Screening Tablets for DOB Using Surface‐Enhanced Raman Spectroscopy*

Abstract

2,5,-Dimethoxy-4-bromoamphetamine (DOB) is of particular interest among the various "ecstasy" variants because there is an unusually long delay between consumption and effect, which dramatically increases the danger of accidental overdose in users. Screening for DOB in tablets is problematic because it is pharmacologically active at 0.2-3 mg, which is c. 50 times less than 3,4-methylenedioxy-N-methylamphetamine (MDMA) and makes it more difficult to detect in seized tablets using conventional spot tests. The normal Raman spectra of seized DOB tablets are dominated by the bands of the excipient with no evidence of the drug component. Here we report the first use of on-tablet surface-enhanced Raman spectroscopy (SERS) to enhance the signal from a low concentration drug. Raman studies (785-nm excitation) were carried on series of model DOB/lactose tablets (total mass c. 400 mg) containing between 1 mg and 15 microg of DOB and on seized DOB tablets. To generate surface-enhanced spectra, 5 microL of centrifuged silver colloid was dispensed onto the upper surface of the tablets, followed by 5 microL of 1.0 mol/dm(3) NaCl. The probe laser was directed onto the treated area and spectra accumulated for c. 20 sec (10 sec x 2). It was found that the enhancement of the DOB component in the model tablets containing 1 mg DOB/tablet and in the seized tablets tested was so large that their spectra were completely dominated by the vibrational bands of DOB with little or no contribution from the unenhanced lactose excipient. Indeed, the most intense DOB band was visible even in tablets containing just 15 microg of the drug. On-tablet surface-enhanced Raman spectroscopy is a simple method to distinguish between low dose DOB tablets and those with no active constituent. The fact that unique spectra are obtained allows identification of the drug while the lack of sample preparation and short signal accumulation times mean that the entire test can be carried out in <1 min.

Raman spectroscopy – Basic principle, instrumentation and selected applications for the characterization of drugs of abuse

“…20 The modified surface enhanced Raman spectroscopic method was proposed to analyze seized tablets of 2,5-dimethoxy-4-bromoamphetamine (DOB). 21 5 ll of centrifuged silver colloid and 5 ll of 1 mol/dm 3 of sodium chloride solution were dispensed onto upper surface of tablets and 785 nm diode laser was directed onto treated area and spectra were recorded. Method improves the signal from low concentrations of DOB and detection limit was 15 lg.…”

Quantitative SERS Methods

“…Figure 3.3 shows an example where SERS is used to detect the signal from a particularly dangerous 'ecstasy' variant 2,5,-dimethoxy-4-bromoamphetamine (DOB) [25]. This compound is occasionally seized in the same locations where typical ecstasy-type 'designer' amphetamines such as 3,4-methylenedioxy-N-methylamphetamine (MDMA) are distributed and consumed.…”

Classification and Quantitative Analysis of Azithromycin Tablets by Raman Spectroscopy and Chemometrics

“…Raman technique has thus been widely applied to the pharmaceutical industry and the characterization of tablets, such as ecstasy [4], indomethacin [5] and ambroxol [6]. Applications of Raman spectroscopy in tablet analysis has extensively reported, such as solid-state evaluation, polymorphic forms analysis, investigation of coating characteristics, quantitative determination [7,8], and particularly in the identification of pharmaceutical drugs [9] and counterfeits [10][11][12]. Moreover, on-line analysis [13] and process analysis [14] by using Raman spectroscopy were also studied.…”