Polar trace compounds

Polar trace compounds, such as sotolon and furaneol, are often directly determined by GC-MS of a polar extract obtained directly from wine (Cutzach et al. 1998 Camara et al. 2004 Moreno et al. 2005). However, this strategy only works when the compounds reach relatively high concentrations. For a determination at lower concentrations, a selective SPE isolation procedure has been proposed (Ferreira V et al. 2003a)... 

Chian et al. [69] point out that the Bellar and Iichtenberg [65] procedure of gas stripping followed by adsorption onto a suitable medium and subsequent thermal desorption onto a gas chromatograph-mass spectrometer is not very successful for trace determinations of volatile polar organic compounds such as the low molecular weight alcohols, ketones, and aldehydes. To achieve their required sensitivity of parts per billion, Chian et al. [69] carried out a simple distillation of several hundred ml of sample to produce a few ml of distillate. This achieved a concentration factor of between 10 and 100. The headspace gas injection-gas chromatographic method was then applied to the concentrate obtained by distillation. 

Hennion MC, Coquart V. 1993. Comparison of reverse-phase extraction sorbents for the on-line trace enrichment of polar organic compounds in environmental aqueous samples. J Chromatogr 642 211-224... 

Derivatization After Desorption. Alkanolamines, highly polar basic compounds, present a difficult analytical problem. Although direct gas chromatographic separations can be achieved, this technique is not applicable to trace analysis due to sorption problems at trace concentrations. A derivatization/gas chromatographic procedure has been developed for the determination of alkanolamines in air as low as 100 ppb (54,55). The samples are collected on activated alumina and desorbed with an aqueous solution of 1-octanesulfonic acid. The... 

In order to separate and identify the various substanaes in the column, each zone is cut off at the borders with a knife and treated with a polar solvent to dissolve the adsorbed compds. After sepg, by filtration, each soln from the material of column, the solvent is removed by evaporation and the residue is weighed and identified by chemical means. If, in chromatographing colorless compds, there is no satisfactory streak reagent available, a colored tracing compound may be used (Ref 58,p 54). For example, in the sepn of... 

Polar organic compounds, VOCs, metals, trace elements... 

The values for lauric acid, stearic acid, and stearyl alcohol are 5 to 7 dynes/cm. higher than those reported previously. This probably reflects a difference in the purity of the mercury used rather than the polar fatty compounds. Very small traces of metallic impurities in mercury have been shown to alter its surface properties greatly. 

Coquart, V. Hennion, M.C. Trace level determination of polar phenolic compounds in aqueous samples by high-performance liquid chromatography and on-hne preconcentration on porous graphitic carbon. J. Chromatogr., A. 1992, 600 (2), 195 - 201. 

International Sorbent Technology, SBD-1 from J. T. Baker, and the Oasis HLB poly(divinylbenzene-co-A-vinylpyrrolidone) polymer of Waters. All of these polymers contain some trace of hydrophilic character to improve their wetting characteristics for good mass transfer, but yet the polymers still have high capacities for polar organic compounds. 

Most of the work to date has been done using relatively few mobile phases (n-pentane, carbon dioxide, and nitrous oxide). Future efforts are needed to explore the use of other more polar and/or mixed mobile phases. Furthermore, column surface deactivation has become more important as emphasis has focussed more on the analysis of polar and trace compounds. The greatly increasing... 

Phenoxy carboxylic acids. The application of APCI in the determination of the polar acidic phenoxycarboxyHc acids led to unsatisfactory results. Nevertheless this method was apphed by Santos et al. [348] for the determination of the 2,4-D, MCPA and MCPP herbicides and their degradation products in trace quantities in estuarine waters of drainage of the Ebro delta. Response for the very polar acidic compounds preferentially ionised by ESI in the negative mode with excellent sensitivity [176, 325] in the APCI mode, however, was reduced (cf. 15.3.3.2 ESI, orga-nophosphones compounds) [348]. Results obtained by APCI or PBl, however, proved an increased sensitivity of APCI compared to PBl [320]. 

Composition Genuine essential oils consist exclusively of volatile components with boiling points mainly between 150 and 300 °C. They contain predominantly hydrocarbons or monofunctional compounds such as aldehydes, alcohols, esters, ethers, and ketones. Parent compounds are mono- and sesquiterpenes, phenylpropane derivatives, and longer-chain aliphatic compounds. Accordingly, essential oils are relative non-polar mixtures, i.e., they are soluble in most organic solvents. Often the organoleptic properties are not determined by the main components but by minor and trace compounds such as, e.g., 1,3,5-undecatrienes and pyrazines in galbanum oil. In many of the commercially important oils, the number of identified components exceeds 100. Very many of the constituents are chiral, frequently one isomer predominates or is exclusively present, e. g., (- )-menthol in peppermint oils or (-)-linalyl acetate in lavender oil. 

LTP probe was used to continuously monitor ongoing condensation of ethylenediamine with aldehyde within a few tens of seconds [60], This approach can monitor reactants and products including polar and non-polar organic compounds. Furthermore, only trace amounts of the reaction species lifted and ionized by the LTP are sufficient for MS analysis. Therefore, the common contamination problems occurring in on-line monitoring MS can be reduced using this approach. 

A variable pressure oil pump was used in this distillation. Approximately 10 g of a volatile component, consisting mostly of hexamethyl-disiloxane, was obtained at room temperature (15 (in) before the forerun. The forerun contained the desired product and mineral oil from the n-butyllithium solution. The pot residue was about 5 g. The submitters find the disilyl compound thus obtained is contaminated with a trace amount of mineral oil and 4-6% of a vinylsilane, probably 2-methyl-l-trimethylsiloxy-3-trimethylsilyl-2-propene. This impurity becomes quite significant if the reaction medium is less polar than the one described (e.g., too much hexane from n-butyllithium is allowed to remain behind). The spectral properties of the desired product... 

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