Increased concentration of PAH derivatives in biochar-amended soil observed in a long-term experiment.

During biochar preparation or application some toxic substances may be formed. The established limitations of the content of polycyclic aromatic hydrocarbons (PAHs) aim to monitor the fate of PAHs in the life cycle of biochar. The latest studies have revealed that besides PAHs, some of their derivatives with confirmed toxicity are formed. There has been no policy regards PAH derivatives in biochar yet. The aim of the presented studies was the estimation the changes in the content of PAHs and their derivatives during the agricultural application of biochar. A pot experiment with grass revealed that in a short time, both the content of PAHs and their derivatives was reduced. Similarly, when biochar was added to soil in a long-term experiment, the content of determined derivatives was below the limit of detection, whereas interestingly, the content of pristine PAHs increased with time. Co-addition of biochar and sewage sludge increased the content of PAHs and their derivatives indicating potential environmental hazard due to their presence. However, the key point is the estimation of the bioavailability of PAHs and their derivatives as only the bioavailable fraction is revealing the environmental hazard.

Cannabigerol (CBG) signal enhancement in its analysis by gas chromatography coupled with tandem mass spectrometry.

PURPOSE: According to recent reports, cannabigerol (CBG) concentration level in blood and body fluids may have forensic utility as a highly specific albeit insensitive biomarker of recent cannabis smoking. While the analytical sensitivity of cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabichromene (CBC) or cannabinol (CBN) estimation by gas chromatography-mass spectrometry (GC-MS) is similar and sufficiently high, it is exceptionally low in the case of CBG (ca. 25 times lower than for the other mentioned cannabinoids). The purpose of this study is to explain the reasons for the extremely low analytical sensitivity of GC-MS in estimating CBG and to present possible ways of its improvement. METHODS: Nuclear magnetic resonance (NMR) data and GC-MS responses to CBG and its various derivatization and transformation products were studied. RESULTS: The validation data of individual derivatives of CBG and its transformation products were established. CBG silylation/acylation or hydration allows to decrease LOD about 3 times, whereas the formation of pyranic CBG derivative leads to 10-times decrease of LOD. The paper enriches the literature of the subject by providing MS and NMR spectra, not published so far, for derivatives of CBG and its transformation products. The most likely cause of low GC-MS response to CBG is also presented. CONCLUSIONS: The presented results shows that although the signal increase of CBG can be obtained through its derivatization by silylation and/or acylation, the greatest increase is observed in the case of its cyclization to the pyranic CBG form during the sample preparation process. The CBG cyclization procedure is very simple and workable in estimating this cannabinoid in blood/plasma samples.

Fast and reliable determination of phthalic acid esters in soil and lettuce samples based on QuEChERS GC-MS/MS.

Phthalates are commonly used as plasticizers, and solvents in industry and households. We propose an application of the QuEChERS method for the determination of six PAEs in the soil and lettuce (roots and leaves) by GC-MS/MS. The QuEChERS method validation procedure was performed and good linearity (>0.997), recovery (97.2-99.1 %), very low detection limits (0.09-0.43 ng/g), and satisfactory inter- and intraday precision (∼4%) were obtained confirming that QuEChERS GC-MS/MS applied for PAEs determination in the environmental samples is a cheap and environmentally friendly method. In general, the higher the number of carbon atoms in PAEs, the higher the percentage noted in the lettuce roots. At higher PAEs concentration (60 ng/g) the main bis(2-ethylhexyl) phthalate (DEHP) sink were roots whereas at lower concentrations (30 ng/g) most of DEHP was noted in lettuce leaves implying that the fate of PAEs was governed not by the chemical structure of PAEs but rather partitioning (logKow).

Determination of 3- and 4-chloromethcathinone interactions with plasma proteins: study involving analytical and theoretical methods.

PURPOSE: The purpose of this paper was to determine 3- and 4-chloromethcathinone (3- and 4-CMC) binding degree and possible binding interaction modes with human serum albumin (HSA) using analytical and theoretical methods. METHODS: Experimental determination of 3- and 4-CMC binding degree with HSA was performed using gas chromatography-tandem mass spectrometry preceded by the equilibrium dialysis (ED) and ultrafiltration (UF). Nuclear magnetic resonance (NMR) spectroscopy was used to determine 3- and 4-CMC epitope-binding maps and possible binding sites in HSA. The molecular docking and molecular dynamics were employed to obtain detailed information about binding modes of 3- and 4-CMC enantiomers in HSA. RESULTS: As follows from the presented data, the degree of binding of 3- and 4-CMC is at a similar level of approx. 80%. This indicates a relatively strong binding of CMC to plasma proteins. The model studies employing the NMR spectroscopy and molecular simulations indicate that both CMCs bind to HSA. The whole 3- and 4-CMC molecules are embedded in the binding sites, with aromatic moieties being in the closest contact with the HSA residues. Moreover, conducted experiments show that  Sudlow site II is the main binding center for 3- and 4-CMC and  Sudlow site I acts as the secondary binding site. CONCLUSIONS: Although many studies describe pharmacological and toxicological properties of synthetic cathinones (SC), the data taking SCs binding in plasma into consideration are scarce. To our knowledge, this is the first report presenting comprehensive experimental and theoretical characterization of 3- and 4-CMC binding with plasma proteins.

GC vs. HPLC in quantitation of CBD, CBG, ∆9-THC and CBN in plasma using different sample preparation methods.

The sensitivity of complex analytical procedures depends not only on the sensitivity of the analytical instrument used, but also on the recovery degree of the examined analyte by the employed sample preparation method. The recovery degrees of individual cannabinoids reported in literature, estimated using the same sample preparation method, are unexpectedly divergent. Therefore, the aim of this study was a thorough assessment of the most commonly used sample preparation methods, such as protein precipitation, LLE, QuEChERS and SPE, in the context of the reliability of the obtained results. The presented report shows that the highest sensitivity, precision and reliability of the chromatographic analysis of CBG, CBD, ∆9-THC and CBN in human plasma can be obtained using SPE. The recovery degrees of these cannabinoids by SPE are highly repeatable and exceed 95 %, while they are significantly lower for such sample preparation methods as protein precipitation, LLE and QuEChERS (ca. 80, 65 and 87, respectively). Moreover, the supernatants obtained by the latter methods contain interferents evoking matrix-effect, which makes reliable quantification of the listed cannabinoids by GC difficult. To our knowledge, the paper is the first such extensive comparison of sample preparation procedures used for the determination of cannabinoids in plasma by GC-MS and HPLC-MS. The presented results and the discussion allow to understand why different recovery degrees for the same xenobiotic can be find in literature despite they have been estimated using the same or different sample preparation method or different chromatography types.

The Anti-Acne Potential and Chemical Composition of Knautia drymeia Heuff. and Knautia macedonica Griseb Extracts.

The treatment of acne and other seborrheic diseases has arisen as a significant clinical challenge due to the increasing appearance of multi-drug resistant pathogens and a high frequency of recurrent lesions. Taking into consideration the fact that some Knautia species are valuable curatives in skin diseases in traditional medicine, we assumed that the thus far unstudied species K. drymeia and K. macedonica may be a source of active substances used in skin diseases. The purpose of this study was to evaluate the antioxidant, anti-inflammatory, antibacterial, and cytotoxic activities of their extracts and fractions. An LC-MS analysis revealed the presence of 47 compounds belonging to flavonoids and phenolic acids in both species while the GC-MS procedure allowed for the identification mainly sugar derivatives, phytosterols, and fatty acids and their esters. The ethanol as well as methanol-acetone-water (3:1:1) extracts of K. drymeia (KDE and KDM) exhibited great ability to scavenge free radicals and good capacity to inhibit cyclooxygenase-1, cyclooxygenase-2, and lipoxygenase. Moreover, they had the most favorable low minimal inhibitory concentration values against acne strains, and importantly, they were non-toxic toward normal skin fibroblasts. In conclusion, K. drymeia extracts seem to be promising and safe agents for further biomedical applications.

Microorganisms and their metabolites affect the content of polycyclic aromatic hydrocarbons and their derivatives in pyrolyzed material.

Toxic polycyclic aromatic hydrocarbons (PAHs) and more toxic N- and O-containing derivatives can be determined in biochar. However, their fate in the environment and bioavailability depends on many parameters and was not studied yet. In the presented studies a set of biochars obtained from various feedstock at the same pyrolysis temperature (600 °C) subjected to environmental pressure e.g. soil microorganisms and enzymes was described. Presented study aimed to determine the effect of biological agents on the physicochemical characteristic and the content of PAHs and their derivatives in biochars after long-term treatment (6 months). The results indicated that enzymatic aging usually lowered (up to 94 %) the content of PAHs and their derivatives in biochar. Simultaneously, biological aging reduced the bioavailability of tested compounds. Considering the total fraction of PAHs and their derivatives, biochars treated with nutrients and microbial inoculum were characterized by the lowest content of analytes (even in comparison to biochars treated with nutrients alone). To complement the obtained results, the content of C, H, N, O, and ash as well as specific surface area, aromaticity, polarity, and hydrophilicity in biochar before and after modifications were determined. In general, enzymatic aging increased, and biological aging decreased the content of C% and H% in biochar. Both aging processes lowered the H/C ratio which indicated the decrease of the aromatization degree for artificially altered biochar.

Unexpected formation of dichloroacetic and trichloroacetic artefacts in gas chromatograph injector during Cannabidiol analysis.

The knowledge about the stability of compounds and possible ways of their transformation in the process of sample preparation for analysis and during analysis itself is very helpful in the assessment of possible errors which can appear when an accurate and precise estimation of compound concentration in tested samples is attempted. The present paper shows that a significant amount of CBD present in the blood/plasma sample analyzed by means of GC transforms in the hot GC injector not only to 9α-hydroxyhexahydrocannabinol, 8-hydroxy-iso-hexahydrocannabinol, Δ9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, and cannabinol but also to the trichloroacetic esters of Δ9-THC and Δ8-THC and, unexpectedly, to their dichloroacetic esters when trichloroacetic acid is used as protein precipitation agent. The increase of GC injector temperature favors the formation of dichloroacetic esters of Δ9-THC and Δ8-THC in relation to their trichloroacetic ones. The appearance of dichloroacetic esters of Δ9-THC and Δ8-THC among CBD transformation products is probably the result of the thermal decomposition of their trichloroacetic esters. The transformation of trichloroacetic derivatives of organic compounds into their dichloroacetic derivatives in GC injector has not been reported yet. The instability of trichloroacetic derivatives of Δ8-/Δ9-THC during their GC analysis is probably accounts for the lack of their GC-MS spectra in the databases. NMR, GC-MS and LC-MS spectra of the newly discovered derivatives constitute an important element of the work. The obtained results demonstrate why the use of trichloroacetic acid for plasma samples deproteinization should be avoided when CBD and/or THC are determined by GC.

Chromatographic analysis of CBD and THC after their acylation with blockade of compound transformation.

METHODS: for the analysis of cannabinoids in bio-matrices are continually improved to achieve best possible sensitivity in their detection and accurate quantification. It has been well documented that CBD cyclizes to Δ9-THC and Δ9-THC isomerizes to Δ8-THC under acidic conditions by means of a Lewis-acid-catalyzed process, causing difficulty in accurate quantification of Δ9-THC in the presence of CBD, of CBD itself and of Δ9-THC itself when these compounds have to be derivatized by acylation. The present paper shows that CBD cyclization and Δ9-THC isomerization can be blocked by tertiary amines or azines, which capture protons appearing in the derivatizing mixture during acylation. The efficiency of the described acylation of CBD depends on the time and temperature of the derivatizing process, whereas the degree of CBD acylation, i.e. the synthesis of mono- or di-acylate CBD derivative, depends on the mutual ratio of the cannabinoid, the acylating agent and the proton binding compound. The way of mono- and di-acyl CBD derivatives formation described in the paper has not been reported yet. The paper contains a comprehensive analytical characterization of two types of CBD acyl derivatives, CBD-TFA and CBD-Ac, obtained by NMR, GC-MS and LC-MS.

Long-term physical and chemical aging of biochar affected the amount and bioavailability of PAHs and their derivatives.

Biochar applied into the soil is recommended as an effective tool for increasing its properties and crop productivity. However, biochar can contain some potentially toxic compounds such as polycyclic aromatic hydrocarbons (PAHs). Moreover, during biochar production or environmental application (e.g. as soil fertilizer), more toxic PAHs derivatives containing nitrogen, oxygen or sulfur can be formed. There is a lack of information on how the environmental factors affect the bioavailability of such compounds during the long-term application of BC into the soil. In the presented studies the effects of physical (freeze-thaw cycles) and chemical aging (temperatures 60 °C and 90 °C) on the total and bioavailable content of PAHs and their derivatives were estimated. The results indicate that long-term (6 months) aging affected the physicochemical characteristic of biochars promoting the formation of new C and O-containing species on the BC surface increasing their polarity and hydrophilicity. Physical and chemical aging promoted the formation of compounds with higher molecular weight and a significant (up to 550 %) increase in the bioavailability of PAHs and their derivatives. The results of this study highlight the importance of the bioavailable fraction of PAHs and their derivatives for evaluation of the toxicity of aged biochar.

Low bioavailability of derivatives of polycyclic aromatic hydrocarbons in biochar obtained from different feedstock.

In the last years, there is great progress in the field of studies on the thermal transformation of wastes into valuable materials such as biochar. High-temperature processes, however, are connected with the formation of polycyclic aromatic hydrocarbons (PAHs) with confirmed toxicity. However, during pyrolysis, some derivatives containing oxygen, nitrogen, or sulfur can also be formed. Their toxicity is expected to be higher than parent PAHs. However, the key parameter in the agricultural application of carbonaceous materials is PAHs' bioavailability. The aim of the presented studies was the determination of the effect of various feedstock (wheat straw (Triticum L.), willow (Salix viminalis), sunflower, residues from softwood and hardwood, sewage sludges, and residues from biogas production) on the formation of PAHs and their derivatives (O-, N-PAHs) in biochar and their bioavailability. The results indicated that the content of total and bioavailable PAHs in obtained biochar was rather low. The concentration of total PAHs in plant-derived biochar reached 57 ± 3 ng g-1 - 181 ± 8 ng g-1, whereas sewage sludge-derived biochar contained from 121 ± 6 ng g-1 to 188 ± 9 ng g-1 of PAHs. The highest concentration of PAHs was noted in biochar obtained from residues from biochar production - up to 202 ± 9 ng g-1. The total concentration of bioavailable PAHs was lower and reached 2-4.45 ng L-1 for plant-derived biochar, 3-40 ng L-1 for sewage sludge-derived biochar. The highest content of bioavailable PAHs was noted in biochar obtained from residues from biogas production: 9-42 ng L-1 indicating that increased attention should be paid to using this type of biochar. Among PAHs derivatives, nitronaphthalene, 1-methyl-5-nitronaphthalene, 1-methyl-6-nitronaphthalene, 9,10-anthracenedione, 4H-cyclopenta(def)phenanthrene, nitropyrene were determined at various levels and their concentrations were from below the limit of detection (LOD) to 28 ng L-1 for plant-derived biochar, 3-16 ng L-1 for biochar obtained from residues from biogas production, and 5-45 ng L-1 for sewage sludge-derived biochar. The content of bioavailable PAHs derivatives was, generally, one order of magnitude lower than parent PAHs derivatives, and reached from below LOD up to almost 1 ng L-1 for plant-derived biochar, from 0.5 to 2 ng L-1 for biochar obtained from residues from biogas production, and from 0.2 to almost 5 ng L-1 for sewage sludge-derived biochar confirming the safety of agricultural usage of biochar.

Can Extracts from the Leaves and Fruits of the Cotoneaster Species Be Considered Promising Anti-Acne Agents?

This study aimed to evaluate the phenolic profile and biological activity of the extracts from the leaves and fruits of Cotoneaster nebrodensis and Cotoneaster roseus. Considering that miscellaneous species of Cotoneaster are thought to be healing in traditional Asian medicine, we assumed that this uninvestigated species may reveal significant therapeutic properties. Here, we report the simultaneous assessment of chemical composition as well as biological activities (antioxidant, anti-inflammatory, antibacterial, and cytotoxic properties) of tested species. Complementary LC-MS analysis revealed that polyphenols (especially flavonoids and proanthocyanidins) are the overriding phytochemicals with the greatest significance in tested biological activities. In vitro chemical tests considering biological activities revealed that obtained results showed different values depending on concentration, extraction solvent as well as phenolic content. Biological assays demonstrated that the investigated extracts possessed antibacterial properties and were not cytotoxic toward normal skin fibroblasts. Given the obtained results, we concluded that knowledge of the chemical composition and biological activities of investigated species are important to achieve a better understanding of the utilization of these plants in traditional medicine and be useful for further research in their application to treat various diseases, such as skin disorders.

Oleamide as analyte protectant in GC analysis of THC and its metabolites in blood.

Methods for the analysis of cannabinoids in bio-matrices are continually being developed, to achieve a proper sensitivity required for their detection and accuracy in their quantification. The presented paper shows that the analytical sensitivity of GC-MS to THC and its metabolites in blood samples can be significantly increase by oleamide (OLA) addition to the examined sample, which evokes the matrix effect of transient character. The magnitude of signal increment resulting from oleamide presence in the examined sample is the greatest for THC metabolites and depends on oleamide concentration in the examined sample. The use of transient matrix effect to increase the sensitivity of the analysis can be applied not only in QuEChERS procedure, which is applied in the described experiments, but also in other blood sample preparation methods. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of THC and its metabolites in blood allowed to lower limit of detection (LOD) approximately by 20.5%, 87.6% and 90.1% in the case of THC, THC-OH and THC-COOH, respectively.

Formation of trifluoroacetic artefacts in gas chromatograph injector during Cannabidiol analysis.

The knowledge of compounds stability in the process of sample preparation for analysis and during analysis itself helps assess the accuracy and precision of estimating their concentration in tested samples. The present paper shows that a significant amount of CBD present in the blood/plasma sample analyzed by means of GC transforms in the hot GC injector not only to 9α-hydroxyhexahydrocannabinol, 8-hydroxy-iso-hexahydrocannabinol, delta-9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, and cannabinol but also to the trifluoroacetic esters of Δ9-THC and Δ8-THC, when trifuoroacetic acid is used as protein precipitation agent. The amount of those newly revealed CBD transformation products depends on the GC injector temperature and on the extrahent type when extracts of the supernatants centrifuged from human plasma samples are analyzed after their preliminary protein precipitation by trifuoroacetic acid. Although trifuoroacetic acid as a protein precipitating agent has many disadvantages, it is quite often used for this purpose due to its very high protein precipitation efficiency. The results presented in the study demonstrate why the use of trifuoroacetic acid for plasma samples deproteinization should be avoided when CBD is determined by GC.

The Anti-Acne Potential and Chemical Composition of Two Cultivated Cotoneaster Species.

In light of current knowledge on the role of reactive oxygen species and other oxidants in skin diseases, it is clear that oxidative stress facilitates inflammation and is an important factor involved in skin diseases, i.e., acne. Taking into consideration the fact that some Cotoneaster plants are valuable curatives in skin diseases in traditional Asian medicine, we assumed that thus far untested species C. hsingshangensis and C. hissaricus may be a source of substances used in skin diseases. The aim of this study was to evaluate the antioxidant, anti-inflammatory, antimicrobial, and cytotoxic activities of their various extracts. LC-MS analysis revealed the presence of 47 compounds (flavonoids, phenolic acids, coumarins, sphingolipids, carbohydrates), while GC-MS procedure allowed for the identification of 42 constituents (sugar derivatives, phytosterols, fatty acids, and their esters). The diethyl ether fraction of C. hsingshangensis (CHs-2) exhibited great ability to scavenge free radicals and good capacity to inhibit cyclooxygenase-1, cyclooxygenase-2, lipoxygenase, and hyaluronidase. Moreover, it had the most promising power against microaerobic Gram-positive strains, and importantly, it was non-toxic toward normal skin fibroblasts. Taking into account the value of the calculated therapeutic index (>10), it is worth noting that CHs-2 can be subjected to in vivo study and constitutes a promising anti-acne agent.

Improving the sensitivity of estimating CBD and other xenobiotics in plasma samples: Oleamide-induced transient matrix effect.

The paper discusses the matrix effect evoked by oleamide (OLA), a compound frequently found in samples processed and/or stored in lab polypropylene vials or disposable syringes. In the case of many substances a higher response for their samples containing OLA than for net solutions is observed. The analyte signal gain resulting from OLA presence in the examined sample depends on the ratio of OLA concentration to analyte concentration. A characteristic feature of the matrix effect evoked by oleamide is its short duration, which makes the chromatographic data (retention value and signal magnitude of examined compound) repeatable and reproducible. The identified "transient matrix effect" may significantly increase the sensitivity of many analytical procedures employing GC. Evoking the transient matrix effect by means of OLA in the experimental analytical quantitation of cannabidiol in plasma allowed to lower its limit of detection (LOD) by more than 50 %.

Conversion of cannabidiol (CBD) to Δ9-tetrahydrocannabinol (Δ9-THC) during protein precipitations prior to plasma samples analysis by chromatography - Troubles with reliable CBD quantitation when acidic precipitation agents are applied.

The growing popularity of supplements containing cannabidiol (CBD), mainly CBD oils, in self-medication of humans and the increased interest in this compound in different preclinical and clinical trials stimulates the development of procedures of CBD analysis in plasma for the study of CBD pharmacology in people and animals or in establishing dose-therapeutic effect relationships of this compound. Preliminary removal of protein by its precipitation from plasma is still one of the willingly applied plasma sample preparation methods in many analytical procedures estimating plasma drug concentration, including CBD. The present paper shows that a significant amount of CBD transforms to Δ9-tetrahydrocannabinol (Δ9-THC) in a hot GC injection system when acidic precipitation agents, such as TFA, TCA, HClO4, H2SO4, ZnSO4 or CHCl3, are used for plasma protein precipitation. The transformation degree depends on the temperature of the GC injector, the concentration of the precipitation agent and the incubation time of plasma with the precipitating agent. At the CBD plasma concentration equal to 50 ng/ml, which is approximately the mean level for patients treated for epileptic syndromes, the CBD transformation degree can exceed 20%. For a reliable estimate of CBD in blood plasma, neutral precipitation agents (e.g. ACN, MeOH, acetone) should be used when plasma deproteinization precedes GC analysis. The presented results are important not only for analysts cooperating with pharmacologists and for medicine doctors examining the activity of CBD-containing drugs in the therapeutic process, but also for forensic scientists who may erroneously find innocent people guilty of using marijuana or its preparations.

Application of the QuEChERS procedure for analysis of Δ9-tetrahydrocannabinol and its metabolites in authentic whole blood samples by GC-MS/MS.

PURPOSE: Analysis of drugs and their metabolites in biofluids usually demands the application of sample preparation methods that allow for full isolation of analyzed substances from the matrix. The purpose of this study was to develop a method using the QuEChERS procedure for analysis of Δ9-tetrahydrocannabinol (THC), 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (11-COOH-THC). METHODS: THC, 11-OH-THC and 11-COOH-THC were quantified in whole blood samples using QuEChERS extraction and gas chromatography-tandem mass spectrometry. RESULTS: The described method is characterized by good linearity, very low detection limits and satisfactory inter- and intraday precisions for THC, 11-OH-THC and 11-COOH-THC. The applicability of the procedure was confirmed using authentic whole blood samples collected from 30 persons suspected of driving under the influence of drugs. CONCLUSIONS: The application of QuEChERS extraction described herein is a simple and convenient method for the routine analysis of THC, 11-OH-THC and 11-COOH-THC in whole blood samples from living and deceased humans. To our knowledge, this paper is the first academic report describing the QuEChERS extraction of THC and its metabolites from whole blood specimens.

Modified headspace solid-phase microextraction for the determination of quantitative relationships between components of mixtures consisting of alcohols, esters, and ethers - impact of the vapor pressure difference of the compounds.

The quantitative relationship between analytes established by the headspace solid-phase microextraction procedure for multicomponent mixtures depends not only on the character and strength of interactions of individual components with solid-phase microextraction fiber but also on their vapor pressure in the applied headspace solid-phase microextraction system. This study proves that vapor pressure is of minor importance when the sample is dissolved/suspended in a low-volatility liquid of the same physicochemical character as that of the used solid phase microextraction fiber coating. It is demonstrated for mixtures of alcohols, esters, ethers and their selected representatives by applying a headspace solid-phase microextraction system composed of Carbowax fiber and sample solutions in polyethyleneglycol. The observed differences in quantitative relations between components of the examined mixtures established by their direct analysis and by modified headspace solid-phase microextraction are insignificant (Fexp  < Fcrit ). It is explained by a significant diminution in vapor pressure difference between individual components of the examined mixture in the applied headspace solid phase microextraction system due to low components concentration in polyethyleneglycol suspensions (Raoult's law) and due to strong specific interactions of analyte molecules with polyethyleneglycol molecules.

Modified HS-SPME for determination of quantitative relations between low-molecular oxygen compounds in various matrices.

Similar quantitative relations between individual constituents of the liquid sample established by its direct injection can be obtained applying Polydimethylsiloxane (PDMS) fiber in the headspace solid phase microextraction (HS-SPME) system containing the examined sample suspended in methyl silica oil. This paper proves that the analogous system composed of sample suspension/emulsion in polyethylene glycol (PEG) and Carbowax fiber allows to get similar quantitative relations between components of the mixture as those established by its direct analysis, but only for polar constituents. It is demonstrated for essential oil (EO) components of savory, sage, mint and thyme, and of artificial liquid mixture of polar constituents. The observed differences in quantitative relations between polar constituents estimated by both applied procedures are insignificant (Fexp < Fcrit). The presented results indicates that wider applicability of the system composed of a sample suspended in the oil of the same physicochemical character as that of used SPME fiber coating strongly depends on the character of interactions between analytes-suspending liquid and analytes-fiber coating.