In our design, the analyte is dissolved in EtOH. As we discuss below, this enables concentration discrimination versus % purity, which we argue is the more useful information to give to a person intending on using the drug. The solubilized sample is irradiated in a custom holder composed of a UV and chemically resistant material that is simple to wipe clean and holds a 2.2 mL volume. The total cost of the device as shown in Figure is ~$2,000, with the cost being dominated by the spectrometer. The device benefits from being operated by a customizable microcomputer, meaning both data acquisition and analysis can be controlled. The device operates by optimizing the signal such that the detector integration time is consecutively increased until the detector is at 80% saturation, assuming a linear relationship between signal size and integration time, which is a reasonable approximation. Figures and shows the resultant output of the device with EtOH present both as a two-dimensional plot (Figure ) and a contour plot (Figure ). The data essentially show the specular-and diffuse-reflection from the excitation sources since there is no analyte present and we note these data are not normalized for differences in integration time. For clarity, in fluorescence spectroscopy (e.g. Figure ), the reflected excitation source data are almost always excluded since they typically dwarf emission signals. However, as we discuss below, we have found these data to be useful, and so the geometry of the device shown in Figure is set-up to achieve some approximate parity between these signal sizes (acknowledging this varies widely for different molecules) and fluorescence emission (discussed below). Note, that the contour plot graphic shown in Figure interpolates between the data points to give the illusion of a higher resolution scan and is to aid the eye only. Figures and show the collected data with Diazepam at a relatively low concentration (0.5 mg/mL) compared to the pharmaceutical dose (we consider concentration effect in detail below). From these data there is clear discrimination of the emission resulting from the analyte, manifesting as new emission bands centered largely at ~ λem = 385 nm. Moreover, we also find variance in the reflected incident light, with notable quenching of LEDs > 305 nm. Hybridised fluorescence and reflectance fingerprints. With our device in hand, we consider how it can be implemented to discriminate both BZD type and concentration. The magnitude of fluorescence emission is related to the concentration of a fluorophore, However, the magnitude of emission is usually a poor means to assess concentration, owing to a raft of potential convolving effects including collisional quenching, FRET, and the inner filter effect. Figure demonstrates this challenge for a range of concentrations of diazepam, showing that the peak of the emission saturates with increasing concentrations (~5 x pharmaceutical dose). These data illustrate that fluorescence emission alone becomes unreliable at high concentrations of an analyte. Instead, the absorption of an analyte is a more reproducible means to assess concentration. Absorbance spectra were measured for 24 benzodiazepine standards and these data are shown in Figure . As expected, a significant variation in absorbance across different BZDs was observed, consistent with the variation in electronic structure. Consistent absorption features between compounds of the same structural class (Figure ) was also observed. Whilst the variation in electronic absorption spectra with variation in structure is not a surprise result, it demonstrates the principle that different BZDs will absorb different wavelengths of light preferentially and characteristically. As, such, we suggest that hybridizing both the FSF and information from analyte absorption might provide a means to both identify and quantify benzodiazepines, which we refer to as hybrid spectral fingerprinting (HSF). Potentially, the magnitude of the reflected excitation source contains a wealth of information on the absorption of an analyte. That is, as the concentration of a fluorophore Figure . Relationship between absorption spectra, concentration, reflectance, and emission. (A-D), alprazolam, low dose 0.25mg (0.1mg/mL), medium dose 0.5mg (0.2mg/mL), high dose1.5mg (0.6mg/mL) (E-H), etizolam. Low dose 0.75mg (in 2.5mL, 0.3mg/mL), medium dose 1.5mg (0.6mg/mL), high dose 3mg (1.2mg/mL). (I-L), lorazepam, low dose 0.5mg (in 2.5mL, 0.2mg/mL), medium dose 2mg (0.8mg/mL), high dose 4mg (1.6mg/mL).