bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of AmpiciUin and Amoxicillin in Milk with an Automated Liquid Chromatographic Cleanup
Authors: Moats William A
Published: February 2020

A method is described for determination of am-piciitin and amoxicillin in milk by using an automated liquid chromatographic (LC) cleanup. Milk was deproteinated by adding tetraethylammonium chloride solution and acetonitrile. The filtrate was concentrated by evaporation, filtered, and loaded into a 4 mL autosampler vial. For LC cleanup, a Waters W1SP 712 autosampler, a Varian 9010 pump, a Supelcosil LC-18 column, and an ISCO FOXY fraction collector were used. The cleanup program, where A is 0.01 M KH2PO4 and B is acetonitrile, was 100A + OB for 0-3 min and then 70A + 30B for 24 min. Sample concentrate (2 mL) was loaded onto the column for cleanup. Fractions containing amoxicillin and ampicillin were collected, partially acidified, and concentrated to 1 mL. Analysis was done on the LC-18 column, with a mobile phase of 0.015M H3PO4–{0.0075M sodium dodecyl sulfate-acetonitrile (70 + 30)] for amoxicillin and 0.0067M H3PO4–0.0033M KH2PO4–[0.005M sodium dodecyl sulfate–acetonitrile (67 + 33)] for ampicillin. Recoveries were generally 80–90% at a concentration range of 1–0.01 ppm, with a detection limit of 2–5 ppb. By collecting appropriate fractions, the method can be applied to the determination of any amphoteric β-lactam.
Determination of Captan in Water, Peaches, and Apple Juice by a Magnetic Particle-Based Immunoassay
Authors: Itak Jeanne A , Selisker Michele Y , Herzog David P , Fleeker James R , Bogus Edward R , Mumma Ralph O
Published: February 2020

A magnetic particle-based enzyme-linked immunosorbent assay (EUSA) was used to determine captan residues in water, peaches, and apple juice. Precision studies of captan-spiked water samples showed coefficients of variation (CVs) of 24% at 0.1 ppm and 15% at 2.0 ppm. Average recoveries from water were 110–118%, with an estimated sensitivity of 0.01 ppm for captan. Low cross-reactivity was seen with the related phthalimide fungicides capta-fol and folpet. A least-detectable dose (LDD) of 1 ppm was estimated for captafol in the immunoassay; an LDD of 8.6 ppm was estimated for folpet. Apple juice samples were analyzed by a 3-step procedure: the sample was concentrated on a Cis bonded silica solid-phase column, the eluate was diluted in buffer, and the sample was assayed by ELISA. The detection limit in apple juice was estimated to be 0.1 ppm on the basis of the detection limit observed in water and the required calculation factors; the average recovery was 115%. Acetone extraction, Cis bonded silica solid-phase extraction column, and the immunoassay were used consecutively to analyze peach samples. The detection limit in peaches was estimated to be 0.15 ppm on the basis of the detection limit observed in water and the required calculation factors. Captan residues were found in all but one of the peach samples and ranged from 0.15 to 1.12 ppm (|ig/g). Recovery of added captan from peaches averaged 98% for both spike levels tested. Results of analysis of captan in peaches by immunoassay and gas chromatography with electron capture detection (GC/ECD) were compared. GC/ECD gave an average recovery of 75%; immunoassay gave an average recovery of 112%.
Elevated-Temperature, Colorimetric, Monoclonal, Enzyme-Linked Immunosorbent Assay for Rapid Screening of Salmonella in Foods: Collaborative Study
Authors: Eckner Karl F , Dustman Wendy A , Curiale Michael S , Flowers Russell S , Robison Barbara J
Published: February 2020

A collaborative study was performed by 30 laboratories in 3 sets of trials to validate a modified colorimetric monoclonal enzyme-linked immunosorbent assay (ELISA) method for Salmonella detection. The modifications to the current methodology included incubation of enrichments and postenrichments at an elevated temperature, addition of novobiocin to the M-broth post-enrichment, and elimination of the centrifugation and agitation steps. Five artificially contaminated foods (nonfat dry milk, milk chocolate, dried egg, ground black pepper, and soy flour) and 1 naturally contaminated food (raw ground turkey) were analyzed. The artificially contaminated foods were inoculated with individual Salmonella serotypes at a high (10–50 cells/25 g) and low (1–5 cells/25 g) contamination level. Results from the modified ELISA method were compared to the Bacteriological Analytical Manual (BAM)/AOAC culture method. In 2 of the food products, milk chocolate and pepper, a number of laboratories isolated Salmonella from uninoculated control samples, thus invalidating their data. As a result, there were too few laboratories remaining with valid data, and these foods were repeated. In the completed study, there were 11 false negative results obtained by the modified ELISA method, while there were 28 false negatives produced by the BAM/AOAC procedure. There were 11 ELISA positive assays which could not be confirmed by culture methods. Statistically, there were no differences between the modified, colorimetric, monoclonal ELISA and the reference culture method in all foods except raw turkey, where the ELISA method was more productive. The colorimetric monoclonal enzyme immunoassay (Salmonella-Tek) method for detecting Salmonella in all foods has been adopted first action by AOAC INTERNATIONAL.
Spectrophotometric Determination of Nitrate in Baby Foods: Collaborative Study
Authors: Sjöberg Anna-Maua K , Alanko Timo A
Published: February 2020

A collaborative study was conducted of a spectro-photometric method for determination of nitrate after cadmium reduction to nitrite in baby foods containing meat. Thirty-one municipal and 2 industrial food laboratories participated in the study. The study design involved 2 baby food matrices. Samples of both matrices were prepared at 3 concentration levels between 52 and 309 mg NaNO3/kg as blind duplicates. A blank without added nitrate was also included. The outlier percentage of the results was very low (4.3%). It was typical for the method that recoveries were slightly >100%. Recoveries for baby foods varied between 113.3 and 116.9%, and were acceptable for control purposes. The relative standard deviations for repeatability were 5.0–18.1%. The relative standard deviations for reproducibility were 8.3–21.6%. Three collaborators also evaluated liquid chromatographic technique for nitrate determinations. These preliminary results are presented but are not analyzed statistically. The spectrophotometric method was adopted first action by AOAC INTERNATIONAL.
Comparison of Methods for Sampling Vadose Zone Soils for Determination of Trichloroethylene
Authors: Hewitt Alan D
Published: February 2020

This study compares 2 sampling and handling methods for the collection of soils to be analyzed for volatile organic compounds (VOCs). The currently accepted practice uses a vessel for the sole purpose of transferring and storing suspect soils from hazardous waste sites. This practice requires that the soil that is analyzed be handled at least twice: once when the vessel is filled on site and again when a subsample is removed for laboratory analysis. The sampling and handling protocol with which the current practice was compared limits sample exposure and disruption during collection and provides for sample acquisition during the field sampling exercise. The results confirm that sampling methods that limit disruption and exposure of soil samples are needed to obtain more accurate measurements of VOC concentrations in vadose zone soils.
Liquid Chromatographic Method for Analysis of the Naphthalene Dicarboxaldehyde Derivative of Fumonisins
Authors: Bennett Glenn A , Richard John L
Published: February 2020

A liquid chromatographic (LC) method for determining fumonisins in corn, feed, and laboratory cultures was optimized. We investigated the efficiency of extraction solvents, the performance of cleanup columns, the stability of fluorescent derivatives, and the efficiency of LC columns to separate deri-vatized fumonisins from interferences so that we could develop a sensitive, reliable assay for fumonisins. Maximum extraction efficiency was accomplished by shaking contaminated samples in acetonitrile–water (50 + 50, v/v) for 1 h; methanol–water mixtures and other ratios of acetonitrile–water were less efficient. Solid-phase extraction cleanups on reversed-phase Cia and strong anion exchange (SAX) columns were compared. The SAX columns were very efficient in isolating fumonisins from crude extracts; however, only the C18 columns could be used to partially purify fumonisin hydrolysis products. A highly fluorescent and stable derivative, prepared from naphthalene-2,3-dicar-boxaldehyde, proved to be suitable for LC analysis. Both parent compounds and hydrolysis products were separated in a simple gradient systjem of acetonitrile-acetic acid and water-acetic acid in less than 30 min.
Production of Carbon 14-Labeled Fumonisin in Liquid Culture
Authors: Blackwell Barbara A , Miller J David , Savard Marc E
Published: February 2020

A method for the production and purification of radiolabeled fumonisin that involves the addition of 14C-acetate to liquid cultures of Fusarium moniliforme in shake flasks is reported. Stable isotope 13C labeling studies were carried out using specifically enriched acetate and several amino acids to determine the location of labeled carbon atoms in the radiolabeled fumonisin that was also produced (650 μCi/mmol). These experiments determined that the 14C was distributed throughout the molecule making it useful for studies of fumonisin residues in animal products. Additionally, the 13C studies indicated that the biosynthesis of fumonisin involves the addition of methionine, glutarate, and serine or alanine to the hydrocarbon backbone. These data best fit the hypothesis that this backbone is polyketide in origin as opposed to being a modified lipid.
Liquid Chromatographic Determination of Sphmgamne and Sphingosine: Use of the Free Sphinganine-to-Sphingosine Ratio as a Biomarker for Consumption of Fumonisins
Authors: Riley Ronald T , Wang Elaine , Merrill Alfred H
Published: February 2020

Because the chemical structure of fumonisin B1 (FB1) has several structural features in common with the sphingoid bases, sphingosine and dihydro-sphingosine (sphinganine), we tested the hypothesis that the fumonisins might alter the normal cellular activity or the metabolism of endogenous free sphingoid bases. FB1 was found to be a potent inhibitor of de novo sphingolipid biosynthesis in vitro, its primary target being sphinganine N-acyl-transferase. This inhibition resulted in a decrease in the biosynthesis of sphingosine and an accumulation of free sphinganine, an intermediate in the de novo biosynthetic pathway for complex sphin-golipids. These findings led to the hypothesis that consumption of feed containing fumo|nisins should cause an increase in the ratio of free sphinganine to free sphingosine in tissues and serum. Data consistent with this hypothesis have been obtained from horses and pigs that consumed feed containing fumonisin-contaminated corn screenings and from rats fed feed supplemented with fumonisin-containing fungal culture materials or pure FBi. Thus, the ratio of free sphinganine to free sphingosine shows promise as a tissue, urine, or serum marker for animals consuming feed containing fumonisins. The present paper provides a detailed description of the extraction of free sphingoid bases and the liquid chromatographic method we used for determining the relative amounts of free sphingosine and free sphinganine in serum, urine, and various tissues of animals. Study results are summarized, and the ratio of free sphinganine to free sphingosine is discussed as a presumptive test for identifying animals consuming fumonisin-contami-nated feed.
Determination of Nitrofuran Residues in Poultry Muscle Tissues and Eggs by Liquid Chromatography
Authors: Kumar Luxmy , Toothell John R , Ho Koon-Bay
Published: February 2020

A liquid chromatographic (LC) method was developed and statistically validated for the determination of nitrofurazone, furazolidone, and furaltadone residues in poultry and porcine muscle tissues. The antimicrobial residues were extracted with a mixture of dichloromethane and ethyl acetate by using ultrasonication followed by solid-phase extraction cleanup and LC analysis with UV detection. A modification of the method incorporating acetonitrile extraction and solvent partition cleanup was developed for analysis of poultry eggs. The limits of detection were 1 μg/kg for nitrofurazone and furazolidone and 2 μg/kg for fural-tadone in both muscle tissues and eggs. Average recoveries for spike levels of 1,2, and 5 μg/kg ranged from 84 to 128%, and coefficients of variation were between 1.1 and 12.1%. Afield trial with these methods was conducted in conjunction with the Western Australian Department of Agriculture to determine the stability of furaltadone in both poultry tissue and eggs. Results of this study show that the concentration of furaltadone in muscle tissue diminished rapidly even when stored at −18°C. Furaltadone was considerably more stable in eggs.
Deoxyribonucleic Acid Hybridization Method for the Detection of Listeria in Dairy Products, Seafoods, and Meats: Collaborative Study
Authors: Curiale Michael S , Sons Terri , Fanning Luanne , Lepper Wendy , Mclver Dawn , Garramone Susan , Mozola Mark
Published: February 2020

The method is based on the hybridization of synthetic deoxyribonucleic acid probes to ribosomal ribonucleic acid sequences unique to Listeria. This method was compared to 2 culture methods: the U.S. Food and Drug Administration method for the detection of Listeria in dairy products and sea-foods and the U.S. Department of Agriculture, Food Safety and Inspection Service method for Listeria in meats. Six food types with replicate samples containing various concentrations of Listeria were analyzed by the collaborating laboratories. Listeria was detected in 774 samples using the DNAH method and in 772 samples using a culture method. The DNAH and culture methods were in agreement for 668 samples containing Listeria and 306 samples without Listeria. The overall rate of agreement between methods was 82.3%. The method has been adopted first action by AOAC INTERNATIONAL.
Gas Chromatographic Determination of Mono- and Diglycerides in Fats and Oils: Summary of Collaborative Study
Authors: Firestone David
Published: February 2020

A collaborative study was conducted on a capillary gas chromatographic method for the determination of mono- and diglycerides in fats and oils. Other components of fats and oils such as glycerol, fatty acids, and sterols may be analyzed by this method. Six materials used in the study consisted of 2 commercial mono- and diglyceride emulsifiers, 2 synthetic compositions with known amounts of monoand diglycerides in the presence of an excess of triglycerides, and 2 refined sunflower oils spiked with mono- and diglycerides. Eight laboratories participated in the study. On the basis of the collaborative study results, the method has been adopted first action by AOAC INTERNATIONAL as an IUPAC/AOCS/AOAC method.
Liquid Chromatographic Fluorescence Method for the Determination of Thiabendazole Residues in Green Bananas and Banana Pulp
Authors: Arenas Rene V , Johnson Nelson A
Published: February 2020

A novel liquid chromatographic method was developed for the determination of thiabendazole (TBZ) residues in whole green bananas and ripe banana pulp. TBZ is extracted from the banana matrix with ethyl acetate, followed by cleanup of extract on a cation-exchange, solid-phase extraction column. The extract is analyzed for TBZ residues by column liquid chromatography using a cation-exchange column with fluorescence detection. Recoveries of TBZ from whole green bananas fortified with TBZ at 0.05-10 ppm and from ripe banana pulp fortified with TBZ at 0.01-2 ppm averaged 93 and 95%, respectively. The following method for monitoring TBZ residues in whole green bananas and ripe banana pulp is simple, rapid, and sensitive.
Analysis of Flusilazole and Its Major Phenyl Metabolite (IN-F7321) by Approaches Based on Gas Chromatography
Authors: Guinivan Richard A , Gagnon Michael R
Published: February 2020

Two basic, previously unpublished procedures were developed to obtain flusilazole data for regula- tory purposes. One method involves extraction into ethyl acetate, cleanup on silica or Florisil, and analysis of flusilazole only by packed-column gas chromatography (GC) with nitrogen-phosphorus detection. The second method involves extraction into ethyl acetate, followed by gel permeation chro- matography and analysis by capillary GC with mass-selective detection for both IN-F7321 (major metabolite) and flusilazole. Several adaptations of the second procedure increase the analytical op- tions for flusilazole. The parent-only method was applied to analysis of more than 18 matrixes. The parent-plus-metabolite method and its adaptations were applied to the analysis of more than 33 ma- trixes. Cereals, fruits, animal matrixes and related processed fractions were analyzed. Average recov- eries for the parent-only method were generally above 90% (always above 80%) with standard devia- tions of 12% or less for fortifications ranging from 0.010 to 1.0 ppm. Average recoveries ranged from 84 to 108% for flusilazole and 82 to 111% for IN- F7321 fortifications from 0.010 to 2.0 ppm for the parent-plus-metabolite method. Standard devia- tions ranged from 3.6 to 20%.
Colorimetric Determination of Trace Iron in Water Samples by Using a Poly(Vinyl Chloride) Membrane Containing Bathophenanthroline as a Solid-Phase Extraction Medium
Authors: Saito Takashi
Published: February 2020

Trace iron was determined by solid-phase extraction using a polymer membrane as an extracting medium. The polymer membrane consisted of 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) as a chelating agent, o-nitrophenyl octyl ether (o-NPOE) as the extracting solvent, and polyvinyl chloride) (PVC). When the PVC membrane came into contact with iron in the samples, the membrane changed from colorless to red, and the color intensity was proportional to the iron concentration. The iron concentration was calculated from a calibration graph, after the absorbance of the colored membrane was measured spectrophotometrically. With this method, iron concentrations ranging from 2.76 × 10−7 to 4.29 × 10−5M were determined quickly and easily.
Reversed-Phase Liquid Chromatographic Determination of Vitamin D in Milk
Authors: Hagar Arthur F , Madsen Lee , Wales Louis , Bradford Henry B
Published: February 2020

Vitamin D in milk is determined by a slight modification of the method of Sliva et al. [J. AOAC Int. (1992) 75,566–571] for infant formula and enteral nutritional products. The sample is saponified for 30 min at 60°C and extracted overnight into 60 mL of hexane. The hexane layer is washed, neutralized, and taken to dryness with a rotary evaporator. The sample is reconstituted in hexane and applied to 500 mg of Florisil in a solid-phase extraction column. Vitamin D is eluted with isopropyl alcohol. The eluate is evaporated to dryness under N2, and the sample is reconstituted in 1.0 mL of acetonitrile. The extract is analyzed on a C18 liquid chromatographic column (250 × 4.6 mm, 5 μm particle size) with UV detection at 265 nm. Milk samples of various fat content (i.e., skim, low fat, and whole milk) were analyzed. Spiked recoveries gave means of 81–96%; recoveries were inversely related to fat content. Assay precision ranged from 3.2 to 8.6%. The method can measure vitamins D2 and D3 individually, and no difference in the recoveries of the 2 vitamins was observed. Thus, vitamin D2 can be used as an internal standard for quantitating vitamin D3, and vice versa. The method is satisfactory for use in screening of milk for vitamin D content.
Determination of Narasin in Raw Material, Premix, and Animal Feeds by Liquid Chromatography and Correlation to Microbiological Assay
Authors: Rodewald John M , Moran John W , Donoho Alwin L , Coleman Mark R
Published: February 2020

A method is described for the detection and quantitation of narasin in raw material, premix, and feeds by liquid chromatography (LC) and postcolumn derivatization (PCD) with vanillin. Narasin was mixed with vanillin under acidic conditions and heated, and the resulting products were measured by a variable-wavelength detector operating at 520 nm. The LC responses of narasin and narasinlike factors were determined and correlated to the microbiological response of each factor as determined with Streptococcus faecium. Narasin reference standard was characterized in the same manner as the individual factors. The chemical composition of the reference standard (i.e., the amounts of narasin factors expressed in percent) combined with the relative microbiological potency value was used to calculate the biopotency contribution of each narasin factor. A formula was used to transform chemical composition values (amounts of narasin factors expressed in percent) of the reference standard to total microbiological activity as directly obtained from the microbiological assay. The LC method was validated by analyses of raw material, premix, and cattle and poultry rations.
Capillary Zone Electrophoretic Determination of Histamine in Fish
Authors: Mopper Barry , Sciacchttano Carl J
Published: February 2020

Histamine, the principal causative agent in scombroid food poisoning, was analyzed in seafood by a new, rapid, and sensitive method using capillary zone electrophoresis (CZE) with UV detection at 210 nm. Incurred histamine in methanolic fish extracts migrated within 4 min in a fused silica capillary filled with 0.02 M citrate buffer, pH 2.5, under an applied potential of 375 V/cm. The analytical response was linear from 0.5 to 100 ppm histamine (correlation coefficient, r = 0.999). The coefficients of variation for migration time and peak area response were <1 and <3%, respectively. Recovery of histamine in fortified fish composites was satisfactory. CZE was considered for alternative application in seafood speciation.
Determination of Monensin in Chicken Tissues by Liquid Chromatography with Postcolumn Derivatization
Authors: Moran John W , Matthew Rodewald J , Donoho Alvin L , Coleman Mark R
Published: February 2020

A method is described for the detection and quantitation of monensin in chicken tissues by liquid chromatography with postcolumn derivatization with vanillin. Monensin is extracted from the tissues by homogenization with methanol–water and is isolated and concentrated by liquid–liquid partition and sorbent extraction with silica gel. Monensin is mixed postcolumn with vanillin under acidic conditions and heated, and the resulting products are measured by a variable-wavelength detector operating at 520 nm. The method has a limit of quantitation of 0.025 μg/g and is validated for use in the analyses of chicken muscle, liver, and skin (with adhering fat tissues) for monensin. Standard recoveries from the 3 tissue types tested at 3 levels ranged from 82 to 96%. The method represents an improvement in specificity, accuracy, and analysis time over existing methods, which use microbiological techniques.
Direct Graphite Furnace–Atomic Absorption Method for Determination of Lead in Edible Oils and Fats: Summary of Collaborative Study
Authors: Firestone David
Published: February 2020

The IUPAC Commission on Oils, Fats, and Derivatives undertook development of a method and collaborative study for the determination of lead in oils and fats by direct graphite furnace–atomic absorption spectrophotometric method. Various types of graphite furnaces were used with or without platform. Twenty-three collaborators from 12 countries participated in the study. The materials tested were edible oils (soybean oil) and fats (cocoa butter) containing lead at 3 concentration levels (low, medium, and high). Each level was represented by 2 batches provided in duplicate (blind coded), so that each collaborator received a total of 24 test samples. Collaborators were instructed to analyze each in duplicate and report both results. Twenty collaborators returned the results of the study. After data from laboratories that did not follow the instructions were excluded, only 16 sets of data were evaluated statistically. The method for determination of lead in oils and fats by direct graphite furnace–atomic absorption spectrophotometry has been adopted first action by AOAC INTERNATIONAL as an IUPAC–AOCS–AOAC method.
Particle Concentration Fluorescence Immunoassay for Determination of Tylosin in Premix, Feeds, and Liquid Feed Supplement: Comparison with Tiirbidimetric Assay
Authors: Wicker Alan L , Mowrey Daniel H , Sweeney Daniel J , Coleman Mark R , Morris Deborah K , Brockus Catherine L
Published: February 2020

A rapid, competitive particle concentration fluorescence immunoassay (PCFIA) for the determination of tylosin (Tylan) concentrations in extracts of pre-mix, feeds (cattle, chicken, and swine), and liquid feed supplement is described. Tylosin-β-phyco-erythrin conjugate, tylosin standard or diluted sample extracts, and rabbit anti-tylosin antibody are incubated for 15 min in PCFIA plates. Rabbit anti-tylosin antibody is then captured, during a 15 min incubation, with goat anti-rabbit antibody that is attached to latex beads. Assay plates are washed to remove unbound tylosin-(β-phyco-erythrin and unbound, free tylosin. Fluorescence is measured with a fluorimeter. Tylosin concentration is inversely proportional to the β-phycoerythrin fluorescence signal. The method, evaluated and validated with an IDEXX Screen Machine, shows high specificity with regard to compounds expected to be found in the presence of tylosin, and results correlate well with traditional turbidimetric assay results. Hydrolysis of TUA (tylosin-urea ad-duct), necessary with microbiological methods, and cleanup of extracts beyond filtration are unnecessary with the PCFIA for tylosin.
Alternative Sieving Method for Extraction of Light Filth from Cheeses: Collaborative Study
Authors: Nakashima Marvin J
Published: February 2020

A collaborative study was conducted on an alternative sieving method for the extraction of light filth from cheeses. The alternative method was developed that is applicable to broad variety of cheeses. A 225 g test portion is dispersed in a solution of 5.7% HCI, Igepal CO-730, and Igepal DM-710. Digested cheese is wet-sieved on a No. 230 sieve. The residue is treated with Tergitol Anionic 4, transferred to 1% sodium lauryl sulfate solution, heated, and maintained at 65°-75°C for 10 min. The residue is washed with these 2 surfactants a maximum of 4 times until it is reduced to an amount that is filterable. The residue is filtered and the filter papers are examined microscopically at a magnification of ca 30×. Average recoveries by 9 collaborators for 3 spike levels of rat hairs (5,10, and 15) were 80, 68, and 81%, respectively; for insect fragments (5,15, and 30) recoveries were 97, 90, and 92%, respectively. The alternative sieving method for extraction of light filth from cheeses has been adopted first action by AOAC INTERNATIONAL.
Effect of Infrared Analyzer Homogenization Efficiency on Repeatability of Uncorrected Fat A and Fat B Signals
Authors: Smith Erika B , Barbano David M , Lynch Joanna M , Fleming J Richard
Published: February 2020

Poor repeatability by infrared milk analyzers may be caused by inefficient homogenization as a result of light scattering and the Christiansen effect. The objectives of this study were to identify instruments with good and poor homogenization efficiency and to determine if a difference exists in repeatability performance between instruments with good vs poor homogenization efficiency. Unhomo-genized and homogenized portions of the same milk were tested 20 times consecutively on 22 instruments. An instrument was considered to have poor homogenization efficiency if the mean difference in the uncorrected signal between unhomo-genized and homogenized portions of the same milk was ≥1.43% of the fat test (i.e., ≥0.05% at 3.5% fat). Instruments were evaluated for repeatability by calculating the sample standard deviation and the range of the latter 19 uncorrected readings for un-homogenized and homogenized milks. When repeatability was evaluated as a function of homogenization efficiency, there was a significant (p = 0.001) correlation between poor homogenization efficiency and poor repeatability when testing unho-mogenized milk but not when testing homogenized milk. Improved homogenizer performance within infrared milk analyzers is needed to improve the repeatability of raw milk testing.
Determination of Phthalates in Water and Soil by Tandem Mass Spectrometry Under Chemical Ionization Conditions with Isobutane as Reagent Gas
Authors: Brumley William C , Shafter Elizabeth M , Tillander Paul E
Published: February 2020

Eleven phthalate esters spiked in water and soil were determined by tandem mass spectrometry (MS) under positive chemical ionization mass spectrometry (CIMS) conditions with isobutane as reagent gas. Emphasis was placed on the determination step because tandem MS and CIMS are not widely adopted in current methods of the U.S. Environmental Protection Agency. Extraction by sonica-tion and cleanup by use of a solid-phase extraction cartridge were adopted. The relative response factors gave relative standard deviations (RSDs) of 12-30% when 2 unlabeled internal standards were used. The relative abundances of monitored ions gave relative abundance deviations of less than ± 8%. The method confirms identity, including molecular weight, and quantitates with high specificity. Results obtained with 2 unlabeled internal standards were compared with results obtained with a stable-isotope-labeled internal standard for dioctyl phthalate.
A Rapid Multiresidue Screen for Organophosphorus, Organochlorine, and N-Methyl Carbamate Insecticides in Plant and Animal Tissues
Authors: Holstege Dirk M , Scharberg David L , Tor Elizabeth R , Hart Laura C , Galey Francis D
Published: February 2020

A multiresidue screen for the quantitative determination of 43 organ op hosphorus, 17 orga no-chlorine, and 11 N-methyl carbamate insecticides in 10 g of plant or animal tissues is described. The insecticides are extracted with 5% ethanol in ethyl acetate (v/v). Samples with high lipid content are cleaned up by automated gel permeation chromatography with a 30% ethyl acetate in hexane (v/v) eluant and in-line silica gel minicolumns. Highly pigmented samples are cleaned up with class-specific solid-phase extraction columns. The concentrated extracts are analyzed by selective detection with gas chromatography or liquid chromatography. Recovery of 71 insecticides ranged from 77 to 113%. Analysis of fortified bovine liver (n = 5) resulted in an average recovery of 96 ± 4% at the 0.5 to 0.05 μg/g level. Analysis of fortified alfalfa hay (n = 5) resulted in a mean recovery of 94 ± 4% at the 0.06 to 0.5 μg/g level, and analysis of fortified fresh tomatoes (n = 5) resulted in an average recovery of 97 ± 3% at the 0.06 to 0.5 μg/g level. Method detection limits ranged from 0.02 to 0.5 μg/g for the compounds studied with a nominal 10 g sample.
Determination of Ethyl Carbamate in Alcoholic Beverages and Soy Sauce by Gas Chromatography with Mass Selective Detection: Collaborative Study
Authors: Canas Benjamin J , Joe Frank L , Diachenko Gregory W , Burns Gordon
Published: February 2020

A method using gas chromatography with mass selective detection for the determination of ethyl carbamate (EC; also known as urethane) in alcoholic beverages and soy sauce was collaboratively studied by 17 laboratories including authors’ laboratories. The method uses prepacked columns for extraction of liquids with methylene chloride, and n-propyl carbamate as the internal standard. A practice sample and 6 samples of distilled spirits, fortified wines, table wines, and soy sauces were analyzed by each collaborator. Each matrix included blind duplicates of incurred and fortified EC at 3 levels. Distilled spirits contained 50–330 ng EC/g (ppb), fortified wine 40–160 ppb, table wine 10–50 ppb, and soy sauce 15–70 ppb. The ranges of the repeatability relative standard deviations, excluding outliers, were 4.03–6.63% for distilled spirits, 4.01–5.05% for fortified wine, 3.94–6.73% for table wine, and 4.70–8.49% for soy sauce. The ranges of the reproducibility relative standard deviations, excluding outliers, were 8.53–9.49% for distilled spirits, 6.84–12.02% for fortified wine, 8.86–18.47% for table wine, and 13.87–27.37% for soy sauce. Recoveries of added EC ranged from 87 to 93%. Recoveries relative to reference values, labeled as the internal standard, obtained by using gas chromatography/ tandem mass spectrometry with a triple quadrupole mass spectrometer ranged from 89 to 100%.
Fractionation of Salad Dressings for Fatty Acid Profile and Soluble Sugar Determination Using the Ultracentrifuge
Authors: Patel Anasuya S
Published: February 2020

An analytical method was developed for fractionating small samples of salad dressing for fatty acid profiles and soluble sugar content by using an ultracentrifuge. The extracted oils were characterized and compared with those obtained by the official AOAC ether extraction procedure. Both methods gave similar results for fatty acid profiles and oil recoveries. The fatty acid profiles were determined by gas chromatography. In addition, the sugar content of the aqueous layer of the centrifuged samples could easily be obtained by refractometry. The proposed method is time and labor efficient and eliminates the use of hazardous and flammable ether.
Gas Chromatographic/Mass Spectrometric Confirmation of Ten N-Methylcarbamate Insecticides in Liver
Authors: Bakowski Ralph S , Ali M Sher , White Jerry D , Phillippo Evan T , Ellis Richard L
Published: February 2020

A gas chromatographic/mass spectrometric (GC/MS) confirmation procedure for 10 phenyl-N-methyl-carbamate insecticides in liver tissue was developed. The extract from liquid chromatography (LC) is purified with a C18 solid-phase extraction cartridge and then derivatized with heptafluorobutyric anhydride; the derivative is injected for analysis by GC/MS with electron ionization and multiple ion monitoring. The identity of the derivative is confirmed by comparison of its retention time and relative intensity data with those of a standard. Liver extracts from the LC procedure containing carbamates at 10 ppb levels were successfully confirmed by this procedure.
Evaluation of Two Field Screening Test Kits for the Detection of PCBs in Soil by Immunoassay
Authors: Waters Larry C , Smith Rob R , Stewart Joe H , Jenkins Roger A , Counts Richard W
Published: February 2020

Effective field screening methods could minimize the time and reduce the cost of characterizing and remediating hazardous waste sites. Rigorous evaluation of novel field screening methods is required before they can be considered as replacements for, or adjuncts to, currently used laboratory methods. Alternatives to standard laboratory analytical methods should be rapid, analyte-specific, cost-effective, accurate, and sensitive in the range at which the analyte is regulated. In this study, 2 immunoassay- based field test kits for polychlorinated biphenyls (PCBs) in soil were evaluated with reference to those criteria. PCBs were analyzed in both spiked and field soil samples. Based on laboratory performance, we estimate that 20 to 40 samples can be analyzed in the field per day. Sensitivity of the assay is in the 1 ppm range. Because the assay is based on the specificity of the antigen/antibody reaction, interferences are practically negligible. The method is accurate; the false-negative and false-positive results that were observed can be explained by differences in the immunoreactivities of the Aroclors present in the test samples and the Aroclors used as standards in the assay. The savings in time and expense to analyze PCBs in soil with the immunoassay-based test kits over conventional laboratory methods should be substantial.
Determination of Ardacin in Various Silage Feed Diets by a Rapid Liquid Chromatographic Assay
Authors: Fagan Sylvia V B , Gombatz Connie , Abdel-Kader Hafez , Menon Govind
Published: February 2020

A method is presented for the detection and quantitation of Ardacin in silage feed diets by liquid chromatography, using a cyano column and an acetonitrile–methanol water mobile phase modified with trifluoroacetic acid. This method includes comprehensive procedures for extracting Ardacin from various silage feed formulations, cleaning up the extracted sample by using solid-phase extractions, and analyzing the eluted solid-phase extract with a suitable liquid chromatographic system. Ardacin was extracted from the silage feed formulations with 50% acetonitrile and 50% 0.1 M KOH. The extract was cleaned up with a wide-pore butyl solidphase extraction cartridge. The sample extract was chromatographed and quantified at 220 nm, using an external method of calculation. Recoveries of the medicated silage feed formulation ranged from 72.1 ± 1.7% to 109.1 ± 2.4%, depending on the sites and types of formulation analyzed.
Rapid Supercritical Carbon Dioxide Extraction Method for Determination of Polychlorinated Biphenyls in Fish
Authors: Lee Hesg-Biu , Peart Thomas E , Niimi Arthur J , Knipe Charles R
Published: February 2020

An efficient and environmentally friendly supercritical fluid extraction (SFE) method for the determination of naturally contaminated polychlorinated biphenyls (PCBs) in fish tissues is described. The effect of various SFE conditions on lipid content and PCB recovery in fish extracts was studied. Optimal conditions for PCB extraction were nonmodified carbon dioxide at 100°C, pressure of 5000 psi, and flow rate of 2.5 mL/min. Recoveries of PCBs were ≥95% for both naturally contaminated and spiked fish, and this extraction procedure required less than 40 min per sample. By incorporating activated basic alumina with the sample in the extraction process, fish lipid was selectively retained by the adsorbent. The lipid content in the SFE extract varied from <0.1% to 2.2% for the fish samples tested, including those samples with over 30% lipid by weight. In most cases, the remaining lipid was conveniently removed from PCBs by a down-sized Florisil column cleanup. The commonly found chlorinated insecticides, hexachlorobenzene, p,p′-DDE, and mirex were also extracted and determined simultaneously with PCBs.
Evaluation of Prechromatographic Oxidation for Liquid Chromatographic Determination of Paralytic Shellfish Poisons in Shellfish
Authors: Lawrence James F , Ménard Cathie , Cleroux Chantal
Published: February 2020

A liquid chromatographic (LC) method employing prechromatographic oxidation for the determination of paralytic shellfish poison (PSP) toxins was evaluated. A number of changes to an earlier method resulted in improved separation and quantitation of most PSP analogues. Modification of the periodate oxidation reaction for the h-hydroxy-containing toxins led to improved sensitivity and stability of the products, enabling automated overnight analyses. These changes also enabled quantitation of gonyautoxins 1 and 4 (together) in the presence of gonyautoxins 2 and 3. Decarbamoylsaxitoxin can be identified and quantitated after peroxide oxidation. A cleanup step using a strong-anion-exchange column removed the C toxins and B-2 from the extracts and enabled a more accurate quantitation of gonyautoxins 1 and 4 and neosaxitoxin. Chiral chromatography, employing a reversed-phase column and chiral mobile-phase additives (copper-proline complex), was briefly evaluated for the separation of the oxidation products of the isomer pairs, gonyautoxins 1 and 4 and gonyautoxins 2 and 3. A comparison of the method with the mouse bioassay for the determination of PSP in lobster hepatopancreas (58 samples) showed a reasonable correlation (0.90) over a concentration range of 40–500 (μg/100 g (saxitoxin equivalents), although the LC results were consistently higher than the mouse bioassay values by about 40%.
Detection of Marine Toxins Using Reconstituted Sodium Channels
Authors: Trainer Vera L , Baden Daniel G , Catterall William A
Published: February 2020

Specific binding of the marine toxins saxitoxin, tetrodotoxin, and brevetoxin to the rat brain sodium channel is demonstrated using purified sodium channels reconstituted into phospholipid vesicles. Restoration of sodium channel function and binding activity by incorporation into phospholipid vesicles provides the only rigorous proof that the purified protein contains the neurotoxin receptor sites. In addition, reconstitution provides a valuable experimental preparation for biochemical analysis of neurotoxin binding sites and may facilitate the development of a specific toxin detection system.
Integration of Immunochemical Methods with Other Analytical Techniques for Pesticide Residue Determination
Authors: Lucas Anne D , Gee Shirley J , Hammock Bruce D , Seiber James N
Published: February 2020

The growing volume of literature concerning immunoassay analysis for trace levels of agrochemicals and other low molecular weight contaminants in various matrixes is indicative of the tremendous interest in and utility of this analytical technique. Most immunoassay methods described in the literature analyze compounds directly, for example, a herbicide in water, or involve solvent exchange of an organic sample extract or dilution of an aqueous-based sample to minimize the matrix effect. As immunoassay for small molecules becomes widely accepted and applied, new challenges involving more complex chemicals in more difficult matrixes arise. The integration of “classical” analytical chemistry with immunochemistry can provide new techniques and approaches useful in discovering the movement, mode of action, and ultimate impact of certain chemicals on humans and the environment.
Agarose Gel Electrophoretic Detection of Six β-Lactam Antibiotic Residues in Milk
Authors: Cutting Jeffrey H , Kiessling William M , Bond Fred L , Mccarron James E , Kreuzer Karen S , Hurlbut Jeffrey A , Sofos John N
Published: February 2020

An electrophoretic method coupled with bioautography was developed for detection and identification of penicillin G, ampicillin, amoxicillin, cloxacillin, cephapirin, and ceftiofur residues in milk. The method uses a 2% agarose gel for electrophoresis, an overlay of PM indicator agar seeded with Bacillus stearothermophilus var. calidolactis, and incubation at 55°C for 16–18 h. The new method separated and detected residues in milk at the levels of concern for the Food and Drug Administration (FDA) for penicillin G (5 ppb), cephapirin (20 ppb), and ceftiofur (50 ppb). The method also detected ampicillin, amoxicillin, and cloxacillin at 20,30, and 30 ppb, respectively, but these levels are above those of concern for FDA (10 ppb).
Determination of Monensin in Edible Bovine Tissues and Milk by Liquid Chromatography
Authors: Moran John W , Turner James M , Coleman Mark R
Published: February 2020

A method is described for detection and quantitation of monensin in bovine tissues by liquid chromatography (LC) with postcolumn derivatization (PCD) with vanillin. Monensin is extracted from the tissues by homogenization with methanol–water and is isolated and concentrated by liquid–liquid partition and sorbent extraction with silica gel. Monensin is mixed postcolumn with vanillin under acidic conditions and heated, and the resulting products are measured by a variable-wavelength detector at 520 nm. The method has a limit of quantitation of 5 ppb monensin in milk and 25 ppb monensin in bovine muscle, liver, kidney, and fat. Standard recovery over the levels and matrixes tested ranged from 80 to 88%. The method is an improvement in specificity, accuracy, and analysis time over existing monensin residue methods for bovine tissues.
Evaluation of a Postcolumn Electrochemical Reactor for Oxidation of Paralytic Shellfish Poison Toxins
Authors: Lawrence James F , Wong Barbara
Published: February 2020

A liquid chromatographic method using a postcolumn electrochemical reactor that oxidizes paralytic shellfish poison toxins to fluorescent derivatives has been developed. Several experimental parameters, including pH and oxidation potential, were investigated. For nonhydroxylated toxins, the sensitivity improved with increasing pH and voltage. At optimum operating conditions, the sensitivity for saxitoxin and gonyautoxins 2 and 3 was an order of magnitude greater than that for neosaxitoxin and B1 and 2 orders of magnitude greater than that for B2. The limit of detection for saxitoxin was 0.10 ng (signal-to-noise ratio, 3:1). Electrochemical oxidation products were similar to those formed in the prechromatographic periodate oxidation method. Shellfish and plankton extracts were analyzed with the electrochemical system, and results agreed well with those obtained with established methods. Shellfish samples contaminated at the regulatory limit of 0.8 μ/g were readily analyzed by the method.
Immunoaffinity Column Coupled with Liquid Chromatography for Determination of Fumonisin B1 in Canned and Frozen Sweet Corn
Authors: Trucksess Mary W , Stack Michael E , Allen Shantae , Barrion Noel
Published: February 2020

A modified liquid chromatographic (LC) method for determining fumonisin B1 (FB1) in corn was applied to canned and frozen sweet corn. The corn is extracted with methanol–water (8 + 2), and the extract is filtered. The filtrate is diluted with water and passed through an immunoaffinity column. After the column is washed with water, FBi is eluted with methanol–water (8 + 2). The eluate is evaporated to dryness by using a vacuum concentrator, and the residue is dissolved in acetonitrile–water (1 +1). FB1 is derivatized with o-phthaldialdehyde. The derivative is separated on a reversed-phase C18 LC column using acetonitrile–water–acetic acid (50 + 50 + 1) and quantitated with a fluorescence detector. Recoveries of FB1 from canned and frozen corn spiked over the range of 50–200 ng/g were 76–88%. The limit of determination was about 25 ng/g, and the limit of detection was about 4 ng/g. The method was applied to 97 commercial canned and frozen sweet corn samples collected from different areas of the United States. Sixty samples contained no FB1. Low levels (trace–82 ng FB1/g corn) were found in 35 samples; 235 ng FB1/g was found in 1 canned corn sample, and 350 ng FB1/g was found in 1 frozen corn sample.
Liquid Chromatographic Method for Determination of Biogenic Amines in Fish and Fish Products
Authors: Veciana-Nogues María Teresa , Hernandez-Jover Teresa , Marine-Font Abel , Vedal-Carou María Del Carmen
Published: February 2020

A liquid chromatographic method with postcolumn derivatization is described for determination of biogenic amines in fish and fish products. Histamine, tyramine, serotonin, β-phenylethylamine, tryptamine, putrescine, cadaverine, agmatine, spermine, and spermidine can be determined in less than 60 min. Routine sample preinjection treatment implies only 2 extractions with 0.6N perchloric acid and filtration through a 0.45 μm filter. Lack of interferences from volatile amines, amino acids, and dipeptides was verified. Results of reliability study were satisfactory. The proposed method was linear for each amine between 0.25 and 8.00 mg/L. Average recoveries ranged from 92 to 103%. Precisions (coefficients of variation) ranged from 0.70 to 9.75%. Determination limits were ≤1 mg/kg. A modification in LC conditions was necessary to apply the method to ripened fish products to avoid interferences from food matrixes. In addition, stability of biogenic amines in fresh anchovies and hake during short-term frozen storage was studied. Results showed that, except for agmatine, frozen storage is suitable for keeping samples before analysis.
Quality Assurance in Weighing
Authors: Kenyon Allen S , Black J C , Layloff Thomas P
Published: February 2020

Weighing is the most used step in any analytical procedure, and the balance is the one essential piece of laboratory equipment in all analyses. Yet weighing is a common source of error in final analytical results and can be difficult to detect. Analysts may become complacent and expect all weighings to be accurate. Our laboratory experienced a problem in weighing and found that the principal error was due to drift. The ensuing investigation into the cause led to a procedure for reducing drift, which, in turn, ensured accurate weighings that have improved quality assurance in our total operations.