To provide a measure of the total amount of exchangeable cations that can be held by peat expressed as mequiv./100 g air-dried peat, the modified method of Puustjärvi for cation exchange capacity has been proposed and studied collaboratively. The statistical treatment of the collaborators’ results indicate a satisfactory degree of precision and accuracy for the 3 products considered, moss, humus, and reed-sedge. The method for cation exchange capacity of peat materials, with the description of the transfer technique included, has been adopted as official first action. The 7 ASTM methods have been adopted as procedures.
This paper describes a simple, rapid modification of a method developed at the Fisheries Research Board of Canada for determining mercury in fish and other food products. Wet digestion and flameless techniques of atomic absorption spectrophotometry are used. Replicate analyses on different days showed good precision and samples spiked with known amounts of mercury showed adequate recovery.
Medicated feeds (pelleted or mash) containing guarantees of carbadox, furazolidone, nitrofurazone, and ethopabate are pretreated with water, extracted with 95% dimethylformamide overnight at room temperature, cleaned up on a column of alumina, and injected into a high pressure liquid chromatograph for quantitative measurement. Carbadox, nitrofurazone, and furazolidone can be separated; chromatograms show excellent baseline resolution, and results are in good agreement with colorimetric methods. The same extraction and cleanup can be used to improve colorimetric methods for furazolidone and nitrofurazone.
A liquid fertilizer containing phosphite was toxic to over 1,000 ha of corn (Zea mays L.) in southern Michigan. The fertilizer contained 9% N, 8% P, and 7.5% K and was applied over the seed at planting time. Toxicity was also obtained when the foliage was sprayed with the same fertilizer. Laboratory tests using paper chromatography and greenhouse trials identified the P source as a phosphite (HPO3)−2. Plants showed white, variegated streaking of the leaves in mild cases and spindly, rolled, yellowish‐white leaves in severe toxicity.
An atomic absorption Spectrophotometric (AAS) method for determining chelated iron in iron chelate concentrates was collaboratively studied by 13 laboratories. Nonchelated iron was selectively precipitated as ferric hydroxide from an aqueous solution of the sample by adjusting to pH 8.5 with sodium hydroxide. A filtered portion of the sample solution was diluted with 0.5N HC1, and the iron was determined by AAS using standards containing disodium EDTA. Six pairs of iron chelate materials (12 samples) were analyzed and the average coefficients of variation were iron EDTA 3.52%, iron HEDTA 4.16%, iron DTPA 3.55%, iron EDDHA 3.52%, iron citrate 2.86%, and iron DPS 8.47%. The method has been adopted official first action.
An empirical method for determining moisture, mineral, and organic content of peat has been proposed and collaboratively compared with a method similar to that used in Federal specifications for the purchase of peat. Moisture results were significantly low by the Federal method in all cases but generally were equally precise by both methods, indicating that larger samples do not greatly improve the precision. Ash results were about the same for both methods, although the Federal method gave higher precision; ashing conditions in the proposed method appear inconsistent due either to the lower ashing temperature or to the larger sample used. It is recommended that study be continued.
Carbadox (CBX), an antibacterial agent, and pyrantel tartrate (PT), an anthelmintic, are formulated either separately or together in swine feeds. The official Association of Official Analytical Chemists (AOAC) spectrophotometric methods for both drugs are long, nonspecific, and require standard addition techniques. Results by this technique are positively biased. A simple, direct, specific, high-pressure liquid chromatographic (HPLC) method to determine either one or both drugs simultaneously with apparent accuracy and precision is developed. Drugs are released from feed matrices by water, extracted with dimethylformamide (DMF), cleaned up on alumina, and quantitated by direct comparison to standards using a Whatman Partisil 10 ODS-3 column and a mobile solvent containing 23.5 +/- 1.5% DMF in phosphate buffer (pH 2.0). Fourteen laboratories participated in a collaborative study of this method for determination of CBX and PT in animal feeds.
A simple liquid chromatographic method for vitamin A (retinol) in animal feeds is described. The feed is saponified, diluted to minimize interferences, and extracted Into petroleum ether with a single step. The analysis is sensitive and specific with liquid chromatography and a fluorescence detector. The minimum level of detection is 15 ng/mL, which Is equivalent to 10 000 units/lb vitamin A. The method Includes a stable and reproducible standardization of vitamin A that Is used to calibrate standard peak heights In terms of units retlnol/mL. Guarantees of 10 000 units/lb up to premix levels can be analyzed with good recoveries and precision.
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