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Biomedical subjects

Marek Trojanowicz

Publications and source records attributed to Marek Trojanowicz.

At least 19 recordsLinked to original sources
PubMed2006

Enantioselective screen-printed amperometric biosensor for the determination of D-amino acids.

D-amino acids are generally considered to be important markers of bacterial contamination of food products. A screen-printed amperometric biosensor for the detection of D-amino acids has been constructed by the immobilization of D-amino acid oxidase on a graphite working electrode of a screen-printed strip modified with Prussian Blue and Nafion layers. Enzyme immobilization was then carried out by cross-linking of a mixture of the enzyme and bovine serum albumin with glutaraldehyde. As a result of the mediator addition and because of the multi-layer construction of the biosensor, including a polymer layer to avoid the interferences, the limit of the detection of the developed biosensor was two orders of magnitude improved in comparison to other screen-printed biosensors, as far as the determination of amino acids is concerned. Additional modification of the graphite electrode with carbon nanotubes led to a significant enhancement of the signal magnitude. A fast linear response of the developed biosensor was subsequently observed in static measurements for D-alanine in the concentration range from 5 to 200 microM. Excellent enantioselectivity towards D-amino acids was discovered. During the experiment, D-amino acids were detected in fruit juices and some milk samples. The complex matrix of natural milk samples had no influence on the response of the biosensor. The results were in good agreement with those obtained by capillary electrophoresis measurements.

Alanine↗
PubMed2006

Separation and determination of perfluorinated carboxylic acids using capillary zone electrophoresis with indirect photometric detection.

Perfluorinated carboxylic acids (PFCAs) belong to anthropogenic fluoroorganic compounds that have been detected in the natural environment and living organisms including humans. A capillary zone electrophoretic method with indirect UV detection using 2,4-dinitrobenzoic acid (2,4-DNBA) as a chromophore probe has been developed for analysis of PFCAs (C6-C12) in water. Optimal analyte resolution and detection sensitivity was obtained with 50 mM Tris solution of pH 9.0 and 50% methanol as a background electrolyte (BGE). The baseline separation of C6-C12 PFCAs was obtained within 20 min with detection limits in the range from 0.6 to 2.4 ppm.

Carboxylic Acids↗
PubMed2006

Determination of amino acids in saliva using capillary electrophoresis with fluorimetric detection.

In the present study a sensitive method for the quantification of main free amino acids in saliva using capillary electrophoresis with laser induced fluorescence detection was developed. As background electrolyte 20 mM borate buffer pH 9.5 was used. Amino acids were separated after derivatization with fluorescein isothiocyanate (FITC) and the conditions for derivatization were optimized. The main amino acids occurring in saliva (Pro, Ser, Gly and Glu) were separated in less than 7 min. The parameters of validation such as linearity of response, precision and detection limits were determined. The detection limits were obtained in the range from 0.1 to 2.4 nM. The developed method was employed for determination of amino acids in real saliva samples.

Amino Acids↗
PubMed2006

Determination of microcystins in environmental samples using capillary electrophoresis.

The applicability of capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) methods for the simultaneous determination of two frequently occurring microcystins (MCs-LR and -YR) and a new variant (MC-YA) in crude extracts of Hungarian bloom samples and cyanobacterial cultures was studied. It was found that the comparison of the results obtained by both CZE and MEKC measurements (due to the differences in their separation mechanisms) for the same sample can guarantee the reliability of the quantitative results. In our work environmental samples like lake waters, water bloom samples, cyanobacterial isolates were analysed. The three microcystins could be directly determined in water bloom samples collected from Hungarian lakes and laboratory culture samples of cyanobacteria.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2005

On-line preconcentration techniques in determination of melatonin and its precursors/metabolites using micellar electrokinetic chromatography.

Determination of melatonin (MT) (N-acetyl-5-methoxytryptamine) and related indole compounds using standard capillary electrophoresis (CE) system with UV detection was investigated. Satisfactory separations of six analytes i.e. l-tryptophan (l-TRP), 5-methoxyindoleacetic acid (5-MIAA), 6-hydroxymelatonin (6-HMT), MT, serotonin (SER) and 5-methoxytryptamine (5-MTRA) were performed employing micellar electrokinetic chromatography (MEKC). The optimal background electrolytes (BGE) used for separations were 20mM tetraborate buffer (pH 9.2) and 20mM phosphate buffer (pH 3.3) when employing techniques with normal and reverse migration of micelles, respectively. Fifty millimolar sodium dodecyl sulfate (SDS) was employed as the pseudostationary phase and voltage of +/-20kV was used throughout the investigation. On-line preconcentration techniques, stacking and sweeping, were applied in order to overcome high detection limits that are a serious drawback of CE with UV detection. A comparison of used techniques, concerning enhancement factors and limits of detection (LOD), is presented. Obtained results show that the use of stacking with reverse migrating micelles (SRMM) as one of preconcentration techniques allows obtaining the lowest estimated LODs for MT at the level of 30ng/mL with injection time of 99s at 0.5psi. Estimated LODs for other analytes in these conditions were, 21, 26 and 100ng/mL for l-TRP, 5-MIAA and 6-HMT, respectively. Signals of 5-MTRA and SER obtainable only with 10s injection allowed reaching estimated LODs of 62.5 and 130ng/mL, respectively. Analysis of spiked, diluted human serum was carried out as a preliminary application illustration of developed procedure.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2005

Liquid chromatography determination of natural dyes in extracts from historical Scottish textiles excavated from peat bogs.

Textiles excavated from Scottish sites belonging now to the collections of the National Museums of Scotland, including seventeenth century textiles from peat bogs in the Scottish Highlands and Islands, were selected for analysis by high performance liquid chromatography with photodiode array detection (PDA HPLC) to detect whether any dyes remained and, if so, to identify their biological sources. Dye components were identified in 36 of the 81 samples analysed. Although it was not possible to identify the exact sources of the dyestuffs because of the wide-spread occurrence of these natural dyes components, the study has shown that textiles previously not thought to have been coloured had detectable traces of dye. Before the historical textiles were analyzed, an improved extraction procedure that combined the routine acid hydrolysis method with one using dimethylformamide (DMF) was applied. The DMF method enabled increased recovery of major flavonoid and anthraquinoid compounds, and very high efficiency of recovery of indigotin even in textiles with no colour visible, thereby complementing the acid hydrolysis method already in use. Extracts from historical thread samples were analysed by PDA HPLC using a reversed-phase gradient system comprising of a C18 column (150 mm x 4.6 mm i.d., 25 +/- 1 degrees C) with water, methanol and o-phosphoric acid at an eluent flow rate of 1.2 ml/min. A preliminary investigation to improve the detection limits further for a selection of natural dyes was made by comparing results from the 4.6mm internal diameter (i.d.) column with a narrow bore C18 column (2.1 mm i.d.). An increase in the detector response was observed for narrow-bore column proving its possibility of enhancement of sensitivity.

Animals↗
PubMed2005

Radiolytic degradation of herbicide 4-chloro-2-methyl phenoxyacetic acid (MCPA) by gamma-radiation for environmental protection.

Reversed-phase HPLC determination of the herbicide MCPA and its products of radiolytic degradation has been optimized. The radiolytic degradation was carried out using gamma-irradiation and was optimized in terms of irradiation dose and pH of irradiated MCPA solution. Decomposition of 100 ppm MCPA in pure solutions required irradiation with a 3 kGy dose. The main products of irradiation in the dose range up to 10-kGy were various phenolic compounds and carboxylic acids. The developed method was applied for treatment of industrial waste from production of MCPA. The 10-kGy dose was needed for decomposition of 500 ppm of MCPA in the industrial waste samples; however, the presence of stoichiometric amount of hydrogen peroxide in the irradiated waste allowed a 50% reduction of the gamma-irradiation dose. Despite complete decomposition of MCPA in the industrial waste, in order to reduce the toxicity of irradiated waste, measured by the Microtox bioluminescence test, higher than a 10 kGy irradiation dose was needed.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed2005

Flow-through microdispenser for interfacing micro-HPLC to Raman and mid-IR spectroscopic detection.

A flow-through microdispenser has been coupled to a micro HPLC separation system and used as a solvent elimination interface for Fourier transform infrared (FTIR) and Raman spectroscopic detection of the separated compounds. Using the microdispenser picoliter sized droplets can be generated and deposited on an appropriate target placed on a computerized x, y-stage. Evaporation of volatile solvent and buffer is rapid and allows analysis of the obtained dry deposits by various techniques. Due to the destruction free character of Raman and FTIR spectroscopy they can be applied sequentially to interrogate the same deposit. In the reported application five phenolic acids typically present in wine have been separated on a C-18 column technique using a mixture of water, methanol and acetic acid as mobile phase. For spectrum acquisition infrared and Raman microscopes have been used. The spectra recorded from the dried deposits of the separated compounds agreed well with the reference spectra of corresponding components.

Chromatography, High Pressure Liquid↗
PubMed2005

Towards the protein phosphatase-based biosensor for microcystin detection.

A colorimetric test for the detection of microcystins based on immobilised protein phosphatase (PP) has been developed. A PP2A produced by molecular engineering has been used and its performance has been compared to those of commercial PP2A and PP1. Covalent immobilisation of the enzyme using glutaraldehyde, encapsulation by sol-gel and entrapment with photocrosslinkable poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) have been compared, the latter method providing the highest immobilisation yields. Screen-printed carbon electrodes (SPEs), Maxisorp microtiter wells and Ultrabind modified polyethersulfone affinity membranes have been used as immobilisation supports. Whilst the highest immobilisation yields were obtained with microtiter wells, the highest operational and storage stabilities were achieved with carbon SPEs and membranes, respectively. The immobilisation of PP by PVA-SbQ provided a means to preserve the enzymatic activity, which decreased at fast rates when the enzyme was kept in solution. The colorimetric test using p-nitrophenyl phosphate has demonstrated that the immobilised enzyme is able to recognise both microcystin variants (MC-LR and MC-RR), although optimisation work should be performed to achieve appropriate limits of detection. With the purpose to develop an electrochemical biosensor, several phosphorylated substrates have been used. Promising results have been achieved with the commercial enzymes and alpha-naphtyl phosphate, p-aminophenol phosphate and catechol monophosphate as enzyme substrates, guaranteeing the viability of the electrochemical approach.

Biosensing Techniques↗
PubMed2005

Electroanalytical flow measurements.

A review based on 94 cited original papers describes recent achievements in application of different electrochemical detection in flow analysis, injection techniques of flow analysis, liquid chromatography and capillary electrophoresis.

Chemistry Techniques, Analytical↗
PubMed2005

Separation of perfluorocarboxylic acids using capillary electrophoresis with UV detection.

A capillary electrophoretic method with UV detection for separation and quantitation of perfluorocarboxylic acids (PFCAs) from C6-PFCA to C12-PFCA has been developed. The optimization of measurement conditions included the choice of the most appropriate type and concentration of buffer in the background electrolyte (BGE), as well as the type and the content of an organic modifier. The optimal separation of investigated PFCAs was achieved with 50 mM phosphate buffer and 40% isopropanol in the BGE using direct UV detection. The optimum wavelength for direct UV detection was optimized at 190 nm. For indirect detection, several chromophores were studied. Five mM 3,5-Dinitrobenzoic acid (3,5-DNBA) in 20 mM phosphate buffer BGE and indirect UV detection at 280 nm gave the optimal detection and separation performance for the investigated PFCAs. The possibility of on-line preconcentration of solutes by stacking has been examined for indirect detection. The detection limits (LODs) determined for direct UV detection ranged from 2 microg/mL for C6-PFCA to 33 microg/mL for C12-PFCA. The LODs obtained for indirect UV detection were comparable to those obtained for direct UV detection.

Carboxylic Acids↗
PubMed2005

Determination of melatonin and its precursors and metabolites using capillary electrophoresis with UV and fluorometric detection.

A micellar electrokinetic chromatography method has been developed for simultaneous determination of melatonin and its precursors and metabolites. A 20 mM borate buffer pH 9.5 with 50 mM SDS served as the electrolyte. Tryptophan, 5-methoxyindoleacetic acid, 6-hydroxymelatonin, melatonin, serotonin, and 5-methoxytryptamine were baseline separated in less than 13 min. The limits of detection for UV detection and fluorometric detection based on native fluorescence of analytes were at the sub-ppm level. The proposed method with UV detection was applied to melatonin content control in pharmaceutical tablets with a precision expressed as RSD (n = 7) = 1.6%. For biological samples extraction with chloroform and ethyl acetate was examined. With ethyl acetate and chloroform recoveries of 87.2% and 82.1% melatonin, respectively, were obtained from plasma samples. The recovery of melatonin from spiked urine samples was 80.0% for ethyl acetate and 82.5% for chloroform. Fluorometric detection provides about two-fold improvement over UV in the detection of melatonin and minor improvements for three other analytes, but is much poorer than UV for tryptophan and 6-hydroxymelatonin in applied conditions.

Animals↗
PubMed2005

Zone electrophoresis separation of perfluorocarboxylic acids on a chip with conductivity detection.

Perfluorinated carboxylic acids (PFCAs), amphiphiles of anthropogenic origin, are spread worldwide throughout the environment. This work deals with their zone electrophoresis (ZE) separation on a chip with coupled columns and integrated conductivity detection. Analogies with the electrophoretic behavior of PFCAs and fatty acids were employed in a search for electrolyte conditions suitable for their separation. ZE separations in the water-ethanol electrolyte systems, based on differences in the ionic mobilities of the anions of PFCAs, provided favorable resolution and detection conditions of the homologues containing up to 10 carbon atoms in the alkyl chain. Concentration limits of detection of 0.3-6.5 micromol/L were attained for PFCAs (loaded by a 900 nL volume sample injection channel of the chip) under these separation conditions. The material of which the chip was made [poly(methylmethacrylate)] restricted its use in investigations of the separations of higher PFCA homologues as it was damaged by ethanolic and/or methanolic background electrolyte solutions required in experiments with these amphiphilic compounds.

Journal Article↗
PubMed2004

Identification of "insoluble" red dyewoods by high performance liquid chromatography-photodiode array detection (HPLC-PDA) fingerprinting.

The paper describes a high performance liquid chromatography-UV/Vis spectrometry detection analytical approach to the identification of some redwood species of historical importance in textile dyeing. The group of extracted dyestuffs considered as "insoluble" because of their non-aqueous or alkaline extraction conditions is present in the wood of the Pterocarpus family and Baphia nitida species. First, the crude extracts of tinctorial and related species and their chromatographic fingerprints were studied. This part of work shows that some species not yet mentioned in the literature have potential dyeing properties. Subsequent experiments performed on the redwood cargo of a 200-year-old archaeological shipwreck allowed identification of the water-logged wood species. Furthermore, the different methods of dyestuff extraction used for dyeing according to traditional recipes and their impact on analytical results were studied. They show that standard recovery obtained by acid hydrolysis of dyestuff from dyed yarns is inadequate. Hence, alternative solvent-based procedures were proposed. The identification of species in textile threads then becomes possible. The applied approach was validated by analysis of dyed reference yarns with some indications of crude material extraction mode. The employed method of analysis seems to be useful for "insoluble" wood species identification in cultural heritage artifacts as well as for phytochemical purposes, despite the fact that very few detected color compounds were chemically identified.

Chromatography, High Pressure Liquid↗
PubMed2004

Monitoring of toxicity during degradation of selected pesticides using ionizing radiation.

The optimization of experimental conditions for radiolytic removal of organic pollutants from water and waste with the use of ionizing radiation via controlling the concentration of target compound(s) requires also monitoring the toxicity changes during the process. Commonly used herbicides 2,4-D and dicamba were shown to increase toxicity measured with the Microtox test at low irradiation doses resulting from formation of more toxic transient products, which can be decomposed at larger doses. The changes of toxicity were examined with respect to dose magnitude and the presence of commonly occurring scavengers of radiation.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2004

Limitations in the analytical use of invertase inhibition for the screening of trace mercury content in environmental samples.

The possibility of screening the mercury(II) content in real environmental samples based on inhibition of the activity of dissolved invertase has been examined. The extent of inhibition was measured with an amperometric glucose biosensor with glucose oxidase immobilized on a membrane. Data concerning the stability and reproducibility of measurements are provided. The effects of heavy metals on the inhibition of invertase, together with that of common anions such as chloride, nitrate and sulfate are reported. The determination of mercury using this procedure has been carried out in samples of natural and waste water samples of various origins already analyzed by ICP-AES, by spiking ppb levels of mercury(II). Differences in the inhibiting effect of the samples and in the recoveries were found and are discussed.

Environmental Pollutants↗