Ergosterol, a precursor of vitamin D, has δmax = 282 nm and molar absorptivity ε = 11,900 M-1cm-1. What is the concentration of ergosterol in a solution whose absorbance A = 0.43 with a sample pathlength l = 1.00 cm.?

3.6 * 10⁻⁵ M

Explanation:

Ergosterol has a maximum absorbance at λ = 282 nm. The absorbance of an analyte is related to its concentration through the Beer-Lambert's law.

A = ε * l * c

where,

A: absorbance

ε: molar absorptivity

l: optical path length

c; molar concentration

c = A / ε * l = 0.43 / (11,900 M⁻¹cm⁻¹) * 1.00 cm = 3.6 * 10⁻⁵ M