Ethanol, detection identification

The use of mesitoate esters in the elucidation of reaction mechanisms has been pioneered by Burrows and Topping (1969,1970). This system has been used to suppress the competitive intermolecular reaction by steric bulk effects and to detect participation by the identification of the products formed. Under identical conditions (pH 11.28 at 30°C in 9.5% ethanol-water), 2-acetylphenyl mesitoate [41]is hydrolysed 130 times more readily than 4-acetylphenyl mesitoate, clearly indicating intramolecular catalysis. However, the products of hydrolysis provided no clue to the mechanism of... 

Fig. 2.54. High-performance liquid chromatography profile of a peppermint sample (gradient no.l), extracted with ethyl ether (a) and ethanol (b). Chromatographic profile of a sample extracted with ethanol (gradient no.2) (c). Detection at 320 nm. For peak identification see Table 2.55. Reprinted...

Ethanol and a long list of carbonyl compounds and aliphatic acids occur in fresh milk (Table 1.5). Some of them have been detected in only a few of the samples in which they were sought. Techniques for detecting such compounds include derivatization with 2,4-dinitrophe-nylhydrazine and various methods of volatilization, extraction, and chromatography (Harper and Huber 1956 Morr et al. 1957 Harper et al. 1961 Wong and Patton 1962 Scanlan et al. 1968 Marsili et al. 1981). The sum of the concentrations of acids listed in Table 1.5 is only 1-3 mmol/liter, compared to the citrate concentration of 10 mmol/liter. Oxalate has been reported to occur in milk (Zarembski and Hodgkin-son 1962) on the basis of a certain colorimetric reaction, but positive identification has not been made. 

A gas-solid chromatographic technique using flame ionization detection and a Porapak Q column has been used for the identification and the determination of ethanol, isopropanol, and acetone in pharmaceutical preparations. The technique involves direct injection of an aqueous dilution of the product, and therefore is simple and direct. 

Techniques such as Py-MS or Py-GC/MS are not always suitable for the identification of less volatile or highly polar compounds. HPLC analysis with MS detection provides a better tool in such cases, and it was successfully applied for lignin pyrolysate analysis (see Section 5.7). Pyrolysis products from a lignin sample from mixed hardwood, obtained using the organosolv procedure with ethanol/water and generated at 510° C in an on-line Curie point pyrolyser and analyzed by HPLC [8], indicated the presence of a series of compounds shown in Table 9.1.7. 

In comparison to equivalent optical detection methods using whole cell biosensors for water toxicity detection, these results proved to be more sensitive and produce faster response time. Concentrations as low as 1% of ethanol and 1.6 ppm of phenol could be detected in less than 10 min of exposure to the toxic chemical, whilst a recent study [11] which utilized bioluminescent E.coli sensor cells, detected 0.4 M (2.35%) ethanol after 220 min. An additional study [1] based on fluorescent reporter system (GFP), enabled detection of 6% ethanol and 295 ppm phenol after more than one hour. Cha et al [12] used optical detection methods of fluorescent GFP proteins, detected 1 g of phenol per liter (1,000 ppm) and 2% ethanol after 6 hours. Other studies [13] could not be directly compared due to different material used however their time scale for chemicals identification is hours. 

According to earlier reports, difficulties in isolating the quaternary salts in a pure state and hence in detecting the diastereomers were surmounted by chromatographic separation of their nor-bases derived by pyrolysis 21) of the muscarine chlorides under reduced pressure at 200-240°C. In this way all muscarine diastereomers were found in A. muscaria, Inocybe patouillardi, and I. rimosa (14). Later, owing to impressive developments in instrumental analytical methods, detection and identification of the alkaloids as intact cations by recording secondary-ion mass spectra (SIMS), either of intact mushroom tissue or of ethanol extracts of defatted mushroom tissue, appeared to be possible (22). 

Figure 1 Analysis of a standard volatile mixture. Column 80 m X 0.53 mm i.d. SPB-1 (5nm film). Carrier gas helium (flow rate 8.6 ml min ). Oven temperature 40°C (6 min), then to 80°C at 5°C min then to 200°C at 10°C min (run time 26 min). Injection 10pi vapor. Detector sensitivities (fsd) FID, 3.2nA ECD, 64 kHz. Peaks 1, propane 2, FC 12 3, dimethyl ether 4, isobutane 5, butane 6, BCF 7, ethanol 8, acetone 9, 2-prop-anol 10, FC 11 11, FC 113 12, halothane 13, butanone 14, hexane 15, chloroform 16, 1,1,1-trichloroethane 17, carbon tetrachloride 18, trichloroethylene 19, methyl isobutyl ketone 20, 1,1,2-trichloroethane (internal standard) 21, toluene 22, tet-rachloroethylene 23, 2,2,2-trichloroethanol 24, ethyl benzene (internal standard). (Reproduced with permission from Streete PJ, Ruprah M, Ramsey JD, and Flanagan FtJ (1992) Detection and identification of volatile substances by head-space capillary gas chromatography to aid the diagnosis of acute poisoning. Analyst 117 111 1-1127. The Royal Society of Chemistry.)...

---