How do you calculate Horwitz?
How do you calculate Horwitz?
It is the ratio of the observed relative standard deviation among laboratories calculated from the actual performance data, RSDR (%), to the corresponding predicted relative standard deviation calculated from the Horwitz equation PRSDR (%) = 2C–0.15, where C is the concentration found or added, expressed as a mass …
What is Horwitz function?
The Horwitz function describes the trend of reproducibility SDs observed in collaborative trials in the food sector over a wide range of concentrations of the analyte. The Horwitz function serves an additional role as a fitness-for-purpose criterion in the form of the Horwitz ratio (HorRat).
What is the Horwitz curve?
The Horwitz curve is a very simple exponential relationship of the variability of chemical measurements in the interlaboratory environment to the concentration of the analyte, more or less independent of analyte, matrix, method, and time of publication.
What is HorRat value?
Abstract. The Horwitz ratio (HorRat) is a normalized performance parameter indicating the acceptability of methods of analysis with respect to among-laboratory precision (reproducibility).
Why does the Horwitz curve happen?
The Horwitz curve gives an indication of the precision to be expected of a newly developed method as a function of the concentration of the analyte. These are the most favourable conditions possible and they yield the best precision, (i.e., the smallest standard deviation).
Is the Horwitz equation required by ISO 17025?
measurement uncertainty, as required by ISO 17025. We recommend that, instead of using the Horwitz equation, there should be a proper identification of all components of uncertainty of measurement and reasonable estimation, as stipulated by the ‘‘Guide to the Expression of Uncertainty in Measurements’’ (GUM).
What should you use instead of the Horwitz equation?
We recommend that, instead of using the Horwitz equation, there should be a proper identification of all components of uncertainty of measurement and reasonable estimation, as stipulated by the “Guide to the Expression of Uncertainty in Measurements” (GUM). 1. Introduction
Is the Horwitz function problematic at zero analyte concentration?
As well, the Horwitz function potentially has a problem at zero analyte concentration, as noted by Holland et al. [6]. This is problematic because analytical blanks do not have infinite standard deviations. W. Horwitz, “Evaluation of analytical methods used for regulation of foods and drugs”, Anal. Chem. 54 ( 1982) 67-76.
Which is an intrinsic problem of the Horwitz equation?
Worse precision in the determination of aflatoxins can therefore be an intrinsic problem of aflatoxin determination rather than a concentration effect. This potential correlation between analyte type and analyte concentration casts further doubt on the applicability of the model. 3.2.