Detection and quantification of the opioid tramadol in urine using surface enhanced Raman scattering

Abstract

There is an on going requirement for the detection and quantification of illicit substances. This is in particular the case for law enforcement where portable screening methods are needed and there has been recent interest in breath tests for a range of narcotics. In this study we first developed surface enhanced Raman scattering (SERS) for the detection of tramadol in water and establish robust and reproducible methods based on silver hydroxylamine colloid. We used 0.5 M NaCl as the aggregating agent, with the pH ∼ 7.0 and SERS data were collected immediately (i.e., the analyte association and colloid aggregation times were zero). The limit of detection was rather high and calculated to be 5 × 10(-4) M which would not be practical in the field. Undeterred we continued with spiking tramadol in artificial urine and found that no aggregating agent or modification of pH was necessary. Indeed aggregation occurred spontaneously due to the complexity of the medium which is rich in multiple salts, which are commonly used for SERS. We estimated the limit of detection in artificial urine to be 2.5 × 10(-6) M which is equivalent to 657.5 ng mL(-1) and very close to the levels typically found in individuals who use tramadol for pain relief. We believe this opens up opportunities for testing SERS in real world samples and this will be an area of future study.

Recent developments in quantitative SERS: Moving towards absolute quantification

“…Finally, the detection of drugs of abuse is important and this has been shown using colloidal-based SERS for the quantification of the controlled substance tramadol [38] and the previously categorised legal high 5,6-methylenedioxy-2aminoindane (MDAI) [39]. SERS has also been used to measure drug overdoses from human saliva [40] as well as drugs of abuse [41,42].…”

Review of SERS Substrates for Chemical Sensing

“…Using artificial neural networks (ANNs), it was demonstrated that SERS could be used for simultaneous analysis of multiple determinands without recourse to lengthy chromatography. Detection of the pain reliever tramadol in artificial urine by SERS using suspensions of Ag NPs was also demonstrated [37]. The limit of detection was 657.5 ng mL −1 , which is close to the levels typically found in individuals who use tramadol for pain relief.…”

“…These include benzene, toluene, ethylbenzene, and xylenes (BTEX) [2,3,4,5]; polycyclic aromatic hydrocarbons (PAHs) [6,7,8,9]; volatile organic compounds (VOCs) such as chlorinated solvents [3,10] and methyl t-butyl ether (MTBE) [3]; heavy metals [11,12,13,14,15]; toxic or radioactive cations/anions [16,17,18,19,20,21,22,23,24]; ionic nutrients [16,25,26,27]; pesticides [28,29,30,31,32]; drugs and pharmaceuticals [33,34,35,36,37,38]; and explosive materials [39,40,41,42,43]. In addition, SERS has been combined with other analytical techniques such as gas chromatography (GC) [44,45], thin layer chromatography (TLC) [46], liquid chromatography (LC) and flow injection analysis (FIA) [47,48,49], and electrochemistry [50,51].…”

Near-infrared (NIR) surface-enhanced Raman spectroscopy (SERS) study of novel functional phenothiazines for potential use in dye sensitized solar cells (DSSC)

“…Likewise a highly sensitive spectroscopic tool offers great potential for drug detection. 35,36 Key to this spectroscopic method is the presence of coinage metal nanoparticles, preferentially gold and silver, 37 but copper is also an applicable SERS substrate. 38,39 Their LSPR, 40 i.e.…”