Analysis collaborative study

Sullivan, J. J., T. A. Hollingworth, M. M. Wekell et al. 1990. Determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow-injection analysis—Collaborative study. /. AO AC 73 35-42. 

An analysis of variance can be extended to systems involving more than a single variable. For example, a two-way ANOVA can be used in a collaborative study to determine the importance to an analytical method of both the analyst and the instrumentation used. The treatment of multivariable ANOVA is beyond the scope of this text, but is covered in several of the texts listed as suggested readings at the end of the chapter. 

An analysis of nearly 10,000 collaborative studies suggests that a reasonable estimate for a method s reproducibility is... 

Horwitz claims that irrespective of the complexity found within various analytical methods the limits of analytical variability can be expressed or summarized by plotting the calculated mean coefficient of variation (CV), expressed as powers of two [ordinate], against the analyte level measured, expressed as powers of 10 [abscissa]. In an analysis of 150 independent Association of Official Analytical Chemists (AOAC) interlaboratory collaborative studies covering numerous methods, such as chromatography, atomic absorption, molecular absorption spectroscopy, spectrophotometry, and bioassay, it appears that the relationship describing the CV of an analytical method and the absolute analyte concentration is independent of the analyte type or the method used for detection. 

Sections on matrix algebra, analytic geometry, experimental design, instrument and system calibration, noise, derivatives and their use in data analysis, linearity and nonlinearity are described. Collaborative laboratory studies, using ANOVA, testing for systematic error, ranking tests for collaborative studies, and efficient comparison of two analytical methods are included. Discussion on topics such as the limitations in analytical accuracy and brief introductions to the statistics of spectral searches and the chemometrics of imaging spectroscopy are included. 

A collaborative study conducted by Britton et al. (1984) to determine the most reliable method among the three most commonly used methods (two colorimetric methods and the specific ion electrode method) showed that both pyridine-barbituric acid and pyridine-pyrazolone have similar statistical accuracy. The pyridine-barbituric acid method was preferred by Britton et al. (1984) over the pyridine-pyrazolone method for its convenience (quicker analysis time) rather than the statistical accuracy of data. The electrode method had higher data variability. 

It is important to appreciate that the statistical significance of the results is wholly dependent on the quality of the data obtained from the trial. Data that contain obvious gross errors should be removed prior to statistical analysis. It is essential that participants inform the trial co-ordinator of any gross error that they know has occurred during the analysis and also if any deviation from the method as written has taken place. The statistical parameters calculated and the outlier tests performed are those used in the internationally agreed Protocol for the Design, Conduct and Interpretation of Collaborative Studies.14... 

As in many countries where maximum levels are set for the use of intense sweeteners in foods, analytical methods for identification and quantitative determination are required. Although a wide variety of methods is described, the European Standards for sweetener analysis deserve special attention. They were based on the most widely used analytical methods available and also demonstrated applicability and reliability in collaborative studies in several laboratories. 

Kennedy JW, Kaiser GC, Fisher LD, et al. Multivariate discriminant analysis of the clinical and angiographic predictors of operative mortality form the collaborative study in coronary artery surgery (CASS). J Thorac Car-diovasc Surg 1980 80 876-887. 

Precision plays a central role in collaborative studies. Wood [84] defines a collaborative trial as a procedure whereby the precision of a method of analysis may be assessed and quantified. Precision is the objective of interlaboratory validation studies, and not trueness or whichever other method performance parameter. Evalu-... 

M. G., Stella, C., Veuthey, J.-L., Estevenon, O., Van Schepdael, A., Roets, E., and Hoog-martens, J. (2003), Determination of uncertainty in analytical measurements from collaborative study results on the analysis of a phenoxymethylpenicillin sample, Anal. Chim. Acta, 481, 261-272. 

Association of Official Analytical Chemists (AOAC) International (2000), Method validation programs (OMA/PVM Department), including Appendix D Guidelines for collaborative study procedures to validate characteristics of a method of analysis, available http //www.aoac.org/vmeth/devmethno.htm. 

Precision is the degree of agreement between a series of measurements obtained from multiple sampling of the same homogeneous sample under prescribed conditions. Precision may be considered at three levels repeatability (precision under the same operating conditions over a short interval of time), intermediate precision (precision within-laboratory variations different days, different analysis, different equipment, etc.), and reproducibility (precision between laboratories, collaborative studies, usually applied to standardization of methodology). 

The reliability of a method can be determined by assessing certain method performance criteria including, specificity, accuracy, precision, limit of detection and quantitation, sensitivity, applicability, and practicability as appropriate (13). This very often requires that an extensive collaborative study be undertaken to obtain the necessary data. Methods that have successfully undergone this performance review testing have been considered to be validated for the purpose of the analysis (14). 

Protein dispersibility index Dry product is dispersed in water by blending, then centrifuged at 880 x g for I0 min Protein dispersibility index (%) = (% water-dispersible prolein/% total protein) x 100 Advantages Tested in a collaborative study and found to be reproducible between laboratories. Disadvantages Limited to soy products protein is determined by Kjeldahl analysis, which can be a lengthy procedure. AOCS Method B a 10-65 (AOCS, 1999) AACC Method 46-24 (AACC, 2000)... 

Tanner, J.T., Barnett, S.A., and Mountford, M.K. 1993. Analysis of milk based infant formula. Phase V. Vitamins A and E, folic acid, and pantothenic acid Food and Dairy Administration-Infant Formula Council Collaborative study. J. AOAC Int. 76 399-401. 

Since then, there have been a number of reversed-phase separations employing precolumn derivatization. Interestingly, fluorescamine (not frequently employed for RP-HPLC of amino acids with precolumn reaction) has been reported for taurine analysis in milk (197) and human plasma (198). Precolumn derivatization with OPA/2-mercaptoethanol has been reported for the analysis of infant formula and human breast milk (199). Although not the principal focus of the study, Carratu et al. (200) report taurine values in parenteral solutions as determined by FMOC. In an excellent article, Woollard and Indyk (201) report the dansylation of taurine for its determination in a wide variety of dairy-related products. Subsequently, the same authors report the results of a large collaborative study (202) for the determination of taurine (again, by dansylation) in milk and infant formula. This study afforded an overall interlaboratory RSD of 7.0% and established a lower limit for determination at 5 mg taurine per 100 g of product. 

DC Woollard, HE Indyk. Taurine analysis in milk and infant formulae by liquid chromatography collaborative study. J Assoc Off Anal Chem Int 80 860-865, 1997. 

EJ de Vries, B Borsje. Analysis of fat-soluble vitamins. 27. High performance liquid chromatographic and gas-liquid chromatographic determination of vitamin D in fortified milk and milk powder collaborative study. J Assoc Off Anal Chem 65 1228-1234, 1982. 

A collaborative study for the determination of ethoxyquin in various meals and extruded pet foods was done under Schreier and Greene (134). Eleven laboratories took part in the study and determined ethoxyquin in acetonitrile extracts of ground samples using a column packed with C,8 octadecylsilane and a mixture of acetonitrile and ammonium acetate solution as a mobile phase. The method was tested for the analysis of 16 samples that contained ethoxyquin from 0.25 to 289 ppm. Repeatability standard deviations ranged from 0.08 to 3.2 ppm, and repeatabil-... 

Three spectrophotometric procedures are given in the AOAC compendium of methods (960.22, 962.13 and 967.11) for the analysis of caffeine, all of which have an extraction stage followed by a quantification procedure. There is also an HPLC method, discussed earlier, which was designed to measure saccharin, benzoic acid and caffeine at the same time (AOAC, 978.08). Again, the HPLC method, EN 12856 1999 (Anon, 1999a), can be used for the analysis of caffeine, but this analyte was not included in the collaborative study. 

In recent years HPLC procedures have evolved as the methods of choice for the analysis of vitamin Do in bulk drug (32,33,53-61), pharmaceutical preparations (52-73), fortified milk (74-82), animal feed supplements (83-89), margarine (79), infant formulae (79), cod liver oil (90-93), and chicken egg (96). It may be pointed out that these reports represent the latest in the state-of-the-art in the HPLC analyses of vitamins Dg and D3. In spite of the intensive effort by a number of investigators and a few collaborative studies, there is no consensus on widely acceptable HPLC methods for vitamin D analysis in the bulk drug, pharmaceutical preparations, and fortified milk. 

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