2nd International Plant Spectroscopy Conference (IPSC) 2019, Berlin, 24 - 28 March 104 P-019: Herbal characterization and discrimination perspectives using Fourier transform infrared photoacoustic spectroscopy (FTIR PAS) and diffuse reflectance infrared spectroscopy (DRIFT) Agnese Brangule, Pẽteris Tretjakovs Riga Stradiņš University, Department of Human Physiology and Biochemistry, Riga, Latvia E-mail: agnese.brangule@rsu.lv This study demonstrates the significant potential of cantilever-enhanced Fourier transform infrared photoacoustic spectroscopy (FTIR PAS) principles and diffuse reflective infrared spectroscopy (DRIFT) with a diamond stick. The improved sensitivity and reproducibility of both methods present an absolute tool in the study of herbals and plants. For many centuries, herbal medicine (HMs) has been used worldwide in traditional health care [1]. FTIR methods have been widely used since the 1960s [2] and can be used for both qualitative and quantitative analysis [3]. In the field of HMs, the FTIR fingerprint spectra have been used since early 1987 and are used less frequently than chromatography methods (CM) [4,5,6]. Until now, the introduction of FTIR methods was limited by the complexity of spectra and its interpretation. This problem can be resolved by using chemometrics and machine learning. The major advantages of FTIR methods are the following: it is sensitive and non- destructive or only slightly damages the sample; it requires minimal sample preparation at most; small sample quantities are necessary for measuring [2,3]. One of the important features of FTIR is the possibility to simultaneously determine different components in the same sample from a single instrumental measurement [7]. In previous studies, the FTIR spectroscopy’s sampling methods transmission and ATR was most widely used as DRIFT and cantilever-enhanced photoacoustic spectroscopy (FTIR PAS). FTIR PAS is based on the photoacoustic effect. If the substance is irradiated with a pulsating light, the substance emits acoustic waves that have the same frequency as the pulsating light. In this study, we evaluated dried herbals and green, and black tee (Figure 1). PAS and DRIFT spectra were taken at 450–4000 cm -1 , at a resolution of 4 cm -1 , and an average made from 10 scans. For PAS, the homogenized samples were placed in the PAS cell filled with helium gas (flow 0.5 l/min), but for DRIFT homogenized samples were placed on the diamond stick. Figure 1. FTIR PAS and FTIR DRIFT spectra of green tea and chamomile