Gas Chromatography

Halitosis is an unpleasant condition that may be the origin of concern not only for a possible health condition but also for frequent psychological alterations which may lead to social and personal isolation. The most frequent sources of halitosis that exist in the oral cavity include bacterial reservoirs such as the dorsum of the tongue, saliva and periodontal pockets. Volatile sulphur compounds (VSCs) are the prominent elements of oral malodour. Genuine halitosis and pseudo-halitosis should be in the treatment realm of dental practitioners. Clinical Relevance: Halitosis can be a symptom of underlying systemic disease, therefore the exact diagnosis and its source (oral or non-oral) is important in the proper approach to its management.

Ethyl glucuronide (EtG) is a minor and direct metabolite of ethanol. EtG is incorporated into the growing hair allowing retrospective investigation of chronic alcohol abuse. In this study, we report the development and the validation of a method using gas chromatography–negative chemical ionization tandem mass spectrometry (GC–NCI-MS/MS) for the quantification of EtG in hair. EtG was extracted from about 30mg

Fatty acid composition of human milk (HM) is known to change considerably during lactation. However, we were unable to find data on changes of fatty acid composition of HM during the very early phase of lactation, i.e. in the first week of life. HM samples were obtained from 18 healthy lactating women every day during the first week and thereafter on the 14th and 28th days of lactation. Fatty acid composition of colostrum and mature HM samples was determined by high-resolution capillary gas-liquid chromatography. Values of the n-6 essential fatty acid, linoleic acid, in HM did not change significantly during the first month of lactation, whereas values of the n-3 essential fatty acid, alpha-linolenic acid, showed significant increases during the first 2 weeks of lactation (1st day: 0.49 [0.12], % weight/weight, median [ranges from the 1st to the 3rd quartile], 14th day: 0.69 [0.31], p < 0.05). In contrast, values of the n-6 long-chain metabolites, eicosadienoic-, dihomo-gamma-linolenic- and arachidonic acid, as well as the values of the n-3 long-chain metabolites, eicosatrienoic-, and eicosapentaenoic acid exhibited significant decreases during the entire period investigated. The principal n-3 long-chain metabolite, docosahexaenoic acid, showed a significant increase between the 3rd and 14th days, but a significant decrease between the 14th and 28th days (3rd day: 0.15 [0.13], 14th day: 0.28 [0.11], p < 0.05, 28th day: 0.19 [0.12], p < 0.01). There were statistically significant positive correlations between arachidonic and docosahexaenoic acid values on the 1st (r = 0.67, p < 0.01), 5th (r = 0.56, p < 0.05) and the 6th (r = 0.53, p < 0.05) days of lactation. Fatty acid composition of HM changes significantly even during the first week of lactation. The lack of positive correlation between essential fatty acids and their long-chain metabolites suggests that it is not only the availability of essential fatty acids that influences the fatty acid composition of human colostrum.

The purpose of the study was to optimise analytical methods for determination of the chemical speciation of mercury in studies of protective mechanisms of selenium. Optimisation of the methods was performed using CRM DOLT-2 (Dogfish liver), both in its original form and after separation of various fractions. The sample was homogenised with 10 mM Tris-HCl buffer (pH 7.6) and ultracentrifuged. The soluble phase obtained was applied to a size exclusion chromatography column (Sephadex G-75 column) for separation of various protein fractions. Total mercury (total Hg), monomethyl mercury (MeHg) and selenium (Se) were determined in whole dogfish liver tissue and its soluble and insoluble phases (pellet). Different approaches for determination of total Hg and MeHg were compared. Simultaneous determination of MeHg and inorganic mercury (Hg2+) was based on alkaline dissolution and/or acid leaching, followed by ethylation, room temperature precollection, isothermal gas chromatography (GC), pyr...

Dry powder formulations are often composed of fine drug particles and coarser carrier particles, typically alpha-lactose monohydrate. However, the performance of a powder formulation may be highly dependent on the lactose quality and source. This study investigated the characteristics of lactose that influence the drug-to-carrier interaction and the performance of lactose-based dry powder inhaler formulations. The selected lactoses differed in the preparation processes and the content of fine lactose particles. Efficiency testing was done using fluticasone propionate and terbutaline sulphate as model drugs. Inverse gas chromatography was used to determine the surface heterogeneity distribution of different energy sites of the lactose and to understand the mechanism by which the fine carrier particles can improve the performance of dry powder inhalers. To assess the adhesion of respirable-sized drug to carrier particles, a simple method was developed based on aspiration and consideri...

ABSTRACT The alkane pattern of leaf waxes from 24 tropical Ficus species in Nigeria was determined by gas chromatography and gas chromatography–mass spectrometry. Of the 12 alkanes identified, hentriacontane and tritriacontane were the major components in all the species studied. The chemosystematic significance of leaf alkanes is discussed in Ficus for the first time. There is an indication that alkane occurrence in Ficus could provide useful information to the understanding of species variability.

Molecular and tissue damage induced by reactive oxygen species is a serious consequence of the production of free radicals in biological systems. Biological markers produced by reactions with hydroxyl radicals are useful indices of free radical processesin vivo.In this respect, hydroxylation of aromatic compounds such as salicylate (2-hydroxybenzoate) has been used extensively as a measure of hydroxyl radical formation. 4-Hydroxybenzoate

Two still-life paintings were scientifically examined in order to gain insights about Dutch painter Jan van Huysum's (1682-1749) purportedly secretive paintings techniques, comparing the actual works to information obtained in the few available historical technical sources. Surface investigations included macroscopic and microscopic examination, infrared reflectography and x-radiography, while material characterization of the ground, organic and inorganic pigments and binding media was carried out with a range of non-destructive and destructive analytical techniques. The belief that the two works were an original pair of pendant paintings was disproved due to substantial technical differences in the wood support, ground layers and use of yellow pigment. It was also found that Van Huysum's use of newly developed pigments (Prussian blue, Naples yellow) had lead to changes in his painting technique, which no longer corresponded to those described in the period's manuals, an...