Automation of the AOAC Photometric Phosphomolybdovanadate Method for Direct Available P2O5

1966 ◽  
Vol 49 (6) ◽  
pp. 1213-1218
Author(s):  
Charles W Gehrke ◽  
James H Baumgartner ◽  
James P Ussary
Keyword(s):  
Sampling Rate ◽  
Gravimetric Method ◽  
Photometric Method ◽  
Available Phosphorus ◽  
Automatic Method ◽  
Average Recovery ◽  
Automated Method ◽  
Relative Standard ◽  
Standard Deviations

Abstract 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.

Automated Method for the Determination of Direct Available P2O5 in Fertilizers

1973 ◽  
Vol 56 (5) ◽  
pp. 1078-1083
Author(s):  
Larry G Hambleton
Keyword(s):  
Primary Standard ◽  
Sampling Rate ◽  
Gravimetric Method ◽  
Ammonium Citrate ◽  
Photometric Method ◽  
Ferric Pyrophosphate ◽  
Color Development ◽  
Automated Method ◽  
Significant Difference ◽  
Coloring Matter

Abstract An automated photometric method for the analysis of direct available P2O5 in fertilizers has been developed. The method utilizes basic AutoAnalyzer equipment along with a heating bath to destroy ammonium citrate and coloring matter and also to hydrolyze non-orthophosphates. The 0.15 and 0.35 mg P2O5/ml ranges are expanded to read 10 and 90% T, respectively, with a sampling rate of 30 analyses/ hr. Experiments were conducted to show the effect of acid and ammonium citrate concentrations on color development. The normality of acid needed to completely hydrolyze the phosphorus in non-orthophosphate samples was also determined. Results for samples of urea-ammonium polyphosphate, sodium pyrophosphate, sodium metaphosphate, and ferric pyrophosphate analyzed by the automated method are reported and compared to results on the same samples analyzed by the official final action gravimetric quinolinium molybdophosphate method, 2.023–2.025; good agreement was shown between the methods. Six replicate determinations on 5 mixed fertilizer samples and a KH2PO4 primary standard by each method were in close agreement. The accuracy of the automated method was confirmed by analyzing 312 routine fertilizer samples by both the automated method and the gravimetric method; results did not show a significant difference when compared by Students’ l-test at the 5% level.

Spectrophotometric Determination of Cyclamate in Soft Drinks and Desserts: Complementary Collaborative Study

1988 ◽  
Vol 71 (6) ◽  
pp. 1212-1214
Author(s):  
Anna-Maija K SJÖBERG
Keyword(s):  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Soft Drink ◽  
Collaborative Study ◽  
Soft Drinks ◽  
Food Control ◽  
Average Recovery ◽  
Relative Standard ◽  
Standard Deviations

Abstract Fifteen official food control laboratories participated in a collaborative study of a spectrophotometric method to determine cyclamate in a soft drink and a dessert at concentrations of 90-311 mg/L and 202-526 mg/kg, respectively, with blind duplicates and a blank. Average recovery from the soft drink was 97.5%, and from the dessert, 98.6%. Reproducibility relative standard deviations were 4.7-6.5% and 6.9-8.5%, respectively. The outlier percentage was 5.5%. This study complements an earlier work by leading Nordic food laboratories and was designed according to the latest recommendations. The results of this study were compared with those of the earlier collaborative study and with general collaborative results obtained by AOAC.

Automated Method for Determining Direct Available P2O5 in Fertilizers

1974 ◽  
Vol 57 (4) ◽  
pp. 785-790
Author(s):  
Larry L Wall ◽  
Charles W Gehrke
Keyword(s):  
Sampling Rate ◽  
Gravimetric Method ◽  
Ammonium Citrate ◽  
Slight Effect ◽  
Flow Rates ◽  
Automated Method ◽  
Accuracy And Precision ◽  
Analytical System ◽  
Hydrolysis Of ◽  
Heating Bath

Abstract In the automated method for the analysis of direct available and total P205 in fertilizers, a heating bath is used to destroy ammonium citrate and colored material and for hydrolysis of non-orthophosphates. The heating bath was maintained at 98°C and contained a 40' time delay coil, providing 15 min digestion. Improvements on the method for the automated digestion of citrate extracts of fertilizer included decreasing the reagent and sample flow rates by factors of 2 to 5. All of the citrate in those samples containing the highest levels of citrate was not destroyed; however, the slight effect of the remaining citrate could be eliminated by changing the concentration of the molybdovanadate reagent. No difficulty was encountered with the hydrolysis of non-orthophosphates. With this analytical system, steady state conditions were reached at a sampling rate of 40 samples/hr and with a 4 : 1 sample-to-wash ratio. Repeated analyses were made on 9 samples, and the accuracy and precision of results obtained by the automated method compared very well with data by the official AOAC gravimetric method.

Automated Urease-Chromous Method for Determining Nitrogen in Fertilizers

1979 ◽  
Vol 62 (3) ◽  
pp. 503-508 ◽  
Author(s):  
Larry L Wall ◽  
Charles W Gehrke
Keyword(s):  
Sample Preparation ◽  
Sampling Rate ◽  
Screening Method ◽  
Colorimetric Method ◽  
Diammonium Phosphate ◽  
Automated Method ◽  
Relative Standard ◽  
Single Method ◽  
Analytical System ◽  
And Control

Abstract An automated urease-chromous colorimetric method (AUCM) has been developed for determining nitrogen in fertilizers. The method is applicable to fertilizer samples that contain only ammoniacal, nitrate, and urea nitrogen. The concept of this method, combining nitrate reduction and enzymatic urea hydrolysis to produce a single method for total nitrogen, is new. The AUCM is an almost totally automated method with only an acidic dissolution step as the manual sample preparation. The urea is hydrolyzed to ammonia and carbon dioxide with urease, and the nitrate is reduced to ammonia with chromous ion within the continuous flow analytical system. The final step, also within the analytical system, is the spectrophotometric measurement of the ammonia, employing the ammonia-salicylate-hypochlorite chemistry. The sampling rate is 30 samples/hr. The method is not applicable to fertilizer samples containing refractory organic nitrogen forms, water-insoluble nitrogen, or significant levels of biuret. The average per cent nitrogen recovery by the AUCM for ammonium nitrate-diammonium phosphate bulk-blended fertilizer samples was 99.7, suspensions and liquids 99.7, urea fertilizers 97.8, and urea-diammonium phosphate bulk blends 98. The relative standard deviation for the analytical system was 0.40%, and for the method, 0.70%. The sample preparation is short and simple. This method offers many advantages as a screening method for fertilizer industry and control laboratories.

Collaborative Study of the Photometric Molyb do vanadate Method for Phosphorus

1965 ◽  
Vol 48 (3) ◽  
pp. 654-657
Author(s):  
Mary Heckman
Keyword(s):  
Collaborative Study ◽  
Gravimetric Method ◽  
Volumetric Method ◽  
Photometric Method ◽  
Coefficients Of Variation ◽  
Standard Deviations ◽  
Official Status ◽  
Feed Samples ◽  
Phosphorus Levels ◽  
Good Agreement

Abstract Sixteen laboratories analyzed five feed samples, with phosphorus levels ranging from about 0.60 to 5.50% by the photometric molybdovanadate method studied in 1963 (This Journal, 46, 836 (1963)), and by either the volumetric method, 22.061, or the gravimetric quinoline molybdate method (ibid., 47, 170 (1964)), both of which have some official status. Eight sets of results based on the volumetric method and eight based on the gravimetric method were available. Means for all methods were in good agreement. Standard deviations and coefficients of variation were satisfactory for all methods, indicating superiority of both volumetric and gravimetric methods over the photometric method. Calculation of standard deviations for the entire range tested, however, showed the photometric method to be superior to the volumetric method and inferior to the gravimetric. The molybdovanadate method was adopted as official, first action.

Automation of the Flame Photometric Method for Potassium in Fertilizer Grade Potassium Salts

1965 ◽  
Vol 48 (4) ◽  
pp. 865-868
Author(s):  
James P Ussary ◽  
Charles W Gehrke
Keyword(s):  
Photometric Method ◽  
Potassium Salts ◽  
Considerable Saving ◽  
Large Numbers ◽  
Relative Standard ◽  
Aoac Official ◽  
Standard Deviations ◽  
Flame Method ◽  
Analytical Time

Abstract Five selected commercial salts and two reagent grade salts were analyzed for potassium at least 10 times independently by both the automatic flame photometric method and the AOAC official STPB method. The flame photometric results were as precise and accurate as the official STPB results. The relative standard deviations were 0.36% K2O for the automated flame method and 0.32% K2O for the STPB method. The averages of the results (100.1%) on the reagent grade salts were very close to the theoretical values. The automatic flame photometric method for potassium in fertilizer grade potassium salts is accurate and precise, and results in a considerable saving in analytical time, especially for laboratories routinely analyzing large numbers of samples.

Determination of Total Dietary Fiber in Foods and Food Products by Using a Single-Enzyme, Enzymatic-Gravimetric Method: Interlaboratory Study

1995 ◽  
Vol 78 (6) ◽  
pp. 1440-1443
Author(s):  
Betty W Li
Keyword(s):  
Dietary Fiber ◽  
Gravimetric Method ◽  
Food Composition ◽  
Interlaboratory Study ◽  
Department Of Agriculture ◽  
Total Dietary Fiber ◽  
Relative Standard ◽  
Simplified Method ◽  
Standard Deviations

Abstract A simplified enzymatic-gravimetric method for total dietary fiber (TDF) determination has been published and used in the Food Composition Laboratory of the U.S. Department of Agriculture since 1988. This method gives comparable results to AOAC Official Methods 985.29 and 991.43 but the AOAC methods use 100°C (water bath) to gelatinize the sample and a combination of α-amylase and an amyloglucosidase to hydrolyze starches, whereas the simplified method incorporates an autoclaving step (121°C) for gelatinization followed by incubation with only amyloglucosidase. The simplified method omits protease hydrolysis and does not require any pH adjustment. Overall, the simplified method cuts cost and is less labor intensive. An interlaboratory study was conducted to validate this method. Blind duplicates of six sample (baked beans, corn bran, roasted peanuts, cooked potatoes, white bread with reduced calories, and cooked white rice) were sent to 11 laboratories. The reproducibility relative standard deviations of the TDF values (without outliers) ranged from 3.46 to 27.6%. The repeatability standard deviations ranged from 0.91 to 14.6%.

Spectrophotometric Determination of Nitrate in Baby Foods: Collaborative Study

1994 ◽  
Vol 77 (2) ◽  
pp. 425-430 ◽  
Author(s):  
Anna-Maua K Sjöberg ◽  
Timo A Alanko
Keyword(s):  
Collaborative Study ◽  
Photometric Method ◽  
Chromatographic Technique ◽  
Baby Foods ◽  
Relative Standard ◽  
Food Matrices ◽  
Standard Deviations ◽  
Liquid Chromatographic ◽  
Concentration Levels

Abstract A collaborative study was conducted of a spectro-photometric method for determination of nitrate after cadmium reduction to nitrite in baby foods containing meat. Thirty-one municipal and 2 industrial food laboratories participated in the study. The study design involved 2 baby food matrices. Samples of both matrices were prepared at 3 concentration levels between 52 and 309 mg NaNO3/kg as blind duplicates. A blank without added nitrate was also included. The outlier percentage of the results was very low (4.3%). It was typical for the method that recoveries were slightly >100%. Recoveries for baby foods varied between 113.3 and 116.9%, and were acceptable for control purposes. The relative standard deviations for repeatability were 5.0–18.1%. The relative standard deviations for reproducibility were 8.3–21.6%. Three collaborators also evaluated liquid chromatographic technique for nitrate determinations. These preliminary results are presented but are not analyzed statistically. The spectrophotometric method was adopted first action by AOAC INTERNATIONAL.

Gravimetric Determination of Ash in Foods: NMKL Collaborative Study

1989 ◽  
Vol 72 (3) ◽  
pp. 481-483 ◽  
Author(s):  
Anna Birthe Mortensen ◽  
Harriet Wallin
Keyword(s):  
Collaborative Study ◽  
Gravimetric Method ◽  
Constant Weight ◽  
Gravimetric Determination ◽  
Relative Standard ◽  
Standard Deviations ◽  
Food Commodities

Abstract A gravimetric method for the determination of ash was collaboratively studied in 14 laboratories. The food is ashed at 550 °C to constant weight and the ash is determined by weighing. Seven samples of various food commodities with estimated ash contents varying between low and high (0.07-8.0 g/100 g) were included in the study. The relative standard deviations for reproducibility varied, ranging from 1.0 and 1.3 for ash contents of 7.2 and 8.0 g/100 g, to 11 ± 1% for low ash contents of 0.07 and 0.27 g/100 g.

Enzymatic-Ultraviolet Method for Measuring Lactose in Milk: Collaborative Study

1984 ◽  
Vol 67 (3) ◽  
pp. 637-640 ◽  
Author(s):  
David O Biltcliffe ◽  
Dick H Kleyn ◽  
J Richard Trout ◽  
◽  
D Azzara ◽  
...  
Keyword(s):  
Food Industry ◽  
Collaborative Study ◽  
Skim Milk ◽  
Gravimetric Method ◽  
T Test ◽  
Enzymatic Method ◽  
Commercial Laboratory ◽  
Aoac Method ◽  
Standard Deviations

Abstract Collaborators in 8 dairy and food industry laboratories performed one lactose determination on each of 8 unknown samples of milk, lowfat milk, or skim milk, as 3 pairs of blind duplicates. Two known samples were provided to gain experience prior to analysis of the unknown samples. All of the above samples were also analyzed for lactose content by the official AOAC gravimetric method (16.507) by a commercial laboratory. From the overall mean of results on all samples, determinations by the enzymatic method averaged 0.49% lower than by the AOAC method. This difference was significant by the t-test (P = 0.05), which indicated a lack of agreement between the compared methods in determining lactose content. Standard deviations were similar for the 3 sets of blind duplicates which ranged between 3.67 and 4.55% lactose content. F-values revealed that variations between means obtained by laboratories differed significantly as compared with variations within laboratory means. The method has been adopted official first action.

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