February 2020

A multiresidue method for isolation and liquid chromatographic determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in milk is presented. The sensitivity of the method is adequate to meet the needs of regulatory agencies. The European Community established 100 μg/kg as the maximum residue limit (MRL) in milk for TC, CTC, and OTC. Recoveries exceeded 80% for all tetracyclines at all levels, with good precision. Correlation coefficients of standards curves for individual tetracyclines isolated from fortified samples ranged from 0.991 for CTC to 0.998 for OTC. Other antibiotics that might interfere with analysis did notinterfere with elution times of OTC, TC, andCTC. The procedure is rapid, precise, and quantitative and requires minimal preparation andminimal use of organic solvents. It can beapplied to routine surveillance programs. We canprepare 10 samples for analysis in about 1.45 h.
Determination and Survey of Ochratoxin A in Wheat, Barley, and Coffee—1997
Authors: Trucksess Mary W , Giler John , Young Kathryn , White Kevin D , Page Samuel W
Published: February 2020

Ochratoxin A (OA) is a nephrotoxic and nephrocarcinogenic mycotoxin produced by Aspergillus and Penicillium species. It has been found mainly in cereal grains and coffee beans. The purpose of this study was to investigate the occurrence of OA in cereal grains and in coffee imported to the United States. A modified liquid chromatographic (LC) method for determining OA in green coffee was applied to wheat, barley, green coffee, and roasted coffee. The test sample was extracted with methanol–1% NaHCO3 (7 + 3), and the extract was filtered. The filtrate was diluted with phosphate-buffered saline (PBS), filtered, and passed through an immunoaffinity column. After the column was washed with PBS and then with water, OA was eluted with methanol. The eluate was evaporated to dryness, and the residue was dissolved in acetonitrile–water (1 +1). OA was separated on a reversed-phase C18 LC column with acetonitrile-water-acetic acid (55 + 45 + 1) as eluant and quantitated with a fluorescence detector. Recoveries of OA from the 4 commodities spiked over the range 1–4 ng/g were 71–96%. The limit of detection was about 0.03 ng/g. OA contamination at >0.03 ng/g was found in 56 of 383 wheat samples, 11 of 103 barley samples, 9 of 19 green coffee samples, and 9 of 13 roasted coffee samples. None of the coffee samples contained OA at >5 ng/g; only 4 samples of wheat and 1 sample of barley were contaminated above this level.
Inulin and Oligofructose Are Part of the Dietary Fiber Complex
Authors: Prosky Leon
Published: February 2020

Dietary fiber has been defined as the remnants of plant cells resistant to hydrolysis by human alimentary enzymes. Its main chemical constituents are hemicelluloses, celluloses, lignin, pectins, gums, and waxes. The U.S. Food and Drug Administration and the U.S. Department of Agriculture determine compliance with nutritional labeling regulations for dietary fiber by use of the existing AOAC INTERNATIONAL methods for total dietary fiber. The above compounds are readily detected by these methods. However, some oligo and polysaccharides are resistant to human alimentary enzymes and do not precipitate in 78% ethanol, the usual reagent for precipitating dietary fiber in analytical procedures. Some of these saccharides, termed fructans, are inulin and oligofructose. They possess many physiological attributes normally associated with dietary fiber. Inulin is a mixture of oligo and polysaccharides composed of fructose moieties joined by β(2→1) linkages in linear chains. Almost each chain ends with a glucose moiety. Oligofructose is a synonym for fructooligosaccharides, with fructose moieties joined by β(2→1) linkages, as in inulin. Not all molecules have a glucose unit, and the chain length is less than 10 units. A method for inulin and oligofructose was developed andapproved official first action by AOAC INTERNATIONAL in early 1997. It involves extraction of sample and treatment of the extract with amyloglucosidase followed by fructozyme (Fructozyme™ Enzyme Process Division, Novo Nordisk, Novo Industry, Copenhagen, Denmark). The sugars released in each of the 3 steps are measured by anion-exchange chromatography. The concentration of fructans is calculated as the difference of sugars, glucose and fructose, after the enzymatic treatments and the initial sample. The repeatability standard deviations for inulin and oligofructose ranged from 2.9 to 5.8% and the reproducibility standard deviations ranged
Separation of C60 and C70 Fullerenes by Thin-Layer Chromatography on Silica Gel Impregnated with Polymers
Authors: Litvinova Larissa S , Zgonnik Vladimir N
Published: February 2020

Separation of C60 and C7 fullerenes was studied on silica gel layers impregnated with polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly(ethyl- ene oxide) (PEO) solutions at 0.5-2.5%. To evaluate the effect of polymer nature on the retention of fullerenes, ΔhRf’ values were determined: ΔhRf’ =hRf(impregnated siO2)-hRf(siO2). For all polymers, the ΔhRf’ values of fullerenes increased with increasing concentration (C) of the impregnating solution. At C = 2.5%, ΔhRf’ increased with polymer nature in the following order: PVA < PEO < PVP. The separation selectivity of fullerenes also improved. Increasing the concentration of acetate groups in PVA increased ΔhRf’. The nature of interaction between fullerene and polymers is discussed.