= W. G. Zijlstra
{c}
\b[W. G. Zijlstra] is the first author of a 1991 study with <A. Buursma> and <W. P. Meeuwsen-van der Roest> measuring visible and near-infrared reference spectra of human <hemoglobin> derivatives. The authors reported that small fetal/adult differences in <molar absorption coefficient> mattered for multicomponent analysis.<Absorption spectra of human fetal and adult oxyhemoglobin, de-oxyhemoglobin, carboxyhemoglobin, and methemoglobin by W. G. Zijlstra and others>[Byline; Abstract, first two sentences]{ref} The work connects experimental optical measurements to the quantitative interpretation of <blood> samples.
The central measurement distinction is between a chemical species and a total signal. <Oxyhemoglobin>, <deoxyhemoglobin>, <carboxyhemoglobin> and <methemoglobin> can all contribute to measured <absorbance>, while <functional oxygen saturation> uses only the first two in its denominator. A fitted total optical signal therefore needs chemical interpretation before it becomes an oxygen-transport quantity.
An original synthetic example makes that separation concrete. If inferred concentrations are $H_O=8$, $H_D=2$ and $H_C=2$ with the remaining species absent, then <functional oxygen saturation> is $8/(8+2)=0.8$, whereas <fractional oxyhemoglobin> is $8/(8+2+2)=2/3$. Multiplying every concentration by two doubles the mixture's predicted <absorbance> at fixed path length under the <Beer-Lambert law>, but leaves both fractions unchanged.
Reference spectra thus help distinguish composition, concentration and denominator choice. This is the scientific role of the documented study; it should not be confused with directly measuring <oxygen consumption>, <blood flow> or <cardiac output>. Those quantities require additional observations and balance assumptions.
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