Fig. 2

Workflow to Determine Residual TFV on Gel Applicators Using FTIR Spectroscopy. Calibration samples, solutions of known amounts of TFV and placebo gel, are applied to the FTIR spectrometer (Step 1) to generate spectra from each sample (Step 2). The spectral data from the calibration samples are used to develop a discriminant algorithm for determining the presence of TFV in clinical samples (Step 3). Using this algorithm, vaginal swab extracts are placed on the spectrometer upon which a computer is programmed to generate a yes or no readout based on the algorithm prediction (Step 4).