Paweł Kościelniak

Microwave-assisted extraction of tricyclic antidepressants from human serum followed by high performance liquid chromatography determination.

A microwave-assisted extraction (MAE) method has been developed and optimized for the extraction of six tricyclic antidepressants (TCAD; nordoxepin, nortriptyline, imipramine, amitriptyline, doxepin, dezypramine) from human serum. Optimal parameters of MAE (solvent and extraction temperature) for water solution of these drugs were defined. The microwave-assisted procedure developed was validated by extraction of serum samples at two concentration levels and then successfully applied to the analysis of reference material. Limit of quantification, precision and recovery were found for the studied compounds in the ranges 0.04-0.15 microg/mL, 1.57-4.34% (RSD) and 94-105%, respectively.

Nonlinear calibration by the standard addition method

Abstract The possibility of using the standard addition method (SAM) for calibration in the case of nonlinear relationship between the analytical signal and the analyte concentration is investigated. Analysis of both the precision and the accuracy of SAM has been theoretically carried out assuming that the measurement data are produced with constant random error and then fitted by parabolic function. Several empirical parameters were considered, including, e.g., the number and size of additions, and the curvature degree. Theoretical examinations have been verified by experimental results of some determinations performed by flame atomic absorption and emission spectrometry. Criteria for the selection of linear and nonlinear approximations were discussed. Consequently, the experimental conditions have been suggested allowing the nonlinear calibration by SAM to be applied in practice.

Application of capillary electrophoresis in determination of acid dissociation constant values.

The chemical groups undergoing protonation or deprotonation in solution are described by the acid dissociation constant value, the key parameter for physicochemical characterization of biologically- and pharmacologically-important compounds. Capillary electrophoresis (CE) proved to be suitable technique for its determination: it enables automated and accurate measurements even for minute amount of sample, does not require the information about concentration, and handle both the impure and complex samples. In this review, a number of contributions reporting on the application of CE in pKa prediction has been summarized and critically discussed. The reader will find herein the brief introduction of theory, summary of all works published in the last decade, considerations on the most important innovations and achievements, and the discussion of pKa-related issues as e.g. the role of pKa-shifts in the chiral separation mechanism or the elucidation of migration order reversals observed during CE-mediated separations.

Univariate calibration techniques in flow injection analysis

Abstract A critical view of univariate calibration techniques developed in the flow injection analysis (FIA) is presented. A classification system based on three main calibration categories — interpolative, extrapolative or indicative — is proposed and rationale behind it discussed. Then, the reasons for rather poor applicability of FIA techniques to routine analysis are considered from various points of view. Finally, a novel approach to the FIA calibration is suggested: the integrated calibration technique. It is believed to be more acceptable in analytical practice due to such features (discussed theoretically and shown experimentally) as reliability, simplicity, versatility and procedural similarity to the common batch calibration technique.

Application of capillary electrophoresis to examination of color inkjet printing inks for forensic purposes

In the process of questioned document examination, the discrimination of inkjet printing inks is becoming more necessary due to increasingly frequent counterfeiting of documents printed by inkjet printers. Therefore, a method based on micellar electrophoretic capillary chromatography (MECC) has been developed and applied to analysis of such inks extracted from paper. With the use of an optimized and validated analytical procedure, multielectropherograms of inks taken from various models of printers made by various producers (Hewlett-Packard, Epson, Brother, Lexmark and Canon) were created. It was shown that effective differentiation of individual inks was possible in terms of migration time, order and specific shapes of characteristic peaks. By comparison of recorded UV-Vis spectra, the identification of main dyes was also achievable. The usefulness of the method was confirmed by an intralaboratory test of utility, in which several forged printouts were successfully examined. The obtained results proved that the proposed procedure is a useful tool that could be applied to ink discrimination and group identification of dyes originating from inkjet printing inks. Consequently, the developed method can be applied in the forensic field, including investigation of the authenticity of documents.

DIFFERENTIATION OF MOTOR OILS BY INFRARED SPECTROSCOPY AND ELEMENTAL ANALYSIS FOR CRIMINALISTIC PURPOSES

Abstract Sixteen kinds of mineral, synthetic and semisynthetic motor oils were examined by the FTIR, XRF and AAS methods. It was found that infrared spectroscopy supported by the quantitative elemental analysis provides information on the additives and can be recommended in most cases for differentiation between various oil samples for criminalistic purposes.

An overview of on-line systems using drug metabolizing enzymes integrated into capillary electrophoresis

Enzymatic assays using CE are now among the most noteworthy applications of this analytical technique in pharmacology‐related investigations. Studies of metabolic pathways of new chemical entities mediated by drug metabolizing enzymes are attracting particular attention. Conventional CE‐based enzymatic in vitro assays are generally restricted to the separation of reagents after incubation performed off‐line. EMMA represents an alternative and fully prospective approach, allowing injection, reaction, separation, and detection to be conducted in a single capillary. Such an on‐line system—in contrast to the standard approach—enables automation, miniaturization, and a significant reduction in reagent volumes, resulting in a very robust and cost‐efficient method. Hence, EMMA could be a method of choice for the screening of new drugs, enzymatic inhibitors, and putative drug–drug interactions. This review provides a summary of reports covering the area of EMMA‐based and related methods implemented into in vitro studies of drug metabolizing enzymes. A general description of the EMMA framework, enzyme families, and a concise discussion of the prognosis for the development of this methodology are given as well.

Tyrosinase-based biosensor for determination of bisphenol A in a flow-batch system

A tyrosinase-based amperometric biosensor is proposed for determination of bisphenol A (BPA) in a flow-batch monosegmented sequential injection system. The enzyme was entrapped in a sol-gel TiO2 matrix modified with multi-walled carbon nanotubes (MWCNTs), polycationic polymer poly(diallyldimethylammonium chloride), (PDDA) and Nafion. Morphology of TYR/TiO2/MWCNTs/PDDA/Nafion matrix composite was studied via scanning electron microscopy (SEM). Electrochemical behavior of the developed biosensor towards bisphenol A was examined and analytical characteristics were assessed with respect to linear range, biosensor sensitivity, limit of detection, long term stability, repeatability and reproducibility. Linear range of biosensor response was found between 0.28 and 45.05 µM with high sensitivity of 3263 µA mM(-1) cm(-2) and detection limit 0.066 µM. The approach was successfully employed for determination of BPA in natural samples.

An automatic, vigorous-injection assisted dispersive liquid–liquid microextraction technique for stopped-flow spectrophotometric detection of boron

A novel automatic vigorous-injection assisted dispersive liquid-liquid microextraction procedure based on the use of a modified single-valve sequential injection manifold (SV-SIA) was developed and applied for determination of boron in water samples. The major novelties in the procedure are the achieving of efficient dispersive liquid-liquid microextraction by means of single vigorous-injection (250 µL, 900 µL s(-1)) of the extraction solvent (n-amylacetate) into aqueous phase resulting in the effective dispersive mixing without using dispersive solvent and after self-separation of the phases, as well as forwarding of the extraction phase directly to a Z-flow cell (10 mm) without the use of a holding coil for stopped-flow spectrophotometric detection. The calibration working range was linear up to 2.43 mg L(-1) of boron at 426nm wavelength. The limit of detection, calculated as 3s of a blank test (n=10), was found to be 0.003 mg L(-1), and the relative standard deviation, measured as ten replicable concentrations at 0.41 mg L(-1) of boron was determined to be 5.6%. The validation of the method was tested using certified reference material.

Examination of colour inkjet printing inks by capillary electrophoresis

The possibility of comparing inkjet printing inks by micellar electrokinetic capillary electrophoresis (MECC) with diode array detection was studied. An analytical procedure was designed and successfully applied to discriminate between the electrophoretic profiles of inks (extracted from paper) produced by five well-known manufacturers. The separation process was conducted in a polyimide-coated fused silica capillary (ID 50 μm, 60 cm total/50 cm effective length) with +30 kV high voltage applied. Background electrolyte was used of the following optimum composition: 40 mM sodium borate buffer, 20mM sodium dodecyl sulphate(IV) (SDS) and 10% (v/v) acetonitrile (pH 9.56). The experimental conditions were adjusted in terms of resolution and analysis time. The best results were obtained at 10 and 25°C storage and capillary temperature, respectively, using 25 dots (ø 0.8mm) cut from printouts as the sample and BGE diluted with water (1:99, v/v) as the injecting solution. The MECC separation of main printing ink components by the proposed method showed excellent precision - the RSD value of the migration time calculated for each of the investigated peaks did not exceed 3.3%. The optimized method was applied to group identification and differentiation of: (a) three colours of printing inks, (b) inks from different manufacturers (Hewlett-Packard, Epson, Brother, Lexmark and Canon) and (c) inks from different printer models. In all these cases, inks were successfully differentiated on the basis of position (migration time) and shape of their characteristic peaks.