Helena Prosen

Solid-phase microextraction

Abstract In recent years, much attention in analytical chemistry has been paid to sample preparation techniques, especially those which minimise the consumption of organic solvents. One of the most promising of these, solid-phase microextraction (SPME), is presented in both its theoretical and practical aspects. Conditions which affect its performance are assessed, as are the problems which may arise from its use. Finally, some typical applications are listed, highlighting the methods sensitivity and precision, and the range of samples where SPME can be used successfully.

On-line trace enrichment of polar pesticides in environmental waters by reversed-phase liquid chromatography-diode array detection-particle beam mass spectrometry

The determination of a group of pesticides by RPLC-diode array detection, coupled on-line to particle beam MS, is developed for the analysis of different environmental water. On-line trace enrichment of 100 ml of sample on a PLRP-S precolumn allows the determination of most pesticides at levels between 0.2 and 5 μg l−1 and detection limits in the range 0.05–0.5 μg l−1 for diode array detection and 0.02–0.5 μg l−1 for particle beam MS. With real-life samples, a distinct matrix effect is observed in particle beam MS detection, which is caused by coeluting compounds acting as carriers. This improves analyte detectability and requires standard addition to be used for quantification. Different river and drinking waters were analysed and some pollutants were detected at sub- μg l−1 levels.

Evaluation of matrix effect in determination of some bioflavonoids in food samples by LC–MS/MS method

In the present work the LC-MS/MS method with solid phase extraction for simultaneous determination of bioflavonoids rutin, quercetin, hesperidin, hesperetin and kaempferol in some food samples (red onion, orange peel and honey) was developed and the matrix effect accompanying this determination was quantified. The matrix effect evaluated using a postextraction addition method was found to be negative in the range -44 to -0.5%, indicating ionization suppression and strongly depended on bioflavonoid concentration. The observed matrix effect was explained taking into account the co-elution of phenolic acids, in terms of their acid-base and hydrophilic properties. The efficacy of extraction expressed as the absolute recoveries of flavonoids were 88-96%, indicating very good efficiency of extraction. The extracts of food samples obtained either by Soxhlet or ultrasonic extraction were analyzed for bioflavonoid content by the LC-MS/MS method in selected reaction monitoring mode using a triple quadrupole detector and standard addition method, which was found to be the most suitable calibration approach for these samples. The optimized separation was achieved on a Phenomenex Gemini C18 column with gradient elution and mobile phase composition A: 2% acetic acid in water and B: acetonitrile. R(s) values were in the range from 1.3 to 3.1, indicating good selectivity of the method. The obtained results (mg/100g fresh weight) for different bioflavonids were for rutin 0.16, for quercetin in the range 0.65-56, for hesperidin 0.016-24, for hesperetin 0.0068-36.4 and for kaempferol 0.14-1.63 and generally show good agreement with published data. Low detection limits (0.014-0.063 μg/mL) were obtained with acceptable recoveries (86-114%). Total time of analysis was less than 40 min, therefore the proposed method represents significant improvement over existing methods.

Optimization of an analytical procedure for the determination of triazine herbicides in environmental samples

Abstract A clean-up procedure and high-performance liquid chromatographic conditions were optimized for the determination of triazines in drinking and surface water. Two extraction systems were tested: off-line solid-phase extraction (SPE) with C18-bonded silica gel cartridges and on-line SPE with PLRP-S (styrene-divinylbenzene copolymer) preconcentration cartridges. The on-line SPE procedure was chosen for further work. Chromatographic conditions were optimized for UV absorbance and particle beam (PB) MS detection. The LC-UV analytical system with on-line preconcentration showed excellent linearity over the concentration range tested and low detection limits (below 0.05 μg/l) for drinking water. With preconcentration from large volumes of water, some triazines and other pesticide pollutants could be detected in drinking and river water by PB-MS. Quantification was achieved by means of the standard addition method. For soil samples, the extraction procedure was off-line and more elaborate.

Development and validation of dried blood spots technique for quantitative determination of topiramate using liquid chromatography–tandem mass spectrometry

An LC-MS/MS method for determination of the anti-epileptic drug topiramate (TPM) in dried blood spot (DBS) samples was developed and validated. DBS samples were prepared by spotting 30 μL of spiked whole blood onto FTA(TM) DMPK-C cards and drying for at least 3 h. Six-millimetre punched spots were then extracted by using a mixture of methanol and water (90:10, v/v) with deuterated internal standard (topiramate-d12). The extracted samples were injected into a liquid chromatograph equipped with a tandem mass spectrometric detector. Negative ions were monitored in the selected reaction monitoring mode and transitions m/z 338.2 → 78.1 and m/z 350.3 → 78.1 were used for the quantitative evaluation of TPM and internal standard, respectively. The results obtained from validation were statistically evaluated according to the requirements of the European Medicines Agency and US Food and Drug Administration regulatory guidelines. The linearity of the method was checked within a concentration range from 10 to 2000 ng/mL. The validation results indicate that the method is accurate, precise, sensitive, selective and reproducible.

Identification and Quantification of Aroma Compounds of Tartary Buckwheat (Fagopyrum tataricum Gaertn.) and Some of Its Milling Fractions

UNLABELLED Tartary buckwheat (Fagopyrum tataricum) seeds have a strong aroma that characteristically differs from the aroma of common buckwheat (Fagopyrum esculentum). Its phytochemical background has only been recently investigated. The aim of this study was to identify and quantify individual compounds responsible for tartary buckwheat aroma. Volatiles from different samples (whole seed, flour, and husks) were extracted with simultaneous extraction and distillation by Likens-Nickerson apparatus and analyzed by GC-MS. A total of 48 compounds were quantified and their odor activity values (OAV) were calculated. OAV of 26 compounds was higher than 10; therefore, they significantly contribute to the overall tartary buckwheat aroma. The compounds with OAV > 500 were: (E,E)-2,4-decadienal, (E)-2-nonenal, 2-phenylethanol, (E,E)-2,4-nonadienal, hexanal, decanal, and nonanal. The most important difference from the aroma of common buckwheat is the absence of salicylaldehyde and presence of naphthalene. Salicylaldehyde could be proposed as a marker to detect contamination/adulteration of tartary buckwheat with common buckwheat. PRACTICAL APPLICATION Buckwheat is becoming one of important alternative crops. Its products which are rich in proteins, fiber, vitamins, and antioxidants have been associated with healthy nutrition. Although tartary buckwheat is similar to more familiar common buckwheat, their characteristic aromas differ notably. This study expands recent research on aroma of tartary buckwheat tea to seed, flour, and husks, and suggests how products from different species of buckwheat can be distinguished by analysis of aroma compounds.

Aroma Compounds in Buckwheat (Fagopyrum esculentum Moench) Groats, Flour, Bran, and Husk

ABSTRACT Buckwheat is a pseudocereal with a strong characteristic aroma. Compounds responsible for the aroma of buckwheat groats were recently identified, but the distribution of aromatic compounds between different fractions of the buckwheat kernel (flour, bran, and husk) is not yet known. In this study, the composition of aromatic compounds in buckwheat seed fractions was investigated and compared to the composition of aromatic compounds in groats produced from the same batch of buckwheat seeds. Volatiles from each sample were extracted with simultaneous distillation/extraction with a Likens-Nickerson apparatus. Extracts were analyzed by gas chromatography coupled with mass spectrometry (GC-MS) with electron ionization. Apart from the aroma molecules present in all fractions, compounds that are present only in flour or bran, but not in groats, were also found. Furthermore, some compounds were identified only in buckwheat groats but not in buckwheat flour or bran [octanal, (E,E)-2,4-heptadienal, (E)-2-de...

Applications of Liquid-Phase Microextraction in the Sample Preparation of Environmental Solid Samples

Solvent extraction remains one of the fundamental sample preparation techniques in the analysis of environmental solid samples, but organic solvents are toxic and environmentally harmful, therefore one of the possible greening directions is its miniaturization. The present review covers the relevant research from the field of application of microextraction to the sample preparation of environmental solid samples (soil, sediments, sewage sludge, dust etc.) published in the last decade. Several innovative liquid-phase microextraction (LPME) techniques that have emerged recently have also been applied as an aid in sample preparation of these samples: single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME). Besides the common organic solvents, surfactants and ionic liquids are also used. However, these techniques have to be combined with another technique to release the analytes from the solid sample into an aqueous solution. In the present review, the published methods were categorized into three groups: LPME in combination with a conventional solvent extraction; LPME in combination with an environmentally friendly extraction; LPME without previous extraction. The applicability of these approaches to the sample preparation for the determination of pollutants in solid environmental samples is discussed, with emphasis on their strengths, weak points and environmental impact.

Determination of seven drugs of abuse and their metabolites in surface and waste water using solid-phase extraction coupled to liquid chromatography with high-resolution mass spectrometry

A method based on liquid chromatography with electrospray ionization high-resolution mass spectrometry (Exactive Orbitrap) combined with solid-phase extraction using a strong cationic exchange mixed-mode sorbent has been developed for the determination of seven drugs of abuse, including two synthetic cathinones, as well as some of their metabolites in environmental water samples. The method provides low detection limits and a high confirmation power thanks to the diagnostic and two fragment ions monitored for each compound in high-resolution mass spectrometry, providing six identification points for each analyte. The clean-up step based on methanol in the extraction step adequately decreased the matrix effect, mainly for river and effluent water, and provided suitable process efficiency. Method detection and quantitation limits for environmental waters were at low nanogram per liter. The method was applied to analyze the samples of influent and effluent wastewater, as well as surface water. Codeine, methadone, and its metabolite were determined in all samples of wastewater and the metabolite of cocaine, benzoylecgonine, was found at the highest concentration.

The response of Monoterpenes to Different Enzyme Preparations in Gewürztraminer (Vitis vinifera L.) Wines

The α-terpineol, linalool, nerol and geraniol, which are the main aromatic monoterpenes in the grapevine variety Gewurztraminer, were determined in the grapes, must and wine after treatment with six different pectolytic enzymes [Lallzyme-β (‘Lall’); Rohavin VR-C (‘VRX’), Rohapect D5L (‘D5L’), Rohavin MX (‘MX’), Rohapect VRC (‘VRC’), Endozym cultivar A (‘Cult. A’)], and after treatment with β-glucosidase (βG, EC 3.2.1.21). The concentrations of monoterpenic compounds were determined by solid-phase microextraction (SPME) and GC-MS. The most abundant monoterpene in the grapes of Gewurztraminer was geraniol (66.7 μg/L), followed by nerol (13.3 μg/L), α-terpineol (7.8 μg/L) and finally linalool (3.3 μg/L). Gewurztraminer wine from must treated with the Lall enzyme preparation was the most aromatic, which was also confirmed by chemical and sensory analysis in which the concentrations of nerol (45.9 μg/L), geraniol (31.8 μg/L), α-terpineol (10.5 μg/L) and linalool (6.1 μg/L) were determined. The wines produced from must treated chemically with enzymes showed higher concentrations of many of the monoterpene compounds compared to the control, although the sensorial analysis did not affirm this convincingly.