Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 4 uppsatser.

Voltammetric methods for the determination amphenicol antibiotic chloramphenicol (CAP) and quinolone antibiotic Ofloxacin (OFL) were developed. TTechniques differential pulse voltammetry (DPV) and DC voltammetry (DCV) for determination of both substances at boron doped diamond film electrode (BDDFE) were used. The effect of pH of Britton-Robinson buffer was tested and the stability of the signal with repeated measurements was monitored. Optimal pH 6 was used for determining of CAP by both, DPV and DCV techniques. Media of pH 4 for determining of OFL by DPV and DCV was optimal. Under these conditions linear dependences in the calibration concentration region 1.10 -6 - 1.10-4 mol.l -1 were obtained. The limit of determination for the method for CAP by DPV at 3.10 mol.l , by -6 -1 DCV at 3.10 mol.l and for -6 -1 OFL by DPV at 1.10 mol.l -6 -1 and by DCV at 4.10 mol.l -7 -1 was found. The developed methods were used for the determination of CAP in the drug samples Spersadex comp. and OFL determination in drug samples Zanocin 200. Method for solid phase extraction of OFL from samples of urine with voltammetric detection was developed with limit of determination at 7.10 mol.l . -6 -1

During the 21st century, pollution of environment was steadily increasing. Continuous monitoring of pollutants levels represents important part of effective environment protection. Demands for fast analysis of a large numbers of samples caused introduction of automation to analytical chemistry. Techniques based on flow analysis attracted big attention. They are able to decrease need for manual treatment of samples and decrease analysis duration. The advantage of flow-based analytical devices is also compatibility with several detection systems. Among others, electrochemical detectors are very attractive due to their high sensitivity, good selectivity and possibility of miniaturization. The presented thesis focuses on methods for detection of heavy metal and bacterial contamination. In order to it, electrochemical automatized methods and methods which utilized nanotechnology were developed.

Voltammetric determination of 2-methoxy-5-nitrophenol was studied using DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a carbon film electrode (CFE) and a meniscus modified silver solid amalgam electrode (m-AgSAE). Conditions were found for its determination by DCV and DPV at CFE in Britton - Robinson buffer within concentration range 1.10-4 - 1.10-6 mol.l-1 . Using adsorptive stripping voltammetry (AdSV) m-AgSAE in Britton - Robinson buffer pH 2,0 compound this determined in the concentration range (2 - 10) .10-7 mol.l-1 with a limit of detection 3,6.10-7 mol.l-1 . Using a combination of DPV with solid phase extraction (SPE) for determination of 2-methoxy-5-nitrophenol in river water, limit of detection 6,6.10-8 mol.l-1 was abtained. Using cyclic voltammetry (CV) at m-AgSAE and at CFE mechanism of electrochemical reduction 2-methoxy-5-nitrophenol was proposed.

This diploma thesis is focused on the determination of chloramphenicol by differential pulse voltammetry (DPV), DC voltammetry (DCV), cyclic voltammetry (CV) and adsorptive stripping voltammetry (AdSV) on a meniscus modified silver solid amalgame electrode (m- AgSAE). For the determination of chloramphenicol the optimum conditions were found and under these conditions concentration dependences were measured and then limits of quantification were determined. The influence of pH of BR buffer was tested. For determination of chloramphenicol by DCV pH 7 was chosen as an optimum background and pH 8 was chosen as an optimmum for DPV determination. Under these conditions linear dependences were obtained in the concentration range of 1·10-6 - 1·10-4 mol·l-1 . The limit of detection of chloramphenicol by DCV was 2.3·10-6 mol·l-1 . The limit of detection of chloramphenicol by DPV was 2.1·10-6 mol·l-1 in distilled water, 2.9·10-6 mol·l-1 in river water and 4.2·10-6 mol·l-1 in drinking water. Electrochemical behavior of chloramphenicol was studied by cyclic voltammetry in BR buffer with pH 2, 6, 8, 12 and then mechanism of reduction of chloramphenicol was propose based on available literature. Chloramphenicol was determined in drug Spersadex by DPV in BR buffer with pH 8. The optimal conditions for determining...

The aim of the thesis was to study the possibility of employment of cyclic voltammetry as a detection technique in liquid chromatography. The phenothiazine derivatives (chlorpromazine hydrochloride, diethazine hydrochloride, and thioridazine hydrochloride) were used as model compounds. Firstly, the comparison of two potential detectors (tubular detector and bulk "wall-jet" detector) was accomplished. Only bulk "wal-jet" detector satisfied. Next, the conditions for the separation and detection of studied phenothiazines on RP-select B LiChrospher® 60 (250×4 mm) column with cyclic voltammetry as the detection techniques were optimized. The best separation is achieved in mobile phase consisted from the solution of 0.1 mol dm-3 sodium perchlorate in acetonitrile-water (80:20) mixture. The effect of flow rate of mobile phase and scan rate of polarization of the electrode on the symmetry of chromatographic peak was also followed, and optimal values of 0.5 ml min-1 for flow rate, and of 0.5 V s-1 for scan rate, were found. Under optimized conditions the calibration dependences of studied phenothiazines were measured in the range from 5×10-5 to 1×10-3 mol dm-3 for chlorpromazine, and in the range from 8×10-5 to 1×10-3 mol dm-3 for diethazine and thioridazine. The developed method was applied to...

MicroRNAs are small non-coding RNA molecules with length of about 22 nt. These molecules participate on regulation of gene expression at the post-transcriptional level. They represent the largest group of regulators in the cell and therefore are also involved in all key processes such as proliferation, differentiation or apoptosis. Moreover, they participate in tumor transformation. These small molecules have a great potential to be diagnostic markers or assist in the treatment and prevention of diseases. This research was focused on the development of isolation method using magnetic particles with subsequent electrochemical detection of microRNA. Optimization steps were performed and then the entire method was successfully applied to real samples of HEK293 cells expressing increased levels of miR-124. The developed method proved to be sufficiently specific and applicable to the analysis of microRNA.

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This Ph. D. thesis presents new methods for the determination of selected clinically relevant electrochemically active compounds. The first part deals with development of determination of tumour biomarkers homovanillic acid (HVA) and vanillylmandelic acid (VMA) in human urine with the use of hollow-fibre based liquid-phase microextraction (HF-LPME) and differential pulse voltammetry (DPV) at cathodically pre-treated boron doped diamond electrode (BDDE). Optimum conditions for HF-LPME-DPV of HVA and VMA were as follows: butyl benzoate as supported liquid membrane formed on porous polypropylene hollow-fibre, 0.1 mol L−1 HCl as donor phase and 30 min extraction time. Optimum acceptor phases were 0.1 mol L−1 phosphate buffer of pH 6 with ionic strength set to 0.55 mol L−1 for HVAand 0.1 mol L−1 NaOH for VMA, respectively. HF-LPME-DPV concentration dependencies for HVA and VMAwere linear in the range from 0.4 to 100 µmol L−1 and 0.5 to 100 µmol L−1 . Limits of quantification (LOQ)/detection (LOD) were 1.2/0.4 µmol L−1 for HVA and 1.7/0.5 µmol L−1 for VMA, respectively. The applicability of the developed methods was verified by analysis of human urine. In the second part, voltammetric behaviour of heavy metal poisoning antidote 2,3- dimercapto-1-propane-sulfonic acid (DMPS) was investigated with the use...

Theme of this diploma thesis is usage of electrochemical techniques for study of apoferritin, which is artificially synthetized protein derived from ferritin. Apoferritin has empty cavity which can be used for completion of broad amount of substances. Encapsulation of anticancer drugs can decrease their unwanted side effects such as strong toxicity and therefore increase it’s effectiveness at the tumor site. Substances chosen in this diploma thesis were standard platinum and platinum drugs cisplatin and it’s analogy oxaliplatin. Measurement was performed by electrochemical method differential pulse voltammetry by which was determined encapsulation capacity of apoferritin for chosen anticancer drugs. For determination size and zeta potential of nanoparticles was used colloid analyzator ZetaSizer Nano.