Determination of Phosphorus in Processed Cheese: Collaborative Study

1985 ◽  
Vol 68 (1) ◽  
pp. 102-104
Author(s):  
Gerald Steiger ◽  
William Horwitz ◽  
Lambrecht J Poortvliet ◽  
Petter Soderhjelm
Keyword(s):  
Systematic Error ◽  
Collaborative Study ◽  
Accuracy Control ◽  
Processed Cheese ◽  
Molybdenum Blue ◽  
Final Measurement ◽  
Cheese Products

Abstract A second interlaboratory collaborative study of the determination of phosphorus in processed cheese products by the molybdenum blue method verifies that this method is prone to producing a laboratoryinduced systematic error. It would be useless to continue to make minor modifications in the details of the method, which will improve only the within-laboratory precision, until an accuracy control of the final measurement step is incorporated into the method.

Collaborative Study of the Spectrophotometric Determination of Phosphatase Activity in Milk Utilizing a New Alkaline Phosphatase Assay System

1972 ◽  
Vol 55 (3) ◽  
pp. 498-503
Author(s):  
D H Kleyn ◽  
C L Huang
Keyword(s):  
Systematic Error ◽  
Collaborative Study ◽  
Correlation Coefficients ◽  
New Method ◽  
Statistical Comparison ◽  
Alkaline Phosphatase Assay ◽  
Phosphatase Assay ◽  
Method Analysis ◽  
Quantitative Procedure

Abstract A quantitative procedure (modified new method) has been studied that employs phenolphthalein monophosphate as the substrate and dialysis of released phenolphthalein followed by subseqvient measurement of the dialysate in a spectrophotometer at 550 nm. Nine collaborators evaluated 6 unknown samples of milk containing various levels of rawmilk, in triplicate, by the modified new method and the Scharer modified spectrophotometric method. Analysis of variance revealed that the random error of the modified new method was almost twice that of the Scharer technique, while the systematic error of the modified new method was only about ¼ that of the latter method. Two-sample charts indicated that the systematic error of the modified new method was less than that of the Scharer method; this was verified by a statistical comparison which showed that the total analytical error was much lower for the modified new method. A linear relationship was found between the 2 methods by 5 of the collaborators; the correlation coefficients ranged from 0.993 to 0.999. Based on these results, the method has been adopted as official first action for the analysis of milk.

scholarly journals Determination of Total Phosphorus in Foods by Colorimetry: Summary of NMKL Collaborative Study

1996 ◽  
Vol 79 (6) ◽  
pp. 1408-1410 ◽  
Author(s):  
T Katrhna Pulliainen ◽  
Harriet C Wallin
Keyword(s):  
Total Phosphorus ◽  
Phosphorus Content ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Milk Powder ◽  
Molybdenum Blue ◽  
Relative Standard ◽  
Standard Deviations ◽  
Skimmed Milk Powder

Abstract A collaborative study was conducted to validate a spectrophotometric–colorimetric method for determining total phosphorus in foods. The sample was dry-ashed in the presence of zinc oxide, and total phosphorus content was measured colorimetrically as molybdenum blue. Twelve laboratories from the Nordic countries participated in the study. The test materials included potato flour, sausage, cold ham, infant formula powder, cheese, and skimmed milk powder. Participants received 12 randomly coded samples of 2 blind duplicates of each material. Phosphorus contents of materials varied between 0.076 and 0.96 g/100 g. Relative standard deviations for repeatability of the method varied from 1.1% for 0.96 g phosphorus/100 g to 5.4% for 0.29 g phosphorus/100 g. Relative standard deviations for reproducibility varied from 3.6% for 0.96 g phosphorus/100 g to 7.7% for 0.23 g phosphorus/100 g. The colorimetric method for determination of total phosphorus in foods has been adopted first action by AOAC INTERNATIONAL as an NMKUAOAC INTERNATIONAL method.

Collaborative Study of the Thermistor Cryoscopic Method for the Determination of the Freezing Point Value of Milk

1968 ◽  
Vol 51 (4) ◽  
pp. 816-821
Author(s):  
R W Henningson
Keyword(s):  
Standard Deviation ◽  
Systematic Error ◽  
Freezing Point ◽  
Collaborative Study

Abstract Data from 19 collaborators for two sample pairs were used to estimate the precision and systematic error of the thermistor cryoscopic method for determining the freezing point value of milk. Precision was greater for the milks (0.0015°) than for the standards (0.004°). The systematic error was estimated to be 0.0033°. The standard deviation for interlaboratory individual determinations was estimated to be 0.0049°.

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