Showing papers in "Journal of AOAC International in 1995"

Postcolumn derivatization liquid chromatographic method for paralytic shellfish toxins

Abstract: More than 20 analogues of saxitoxin occur naturally. An accurate analytical method applicable to all saxitoxins is required because of the recent findings that decarbamoyl toxins and C (N- sulfocarbamoyl-11-hydroxysulfate) toxins are metabolites of marine animals or major products of some dinoflagellate species. Almost all the toxins could be determined by ion-interaction chromatography on a silica-based reversed-phase (C 8 ) column with postcolumn periodate oxidation and fluorescence detection. Toxin groups of different net charges were separately determined by isocratic elution using different mobile phases. For determination of the saxitoxin group (net charge, 2+) and the gonyautoxin group (net charge, 1+), use of 1-heptanesulfonate as counterion, with or without acetonitrile in the mobile phase, resulted in resolution of decarbamoyl toxins from their carbamate analogues. C toxins having both N-sulfocarbamoyl and 11-hydroxysulfate moieties on the same molecule were completely resolved using the tetrabutylammonium ion. High sensitivity with detection limits ranging from 20 to 110 fmol were achieved as a result of reduced band broadening and optimized reaction conditions. For applications to biological matrixes, a cleanup procedure using a C 18 solid-phase extraction cartridge was effective in preventing false peaks. When applied to low-toxicity shellfish, the liquid chromatographic method gave higher values than the standard mouse bioassay, because of underestimation by the bioassay

Total dietary fiber determined as neutral sugar residues, uronic acid residues, and Klason lignin (the Uppsala method): collaborative study.

Abstract: A joint AOAC/American Association of Cereal Chemists (AACC) collaborative study was conducted to determine by the Uppsala method the dietary fiber content and its composition in various foods. The method includes preparation of a residue by treatment with thermostable alpha-amylase and amyloglucosidase and then ethanol precipitation of solubilized dietary fiber components while leaving low-molecular weight carbohydrates in solution. After acid hydrolysis of residue, neutral polysaccharide residues are determined as alditol acetates by gas-liquid chromatography, uronic acid residues are determined by colorimetry, and ash-free acid-insoluble residue (Klason lignin) is determined gravimetrically. Total dietary fiber, including enzyme-resistant starch, is calculated as the sum of nonstarch polysaccharide residues and Klason lignin. Nine laboratories completed the study, analyzing in duplicate 8 unknown dried products that included 4 cereal products, green peas, potato fiber, carrots, and apples. Total dietary fiber contents of products tested ranged from 4.6 to 84.3%, with an average RSDR value of 8.4% (range, 4.8-11.1%). Total neutral polysaccharide residues ranged from 3.8 to 64.1%, with an average RSDR value of 7.5% (range, 5.4-10.5%). Individual neutral sugars (rhamnose, arabinose, xylose, mannose, galactose, and glucose) and uronic acid residues present at more than 1% generally had good RSDR values (3.3-22.8%), whereas, as expected for Klason lignin, only the wheat bran sample with a high content (16%) had an excellent RSDR value (5.0%). The gas chromatographic-colorimetric-gravimetric method (Uppsala method) for determination of total dietary fiber (as neutral sugar residues, uronic acid residues, and Klason lignin) has been adopted first action by AOAC INTERNATIONAL.

Polymerase chain reaction-restriction fragment length polymorphism analysis: a simple method for species identification in food.

Abstract: The polymerase chain reaction (PCR) technique was applied to meat species identification in marinated and heat-treated or fermented products and to the differentiation of closely related species. DNA was isolated from meat samples by using a DNA-binding resin and was subjected to PCR analysis. Primers used were complementary to conserved areas of the vertebrate mitochondrial cytochrome b (cytb) gene and yielded a 359 base-pair (bp) fragment, including a variable 307 bp region. Restriction endonuclease analysis based on sequence data of those fragments was used for differentiation among species. Restriction fragment length polymorphisms (RFLPs) were detected when pig, cattle, wild boar, buffalo, sheep, goat, horse, chicken, and turkey amplicons were cut with AluI, RsaI, TaqI, and HinfI. Analysis of sausages indicates the applicability of this approach to food products containing meat from 3 different species. The PCR-RFLP analytical method detected pork in heated meat mixtures with beef at levels below 1%, and the method was confirmed with porcine- and bovine-specific PCR assays by amplifying fragments of their growth hormone genes. Inter- and intraspecific differences of more than 22 animal species with nearly unknown cytb DNA sequences, including hoofed mammals (ungulates), and poultry were determined with PCR-RFLP typing by using 20 different endonucleases. This typing method allowed the discrimination of game meats, including stag, roe deer, chamois, moose, reindeer, kangaroo, springbok, and other antelopes in marinated and heat-treated products.

FDA Total Diet Study, July 1986-April 1991, dietary intakes of pesticides, selected elements, and other chemicals.

Abstract: The U.S. Food and Drug Administration conducts the Total Diet Study to determine dietary intakes of selected pesticides, industrial chemicals, and elements (including radionuclides). This paper reports results for the sampling period July 1986 to April 1991. The study involves retail purchase of foods representative of the ?total diet? of the U.S. population, preparation for ?table-ready? consumption, and individual analyses of 234 items making up the diets of 8 population groups. The diets were based on 2 nationwide food consumption surveys. The data presented represent 21 food collections (also termed ?market baskets?) in regional metropolitan areas during the 5-year period. Dietary intakes of nearly 120 analytes are presented for 8 population groups, which range from infants to elderly adults. Intakes of selected population groups are compared with representative findings from earlier Total Diet Study sampling periods. As reported previously, average daily intakes are well below acceptable limits.

Detection of sodium channel toxins: directed cytotoxicity assays of purified ciguatoxins, brevetoxins, saxitoxins, and seafood extracts.

Abstract: Neuroblastoma cells in culture were used to detect sodium channel-specific marine toxins based on an end-point determination of mitochondrial dehydrogenase activity. The assay responds in a dose-dependent manner to ciguatoxins, brevetoxins, and saxitoxins, and delineates the toxic activity as either sodium channel enhancing or sodium channel blocking. The assay responds rapidly to sodium channel activating toxins, allowing dose dependent detection in 4 to 6 h. Brevetoxins can be detected at 250 pg, and purified ciguatoxins are detected in the low picogram and subpicogram levels. The results obtained from cell bioassay of ciguatoxic finfish extracts correlates with those obtained from mouse bioassays. Sodium channel blocking toxins can also be detected with an approximate sensitivity of 20 pg in 24 to 48 h. This cell-based technique is simple, sensitive, demonstrates potential as an alternative to animal testing for sodium channel activating and blocking toxins, and can be automated.

Rapid Extraction and Cleanup for Liquid Chromatographic Determination of Domoic Acid in Unsalted Seafood

Abstract: Domoic acid is the toxin responsible for incidents of amnesic shellfish poisoning. A rapid extraction and cleanup for the liquid chromatographic determination of domoic acid in unsalted seafood is reported. The method uses a single-step extraction with 50% aqueous methanol and a selective cleanup and preconcentration with strong-anion exchange, solid-phase extraction. Determination is performed by liquid chromatography with ultraviolet absorbance detection. The detection limit was 20-30 ng/g. Recoveries of 93% were achieved from 0.2 to 20 μg/g in mussel tissues. The method gave a precision of less than 3% for concentrations greater than 2 μg/g and less than 6% at 0.2 μg/g. A linear dynamic range of 104 can be achieved. The method was successfully applied to a variety of seafood products, including mussels, razor clams, crabs, and anchovies

Determination of pH of soils by different methods : collaborative study

Abstract: Fifty-three laboratories (including author's) from Canada, India, Israel, and the United States participated in a collaborative study for the measurement of pH of different types of soils. A method with 2 alternative procedures was used for pH measurements of mineral soils (alternative I for soils containing less than 17× organic carbon and alternative II for soils with variable salt content), a second method was used for saline-sodic soils, and a third method was used for organic soils (soils containing at least 17× organic carbon). The pH was measured potentiometrically. The methods were selected by the Soil Science Society of America, S889 Committee on Coordination of Official Methods of Soil Analysis. Each laboratory used all 4 procedures to analyze 10 blind duplicate samples per procedure. The repeatability relative standard deviation values (RSD,) were 1.45-7.80% for mineral soils tested by the alternative 1, 0.95-6.91% for mineral soils tested by the alternative 11, 0.74-7.09% for saline-sodic soils, and 0.73-4.66% for organic soils. The corresponding reproducibility relative standaad deviation (RSDR) values were 2.67-10.75%, 2.03-7.54%, 2.45-9.93%, and 2.15-6.32%. Repeatability and reproducibility data indicated that the results are within acceptable levels. The 3 methods for pH measurements of mineral, saline-sodic, and organic soils were adopted first action by AOAC INTERNATIONAL

Survey of lead, cadmium, fluoride, nickel, and cobalt in food composites and estimation of dietary intakes of these elements by Canadians in 1986-1988.

Abstract: During the period 1986-1988, foods were purchased at the retail level in 5 Canadian cities and, for each city, prepared for consumption and combined into 113 composites and 39 composite subsets. Lead and cadmium were determined in all the samples; fluoride, in samples from Winnipeg; and cobalt and nickel, in samples from Montreal. Means and ranges of concentrations (ng/g) found in individual samples were lead, 23.2 (< 0.4-523); cadmium, 9.96 (< 0.02-167); fluoride, 325 (11-4970); nickel, 196 (< 0.6-2521); and cobalt, 9.4 (< 0.3-75.7). Estimated dietary intakes (microgram/day) of the elements over all ages and sexes were lead, 24; cadmium, 13; fluoride, 1763; nickel, 286; and cobalt, 11. During the period 1985-1988, the average level of lead in canned foods decreased from 73.6 to 46 ng/g.

Multiresidue determination of pesticides in fruit and vegetables by gas chromatography-mass-selective detection and liquid chromatography with fluorescence detection

Abstract: A method is described for determining 199 pesticides in fruit and vegetables. Residues are extracted from samples with acetonitrile, and coextractives are removed with a miniaturized charcoal-Celite column cleanup. Analysis is performed by gas chromatography with mass-selective detection in selective-ion monitoring mode. Two injections per sample are required to cover all compounds. Positive analytes are confirmed by retention time and ion ratios. Carbamates are analyzed by liquid chromatography with postcolumn reaction and fluorescence detection. Recovery data were obtained by fortifying 3 matrixes (pears, carrots, and bananas) at 0.1-0.5 ppm. In addition, the method demonstrated acceptable performance for analysis of other crops such as apple, strawberry, orange, pineapple, asparagus, beet, cucumber, tomato, pepper, squash, green peas, potato, and sweet potato. Limits of detection ranged from 0.02 to 0.2 ppm depending on the compound.

Dietary intakes of pesticides, selected elements, and other chemicals: FDA Total Diet Study, June 1984-April 1986.

Abstract: The U.S. Food and Drug Administration conducts the Total Diet Study to determine dietary intakes of selected pesticides, industrial chemicals, and elements (including radionuclides). The results reported here reflect the sampling period from June 1984 to April 1986. The study involves retail purchase of foods representative of the total diet of the U.S. population, preparation for table-ready consumption, and individual analyses of 234 items depicting the diets of 8 population groups. The diets were based on 2 nationwide food consumption surveys. The data presented represent 8 food collections (also termed "market baskets") in regional metropolitan areas during the 2-year period. Dietary intakes of over 90 analytes are presented for the 8 population groups, which range from infants to elderly adults. Intakes of selected population groups are compared with representative previous findings. As reported previously, average daily intakes are well below acceptable limits.

Validation of an Analytical Instrumental Method by Standard Addition Methodology

Abstract: A statistical procedure to validate an analytical methodology by standard addition methodology is described. The data set obtained in 3 calibration experiments with standard solutions, standard additions, and portions of sample is used. The accuracy of the analytical results is checked by comparison of analyte contents in the different calibrations and from the recovery. Mathematical expressions to estimate the statistical parameters are proposed. The statistical protocol has been applied to fluorimetric determination of molybdenum with alizarin S in vegetable tissues

Development of a method of analysis for 46 pesticides in fruits and vegetables by supercritical fluid extraction and gas chromatography/ion trap mass spectrometry

Abstract: A multiresidue method using supercritical fluid extraction (SFE) and gas chromatography/ion trap mass spectrometry (GC/ITMS) was developed for analysis of 46 pesticides in fruits and vegetables. The SFE procedure used 2 commercial instruments that trapped the extracts on solid-phase material. Silica gel chemically bound to octadecylsilane (ODS) collected the extracted pesticides efficiently, and elution of the trap with acetonitrile gave high recoveries. Extracts thus obtained were sufficiently clean for subsequent GC/ITMS analysis. The SFE conditions were 320 atm and 60 degrees C (0.85 g/mL CO2 density) and 1.6 mL/min CO2 flow rate for 6 extraction vessel volumes. Trapping on 1 mL ODS occurred at 10 degrees C, and a 0.4 mL/min flow rate of acetonitrile at 40 degrees-50 degrees C was used to elute the pesticides. Quantitative and qualitative analyses of the 46 pesticides were performed simultaneously by GC/ITMS. Studies of fortified samples gave > 80% recoveries for 39 pesticides, and recoveries of > 50% for the other pesticides, except methamidophos and omethoate. Grapes, carrots, potatoes, and broccoli were used as samples during method development, and a blind experiment involving incurred and fortified samples was used to test the approach. Results of the blind study compared satisfactorily with results from 7 laboratories using traditional GC detectors and solvent-based extractions.

Analysis of diarrhetic shellfish poisoning toxins in shellfish tissue by liquid chromatography with fluorometric and mass spectrometric detection.

Abstract: Diarrhetic shellfish poisoning (DSP) is a severe gastrointestinal illness caused by consumption of shellfish contaminated with toxigenic dinoflagellates. The main toxins responsible for DSP are okadaic acid (OA), DTX-1, DTX-2, and DTX-3, the latter being a complex mixture of 7-O-acyl derivatives of the first 3. In this study, existing methods based on liquid chromatography (LC) combined with mass spectrometry (LC-MS) and LC with fluorometric detection (LC-FLD) of anthryldiazomethane (ADAM) derivatives were improved upon to achieve a high degree of accuracy and precision for the determination of DSP toxins in a new mussel tissue reference material (MUS-2). All experimental parameters were examined comprehensively, and a new internal standard and a new solid-phase extraction cleanup method were introduced. Quantitative extraction of DSP toxins from shellfish tissue was achieved by exhaustive extraction with aqueous 80% methanol. Cleanup was accomplished by partitioning the crude aqueous methanol extract with hexane to remove lipids and then with chloroform to isolate the toxins. A further cleanup based on an aminopropylsilica column was useful for LC-MS and looks promising for the ADAM/LC-FLD method. The internal standard, 7-O-acetylokadaic acid, synthesized by partial acetylation of OA, improved accuracy and precision by correcting for incomplete recoveries in extraction, cleanup, and derivatization steps and for volumetric errors and instrumental drift. An improved silica cleanup after ADAM derivatization also was developed by controlling the activities of both sorbent and solvents. The methods were tested with various mussel tissue samples. The resulting improved methods will be useful to analysts involved in routine monitoring of DSP toxins.

Determination of amino acids in food and feed by derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and reversed-phase liquid chromatographic separation

Abstract: A study of a new amino acid analysis method using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate as a precolumn derivatization reagent for the analysis of food and feed is described. All amino acids, including methionine sulfone and cysteic acid, were well separated on a liquid chromatographic system using the optimized chromatographic conditions. Salts in food and feed interfered very slightly with the derivatization yields of all amino acids. Several typical agricultural products and animal feeds, including 2 AOAC test samples, were analyzed with the method. The results agreed well with the data generated by using the classical post-column method with ion-exchange chromatography. The average relative standard deviations for corn and broiler starter feed were 0.74 and 0.70%, respectively. Good recoveries of all amino acids were demonstrated (average, 101 %), even for a sample with a very complex matrix.

Market basket and duplicate portion estimation of dietary intakes of cadmium, mercury, arsenic, copper, manganese, and zinc by Japanese adults.

Abstract: Daily intakes of selected metals from meals in Shiga Prefecture (Japan) were investigated by the duplicate portion method and market basket method. In 1991 and 1992, daily intakes of metals by women, determined by the duplicate portion method, were, respectively, 37 and 27 micrograms for Cd, 4.3 and 3.5 micrograms for Hg, 260 and 210 micrograms for As, 1200 and 1200 micrograms for Cu, 4700 and 3600 micrograms for Mn, and 8000 and 7200 micrograms for Zn. Those determined by the market basket method were, respectively, 32 and 35 micrograms for Cd, 4.3 and 9.9 micrograms for Hg, 160 and 280 micrograms for As, 1100 and 980 micrograms for Cu, 3600 and 4700 micrograms for Mn, and 8700 and 8500 micrograms for Zn. No wide differences between the 2 methods were found, except for Hg data in 1992. Daily intakes of Cd and Hg in Shiga Prefecture were lower than the provisional tolerable daily intakes of 57-72 micrograms for Cd and 43 micrograms for Hg, proposed by the Food and Agricultural Organization and the World Health Organization.

Evaluation of Prechromatographic Oxidation for Liquid Chromatographic Determination of Paralytic Shellfish Poisons in Shellfish

Abstract: 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 N-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 (090) 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%

Rapid and simple method for determination of cholesterol in processed food

Abstract: An improved method for determination of cholesterol in processed food with only one extraction and without solvent removal was developed. Total time to analyze a sample including gas chromatographic (GC) analysis is 45 min. Food samples spiked with internal standard are hydrolyzed in a screw-capped vial with saturated methanolic KOH. Cyclohexane is added to the mixture, and the upper layer is analyzed by GC on a capillary column. Average recoveries of spiked white eggs are 99 +/- 0.5%. Fifteen types of processed food containing shrimp, fish, meat, cheese, eggs, and vegetables were analyzed with this method and with the AOAC method.

Liquid chromatographic method for determination of biogenic amines in fish and fish products.

Abstract: A liquid chromatographic method with postcolumn derivatization is described for determination of biogenic amines in fish and fish products. Histamine, tyramine, serotonin, beta-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 micron 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 < or = 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.

Determinations of marine toxins in foods.

Abstract: Prospects of new analytical methods for determining marine toxins in foods are described. The methods discussed include fluorometric liquid chromatography, cytotoxicity assays, channel binding assays, and enzyme-immunoassays. Emphasis was laid on assay methods for ciguatoxins and diarrhetric shellfish toxins

Determination of fat, protein, and total solids in cheese by near-infrared reflectance spectroscopy.

Abstract: Near-infrared reflectance (NIR) spectroscopy was used to analyze fat, protein, and total solids in cheese without any sample treatment. A set of 92 samples of cow's milk cheese was used for instrument calibration by principal components analysis and modified partial least-square regression. The following statistical values were obtained: standard error of calibration (SEC) = 0.388 and squared correlation coefficient (R2) = 0.99 for fat, SEC = 0.397 and R2 = 0.98 for protein, and SEC = 0.412 and R2 = 0.99 for total solids. To validate the calibration, an independent set of 25 cheese samples of the same type was used. Standard errors of validation were 0.47, 0.50, and 0.61 for fat, protein, and total solids, respectively, and R2 for the regression of measurements by reference methods versus measurements by NIR spectroscopy was 0.98 for the 3 components.

Evaluation of a liquid chromatographic method for the determination of fumonisins in corn, poultry feed, and Fusarium culture material.

Abstract: The performance of a liquid chromatographic method for determining fumonisins in corn, animal feeds, and culture material was evaluated. Efficiencies of extractions with the following solvent systems were determined : acetonitrile-water (50 + 50, v/v), methanol-water (75 + 25, v/v), and 100% water. The acetonitrile solvent gave both higher extraction efficiencies and faster extraction times than the other 2 solvents. Extraction was followed by C 18 solid-phase extraction column cleanup. Fumonisin B 1 (FB 1 ), fumonisin B 2 (FB 2 ), and fumonisin B 3 (FB 3 ) were measured by precolumn derivatization with o-phthalaldehyde followed by isocratic separation on a C 18 reversed-phase column with a mobile phase of 50 mM potassium dihydrogen phosphate (pH 3.3)-acetonitrile (60 + 40). Commercially prepared poultry feed, corn, and Fusarium spp. corn cultures were analyzed at the following levels : FB 1 , 1.5 to 15 000 μg/g ; FB 2 , 0.5 to 4000 μg/g ; FB 3 , and 0.17 to 1 500 μg/g. Recoveries were 91-94%, 90-100%, and 81-93% for FB 1 , FB 2 , and FB 3 , respectively. Precision (coefficient of variation) was determined with pooled field samples and ranged from 2% at 19 μg/g for FB 1 to 9% at 0.17 μg/g for FB 3 . Time and pH studies of the formation of the fluorescent derivative and its stability were conducted. Complete reaction occurred at pHs above 7.9, with optimal pH for chromatography between 8.0 and 8.5. No statistically significant response differences were detected for reaction times ranging from 4 to 40 min ; however, the detector signal was significantly reduced when reaction times were shorter than 4 min. Chromatograms of samples were free of interferences for all feeds, corn, and culture material tested. Quantitation limits for the 3 fumonisins were of the same magnitude and were estimated to be 0.1 μg/g for FB 1 and 0.2 μg/g for FB 2 and FB 3 .

Survey of deoxynivalenol in U.S. 1993 wheat and barley crops by enzyme-linked immunosorbent assay.

Abstract: Wheat and barley from the 1993 crop year were analyzed for deoxynivalenol (DON). A total of 630 samples were collected by the Federal Grain Inspection Service in 25 states and analyzed using a commercially available, direct competitive, enzyme-linked immunosorbent assay. The limit of determination was about 0.5 micrograms/g. DON contamination in the 483 wheat samples averaged 2.0 micrograms/g and ranged from < 0.5 to 18 micrograms/g. DON contamination in the 147 barley samples averaged 4.2 micrograms/g and ranged from < 0.5 to 26 micrograms/g. About 40% fo the wheat samples and 57% of the barley samples contained DON levels that were greater than the U.S. Food and Drug Administration 1982 advisory level of 2 micrograms/g for DON in wheat designated for milling (human consumption).

International survey on dietary fiber: definition, analysis, and reference materials.

Abstract: An international survey was conducted to get the views of 147 professionals in the field on the definition of dietary fiber. The survey also solicited opinions on analytical methods for nutrition labeling, quality control, and nutrition research. The survey finds that dietary fiber is generally defined as polysaccharides and lignin that are not hydrolyzed by human alimentary enzymes. Support is strong for expansion of the definition to include oligosaccharides that are resistant to hydrolysis by human alimentary enzymes. Among techniques for nutrition labeling and quality control, enzymatic-gravimetric methods get the highest support. For nutrition research, more detailed methods such as gas-liquid chromatography and liquid chromatography were considered more appropriate. Respondents support labeling of total, soluble, and insoluble dietary fiber or total dietary fiber alone as sufficient for nutrition labeling of food packages. However, for nutrition research, detailed analytical methods, improvements in accuracy (i.e., closer simulation of in vitro techniques to conditions of human gastrointestinal tract), and improvements in precision and simplicity are suggested. Less than 20% of the participants use reference materials for dietary fiber analysis.

Liquid chromatographic determination of trans-10-hydroxy-2-decenoic acid content of commercial products containing royal jelly.

Abstract: Thirty-nine samples of commercial products containing royal jelly were analyzed by liquid chromatography for their trans-10-hydroxy-2-decenoic acid (10-HDA) content. Most of the samples contained 10-HDA. Samples claimed to be pure royal jelly contained 1.98 to 6.37% 10-HDA (w/w). The 10-HDA content of samples claimed to contain royal jelly as an ingredient ranged from nondetectable to 1.28% (w/w).

Isolation, purification, and liquid chromatographic determination of stilbene phytoalexins in peanuts

Abstract: A liquid chromatographic (LC) method for determination of stilbene phytoalexins (SPs) in peanuts has been developed. SPs were extracted with acetonitrile-water (90 + 10, v/v) by high-speed blending. An aliquot of extract was applied to a minicolumn packed with Al 2 O 3 -ODS (C 18 ) mixture and eluted with acetonitrile-water (90 + 10, v/v). Eluate was evaporated under nitrogen, and residue was dissolved in LC mobile phase. SPs in an aliquot of purified extract were quantitated by normal-phase partition LC on silica gel with n-heptane-2-propanol-water-acetonitrile-acetic acid (1050 + 270 + 17 + 5 + 1, v/v) as mobile phase. Recoveries of SPs [trans-4-(3-methyl-but-1-enyl)-3,5,4'-trihydroxystilbene (trans-arachidin-3 ; t-Ar-3), trans-3-isopentadienyl-4,3',5'-trihydroxystilbene (t-IPD), and trans-3,5,4'-trihydroxystilbene (trans-resveratrol; t-Res)] from peanuts spiked at 300 ppb were 96.05 ± 2.8%. Limits of quantitation for t-Ar-3 and t-IPD were about 100 ppb. t-Ar-3, t-IPD, and t-Res were found in all parts of the peanut plant as major SPs produced in response to fungal invasion.

Daily intakes of tributyltin and triphenyltin compounds from meals.

Abstract: Daily intakes of tributyltin (TBT) and triphenyltin (TPT) compounds from meals in Shiga Prefecture, Japan, were investigated by 2 methods. Daily intakes of TBT and TPT by the duplicate portion method were, respectively, 4.7 and 0.7 microgram in 1991 and 2.2 and 0.7 microgram in 1992. Those by the market basket method were, respectively, 6.9 and 5.4 micrograms in 1991 and 6.7 and 1.3 micrograms in 1992. Daily intakes of TBT and TPT by the market basket method were higher than those by the duplicate portion method. These values were considerably lower than acceptable daily intakes of 80 micrograms/50 kg body weight specified by the Welfare Ministry of Japan for bis(tri-n-butyltin)oxide and of 25 micrograms/50 kg body weight specified by the Food and Agriculture Organization/World Health Organization for TPT.

Determination of tetracycline residues in bovine milk, serum, and urine by capillary electrophoresis.

Abstract: A method was developed for simultaneous determination of oxytetracycline (OTC), chlortetracycline, tetracycline, and doxycycline levels in cow milk, serum, and urine by capillary electrophoresis (CE). The tetracyclines (TCs) were extracted specifically with a metal-chelating affinity column. Extracts were then applied to C18 cartridges treated with dimethyldichlorosilane, and the TCs were eluted with ethanol. Salt-free sample residues were run on CE with a diode array detector at 370 nm. A 50 cm x 75 micron uncoated capillary at 15 kV and 23 degrees C was used to separate the TCs. The run buffer contained 10 mM sodium dodecyl sulfate, 50 mM borate, and 50 mM phosphate, pH 8.5. TC peaks were identified by migration times, coinjection of standards, and diode array spectra. Limits of detection for TCs were 1.3-5.6 ng/mL, and limits of quantitation were 1.7-8.7 ng/mL in cow fluid samples. OTC appeared consistently at 13.3-13.4 min in milk, serum, and urine samples from a cow treated with OTC. OTC was further identified by coinjection of OTC standard and OTC diode array spectra. The CE method can be used to simultaneously determine 4 TC residues at low parts-per-billion levels.

Determination of malachite green and its metabolite, leucomalachite green, in catfish (Ictalurus punctatus) tissue by liquid chromatography with visible detection.

Abstract: To determine residues of malachite green (MG) and its metabolite, leucomalachite green (LMG), in catfish tissue, analytes are extracted with acetonitrile- buffer and the extract is partitioned into methylene chloride. Final cleanup and isolation are performed on neutral alumina solid-phase extraction (SPE) and propylsulfonic acid cation-exchange SPE columns before analysis by liquid chromatography with visible detection. PbO 2 postcolumn oxidation is performed by isocratic elution with a buffered mobile phase from a cyano column. Recoveries and relative standard deviations (RSDs) from fortified catfish tissues were 72.9% (RSD, 1.92%; 23 ppb), 75.5% (RSD, 6.85%; 11 ppb), and 69.6% (RSD, 6.93%; 5.7 ppb) for MG and 87.4% (RSD, 2.92%; 21 ppb), 88.1% (RSD, 5.94%; 10 ppb), and 82.6% (RSD, 11.5%; 5.3 ppb) for LMG. The method was applied to MG-incurred catfish at depuration times of 0, 2, 4, 8, and 24 h. Average levels of residual MG and LMG in the 24 h depuration catfish tissue were 73.4 and 289 ppb, respectively

Automated Sample Preparation for Monitoring Groundwater Pollution by Carbamate Insecticides and Their Transformation Products

Abstract: We investigated automated on-line solid-phase extraction (SPE) followed by liquid chromatographic (LC) techniques for monitoring carbamates and their transformation products. Analytical determinations were performed by LC with UV or postcolumn fluorescence detection (U.S. Environmental Protection Agency Method 531.1 for carbamate insecticides) after preconcentration with on-line SPE using C18 Empore extraction disks. On-line SPE/LC/thermospray mass spectrometry with time-scheduled selected-ion monitoring was used as confirmatory method. The method was used to determine pesticide traces in well waters of a typical aquifer in the Almeria area (Andalucia, south of Spain) from March 1993 to February 1994. The major pollutants, found in highest amounts, were carbofuran, methiocarb, and methomyl, at levels of 0.32, 0.3, and 0.8 micrograms/L, respectively. According to results of seasonal variation studies, pollution by carbamate insecticides is sporadic and exceeds the limit of 0.5 micrograms/L for total pesticides allowed by the European Economic Community Drinking Water Directive only twice a year. 3-Hydroxycarbofuran and methiocarb sulfone also were detected, showing the importance of including the main toxic break-down products of carbamate insecticides in future monitoring programs.

Immunoassay of pesticides: an update

Abstract: Measurement of levels of pesticides residues in foods and crops most often requires extensive cleanup and instrumental techniques such as gas chromatography. Immunoassay measurement techniques, on the other hand, may be used directly on the test portion or require only minimal cleanup. Further refinements of the common antibody-enzyme-based solid-phase assays, such as use of coated magnetic particles, antibody-coated crystals, and continuous-flow devices, have extended the measurement range and applicability of these assays. Likewise, new immunoassays for pesticides have been developed, and existing assays have been refined, optimized, and more completely characterized and validated. In addition to their ability to accurately and reliably measure amounts of residues present in food and crops, immunoassays can be readily used as rapid screening methods for contaminants in field samples. We have previously reviewed much of the work in the area of pesticide immunoassay; this report updates previous information and discusses some new immunoassay techniques.