Brine Saturation Technique for Extracting Light Filth from Ground Cinnamon: Intralaboratory Study

An intralaboratory study was performed using the new brine saturation technique for isolating light filth from ground cinnamon. Recoveries of light filth averaged ^96.5%. The excellent recovery plus improvements in safety and simplicity give this new technique considerable advantage over the present official method.

Measurement of the Bioavailability of Iron, Using the Rat Hemoglobin Repletion Test

Variations in the AOAC official first action rat hemoglobin repletion test for iron were studied. These changes included (1) use of a simplified basal diet to eliminate ingredients which sometimes contribute too much iron; (2) increased fortification of the basal diet with vitamin E, pantothenic acid, and pyridoxine; (3) increased dietary copper; (4) variations in the carbohydrate source in the basal diet; (5) changes in the length of the depletion and repletion periods; and (6) comparison of prophylactic and curative procedures. The changes yielded results comparable to those obtained with the present official method. Further study may reveal that the depletion period can be shortened or eliminated. To fully meet the rat's vitamin requirements, increased levels of vitamin E, pantothenic acid, and pyridoxine are recommended. It is further recommended that the present method remain in official first action status, and that study be continued.

Microbiological Assay of Oxytetracycline in Liquid Supplements

The extraction procedure of the official final action method for the determination of oxytetracycline in dry feeds, 38.208–38.213, has been modified for the analysis of liquid supplements. Ten g samples were extracted with 50 ml acid-methanol and diluted to 100 ml with the same solvent. Aliquots of the extract prepared according to the modified extraction procedure were assayed by the present official method and gave an average recovery of 100.6% and a coefficient of variation of 6.2% at a medication level of 500 mg/lb. Assays performed on liquid supplements containing oxytetracycline stored for an average of 26 days at 37 and 21°C, and for 37 days at – 4°C showed potency retentions of 21, 80, and 97%, respectively, indicating a need for low-temperature storage prior to analysis.

Detection of Wheat Grains Contaminated with Urine

A modification of the present official method, 40.131-40.132 (Official Methods of Analysis, 11th Ed.), for the detection of urea is presented. Collaborative results show the modification of incorporating the urease and bromothymol blue in a soft (1%) agar to he more sensitive and responsive to the presence of urine on grains and seeds than the official method. The modified method has been adopted as official first action.

Collaborative Study of a Potentiometric Titration Method for Determining the Sodium Chloride Content of Canned Vegeable Products

A potentiometric method was compared with the official method, 32.018, for determining the sodium chloride content of canned vegetable products. The proposed method was very easy to use, simple, dependable, accurate, precise, and much faster than the present official method. The collaborative study consisted of 8 processed vegetable samples (canned tomato paste, sweet peas, green beans, yellow corn, sauerkraut, dill pickles, and 2 olive samples) submitted to 9 laboratories. The data from one collaborator were not included in the report because they differed too much from the others. The study indicated good agreement with the official method and very good precision as shown by the low standard deviations. It is recommended that the method be adopted as official first action. Further study is also recommended.

Determination of Water-Insoluble Nitrogen in Mixed Fertilizers

A procedure was developed for the determination of water-insoluble nitrogen which did not require alteration of the sample by grinding. Samples of the fertilizer were washed in a column with the equivalent of 100 inches of water. The residual nitrogen was then determined by conventional Kjeldahl procedures. The procedure was as reproducible as the present official method but was applicable to all types of sources of water-insoluble nitrogen. Since grinding was eliminated, particle sizesolubility relationships and coatings were not affected.

Determination of the Freezing Point of Milk by Thermistor Cryoscopy

Specific directions for the thermistor cryoscopic method, including uniformity in cooling, degree of supercooling, seeding, and reading procedures, are proposed for the present official method. It is emphasized that the instrument must be in the proper condition for use, must be properly calibrated, and must be properly utilized by the analyst. Each analyst should individually calibrate with standards by the same uniform procedure for standards and milk samples. The precautions necessary in the determination are part of the method and must be observed if the same sample is to yield the same freezing point value for different analysts, in different laboratories, at different times

Iodine in Iodized Salt

The official method for iodine in iodized salt, 31.064–31.067, was studied to determine interference from sodium thiosulfate added as a stabilizing agent; no interference was found. The present official method for iodine in iodized salt is reliable, and study of methods should be discontinued.

Determination of Salt in Butter

The official AOAC, 15.135, and International Dairy Federation (IDF) methods for determining the salt content of butter have been collaboratively studied. Results indicated that there was no significant difference (P > 0.05) between the method means. A highly significant difference (P < 0.001) was found between laboratory means which reflected individual differences in performing titration procedures and slight deviations from the prescribed procedure. The overall results indicated that the IDF method as studied was as accurate as the longer present official method, and the IDF method is recommended for adoption as official, first action.

A survey of maincrop potatoes I. Estimates of yield, 1948–50

The survey shows that objective estimates of the yield of maincrop potatoes can be obtained from small samples carefully selected and dug by hand. Samples taken from about 1000 fields gave estimates of the mean yield of all counties sampled with a standard error due to sampling of less than ± 0·2 ton/acre. The precision of the estimate could have been improved by a better distribution of samples among counties.The results point to underestimation on the part of the official estimates, in each of the 3 years, especially in the case of high yields in particular counties, and in particular years. The discrepancy between the official and the survey yields is of the order of 1¾ tons/acre, after all necessary corrections have been applied to the survey yields.The experience gained in the survey indicates that the method of sampling adopted provides an accurate and reliable method of estimating the yields of potatoes which could supplement, and, possibly, ultimately replace the present official estimates if more accurate estimates are required. A national scheme, properly designed, which would include all the potato-growing areas in due proportion should not be unduly expensive to operate. Estimates so obtained would not only be generally more accurate than those obtained by the present official method, but, perhaps more important, would indicate far more closely the fluctuation in yield from year to year.