Computation of HORRAT values.
The formula for the Horwitz ratio (HORRAT) as presented in the Study Director's Manual of AOAC INTERNATIONAL is applicable only when the concentration is in the unit/unit form (e.g., microg/microg, g/g, etc.). When the analyte concentration is a trace or mass fraction amount (e.g., microg/g), the formula generates incorrect HORRAT values. Alternative calculation procedures are presented to circumvent such problems.
McClure
Foster D
FD
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Scientific Analysis and Support, Division of Mathematics, 5100 Paint Branch Pkwy, College Park, MD 20740-3835, USA. fmcclure@cfsan.fda.gov
Lee
Jung-Keun
JK
D005504:Food Analysis / Q000592:standards / Q000706:statistics & numerical data*; D008433:Mathematics; D008832:Microchemistry; D015203:Reproducibility of Results