Andrzej Parczewski

Optimization of solid-phase microextraction conditions for gas chromatographic determination of ethanol and other volatile compounds in blood

A procedure for the determination of acetaldehyde, acetone, methanol, ethanol, 1-propanol and 2-propanol in blood was developed. Separation of analytes was carried out on DB-wax capillary column (l = 30 m, I.D. = 0.32 mm, dF = 0.5 microm) at 40 degrees C, hydrogen was used as a carrier gas (at 30 kPa) and FID as a detector. Quantification was performed with the use of 2-butanol as an internal standard. Headspace solid-phase microextraction was applied as the sample preparation technique. The usefulness of most commercially available fiber coatings was checked and 65 microm Carbowax/DVB proved most effective. Microextraction was carried out from the headspace at 60 degrees C for 10 min. The sample was stirred at 750 rpm. In order to improve the extraction efficiency of analytes, salting-out agents were also applied. Potassium carbonate turned out to be the most efficient. A 1.0-g amount of this salt and 0.1 ml of I.S. were added to 0.5 ml of sample. Validation of the worked-out method was performed. For each analyte, the limits of detection and quantification, linearity, working range, accuracy and precision were determined or tested.

ToF-SIMS application in the visualization and analysis of fingerprints after contact with amphetamine drugs

Time-of-flight secondary ion mass spectrometry was applied in forensic research for characterization, visualization and analysis of fingerprints left after the fingers were contaminated by traces of drugs: amphetamine (AF), methamphetamine (MA) and methylenedioxymethamphetamine (MDMA; ecstasy). Experimental work was carried out using four kinds of bases (steel, aluminium, brass and glass) on which fingerprints were imprinted. The results of our preliminary studies have demonstrated that the ToF-SIMS technique can be a powerful tool in chemical investigations of fingerprints and detection of traces of substances, which do not exist in natural skin extraction, but can be found at the crime scene.

Application of chemometric methods in searching for illicit Leuckart amphetamine sources

A chromatogram of contaminants of illicit amphetamine is referred to as contamination profile. The profile depends on the method and conditions of the drug synthesis. Therefore, it allows to link a drug sample sized by the police to the source of illicit production as well as enables to find out the links between dealers and users. In our study, statistical and chemometric methods were applied. The areas of 15 more informative chromatographic peaks were selected and used as original variables describing the drug samples. The selected peaks formed a profile. As a rule, samples submitted to the police laboratory are classified using correlation coefficient between the corresponding profiles as a measure of similarity. A preliminary classification and the affiliation of a given profile to a class is verified by means of principal component analysis and cluster analysis. Different distances between profiles are used including Euclidean and Pearson ones. The data structure is visualized in two- or three-dimensional spaces of two or three most important principal components. For the purpose of this study, a total of nearly 1000 drug samples were tested. It has been concluded that amphetamine samples may be attributed to one source if the Euclidean distance between the corresponding profiles is less than 1, and the Pearson distance is less than 0.04. This approach proved very effective in identification of drug traffic routes and clandestine laboratories by the police.

Non-linear transformation of factors in the design of experiments

Abstract The application of nonlinear transformations of factors in empirical modelling based on experimental design is proposed. The utility of the polynomial model: R ~ = ΣiB x ~ i + Σi,jBij x ~ i x ~ j + … in empirical modelling may be considerably increased when nonlinear relationships betwee the coded, x ~ , and actual, x, factors are applied, in addition to the linear (conventional) ones. The logarithmic transformation, x ~ i = log qi (ai + bixi), is presented as an example and its application in modelling of interference effects in atomic absorption spectrometry is suggested.

Synthesis of standards of the most important markers of Leuckart p-methoxymethamphetamine (PMMA): Examination of the influence of experimental conditions and a drug diluent on SPE/TLC profiling

The synthesis of characteristic markers of PMMA obtained by Leuckart method was described. The effectiveness of a procedure of SPE/TLC screening profiling of impurities was studied on the basis of selected impurities. The influence of glucose (a drug diluent) on the profile quality was investigated. The intermediate product (characteristic for the Leuckart synthesis) N-formyl-p-methoxymethamphetamine (1) and by-products: N-formyl-p-methoxyamphetamine (2), p-methoxyamphetamine (3), N,N-dimethyl-p-methoxyamphetamine (4), (RS) and (RR/SS) diastereoisomers of bis(1-methyl-2-(4-methoxyphenyl)ethyl)amine (meso-5 and rac-5), (RS) and (RR/SS) diastereoisomers of N-methyl-bis(1-methyl-2-(4-methoxyphenyl)ethyl)amine (meso-6 and rac-6), N-methyl-1,3-bis(4-methoxyphenyl)propane-2-amine (7) were synthesized. The substrate p-methoxyphenylacetone and the impurities 1 and 4 were used in the study of influence of experimental conditions and glucose on the profiling process and results. The experiments were carried out according to a 2(4) factorial design. The proposed criterions of the profile quality are based on matrix presentation of TLC patterns. They take into account the number of spots revealed, differences between R(f) values and intensity of fluorescence, simultaneously.

Empirical modelling of the matrix effect in atomic absorption spectrometry : Determination of Calcium in Presence of Aluminium

Abstract A generalized method of empirical modelling based on experimental design is adapted and applied in an examination of the interfering effect of aluminium on the determination of calcium by atomic absorption spectrometry. Both 2 2 and 3 2 factorials, as well as first-order and second-order models are considered with linearly and logarithmically transformed concentrations of calcium and aluminium. The logarithmic transformations are shown to be more effective in modelling the interfering effect, i.e., fewer experiments are necessary to obtain an adequate mathematical description of the effect than are needed after linear transformations.

The use of empirical mathematical models in the examination of homogeneity of solids

Abstract Experimental design theory is applied: the points to be analyzed on the sample surface are selected so that they form a pattern of rectangles, each of which is treated separately. When the points are arranged in rows and columns, the pattern can be described by factorials of the 2 2 or k 2 type. The results of determining a particular component at each point selected are used to calculate the regression coefficients in an empirical mathematical model; this approximates the dependence of the concentration of the component on the position on the surface within the rectangle. Such models are formulated for each area and the distribution of the component is approximated and finally mapped. Examples based on earlier results are given.

HPLC/DAD Screening Method for Selected Psychotropic Drugs in Blood

The influence of experimental conditions on gradient high-performance liquid chromatography/diode array detector separation and identification of 13 psychotropic drugs belonging to two groups--phenothiazines and tricyclic antidepressants--was examined. The main interaction effects of three experimental factors were determined according to a 2 3 factorial design, and the optimum conditions of analysis were searched for. The degree to which the chromatographic peaks overlap is taken into account in a proposed criterion for separation quality. The screening analysis proposed was tested on whole blood samples spiked with mixtures of the examined drugs. The method was characterized by such validation parameters as relative retention times, absorbance ratios at two wavelengths, detection limits, linearity ranges, and extraction recoveries. The method proved to be a suitable tool for the identification of psychotropic drugs tested for forensic purposes.

Optimum TLC system for identification of phenothiazines and tri- and tetracyclic antidepressants

The TLC separation of twelve drugs from three pharmaceutical groups: phenothiazines and tri and tetracyclic antidepressants is presented. Three kinds of eluents and two types of solid phases (RP 18 and Silica gel 60) were used. The composition of mobile phases was optimized by the Simplex method. In the basic optimization criterion the differences betweenRf values of the spots corresponding to individual drugs were taken into account. An auxiliary criterion was based on the colour of the spots, which were developed with appropriate reagents. The experimental data obtained during optimization were interpreted using a matrix presentation. In the optimal conditions the differences between positions of the spots enable identification of ten of the examined drugs, but two remained unresolved.

Examination of distribution of trace elements in hair, fingernails and toenails as alternative biological materials. Application of chemometric methods

AbstractThe aim of this study was to find correlations between several studied elements and analyzed materials as well as the application and validation of an analytical method to determine trace elements in hair, fingernails and toenails of healthy volunteers (normal concentration). The method developed covers washing, mineralization and ICP-MS determination of 10 elements (Ca, Cd, Co, Cr, Cu, Fe, Mg, Ni, Pb and Zn) in hair and nails. Concentrations of the selected elements in hair, fingernails and toenails were measured for 24 women and 18 men. Furthermore, a chemometric approach (Principal Component Analysis, PCA) was employed to evaluate the correlations between concentrations of the elements in hair and nails and between these materials. Until now PCA has not been frequently applied in handling and interpretation of the results of analysis of biological materials. However, the results of the present investigation show the high potential of PCA in extraction of valuable information from analytical measurements. Additionally, PCA has become a useful tool for visualization of the obtained results. Moreover, the cluster analysis (CA) was used to group the samples according to gender, taking into account two different groups of elements: essential and toxic.