Glycerol detection

In the following examples, pinacol is oxidised to acetone, which is identified as its semicarba2one and its 2,4 dinitrophenylhydra2one, and glycerol is oxidised to formaldehyde and formic acid. The formaldehy de is readily detected by the condensation product which it gives with dimedone, 5,5-dimethylcyclohexan-i,3-dione (p, 277). 

I. Acrolein test. Heat 0-5 ml. with about i g. of finely powdered KHSO4. Acrolein, CH2 CH CHO, produced by dehydration of the glycerol, is readily detected by its characteristic and irritating odour smell cautiously). 

Mass spectral analysis of quaternary ammonium compounds can be achieved by fast-atom bombardment (fab) ms (189,190). This technique rehes on bombarding a solution of the molecule, usually in glycerol [56-81-5] or y -nitroben2yl alcohol [619-25-0], with argon and detecting the parent cation plus a proton (MH ). A more recent technique has been reported (191), in which information on the stmcture of the quaternary compounds is obtained indirectly through cluster-ion formation detected via Hquid secondary ion mass spectrometry (Isims) experiments. 

Cherry and Crandall in 1932 (86) used olive oil as substrate with gum acacia as the emufsTfier. This method has served as the basis for a number of modifications that increased the stability of the emulsion, decreased incubation time and gave better precision. When a serum sample is incubated with a stabilized olive oil emulsion, lipase acts at the interface of substrate and water to hydrolyze olive oil into fatty acid plus diglycerides, and to a small extent to monoglycerides and glycerol. The bile salt sodium deoxycholate activates the reaction. These methods measure the liberated fatty acids by titration with a standardized NaOH solution. An indicator such as phenolphatalein, thymolphthalein or methyl red or a pH meter are used to detect the end point. 

Several supported metalhc catalysts were evalrrated for the selective hydrogenolysis of glycerol. Initially, the reactions were performed tmder acidic conditions in order to promote the formation of 1,3-PDO. Rutheniirm-based catalysts were found to be the most active catalysts but significant amount of tmdesired products resulted from C-C cleavages were detected. On the contrary, Rh/C catalysts were found selective to C-O cleavages. As far as the selectivity to 1,3-PDO was concerned, we previously reported that the addition of iron salts in the medium improved the l,3-PDO/l,2-PDO selectivity (11). A systematic study on the influence of additives was therefore carried out in the present investigation. Mineral and organic acids were evaluated for this purpose (Table 35.1). 

Acetic or trifluoroacetic acids gave a very low glycerol conversion and no traces of 1,3-PDO could be detected. When the reaction was performed in the... 

The hydrogenolysis of glycerol was studied over a large range of pH in order to determine the optimal pH value at which the higher reaction rate and selectivity to 1,2-PDO are obtained. Selected results are summarized in Table 35.2. In the presence of Rh/C and under neutral conditions (pHi = 5.5), a low conversion of glycerol was achieved (< 4%) after 48 h. The main product was 1,2-PDO, but EG, 1-propanol, ethanol and 1,3-PDO were also detected. Increasing the initial pH from 5.5 to 12.0 had beneficial effects both on the conversion and selectivity. The selectivity to EG decreased from 13% under neutral condition to less than 1% while the selectivity toward the desired 1,2-PDO increased from 52% to 96%. 

Glycerol monostearate can also be determined by LC-MS. Detection by positive APCI is possible. Figure 15 shows a typical chromatogram for the technical product eluting from a Phenomenex Aqua Ci8 column with methanol-water gradient (70-100% methanol). The molecular ion (M + H)+ mass spectra of the two main peaks detected are shown in Figures 16 and 17. 

The pyrolysis of glycerolipid materials requires the use of a suitable derivatising agent, in order to increase the detectability of fatty acids and dicarboxylic acids, which may be present in a mature paint film as free acids, metal soaps, as well as esterified with glycerol. The oils and fats commonly used in samples from works of art have been analysed by means of pyrolysis using TMAH [12,23,25,26,32 38], and HMDS [37,39]. 

Northern crayfish, Orconectes viritis 101 pg/L for 7 days Acrolein not detected in tissues glycerol and lactic acid were the major metabolites 25... 

Fast librational motions of the fluorophore within the solvation shell should also be consideredd). The estimated characteristic time for perylene in paraffin is about 1 ps, which is not detectable by time-resolved anisotropy decay measurement. An apparent value of the emission anisotropy is thus measured, which is smaller than in the absence of libration. Such an explanation is consistent with the fact that fluorescein bound to a large molecule (e.g. polyacrylamide or monoglucoronide) exhibits a larger limiting anisotropy than free fluorescein in aqueous glycerolic solutions. However, the absorption and fluorescence spectra are different for free and bound fluorescein the question then arises as to whether r0 could be an intrinsic property of the fluorophore. 

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