Microbiological Assay of Streptomycin in Feeds: 1971 Collaborative Study

1972 ◽  
Vol 55 (4) ◽  
pp. 714-717
Author(s):  
John J Mayernik ◽  
Gloria Y Fiori ◽  
Shirley Hughes
Keyword(s):  
Sample Size ◽  
Reference Point ◽  
Collaborative Study ◽  
Microbiological Assay ◽  
Modified Method ◽  
Coefficients Of Variation ◽  
Aoac Official ◽  
Low Levels

Abstract The AOAC official first action method for the determination of streptomycin in feed in which the regular streptomycin assay agar is used was modified for application to the assay of low levels of streptomycin. The modifications consist of (1) increasing the sample size, (2) reducing the amount of agar in the assay plates, (3) lowering the concentration of the reference point on the assay plates, and (4) incubating the plates at 22–25°C instead of 37°C. Fifteen collaborators used the modified method to assay 6 feeds containing 5–30 g streptomycin/ ton. Mean recoveries ranged from 91.7 to 111.0% and coefficients of variation ranged from 5.8 to 8.7%. The method modified as described has been adopted as official first action for the assay of feeds containing 5–30 g streptomycin/ton.

Collaborative Study of Microbiological Assay for Low Chlortetracycline Concentrations in Final Feeds

1967 ◽  
Vol 50 (2) ◽  
pp. 446-449
Author(s):  
Anthony Abbey
Keyword(s):  
Sodium Hypochlorite ◽  
Animal Feed ◽  
Collaborative Study ◽  
Microbiological Assay ◽  
Poultry Feed ◽  
Assay Procedure ◽  
Coefficients Of Variation ◽  
Commercial Poultry ◽  
Low Levels ◽  
The Individual

Abstract Two batches of commercial poultry feed containing low levels of chlortetracycline (CTC) activity (ca 10 ppm) were assayed collaboratively in 15 laboratories. The coefficients of variation for the individual batches were 10.0 and 9.2%, respectively; combining the data for both batches gave a coefficient of variation of 9.6%. The microbiological assay procedure, utilizing compensating CTC standard curves prepared with a diluent containing sodium hypochlorite- inactivated animal feed extracts, was found applicable in all 15 participating laboratories. The method is recommended for adoption as official, first action.

Microbiological Assay of Streptomycin in Feeds

1971 ◽  
Vol 54 (1) ◽  
pp. 116-120
Author(s):  
John J Mayernik ◽  
Gloria Y Fiori
Keyword(s):  
Microbiological Assay ◽  
Modified Method ◽  
Coefficients Of Variation

Abstract The official AOAC first action non-sulfadiazine-sensitized method for the determination of streptomycin in feed was modified slightly. The modification consists of filtering the assay solution to remove the precipitate which forms when the solution is adjusted to pH 8. Eighteen collaborators used this modified method to assay 12 poultry and swine feeds containing 30-5000 g streptomycin/ton. Mean recoveries ranged from 97.6 to 104.0% and coefficients of variation ranged from 4.0 to 7.1%. It is recommended that approval of the non-sensitized method, as modified, be extended to 30 g/ton from the previously adopted level of 5600 g/ton.

Liquid Chromatographic Determination of Nitrogen Derived from Urea and Water-Soluble Methylene Ureas in Urea Formaldehyde Fertilizers: Collaborative Study II

1984 ◽  
Vol 67 (4) ◽  
pp. 768-770
Author(s):  
Allan D Davidson ◽  
◽  
C Barry ◽  
J Carmany ◽  
A F Grigor ◽  
...  
Keyword(s):  
Urea Formaldehyde ◽  
Collaborative Study ◽  
Chromatographic Determination ◽  
Water Soluble ◽  
Paired Samples ◽  
Coefficients Of Variation ◽  
Liquid Chromatographic Determination ◽  
Aoac Official ◽  
Liquid Chromatographic

Abstract A second collaborative study with 6 collaborators was conducted on the AOAC official first action method for measuring nitrogen derived from urea, methylenediurea (MDU), and dimethylenetriurea (DMTU). No variations were made. The collaborators made single determinations on 2 separate days on 5 sets of paired samples. The mean coefficients of variation for the completed study were 4.22% for urea, 5.08% for MDU, and 5.48% for DMTU, which are only slightly higher than the values reported in the first study: urea, 3.24%; MDU, 3.48%; and DMTU, 6.56%. The method has been adopted official final action.

Collaborative Study of the Determination of Dithiocarbamate Residues by a Modified Carbon Disulfide Evolution Method

1971 ◽  
Vol 54 (3) ◽  
pp. 528-532 ◽  
Author(s):  
George E Keppel
Keyword(s):  
Hydrogen Sulfide ◽  
Stannous Chloride ◽  
Collaborative Study ◽  
The Other ◽  
Dilute Acid ◽  
Trap Hydrogen ◽  
Modified Method ◽  
Coefficients Of Variation ◽  
Naoh Solution

Abstract A modified method for determination of dithiocarbamate residue recoveries from grain was studied collaboratively. In this method dilute acid with stannous chloride is added to the crop, which is then heated to boiling for the dithiocarbamate decomposition step. A mixture of NaOH solution and benzene is used to trap hydrogen sulfide and other volatile interferences. Collaborative results were low and erratic, with large coefficients of variation. The results of the Associate Referee, on the other hand, were better. Further study on this method is recommended.

Collaborative Study of the Official AOAC Method for the Determination of Biuret in Fertilizers

1974 ◽  
Vol 57 (6) ◽  
pp. 1360-1362
Author(s):  
Luis F Corominas
Keyword(s):  
Sample Size ◽  
Ammonium Carbonate ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Nickel Sulfate ◽  
Complexing Agent ◽  
Modified Method ◽  
Aoac Method ◽  
Larger Sample

Abstract The present official first action method for biuret, 2.073-2.075, has been compared with a modified version (larger sample size, vacuum removal of ammonia and ammonium carbonate, and recrystallization of biuret standard) and a colorimetric method using nickel sulfate as the color complexing agent. Five samples containing from 0.4 to 0.9% biuret were collaboratively studied. In general, the modified method yielded better results, based on 515 individual results reported by 7 laboratories.

Collaborative Study of a Modified Extraction Procedure for Lasalocid Sodium in Feeds by Microbiological Assay

1976 ◽  
Vol 59 (6) ◽  
pp. 1286-1289
Author(s):  
Jacob M Scheiner
Keyword(s):  
Ethyl Acetate ◽  
Collaborative Study ◽  
Extraction Procedure ◽  
Alcohol Concentration ◽  
Microbiological Assay ◽  
Extraction Technique ◽  
Poultry Feeds ◽  
Coefficients Of Variation

Abstract A collaborative study was conducted on a modified extraction technique in the microbiological determination of lasalocid sodium in finished poultry feeds. The feed is warmed briefly with pH 4.7 buffer and the drug is extracted with ethyl acetate. The extract is washed with HCl and NaOH and evaporated to dryness, and the residue is dissolved in hexane, partitioned into methanol-water (3+1), and diluted to assay range at a final alcohol concentration of 25% (v/v). Seven laboratories participated in the study. Average recoveries of lasalocid sodium added at 0.01035, 0.00863, and 0.0069% ranged from 93 to 99% for mash feeds and from 86 to 95% for pellets. The coefficients of variation averaged 11.2% for mashes and 9.8% for pellets. The modified extraction technique has been adopted as official first action.

Adaptation of the AOAC Fluorine Method for Determining Fluoride in Fish Protein Concentrate

1970 ◽  
Vol 53 (1) ◽  
pp. 3-6
Author(s):  
R. Bruce Klemm ◽  
Mary E. Ambrose Klemm
Keyword(s):  
Steam Distillation ◽  
Silica Sand ◽  
Official Method ◽  
Protein Concentrate ◽  
Fish Protein ◽  
Direct Titration ◽  
Modified Method ◽  
Aoac Official ◽  
Aoac Official Method

Abstract The AOAC official method, 24.029–24.035, for the determination of fluorine in foods was modified slightly to o btain quantitative recoveries of fluorine from samples of fish protein concentrate (FPC). The most important alterations include the use of steam distillation, the addition of finely ground silica sand in the distillation, a decrease in the distillation temperature, and the utilization of direct titration. Recoveries of fluoride added to FPC before ashing, using this modified method, averaged 96.0 ± 3.0%. Our results are in agreement with those of several other analysts who used a variety of methods.

Cryoscopy of Milk: Effect of Variations in the Method

1966 ◽  
Vol 49 (3) ◽  
pp. 511-515 ◽  
Author(s):  
R W Henningson
Keyword(s):  
Statistical Analysis ◽  
Sample Size ◽  
Freezing Point ◽  
Collaborative Study ◽  
Sample Temperature ◽  
Milk Samples ◽  
Two Samples ◽  
Temperature Rate

Abstract Bath level, sample temperature, rate of stirring, degree of supercooling, sample size, sample isolation, and refreezing of the sample were the variables in the thermistor cryoscopic method for the determination of the freezing point value of milk chosen for study. Freezing point values were determined for two samples of milk and two secondary salt standards utilizing eight combinations of the seven variables in two test patterns. The freezing point value of the salt standards ranged from –0.413 to –0.433°C and from –0.431 to –0.642°C. The freezing point values of the milk samples ranged from –0.502 to –0.544°C and from –0.518 to –0.550°C. Statistical analysis of the data showed that sample isolation was a poor procedure and that other variables produced changes in the freezing point value ranging from 0.001 to 0.011°C. It is recommended that specific directions be instituted for the thermistor cryoscopic method, 15.040–15.041, and that the method be subjected to a collaborative study.

Collaborative Study of a Modified Method for the Determination of Aflatoxins in Copra, Copra Meal, and Coconut

1971 ◽  
Vol 54 (4) ◽  
pp. 874-878
Author(s):  
F J Baur ◽  
J C Armstrong
Keyword(s):  
Aflatoxin B1 ◽  
Quantitative Measurement ◽  
Collaborative Study ◽  
Copra Meal ◽  
Modified Method

Abstract A collaborative study, in which 19 laboratories participated, was conducted on a modified method for the determination of aflatoxins in 2 copra samples, one naturally contaminated, and 4 samples of naturally contaminated copra meal. The sensitivity and precision of the modified method for aflatoxin B1 and total aflatoxins were comparable to the official methods for peanuts and peanut products. Aflatoxins B2, G1, and G2 were reported by most of the laboratories, but background interferences made quantitative measurement less reliable than for B1. The method as it presently stands is also applicable to the analysis of coconut. The method has been adopted as official first action; further study will be directed toward improved precision for analysis of aflatoxins B2, G1, and G2.

Multiresidue Gas Chromatographic Method for Determining Organochlorine Pesticides in Poultry Fat: Collaborative Study

1984 ◽  
Vol 67 (2) ◽  
pp. 284-289 ◽  
Author(s):  
James A Ault ◽  
Tim E Spurgeon ◽  
◽  
M M Anderson ◽  
R Bowers ◽  
...  
Keyword(s):  
Chromatographic Method ◽  
Collaborative Study ◽  
Gel Permeation Chromatography ◽  
Accuracy And Precision ◽  
Coefficients Of Variation ◽  
Poultry Fat ◽  
Gel Permeation ◽  
Detector Method ◽  
Gas Chromatographic Method

Abstract A gas chromatographic electron capture detector method is described for the quantitative determination of organochlorine pesticide residues in poultry fat. The samples are rendered and cleaned up using automated gel permeation chromatography. The collaborative samples consisted of 10 fortified samples and one incurred residue sample, all in duplicate. Fortification levels ranged from 0.15 to 1.0 ppm for a-BHC, lindane, cis- and frans-chlordane, octachlor epoxide, o,p' and p,p'-DDT, p,p'-DDE, p,p'-TDE, hexachlorobenzene, heptachlor epoxide, dieldrin, endrin, methoxychlor, mirex, and toxaphene. The average recovery was 91.9% with a range of 81-102%. The ranges of coefficients of variation were: CVo = 3.39-14.79%; CVL = 0-16.6%; and CVx = 5.82-19.0%. The results indicate accuracy and precision comparable to other official methodology. The method has been adopted official first action.

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