Capillary chromatogram

Taken collectively, the data clearly indicated differential vaporization as the primary mode of toxaphene loss from leaf surfaces and gave no indication that chemical reactivity played even a minor role. If toxaphene had been degraded either on surfaces or during its brief residence time in the air prior to sampling, changes in the chromatographic profile would have been erratic with new peaks observed in the capillary chromatograms such as occur in samples of anaerobic soil and ditch sediment where microbial decomposition is extensive. 

Figure 5. Capillary chromatograms of aa aliphatic fraction from a solvent refined coal liquid. Conditions (A) SFC...

Fig. 3.12. Capillary chromatograms of volatiles from 24 h urine of a normal male detected by (A) flame ionization detector, and (B) the nitrogen sensitive thermionic detector. Reproduced from [113].

A typical capillary chromatogram of a hydrocarbon sample run on GC-MS has the same appearance as it would with an FID (see Fig. 10.9). Note the narrow peak widths, typically around 1 second or less at half height. This means that the MS system must scan the GC peak about 10 times per second in order to get a good mass spectrum. 

Of course, the capillary chromatogram in Figure 4.1b, obtained at 20 mL/min carrier-gas flowrate—a linear velocity of 172 cm/s—exhibits far less resolution than is possible when the flow or velocity is set closer to the optimum, as shown in... 

Three stages in the evolution of the capillary column technology are presented in Figure 3.3 a packed coluum separation and two separations with a stainless steel and glass capillary coluum. Better resolution is evident with the capillary chromatograms because more peaks are separated and smaller peaks can be detected. The superior performance of the glass capillary coluum is clearly apparent in this case. 

In capillary electrophoresis the conducting buffer is retained within a capillary tube whose inner diameter is typically 25-75 pm. Samples are injected into one end of the capillary tube. As the sample migrates through the capillary, its components separate and elute from the column at different times. The resulting electrophero-gram looks similar to the chromatograms obtained in GG or HPLG and provides... 

Although aimed at the introductory class, this simple experiment provides a nice demonstration of the use of GG for a qualitative analysis. Students obtain chromatograms for several possible accelerants using headspace sampling and then analyze the headspace over a sealed sample of charred wood to determine the accelerant used in burning the wood. Separations are carried out using a wide-bore capillary column with a stationary phase of methyl 50% phenyl silicone and a flame ionization detector. 

The most common chromatogram in the distilled spirits industry is the fusel oil content. This consists of / -propyl alcohol, isobutyl alcohol, and isoamyl alcohol. Other common peaks are ethyl acetate, acetaldehyde, and methanol. The gc columns may be steel, copper, or glass packed column or capillary columns. Additional analyses include deterrninations of esters, total acids, fixed acids, volatile acids, soHds or extracts (used to determine... 

Figure 10.3 Gas cliromatograms of a cold-pressed lemon oil obtained (a) with an SE-52 column in the stand-by position and (b) with the same column showing the five heart-cuts (c) shows the GC-GC chiral chromatogram of the ti ansfeired components. The asterisks in (b) indicate electric spikes coming from the valve switcliing. The conditions were as follows SE-52 pre-column, 30 m, 0.32 mm i.d., 0.40 - 0.45 p.m film tliickness cairier gas He, 90 KPa (stand-by position) and 170 KPa (cut position) oven temperature, 45 °C (6 min)-240 °C at 2 °C/min diethyl-tert-butyl-/3-cyclodextrin column, 25 m X 0.25 mm i.d., 0.25 p.m film thickness cairier gas He, 110 KPa (stand-by position) and 5 KPa (cut position) oven temperature, 45 °C (6 min), rising to 90 °C (10 min) at 2 °C/min, and then to 230 °C at 2 °C/min. Reprinted from Journal of High Resolution Chromatography, 22, L. Mondello et al, Multidimensional capillary GC-GC for the analysis of real complex samples. Part IV. Enantiomeric distribution of monoterpene hydrocarbons and monoterpene alcohols of lemon oils , pp. 350-356, 1999, with permission from Wiley-VCH.

Figure 12.13 Illustration of isothermal dual capillary column clnomatography used for separation of UV photolysis products of methyl isopropyl ether, (a) Heait-cut and hack-flushing at preseparation clnomatogram 1, PPG pre-column (20 m X 0.25 mm i.d.) 55 °C, 0.2 har N2 3p.L. Clnomatogram 2, Marlophen main column (100 m X 0.25 mm i.d.) 1.5 har N2 sample, heait-cut from chromatogram 1. (h) Obtained under the same conditions as (a), hut without capping of the heait-cut. Reprinted with permission from Ref. (19).

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).

Figure 14.8 shows a detailed schematic representation of a natural gas analysis System, which fully complies with GPA standardization (8). This set-up utilizes four packed columns in connection with a TCD and one capillary column in connection with an FID. The contents of both sample loops, which are connected in series, are used to perform two separate analyses, one on the capillary column and one on the packed columns. The resulting chromatograms are depicted in Figure 14.9. 

Figure 14.9 (a) Typical chromatogram obtained from the natural gas analyser, capillary... 

Qualitatively equation (7.15) is adequate to describe tiM f influence of layer quality, selectivity, and zone position in the 1 chromatogram upon resolution for a single unidimensional development under capillary flow controlled conditions. The variation of R, with Rf is not a simple function as can be seen from Figure 7.6. The resolution increases with the layer efficiency in a manner that depends linearly on the R, value. — Relatively small changes in selectivity have an enormous impact on... 

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