Collaborative study of a method for the extraction of light filth from ground turmeric.

An improved method has been developed for the extraction of light filth from ground turmeric. The method involves an isopropanol defatting followed by a direct flotation from 40% isopropanol with Tween 80-EDTA (1+1) and hot mineral oil. Collaborative results show that the method is rapid and yields better filth recoveries than the official first action method, 44.118. The method has been adopted as official first action to replace 44.118.     

Collaborative study of a method for the extraction of light filth from whole, cracked, or flaked and ground spices.

An improved method has been developed for the extraction of light filth from whole, cracked, or flaked spices (basil, bay leaves, clery leaves, chervil, chives, dill weed, mint flakes, parsley, rosemary, sage, tarragon, thyme, and vegetable flakes) and from ground spices (cloves, cumin, marjoram, mustard seed, oregano, sage, and thyme). The method involves a chloroform or isopropanol defatting, followed by a direct flotation from 40% isopropanol with Tween 80-EDTA (1+1) and mineral oil-heptane (85+15). Collaborative results show that the proposed method is more rapid to perform and yields better filth recoveries than the official first action methods for ground spices, 44.116, and whole, cracked, or flaked spices, 44.129. The method has been adopted as official first action.     

Collaborative study of a gas-liquid chromatographic method for the analysis of propazine.

A gas-liquid chromatographic method for the determination of propazine in wettable powder formulations containing about 80% active ingredient was collaboratively studied, using a matched pair scheme. The propazine was extracted from the powder with chloroform, with dieldrin as an internal standard, and chromatographed on Carbowax 20M, using a flame ionization detector. Two samples were analyzed using peak height measurements with the following results (13 collaborators): 1.2% overall coefficient of variation and 1.2% coefficient of variation for the random error. Statistical evaluation of these factors reveals no evidence of systematic error contribution. The method has been adopted as official first action.     

Collaborative study of speaker identiication by the voiceprint method.

In the voiceprint method known and unknown voices are compared to determine if they are the same speaker. An unknown voice is recorded over the telephone onto a quality recorder. The known voice is similarly recorded, repeating the questioned message verbatim. An examiner determines, by means of acoustic spectrography and aural analysis, the similarities or differences existing between the known and unknown speakers. A positive conclusion is based on at least 10 pairs of like sounds. Five decisions are available for the examiner to make: positive identification, positive elimination, probable identification, probable elimination, and unable to make a decision with the sample submitted. Seven collaborators, chosen from various parts of the United States, were given recordings of 4 unknown speakers, 2 male and 2 female, to compare with similar recordings of 6 known speakers, 3 male and 3 female. A total of 21 positive identifications and 63 positive eliminations was possible. Twenty correct identifications and 47 correct positive eliminations were made. In 16 tasks, all involving the same unknown sample, collaborators reported they could not make a determination due to the poor quality of the sample. No false identifications were made; however, a trainee examiner, with less than 2 years experience, eliminated a known speaker when in fact a match did exist, thereby falsely eliminating the speaker. Examiners with more than 2 years of experience correctly identified all existing matches. This study indicates that a trained examiner can make very reliable decisions, using the aural and visual methods of comparing known and unknown voices. The voiceprint method has been adopted as official first action.     

Collaborative study of a method for the analysis of dry methoxychlor formulations.

A collaborative study has been completed on a method for determining methoxychlor content in dry formulations. The method is based on a total halogen determination plus a selective, qualitative thin lay chromatographic (TLC) measurement to establish the p,p'-methoxychlor is the primary halogen-containing organic species present in the formulation. After extraction of the sample with toluene, the toluene solution of methoxychlor is treated with sodium biphenyl to convert all halogen to the halide. The halide is then extracted with a solution of nitric acid and titrated with silver nitrate according to the Volhard procedure or potentiometrically, using a pH meter assembly. Based on the results obtained from 7 collaborators, the standard deviation of the method is about 0.48% at the 50% level. The qualitative TLC measurement is made on an aliquot of the initial toluene extract, using a selective halogen detection system. The method has been adopted as official first action.     

牛肉部分玻璃化转变温度研究

利用调制式差示扫描量热仪(MDSC)对牛肉糜和牛肉肌动球蛋白的部分玻璃化转变温度进行了测定，得出平均转变温度约为－52.54℃。实验研究了明胶、海藻酸钠和羧甲基纤维素钠对牛肉糜部分玻璃化转变温度的影响，结果表明3种添加剂对牛肉糜部分玻璃化转变温度均无显著影响。利用程序降温仪对牛肉糜进行冻结与解冻实验，结果表明在本实验的降温速率1～5℃/min范围内，降温速率越高，所需的冻结终温越低。     

Collaborative study of a method for chemical confirmation of the identity of aflatoxin.

The chemical method for confirmation of the identity of aflatoxin by derivative formation directly on the TLC plate was studied collaboratively by 8 participants. The results show that aflatoxin B-1 was confirmed in 17 of 17 sample extracts representing 15 mu-g aflatoxin B-1/kg peanut butter, in 13 of 16 extracts representing 5 mu-g/kg, and in none of the 7 aflatoxin-free extracts. Collaborators commented that the method was easily performed and gave good results. The method has been adopted as official first action.     

Collaborative study of a column chromatographic method for bendroflumethizide and cyclothiazide.

Bendroflumethiazide and cyclothiazide are eluted from a sodium carbonate column with chloroform-acetic acid (98+2) and are measured directly by ultraviolet spectrophotometry. The method was collaboratively studied by 8 analysts. The average per cent recovery and standard deviations for simulated mixes of bendroflumethiazide and cyclothiazide were 99.61+/-0.78 and 99.3+/-1.97. The method has been adopted as official first action for the determination of bendroflumethiazide.     

Collaborative study of a spectrofluorometric method for lasalocid sodium in feeds.

A collaborative study has been completed on a spectrofluorometric method for determining lasalocid sodium in finished poultry feeds. After a brief treatment of feed samples with pH 4.7 buffer, the drug is extracted with ethyl acetate. The ethyl acetate extract is further cleaned up by treatment with HCI and NaOH and quantitatively measured by spectrofluorometry. Nonspecific fluorescence is corrected for via the lasalocid-boric acid complex. The method is rapid, sensitive, and free of interference. A number of other feed additives, including monensin and ethoxyquin, do not interfere. Nine collaborators participated in the study and agreement between laboratories was satisfactory. The average recoveries of lasalocid sodium from the mash feeds added at levels of 0.0064, 0.0080, and 0.0096% were 100, 98, and 99%, respectively, and the corresponding coefficients of variation were 12.8, 8.2, and 8.0% (all results included). The method has been adopted as official first action.     

Collaborative study of a semiautomated fluorometric method for the determination of reserpine in tablets.

A semiautomated fluorometric method for the determination of resperpine in tablets was collaboratively studied by 7 laboratories. The method is a modification of the semiautomated method of Urbányi and Stober, which involves formation of a fluorogen with vanadium pentoxide. Collaborators were supplied with 3 composites, each from a different dosage level of commercial tablets. The results obtained agreed well with the AOAC manual fluorometric method; coefficients of variation ranged from 0.45 to 2.70%. The method has been adopted as official first action.     

Collaborative study of a method for the determination of ochratoxin A in green coffee.

A method for the semiquantitative determination of ochratoxin A in green coffee has been studied collaboratively by 11 laboratories. The average recovery for the 7 samples spiked at 3 levels of ochratoxin A was 69.1%, ranging from 60.5 to 85.6%. This is comparable to other visual thin layer chromatographic methods of mycotoxin detection. The method has been adopted as official first action for the determination of ochratoxin A in green coffee beans.     

Collaborative study of a gas-liquid chromatographic method for the analysis of chlorobenzilate and chloropropylate.

A gas-liquid chromatographic method for the determination of chlorobenzilate and chloropropylate in liquid formulations containing about 46 and 26% active ingredient, respectively, was collaboratively studied, using a matched pair scheme. The samples were dissolved in acetone containing debenzyl succinate as an internal standard and chromatographed on Carbowax 20M, using a flame ionization detector. Analyses of 4 samples by 13 collaborators using peak height measurements showed the following results: chlorobenzilate-2.5% overall coefficient of variation, 1.0% coefficient of variation for the random error, and 0.7% systematic error; chloropropylate-2.0, 1.4, and 0.4%, respectively. The method has been adopted as official first action.     

Collaborative study of the gravimetric method for the determination of mercury in chlorinated pesticide formulations.

The official first action AOAC gravimetric method for mercury, 6.C01-6.C03, and the official CIPAC titrimetric method, M2.3, were collaboratively studied by 4 CIPAC laboratories, using the same 4 samples analyzed by AOAC collaboration in 1972. Averages at the 3.7 and 3.4% level were the same by both methods whereas the CIPAC method produced, on the average, 4% higher results, all levels included. The AOAC method performs well in the presence of copper and chlorinated pesticides and is less complex to use than the present CIPAC method for mercury in these mixtures. The method has been adopted as official final action.     

Collaborative study of a rapid method for determing aflatoxins in cottonseed products.

Eleven laboratories collaboratively studied a modification of the official final action AOAC method, 26.048-26.056, for determining aflatoxins in cottonseed products. An aflatoxin-negative meal, 6 contaminated meals, 4 contaminated meats (kernels) samples, and 2 ammonia-inactivated meals were used. Mean aflatoxin values, mug/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.