Degradation products polar/nonpolar

Cyclohexadienones. The perturbation of the electronic absorption spectra by adsorption on silica gel can have a significant effect on subsequent photochemical reactions. For example, Hart has shown that 2,4-cyclo-hexadienones photochemically degrade cleanly in nonpolar solvents to a ketene (1) but in highly polar solvents or adsorbed on silica gel bicyclic ketone (2) is the predominant product.33 The absorption spectra indicate that in nonpolar solvents the lowest singlet state is the n,n state, from which the formation of the ketene proceeds. This n -n band is obscured by the band in polar media, inversion of the energy levels of the n,n, and the first... 

Some degradation products are either very polar or very nonpolar in nature this may present an issue in chromatography, where they may not be retained or strongly adsorbed on the column, respectively. One may also want to double check the reference standard for its purity, moisture content, and/or salt/ acid-base ratio for calculation. An analytical chemist must remember to explore all possibilities if mass balance issue is observed (either during method development, validation and/or stability testing). 

Some triazines, including atrazine and simazine, were extracted from water by SEE after preconcentration on sohd-phase extraction disks.The freeze-dried residue or SPE disk was then introduced into the extraction cell and eluted with either pure CO2 or methanol or acetone-modified CO2. SEE has been applied in combination with online sohd-phase extraction for pesticides, including triazines. However, this technique is still used mainly on solid matrixes. The main limitation with aqueous matrixes remains the miscibility of water with supercritical carbon dioxide. Recoveries of nonpolar pesticides, extracted by SEE technique using octacedyl-bonded silica, are generally effective with CO2 elution alone. This is not the case for semipolar and polar compounds, such as triazines and their degradation products. For example, the addition of... 

Sorbent-analyte interactions fall into three categories nonpolar, polar, and ionic. Nonpolar sorbents are generally selected for extracting triazines from water. By contrast, degradation products containing polar functional groups such as, hydroxyl, carbonyls, amines, and sulfhydryls, need polar sorbents. 

In pharmaceutical preparations, panthenol can be determined as a volatile derivative or as derivatives of its degradation products. Most commonly employed are acetyl and trimethylsilyl derivatives. The same derivatization procedures used for the acetylation of pantothenic acid can be employed for the conversion of panthenol into its triacetate, which can then be analyzed on polar stationary phases. Similarly, a tris(trimethylsilyl) ether of panthenol may be prepared using the derivatization procedures previously described. In addition, a 3 6 2 (v/v/v) mixture of TMCS-HMDS-dioxane (35°C, 100 min) has been used. Nonpolar po-lymethylsiloxanes are the stationary phases of choice. 

Mono- and dicarboxylic acids were the major products identified in both environments. Ketoacids were formed in both air and water but hydrocarbons and ketones were only identified after aging in air. Blends without pro-oxidants did not form any degradation products. By a liquid phase (diethyl ether) and a solid phase (nonpolar dimethylsiloxane and polar carbowax fibers) extraction followed by GC-MS with derivatization of products (methanize dicarboxylic acids) the following products were identified— Table 2. 

Molinate has a low toxicity to rats, oral LDso=720 mg/kg, and is rapidly metabolized by plants to CO2 (1) (5) and naturally occurring plant constituents (1). Molinate is also readily metabolized by soil microorganisms (6). After incubation of molinate with Bacillus sp. 24, Nocardia sp. 119, and Micrococcus sp. 22r which were isolated from Russian garden soils and rice field drains (7,8), it was found that molinate was completely degraded into various hydroxy and oxidized products in the medium. Molinate can be metabolized to its corresponding sulfoxide in the mouse in vivo and by the microsome-NADPH system of mouse liver (9, 10). Hubbell et al. (11) and DeBaun et al. (12) also found molinate sulfoxide along with other polar and nonpolar metabolites in rat urine. 

---