an ultraviolet (UV) light source for producing broadband UV light;

a sample cell for holding the controlled drug waste sample and receiving the UV light;

an optical spectrometer for measuring transmitted UV light from the sample cell to obtain a UV absorption spectrum of the controlled drug waste sample;

a spectral library comprising the UV absorption spectra of controlled drugs, excipients in controlled drugs, and diluents; and

a processor generating a mixture spectrum using the library spectra of controlled drugs, excipients, and diluents in accordance to a description of the controlled drug waste sample and comparing the spectral shape and spectral intensity of the UV absorption spectrum of the controlled drug waste sample in reference to the mixture spectrum to verify type and concentration of the controlled drug waste sample, wherein the mixture spectrum is a linear combination of the library spectra of controlled drugs, excipients, and diluents, wherein coefficients of the linear combination are allowed to have negative values.

obtaining a description of the controlled drug waste sample;

obtaining an ultraviolet (UV) absorption spectrum of the controlled drug waste sample;

providing a spectral library comprising the UV absorption spectra of controlled drugs, excipients in controlled drugs, and diluents;

generating a mixture spectrum using the library spectra of controlled drugs, excipients, and diluents in accordance to the description of the controlled drug waste sample; and

comparing the spectral shape and spectral intensity of the UV absorption spectrum of the controlled drug waste sample in reference to the mixture spectrum to verify type and concentration of the controlled drug waste sample;

wherein the mixture spectrum is a linear combination of the library spectra of controlled drugs, excipients, and diluents, wherein coefficients of the linear combination are allowed to have negative values.

(i) obtaining an ultraviolet (UV) absorption spectrum of the controlled drug waste sample;

(ii) providing a spectral library comprising the UV absorption spectra of controlled drugs, excipients in controlled drugs, and diluents;

(iii) selecting a controlled drug from the spectral library and generating a mixture spectrum using the library spectra of the selected controlled drug, all possible excipients in the selected controlled drug, and all possible diluents, wherein the mixture spectrum is a linear combination of the library spectra of the selected controlled drug, the possible excipients, and the possible diluents, wherein coefficients of the linear combination are allowed to have negative values;

(iv) adjusting the coefficients of the selected controlled drug, the possible excipients, and the possible diluents in the mixture spectrum till the mixture spectrum has a maximum correlation in reference to the obtained UV absorption spectrum of the controlled drug waste sample;

(v) repeating steps (iii)-(iv) for all controlled drugs in the spectral library to obtain maximum correlation for all the controlled drugs; and

(vi) identifying a list of controlled drugs with their maximum correlation above a predetermined threshold as the possible type of controlled drug for the controlled drug waste sample.