William Horwitz (1918 – September 27, 2006 in
Olney, Maryland
Olney is a U.S. census-designated place and an unincorporated area in Montgomery County, Maryland. It is located in the north central part of the county, north of Washington, D.C.
Olney was largely agricultural until the 1960s, when growth of ...
) was an
analytical chemist
Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...
who is notable for formulating a description of the relationship between the variability of chemical measurements and the concentration of the analyte. This relationship, called the
Horwitz curve applies only to the between-laboratory variability of measurements.
* w = weight percent of analyte in sample
-w/w
* C = mass fraction of analyte in sample
imensionless= w / 100%-w/w
* predicted RSD (relative standard deviation) = 2^(1-0.5*log(C))%
Horwitz worked for the
U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
(FDA) for 57 years until his retirement in 2000 and was head of the
Association of Official Analytical Chemists for 24 years.
The Horwitz curve is "one of the most intriguing relationships in modern analytical chemistry";
[Meija, Juris]
"A chemical uncertainty principle challenge"
''Analytical and Bioanalytical Chemistry'', vol. 387, no. 5, March 2007, p. 1583-1584, DOI: 10.1007/s00216-006-1059-0 it is related to the
Variance-to-mean ratio
In probability theory and statistics, the index of dispersion, dispersion index, coefficient of dispersion, relative variance, or variance-to-mean ratio (VMR), like the coefficient of variation, is a normalized measure of the dispersion of a prob ...
.
References
Obituary: William HorwitzThe amazing Horwitz function
''Chemistry International'', Vol. 22, No. 6, November 2000
1918 births
2006 deaths
20th-century American chemists
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