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Various HPLC columns with different length, particle size, sorbent properties, and carbon percentage were applied for the determination of main phenolic compounds present in mixed fruit‐green tea. Separation characteristics were compared, and some of the tested columns were recommended for the developed HPLC assay. Yields of phenolic compounds were evaluated for water and organic‐water mixtures as the extraction media. SPE, using Oasis HLB cartridges, was used for the cleaning up the liquid extracts of fruit‐green tea samples.

HPLC columns with different length, particle size, and chemical properties of sorbent were tested and compared for the application in the development of the universal HPLC assay for determination of phenolic compounds, which could be present in some medicinal plants from the Lamiaceae family (Melissa officinalis, Rosmarinus officinalis, Salvia officinalis, Thymus serpyllum, and Origanum vulgare). More RP‐18 columns have been chosen for the simultaneous separation of all phenolic compounds in the study. The basic chromatographic characteristics were evaluated and the HPLC method using one of the suitable columns was validated for all determined analytes. The recommended separation conditions were applied for phenolic compound monitoring in extracts of plant material. Yields of analytes present in all plant samples were evaluated.

Four different preparation techniques [SPE (Solid phase extraction) in off-line and on-line modes, PSE (Pressurized solvent extraction) and SFE (Supercritical fluid extraction)] were tested for the isolation of some phenolic compounds from Mellissa officinalis. Solid phase extraction methods using the hydrophilic–lipophilic sorbent (OASIS HLB) was used in off-line mode for clean-up of the water extract of medical plants. A generic SPE method was slightly modified, both washing and elution steps were optimized. The contents of methanol for both steps were recommended. Extraction recoveries for all analyzed compounds were about 100% with RSD values in the range 1.1–2.7%. On-line SPE has also been applied for phenolic compounds isolation. Pressurized solvent extraction and SFE are not recommended as preparation techniques suitable for polar phenolics extraction from plant material. Yields of all analytes were low in comparison to liquid extraction and SPE, and the cleanness of chromatograms has also...

A simple HPLC method has been developed for the determination of morphine and its two metabolites, morphine-6-glucuronide and morphine-3-glucuronide in serum. An SPE procedure using OASIS cartridges was recommended for the serum sample preparation. Stationary phases of new generation (Symmetry Shield, XTerra) were tested for the HPLC separation. Mobile phases without any organic modifier and without ion pairs were applied in wide ranges of pH values (Symmetry Shield column pH = 2.5–7.2, XTerra column pH = 2.5–9.5). For higher pH values, very low contents of organic modifier could be used (1, 2%). All analytes were detected by UV detection at 210 nm. Detection limits of the assay were 6.9 ng/ml for morphine, 2.3 ng/ml for M3G and 20.0 ng/ml for M6G.

A very simple solid-phase extraction (SPE) generic assay has been developed for high performance liquid chromatography (HPLC)-DAD or HPLC-UV analysis of morphine and its two metabolites (morphine-3-glucuronide and morphine-6-glucuronide) in serum samples of cancer patients. Solid-phase extraction cartridges with OASIS polymeric hydrophilic–lipophilic sorbent have been applied for SPE off-line procedure. High extraction recoveries have been obtained for simultaneous isolation of all three analytes: 90% for morphine, and 96% and 99% for morphine-3-glucuronide M3G and morphine-6-glucuronide M6G, respectively. The main goal of this work was to optimize loading, washing, and elution steps of the SPE assay, especially pH of loaded sample, volumes of applied wash, and elution solvents with the aim to reduce time for sample preparation and to simplify the SPE procedure. Sorbents of a new generation has also been applied in the HPLC assay (Symmetry Shield RP-8) with mobile phases without any ion-pair ag...

A rapid assay has been developed for on-line SPE-HPLC determination of trimethoprim in milk. SPE precolumns packed with reversed-phase sorbent (RPS C-18) and with restricted access material (ADS C-18) have been tested in the column switching system. Only a simple preparation procedure for the milk sample is required before the direct injection. A Symmetry C-18 analytical column and mobile phase consisting of 100 mM phosphate buffer (pH3), with the addition of an ion-pair agent (PSA) and acetonitrile, have been used for HPLC analysis. UV detection was performed at 229 nm. The detection limit for trimethoprim in milk was 5 ng/mL.

A simple and effective HPLC assay for determination of the main phenolic acids (rosmarinic, caffeic, protocatechuic) that were isolated from medicinal plant Melissa officinalis has been developed. The main goal of this work was to test and evaluate the liquid extraction procedure for plant samples. As the effective extraction media, mixtures of methanol-water and methanol-water (pH 2.5) were chosen. The following extraction conditions were used: time of extraction step 10 minutes, 3 extraction steps, volume of extraction mixture 10 mL, temperature 25°C. The extraction recoveries were: rosmarinic acid 100.7%, caffeic acid 99.9%, protocatechuic acid 96.0%. Yields of phenolic acids extracted from Melissa officinalis grown in Slovakia were: rosmarinic acid 17.03 mg/g (RSD=1.87%), caffeic acid 1.99 mg/g (RSD=3.65%), and protocatechuic acid 0.041 mg/g (RSD=5.75%).

Species of the genus Karwinskia are medicinal woody plants producing secondary metabolites (anthracenones, peroxisomicine A 1 ) with antitumour effects. We investigated the photosynthetic and growth characteristics of Karwinskia parvifolia Zucc. and Karwinskia humboldtiana Rose plants grown at two rates of nitrogen supply. There were significant differences in growth, CO 2 exchange (photosynthesis, respiration), chlorophyll and nitrogen concentration between plants grown at high nitrogen supply (HN) and low nitrogen supply (LN). At HN, the plants of both species grew faster than those cultivated at LN. Rates of photosynthesis, leaf respiration and root respiration, quantum yield, the concentration of chlorophylls (a, b, a + b), specific leaf area, leaf mass ratio and peroxisomicine At concentration were higher in plants grown at HN. The species-specific difference in the daily carbon budget was mainly due to variation in rates of carbon fixation. K. parvifolia responded more strongly to the nitrogen treatment than K. humboldtiana, in terms of growth, as well as with respect to photosynthesis and peroxisomicine A 1 concentration.

Column-switching chromatographic systems using conventional reversed-phase Separon SGX C18 and restricted access media LiChrospher ADS RP-18 precolumns were applied for the determination of propafenone and its main metabolite 5-hydroxypropafenone in human serum samples. The LiChrospher ADS RP-18 precolumn has been found to be more suitable for the sample clean-up. Serum samples were directly injected into the chromatographic system. Proteins and other endogenous compounds were removed by washing with 10% 2-propanol in water and the analytes separated on the Gromsil ODS AB analytical column. The chromatograms were detected at 246 nm. The method validation confirms the suitability of the column-switching system for the quantitation of propafenone and its metabolite. The presented assay shows good linearity with high correlation coefficients (0.992–0.999), high recoveries (96.6±6.1–103.5±5.8) and excellent values of the repeatabilities (1.23–4.5%). The limits of quantitation are 25–40 ng/ml for the injection volume of 50 μl. The complete analysis including the precolumn reconditioning and the sample clean-up requires 26 min, the sample throughput is approximately four samples in an hour.

An HPLC method for the determination of sweet-tasting stevioside (STS) in the leaves of the plant Stevia rebaudiana and in some beverages (e.g. tea, orange juice) was developed. The pre-separation procedure consisted of extraction of STS from the plant material using boiling water and a solid-phase extraction (SPE). Recovery rates of the SPE for the analysed matrices ranged from 92.8% to 97.8% (for concentrations of STS of 105, 210 and 300 μg/ml; Relative Standard Deviation (RSD)≤3.3%). The chromatographic separations were realized using a C18 column, the mobile phase consisting of methanol and water, and with UV detection at 210 nm. The limits of determination of STS were 5 μg/ml for the leaf extracts and the tea sample and 8 μg/ml for the juice sample.

The reaction products of the photocatalytic oxidation of p-cresol were characterized by high performance liquid chromatography. The influence of p-cresol concentration as well as the presence of dioxygen and hydrogen peroxide on the rate of photocatalytic oxidation was studied. The p-cresol concentration in the irradiated systems was determined by spectrophotometric method using α-nitroso-β-naphtol or by the Principal Component Regression method (in the sample with hydrogen peroxide added). The reaction pathway of the photocatalytic oxidation of p-cresol in TiO2 suspension was suggested.

A method is described for the identification and determi—nation of degradation products in mancozeb (manganese-zinc salt of ethylenebisdithiocarbamates). The method is based on the semi-preparative separation of ethylenebisdiizothiocyanate sulphide (EBIS) and ethylenebisthiuramdisulphide (ETD) which were prepar—ed by the iodine oxidation of disodium salt of ethylenebisdithio-carbamate. MS spectra were applied for the identification of EBIS and ETD. Reversed- phase HPLC was used for the determination of EBIS and ETD in methanol extract of mancozeb.

HPLC with DAD (diode array detector) was applied as rapid method for the analytical control of the purity and stability of carboplatin and oxocarboplatin as effective cytostatics of 2nd generation. The stability of carboplatin has been measured in some infusion media (sodium chloride, glucose, sodium citrate) and compared to the cisplatin (cytostatic of 1st generation) stability. In addition ligand-exchange reactions between cisplatin and carboplatin have been studied together with the influence of temperature, pH and the concentrations of reactants. A method was developed for the analysis of clinical samples using solid-phase extraction as a preseparation and preconcentration step. The detection limits were 5 μg/ml serum for cisplatin, 0.16 μg/ml for carboplatin and 0.23 μg/ml for oxo-carboplatin.

Matrix solid-phase dispersion (MSPD) was used for sample preparation of plant material (Melissa officinalis, Lemon Balm) prior to liquid chromatography of rosmarinic, caffeic and protocatechuic acids, phenolic compounds present in this herb. Different MSPD sorbents and various elution agents were tested and the optimal extraction conditions determined with the aim to obtain extraction recoveries greater than 90% for all analytes.

On the basis of standards of identification of substances in the additive system of polyethylene has been performed. Different methods for separation such as adsorption thin-layer chromatography, high-performance liquid chromatography with chemically bounded phases, and gas chromatography have been used. The fir al identification has been made with mass spectrometry. The substances have been extracted from polyethylene with hexane and chloroform.