An HPLC method was developed to determine residues of individual isomers of brodifacoum (3-[3-4'-bromo[1,1'-biphenyl]-4-yl)-1, 2, 3, 4-tetrahydro- 1 -naphthalenyl]- 4 -hydroxy-2H- 1 -benzopyran-2-one) in rat tissue. The compound was extracted twice with 10% methanol in chloroform, filtered, and cleaned up by using automated gel permeation chromatography. A final cleanup on a silica gel SEP-PAK was added to protect the analytical column from irreversible adsorption and to reduce analysis time. The analysis was done on a μPorasil column; a UV detector was used for quantitation. Recoveries of brodifacoum added to rat tissue in concentrations of 0.12-5.0 ppm were greater than 90%.
A single comprehensive nitrogen method applicable to all fertilizers and to all forms of fertilizer nitrogen has been developed. The method utilizes untreated chromium metal powder in an acid medium to reduce nitrates. It quantitatively reduced nitrates alone, nitrates in the presence of organic matter, and nitrates in samples with high C1"/N03_ratios. Quantitative results were obtained with both solid and liquid fertilizer samples and with highly refractory organic samples. When subjected to the ruggedness test of Youden the method was "rugged."
Applications of an improved gel-solvent system for cleanup of pesticide residues by gel permeation chromatography (GPC) were investigated. Elution characteristics using Bio-Beads SX-3 gel and a toluene-ethyl acetate (1+3) elution solvent were determined for 16 nonicnic chlorinated pesticides, 3 polychlorinated biphenyls (PCBs), 14 chlorophenoxy herbicide esters, and 7 organophosphate insecticides. Elution patterns for vegetable and animal lipids were also studied. Quantitative recoveries of the pesticides were achieved. No liquid-liquid partitioning cleanup steps were required with any type of nonionic chlorinated pesticide or sample matrix. Only GPC cleanup was required for the nonionic chlorinated pesticides, PCBs, and organophosphate pesticide residues in chicken and turkey fat samples. Electron capture and flame photometric detectors were used in the gas chromatographic method for the respective pesticides. Samples containing up to 0.5 g lipid each were processed at the rate of one every 30–40 min with the automated system. Results were in excellent agreement with those from accepted manual partitioning methods and were achieved with significant savings of both labor and chemicals.
An automated spectrophotometric method utilizing the Technicon Autoanalyzer has been developed to determine nitrogen in fertilizer digestates in the range from 5 to 15 ppm nitrogen at a rate of 40 analyses per hour. NH4 is determined by reacting it with phenol and hypochlorite in an alkaline medium to form a blue compound closely related to indole phenol. Optimum reagent concentrations for the colored reaction were determined, and several ions were investigated to determine if they interfere with the reaction. Comparison of results obtained by the automated method and the comprehensive nitrogen method in primary standard grade NH4SO4 and KN03, Magruder check samples, and several commercial fertilizers show that the automated method is accurate and precise. The automated method results in considerable saving of analytical time, especially in laboratories analyzing large numbers of samples
An automatic photometric method utilizing the Technicon AutoAnalyzer has been developed to determine phosphorus in all forms of fertilizer phosphorus in the range of 2.0–4.5 mg P2O5/100 ml at a sampling rate of 40 analyses/hr. Multiple analyses of KH2PO4, 9 Magruder check samples, and numerous commercial fertilizers were made and compared with results obtained by the official quinolinium phosphomolybdate method, 2.025(b). Average range for five independent determinations was 0.22% P2O5 for the automated method and 0.26% P2O5 for the gravimetric method; average relative standard deviations were 0.44 and 0.60%, respectively. The average recovery of P2O5 from KH2PO4 was 99.8% with the photometric method and 100.3% with the quinolinium method. Results on 69 commercial fertilizers containing 5–54% P2O5 by the automatic method were only 0.02%% lower than those by the gravimetric quinolinium method. Results show that the automated phosphomolybdovanadate method for direct available phosphorus in fertilizers is accurate, precise, and less time consuming for routine control and industrial laboratories.
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