Region of interest selection in heterogeneous digital image: Wine age prediction by comprehensive two-dimensional gas chromatography.

This study integrates genetic algorithm (GA) with partial least squares regression (PLSR) and various variable selection methods to identify impactful regions of interest (ROI) in heterogeneous 2D chromatogram images for predicting wine age. As wine quality and aroma evolve over time, transitioning from youthful fruitiness to mature, complex flavors, which leads to alterations in the composition of essential aroma-contributing compounds. Chromatograms are segmented into subimages, and the GA-PLSR algorithm optimizes combinations based on grayscale, red-green-blue (RGB), and hue-saturation-value (HSV) histograms. The selected subimage histograms are further refined through interval selection, highlighting the compounds with the most significant influence on wine aging. Experimental validation involving 38 wine samples demonstrates the effectiveness of this approach. Cross-validation reduces the PLS model error from 2.8 to 2.4 years within a 10 × 10 subset, and during prediction, the error decreases from 2.5 to 2.3 years. The study presents a novel approach utilizing the selection of ROI for efficient processing of 2D chromatograms focusing on predicting wine age.

Aroma Compounds in Essential Oils: Analyzing Chemical Composition Using Two-Dimensional Gas Chromatography-High Resolution Time-of-Flight Mass Spectrometry Combined with Chemometrics.

Analyzing essential oils is a challenging task for chemists because their composition can vary depending on various factors. The separation potential of volatile compounds using enantioselective two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC×GC-HRTOF-MS) with three different stationary phases in the first dimension was evaluated to classify different types of rose essential oils. The results showed that selecting only ten specific compounds was enough for efficient sample classification instead of the initial 100 compounds. The study also investigated the separation efficiencies of three stationary phases in the first dimension: Chirasil-Dex, MEGA-DEX DET-ß, and Rt-ßDEXsp. Chirasil-Dex had the largest separation factor and separation space, ranging from 47.35% to 56.38%, while Rt-ßDEXsp had the smallest, ranging from 23.36% to 26.21%. MEGA-DEX DET-ß and Chirasil-Dex allowed group-type separation based on factors such as polarity, H-bonding ability, and polarizability, whereas group-type separation with Rt-ßDEXsp was almost imperceptible. The modulation period was 6 s with Chirasil-Dex and 8 s with the other two set-ups. Overall, the study showed that analyzing essential oils using GC×GC-HRTOF-MS with a specific selection of compounds and stationary phase can be effective in classifying different oil types.

Enhanced multi-stir bar sorptive extraction for wine analysis: Alteration in headspace mode.

Multi-stir bar sorptive extraction (multi-SBSE) represents a viable alternative for recent trends in sample preparation based on a combination of extraction techniques. In this case, increased amount of sorbent and its extended polarity range could advance quality of experimental data obtained in foodomics or metabolomics investigations. With this in mind, it was developed multi-SBSE procedure suitable for authentication of botrytized wine produced in different countries of Tokaj wine region. A design of headspace mode of multi-SBSE was modified to provide additional agitation of a stir bar. An expanded profile of wine samples was obtained with the application of EG-Silicone and PDMS coated stir bars in headspace and direction immersion mode, respectively. Multivariate optimization based on central composite design was selected to determine the influence of various experimental parameters, including extraction temperature enhancing headspace extraction. In our case, proper description of the optimization results required application of a third-order polynomial model, which highlighted dominant influence of salt addition for extraction in both modes. Due to a large number of extracted compounds, comprehensive two-dimensional gas chromatography (GC × GC) was used for assessment of wine samples. Such approach allows reveleaing the presence of sulphur containing compounds, diols, ketone derivatives and methoxybenzenes linking a specific geographical origin. At the same time, the results obtained for compounds common for all the samples were processed with principal component analysis (PCA). Considerable progress for discrimination of the botrytized wines was mainly achieved with combined data from EG-Silicone and PDMS extraction.

Optimization of enantiomer separation in flow-modulated comprehensive two-dimensional gas chromatography by response surface methodology coupled to artificial neural networks: Wine analysis case study.

In spite of extensive applications of flow modulated comprehensive two-dimensional gas chromatography (FM-GG × GC) in different research areas, its application in the field of chiral separation is very limited. From a practical point of view, the establishment of experimental parameters for enantiomer separations is possibly more demanding in this case. Since the carrier gas flows in both dimensions, it affects not only the separation parameters, but also the fill/flush volumes of the modulator and its working efficiency. In this context, a multivariate design of experiment was applied to find the optimum experimental parameters of a reversed fill/flush (RFF) modulator for enantiomer separation of organic compounds present in botrytized wine samples. The results were described both with response surface methodology and artificial neural networks (ANN). The enantiomeric composition of chiral compounds present in the botrytized wines was used to identify their geographical origin, by principal component analysis (PCA). In addition, the developed one-class partial least squares (OC-PLS) model enabled recognition of the wine samples from the Tokaj wine region with 93% effectiveness in the presence of other samples.

Multivariate optimization of dual-sorbent dynamic headspace extraction of volatiles in wine analysis.

The main critical point of newly developed miniaturized sample preparation techniques is a limited extraction capacity. Dynamic headspace extraction offers increased volume of sorbent which is commonly used in environmental analysis. Application of two sorbents (Carbopack B/Carbopack X and Tenax® TA) at different extraction temperatures allows enhancing a range of volatile organic compounds available for analysis. Such approach was applied in our research for quantification of volatile organic compounds in botrytized wines with gas chromatography. The central composite design was included to analysis simultaneous effects of incubation time, incubation temperature, purge volume and purge flow. In attempt to properly assess results, the data evaluation involved Pareto charts, surface response methodology and principal component analysis. Multivariate experimental design revealed statistical significance of purge volume and quadratic terms of incubation time and temperature, for response of volatiles. The quantification method with 0.2-2.0 µg/L LOD and 0.5-5.0 µg/L LOQ values, was developed under simultaneously optimized experimental conditions such as a 54 °C incubation temperature, a 20.18 min incubation time, a 344.3 mL purge volume and a 16.0 mL/min purge flow. The increased levels of linalool oxide, ethyl phenylacetate, γ-hexalactone and α-terpineol were observed in the samples, that correlated with botrytized wine technology.

Classification of Botrytized Wines Based on Producing Technology Using Flow-Modulated Comprehensive Two-Dimensional Gas Chromatography.

The enantiomeric ratio of chiral compounds is known as a useful tool to estimate wine quality as well as observe an influence of wine-producing technology. The incorporation of flow-modulated comprehensive two-dimensional gas chromatography in this type of analysis provides a possibility to improve the quality of results due to the enhancement of separation capacity and resolution. In this study, flow-modulated comprehensive two-dimensional gas chromatography was incorporated in enantioselective analysis to determine the influence of winemaking technology on specific features of botrytized wines. The samples included Tokaj essences (high-sugar wines), Tokaj botrytized wines and varietal wines (Furmint, Muscat Lunel, Lipovina) and wines maturated on grape peels. The obtained data was processed with hierarchic cluster analysis to reveal variations in composition and assess classification ability for botrytized wines. A significant difference between the samples was observed for the enantiomeric distribution of ethyl lactate and presence of monoterpene alcohols. The varietal wines were successfully separated from the other types, which showed more similar results and could be divided with additional parameters. We observed a correlation between the botrytized wines and the varietal wines fermented with grape skins. As to the essences produced from juice of botrytized grapes, the results were quite similar to those of the botrytized wines, even though monoterpenes were not detected in the extracts.

A fast and inexpensive approach to characterize Slovak Tokaj selection wines using infrared spectroscopy and chemometrics.

The Tokaj Selection wines (hungarian equivalent "Aszú") are typical noble sweet wines produced in Tokaj wine region that falls within two countries, Slovakia and Hungary. Taking into account the economic importance and uniqueness of these wines, in this work, a new, fast and inexpensive method that combines infrared spectroscopy and multivariate models for characterization Slovak Tokaj Selection wines was developed. At first, sample authentication via one class models (dd-SIMCA) considered Slovak Tokaj Selection wines as target class. The non-target sample was considered to be only a Tokaj sample of Slovak origin. The resulting model was able to properly recognize samples of the target class with high sensitivity and specificity. Subsequently, the putna index was predicted via PLS models. RMSEP equals 0.44; REPpred of 9.6 and R2 0.95 was found in prediction step.

Novel sample preparation approaches in gas chromatographic analysis: Promising ideas.

The development of sample preparation procedures is still a dynamic process despite a number of already proposed techniques. The main challenge in this research field is to fully replace classical procedures like liquid-liquid extraction and solid-phase extraction in gas chromatographic analysis. Some progress has been already achieved for the last 20 years when miniaturized techniques were incorporated in ISO standards. The current review is focused on novel approaches in sample treatment that appeared since 2010. It includes research studies describing non-conventional instrumental design available to inspire future progress in the field. A combination of a few extraction principles and supporting with additional treatment are the main core suggested for improvement of sample preparation efficiency. This requires good compatibility of extraction media, assessment of multiple experimental parameters, and potential automatization possibilities.

Comparison of commercial organic polymer-based and silica-based monolithic columns using mixtures of analytes differing in size and chemistry.

Commercially available silica-based monolithic columns Chromolith RP-8e, Chromolith RP-18, and Chromolith HR RP-18, and polymer-based monolithic columns ProSwift RP-1S, ProSwift RP-2H, and ProSwift RP-3U varying in pore size and bonded phase have been tested for the fast separation of selected sets of analytes. These mixtures of analytes included small molecules (uracil, caffeine, 1-phenylethanol, butyl paraben, and anthracene), acylated insulins, and intact proteins (ribonuclease A, cytochrome C, transferrin, apomyoglobin, and thyroglobulin), and covered wide range of chemistries and sizes. Small molecules were well separated with a height equivalent to theoretical plate of 11-26 µm using silica-based monolithic columns, while organic polymer-based monoliths excelled in the fast sub 1 min baseline separations of large molecules. A peak capacity of 37 was found for separation of acylated insulins on Chromolith columns using a 3 min gradient at a flow rate of 3 ml/min. Poor recovery of proteins from Chromolith columns and significant peak tailing of small molecules using ProSwift columns were the major obstacles in using monolithic columns in those applications.

Volatile fingerprinting of the plum brandies produced from different fruit varieties.

Nowadays, fingerprinting of food became one of the most perspective analytical tools to resolve a problem of food quality and authentication, especially in difficult cases like differentiation of fruit varieties. In this work, plum brandies distillated by the same technology from 25 plum cultivars were distinguished by comprehensive two-dimensional gas chromatographic analysis and sensory evaluation. The number of identified compounds in studied samples varied between 91 and 195 depending on the plum variety. Enriched volatile organic compounds (VOC) profile was identified for the samples received from "Chrudimer", "Cacak Fruitful" and "Hanita" plum varieties, whereas in the case of "Gabrovská", "Presenta", Elena" and "President" plum varieties, the VOC profile was significantly reduced. From qualitative point of view, the particular plum brandies showed differences in the presence of unsaturated fusel alcohols (e.g. 3-methyl-3-buten-1-ol, trans-3-hexenol), unsaturated aldehydes (2-butenal, 2-nonenal), monoterpene derivatives (e.g. linalool acetate, geraniol acetate) and lactones, which were mainly detected at the trace level.

Distribution of enantiomers of volatile organic compounds in selected fruit distillates.

The enantiomer ratios of chiral volatile organic compounds in fruit distillates were determined by multidimensional gas chromatography using solid-phase microextraction (SPME) as a sample treatment procedure. Linalool and its oxides, limonene, α-terpineol, and nerolidol, were present at the highest concentration levels, while significantly lower amounts of ß-citronellol and lactones were found in the studied samples. However, almost all terpenoids mainly occur as a racemic or near-racemic mixture; enantiomer distribution of some chiral organic compounds in fruit distillates correlated to a botanical origin. In particular, a significant enantiomeric excess of (R)-linalool and (S)-α-terpineol was found only for pear brandy, and likewise the dominance (R)-limonene and the second eluted enantiomer of nerolidol for Sorbus domestica and strawberry, respectively. The distribution of γ-lactones stereoisomers was more nonspecific, with a general excess of the R-enantiomer.

The Tracing of VOC Composition of Acacia Honey During Ripening Stages by Comprehensive Two-Dimensional Gas Chromatography.

In this study, VOC profiles of acacia flowers and honey samples at different processing stages and related comb wax samples were studied using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. It was found that some monoterpene compounds like α-pinene, myrcene, cis-ß-ocimene, and 4-terpineol were common for acacia flower and all acacia honey samples, and the presence of verbenone and ocimene was first established in acacia honey. The most enriched VOC profile was obtained for raw honey before cell capping, where the final composition of lactones was achieved. On the contrary, number of alcohols, esters, and variety of terpenes, as well as their concentration in the honey samples decrease through ripening processes. Strained honey was characterized by the absence of camphor, α-bisabolol, and 3-carene, while isophorone and hexanoic acid were identified only in this type of honey. The composition of final VOC profile of honey was also influenced by the age of comb wax. The additional aromatic and lactone compounds, e.g., phenol, 1-phenylethanol, δ-hexalactone, and γ-heptalactone were observed for honey maturated in old dark comb wax.

A solid-phase extraction method using Transcarpathian clinoptilolite for preconcentration of trace amounts of terbium in water samples.

BACKGROUND: In spite of the fact that terbium is one of the rarest elements in the Earth's crust, it is frequently used for the production of high technological materials. At the result, an effective combination of sample preparation procedure and detection method for terbium ions in different matrices is highly required. The solid-phase extraction procedure with natural Transcarpathian clinoptilolite thermally activated at 350 °C was used to preconcentrate trace amounts of terbium ions in aqueous solutions for a final spectrophotometric determination with arsenazo III. RESULTS: Thermogravimetric investigations confirmed the existence of relations between changes that appeared during dehydratation of calcined zeolite and its sorption affinity. Since the maximum of sorption capacity towards terbium was observed at pH 8.25, a borate buffer medium (2.5 · 10(-4) М) was used to maintain ionic force and solution acidity. Terbium was quantitatively removed from the solid-phase extraction column with a 1.0 M solution of sodium chloride (pH 2.5). The linearity of the proposed method was evaluated in the range of 2.5-200 ng · mL(-1) with detection limit 0.75 ng · mL(-1). CONCLUSIONS: Due to acceptable recoveries (93.3-102.0 %) and RSD values (6-7.1) from spiked tap water, the developed method can be successfully applied for the determination of trace amounts of terbium ions in the presence of major components of water. Graphical abstractSorption of terbium(III) ions on clinoptilolite.