Preparing and analyzing a fluid for a multi-spectral analysis is disclosed. The multi-spectral analysis includes providing two or more separate and independent types of spectroscopies including at least a first spectrometer and a second spectrometer of a spectrometer system to examine the fluid after that fluid has passed through one or more sample preparation processes to increase a purity of a target biological entity in the fluid and thereby enhance signal to noise ratios in measurements and related data analysis operations.