Biomedical subjects

Andrzej Przyjazny

Publications and source records attributed to Andrzej Przyjazny.

8 recordsLinked to original sources

PubMed2004

Application of high-performance liquid chromatography with ultraviolet diode array detection and refractive index detection to the determination of class composition and to the analysis of gasoline.

A method of effective application of normal-phase high-performance liquid chromatography (NP-HPLC) with ultraviolet diode array detection (DAD) and refractive index detection (RID) for the determination of class composition of gasoline and its components, i.e. for the determination of content of alkenes, aromatic and saturated hydrocarbons in gasoline meeting modern quality standards, has been developed. An aminopropyl-bonded silica stationary phase was used along with n-hexane or n-heptane as the mobile phase. A DAD signal integrated over the 207-240 nm range was used to determine alkenes. This eliminates the necessity of separating alkenes from saturates, because the latter do not absorb UV radiation above 200 nm. The content of aromatic hydrocarbons is determined by means of a refractive index detector. Calibration was based on hydrocarbon type composition determined by the fluorescent indicator adsorption method, ASTM D1319. The results obtained by the developed method were found to be consistent with those obtained by fluorescent indicator adsorption or by a multidimensional GC method (PIONA) (ASTM D5443). The method can be applied to gasoline meeting recent quality standards, irrespective of refining technology used in the production of gasoline components, including gasoline with various contents of oxygenates. The developed method cannot be used to determine the hydrocarbon type composition of gasoline that contains as a component the so-called pyrocondensate, i.e. the fraction with a boiling point up to 220 degrees C, obtained through thermal pyrolysis of distillation residues of crude oil or coal and, consequently, does not meet the quality standards. The paper includes the procedure for identification of this type of gasoline.

Chromatography, High Pressure Liquid↗

PubMed2004

Utilization of a sol-gel method for encapsulation of doxorubicin.

The sol-gel pre-doping method was used to encapsulate doxorubicin in silica gels and optimum conditions of preparation of drug-loaded gel were established, ensuring both reproducible and effective results of quantitative encapsulation of doxorubicin and its gradual but complete release. Doxorubicin was encapsulated in polysiloxane polymers using the method based on sol-gel encapsulation without a catalyst, with an acid catalyst (HCl) and a base catalyst (NH3). The time of gelation of the gel loaded with doxorubicin, encapsulation efficiency of the drug and the degree of release of the drug from the gel are all affected by the kind of catalyst (acidic or basic) or its absence at the gel preparation stage, and the temperature of the gelation process. The time of sol gelation when using the NH3 or HCl catalyst was 9 days at 21 degrees C, 2 days at 30 degrees C and 1.5 days at 37 degrees C, while for the gel prepared without a catalyst it was 90 days at 21 degrees C, 75 days at 30 degrees C and 70 days at 37 degrees C. The efficiency of doxorubicin encapsulation was 99.5 +/- 0.5% (w/w) for acid-catalyzed gel, 98.9 +/- 1.01% (w/w) for base-catalyzed gel and 86.4 +/- 11.6% (w/w) for non-catalyzed gel. A 100% (w/w) release of doxorubicin by diffusion through pores was found only in the case of base-catalyzed gel after a 140-h incubation time. For acid-catalyzed gel and non-catalyzed gel, the total amounts of released doxorubicin after 140 h of incubation were 3-5% (w/w) and 9-11% (w/w), respectively. The stability of doxorubicin encapsulated in the three kinds of gel matrices was found to be improved compared to the stability of a free form of the drug in solution.

Buffers↗

PubMed2003

Headspace microdrop analysis--an alternative test method for gasoline diluent and benzene, toluene, ethylbenzene and xylenes in used engine oils.

The primary standard test method used for the determination of gasoline diluent in used engine oils is method D 3525-93 of the American Society for Testing and Materials (ASTM), which involves direct injection of used oil onto a packed GC column and flame ionization detection. Recently, we have utilized a new headspace sampling method: headspace solvent microextraction (HSM), for GC and GC-MS analysis of gasoline diluent in used engine oils. High resolution capillary columns can be used without the necessity for the use of inlet cryogenic cooling or expensive sampling interfaces. This analytical method, which we generically refer to as headspace microdrop analysis yields results comparable to those obtained using the ASTM method, with the added benefit that it allows the quantification of individual volatile diluent components, including benzene, toluene, ethylbenzene and the xylenes.

Benzene↗

PubMed2003

The measurement of conformational stability of proteins adsorbed on siloxanes.

The paper investigates the conformational stability of bovine serum albumin (BSA) and fibrinogen during 24-h incubation in turn with a linear silicone polymer (polydimethylsiloxane (PDMS)), with linear silicone oligomers (hexamethyldisiloxane and octamethyltrisiloxane) and with cyclic silicone oligomers (octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5)). Ten-fold and 100-fold excesses of siloxanes with respect to the proteins were used. Using fluorescence spectroscopy of tryptophan located in the domain of proteins and fluorescence of 8-anilino-1-naphthalenesulfonic acid (1,8-ANS), which interacts with hydrophobic domains of proteins, changes in the tertiary structure of the protein were recorded. The results demonstrated that BSA does not change its native form during 24-h incubation with siloxanes. In contrast, the tertiary structure of fibrinogen was found to be altered by both short-chain linear siloxanes: (hexamethyldisiloxane and octamethyltrisiloxane) and long-chain PDMS. The changes can be observed only at a 100-fold excess of siloxanes with respect to the protein. No conformational changes in fibrinogen exposed to cyclic siloxanes were observed.

Adsorption↗

PubMed2002

Analytical characteristics of the determination of benzene, toluene, ethylbenzene and xylenes in water by headspace solvent microextraction.

Headspace solvent microextraction (HSM) is a novel method of sample preparation for chromatographic analysis. It involves exposing a microdrop of high-boiling point organic solvent extruded from the needle tip of a gas chromatographic syringe to the headspace above a sample. Volatile organic compounds are extracted and concentrated in the microdrop. Next, the microdrop is retracted into the microsyringe and injected directly into the chromatograph. HSM has a number of advantages, including renewable drop (no sample carryover), low cost, simplicity and ease of use, short time of analysis, high sensitivity and low detection limits, good precision, minimal solvent use, and no need for instrument modification. This paper presents analytical characteristics of HSM as applied to the determination of benzene, toluene, ethylbenzene and xylenes in water.

Benzene↗

PubMed2002

Determination of the amount of wash amines and ammonium ion in desulfurization products of process gases and results of related studies.

This paper describes a method for the determination of the so-called wash amines and their degradation products, including ammonium ions, in process liquids and wastewater generated during the desulfurization of hydrogen sulfide gas in the process of crude oil refining and also reports the results of related studies. Ion-exchange liquid chromatography employing an inexpensive cation-exchange HPLC column and refractometric detection was used. The results obtained were compared with those obtained by potentiometric titration. Analytical characteristics and a description of the developed procedure are provided. Examples of the results of routine determinations of amines, their degradation products and ammonium ions in process liquids and wastewater are given.

Amines↗

PubMed2002

Evaluation of optical changes of three types of lenses: hard PMMA, hydrogel, and heparin surface modified hard lenses effected by silicone oil, used clinically as a substitute of the vitreous body.

The objective of these investigations was an in vitro evaluation whether silicone oil OXANE of viscosity 5700 cSt clinically used in eye surgery as a substitute of the vitreous body, being in contact with an artificial polymer lens used as an implant of human lens, causes the changes in its optical properties. The paper presents the results of spectral analysis of transmission of visible (VIS) radiation of three types of artificial lenses: hard PMMA, hydrogel, heparin surface modified (HSM) hard PMMA, and the same lenses damaged by YAG laser radiation with an energy increasing from 1.7 mJ to 3.7 mJ, exposed to clinically applied silicone oil. The studies were carried out, in two-week intervals, over a period of 20 weeks. Hard PMMA and HSM lenses were found not to have changed their optical properties after 20 weeks of exposure to silicone oil. The measured transmittance values were within the range of instrumental error (+/- 1%). Optical properties of hydrogel lenses exposed to silicone oils deteriorated with exposure and after 20-week exposure to silicone oil the average transmittance value decreased by about 18%, reaching its final value of 67.08 +/- 2.37% (RSD = 5.56%). A minimal decrease of the initial transmittance values was observed only for the lenses exposed to laser radiation of highest energy (3.7 mJ). After completed exposure to silicone oil, two kinds of lenses were found to have a slightly improved transmittance: hard PMMA lenses by about 4% and HSM lenses by about 2%. On the other hand, in case of hydrogel lenses the deterioration of optical properties to the extent comparable to that of hydrogel lenses not damaged by laser radiation was observed.

Heparin↗

PubMedDate not supplied

In vitro measurement of conformational stability of fibrinogen adsorbed on siloxane.

The paper describes the effect of 10-, 50-, 100-, 200-, 300-, 400-, and 500-fold excess of low-molecular weight, linear, hexamethyldisiloxane (L(2)) and cyclic hexamethylcyclotrisiloxane (D(3)) with respect to fibrinogen (Fbg) on the conformational stability of Fbg during a 60-h incubation at 37 degrees C. This study used SPE/HPLC/UV and fluorescence of a tryptophan located in the domain of Fbg and fluorescence of 1,1'-bis(4-anilino)naphthalene-5,5'-disulfonic acid (ANS) spectroscopy. The fact that the decrease in fluorescence intensity of siloxane-treated Fbg was accompanied by red shift in the maximum wavelength indicated that denaturation of Fbg had taken place. The differences (the decrease in peak height and the shift in retention time) in chromatograms between control Fbg and siloxane-treated Fbg indicated the adsorption process of Fbg on the surface of siloxanes. Incubating hexamethyldisiloxane with Fbg at L(2)-to-Fbg ratios >300 for 20 h yielded white and mould-like precipitates of Fbg. The same phenomenon demonstrating massive denaturation and aggregation was observed for a greater than 500-fold excess of D(3) with respect to Fbg after 20 h of incubation.

Adsorption↗