Surface enhanced raman spectroscopy as a novel analytical tool in toxicological analysis of heroin and metabolites in saliva

Heroin can be detected and quantified by certain analytical methods; however, forensic professionals and criminal laboratories study for cheaper and faster detection tools. Surface-enhanced Raman spectroscopy rise as a possible alternative tool with its widening application spectra. There are few studies regarding Raman and SERS spectra of heroin and its metabolites, which are unfortunately controversial. In this study we compared five different surfaces in order to find out more efficient Raman-active substrate for opiate detection and rapid quantification of heroin and its metabolites in saliva. Morphine standard material was used to determine the most suitable Raman-active surface for SERS analysis of opiates. For this purpose, thin layer chromatography (TLC) plate, silver nano surface (AgNS), gold nanoparticle nanocellulose (AuNP/Nanocellulose), gold nanoparticle polyaniline (AuNP/Polyaniline) and gold nano-rod (AuNR) surfaces were compared. Separate calibration curves were generated for standart materials and saliva samples containing heroin and its metabolites (morphine, morphine-3-ß-glucuronide and 6-monoacetyl morphine). Repeated SERS analysis of saliva samples containing different concentrations of heroin and metabolites was performed using a 785 nm laser source Raman microscope, AuNR surface and silver nanoparticle (AgNP) as signal enhancer. The results showed that heroin and its metabolites can be detected and measured in saliva samples using a SERS-based system. This study demonstrated that the synergistic effect of AuNR surface and AgNP signal enhancer increases numbers of identifiable bands and their intensities in the SERS spectrum. It was determined that the quantitative analysis of heroin and its metabolites could be achieved very close to the concentrations spiked in blank saliva samples by using the developed method and the formula created by the concentration-intensity match point during the calibration. In this respect, a fast, accurate and very advantageous method in terms of cost-effectivity has been developed to detect and measure heroin and its metabolites in saliva sample.