Assay of Thiamine in Foods, Using Manual and Semiautomated Fluorometric and Microbiological Methods

1977 ◽  
Vol 60 (3) ◽  
pp. 522-527
Author(s):  
Phillip W Defibaugh ◽  
Jeffrey S Smith ◽  
Cora E Weeks
Keyword(s):  
Accurate Method ◽  
Official Method ◽  
Thiamine Hydrochloride ◽  
Fluorescent Method ◽  
Microbiological Methods ◽  
The Mean ◽  
Standard Deviations ◽  
Clam Tissue ◽  
Semiautomated Method

Abstract Three methods for the determination of thiamine in foods were evaluated for accuracy, recovery, and precision: a manual fluorescent method, a semiautomated fluorescent method, and a Lactobacillus viridescens microbiological assay. Thiamine in the samples was destroyed with clam tissue thiaminase; a known amount of thiamine hydrochloride was then added to the extract; and the thiamine recovery was determined. For 14 commercially processed food products analyzed by the manual and semiautomated methods, the mean per cent recovery values and standard deviations were 91.2±8.92 and 99.3±3.13%, respectively. Eight of these products were analyzed by all 3 methods. The mean per cent recoveries and standard deviations for these 8 samples were 90.7±8.97, 101±2.52, and 99.9± 1.03%, respectively, for the manual, semiautomated, and microbiological methods. The microbiological method with L. viridescens gave the best results for the products tested. The concentration of vitamin which can be measured is such that samples of low label declaration present no problems. The semiautomated method offers a rapid and accurate method of thiamine assay. The chemical reactions are identical to those of the official method. The major difference between the methods is in the sample cleanup. It is postulated that the low recovery observed for the manual method is due to incomplete elution of thiamine in the column purification step.

Determination of Maleic Hydrazide Residues in Tobacco and Vegetables

1973 ◽  
Vol 56 (5) ◽  
pp. 1164-1172
Author(s):  
Milan Ihnat ◽  
Robert J Westerby ◽  
Israel Hoffman
Keyword(s):  
Standard Deviation ◽  
Present Method ◽  
Maleic Hydrazide ◽  
Collaborative Study ◽  
Official Method ◽  
Sample Weight ◽  
Relative Standard ◽  
The Mean ◽  
Pipe Tobacco

Abstract The distillation-spectrophotometric method of Hoffman for determining maleic hydrazide has been modified to include a double distillation and was applied to the determination of 1–30 ppm maleic hydrazide residues in tobacco and vegetables. Recoveries of 1–23 μg added maleic hydrazide were independent of weight of maleic hydrazide, but did depend on sample and sample weight. The following recoveries were obtained from 0.5 g sample: pipe tobacco, 84%; commercially dehydrated potato, 83%; cigar tobacco, 81%; dried potato, 76%; fluecured tobacco, 73%; dried carrot, 71%. In the absence of sample, the recovery was 82%. When appropriate standard curves were used, maleic hydrazide levels determined in tobacco samples were essentially independent of sample weight in the range 0.1–3 g. The mean relative standard deviation for a variety of field-treated and fortified tobacco samples containing 1–28 ppm maleic hydrazide was 3%. The precision and sensitivity of this procedure seem to be substantial improvements over official method 29.111–29.117. It is recommended that the present method be subjected to a collaborative study.

scholarly journals Solid-Phase Extraction and Gas Chromatography with Mass Spectrometric Determination of Capsaicin and Some of Its Analogues from Chili Peppers (Capsicum spp.)

1999 ◽  
Vol 82 (6) ◽  
pp. 1399-1405 ◽  
Author(s):  
Philemon Manirakiza ◽  
Adrian Covaci ◽  
Paul Schepens
Keyword(s):  
Gas Chromatography ◽  
Quantitative Determination ◽  
Solid Phase ◽  
Accurate Method ◽  
Mass Spectrometric ◽  
Phase Extraction ◽  
Capsicum Spp ◽  
The Mean ◽  
Chili Peppers

Abstract A rapid and accurate method has been developed for the quantitative determination of capsaicin and its most important analogues, dihydrocapsaicin and nordihydrocapsaicin in chili peppers. These components were extracted with methylene chlo ride and separated from interfering substances with activated charcoal. Further cleanup on Florisil cartridges and elution with ethyl acetate were performed before gas chromatographic with mass spectrometric quantitation. The concentrations found were 440 ± 64 μg/g capsaicin, 81 ± 10 μg/g dihydrocapsaicin, and 11 ± 2 μg/g nordihydrocapsaicin. The mean recovery values for triplicate analysis were between 85-94%.

Collaborative Study of the Determination of Phosphorus in Gelatin, Dessert Preparations, and Mixes

1972 ◽  
Vol 55 (3) ◽  
pp. 581-582
Author(s):  
Roger G Burkepile
Keyword(s):  
Collaborative Study ◽  
Official Method ◽  
Standard Samples ◽  
Preliminary Work ◽  
Aoac Method ◽  
Standard Deviations

Abstract A collaborative study of the proposed method for phosphorus in gelatin, dessert preparations, and mixes has been conducted. The present AOAC method for phosphorus in fertilizers, 2.023–2.025(a), was modified for this study. Preliminary work by the Associate Referee involving 4 phosphorus standard samples compared the proposed method with the official final action AOAC method for gelatin, 23.004. Additionally, phosphorus standard spikes in gelatin at the 1 and 10 mg P2O5, levels were determined by the proposed method. The proposed method is faster and more sensitive than the official method and is as accurate. Five collaborators and the Associate Referee analyzed 4 prepared samples containing various levels of phosphorus by the proposed method. The standard deviations varied from 0.005 for a 225 Bloom gelatin containing an average of 0.273% P2O5 to 0.016 for a strawberry-flavored commercial gelatin with added lecithin containing an average of 0.110% P2O5. The proposed method has been adopted as official first action to replace 23.004, which was repealed, official first action.

scholarly journals Glycemic Index and Insulinemic Index of Foods: An Interlaboratory Study Using the ISO 2010 Method

Nutrients ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 2218 ◽  
Author(s):  
Wolever ◽  
Meynier ◽  
Jenkins ◽  
Brand-Miller ◽  
Atkinson ◽  
...  
Keyword(s):  
Glycemic Index ◽  
Interlaboratory Study ◽  
Official Method ◽  
Significant Difference ◽  
Insulinemic Index ◽  
The Mean ◽  
Standard Deviations ◽  
Mean Glucose ◽  
Insulin Responses ◽  
Food Laboratory

An official method for determining food glycemic index (GI) was published by the Organization for International Standardization (ISO) in 2010, but its performance has not been assessed. Therefore, we aimed to determine the intra- and inter-laboratory variation of food GI values measured using the 2010 ISO method. Three laboratories (Australia, Canada and France) determined the GI and insulinemic-index (II) of six foods in groups of 13–15 participants using the 2010 ISO method and intra- and inter-laboratory Standard Deviations (SDs) were calculated. Overall mean food GIs varied from 47 to 86 (p < 0.0001) with no significant difference among labs (p = 0.57) and no food × laboratory interaction (p = 0.20). Within-laboratory SD was similar among foods (range, 17.8–22.5; p = 0.49) but varied among laboratories (range 17.5–23.1; p = 0.047). Between-laboratory SD of mean food GI values ranged from 1.6 to 6.7 (mean, 5.1). Mean glucose and insulin responses varied among foods (p < 0.001) with insulin (p = 0.0037), but not glucose (p = 0.054), varying significantly among labs. Mean II varied among foods (p < 0.001) but not among labs (p = 0.94). In conclusion, we found that using the 2010 ISO method, the mean between-laboratory SD of GI was 5.1. This suggests that the ISO method is sufficiently precise to distinguish a mean GI = 55 from a mean GI ≥ 70 with 97–99% probability.

AN ACCURATE METHOD FOR THE ESTIMATION OF LOW CONCENTRATIONS OF DEXTRAN IN PLASMA

1957 ◽  
Vol 35 (6) ◽  
pp. 383-390 ◽  
Author(s):  
Robert E. Semple
Keyword(s):  
Aqueous Extract ◽  
Accurate Method ◽  
Protein Precipitation ◽  
In Vitro Tests ◽  
Plasma Samples ◽  
Carbohydrate Concentration ◽  
Low Concentrations ◽  
Standard Deviations

A method is presented for the determination in plasma of small (50–150 mg./100 ml.) amounts of dextran. The procedure, which requires between 3 and 4 hours, consists of protein precipitation, glucose removal by dialysis, and the determination of the carbohydrate concentration of the resulting aqueous extract by a modified anthrone technique. Results of in vitro tests show that average dextran recovery is essentially 100% and that standard deviations in recovery range from 1.7 to 2.5% depending upon the dextran concentration. Deviations are reduced to a range of 1.4–1.7% by the use of duplicate plasma samples.

Microbiological Determination of Neomycin in Feeds: Collaborative Study

1989 ◽  
Vol 72 (2) ◽  
pp. 237-241
Author(s):  
Gerald L Stahl ◽  
D Dal Kratzer ◽  
Charles W Kasson
Keyword(s):  
Statistical Analysis ◽  
Confidence Interval ◽  
Salt Concentration ◽  
Agar Medium ◽  
Collaborative Study ◽  
Tris Buffer ◽  
Official Method ◽  
The Mean ◽  
Swine Feed

Abstract A modification of the AOAC microbiological determination of neomycin in feeds was collaboratively studied by 12 laboratories. The official method was modified by substituting a constant salt concentration diluent for the feed extract diluent, preparing the agar medium in tris buffer, and performing the test with a monolayer plating system. Each laboratory performed single assays on 8 samples in a randomized sequence. The samples included duplicates of a cattle and swine feed at 2 different marketed concentrations. The mean recovery across all laboratories was 110.7% of theory with a range of means of 69.4-128.6 across the 12 laboratories. The results of one laboratory and 2 additional values from different laboratories were deemed outliers and excluded from statistical analysis. The statistical analysis gave a confidence interval of ± 26% for individual assays.

Comparison of Semiautomated and Manual Methods for the Determination of Thiamine in Baby Cereals and Infant and Dietary Formulas

1977 ◽  
Vol 60 (3) ◽  
pp. 737-738
Author(s):  
Wallace M Ribbron ◽  
Kenneth E Stevenson ◽  
James R Kirk
Keyword(s):  
Manual Method ◽  
Standard Curve ◽  
Thiamine Content ◽  
Manual Methods ◽  
The Mean ◽  
Semiautomated Method

Abstract Using a semiautomated method, the mean thiamine content of specific products ranged from 88 to 101% and 83 to 93% for baby cereals and infant and dietary formulas, respectively, of those obtained with the AOAC manual method. The best results were obtained when data for the semiautomated method were calculated from a standard curve obtained by using thiamine solutions which had been digested and hydrolyzed along with the samples.

A New and Rapid Determination of Pyridinium Aldoximes in Blood and Urine

1969 ◽  
Vol 15 (1) ◽  
pp. 72-83 ◽  
Author(s):  
William A Groff ◽  
Robert I Ellin
Keyword(s):  
Standard Deviation ◽  
Transfer Rate ◽  
Rapid Determination ◽  
Accurate Method ◽  
Small Sample ◽  
Basic Solution ◽  
Pyridinium Oximes ◽  
Average Variation ◽  
The Mean

Abstract A rapid and accurate method for analyzing pyridinium oximes—N-methylpyridinium-2-aldoxime chloride, N,N'-trimethylene-(pyridinium-4-aldoxime) dihalide, and N,N'-oxydimethyl-(pyridinium-4-aldoxime) dichloride—in plasma, urine, and whole blood is described. The method is completely automated and requires small sample volumes. Concentrations ranging from 3 to 120 µEq./L. in biologic fluids can be determined at a rate of 40 samples per hour. This technic can be applied to oximes which are unstable in basic solution. The average variation of the oxime concentration used to establish calibration curves, as determined by the ratio of the standard deviation to the mean, was ± 1.5%. Plasma and albumin increase the transfer rate of the oximes through the dialyzing membrane. Theoretical concentrations to explain this phenomenon are presented.

Bacillus stearothermophilus Disk Assay for Determining Ampicillin Residues in Fish Muscle

1991 ◽  
Vol 74 (6) ◽  
pp. 910-912 ◽  
Author(s):  
Steven M Plakas ◽  
Angelo DePaola ◽  
Michael B Mox
Keyword(s):  
Striped Bass ◽  
Bacillus Stearothermophilus ◽  
Fish Muscle ◽  
Control Fish ◽  
Official Method ◽  
Limit Of Determination ◽  
Cultured Fish ◽  
Aoac Official ◽  
The Mean

Abstract The Bacillus stearothermophilus disk assay for penicillin in milk (AOAC official method) was adapted for the determination of ampicillin in fish muscle. The method was evaluated in 2 species of cultured fish: channel catfish and striped bass. Recoveries of ampicillin ranged from 99 to 104% when muscle specimens from both species were spiked at concentrations of 0.025-1.00 μg/g. The lower limit of determination (LOD) was 0.025 μg/g. The assay was applied to monitor the elimination of ampicillin from the muscle of striped bass after intravascular administration (dosage of 10 mg/kg body weight). The mean concentrations in the muscle declined from 1.160 μg/g at 2 h to 0.063 μg/g at 18 h. The half-life of ampicillin in the muscle was 3.6 h. Ampicillin concentrations were below LOD at 24 h. No inhibitory activity was observed in the muscle of control fish.

Gas Chromatographic/Nitrogen-Phosphorus Detection Method for Determination of Ethylene Thiourea in Finished Drinking Waters: Collaborative Study

1993 ◽  
Vol 76 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
James E Longbottom ◽  
Kenneth W Edgell ◽  
Elizabeth J Erb ◽  
Viorica Lopez-Avila ◽  
◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Drinking Water ◽  
Drinking Waters ◽  
Relative Standard ◽  
The Mean ◽  
Ethylene Thiourea ◽  
Standard Deviations ◽  
Nitrogen Phosphorus Detector ◽  
Nitrogen Phosphorus

Abstract A joint U.S. Environmental Protection Agency (USEPA)-AOAC interlaboratory method validation study was conducted on USEPA National Pesticide Survey (NPS) Method 6, "Determination of Ethylene Thiourea (ETU) in Finished Drinking Water by Gas Chromatography with a Nitrogen-Phosphorus Detector." The purpose of the study was to determine and compare the mean recoveries and precision for determination of ETU in reagent water and finished drinking waters. The study design was based on Youden's nonreplicate plan for collaborative tests of analytical methods. The waters were spiked with ETU at 6 concentrations levels, prepared as 3 Youden pairs. In the method, the test water is extracted by passing the sample through an absorbent matrix type tube. ETU is recovered from the tube with methylene chloride, the extract is solvent-exchanged to ethyl acetate, and an aliquot of each extract is analyzed by gas chromatography using a nitrogen-phosphorus detector. Twelve laboratories participated in the study. Data were analyzed using a USEPA computer program, which measured recovery and precision for ETU and compared the performance of the method between the 2 water types. Over the concentration range tested, the mean percent recoveries of ETU were 82-92% in reagent water and 85-98% in finished drinking water. The range of the betweenlaboratory relative standard deviations (RSDR) for the 6 concentrations was 5-24% in reagent water, but was only 4-9% in finished drinking water. The range of the within-laboratory relative standard deviations (RSDr) was 6-14% for reagent water and 6- 10% for finished drinking water. Results for the 2 water matrixes showed no statistically significant differences. The method has been adopted first action by AOAC International for determination of ETU in finished drinking waters.

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