Raman microspectrometric investigationof urea in calcite and gypsum powder matrices

Raman microspectrometry was used for the nondestructive detection of urea in artificially prepared mineral matrices. Various concentrations of urea, a possible biomarker, mixed with calcite and gypsum powders were analyzed using the 514.5‐nm line of an argon laser. Two types of measurements were carried out: direct measurements of powders and analysis of the same mixtures through natural, transparent crystals of calcite and gypsum. The detection limit for urea in artificial powder mixtures was 1 wt% for both calcite and gypsum. In the case of measurements through the monocrystals, the detection limit was between 1 and 5 wt% for calcite and slightly above 5 wt% in the case of gypsum.