bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Nonylphenol and Octylphenol Ethoxylates in Effluent by Liquid Chromatography with Fluorescence Detection
Authors: Mackay Lindsey G , Croft Marguerite Y , Selby David S , Wells Robert J
Published: February 2020

A robust liquid chromatographic (LC) method with fluorescence detection is described for the simultaneous determination of the nonionic surfactants nonylphenol ethoxylates (NPEO) and octylphenol ethoxylates (OPEO) in effluent samples from sewerage treatment plants. The cleanup procedure uses graphitized carbon black solid-phase extraction cartridges. A subsequent derivatization step removes matrix interferences that are no longer fluorescent after acetylation. The efficiency of the method is monitored by inclusion of a surrogate compound designed and synthesized specifically for this purpose. The limit of reporting for the method is 5 μg/L for 100 mL effluent samples. Studies on confirmation of identity of NPEO and OPEO by electrospray LC/mass spectrometry are described.
Gas Chromatographic Determination of Acephate in Technical Material and Soluble Powder Formulations: Collaborative Study
Authors: Kovacs Martin F , Michael Wehr H ,   Collaborators:, Belkind B A , Stein J , Bennett O O , Torkzadeh M , Bernes A , Galoux M , Bura L , Burns A , Fujie G , Gomez F , Lim T , Manso L , Parsons A H , Reeves P , Slahck S C , Harbin D , Sneddon R , Menasco M , Takahashi K , Fukunaga T
Published: February 2020

A gas chromatographic (GC) method was developed for quantitation of acephate (Orthene) in technical material and soluble powder formulations. Acephate is an organophosphate with broad spectrum contact and systemic insecticidal properties. Fourteen collaborators from 8 countries participated in a collaborative study of the method. Collaborators were provided with the method; samples of technical acephate and formulated soluble powder containing 95-99% and 71-75% acephate, respectively; an acephate reference standard; and internal standard. Samples were weighed, diluted to volume with internal standard, and quantitated by using GC peak area ratios. Relative standard deviation values for reproducibility (RSDR) were 1.03-2.55 for 95-99% technical acephate and 1.36-2.73 for formulated soluble powder containing 71-75% acephate. The GC method for determination of acephate in technical material and soluble powder formulations has been adopted by AOAC INTERNATIONAL
Assurance Enzyme Immunoassay for Detection of Enterohemorrhagic Escherichia coli 0157:H7 in Selected Foods: Collaborative Study
Authors: Feldsine Philip T , Falbo-Nelson Maria T , Brunelle Sharon L , Forgey Robin L ,   Collaborators:, Al-Hasani S , Ball C , Beatty S , Blanchfield B , Bowen B , Bremer N , Brookman D , Brookman S , Brushaber M , Bryant J , Bryant D , Bryant R , Chlebowski E T , Copeland F , Culak D A , Dalley E , Destro C , Finkenbiner D , Frissora R , Fung D Y C , Garcia G R , Gray M R , Hagen C J , Harshavardhan T , Hart-Thakur R , Inami G , Johnson S , Kandakai L V , Lessard D , Lin S , Liu V , Matiuck S , McAteer L , Miller L , Moon B , Nasri H , Pack L , Pilot K , Price C , Pruett P , Ramirez C , Richter D , Schmieg J A , Schultz G , Sloan E M , Sprague D M , Tebay D , Tomer J , Tuncan E , Warburton D , Watson M , West D
Published: February 2020

Five foods types were analyzed by the Assurance EHEC (Escherichia coli 0157:H7) enzyme immunoassay (EIA) and by the Bacteriological Analytical Manual (BAM) culture method. Each sample of each food type at each inoculation level was simultaneously analyzed by both methods. A total of 21 laboratories representing state and federal government agencies and private industry in the United States and Canada participated. Samples were inoculated with E. coli 0157:H7, except for one lot of poultry that was naturally contaminated. A total of 1304 samples and controls were analyzed and confirmed, of which 473 were positive and 818 were negative by both methods. Thirteen samples were positive by BAM but negative by EIA. Because of the study design, it was not possible for the BAM method to produce false-negative or falsepositive results. The Assurance method for detection of E. coli OI57:H7 in selected foods has been adopted first action by AOAC INTERNATIONAL.
Multivariate Statistics as a Classification Tool in the Food Laboratory
Authors: Kaufmann Anton
Published: February 2020

Multivariate statistics is a powerful tool for answering complex questions like the geographical origin of wine. Instead of expensive tests such as stable isotope measurements, less costly routine analysis data can be used. Problems like the choice of analysis parameters, the size of reference data, and the best suited statistical technique are addressed. Multivariate statistics was used very successfully with real samples in an official Swiss wine-tasting championship. Although the examples presented in the paper deal with wine, the principles, opportunities, and shortcomings may also apply to other food products.
Determination of Histidine by Atomic Absorption Spectroscopy
Authors: El-Brashy Amina M , Al-Ghannam Sheikha M
Published: February 2020

Two atomic absorption spectrophotometric methods are described for determination of histidine. The first is based on reaction of histidine with mercury(II) ions in phosphate buffer (pH 9). The second is based on reaction of histidine with iron(III) ions in neutral medium. The precipitate formed in both methods is separated by centrifugation, and the equivalent Hg(II) or Fe(III) ions as well as surplus ions in the filtrate are determined by atomic absorption at 253.6 and 248.3 nm for Hg and Fe, respectively. Amounts of histidine are calculated from calibration graphs prepared by standard addition methods or by regression equations. The procedures were successfully applied to assay of histidine in dosage forms after thin-layer chromatographic separation. Results compared favorably with those of the official method.
Predictive Microbiology of Dairy Products: Influence of Biological Factors Affecting Growth of Listeria monocytogenes
Authors: Brouillaud-Delattre Agnes , Maire Murielle , Collette Catherine , Mattei Cesar , Lahellec Cecille
Published: February 2020

The growth potential of Listeria monocytogenes was evaluated at low temperature in sterilized milk and raw dairy products. Sterilized and raw milk were inoculated with different strains of L. monocytogenes in 2 physiological states and at various contamination levels. Raw cheese was naturally contaminated with Listeria spp. The results suggest that some biological factors influence the growth capacity of L. monocytogenes in dairy products. Significant strain effect was observed at low temperature whatever the growth medium. By contrast, no inoculum effect was observed in the 3 dairy products. In raw matrixes, growth of L. monocytogenes was influenced greatly by bacterial interactions and physiological state of inoculum cells.
Use of the Microwave-Assisted Process in Extraction of Fat from Meat, Dairy, and Egg Products under Atmospheric Pressure Conditions
Authors: Paré J R Jocelyn , Matni Gisèle , Bélanger Jacqueline M R , Li Ken , Rule Cari , Thibert Benoît , Yaylayan Varoujan , Liu Zhun , Mathé Daniel , Jacquault Patrick
Published: February 2020

Fat from meat, dairy, and egg products was extracted by using Microwave-Assisted Process (MAP) technology under atmospheric pressure conditions. Fat content was determined gravimetrically after extraction with microwaves and organic solvents that are transparent to microwaves relative to the sample. (In situ hydrolysis was performed for dairy and egg products.) Fat from the food sample migrated completely to the extractant when samples were irradiated with focused microwave for a total of 3 min for meat products, 1 min for dairy products, and 4 min for egg products. Unlike current methods used for determining fat in meat products, the microwave-assisted method does not require a dry sample, because moisture in the sample (around 75%) enhances the efficiency of extraction. No preprocessing was required for meat samples other than homogenization, which is critical, as it is for other current methods. In addition to speed and ease of use, the features of this technology are low solvent consumption, low energy consumption, reproducibility, and recoveries similar to or even better than those of conventional extraction methods.
Quantitation of Aflatoxin B1-N7-Guanine Adduct in Urine by Enzyme-Linked Immunosorbent Assay Coupled with Immunoaffinity Chromatography
Authors: Vidyasagar Tfflrumurthy , Vyjayanthi Vadapalli , Sujatiia Nayak , Rao Beedu Sashidhar , Bhat Ramesh Venkataramana
Published: February 2020

IndiaA specific and sensitive method to quantitate aflatoxin B1-N7-guanine adduct in urine samples by immunoaffinity chromatography coupled with indirect competitive enzyme-linked immunosorbent assay (ELISA) is reported. A novel in vitro method to synthesize an antigen (bovine serum albumin-guanine-aflatoxin B1) and its use to produce polyclonal antibodies specific to the hapten aflatoxin B-N7-guanine are discussed. An indirect competitive ELISA developed to quantitate aflatoxin adduct showed a 50% inhibition at 15.6 pmol aflatoxin B1-N7-guanine (y=66.73+ (-19.8)x, r=-0.997). Interference by aflatoxin B1 was less than 5%, and no interference by guanine, aflatoxin Gι and aflatoxin M1 was observed. An immunoaffinity column was also developed, by using these polyclonal antibodies, for single-step purification of aflatoxin B1-N7-gua-nine. The immunoaffinity column and the indirect competitive ELISA were evaluated and validated by quantitation of aflatoxin B1-N7-guanine in urine from rats dosed with aflatoxin B1 (1 mg/kg body weight). Spiking studies with standard aflatoxin B1-N7-guanine adduct at 2 and 4 μg/mL phosphate- buffered saline gave 96 and 100% recoveries, respectively, for immunoaffinity cleanup column. The method also was tested successfully for quantitating aflatoxin B1-N7-guanine adduct in spiked human urine. Recoveries of the adduct were 79-90%.
Multiresidue Method for Analysis of Pesticides in Liquid Whole Milk
Authors: Bennett Dianne A , Chung Alex C , Mark Lee S
Published: February 2020

A multiresidue method to analyze liquid whole milk for 59 compounds was developed. The method involves a single extraction and cleanup strategy for many classes of compoundsorganophosphorus compounds (OPs), organochlorine compounds(OCs), yv-methylcarbamates (MCs), etc. Initial extraction is performed with ethanol-ethyl acetate as solvent and sodium sulfate as drying agent. A portion of the extract is concentrated to an oily consistency, and target analytes are partitioned into acetonitrile. Further cleanup is achieved by sequential solid-phase extractionsoctadecyl (C18)-bonded silica cartridges followed by aminopropyl (NH2)- bonded silica cartridges. The solvent is exchanged to acetone for analysis by gas chromatography (GC) with electrolytic conductivity, flame photometric (FPD) or mass spectrometric (MS) detection and to methanol for analysis by liquid chromatography with postcolumn derivatization. Typical limits of detection (LODs; peak-to-peak signal-to-noise ratio ≥3) were 0.3 ppb for OPs, 0.9 ppb for OCs and MCs, and 9 ppb for mass-selective detection. From the level of quantitation (LOQ = 3.33 x LOD) to 10 x LOQ, linear instrument response was observed for all detectors except the FPD which required a second- order calibration curve. Average recoveries for spikes at the LOQ ranged from 69 to 127%, with standard deviations of about 10%. Similar accuracy and precision were observed for fortifications at 5 x LOQ and 10 x LOQ. The method was used to analyze 20 milk samples from various liquid milk processing plants. Incurred residues were confirmed by high-resolution GC/MS and GC/MS/MS.
Use of Total Organic Carbon Analysis and Fourier-Transform Infrared Spectroscopy to Determine Residues of Cleaning Agents on Surfaces
Authors: Biwald Christopher E , Gavlick Walter K
Published: February 2020

Total organic carbon (TOC) analysis can be used in many cases as a nonspecific method of determining trace levels of organic residue on manufacturing equipment before and after cleaning. In this study, a swab sampling method followed by TOC analysis is used to determine organic residue levels associated with alkaline and acidic cleaning agents on a stainless steel surface. The alkaline cleaning agent was nonvolatile, resulting in favorable TOC analysis and validation. The acidic cleaning agent was very volatile, requiring more skilled sample handling and resulting in a more difficult validation. Fourier-transform infrared (FTIR) spectroscopy with a grazing-angle sample attachment can be used for direct surface measurements of cleaning-agent residues on a stainless steel surface. FTIR spectroscopic studies complement and support the TOC studies. One band chosen for each cleaning agent was monitored throughout the leaning process. cidic and alkaline
Determination of Emamectin Benzoate in Freshwater and Seawater at Picogram-Per-Milliliter Levels by Liquid Chromatography with Fluorescence Detection
Authors: Hicks Michael B , Payne Lori D , Prabhu Sunil V , Wehner Teresa A
Published: February 2020

Emamectin benzoate is a very effective agricultural insecticide applied to various crops at very low rates. A method to analyze emamectin benzoate in seawater and freshwater was developed. The method yields good recoveries with limits of quantitation of 20 pg/mL for freshwater and 24 pg/mL for seawater (signal-to-noise ratio [S/N] ≥ 10). The limit of detection is 10 pg/mL (S/N ≥ 3). Emamectin benzoateis concentrated from a 50 mL sample on a C8 solid-phase extraction cartridge and eluted with 1% ammonium acetate in methanol. The eluate is evaporated to 1 mL, diluted with 1 % ammonium acetate in water, and partitioned into ethyl acetate. The ethyl acetate extract is concentrated to about 0.5 mL and diluted to about 1 mL with acetonitrile. 1-Methylimidazole is added to the diluted sample, and then trifluoroacetic anhydride is added to form a fluorescent derivative. The derivatized sample is injected onto a reversed-phase liquid chromatographic system equipped with a fluorescence detector. Overall method recoveries for concentrations ranging from 20 to 1010 pg/mL were 84 ± 9.5% for tap water and 89 ± 11% for seawater. These results are equivalent to recoveries previously obtained with a more elaborate method (90 ± 8.8% for freshwater). Controls were free of interferences or coeluting impurities. Fluorescence detection provides high sensitivity and selectivity, enabling trace-level analysis.
Evaluation of Organophosphorus Pesticide Residues in Citrus Fruits from the Valencian Community (Spain)
Authors: Torres Carmen M , Picó Yolanda , Marín Rosa , Mañes Jordi
Published: February 2020

Approximately 200 citrus samples from markets of the Valencian Community (Spain) were analyzed to establish their residue levels in 12 organophosphorus pesticide residues during the 1994-1995 campaign. The organophosphorus pesticides carbophenothion, chlorpyriphos, chlorfenvinphos, diazinon, ethion, fenitrothion, malathion, methidation, methylparathion, phosmet, quinalphos, and tetradifon were simultaneously extracted by matrix solidphase dispersion and determined by gas chromatography- mass spectrometry using selected ion monitoring mode. A total of 32.25% contained pesticide residues and 6.9% exceeded the European Union Maximum Residue Levels (MRLs). The pesticides found in the samples with residues above MRLs were carbophenothion, ethion, methidathion, and methyl parathion. Lower level residues of these and the other pesticides studied (except diazinon) were frequently found. The estimated daily intake of the 12 organophosphorus pesticide residues during the studied period was 4.87 x 10−4 mg/kg body weight/day. This value is lower than the provisional tolerances dairy intakes proposed by the Food and Agriculture Organization and the World Health Organization.
Determination of Fish Flesh Content in Frozen Coated Fish Products (Modification of AOAC Official Method 971.13): Collaborative Study
Authors: Dobson Jane E Fox , McClure Foster D , Rainosek Alvin P ,   Collaborators:, Dashiell K , Fox Dobson J , Harris M , Jones R , Maher E , McGuire A , Noonan J , Petrillo T , Picard M , Romero C , Sabia M
Published: February 2020

An intralaboratory1collaborative study evaluated a modified version of AOAC Official Method 971.13 for determining the fish flesh content (FFC) in frozen coated fish products by comparing it with the on-line method. Eleven collaborators analyzed 36 products (a total of 6336 test samples). Each product targeted one of 4 percent fish flesh (PFF) levels (35,50,65, and 80). Products were manufactured from one of 3 raw materials (fillet blocks, minced blocks, and natural fillets) and processed in one of 4 forms (sticks, portions, formed portions, and fillets) and one of 4 styles (raw breaded, batter-dipped, precooked, and fully cooked). Each “official” test sample was tracked through the processing system and weighed (1) before battering and/or breading and, depending on product style, before frying; and (2) after battering and/or breading and, depending on product style, after frying; so that it served as its own control.
Mainstream Smoke Collection by Electrostatic Precipitation for Acid Dissolution in a Microwave Digestion System Prior to Trace Metal Determination
Authors: Rhoades Charles B , White Ralph T
Published: February 2020

A method is described for collection and preparation of mainstream smoke condensate from cigarettes for determination of trace metal constituents. A sample of mainstream smoke was collected from 300 cigarettes in a final volume of 25 mL. Extremely clean laboratory conditions during sample preparation were essential to avoid contamination and improve precision and accuracy for trace element determination. The clean laboratories maintained a positive pressure of HEPA-filtered air with constant temperature and humidity control. Mainstream cigarette smoke was collected by electrostatic precipitation (EP) on a modified rotary smoking machine located in a wooden CORESTA cabinet. The EP unit was equipped with a high tension generator supplying 17.5 kV to a tungsten electrode followed by 2 secondary acid traps. Samples were collected under 2 smoking regimens: FTC (35 mL puff volumes, one puff every 60 s, and puff duration 2 s) and “Extreme” (75 mL puff volumes, one puff every 35 s, puff duration 2 s). Condensate was extracted from collection tubes with methanol into Teflon microwave digestion vessels and evaporated in an environmental evaporation chamber (EEC). The EEC provided an ultraclean environment for sample evaporation and predigestion steps that eliminated most of the sample matrix. The remainder was decomposed in a programmable closed vessel microwave digestion system. Digested sample solutions were analyzed by graphite furnace atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry for aluminum, arsenic, cadmium, chromium, nickel, and silicon.
Determination of Water in Forages and Animal Feeds by Karl Fischer Titration
Authors: Erem Terri Van , Thiex Nancy , Pohmer Jörg , Poffenbarger Michael W , Smith Victor , Patel Elena
Published: February 2020

Oven methods for determining moisture (volatiles) in forages and other animal feeds are empirical. The moisture concentration obtained depends upon the time and temperature the sample was dried and is influenced by the presence of other volatiles than water. A validated reference method to measure water in forages and animal feeds could be used to evaluate the appropriateness of oven methods for various types of animal feeds and forages. Karl Fischer titration is a well-established method for determining water. However, thorough extraction of water from forages and feeds is a challenge because they often contain cellular structures that release water slowly. Water was successfully extracted into methanol-formamide (50 + 50) by high-speed homogenization and then titrated directly at 50 C with a one-component Karl Fischer reagent based on imidazole. The method is described in detail, results of day-to-day repeatability and laboratory-to-laboratory reproducibility are reported, and preliminary comparison data between oven methods are provided.
Simple, At-Site Detection of Diethylene Glycol/Ethylene Glycol Contamination of Glycerin and Glycerin-Based Raw Materials by Thin-Layer Chromatography
Authors: Kenyon Allen S , Xiaoye Shi , Yan Wang , Wai Har Ng , Prestridge Robert , Sharp Kirsten
Published: February 2020

This paper describes a rapid, inexpensive thin-layer chromatographic (TLC) method that separates diethylene glycol (DEG) from glycerin and other glycols. Studies with collaborating laboratories of the World Health Organization have shown that about 6% DEG in glycerin and about 2% DEG in acetaminophen (paracetamol) elixirs may be detected by direct visual inspection of the developed TLC sheets. Staining the sheet permits detection of DEG at less than 0.1%. The method costs less than $1.00 per test and takes 20 min by visual inspection, longer when staining is required. The visual method can be performed without laboratory facilities by personnel having little previous training. Samples testing positive by the visual method can be submitted to a laboratory for confirmation and quantitation of DEG.
Contemporary Thin-Layer Chromatography in Pharmaceutical Quality Control
Authors: Renger Bernd
Published: February 2020

abstract

The progress in layers, instrumentation, and the development of automated scanning densitometers have led to a remarkable improvement of the features of thin-layer chromatography (TLC) and especially its high performance version (HPTLC). Contemporary TLC or HPTLC combines the techniques' inherent advantages which include high sample throughput, simultaneous processing of standards and samples, flexibility, easy postchro matographic visualization techniques, and the ability to handle complex or crude samples with minimum sample cleanup—with improved selectivity, sensitivity, and accuracy. It is a very economical chromatographic technique that competes with and complements HPLC. Development and validation of procedures can be performed rapidly in full accordance with all current international guidelines.
Comparison of the VITEK Gram-Negative Identification Card and an Enhanced Version for Identification of Salmonella, Escherichia coli, and Other Enterobacteriaceae:. Method Modification
Authors: Gravens Carol K
Published: February 2020

abstract

Comparison of the VITEK® Gram-Negative Identification Card (GNI) was compared to an enhanced version of the test kit, the GNI+ Card. The GNI Card is an official AOAC method (991.13) for identification of Salmonella, Escherichia coli, and other Enterobacteriaceae in foods. In this comparison 5 replicates of 124 gram-negative stock culture strains were evaluated to determine equivalency. Isolates were obtained primarily from food sources, with 108 of the isolates representing 15 genera within the family Enterobacteriaceae. Overall agreement between the GNI Card and the GNI+ Card was 98.2%. Of the 23 strains of Salmonella tested, the longest identification time for the GNI Card was 10 h, with 43.5% of the strains identifying in 4 h or less. The longest identification time of the same Salmonella strains tested with the GNI+ Card was 8 h, with 95.7% of the strains identifying within 4 h. The GNI+ Card provided increased speed of identification while retaining the accuracy of the GNI Card. The GNI method for identifying Salmonella, Escherichia coli, and other Enterobacteriaceae was approved as a method modification by AOAC INTERNATIONAL.
A Kinetic Approach for Determination of Cefadroxil in Pharmaceuticals by Alkaline Hydrolysis
Authors: Helaleh Murad I H , Abu-Nameh Eyad S M
Published: February 2020

abstract

A new, simple, and sensitive kinetic spectrophotometric method is described for analysis of cefadroxil by measurement of its absorbance at 470 nm after hydrolysis with NaOH at 80°C. Studies of the method's precision and accuracy gave a standard deviation of 0.44 μg/mL and a relative standard deviation of 1.93%. The method determines cefadroxil over the concentration range 10- 100 ug/mL. Calculated activation parameters were 12.42, 25.54, 26.25, and 69.00 Kcal/mole for AE*, AG*, Ahf, and AS*, respectively. Cefadroxil concentrations can be determined from the regression line equation y = 0.627x- 8.14 x 10"5, with a correlation coefficient of <1.0000. The method was validated by assay of cefadroxil in commercial capsules and tablets. Recoveries of common excipients were 99.6,100.00, 99.2, 99.6, and 100.4% for lactose, glucose, starch, sucrose, and fructose, respectively. Results were compared with those of a reference method. Calculated f and F values indicate no significant difference between the 2 methods. The degradation products of cefadroxil do not affect determination of cefadroxil.
Routine Analysis of Proteins by Kjeldahl and Dumas Methods: Review and Interlaboratory Study Using Dairy Products
Authors: Wiles Peter G , Gray Ian K , Kissling Roger C ,   Collaborators:, Delahanty C , Evers J , Greenwood K , Grimshaw K , Hibbert M , Kelly K , Luckin H , McGregor K , Morris A , Petersen M , Ross F , Valli M
Published: February 2020

abstract

The Kjeldahl and Dumas (combustion) methods were compared in 11 laboratories analyzing samples of milk, skim milk powder, whole milk powder, whey protein concentrate, infant formula, casein, caseinate, 2 reference compounds (glycine and EDTA), and a secondary reference skim milk powder. The comparison was conducted by using international standards where applicable. Overall means were 8.818 g N/100 g by the Kjeldahl method and 8.810 g N/100 g by the Dumas method. No evidence was found for a consistent bias between methods that may be of concern in the trading of dairy produce. A review of more than 10 related trials revealed a lack of consensus in the bias between the 2 methods, suggesting that differences in methodology and sources of systematic error may be contributors. For samples containing >2 g N/100 g, the Dumas relative repeatability and reproducibility standard deviations were consistently about 0.35 and 0.75%, respectively, whereas the corresponding Kjeldahl values declined generally with N content and were significantly larger. The Dumas precision characteristics may be due to the dominance of Leco analyzers in this trials, and in most other recent trials, rather than an inherent method attribute. Protein determination methods for dairy products need to be reviewed and updated. The Dumas method needs Codex Alimentarius status as a recognized test method.
Analysis of Fumonisin Bi and Its Hydrolysis Product in Tortillas
Authors: Stack Michael E
Published: February 2020

Fumonisins are toxic metabolites of Fusarium moniliforme, a fungus that occurs widely in corn. Fumonisins cause leukoencephalomalacia in horses and pulmonary edema in swine and have been suggested as a possible cause of an increased incidence of neural tube defects among people living along the Texas-Mexico border. As part of an effort to determine levels of fumonisins in human food, a liquid chromatographic (LC) method was devised for determining fumonisin Bi (FB1) and the total hydrolysis product of FB1 (HB1) in tortillas. The method uses acetonitrile-0.1M phosphate buffer (pH 3; 1 +1) extraction, solidphase C18 cleanup, ophthalaldehyde and 2-mercaptoethanol derivatization, and reversed-phase LC. Average recoveries from tortillas spiked with FB1 and HB1 at 250, 500, and 1000 ng/g were 86.5℅ for FB1 and 82.6℅ for HB1. Tortillas (54) and masa (8) from the Texas-Mexico border were analyzed for FB1 and HB1. Average amounts of FB1 and HB1 in tortillas were 187 and 82 ng/g, respectively. Average amounts of FB1 and HB1 in masas were 262 and 64 ng/g, respectively. The results show that fumonisin B1 and its hydrolysis product are present in tortillas consumed by a population experiencing an increased incidence of neural tube defects.
Analysis of Fumonisins and Alternaria alternata Toxin by Liquid Chromatography-Enzyme-Linked Immunosorbent Assay
Authors: Yu Feng-Yih , Chu Fun S
Published: February 2020

Use of a direct competitive enzyme-linked immunosorbent assay (ELISA) as a postcolumn monitoring system after liquid chromatography (LC) is described for analysis of different fumonisin analogs. Without cleanup and derivatization, sample extracts are directly injected into a C18 reversedphase column and then subjected to LC. Fractions (0.5 mL each) are collected and then analyzed by ELISA. LC using a water-methanol gradient separated the 3 major fumonisins FmB1, FmB2, and FmB3, and as low as 0.1 ng FmB1 could be detected. Recovery of FmB1 added to ground corn (100-1000 ng/g) and then extracted with CH3CNH2O (1 + 1, v/v) was 78.8℅. Analysis of fumonisins in one starch and 14 naturally contaminated corn samples showed that FmB1 was the major fumonisin. Ten samples also were contaminated with FmB2, but only 2 samples were contaminated with FmB3. The method also was used to analyze extracts from cultures of 3 Alternaria alternata(AAL) strains. Both FmB1 and the AAL toxin TA were detected in the culture extracts, and their amounts varied considerably with the cultures tested.
Determination of Phenylurea Herbicide Residues in Vegetables by Liquid Chromatography after Gel Permeation Chromatographyand Florisil Cartridge Cleanup
Authors: Sannino Anna
Published: February 2020

A liquid chromatographic method for quantitative determination of 9 phenylurea herbicide residues (metoxuron, metobromuron, monolinuron, chlortoluron, isoproturon, diuron, linuron, chloroxuron, and neburon) in potatoes, carrots, and mixed vegetables is described. Samples are extracted with acetone, partitioned with ethyl acetate-cyclohexane (50 + 50, v/v) and cleaned up by gel permeation chromatography with ethyl acetate-cyclohexane (50 + 50, v/v) as eluant. A small column (1 cm id) packed with Biobeads SX3 resin is used to reduce solvent consumption and analytical time. After solid-phase extraction on a Florisil cartridge, herbicide residues are successfully separated on a C18 column by gradient elution and determined by UV detection at 242 nm. Average recoveries of 9 compounds from different samples range from 70 to 98% at 0.010 and 0.100 mg/kg fortification levels. Quantitation limits are 0.010 mg/kg
Determination of Diethanolamine and N-Nitrosodiethanolamine in Fatty Acid Diethanolamides
Authors: Chou Hardy J
Published: February 2020

Diethanolamine (DEA) is a precursor of N-nitrosodiethanolamine (NDELA), an animal carcinogen. A gas chromatographic (GC) method was developed for determining DEA in fatty acid diethanolamides that are commonly used in cosmetic products. Methanolic solutions of the amides were analyzed by GC with flame ionization detection on either a wide-bore methyl silicone (Rtx-1) or 95% dimethyl- 5% diphenyl polysiloxane (SPB-5) capillary column. Recovery of DEA from fatty acid dialkanolamides at fortification levels of 0.50,1.00, and 5.00% ranged from 94 to 100%. In a survey of commercial fatty acid diethanolamides, DEA was found at levels ranging from 1.1 to 14.0%, and most were in good agreement with manufacturer's DEA specifications. Fatty acid diethanolamides also were analyzed for NDELA by liquid chromatography interfaced to a thermal energy analyzer. Recovery of NDELA from fatty acid diethanolamides at fortification levels of 50,100, and 200 ppb averaged 95%. No NDELA was found in any of the fatty acid diethanolamide samples analyzed
Determination of Pseudoephedrine Hydrochloride and Carbinoxamine Maleate in Combination Drug Formulation by Liquid Chromatography
Authors: Mansour Ali M
Published: February 2020

An isocratic, reversed-phase liquid chromatographic (LC) method was developed for simultaneous determination of pseudoephedrine hydrochloride (I) and carbinoxamine maleate (II) in a pharmaceutical dosage form. Analysis was conducted on a CN column (10μm), with a mobile phase consisting of acetonitrile-methanol-phosphate buffer (pH 5.3)-water (140 + 170 + 40 + 100) and at a detection wavelength of 262 nm. The method was validated for linearity, precision, system reproducibility, and accuracy. Recoveries at 80-120% of labeled claim ranged from 97.4 to 100.7% and from 98.5 to 100.2% for I and II, respectively. Results were linear (correlation coefficient, r > 0.9995 for I in the range 250-750 (μ/mL and r > 0.9999 for II in the range 20-60 μg/mL)
Rapid Gas Chromatographic Method for Simultaneous Determination of Cholesterol and α-Tocopherol in Eggs
Authors: Botsoglou Nickos , Fletouris Dimitrios , Psomas Ioannis , Mantis Antonios
Published: February 2020

A new method was developed for simultaneous determination of cholesterol and α-tocopherol in eggs. It involves rapid and simple sample preparation accomplished in one tube and chromatographic separation that does not require derivatization of analytes. Total analysis time per sample is 40 min. Labor, cost, and use of hazardous chemicals are minimized. To ensure selectivity, accuracy, and precision, critical analytical parameters were investigated. Overall recoveries were 98.8 and 99.2% for cholesterol and α-tocopherol, respectively. Linearity was acceptable for both analytes (r = 0.9964 for cholesterol and 0.9996 for α-tocopherol) in the fortification range examined. Precision data based on within-day and between-days variation gave overall relative standard deviations of 2.0% for cholesterol and 7.0% for α-tocopherol.The method was applied successfully for quantitation of cholesterol and α-tocopherol in eggs.
Determination of Phosphine Residues in Whole Grains and Soybeans by Ion Chromatography via Conversion to Phosphate
Authors: Carlson Marvin , Thompson Richard D
Published: February 2020

An ion chromatographic (IC) method was developed for determining phosphine (PH3) in whole grains (barley, corn, oats, rice, rye, and wheat) and soybeans. The method converts phosphine to phosphate (i.e., orthophosphate) and isolates the phosphate by IC with eluent-suppressed conductivity detection. Recoveries of unbound phosphine by the method were similar to those obtained by an established colorimetric method for 7 different products fortified at 3 levels. Mean recoveries were low (i.e., 30-60%) and varied with product type and level of fortification. Recoveries of PH3 from previously fumigated products fortified with aluminum phosphide ranged from 19.0% for barley fortified at 0.734 ppm to 88.3% for corn fortified at 1.691 ppm. Precision data from 3 products based on replicate analyses (n = 4 or 5) gave relative standard deviations of 1.78-4.66% for mean laboratory-fumigated PH3 levels of 0.679-1.309 ppm. Estimated limits of detection (LOD) and quantitation (LOQ) for PH3 were 0.010 μg/g (10 ppb) and 0.0275 μg/g (27.5 ppb) at signal-to-noise ratios (S/N) of 4:1 and 10:1, respectively. These values were also determined for a nonchemically suppressed IC system with LOD of 0.02 μg/g (20 ppb) and LOQ of 0.055 μg/g (55 ppb) at S/N of 4:1 and 10:1, respectively. Phosphate response was linear over the concentration range equivalent to 0.30-10.0 fig P/mL, with a mean correlation coefficient of 0.9988 based on replicate standard curves. The relationship of product composition to recovery from various products was also examined.
Determination of Neutral Lactase Activity in Industrial Enzyme Preparations by a Colorimetric Enzymatic Method: Collaborative Study
Authors: Engelen Adrianus J , Randsdorp Peter H G ,   Collaborators:, Cassaigne R , Dutta S M , Harboe M , Harju M , van der Heeft F C , Hirota T , McKellar R C , Playne M , Rogers D , San José C , de Vrese M
Published: February 2020

Thirteen laboratories participated in a collaborative study to validate a colorimetric assay for determining neutral lactase activity in industrial enzyme preparations. Each laboratory received 5 duplicate samples with activity levels of 2000 and 5000 neutral lactase units provided by 4 commercial suppliers. Two laboratories did not return results. Method performance was calculated according to AOAC guidelines. From the 11 remaining laboratories, 3 were excluded from statistical analysis because of invalid data determined during initial review by Youden pair, value versus laboratory. Repeatability relative standard deviation (RSDr) values ranged from 3.20 to 8.62%, and reproducibility relative standard deviation (RSDR) values ranged from 8.77 to 16.35%. With outliers excluded, RSDr values ranged from 2.94 to 5.01%, and RSDRvalues ranged from 7.50 to 13.84%. The colorimetric enzymatic method for determining neutral lactase activity in industrial enzyme preparations has been adopted first action by AOAC INTERNATIONAL.
A Validated Liquid Chromatographic Method for Determining Folates in Vegetables, Milk Powder, Liver, and Flour
Authors: Konings Erik J M
Published: February 2020

A liquid chronoat (LG) method was elaborated for determining folates in foods. Folates were extracted by homogenizing in buffer and heat treatment. A portion was incubated with an enzyme preparation containing conjugase, amylase, and protease. After purification by affinity chromatography, folate monoglutamates were determined by reversed-phase LG with fluorescence and diede array detection. Gradient elution with phosphate buffer and acetonitrile was used to separate vitamers. The most abundant folate forms naturally present in foods were detected, including tetrahy-drofolic acid, 5-methyltetrahydrofolic acid, and 5-formyltetrahydrofolic acid. 10-Formylffolic acid could be detected by applying a second fluorescence detector. Folic acid, used for fortification, might also be quantitated with this system. The difference between folate concentrations in sample extracts, with and without treatment of conjugase, is a measure of the quantity Of polyglutamates in the food matrixes. An additional treatment with conjugase, amylase, and protease reflects the arnount of matrix-bound folates. The LC system gave a linear response over the range 0–100 ng/mL. Detection limit for these compounds were 7 pg/mL for tetrahydrofolic acid and 5-methyltetrahydrofolic acid and folic acid were 1ng/ml. Repetability relative standard deviation values for separate folates in 3 candidate Certified Reference Materials (CRMs)—mixed vegetables (CRM 485), pig liver (CRM 487), and whole-meal flour (CRM 121)—and a Certified Reference Material milk powder (CRM 421) varied from 3.3 to 21.0% for the concentration range 1.8–1440 μg/100 g. Recoveries ranged from 73 to 109%. Use of amylase and protease was advantageous. Use of a comercially available folate-binding protein for cleanup saved time and money and was effective. Results for 5-methyltetrahydrofolioc acid were in good agreement with results obtained with other LC methods. Results for total folates were lower than results obtained with microbiological methods.
Multiresidue Gas Chromatographic Method for Determining Synthetic Pyrethroid Pesticides in Agricultural Products: Collaborative Study
Authors: Guo-Fang Pang , Yan-Zhong Cao , Chun-Lin Fan , Jin-Jie Zhang , Xue-Min Li ,   Collaborators:, Chu X-G , Duan W-Z , Gao X-M , Hu X-Z , Kamel A , Kubinec R , Lin A Q , Lin L-Y , Liu S-M , Papadopoulou-Mourkidou E , Mu J , Pan J W , Pardue J R , Parfitt C H , Pavoni G , Saleh M A , Shao J J , Song W B , Tahotna S , Tekel J , Tsai M-C , Wang D N , Wang K-O , Wong S S , Yu J X , Zhou Y , Zhu G-N
Published: February 2020

Fourteen laboratories from 6 countries and regions participated in an international collaborative study to evaluate a multiresidue gas chromatographic (GC) method for determining 8 synthetic pyrethroid pesticides in grains, fruits, and vegetables. The study design was based on Youden’s matched-pairs principle for collaborative tests of analytical methods. Each laboratory analyzed 12 collaborative samples of wheat, oranges, and tomatoes as blind samples. Wheat samples were extracted with acetonitrile–water (2 + 1), while orange and tomato samples were extracted with acetone. Residues were partitioned into hexane, evaporated to dryness with a rotary evaporator, and then dissolved in hexane. The hexane extract was partitioned with acetonitrile and cleaned up on a 5% water-deactivated Florisil column with 6% ethyl ether in hexane as eluant. Residue concentrations were determined by GC with electron capture detection with split-less injection by comparison with single-point calibration standards. The appropriate standard concentration was determined by screening sample extracts before analysis. The multiresidue method was tested over the concentration range of 0.0951.909 mg/kg depending on the 8 different of pesticides and agricultural products analyzed in the collaborative study. Statistical analysis of data from 13 laboratories showed weighted average recoveries for 8 pyrethroids in wheat, oranges, and tomatoes at 0.105–1.909,0.095–1.909, and 0.105–0.954 mg/kg, respectively, ranging from 91.8 to 100.2%, from 88.1 to 100.6%, and from 88.2 to 101.5%, respectively. Reproducibility relative standard deviation values ranged from 6.46 to 17.74%, from 5.94 to 18.13%, and from 5.59 to 10.48%, respectively. Repeatability relative standard deviation values ranged from 6.34 to 10.84%, from 5.19 to 11.72%, and from 3.20 to 8.09%, respectively. The multiresidue GC method for determining synthetic pyrethroid pesticides in agricultural products has been adopted first action by AOAC INTERNATIONAL.
Determination of Benzoylurea Insecticides in Apples and Pears by Solid-Phase Extraction Cleanup and Liquid Chromatography with UV Detection
Authors: Tsiropoulos Nicholas G , Aplada-Sarlis Pipina G , Miliadis George E
Published: February 2020

A liquid chromatographic (LC) method was developed and statistically validated for simultaneous determination of 5 benzoylurea insecticides (di-flubenzuron, triflumuron, teflubenzuron, flufenoxuron, and lufenuron) in apples and pears. It involves preliminary extraction with ethyl acetate–sodium sulfate and cleanup on silica solid-phase extraction cartridges using dichloromethane–2-propanol (9 + 1) as eluant. The eluate is dried under nitrogen and redissolved in methanol. Benzoylurea insecticides are determined by reversed-phase LC with gradient elution at 42°C and UV diode array detection. Recoveries from samples fortified with the 5 insecticides at 0.02–0.5 mg/kg ranged from 83 to 102% for apples and from 75 to 99% for pears. Relative standard deviations were 0–12%. Limits of detection were 0.01 mg/kg for apples and 0.02 mg/kg for pears.
Screening Nitrate in Forages with a Test Strip: Collaborative Study
Authors: Jain Anant V , Ross P Frank , Carlson Michael P ,   Collaborators:, Barger T , Barr C , Booth M , Brown W , Buckley C , Coatuey C , Colvin B , Everson R , Holt K , Kinker J , Landgraf W , Lecrone E , Medlin M , Ross S , Rumbler P , Sanchez D , Short A , Shockley M , Tahara J , Warner D , Weiband L
Published: February 2020

A collaborative study was conducted for screening nitrate in forages with a commercially available test strip. The method involves extracting a finely ground sample with deionized water. The test strip is dipped in the sample extract. The color of the reaction zone on the test strip changes from white to pink or purple depending on the nitrate concentration in sample extract. The nitrate present in the extract is determined by comparing the color of the test strip to the color scale on the test strip container. Six blind quintuplicates of forage samples were analyzed by 20 collaborators. Nitrate concentrations in forage samples tested ranged from <1000 ppm nitrate to >10 000 ppm nitrate on dry matter basis. Each collaborator was asked to assign each sample to one of the 4 following nitrate concentration ranges: (1) <1000 ppm, (2) 1000 to 5000 ppm, (3)>5000 ppm to 10 000 ppm, and (4) >10 000 ppm. Nineteen of 20 collaborators reported results. Results from 2 laboratories were rejected as outliers by inspection and χ2 test. Sensitivity rates (p+) ranged from 0.965 to 0.998, with standard errors of 0.006 to 0.16. Specificity rates (p−) ranged from 0.991 to 0.997 for the 4 ranges, with standard errors of 0.003 to 0.006. False-positive rates (pf+) ranged from 0.006 to 0.046, with standard errors of 0.006 to 0.025. False-negative rates (pf−) ranged from 0.003 to 0.007, with standard errors of 0.003 to 0.006. Screening nitrate in forages with a test strip has been adopted first action by AOAC INTERNATIONAL.
Molar Absorptivities of Aflatoxins B1, B2, G1, and G2 in Acetonitrile, Methanol, and Toluene-Acetonitrile (9 + 1) (Modification of AOAC Official Method 971.22): Collaborative Study
Authors: Nesheim Stanley , Trucksess Mary W , Page Samuel W ,   Collaborators:, Greer J , Hurley J M , Suggs F S , Wilson D M
Published: February 2020

Four laboratories participated in a mini-collaborative study of AOAC Official Method 971.22, Standards for Aflatoxins, Thin-Layer Chromatographic Method, to extend the method to 3 replacement solvents for benzene for calibration of standard afla- toxin solutions. Triplicate test sample vials, each containing 25 μg of the respective aflatoxin for each of the 4 aflatoxins and for each of the solvents, were prepared and sent to each collaborator. The collaborators dissolved the aflatoxin in each vial in 2 mL solvent, measured the UV spectrum, and reported the absorptivity maxima near 350 nm. The concentrations of the aflatoxins in the test samples were determined by dissolving identical test samples in benzene-acetonitrile (98 + 2) and following the procedure described in AOAC Official Method 971.22. These concentrations were, in turn, used to determine the molar absorptivities in the other 3 solvents (see Table 1). AOAC Official Method 971.22 has been modified to extend its applicability to 3 replacement solvents for benzene for calibration of standard aflatoxin solutions.
Laboratory Proficiency Testing of Aflatoxins in Corn and Peanuts—A Cooperative Project between Thailand and the United States
Authors: Vongbuddhapitak Amara , Trucksess Mary W , Atisook Kanoporn , Suprasert Duangchan , Horwitz William
Published: February 2020

The objective of this project was to conduct an aflatoxin proficiency test program in government, academia, and industry laboratories in Thailand. Aflatoxin-free corn and peanuts and corn and peanuts naturally contaminated with aflatoxins diluted to approximately 25 μg/kg were analyzed. Homogeneity of prepared, naturally contaminated test samples was checked on multiple replicates. The test was conducted according to the ISO/IUPAC/AOAC INTERNATIONAL Harmonized Protocol with z scores indicating laboratory performance. The participants used 3 methods: enzyme-linked immunosorbent assay, thin-layer chromatography, and the minicolumn. Of 19 laboratories that reported results for aflatoxins in naturally contaminated corn, 13 (68%) performed satisfactorily, on the basis of the mean obtained by an expert laboratory, a calculated target value for standard deviation, and the z score. Of 21 laboratories that reported results for aflatoxins in naturally contaminated peanuts, 10 (48%) performed satisfactorily. For aflatoxin-free corn, 6 laboratories reported finding aflatoxins at ≥10 ng/g, chiefly by the minicolumn method; for aflatoxin-free peanuts, 1 laboratory reported finding aflatoxins at >10 ng/g. Subsequently, a workshop of lectures and laboratory sessions was conducted to improve performance. A new and simple successive outlier removal procedure applied to the same data removed the same laboratories as did the use of z scores.