Valuable Techniques for Repeatable Absorbance Measurements

Spectroscopy offers a range of available techniques that can be differentiated by the use or omission of reference spectra. This differentiation means that techniques such as Raman or fluorescence typically look at raw intensity outputs, whereas techniques such as transmission or reflectance require some reference scan to calculate those relative outputs. Within the group of referenced spectral techniques, absorbance is easily one of the most common and offers much value because of the concentration dependence of Beer's Law. However, this value is only properly captured when system components and samples are made to be repeatable, both for the reference scans and live acquisitions. This article discusses several useful techniques to establish this repeatability, including proper cuvette and probe handling, component setup, and sample considerations. By optimizing repeatability of the measurement system, the observed concentration values calculated from absorbance outputs are much more accurate and relevant to the sample being measured.