## 2 Analytical Methods for Phytocannabinoid Profiling
### Instrumental Analysis
#### 2.2.4 Vibrational Spectroscopy Methods  
In the past decade, vibrational spectroscopy techniques (IR, NIR, MIR, FTIR and Raman) emerged as process analytical tool in the pharmaceutical industry for monitoring various quality attributes, and as such were recognized by United States Food and Drug Administration (FDA) [201]. Their ability for high-throughput screening of large volume of sample for a short period of time can exert sampling-based errors and provide rapid, versatile and non-invasive approach in qualitative and quantitative profiling and growth staging of cannabis plant and extracts (Table S3). The vibrational IR and Raman spectroscopy are considered complementary techniques; even though both are relying on different physical processes, their main observations are focused on light-induced molecular excitation [202]. Vibrational spectroscopy is based on sample's absorption of light at a defined wavelength range, which occurs as a consequence of the vibrational features of the sample that result in the formation of overtones and combination bands that form the spectrum. The relationship between the spectrum and the physicochemical properties of the sample are mathematically modelled using various multivariate regression methods (principal component analysis (PCA) and increment PCA (iPCA) [203], alone [204] or together with partial least-square (PLS) regression analysis [205,206], based on which the compound concentration in the sample is predicted. NIR spectroscopy, in conjunction with multivariate data analysis, is a widely accepted approach for the abovementioned analysis. Quantitative data generated by NIR strongly agree with UHPLC-UV data, confirming the potential of employment of NIR spectroscopy in routine monitoring of cannabis plant material and cannabis resins [189]. Dispersive NIR and FT-NIR methods were developed for quantification of eight different phytocannabinoids (CBDV, \(\Delta^{9}\)-THCV, CBD, CBC, \(\Delta^{8}\)-THC, \(\Delta^{9}\)-THC, CBG and CBN) in ground leaves and infloresances from _C. sativa_[205] and for discriminating illegal and legal cannabis varieties [207]. A similar NIR method demonstrated sensitivity and specificity for CBD quantification in different liquid pharmaceutical products, thus showcasing its potential as a fast method for monitoring of CBD in the production process [206]. Moreover, an NIR method for the growth staging of Cannabis plants was reported as being sensitive to concentrations of phytocannabinoids and volatile substances in the samples, which are also correlated to the plant age, thus justifying the feasibility of the method for growth staging of cannabis [203]. Dispersive NIR using a scanning monochromator [205], FT-NIR spectrometer with integrated Michelson interferometer and a highly sensitive PbS detector [205], FT-NIR spectrometer based on measurement by diffuse reflectance [206], NIR spectrometer with In-Ga-As detector [203], and a handheld NIR with In-Ga-As array detector [189] were so far employed in phytocannabinoid profiling in cannabis ground leaves and infloresances [205], in cannabis seeds [203] and in liquid pharmaceutical products (medium-chain triglyceride and propylene glycol-based formulations) [206]. Two handheld NIR devices (NIR-S-GI and MicroNIR) are used for in-field determination of \(\Delta^{9}\)-THC content in cannabis infloresances and cannabis resins. For this purpose, spectrophotometers with a larger sample analysis window are more appropriate for highly heterogenous samples, such as whole cannabis infloresances [189]. The literature data regarding phytocanabinoids' structural and molecular analysis, to date, is very scarce, lacking band assignation and in-depth structural analysis of the molecules [208; 209; 23] despite the documented ability to provide chemical fingerprinting and qualitative profiling of phytocannabinoids, especially of FTIR in quantification of biological compounds in complex matrices [210].