Liquid chromatographic method for determination of azinphos-methyl in formulated products: collaborative study

A liquid chromatographic method for determination of azinphosmethyl (Guthion) in formulated products has been developed. Samples are dissolved in acetonitrile and analyzed by reverse-phase chromatography using n-butyrophenone as an internal standard. The method was subjected to a collaborative study involving 15 participating laboratories. Each collaborator was furnished with reference standard, internal standard, and blind duplicate samples of Guthion 50% wettable powder (50WP), 3 flowable (3F), and emulsifiable concentrate (2L and 2S) formulations. Collaborators were instructed to evaluate the method by peak height measurements only. Relative standard deviations for reproducibility (RSDR) were 1.11, 6.28, 2.47, and 1.17% for the 50WP, 3F, 2L, and 2S formulations, respectively. The method has been approved interim official first action for determination of azinphos-methyl in the 50WP, 2L, and 2S formulations.     

Liquid chromatographic determination of carbofuran in technical and formulated products: collaborative study

A liquid chromatographic (LC) method for the analysis of technical and formulated carbofuran samples was evaluated in a collaborative study. Carbofuran is determined by reverse phase LC, using a water-methanol mobile phase and acetophenone as internal standard, and detected at 280 nm. Twelve samples, 5 formulations and technical matched pairs, were analyzed by 17 collaborating laboratories. Accuracy and variability of results are typical of large LC data sets. The method has been adopted official first action.     

Potassium as an index of fruit content in baby food products. Part I. Banana-containing and apricot-containing products.

Percentage ingredient labeling has been proposed for baby foods. We determined whether or not the potassium content of baby foods could be used to verify the quantity of fruit when the characterizing ingredients were apricots or bananas, fruits rich in potassium. Official values for potassium in fruit (USDA Handbook No. 8-9) did not agree well with actual analyses. The potassium levels of products of known composition were accurately predicted from analyses of the actual ingredients used to make the foods. For banana-containing monofruit products of variable or unknown composition, potassium analysis led to fruit level estimates consistent with either the known composition or the label declaration. For products of unknown composition made with apricot concentrate, however, potassium analysis led to fruit level estimates lower than the probable fruit content. The quantity of fruit in baby foods made with potassium-rich fruits can be estimated from the potassium content if the potassium value for the fruit is representative of the actual ingredients used to make the product. If potassium analysis is to be used to verify compliance with percentage ingredient labeling, there must be statutory specification of the single-strength fruit level for fruit reconstituted from concentrate.     

Liquid chromatographic method for analysis of elemental sulfur in pesticide formulations

A nonaqueous reverse-phase liquid chromatographic (LC) method has been developed to determine elemental sulfur in pesticide formulations. Samples were extracted in 50 mL of stabilized tetrahydrofuran (THF) by gentle swirling while sonicating for 1 min. A 5 microL aliquot was injected into the LC instrument equipped with a Vydac 218 TP 54 column. The mobile phase was methanol-acetonitrile-stabilized tetrahydrofuran (58.5 + 40 + 1.5). Sulfur was monitored at 280 nm. Retention time was approximately 5 min with total analysis time of 7 min. For 6 different products analyzed 12 times each, the coefficients of variations were all less than 3.5%. Purity of each sulfur peak was checked by using a photodiode array detector in the spectrum and absorbance ratio modes. No impurities were observed at the monitoring wavelength.     

Determination of the antibiotic fungicide validamycin A in formulated products by micellar electrokinetic chromatography.

A micellar electrokinetic capillary chromatographic method (MEKC) was used to determine validamycin A content in commercial products. The results indicated that this method was capable of analyzing the validamycin A content in formulated products with an instrument detection limit of 0.94 microg/mL and a method detection limit of 1. 70 microg/mL. Relative standard deviation (RSD) values of MEKC determination of validamycin A in formulated products ranged from 0. 61 to 2.09%. Recoveries of validamycin A in formulated products were in the region of 99.5-105.1%. All commercial products collected from markets contained validamycin A. The high percentage of recovery, the low detection limit, and the low RSD values confirmed that the MEKC technique is a senstivie and selective method.     

An automated procedure for the analysis of boron in plant tissue

Abstract

Boron analysis of plant tissue by the quinallzarin procedure has been adapted to the Technicon AutoAnalyzer system. Results obtained are comparable to those by the curcumin method for evaluating the boron status of the plant. Details of the mechanical assembly are presented and precautions to be observed are discussed. The suggested procedure permits the analysis of 30 samples of plant ash extract per hour.     

Validation of liquid chromatographic method for assay of chlorthalidone in tablet formulations

A stability-indicating, reverse phase liquid chromatographic (LC) method was developed for assay of chlorthalidone in tablet formulations. The chromatographic system separates the parent compound from its potential hydrolysis product (4'-chloro-3'-sulfamoyl-2-benzophenone carboxylic acid), which can be quantitated at low levels, and another degradation product (2-chloro-5-(1-methoxy-3-oxo-1-isoindolinyl)benzenesulfonamide), which was found during the experimental work. The procedure can also be used for content uniformity determinations. The general utility of the method was demonstrated by the assay of several product brands. The validated procedure was shown to be accurate, precise, reproducible, and specific.     

Determination of pyrethroid residues in agricultural products by an enzyme-linked immunosorbent assay

To determine cypermethrin and permethrin in agricultural products, a competitive enzyme-linked immunosorbent assay (ELISA) method was employed. The matrix interferences were minimized by direct dilution of the extracts. No further cleanup was needed. A minimum matrix effect with a 1:10 dilution of white wine for cypermethrin and a 1:200 dilution of red and white wines, fruits, and vegetables for permethrin was found when phosphate-buffered saline containing 40% methanol was employed as the diluent. Good recoveries of spiked levels were observed. The mean percentage recoveries of cypermethrin spiked in white wine and permethrin spiked in red and white wines were 99.7, 74, and 78%, respectively. The mean percentage recoveries of permethrin spiked in apple, banana, cucumber, lettuce, onion, and peach were 99.2, 105, 70.2, 97.5, 94.4, and 89.4%, respectively. Validation of the ELISA method with permethrin-spiked lettuce and peach was carried out using gas chromatography with mass spectrometry, resulting in a good recovery and correlation.     

Evaluation of liquid chromatographic methods for analysis of chlorphoxim formulations

Liquid chromatographic (LC) methods for determination of active ingredient in chlorphoxim formulations have been developed independently by Bayer AG and the Centers for Disease Control (CDC). Both methods specify separation on a silica gel column. The Bayer method uses a 5% solution of tetrahydrofuran in hexane as the eluting solvent and quantitates results on the basis of an external standard. The CDC method uses a 5% solution of ethyl acetate in hexane as the eluting solvent and uses 4-fluorophenyl sulfone as an internal standard. The 2 methods were compared by replicate analyses of samples of chlorphoxim technical and water-dispersible powder and emulsifiable concentrate formulations. The precision of both methods was acceptable.     

Rapid automated turbidimetric assay for chlortetracycline hydrochloride, using Leuconostoc mesenteroides as the test organism.

A rapid turbidimetric assay has been developed for chlortetracycline hydrochloride (CTC-HCl) in finished animal feeds and feed supplements, using Leuconostoc mesenteroides as the test organism. Two modifications are presented: The incubation period of modification 1 is 2.5 hr and the sensitivity of the assay is 0.03 microgram CTC-HCl/assay tube. Modification 2 has a sensitivty of 0.01 microgram CTC-HCl/assay tube and requires an incubation period of 3.5 hr. For 21 feed formulations, the turbidimetric method recovered 95.7% of label claim. Recoveries of CTC-HCl standards from the same feeds ranged from 93.4 to 134% with a mean of 103%. The relative standard deviation among day-to-day duplicates is 3.50% for the faster modification and 1.63% for the more sensitive modification.     

Validation of liquid chromatographic method for assay of calcitriol and alfacalcidol in capsule formulations

The validation of a liquid chromatographic procedure suitable for the determination of calcitriol and alfacalcidol in their respective formulations labeled to contain at least 0.25 micrograms drug per unit is described. The capsule content is diluted and chromatographed in 15-20 min on silica columns (5 micron) with a mobile phase of hexane-tetrahydrofuran-methylene dichloride-isopropanol (72 + 12 + 12 + 4, v/v) with detection at 254 nm. The calibration curve is linear. Recoveries of "spikes" averaged 101% with a standard deviation of 2%. Precision was better than 1.5%.     

Liquid chromatographic determination of penicillin V potassium in tablets and powders for oral solution

A reverse-phase liquid chromatographic method is described for the assay of penicillin V potassium in tablets and powders for oral solution. Under isocratic conditions, the combined use of an octadecylsilane column, with a mobile phase composed of acetonitrile-methanol-0.01M monobasic potassium phosphate (21 + 4 + 75, v/v), and photometric detection at 225 nm, separated penicillin V potassium from excipients, related compounds, and degradation products. Sulfadimethoxine was used as an internal standard. Detector responses were linearly related to concentrations of penicillin V over the range 25-225 micrograms/mL (r = 0.99997). Standard addition recoveries ranged from 98.8 to 99.9% (mean 99.5%, n = 8) for tablets and from 97.9 to 101.6% (mean 99.8%, n = 8) for powders for oral solution. The liquid chromatographic assay results were compared with those obtained by the official iodometric titration method. The proposed method is simple, selective, stability-indicating, and free from interference by excipients and degradation products.     

Gas chromatographic method for determination of fenitrothion in fenitrothion technical and in formulated products: collaborative study

A gas chromatographic (GC) method for determination of fenitrothion in fenitrothion technical and formulated products has been subjected to a collaborative study with 7 participating laboratories. Formulations are extracted with chloroform containing dibutyl sebacate as an internal standard and are analyzed by gas chromatography using an OV-210 column. Collaborators were furnished matched pairs of technical product and water-dispersible powder and emulsifiable concentrate formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 0.54, 1.00, and 1.56%, respectively, for technical fenitrothion, water-dispersible powders, and emulsifiable concentrates. The method has been approved interim official first action as an alternative to the present official first action AOAC method 6.A19-6.A24, which uses a polyphenyl ether, 6 ring (PPE-6R) column packing and fluoranthene as internal standard.     

Simplified automated procedure for measurement of certain catecholamine drugs delivered from aerosol inhalation units

An automated colorimetric method is described for the measurement of certain catecholamine drugs, such as isoproterenol and epinephrine, in sample solutions derived from 2 metered doses delivered from the mouthpiece of aerosol inhalation units. The procedure, applicable to the expressed product, involves oxidizing the catecholamine with potassium ferricyanide at pH 6 to produce an aminochrome. This method is similar to the well known trihydroxyindole reaction procedure but differs in that the formed aminochrome is measured spectrophotometrically at 495 nm instead of being further derivatized by alkaline rearrangement to the trihydroxyindole species followed by either spectrophotometric or fluorometric measurement.     

Improved microbiological assay for penicillin residues in tissues and stability of residues under cooking procedures

The microbiological assay for penicillin residues was improved by using centrifugation to remove physical barriers to diffusion, a small buffer/meat extraction ratio, and a more sensitive 2-layer assay system. Recoveries from muscle, kidney, and liver tissues ranged between 70.1 and 86.7% with measurable levels of 0.03--0.05 unit/g. By comparison, the Food and Drug-suggested methodology yielded recoveries of 45.9--54.0% and levels of detectability of 0.08--0.10 unit/g. Cooking of hamburger, steaks, and port chops indicated that procaine penicillin withstood cooking conditions, and significant levels of the original activity remained.     

Evaluation of an automated gel permeation cleanup and evaporation systems for determining pesticide residues in fatty samples

The AutoVap 600 system, used in conjunction with an automated gel permeation chromatography (GPC) instrument, automatically collects and evaporates the effluent from the GPC column, dissolves the residue in a fixed volume of desired solvent, and quantitatively transfers it to a sealed vial. This system was evaluated and found to automate efficiently the cleanup of butterfat for pesticide residue analysis. Quantitative recoveries were obtained for each of 4 pesticides fortified in butterfat and cleaned up through the system and for 12 pesticide standards in the absence of sample matrix collected through the system. After loading, the system operates unattended and will automatically prepare up to 23 individual fat samples for determination by gas chromatography without additional cleanup.     

Gas chromatographic method for determination of p,p'-DDT in DDT technical and formulated products: collaborative study

A gas chromatographic (GC) method for determination of p,p'-DDT in technical and formulated products was developed and it performed well in an initial small collaborative study among 4 laboratories. Samples are dissolved in chloroform, and p,p'-DDT is separated on an OV-210 column and determined by GC analysis with flame ionization detection. 2,2'-Dinitrobiphenyl is used as an internal standard. The method was subjected to an international collaborative study with 10 participating laboratories. Collaborators received matched pairs of technical DDT products and of water-dispersible powder, emulsifiable concentrate, and dustable powder formulations. Relative standard deviations for reproducibility (RSDR) for the paired samples were 1.16, 1.48, 2.08, and 1.80%, respectively. The method has been approved interim official first action by AOAC as a CIPAC-AOAC method.