Chromatographic peak identification

The specialities of chromatographic behaviour of cypermethrin, permethrin, X-cyhalothrin, deltamethrin and fenvalerate were investigated in this work. Gas chromatographic determination was cai ry out with use of packed column with stationai y phase of different polarity (OV-101, OV-210 OV-17) and capillary and polycapillary columns with non-polai ic stationary phase. Chromatographic peak identification was realized with attraction GC-MS method. 

Retention time is the primary means for chromatographic peak identification. Retention time shifts are indicative of leaks, pump malfunctions, and changes in column temperature or mobile phases. 

Further chromatographic peak identification also was carried out by interfaced GC-mass spectrometry (MS) using a Hitachi-Perkin Elmer RMU6L mass spectrometer interfaced through a jet separator (Scientific Glass Engineering Pty., Melbourne, Australia). 

Amorphous and semi-crystalline polypropylene samples were pyrolyzed in He from 388°-438°C and in air from 240°-289°C. A novel interfaced pyrolysis gas chromatographic peak identification system was used to analyze the products on-the-fly the chemical structures of the products were determined also by mass spectrometry. Pyrolysis of polypropylene in He has activation energies of 5-1-56 kcal mol 1 and a first-order rate constant of JO 3 sec 1 at 414°C. The olefinic products observed can be rationalized by a mechanism involving intramolecular chain transfer processes of primary and secondary alkyl radicals, the latter being of greater importance. Oxidative pyrolysis of polypropylene has an activation energy of about 16 kcal mol 1 the first-order rate constant is about 5 X JO 3 sec 1 at 264°C. The main products aside from C02, H20, acetaldehyde, and hydrocarbons are ketones. A simple mechanistic scheme has been proposed involving C-C scissions of tertiary alkoxy radical accompanied by H transfer, which can account for most of the observed products. Similar processes for secondary alkoxy radicals seem to lead mainly to formaldehyde. Differences in pyrolysis product distributions reported here and by other workers may be attributed to the rapid removal of the products by the carrier gas in our experiments. 

Interfaced Pyrolysis Gas Chromatographic Peak Identification System (IPGCS). The versatile IPGCS (5) incorporates instrumentation... 

A novel interfaced pyrolysis gas chromatographic peak identification system has been used to study the pyrolysis and oxidative pyrolysis of... 

Figure 12.14 Chromatographic analysis of aniline (a) Precolumn chromatogram (the compound represented by the shaded peak is solvent flushed) (b) main column chromatogram without cryotrapping (c) main column chromatogram with ciyottapping. Conditions DCS, two columns and two ovens, with and without ciyottapping facilities columns OV-17 (25 m X 0.32 mm i.d., 1.0 p.m d.f.) and HP-1 (50 m X 0.32 mm, 1.05 p.m df). Peak identification is as follows 1, benzene 2, cyclohexane 3, cyclohexylamine 4, cyclohexanol 5, phenol 6, aniline 7, toluidine 8, nittobenzene 9, dicyclohexylamine. Reprinted with permission from Ref. (20).

In some cases a principal components analysis of a spectroscopic- chromatographic data-set detects only one significant PC. This indicates that only one chemical species is present and that the chromatographic peak is pure. However, by the presence of noise and artifacts, such as a drifting baseline or a nonlinear response, conclusions on peak purity may be wrong. Because the peak purity assessment is the first step in the detection and identification of an impurity by factor analysis, we give some attention to this subject in this chapter. 

The full-scan mode is needed to achieve completely the full potential of fast GC/MS. Software programs, such as the automated mass deconvolution and identification system (AMDIS), have been developed to utilize the orthogonal nature of GC and MS separations to provide automatically chromatographic peaks with background-subtracted mass spectra despite an incomplete separation of a complex mixture. Such programs in combination with fast MS data acquisition rates have led to very fast GC/MS analyses. 

It has been argued that in a typical 2DLC proteomic experiment, with only a limited number of fractions submitted for analysis in the second LC dimension, chromatographic peak capacity is less than 1000. This value is considerably lower than the expected sample complexity. Additional resolution is offered by MS, which represents another separation dimension. With the peak capacity defined as the number of MS/MS scans (peptide identifications) accomplished within the LC analysis time, the MS-derived peak capacity was estimated to be in an order of tens of thousands. While the MS peak capacity is virtually independent of LC separation performance, the complexity of the sample entering the MS instrument still defines the quality of MS/MS data acquisition. The primary goal of 2DLC separation is to reduce the complexity of the sample (and concentrate it, if possible) to a level acceptable for MS/MS analysis. What is the acceptable level of complexity to maintain the reliability and the repeatability of DDA experiments remains to be seen. 

Fig. 2.15. Chromatographic profile of a tomato juice extract at a column temperature of 7°C. Peak identification 4 =/0-apo-8 -carotenal 9 = (E)-/0-carotene 11 = 13(Z)-/0-carotene 10 = 9(Z)-/0-carotene 7 = lycopene 7a = 9(Z)-lycopene 7b = 15(Z)-lycopene. Reprinted with permission from V. Bohm [39],...

Fig. 2.17. Saponified carotenoids in orange juice. Chromatographic conditions are given in text. Chromatograms from absorbance monitoring at 430, 486 and 350 nm, respectively, are shown, all at identical attenuation. Peak identification 1, 3, 5, 8, 26 and 29 = unidentified peaks 4 = valen-ciaxanthin 6 = neochrome 7 = trollichrome 9 = antherxanthin 11 = c/s-anthexanthin 12 = neoxanthin 19 = auoxanthin B 20 = c/s-violaxanthin 22 = leutoxanthin 23 = mutatoxan-thin A 24 = mutatoxanthin B 25 = lutein 27 = zeaxanthin 28 = isolutein 31 = a-cryptoxanthin 33 = /J-cryptoxanthin 34 = phytofluene 35 = a-carotene 36 = ae-carotene 37 = / -carotene. Reprinted with permission from R. Rouseff et al. [41].

Fig. 2.51. LC of a flavone standard mixture. For chromatographic conditions see text. Peak identification 1 = quercitrin 2 = myricetin 3 = quercetin 4 = kaempferol 5 = acacetin. Reprinted with permission from C. W. Huck et al. [153].

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...

Fig. 2.60. Simultaneous HPLC-APCI-MS (a) and HPLC-UV (b) chromatograms of the soybean pod extract. Chromatographic conditions see in text. Peak identification 1 = 7,4 -dihydroxyflavone-7-0-/l-D-glucoside 2 = luteolin-7-0-/i-D-glucosidc 3 = apigcmn-7-0-/5-l)-glucoside 4 = 7,4 -dihydroxyflavone 5 = apigcnin-7-0-/]-D-ghicosidc-6"-0-malonate 6 = luteolin 7 = apigenin. Reprinted with permission from S. M. Boue el al. [166].

Fig. 2.61. Separation of grape seed extract (a) and grape seed extract spiked with mixture of eight compounds (b) using optimized conditions. Chromatographic conditions are discussed in the text. Peak identification 1 = 2-phenylethanol 2 = vanillin 3 = ferulic acid 4 = protocatechoic acid 5 = caffeic acid 6 = gallic acid 7 = catechin 8 = epicatechin. Reprinted with permission from A. Kamangerpour et al. [167].

Fig. 2.84. Chromatograms of a solution prepared from commercial canned green tea (a), blank plasma (b) and sample plasma (c) of the same subject at lh after ingestion of 340ml commercial green tea. Peak identification 1 = quercetin 2 = luteohn (internal standard). For chromatographic conditions see text. Reprinted with permission from D. Jin et al. [204].

Fig. 2.135. Upper lane HPLC chromatogram of all-rran.v /l-carolcnc and its isomers in the presence of Chl-a and methyl stearate during illumination for 3h. Peak identification 1 = 13,15-cis-ji-carotene 2 = 15-cw-/fcarotene 3 = a 11 -1 ra ns - /1-c aro tc n c 4 = 9-c(.v-/l-carolene 5 = 13-cis-ji-carotene. Lower lane HPLC chromatogram of Chl-a and its isomers in the presence of /1-carotene and methyl linoletae during illumination for 3 h. Peak identification 1 = Chl-a isomer I 2 = Chl-a isomer II 3 = Chl-a 4 = Chl-a. Chromatographic conditions are described in text. Reprinted with permission from B. H. Chen et al. [306].

---