 G. N. Bowers Jr

G. N. Bowers Jr is an author of research on spectrophotometry and reference materials used for measurement calibration in biochemical analysis. In a 1980 study, Bowers and colleagues specified high-purity 4-Nitrophenol for standardizing measurements of alkaline phosphatase activity. Some commercial samples met their specifications; others required recrystallization or sublimation. This makes purity a practical part of the measurement, rather than an assumption about a reagent label.^[ref]

The same study reported a molar absorption coefficient of $(18380\pm 90)\mathrm{L}\mathrm{mo}{\mathrm{l}}^{-1}\mathrm{c}{\mathrm{m}}^{-1}$ at a wavelength of $401\mathrm{nm}$ and a temperature of $25{}^{\circ }\mathrm{C}$, for $35\mu \mathrm{mol}{\mathrm{L}}^{-1}$ 4-Nitrophenol in $10\mathrm{mmol}{\mathrm{L}}^{-1}$ sodium hydroxide. The stated solution conditions belong with the coefficient: it is not automatically the value for a different wavelength or reaction mixture.^[ref]

For an illustrative Beer-Lambert law calculation using the central reported coefficient, an absorbance $A=0.3676$ through a path length $\ell =1\mathrm{cm}$ gives a molar concentrationThis chosen example shows how characterizing a reference material connects an optical reading to an amount of substance in solution.