Piotr Konieczka

Estimating uncertainty in analytical procedures based on chromatographic techniques.

Chromatographic techniques are very frequently used in analytical procedures for the separation, determination and identification of a wide spectrum of analytes present in samples with complex and sometimes variable matrices. However, the estimation of uncertainty of the final results does not include the uncertainties associated with the actual chromatographic process. In effect, such results cannot always be treated as a reliable source of analytical information. In this paper we present the basic terms, sources of uncertainty, and methods of calculating the combined uncertainty that any presentation of final determinations should include.

Quality Assurance and Quality Control in the Analytical Chemical Laboratory: A Practical Approach

Nowe opracowanie ksiązkowe z zakresu QA/QC to praktyczny podrecznik zarowno dla studentow jak i pracownikow laboratoriow. Opisano systemu jakości wynikow pomiarow analitycznych i poszczegolnych jego skladnikow: spojności pomiarowej, niepewności pomiaru, walidacji procedury analitycznej, materialow odniesienia i badan miedzylaboratoryjnych. Opisano i przedstawiono narzedzia statystyczne sluzące do obliczania parametrow walidacyjnych, szacowania niepewności, opracowywania wynikow badan miedzylaboratoryjnych, stosowania materialow odniesienia. Zamieszczono przyklady dotyczące: tworzenia budzetu niepewności i szacowania niepewności; odrzucania wynikow obarczonych bledami grubymi; obliczania wartości bledow systematycznych; obliczania precyzji (powtarzalnośc, precyzja pośrednia); porownywania precyzji serii wynikow; porownywania wartości wyniku z wartością odniesienia; porownywania wartości wynikow uzyskanych roznymi metodami; liczenia i dokumentowania liniowości; obliczanie wartości LOD i LOQ; określania zakresu pomiarowego; wyznaczania parametrow walidacyjnych. Wszystkie z przykladow zaopatrzone zostaly w skonstruowane arkusze kalkulacyjne ulatwiające obliczenia.

Phenolic composition and antioxidant properties of polish blue-berried honeysuckle genotypes by HPLC-DAD-MS, HPLC postcolumn derivatization with ABTS or FC, and TLC with DPPH visualization

In this study, different Polish cultivars of blue-berried honeysuckles (Lonicera caerulea L.), wild and bog bilberry, were analyzed for bioactive compounds. The chemical properties verified included composition of anthocyanins and other polyphenols, antioxidant activity, and profiles of antioxidants by HPLC postcolumn derivatization or TLC. The antioxidant activities of different blue-berried honeysuckle cultivars were similar to that of wild-growing bilberries (ranging from 170 to 417 μmol TE/g dm in ABTS and from 93 to 166 μmol TE/g dm in DPPH and Folin-Ciocalteu tests). The major anthocyanin in the blue-berried honeysuckle was cyanidin-3-glucoside, which constituted 84-92% of the total anthocyanins. The TLC and HPLC postcolumn antioxidant profiles indicated that anthocyanins are the major antioxidants in all berries studied. Wild berries and the cultivars of the blue-berried honeysuckles are also a similar source of such minerals as K, Mg, and Ca.

Use of Brassica Plants in the Phytoremediation and Biofumigation Processes

In recent decades, serious contamination of soils by heavy metals has been reported. It is therefore a matter of urgency to develop a new and efficient technology for removing contaminants from soil. Another aspect to this problem is that environmental pollution decreases the biological quality of soil, which is why pesticides and fertilizers are being used in ever-larger quantities. The environmentally friendly solutions to these problems are phytoremediation, which is a technology that cleanses the soil of heavy metals, and biofumigation, a process that helps to protect crops using natural plant compounds. So far, these methods have only been used separately; however, research on a technology that combines them both using white cabbage has been carried out.

The Role of and the Place of Method Validation in the Quality Assurance and Quality Control (QA/QC) System

One of the main developmental trends in chemical analytics is the determination of analytes at ever decreasing detection levels in samples with increasingly complex matrices. This is an extremely difficult and complicated task therefore it poses a great challenge to analytical chemists, and it requires that appropriate attention be paid to the Quality Assurance and Quality Control (QA/QC) of the obtained measurements. In this article QA/QC system is described. Following topics are discussed: (1) measurement uncertainty, (2) traceability of analytical results, (3) reference materials, (4) interlaboratory comparisons and (5) method validation. The problems and challenges during method validation process are presented.

The dose‐dependent influence of zinc and cadmium contamination of soil on their uptake and glucosinolate content in white cabbage (Brassica oleracea var. capitata f. alba)

The relationship between the ability to accumulate heavy metals (represented by Cd and Zn) and to synthesize bioactive compounds (represented by glucosinolates [GLS]) was investigated in two cabbage cultivars. Plants were grown in the greenhouse of a phytotron under controlled conditions in soils spiked with two different Zn or Cd concentrations. The measurements of Cd and Zn contents in soil and cabbage (leaf) samples were performed by atomic absorption spectroscopy, whereas GLS levels in cabbage were determined by high-performance liquid chromatography. The ranges of metal contents in soil were 80 to 450 mg/kg dry weight for Zn and 0.3 to 30 mg/kg dry weight for Cd, whereas the levels of accumulated Zn and Cd in cabbage amounted to 15 to 130 and 0.02 to 3 mg/kg dry weight, respectively. After initial symptoms of toxicity, during a later stage of growth, the plants exhibited very good tolerance to both metals. Enhanced biosynthesis of GLS was observed in a dose-dependent manner following exposure to the heavy metals. The GLS content in Zn-exposed cabbage rose from 3.2 to 12 µmol/g dry weight, and the corresponding values for Cd-treated plants were 3.5 to 10 µmol/g dry weight. Thus, the increased soil contamination by metals caused greater accumulation in cabbage, as well as stimulation of GLS biosynthesis. The results obtained point to the high phytoremediation and biofumigation potential of white cabbage.

The Properties, Functions, and Use of Selenium Compounds in Living Organisms

Selenium occurs in the environment in inorganic and organic compounds. For many years it was regarded as a toxic element, causing numerous illnesses and diseases. But research in the past 50 years has revealed a “bright side” to this element, especially as a component of selenoproteins, selenium makes a significant contribution to the health of humans and animals. The selenium content in an organism depends on its concentration and bioavailability in the soil, and the differences between its deficiency, appropriate intake, and excess are very slight. This article gathers information from the literature on: • the consequences of a deficiency and an excess of selenium in the body, as well as the health-promoting mechanisms of selenium, including the functions of selenoproteins • the uptake and transformation of selenium compounds by plants, because of the fact that selenium is better assimilated from plant food and also the classification of plants with respect to their ability to take up selenium from the soil and to accumulate it.

Development of Techniques of Generation of Gaseous Standard Mixtures

Abstract Various reference materials are increasingly used in analytical work. This is directly related to the assessment and quality control of results of measurements in order to make them a reliable source of analytical information. Reference materials are an indispensable tool in the development and validation of new analytical procedures. They also are often used in interlaboratory studies. The use of reference materials allows maintaining traceability. More and more reference materials containing analytes in solid and liquid matrices are becoming available. However, gaseous reference materials are much less available. This is because of the lack of stability with this type of reference materials. Consequently, not all techniques of the generation of gaseous standard mixtures can be used to prepare appropriate matrix-free gaseous reference materials. This article discusses the following topics: (1) classification of known techniques of generation of gaseous standard mixtures; and (2) review of most commonly used techniques, including schematic diagrams of the apparatus. The article also includes the information on a new approach to the problem of generation of gaseous standard mixtures whereby the analyte is generated in the process of thermal decomposition of suitable immobilized compounds formed by chemical modification of an appropriate solid support.

The influence of selenium addition during germination of Brassica seeds on health-promoting potential of sprouts

Abstract The correlation among selenium uptake, the content of bioactive compounds in sprouts, and biological activities triggered in cultured human cells by sprout extracts was investigated. Seeds of Brassica crops and rye were treated with SeO2 water solution. The selenium levels in sprouts increased from 1.0–4.1 to 53.3–382 μg/g dw with no influence on plant physiology according to the indices used. Neither the composition of glucosinolates (GL) in Brassica sprouts nor the myrosinase activity nor the composition of GL breakdown lipophilic products were significantly affected. In all Brassica sprouts, conversion to health-promoting isothiocyanates (ITC) and indoles corresponded to only 1% of total GLs. Low ITC concentration may explain observed lack of induction of glutathione S-transferases (GST) and quinone oxidoreductase (NQO) detoxifying enzymes in HT29 cells exposed to sprout extracts. The insignificant impact on cell growth and genome function suggests that Brassica sprouts may be safe vehicle of selenium to combat its dietary deficiency.

Utilization of thermal decomposition of immobilized compounds for the generation of gaseous standard mixtures used in the calibration of gas analysers

A new method of generation of gaseous standard mixtures has been developed in which the measured component is generated by the thermal decomposition of a substance chemically bonded to the surface of silica gel (modified silica gel). The method enables preparation of a standard mixture (generation of a measured component) immediately before the calibration step. Consequently, it can be applied primarily for the generation of standard mixtures containing volatile, malodorous, unstable and toxic compounds. The results of studies on the application of this method to the generation of multicomponent standard mixtures (mixtures of CO and CO2 in nitrogen) are presented.