Human Hair in the Identification of Cocaine Abuse with Cantilever-Enhanced Photoacoustic Spectroscopy and Principal Component Analysis

Abstract

In this study, a novel approach combining different techniques, including Fourier transform infrared (FT-IR) spectroscopy, photoacoustic spectroscopy (PAS) with an interferometric cantilever microphone, and principal component analysis (PCA) along with a proper data preprocessing procedure, have been used in the investigation of hair samples for cocaine abuse. Hair fibers from cocaine-overdose patients have been measured using a simple procedure involving cantilever-enhanced photoacoustic Fourier transform infrared spectroscopy. In addition, a reference group of hair samples from subjects with no cocaine abuse has been measured. We present a first approach to discriminate the cocaine users from the reference group with the photoacoustic method and PCA. With proper data preprocessing methods, the two groups were successfully separated according to their spectra. The results were confirmed with two different classification methods independent of the principal component data analysis.

All-optical dynamic analysis of the photothermal and photoacoustic response of a microcantilever by laser Doppler vibrometry

“…By virtue of their high sensitivity in response to pressure variations at a particular frequency, cantilever beams (CBs) are utilized as vibration or force sensors in various narrowband applications of pressure or motion detection [ 1 , 2 ]. In addition to well-established applications in atomic force microscopy (AFM) [ 3 , 4 ], scanning force microscopy (SFM) [ 5 ], photothermal spectroscopy (PTS) [ 6 ], and biomolecular sensors [ 7 ], CBs have also been explored for enhanced detection of weak acoustic waves [ 8 ], such as photoacoustic signals [ [9] , [10] , [11] ] in cantilever enhanced photoacoustic spectroscopy (CE-PAS) [ [12] , [13] , [14] , [15] , [16] ] which is a performant spectroscopy method [ 17 ] for trace detection of explosives, pollutants [ 18 , 19 ], illicit drug testing [ 20 ] and industrial monitoring [ 21 , 22 ]. It has been reported that CB enhanced microphones can offer a sensitivity that is 100 times higher than a good quality regular microphone [ 23 ].…”