Glycols, analysis

Gotoh, Y., Tsukada, M., and Minoura, N. (1993) Chemical modification of silk fibroin with cyanuric chloride-activated polyethylene glycol Analysis of reaction site by 1H-NMR spectroscopy and conformation of the conjugates. Bioconjugate Cbem. 4, 554-559. 

D.H. Atha, K.C. Ingham, Mechanism of precipitation of proteins by polyethylene glycols analysis in terms of excluded volume, J. Biol. Chem. 256(1981) I2I08-I2II7. 

Figure 1.16 Glycols analysis of a) standard solution, b) wine. 1. levo-...

Oxidation of a glycol can lead to a variety of products. Periodic acid quantitatively cleaves 1,2-glycols to aldehydes and is used as an analysis method for glycols (12,13). The oxidation of propylene glycol over Pd/C modified with Pb, Bi, or Te forms a mixture of lactic acid, hydroxyacetone, and pymvic acid (14). Air oxidation of propylene glycol using an electrolytic crystalline silver catalyst yields pymvic aldehyde. 

Vanillin, being an aldehyde, is able to form acetals and hemiacetals. Therefore, in flavor formulations using high concentrations of vanillin in conjunction with carriers such as propylene glycol, a glc analysis often shows a reduced vanillin peak after storage of the compounded flavor, and the presence of new peaks indicating acetal formation. Addition of about 0.5% of water to the formula reverses the reaction, ie, there is a reduction of acetal, and the reappearance of vanillin peaks. 

Choline Bitartrate. This substance [87-67-2] is a white crystalline material possessing an acid taste. It melts at 149—I53°C. Analysis by cobaltous chloride shows more than 99% as the bitartrate. Free ethylene glycol is less than 0.25%, with free alkaU at 0.0%. 

The formation of acetals with methanol, ethanol, or ethylene glycol in the presence of an acid catalyst such as hydrogen chloride or ben2enesulfonic acid is straightforward. Sodium bisulfite and hydroxjlamine form adducts with cinnamaldehyde that are used in typical quantitative analysis protocols. 

The submitters state that gas chromatographic analysis was made on a 2-m. column packed with polypropylene glycol (LB-550-X... 

The most demanding test of cesium carbonate as base was with 2,3-dihydroxypyridine (3-hydroxypyridone). The cesium salt was found to be fairly unstable, apparently oxidizing quite rapidly. Model reactions suggested that alkylation would occur 1,3 (N, 0) to give the substituted pyridone. Nevertheless, on the basis of UV and H-nmr analysis, the product of reaction between 2,3-dihydroxypyridine and tetraethylene glycol dibromide was assigned as the pyridocrown (23% yield, mp 77—78.5°) as shown in Eq. (3.60). 

Figure 4.25 (page 122) shows results obtained on TSK-GEL SW and TSK-GEL PW columns for low molecular weight polyethylene glycol (PEG) oligomers and high molecular weight dextrans. The TSK-GEL G2000PW column successfully resolved components of PEG 200, whereas the TSK-GEL G2000SW column did not (Fig. 4.25A). Therefore, the TSK-GEL G2000PW column would be preferable for this analysis.

Deionized water can be used as an eluent for the analysis of nonionic polymers such as pullulan and polyethylene glycol. However, in most cases, salt solutions or buffer solutions are used to decrease ionic or other interactions between samples and the stationary phase or to prevent sample association (Eigs. 6.22 and 6.23, pages 196 and 197). 

Bums and Hazzan demonstrated tlie use of event tree and fault tree analysis in tlie study of a potential accident sequence leading to a toxic vapor release at an industrial chemical process plant. The initiator of tlie accident sequence studied is event P, the failure of a plant programmable automatic controller. Tliis event, in conjunction willi the success or failure of a process water system (a glycol cooling system) mid an operator-manual shutdown of tlie distillation system produced minor, moderate, or major release of toxic material as indicated in Fig. 21.4.1. The symbols W, G, O represent tlie events listed ... 

In Section 21.4 tlie effects of the release of toxic vapors were considered in connection witli an accident sequence initiated by the failure of a plant programmable automatic controller. In tliis study, event tree analysis and fault tree analysis led to identification of tlie glycol cooling system circulation pumps as components meriting high priority for inspection. 

Figure 12.18 LC-SFC analysis of mono- and di-laurates of poly (ethylene glycol) ( = 10) in a surfactant sample (a) normal phase HPLC trace (b) chromatogram obtained without prior fractionation (c) chromatogram of fraction 1 (FI) (d) chromatogram of fraction 2 (F2). LC conditions column (20 cm X 0.25 cm i.d.) packed with Shimpak diol mobile phase, w-hexane/methylene chloride/ethanol (75/25/1) flow rate, 4 p.L/min UV detection at 220 nm. SFC conditions fused-silica capillary column (15 m X 0.1 mm i.d.) with OV-17 (0.25 p.m film thickness) Pressure-programmed at a rate of 10 atm/min from 80 atm to 150 atm, and then at arate of 5 atm/min FID detection. Reprinted with permission from Ref. (23).

IR analysis can also be used quantitatively to determine the EO-PO ratio [12]. Using mixtures of polyethylene glycol and polypropyene glycol as calibration standards, the ratio of two absorbances, one due to the methyl group of the PO unit (e.g., the C-H stretch band at 2975 cm ) and one due to the methylene group (e.g., the C-H stretch band at 2870 cm ), are plotted against percent of PO content. The ratio of the same two absorbances taken from the IR spectrum of a poloxamer may then be used to determine its percent of PO content by interpolation. 

Based on this analysis it is evident that materials which are biaxially oriented will have good puncture resistance. Highly polar polymers would be resistant to puncture failure because of their tendency to increase in strength when stretched. The addition of randomly dispersed fibrous filler will also add resistance to puncture loads. From some examples such as oriented polyethylene glycol terephthalate (Mylar), vulcanized fiber, and oriented nylon, it is evident that these materials meet one or more of the conditions reviewed. Products and plastics that meet with puncture loading conditions in applications can be reinforced against this type of stress by use of a surface layer of plastic with good puncture resistance. Resistance of the surface layer to puncture will protect the product from puncture loads. An example of this type of application is the addition of an oriented PS layer to foam cups to improve their performance. 

Due to the differences in the values relative to any one system, conclusions cannot easily be drawn from the activation parameters listed in Table 3. However, an analysis of the results relative to 1,2-ethanediol, 2,2-dimethyl-l,3-propanediol, 1,5-pentanediol, 1,10-decanediol and diethylene glycol shows that a slight difference can be observed between aromatic and aliphatic acids the activations enthalpies and entropies are in the ranges 70, 100 kJ mol"1 and -SO, -130 J K"1 mol-1 for aromatic acids, and in the ranges 50, 70 kJ mol"1 and -200, -100 J K"1 mol-1 for the aliphatic acids. 

The thin-layer technique (CA 60, 6691) utilizes aliquots of proplnt ether extract (I) and the ether soln (II) of a known mixt. II consists of nitrates of glycerol and glycol, di-Bu or di-Et phthalates, Et or Me centralites, DNT, and diphenylamine. The chromatoplates are made of 85 15 silica gel and plaster of Paris. These plates, containing spots of I and 11, are developed with 1 1 C6H6-petroleum ether, then sprayed with specific detectors by color. The method is much quicker and easier than chemical analysis and simpler than infrared spectroscopy and column chromatography... 

Tannins may be found bound up with magnetite in waterside tube deposits. Degradation products of amines, glycols, polymeric dispersants, chelants, and other organics may also be found and usually are reported in the deposit analysis as a loss on ignition. 

Gas chromatographic analysis at 120° on a 2.2-m. column packed with 10% diethylene glycol succinate showed the forerun fraction to contain approximately 50% product. The other fraction is pure 2,3-epoxycyclohexanone. 

Gas chromatographic analysis was performed on a 2.2-m. 10% diethylene glycol succinate column at 80°. 

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