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.

Titania sol-gel-derived tyrosinase-based amperometric biosensor for determination of phenolic compounds in water samples. Examination of interference effects.

For detection of phenolic compounds in environmental water samples we propose an amperometric biosensor based on tyrosinase immobilized in titania sol-gel. The analytical characteristics toward catechol, p-cresol, phenol, p-chlorophenol, and p-methylcatechol were determined. The linear range for catechol determination was 2.2 x 10(-7)-1.3 x 10(-5) mol L(-1) with a limit of detection of 9 x 10(-8) mol L(-1) and sensitivity 2.0 x 10(3) mA mol(-1) L. The influence of sample matrix components on the electrode response was studied according to Plackett-Burman experimental design. The potential interferents Mg(2+), Ca(2+), HCO3(-), SO4(2-), and Cl(-), which are usually encountered in waters, were taken into account in the examination. Cu(2+) was also taken into account, because CuSO(4) is sometimes added to a water sample, as a preservative, before determination of phenolic compounds. It was found that among the ions tested only Mg(2+) and Ca(2+) did not directly affect the electrode response. The developed biosensor was used for determination of catechol in spring and surface water samples using the standard addition method.

The effect of re-annealing on the distribution of refractive index in a windscreen and a windowpane classification of glass samples.

Tiny glass fragments of two typical objects being of interest in forensic investigations: car windscreen and windowpane were examined from the point of view of their importance as crime evidence. Both examined objects were made from float glass and were toughened. The present paper concerns examination of refractive index distribution across the objects under investigation before and after the glass fragments were annealed according to previously chosen procedure. The annealing procedure was carried out in order to increase discrimination power of refractive index (RI). The following conclusions can be drawn from the results obtained. For both examined objects the mean RI was significantly higher after annealing and, at the same time, standard deviations in RI were smaller. The distributions of RI for both examined objects appeared not to be normal; the deviations from normality were observed at both sides of RI distributions. It was found that the difference in the values DeltaRI (difference between mean values of RI after annealing and before annealing) for both examined object was not significant and thus it would be not a good parameter to differentiate between two heat strengthen objects. The attempt to classify 181 glass samples on the basis of theirs RI and DeltaRI was performed. Increased discrimination of glass samples was observed.

Application of false discovery rate procedure to pairwise comparisons of refractive index of glass fragments.

This study was undertaken to apply a new method of controlling type I error when performing pairwise comparisons. The Benjamini and Hochberg false discovery rate (FDR) controlling procedures have proved to be very powerful tools in solving many practical problems but have not yet been applied to pairwise comparisons of refractive index of glass samples. Students t-test and Welch test (unequal variance Student's t-test) were applied to all possible pairwise comparisons. The comparisons were made on the basis of refractive index values of 72 glass fragments from different car windows and 69 different fragments from one windscreen. The type I error was controlled by the use of Benjamini and Hochberg false discovery rate (FDR) controlling procedure. To illustrate the importance of controlling type I error when using pairwise comparisons, results of pairwise comparisons with the FDR controlling procedure were compared to those comparisons made without any controlling procedure. Significantly fewer false negative results (false rejection of H0) were found during the use of FDR procedure in the comparison of refractive indices from the same windscreen than when comparing without controlling type I error. The results of application of FDR method were also compared to the results of other post-hoc tests, such as Tukey HSD test and Bonfferoni test. The FDR method has higher power than Bonferroni method and Tukey HSD method and control errors better than comparing without controlling type I error. The method of choice, for pairwise comparison of glass fragments on the basis of refractive index is Welch test with FDR adjustment. The method gave type I errors at level about 5.3% and type II error at about 3.7%.

Basic and neutral route specific impurities in MDMA prepared by different synthesis methods. Comparison of impurity profiles.

In this work, the neutral and basic impurities found in the precipitate of MDMA(*)HCl are presented. MDMA.HCl was prepared by the most popular synthesis methods used in clandestine manufacture, i.e. safrole bromination, Leuckart method and reductive amination with various reducing agents: Al/Hg, NaBH(4), NaBH(3)CN. 3,4-Methylenedioxyphenyl-2-propanone (MDP-2-P), the starting material in Leuckart reaction and reductive amination, was prepared by two different synthesis methods, i.e. by isosafrole oxidation and MDP-2-nitropropene reduction. The extraction of impurities was performed under alkaline and neutral conditions. Impurity profiles were obtained using GC/MS. Each synthesis method is characterised by its own route specific impurities. The influence of pH on the extraction of synthesis markers from 3,4-methylenedioxymethamphetamine (MDMA) samples is discussed and comparison of the profiles of basic and neutral impurities is presented.

Determination of synthesis method of ecstasy based on the basic impurities.

MDMA was prepared by five different synthesis routes, i.e. by dissolving metal reduction (Al/Hg), cyanoborohydride reduction (NaBH(3)CN), borohydride reduction in low temperature (NaBH(4)), Leuckart reaction and safrole bromination. MDP-2-P was prepared by two different synthesis methods, i.e. by isosafrole oxidation and MDP-2-nitropropene reduction. Each of the synthesis routes was repeated three times in order to establish variation in qualitative composition of route specific impurities between different batches. The analysis of impurities in MDP-2-nitropropene, MDP-2-P, bromosafrole and MDMA was performed with GC-MS. GC/MS was used also in the analysis of impurities in starting materials: safrole, isosafrole and piperonal. As a result of our study the way of determination of MDMA synthesis route determination based on qualitative composition of impurities is proposed.

Determination of synthesis route of 1-(3,4-methylenedioxyphenyl)-2-propanone (MDP-2-P) based on impurity profiles of MDMA.

In our study 1-(3,4-methylenedioxyphenyl)-2-propanone (MDP-2-P or PMK) was prepared by two different routes, i.e. by oxidizing isosafrole in an acid medium and by 1-(3,4-methylenedioxyphenyl)-2-nitropropene reduction. The final product-MDP-2-P was subjected to GC/MS analysis. The intermediates and reaction by-products were identified and the 'route specific' impurities were established. The following impurities are the markers of the greatest importance: 1-(3,4-methylenedioxyphenyl)-1-propanone (compound 10, Table 2), 1-methoxy-1-(3,4-methylenedioxyphenyl)-2-propanone (compound 11, Table 2) and 2,2,4-trimethyl-5-(3,4-methylenedioxyphenyl)-[1,3]dioxolane (compound 13, Table 2) (the 'oxidising isosafrole route') and N-cyclohexylacetamide (compound 3, Table 1), 3-methyl-6,7-methylenedioxyisoquinoline-1,4-dione (compound 15, Table 1) (the 'MDP-2-nitropropene reduction route'). Subsequently, MDMA was prepared by reductive amination of MDP-2-P using NaBH4 as reducing agent (so-called 'cool method'). Impurities were extracted with n-heptane under alkaline conditions. The impurity profiles were obtained by means of GC/MS, some reaction by-products were identified by means of the EI mass spectra including low energy EI mass spectra and 'route specific' impurities were established. 4-Methyl-5-(3,4-methylenedioxyphenyl)-[1,3]dioxolan-2-one (compound 22, Table 2), N-methyl-2-methoxy-1-methyl-2-(3,4-methylenedioxyphenyl)-ethaneamine (compound 18, Table 2), 3-methyl-6,7-methylenedioxyisoquinoline-1,4-dione (compound 15, Table 1) and N-cyclohexyloacetamide (compound 3, Table 1) were found to be the synthesis markers of greatest importance.

Profiling of impurities in p-methoxymethamphetamine (PMMA) by means of SPE/TLC method. Examination of the influence of experimental conditions according to 2(4) factorial.

In the present paper profiling of impurities in p-methoxymethamphetamine (PMMA) by means of SPE/TLC is reported. PMMA was synthesised by Leuckart procedure. The influence of experimental conditions on the profile quality was investigated. The experiments were carried out according to a 2(4) factorial. The proposed characteristics of the profile quality (optimisation criterions) are based on a matrix presentation of TLC patterns. They take into account, simultaneously, the number of spots revealed, differences between R(f) values and intensity of fluorescence.

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.

Determination of two metals from a single potentiometric titration curve The application of two indicator electrodes.

The advantages of applying two indicator electrodes in complexometric potentiometric multicomponent titration are shown by means of simulated titration curves. Two measurement arrangements have been considered, one in which the indicator electrodes are directly connected to a voltmeter and the other in which the electrodes are connected to the voltmeter through a summing operational amplifier. They have been compared with the conventional arrangement of a single indicator electrode and a reference electrode. The influence of the stability constants of the complexes in solution and of the electrode parameters on the shape of titration curves has been examined. It is shown that the use of two indicator electrodes may significantly increase the applicability of multicomponent potentiometric titrations.

Signal processing with a summing operational amplifier in multicomponent potentiometric titrations.

It has been proved that application of two indicator electrodes connected to the ordinary titration apparatus through an auxiliary electronic device (a summing operational amplifier) significantly extends the scope of multicomponent potentiometric titrations in which the analytes are determined simultaneously from a single titration curve. For each analyte there is a corresponding potential jump on the titration curve. By application of the proposed auxiliary device, the sum of the electrode potentials is measured. The device also enables the relative sizes of the potential jumps at the end-points on the titration curve to be varied. The advantages of the proposed signal processing are exemplified by complexometric potentiometric titrations of Fe(III) and Cu(II) in mixtures, with a platinum electrode and a copper ion-selective electrode as the indicator electrodes.

Factorial analysis of matrix effects in ICP-OES and AAS Determination of Ta and Ni IN Au.

In measuring systems in which the signal is linearly related both to the component of interest and to matrix components, 2(n) factorial analysis is a convenient tool for applying matrix corrections. In general, the linearity condition is satisfactorily fulfilled if the matrix influences are not very large, but generally the signal is not linearly related to the analyte concentration. k(n) (k > 2) factorial analysis can then be applied, but it needs extensive calibration to determine all the regression coefficients. When the non-linearity is not too large (as in atomic-absorption spectrophotometry), a more convenient method is to use the calibration curve or the instrumental curve-correction facility to obtain a linearized variable to which 2(n) factorial analysis is then applied. It is shown that the systematic deviation introduced often remains negligible if only the upper part of the calibration curves is used.

Photometric complex-formation titration of submicromolar amounts of zirconium.

Even in strongly acidic solution Zr(IV) forms polynuclear hydroxide complexes. In these compounds tetrameric units play a dominant role. When the Zr atoms in these units are interconnected through double OH-bridges (olated bonds) quantitative formation of Zr-EDTA is possible at room temperature. When the double OH-bridges are replaced by single oxygen-atom bridges (oxolated bonds) the units are less reactive. The oxolated tetramers are still capable of reacting quantitatively with EDTA if heated to about 100 degrees ; higher oxolated polymers are not. When these higher polymers are formed during the initial adjustment of conditions for a titration, large errors will be observed. By suitable treatment of the solutions oxolation can be restricted sufficiently to permit titrations with an error of less than 1%. Semi-Xylenol Orange has been found to be a suitable indicator for direct titrations; back-titrations are performed with Bi(3+), with PAR as indicator.