Bogusław Buszewski

Comparative study of test methods for reversed-phase columns for high-performance liquid chromatography

Column selection in reversed-phase liquid chromatography (RPLC) is still not a straightforward process. A number of tests to characterise and classify RPLC columns have been suggested. Several tests are already applied in laboratory practice, while others are under development. The results of the various tests, however, are not always qualified to describe the properties of columns for RPLC. In this study different tests for RPLC-columns are studied and compared, viz. the Engelhardt, Tanaka, Galushko and Walters tests. The column descriptors hydrophobicity and silanol activity are investigated in particular. The tests are studied using approximately 20 silica, alumina and polymer based C8- and C18-columns. Hydrophobicity data from the tests generally were good and interchangeable between the tests resulting in a column classification that is independent of the applied test. It appears that buffering of the eluent is mandatory for adequate testing of column silanol activity. In contrast with the high-quality hydrophobicity data, the silanol activity results of the various tests differ significantly. As a consequence column classification with respect to silanol activity depends considerably on the applied test method.

Determination of volatile organic compounds in exhaled breath of patients with lung cancer using solid phase microextraction and gas chromatography mass spectrometry

Abstract Background: Analysis of exhaled breath is a promising diagnostic method. Sampling of exhaled breath is non-invasive and can be performed as often as considered desirable. There are indications that the concentration and presence of certain of volatile compounds in exhaled breath of lung cancer patients is different from concentrations in healthy volunteers. This might lead to a future diagnostic test for lung cancer. Methods: Exhaled breath samples from 65 patients with different stages of lung cancer and undergoing different treatment regimes were analysed. Mixed expiratory and indoor air samples were collected. Solid phase microextraction (SPME) with carboxen/polydimethylsiloxane (CAR/PDMS) sorbent was applied. Compounds were analysed by means of gas chromatography (GC) and mass spectrometry (MS). Results: The method we used allowed identification with the spectral library of 103 compounds showing at least 15% higher concentration in exhaled breath than in inhaled air. Among those 103 compounds, 84 were confirmed by determination of the retention time using standards based on the respective pure compound. Approximately, one third of the compounds detected were hydrocarbons. We found aromatic hydrocarbons, alcohols, aldehydes, ketones, esters, ethers, sulfur compounds, nitrogen-containing compounds and halogenated compounds. Acetonitrile and benzene were two of 10 compounds which correlated with smoking behaviour. A comparison of results from cancer patients with those of 31 healthy volunteers revealed differences in the concentration and presence of certain compounds. The sensitivity for detection of lung cancer patients based on eight different compounds not seen in exhaled breath of healthy volunteers was 51% and the specificity was 100%. These eight potential markers for detection of lung cancer are 1-propanol, 2-butanone, 3-butyn-2-ol, benzaldehyde, 2-methyl-pentane, 3-methyl-pentane, n-pentane and n-hexane. Conclusions: SPME is a relatively insensitive method and compounds not observed in exhaled breath may be present at a concentration lower than LOD. The main achievement of the present work is the validated identification of compounds observed in exhaled breath of lung cancer patients. This identification is indispensible for future work on the biochemical sources of these compounds and their metabolic pathways. Clin Chem Lab Med 2009;47:550–60.

Survey and trends in the preparation of chemically bonded silica phases for liquid chromatographic analysis

In order to increase chromatographic selectivity and to extend the analytical capability of reversed phase liquid chromatography (RP HPLC) many investigators have concentrated on the preparation of silica based column packings with chemically bonded phases (CBP). These phases have also been successfully used in sample preparation techniques, mainly in solid phase extraction (SPE). Although alkyl bonded phases (e.g., C2, C8, and C18) are the most widely used packings in RP HPLC and SPE, various specific applications require CBPs with polar functional groups (e.g., -NH2, -NO2, -CN, and/or -OH). The solution of problems with separation of complicated chiral compounds was attempted by applying stationary phases with chiral selectors (e.g., cyclodextrins, Pirkle phases, crown ethers, etc.). On the other hand, packings with pseudo-membrane or liquid crystal properties have been utilized for the separation of various substances of natural origin. Porous silica is commonly used as a support in the preparation of CBPs. Its physico-chemical characteristics, such as: type and structure of siliceous matrix, porosity, type and concentration of silanol groups, as well as surface purity, strongly influence the density and structure of chemically bonded phases. Recognition of these properties is helpful in optimizing separation processes based on RP HPLC elution and/or extraction of substances with polar character.

Past, Present, and Future of Solid Phase Extraction: A Review

Sample preparation of target compounds from biological, pharmaceutical, environmental, and food matrices is one of the most time-consuming steps in analytical procedures. Extraction techniques are dominant, especially those based on the processes running on the phase such as liquid-liquid and/or liquid-solid. Due to the reproducibility of data, precision, relatively low cost of the appropriate analysis, simplicity of the determination, and the possibility of direct combination of those techniques with other methods (both on-line and off-line), they have become the most widespread in routine determinations. Additionally, sample pretreatment procedures have to be more selective, cheap, quick, and environmentally friendly. Selectivity is obtained by using procedures based on immunoaffinity or molecular imprinting. Reduction of costs can be obtained by automation of the extraction procedures (automated SPE) or techniques like column-switching. Reducing at least the time for sample preparation is achieved by introducing miniaturization techniques (multi-well SPE). This review summarizes the current achievements and application of solid phase extraction (SPE). The main aim is to deal with the utilization of different types of sorbents for solid-phase extraction and emphasize the use of new synthesized sorbents as well as to bring together studies on a systematic approach to SPE method development.

The separation of uranium ions by natural and modified diatomite from aqueous solution

In this work the natural and the surfactant modified diatomite has been tested for ability to remove uranium ions from aqueous solutions. Such controlling factors of the adsorption process as initial uranium concentration, pH, contact time and ionic strength have been investigated. Effect of ionic strength of solution has been examined using the solutions of NaCl, Na(2)CO(3) and K(2)SO(4). The pseudo-first order and the pseudo-second order models have been used to analyze the adsorption kinetic results, whereas the Langmuir and the Freundlich isotherms have been used to the equilibrium adsorption data. The effects of the adsorbent modification as well as uranium adsorption on the diatomite surface have been studied using X-ray powder diffraction, scanning electron microscopy and FTIR spectroscopy. The maximum adsorption capacities of the natural and the modified diatomite towards uranium were 25.63 micromol/g and 667.40 micromol/g, respectively. The desorptive solutions of HCl, NaOH, Na(2)CO(3), K(2)SO(4), CaCO(3), humic acid, cool and hot water have been tested to recover uranium from the adsorbent. The highest values of uranium desorption (86%) have been reached using 0.1M HCl.

Analysis of exhaled breath from smokers, passive smokers and non-smokers by solid-phase microextraction gas chromatography/mass spectrometry.

In this study, 38 samples of expired air were collected and analyzed from 20 non-smoking volunteers, four passive smokers and 14 smokers (21 women and 17 men). Measurements were carried out using solid-phase microextraction (SPME) as an isolation and preconcentration technique. The determination and identification were accomplished by gas chromatography coupled with mass spectrometry (GC/MS). Our data showed that ca 32% of all identified compounds in the breath of healthy non-smokers were saturated hydrocarbons. In the breath of smoking and passive smoking volunteers hydrocarbons were predominant, but also present were more exogenous analytes such as furan, acetonitrile and benzene than in the breath of non-smokers. Acetonitrile, furan, 3-methylfuran, 2,5-dimethylfuran, 2-butanone, octane and decane were identified in breath of smoking and passive smoking persons.

The analysis of healthy volunteers' exhaled breath by the use of solid-phase microextraction and GC-MS

We analysed breath and inhaled room air samples from 39 healthy volunteers (28 non-smokers, 8 smokers and 3 ex-smokers) by SPME-GC-MS. Mixed expiratory and indoor air samples were collected in freshly cleaned Tedlar bags. Eighteen millilitres of each sample were transferred into sealed, evacuated glass vials, preconcentrated by solid-phase microextraction (SPME, carboxen/polydimethylsiloxane) and investigated by gas chromatography with mass spectrometric detection (GC-MS). For the unequivocal identification of potential marker compounds, pure calibration mixtures of reference compounds (depending on commercial availability) were prepared to determine the retention time and mass spectra with respect to our analytical setting. Applying the adapted SPME-GC/MS method with limit of detection in the high ppb range (0.05-15.00 ppb), we succeeded in identifying altogether 38 compounds with concentrations in exhaled breath being at least 50% higher than concentration in inhaled air. From these 38 compounds, 31 were identified not only by the spectral library match but also by retention time of standards. A comparison of retention times and spectrum obtained for standards and determined compounds was performed. We found hydrocarbons (isoprene, 2-pentene, 2-methyl-1-pentene, benzene, toluene, p-cymene, limonene, 2,4-dimethylheptane, n-butane), ketones (acetone, hydroxypropanone, methylvinyl ketone), ethers (dimethyl ether, 1,3-dioxolane), esters (ethyl acetate), aldehydes (propanal, hexanal, heptanal, acrolein) and alcohols (ethanol, 2-metoxyethanol, isopropyl alcohol, 2,2,3,3- tetramethylcyclopropanemethanol, 3,4-dimethylcyclohexanol). Proper identification of compounds in different cohorts of patients and volunteers is the base for further investigation of origin, biochemical background and distribution of potential breath biomarkers.

Determination of volatile organic compounds as biomarkers of lung cancer by SPME–GC–TOF/MS and chemometrics

A method for qualitative and quantitative the determination of concentrations volatile organic compounds (VOCs) in human breath samples using solid phase microextraction (SPME) and gas chromatography-time of flight-mass spectrometry (GC-TOF/MS) has been carried out. They are employed for the preconcentration, separation and analysis of biological samples. The technique to rapid determination compounds present in human air, at the level of parts per billion (ppb) is applied. This method was optimized and evaluated. It showed linear correlations ranging from 0.83 to 234.05 ppb, limit of detection in the range of 0.31 to 0.75 ppb and precision, expressed as the RSD, was less then 10.00%. The unique combination of statistical methods allowed reduce the number of compounds to significant ones only and indicate the potential way to find the biomarkers of the lung cancer. Presented an analytical and statistical methods for detection composition of exhaled air could be applied as a potential non-intrusive tool for screening of lung cancer.

Study of toxicity of imidazolium ionic liquids to watercress (Lepidium sativum L.)

AbstractThe sensitivity of Lepidium sativum L. germination to three imidazolium ionic liquids was investigated in solutions and soils artificially contaminated with mixtures of those compounds. In case of aquatic solutions, the toxic character of analyzed compounds is connected with their hydrophobicity. The seedling growth is increasing with the decrease in ionic liquid hydrophobicity. The novelty of those studies is the application of high-performance liquid chromatography, which was used for the determination of ionic liquid quantity absorbed by cress. There was almost linear relationship between decrease in root germination and amount of ionic liquid uptaken by cress. Furthermore, the systematic studies on the influence of total organic carbon content in soil on the toxicity of ionic liquids to cress were performed for the first time. Hazardous effects appeared to be closely connected with organic matter: with the decrease of total organic carbon quantity, the inhibition of plant growth was more significant. Visual effects of ionic liquid toxic activity to garden cress are similar as in the case of nutrient deficit in plants. FigureVisual phytotoxicity effects observed during the test; leaf chromatosis: light green and yellow (up photos), violet (lower photos)

Effect of zeta potential value on bacterial behavior during electrophoretic separation

The aggregation and/or adhesion of bacterial cells is a serious disadvantage of electrophoretic separations. In this study, physicochemical surface characteristics of bacteria were measured to establish their role in bacterial adhesion and aggregation on the basis of electrophoretic behavior of different clinical strains of Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli bacteria. The number and the shape of peaks obtained on the electropherograms were connected with the zeta potential measurements and in‐line microscope observation using specially designed CE fluorescence stereomicroscope setup. These results suggest that the lower the zeta potential, the higher the number of smaller peaks detected. The direct microscopic observation of electrophoretic movement proved the presence of many small aggregates originating from individual or clustered bacterial cells. On the other hand, lower zeta potential was also observed for dead bacterial cells, which suggested that some of the peaks can be attributed to viable cells while the other to the dead ones.