The light scattered from translucent samples is used to obtain absorption-type spectra and provide quantitation of an absorber within the scattering bodies. Synthetic vesicles with an encapsulated dye, bromo-thymol blue (BTB), are employed as a novel model system to study the properties of translucent samples. Chlorophyll measurement in intact phytoplankton and algae is demonstrated. A least-squares fitting procedure is used to overcome the effect of chlorophyll fluorescence on the scattering data. A straight line relationship between a defined pseudo-absorbance and concentration is shown for both the BTB and chlorophyll data. A limit of detection of about 0.2 mg/L BTB is obtained for the synthetic vesicles. For chlorophyll the limit of detection is in the range of 1 to 5% of that found in the native plankton and algae samples.
William R. Englebreth, Charles K. Mann, and Thomas J. Vickers, "Diode Array Spectrophotometry of Translucent Materials," Appl. Spectrosc. 40, 1136-1141 (1986)