Krystyna Pyrzynska

Porphyrins in analytical chemistry. A review

The porphyrins, naturally occurring macrocyclic compounds, have, in the last 10 years, gained increasing interest in analytical chemistry. This review based on 123 original literature references, mostly published in the 1990s, presents catalytic applications of metalloporphyrins in electroanalysis as electroactive agents in ion selective membranes, as unique reagents in spectrophotometry and as new stationary phases offering unusual resolution in HPLC. The collected data are also presented in four tables.

Functionalized Cellulose Sorbents for Preconcentration of Trace Metals in Environmental Analysis

Regardless the progress in detectability of various instrumentation for trace metal determination, the preconcentration steps are very often needed for the analysis of environmental samples. Among the different techniques that can be used for this purpose, solid-phase extraction using various sorbents has been developed very intensively in recent years. Besides preconcentration, it can also be used for matrix removal necessary in some procedures or for the speciation of trace elements. This review is based on 42 literature references and shows favorable properties of cellulose sorbents for this purpose. Depending on the functional groups attached, the sorbent can be directly used for sorption of target analytes or can be loaded with ligands specifically binding certain species. Applications are reviewed for conventional batch procedures, flow-injection sample processing, and speciation of certain trace elements.

Solid-phase extraction procedure for determination of phenolic acids and some flavonols in honey

The solid-phase extraction procedure (SPE) for isolation and preconcentration of phenolic acids (gallic, p-HBA, p-coumaric, vanillic, caffeic and syringic acid) and some flavonols (rutin, quercetin and kaempferol) from honey samples prior to their determination by HPLC is reported. Different solid sorbents such as Bond Elut octadecyl C(18), Oasis HLB, Strata-X and Amberlite XAD-2 were tested for this purpose. The best results were obtain when aqueous solution of honey (100 mL) was adjusted to pH 2 and passed through the microcolumn containing 2.5 g of Oasis HB followed by washing the sorbent with 50 mL of acidified water (pH 2). The analytes were then eluted with methanol. The proposed method permits the quantification of the studied compounds with the limit of detections ranged from 25 ng kg(-1) to 0.75 microg kg(-1) for p-HBA and quercetin, respectively. The precision of the overall analytical procedure was estimated by measuring the within-day repeatability and the relative standard deviations of the parallel (n=3) results were in the range of 1.9-10.1%. The method was tested for real honey samples from different botanical origins.

Carbon nanotubes as sorbents in the analysis of pesticides

With increasing public concerns for agrochemicals and their potential movement in the ecosystem, very sensitive, selective and precise methods for the analysis of pesticides are needed. Because these substances are present usually at trace levels, the extraction and preconcentration steps are so far essential for their detection. Discoveries of novel nanomaterials with unique properties have significant impact on their use also in extraction techniques. This overview reports the recent application of carbon nanotubes in the analysis of pesticides. The largest numbers of reported applications of carbon nanotubes concern their role as a sorbent materials in solid-phase extraction and microextraction techniques.

Determination of vanadium species in environmental samples

The distribution of vanadium between different oxidation states plays an important role in its environmental chemistry. As its two most commons forms, vanadium(IV) and vanadium(V) have different toxicity, speciation analysis of this element is necessary for environmental and biological samples. This paper presents recent research on the determination of vanadium species. Some important problems concerning stability of vanadium forms and proposed separation techniques are discussed.

Recent advances in solid-phase extraction of platinum and palladium

Increasing platinum concentrations have been detected in environmental samples since the introduction of catalytic converters used in cars. Also the intensive use of platinum-based anti-tumor drugs led to interest in the determination of trace amounts of platinum absorbed by the human body and of the physiological effect of its complexes on living organism. However, detection of Pt and Pd in environmental and biological samples with complex matrices, has to be generally preceded by a preconcentration/separation step. A brief overview of the application of solid sorbents for these procedures based on published data is presented. Attention is also paid to preparation of the samples and detection methods usually used for determination of platinum and palladium.

Application of free radical diphenylpicrylhydrazyl (DPPH) to estimate the antioxidant capacity of food samples

The 2,2-diphenylpicrylhydrazyl (DPPH) assay is widely used in plant biochemistry to evaluate the properties of plant constituents for scavenging free radicals. The method is based on the spectrophotometric measurement of the DPPH concentration change resulting from the reaction with an antioxidant. Several protocols have been followed for this assay using different conditions such as different reaction times, solvents, pH and different compounds used as antioxidant standards. This review shows to what extent the mentioned parameters have the influence on the presented results.

Analysis of selenium species by capillary electrophoresis

The presence of selenium in the form of different species in environmental and biological samples receives an increasing attention due to better understanding of its bioavailability, toxicity and transport mechanism. For many years, gas and liquid chromatography have been extensively explored in speciation analysis of this element. Recently, capillary electrophoresis (CE) has made much progress in this field. This review presents the developments in the application of CE for simultaneous separation and determination of different selenium compounds. Various separation approaches and detection methods as well as pre-concentration techniques are discussed. The speciation performance of CE is illustrated by a number of practically relevant applications.

Analytical Methods for the Determination of Trace Metals in Wine

Trace metal analyses are undertaken to determine trace contamination, their legal limits for export purposes, to monitor the content of certain salts added to some wines during processing, for authenticity purposes, and to determine metal contribution to flavor and wine quality. The most widely applied analytical methods for the determination of metal contents in wine samples are presented. Some problems with sample preparation and validation of the method are also discussed.

Spectrophotometric study of Cd(II), Pb(II), Hg(II) and Zn(II) complexes with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin

The reaction of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) with Cd(II), Pb(II), Hg(II) and Zn(II) was studied spectrophotometrically and kinetics, equilibrium constants as well as photodecomposition of complexes were determined. It was verified that these metal ions with large radius accelerate the incorporation reaction of zinc into TCPP. On the basis of the mechanism and kinetics of this reaction, a sensitive method for the spectrophotometric determination of trace amounts of Zn(II) has been developed. The molar absorptivity of examined Zn-TCPP complex and Sandells sensitivity at 423 nm were 3.5x10(5) M(-1) cm(-1) and 18.3 ng cm(-2). The detection limit for the recommended procedure was 1.4x10(-9) M (0.9 ng ml(-1)) and precision in range 20-100 ng ml(-1) not exceeds 2.7% RSD. The proposed method applied for zinc determination in natural waters and nutritional supplement was compared with AAS results and declared value.