In order to investigate if NAM-IR could identify components of interest in polluted samples, a sequence of experiments was performed, in which solutions of polystyrene (PS) latex beads were spiked with increasingly concentrated solutions of polyvinylpyrrolidone (PVP). In this way, the PS samples were polluted in a controlled manner, with a component known to have IR absorption peaks in the same region as PS.
Mixtures of PS and PVP were sampled onto SiN strings using a standard jet nebulizer setup, and NAM-IR spectra were obtained in the wavenumber range 1150–1850 cm−1.Fig. 8 shows measured NAM-IR spectra of PS/PVP mixtures in different ratios, compared to computationally generated spectra obtained by linear superposition of individual ATR-FTIR spectra of PS and PVP, in the relevant ratios. The NAM-IR spectra are normalized with respect to the QCL power.
Fig. 8.
Left column: NAM-IR spectra of different compositions of PS and PVP. Increasing concentrations of PVP is added to PS starting from the bottom of the column. Right column: measured ATR-FTIR spectra of pure PS (bottom) and PVP (top), along with computationally generated spectra obtained by linear superposition of the individual ATR-FTIR spectra of PS and PVP, in the relevant ratios. The vertical red lines indicate peaks stemming primarily from PS (at 1484 cm−1) and PVP (at 1685 cm−1), respectively. (For interpretation of the references to color in this legend, the reader is referred to the web version of the article.)