Ketones, detection identification

Many impurities are present in commercial caprolactam which pass into the liquid wastes from PCA manufacture from which caprolactam monomer may be recovered. Also, the products of die thermal degradation of PCA, dyes, lubricants, and other PCA fillers may be contained in the regenerated CL. Identification of die contaminants by IR spectroscopy has led to the detection of lower carboxylic acids, secondary amines, ketones, and esters. Aldehydes and hydroperoxides have been identified by polarography and thin-layer chromatography. 

The identification and quantification of potentially cytotoxic carbonyl compounds (e.g. aldehydes such as pentanal, hexanal, traw-2-octenal and 4-hydroxy-/mAW-2-nonenal, and ketones such as propan- and hexan-2-ones) also serves as a useful marker of the oxidative deterioration of PUFAs in isolated biological samples and chemical model systems. One method developed utilizes HPLC coupled with spectrophotometric detection and involves precolumn derivatization of peroxidized PUFA-derived aldehydes and alternative carbonyl compounds with 2,4-DNPH followed by separation of the resulting chromophoric 2,4-dinitrophenylhydrazones on a reversed-phase column and spectrophotometric detection at a wavelength of378 nm. This method has a relatively high level of sensitivity, and has been successfully applied to the analysis of such products in rat hepatocytes and rat liver microsomal suspensions stimulated with carbon tetrachloride or ADP-iron complexes (Poli etui., 1985). 

Identification of pyridoxal phosphate as coenzyme suggested the aldehyde group on pyridoxine might form an intermediate Schiff s base with the donor amino acid. Pyridoxamine phosphate thus formed would in turn donate its NH2 group to the accepting a-ketonic acid, a scheme proposed by Schlenk and Fisher. 15N-labeling experiments and, later, the detection of the Schiff s base by its absorption in UV, confirmed the overall mechanism. Free pyridoxamine phosphate however does not participate in the reaction as originally proposed. Pyridoxal phosphate is invariably the coenzyme form of pyridoxine. 

In recycled PP, 61 compounds were detected and 35 of them were identified. Many peaks showed very low separation levels making their identification difficult. In virgin and recycled PP the following compounds were identified Ethylbenzene and xylene were found only in the recycled resin. Present in both virgin and recycled PP were a large number of branched alkanes and n-alkanes between Qg and C25. Octadecanoic acid, methyl ester and dibutyl palmitate, which is a typical compound used in the cosmetic industry, were found only in the recycled PP. Amines such as hexamine, 3-ethyl and NIN"N" trimethyl dipropylene triamine were identified in both PP materials. Carboxylic acids and ketones were absent in both polymeric materials and so were fragrance or flavour compounds [113]. 

Fig. 10.4. Separation of three types of ketones in 50 mM Tris-HCl buffer, pH 7.3 as the mobile phase with the poly(TBAAm-co-AMPS)-coated column. Conditions column, 750 mm x 25 pm i.d. (600 mm effective length) mobile phase, 50 mM Tris-HCl buffer, pH 7.3 field strength, 400 V/cm injection, 12 kV for 1 s at the side of the anode detection wavelength, 254 nm. Peak identification 1, acetone 2, acetophenone 3, butyrophenone. Reproduced with permission from Sawada and Jinno [11].

MCD measurements are useful not only in purely spectroscopic investigations, for example, in the detection of hidden absorption bands or for the identification of degenerate absorptions, but also in structural organic chemistry. There is, for instance, a rule that describes the influence of the molecular environment on the MCD effect of the n- r band of a ketone (Seamans et al., 1977 Linder et al., 1977). However, the method is clearly most useful for investigating cyclic conjugated n systems. 

The 2-D TLC was successfully applied to the separation of amino acids as early as the beginning of thin-layer chromatography. Separation efficiency is, by far, best with chloroform-methanol-17% ammonium hydroxide (40 40 20, v/v), n-butanol-glacial acetic acid-water (80 20 20, v/v) in combination with phenol-water (75 25, g/g). A novel 2-D TLC method has been elaborated and found suitable for the chromatographic identification of 52 amino acids. This method is based on three 2-D TLC developments on cellulose (CMN 300 50 p) using the same solvent system 1 for the first dimension and three different systems (11-IV) of suitable properties for the second dimension. System 1 n-butanol-acetone -diethylamine-water (10 10 2 5, v/v) system 11 2-propanol-formic acid-water (40 2 10, v/v) system 111 iec-butanol-methyl ethyl ketone-dicyclohexylamine-water (10 10 2 5, v/v) and system IV phenol-water (75 25, g/g) (h- 7.5 mg Na-cyanide) with 3% ammonia. With this technique, all amino acids can be differentiated and characterized by their fixed positions and also by some color reactions. Moreover, the relative merits of cellulose and silica gel are discussed in relation to separation efficiency, reproducibility, and detection sensitivity. Two-dimensional TLC separation of a performic acid oxidized mixture of 20 protein amino acids plus p-alanine and y-amino-n-butyric acid was performed in the first direction with chloroform-methanol-ammonia (17%) (40 40 20, v/v) and in the second direction with phenol-water (75 25, g/g). Detection was performed via ninhydrin reagent spray. 

Odor compounds may also be released from the plastic materials used in cars. The variety of plastics and possible chemical compounds is broad, which makes the identification of odor causing compounds an extremely comphcated task. An effective and rapid screening of VOCs and semi-VOCs from materials used in automobiles was developed by utihzing the SPME technique [28]. The low molecular weight compoimds extracted from five different automobile materials included different benzene derivatives, aldehydes, esters, biphenyls, phthalates, butylated hydroxytoluene, phenols, alcohols, styrene, triethylene-diamine, carboxylic acids and ketones. A considerable munber of VOCs and semi-VOCs were detected, indicating that more attention should be paid to the selection of materials and additives for automotive parts. 

Abundant Cis isoprenoid ketone, Z/E pristenal, and Z/E phytenal as well as phytol biomarker compounds were detected in the sinking particulate materials from the Yongshu Reef Lagoon and the continental shelf of the East China Sea (Figs. 5.28 and 5.29). This appears to be the first report of these compounds in China marine environment. Detection of these compounds in the studied regions is of some importance to understand the evolutional processes of acyclic isoprenoid compounds in the seawater column and their formative pathways in marine sediments. Their identifications were based on chromatographic retention time, mass spectrum features (Figs. 5.28 and 5.29), and comparison with those reported previously. The mass spectrum of phytol trimethylsilyl ether exhibits a base peak at mlz 143 and a molecular ion at mjz 368. Cig isoprenoid ketone has a base peak at mjz 58, a molecular... 

In aliphatic or aromatic hydrocarbons, alcohols may be detected sensitively on the basis of the strongly infrared-active OH bands, as may aldehydes or ketones on the basis of the similarly high-intensity CO bands the presence of organic amines is revealed by the NH bands, and that of nitriles by the CN bands. These same bands may be used, although with lower sensitivity, for the determination of aldehyde impurities in alcohols, or alcohol impurities in nitriles. The appearance of new bands in the infrared spectrum does not always lead to identification of the impurity component, but it definitely draws attention to the contaminated nature of the solvent. 

A number of hydrocarbons were photolysed in a reaction vessel according to the system described by Prof. Wameck, MPI Mainz. Measurements were made with fluorometric and polarographic detection. The photolysis experiment were reproducible with a standard deviation of 3-6 %. Several hydroperoxides could be identifred by "cross"-identifications by comparing the retention times of different photolysed hydrocarbons, aldehydes, ketones and alcohol s with the unknown peaks. 

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.)...

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