Collaborative Study of a Rapid Method for Determining Aflatoxins in Cottonseed Products

1975 ◽  
Vol 58 (4) ◽  
pp. 746-753
Author(s):  
Walter A Pons
Keyword(s):  
Systematic Error ◽  
False Positive ◽  
Collaborative Study ◽  
Statistical Treatment ◽  
Official Method ◽  
Modified Method ◽  
Collaborative Studies ◽  
Coefficients Of Variation ◽  
Aoac Method ◽  
The Mean

Abstract Eleven laboratories collaboratively studied a modification of the official final action AOAC method, 26.048–26.056, for determining aflatoxins in cottonseed products. An aflatoxinnegative meal, 6 contaminated meals, 4 contaminated meats (kernels) samples, and 2 ammonia-inactivated meals were used. Mean a (latoxin values, μg/kg, ranged from 6 to 223 (B1), 2 to 44 (B2), and 7 to 266 (total: B1 + B2). Only one laboratory reported a false-positive for the negative meal. The mean coefficients of variation for B1, B2, and total were 28, 56, and 29%, respectively, for meals; 35, 54, and 37%, respectively, for meats; and 35, 58, and 38%, respectively, for ammoniated meals. Statistical treatment of data from triplicate sets of meals and meats showed evidence for systematic error between laboratories. Since the modified method is considerably faster than the official method and yields precision estimates consistent with previous AOAC collaborative studies on determining aflatoxins, the method has been adopted as official first action.

Quantitative Determination of 1-131, Cs-137, and Ba-140 in Milk: Collaborative Studies

1982 ◽  
Vol 65 (5) ◽  
pp. 1039-1043
Author(s):  
Frederick G D Shuman ◽  
David G Easterly ◽  
Edmond J Baratta
Keyword(s):  
High Activity ◽  
Gamma Ray ◽  
Collaborative Study ◽  
Official Method ◽  
Collaborative Studies ◽  
Coefficients Of Variation ◽  
The Mean ◽  
Method Bias ◽  
Low Activity

Abstract The official method for Cs-137 in milk by gamma-ray spectroscopy was extended to include 1-131 and Ba- 140. A collaborative study was performed on this method applied to 1-131 concentration in cow's milk; the original collaborative study of the method including all 3 nuclides was reviewed. In the 1-131 study, 1 aliquot of a milk sample containing 82 pCi/L was sent to each of 60 laboratories for triplicate analyses. From 40 responses, the mean of the reported values was 81.6 pCi/L, indicating a method bias below the 5% statistical detectability limit. Within- and between-laboratory coefficients of variation (CVs) were 7 and 8%, respectively. In the 3-nuclide study, 2 samples were sent to 25 laboratories for triplicate analyses; one sample contained 633,305, and 515 pCi/L, respectively, of 1-131, Cs-137, and Ba-140 and the other contained 98,52, and 72 pCi/L. For the high-activity sample, within-laboratory CVs were 4-5% for the 3 nuclides and between-laboratory CVs were 4-7%. For the low-activity sample, the corresponding results were 6-9% and 8-16%. The method bias was statistically significant at 95% confidence only for Cs-137 in the high-activity sample; reported results were 3% below the known concentration. The extended method was adopted official first action.

Collaborative Study of Rapid Fat Determination in Meat and Meat Products by Modification of the AOAC Method

1973 ◽  
Vol 56 (5) ◽  
pp. 1140-1143 ◽  
Author(s):  
Julio D Pettinati ◽  
Clifton E Swift ◽  
Edward H Cohen
Keyword(s):  
Standard Deviation ◽  
Collaborative Study ◽  
Meat Product ◽  
Statistical Treatment ◽  
Meat Products ◽  
Complete Removal ◽  
Official Method ◽  
Pork Sausage ◽  
Modified Method ◽  
Aoac Method

Abstract The rapid method for fat determination reported by this laboratory has been evaluated by 10 collaborating laboratories in a comparison with the AOAC method. The method is similar to the official method except that a 3–4 g sample of meat or meat product is dried in an open extraction thimble for 30 min at 125°C and extracted with ethyl ether for 45 min at maximum reflux, and fat content is determined gravimetrically after complete removal of solvent from the extract. Collaborators performed 6 replicate analyses on samples of ground beef, frankfurters, and fresh pork sausage by both methods. A statistical treatment of the results showed that fat contents determined by the modified method agreed with those obtained by the official method. The expected standard deviation, se, averaged for the 3 types of meat product, was ±0.83% fat which is 1.5 times the value obtained by the official method, ±0.56% fat.

Collaborative Study of Improvements in the Distillation Procedure of the Official Method for Formaldehyde in Maple Sirup

1973 ◽  
Vol 56 (1) ◽  
pp. 132-134
Author(s):  
Calixte Hébert
Keyword(s):  
Collaborative Study ◽  
Official Method ◽  
Distillation Method ◽  
Modified Method ◽  
Quantitative Extraction ◽  
Coefficients Of Variation ◽  
Excellent Control ◽  
Final Operation

Abstract A collaborative study was conducted to show that in the quantitative extraction of formaldehyde from maple sirup by the official final action controlled distillation method, 31.184—31.189, accuracy is increased by the use of a thermostatically controlled flask heater, together with the proper insulation of the glass apparatus with asbestos cord. This eliminates undue condensation of the distillate and variations in the final and total distillation times. The modified method was tested by 9 laboratories and, from their individual results, the coefficients of variation for the total time of distillation proved that the method gave excellent control of the final operation. The changes have been adopted as official first action.

Modified Extraction Procedure for Ipronidazole in Feeds Containing Bentonite

1974 ◽  
Vol 57 (1) ◽  
pp. 29-31
Author(s):  
Modest Osadca ◽  
Mercedes Araujo ◽  
Elmer De Ritter
Keyword(s):  
Collaborative Study ◽  
Extraction Procedure ◽  
Gas Liquid Chromatography ◽  
Buffer Gas ◽  
Modified Method ◽  
Quantitative Extraction ◽  
Collaborative Test ◽  
Coefficients Of Variation ◽  
Aoac Method ◽  
Benzene Extract

Abstract The extraction procedure in the AOAC method for ipronidazole in feeds, 38.A01— 38.A07, has been modified to eliminate the interference of bentonite with recovery of ipronidazole from mash feed and pellets. Quantitative extraction from mash feed or ground pellets is achieved by shaking the sample with benzene after a brief soaking with warm, aqueous pH 8 buffer. Gas-liquid chromatography is used to measure ipronidazole in the benzene extract as in the AOAC method. A preliminary collaborative test of the modified method by 3 laboratories on 8 samples of feed containing 0, 2, or 5% bentonite yielded average assays of 0.0061, 0.0058, and 0.0062% ipronidazole, with coefficients of variation averaging 2.4, 6.2, and 4.4%, respectively. Further collaborative study of the modified method is recommended.

Collaborative Study of Modified AOAC Method of Analysis for Nitrite in Meat and Meat Products

1977 ◽  
Vol 60 (3) ◽  
pp. 594-599 ◽  
Author(s):  
Rosemary Nicholas Fiddler
Keyword(s):  
Random Error ◽  
Collaborative Study ◽  
Meat Products ◽  
Matched Pair ◽  
Official Method ◽  
Griess Reagent ◽  
Standard Curve ◽  
Modified Method ◽  
Color Development ◽  
Aoac Method

Abstract A modified version of the AOAC method of analysis for nitrite in meat and meat products was tested collaboratively by 23 laboratories. Results were compared with those obtained by the official AOAC method. Recommended modifications include: (a) substitution of N-(1-naphthyl) ethylenediamine and sulfanilamide for Griess reagent, (b) separate addition and 1:10 dilution of the above reagents, (c) 20 min color development and absorbance read at 540 nm, (d) substitution of NaNO2 for AgNO2 and NaCl, (e) omission of mercuric chloride, (f) screening of filter paper for nitrite contamination, (g) more precise dilution of sample aliquot, and (h) standard curve linear up to 10 μg N/50 ml. Results were statistically treated by Youden’s technique for comparing 2 methods, using a matched pair sample scheme. The random error for the modified method was significantly lower than the random error for the official method. A t-test showed no difference in bias between the 2 methods.

Collaborative Study of an Improved Method for the Isolation of Filth from Starches

1972 ◽  
Vol 55 (1) ◽  
pp. 62-63
Author(s):  
John S Gecan ◽  
Paris M Brickey
Keyword(s):  
Acid Hydrolysis ◽  
Collaborative Study ◽  
Official Method ◽  
Improved Method ◽  
Modified Method ◽  
Aoac Method ◽  
Wet Sieving

Abstract The official AOAC method for filth in starches, 40.056, has been modified to obtain better recovery of extraneous materials. In lieu of wet sieving on a No. 140 sieve, the modified method utilizes No. 230 wet sieving followed by an acid hydrolysis, if excessive starch material remains on the sieve. A limited collaborative study comparing the improved method with the official method resulted in higher recoveries of rodent hairs and equivalent recoveries of other spike elements by the improved method. The improved method is recommended for adoption as official first action to replace 40.056.

Collaborative Study of the Quantitative Gas-Liquid Chromatographic Determination of Fusel Oil and Other Components in Whisky

1972 ◽  
Vol 55 (3) ◽  
pp. 549-556
Author(s):  
J H Kahn ◽  
E T Blessinger
Keyword(s):  
Ethyl Acetate ◽  
Collaborative Study ◽  
Chromatographic Determination ◽  
Official Method ◽  
Fusel Oil ◽  
Fusel Alcohols ◽  
Aoac Method ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract Fifteen chemists participated in a collaborative study for the quantitative pas-liquid chromatographic determination of the individual fusel alcohols and ethyl acetate in whisky. Two levels of congeners represented by 4 coded samples of whisky were analyzed by using t h e proposed method, employing a glycerol-1,2,6-hexanetriol column, and the official AOAC method, 9.063-9.065. Since isobutyl and the atnyl alcohols comprise by far the greatest part of fusel oil, their determination is of major importance to the total fusel oil content . Statistical analyses show that the proposed method is superior to the AOAC method for the determination of these alcohols, whereas the official method is superior for the determination of ethyl acetate and n-propyl alcohol. In general, collaborators employing modern instrumentation preferred the proposed method over the AOAC method. The former method also separates and permits the quantitative measurement of active amyl and isoamyl alcohols. The proposed method has been adopted as official first action as an alternative to 9.063–9.065 for the determination of higher alcohols and ethyl acetate in whisky.

Total Nitrogen in Fertilizer: Collaborative Study

1978 ◽  
Vol 61 (2) ◽  
pp. 299-306
Author(s):  
Paul R Rexroad ◽  
Gary F Krause
Keyword(s):  
Total Nitrogen ◽  
Collaborative Study ◽  
Oxidation Catalyst ◽  
Official Method ◽  
Probability Level ◽  
Sulfate Sulfur ◽  
Powder Method ◽  
Modified Method ◽  
Accuracy And Precision ◽  
Cent Nitrogen

Abstract A modified comprehensive nitrogen method, using 0.4 g C11SO4 as catalyst, is presented. This method plus a modified Raney powder method (mercury-free) with no metallic oxidation catalyst are compared with the AOAC comprehensive nitrogen method. Results from 19 collaborating laboratories for 11 samples are evaluated. The modified Raney method gave significantly low results on 2 samples: 21-7-14 (nitric phosphates-non-sulfate sulfur) and tryptophan. The results for the average per cent nitrogen for 11 samples from the modified comprehensive nitrogen method were comparable to those from the official method at the 95 % probability level; the overall pooled standard deviations were also similar. In this collaborative study, the modified method (with copper) was equal in accuracy and precision to the official method (with mercury). The modified comprehensive nitrogen method has been adopted as official first action.

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.

Microchemical Oxygen Flask Sulfur Determination: General Review and Collaborative Study of an Alternative Method Using Thorin-Methylene Blue Indicator

1976 ◽  
Vol 59 (5) ◽  
pp. 1135-1139
Author(s):  
Laverne H Scroggins
Keyword(s):  
Methylene Blue ◽  
Collaborative Study ◽  
Critical Factor ◽  
Potassium Sulfate ◽  
Masking Effect ◽  
Average Deviation ◽  
Collaborative Studies ◽  
Sulfur Determination ◽  
The Mean ◽  
Barium Perchlorate

Abstract Recent collaborative studies of microchemical oxygen flask sulfur determinations are summarized and compared statistically, and the 1975 collaborative study is presented. This volumetric technique, using a peroxide solution as absorbent, barium perchlorate as titrant, and a combination of thorin and methylene blue as indicator, was tested by 8 collaborators. Data from 72 determinations were reported. The samples studied were sulfanilamide, benzylisothiourea hydrochloride, cystine, potassium sulfate, and potassium sulfate with a phosphate additive. Overall statistical results for the 3 pure organic compounds gave satisfactory values: average standard deviation 0.10, overall average deviation of the mean from the theoretical value 0.13, and average bias −0.04. The overall average deviation of the mean from the theoretical value for the potassium sulfate compound was high (1.94) in this study, and that of the phosphated potassium sulfate compound was even higher (6.46). Thorin-methylene blue does not require a titration assembly (required by tetrahydroxyquinone) and has greater stability than dimethylsulfonazo III whose indicator lag-time causes troublesome pseudo end points. However, a critical factor, when using thorin-methylene blue, is the masking effect of foreign ions. All reagents must be as pure as possible, since concentrations of chloride, fluoride, nitrate, phosphate, potassium, and sodium interfere. The thorin-methylene blue method for sulfur determination has been adopted as official first action as an alternative oxygen flask microchemical method of analysis.

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