Erkki Sippola

Quantification of the Amphetamine Content in Seized Street Samples by Raman Spectroscopy

ABSTRACT: A Raman spectroscopy method for determining the drug content of street samples of amphetamine was developed by dissolving samples in an acidic solution containing an internal standard (sodium dihydrogen phosphate). The Raman spectra of the samples were measured with a CDD‐Raman spectrometer. Two Raman quantification methods were used: (1) relative peak heights of characteristic signals of the amphetamine and the internal standard; and (2) multivariate calibration by partial least squares (PLS) based on second derivative of the spectra. For the determination of the peak height ratio, the spectra were baseline corrected and the peak height ratio (hamphetamine at 994 cm−1/hinternal standard at 880 cm−1) was calculated. For the PLS analysis, the wave number interval of 1300–630 cm−1 (348 data points) was chosen. No manual baseline correction was performed, but the spectra were differentiated twice to obtain their second derivatives, which were further analyzed. The Raman results were well in line with validated reference LC results when the Raman samples were analyzed within 2 h after dissolution. The present results clearly show that Raman spectroscopy is a good tool for rapid (acquisition time 1 min) and accurate quantitative analysis of street samples that contain illicit drugs and unknown adulterants and impurities.

Rapid identification and quantitation of compounds with forensic interest using fast liquid chromatography-ion trap mass spectrometry and library searching.

A fast liquid chromatography-electrospray tandem mass spectrometric (LC-ESI-MS-MS) method by using a monolithic column, gradient elution and ion trap mass spectrometer was developed for 14 forensically interesting and chemically different compounds. All compounds were eluted within 2.5 min and the total analysis time was 5 min including stabilisation time required for the next injection. All the compounds, basics, neutrals and acids were efficiently ionised by positive ion ESI. A laboratory library including MS-MS spectra and retention times was developed and tested. Results with 476 standard samples and 50 authentic samples showed that the compounds studied can be unambiguously identified with the library. A quantitative method was developed for the compounds using external calibration. The evaluation process showed good linearity of the method and reasonable repeatability. Limits of detection ranged from 10.0 to 50.0 ng/ml.

Real-time controlled multidimensional gas chromatography with electronic pressure control: application to chlorobiphenyl analysis

Multidimensional gas chromatography was applied to the quantitative determination of planar chlorobiphenyls (PCBs) in commercial PCB mixtures. The instrumental setup is based on real-time controlled column switching in which the heartcuts are elucidated through retention indices calculated by linear extrapolation from the retention times of n-alkanes as reference compounds. Electronic pressure control providing pressure programming was used to adjust the pressure at the injector and at the mid-point of the column tandem.

Statistical modelling of measurement errors in gas chromatographic analyses of blood alcohol content

Headspace gas chromatographic measurements of ethanol content in blood specimens from suspect drunk drivers are routinely carried out in forensic laboratories. In the widely established standard statistical framework, measurement errors in such data are represented by Gaussian distributions for the population of blood specimens at any given level of ethanol content. It is known that the variance of measurement errors increases as a function of the level of ethanol content and the standard statistical approach addresses this issue by replacing the unknown population variances by estimates derived from large sample using a linear regression model. Appropriate statistical analysis of the systematic and random components in the measurement errors is necessary in order to guarantee legally sound security corrections reported to the police authority. Here we address this issue by developing a novel statistical approach that takes into account any potential non-linearity in the relationship between the level of ethanol content and the variability of measurement errors. Our method is based on standard non-parametric kernel techniques for density estimation using a large database of laboratory measurements for blood specimens. Furthermore, we address also the issue of systematic errors in the measurement process by a statistical model that incorporates the sign of the error term in the security correction calculations. Analysis of a set of certified reference materials (CRMs) blood samples demonstrates the importance of explicitly handling the direction of the systematic errors in establishing the statistical uncertainty about the true level of ethanol content. Use of our statistical framework to aid quality control in the laboratory is also discussed.