Chromatographic conditions temperature

The use of GC retention times with qualitative purposes for interlaboratory comparisons is very difficult because differences in chromatographic conditions (temperature, flow rate) and in column geometry (column length, internal diameter, film thickness) markedly affect their values. 

The effect of temperature on retention time was investigated by Scott and Reese (3), who measured the retention volume of the solutes o-dinitro-benzene, 2-ethoxy naphthalene and p-chlorophenatole over a range of temperatures. The chromatographic conditions used are as follows,... 

Zarzycki and coworkers [77] studied the influence of temperature on the separation of cholesterol and bile acids using reversed-phase stationary phases. The best chromatographic conditions for the separation of mnlticomponent samples of steroids were chosen. Experiments were performed on wettable plates with RP-18W and at the temperatnres of 5, 10, 20, 30, 40, 50, and 60°C. The studies showed (Figure 9.9) that the degree of separation in the high-temperature region can be increased by an improvement of the efficiency of the chromatographic system. However, a relatively weak retention-temperatnre response for the studied steroids was observed. 

Figure 1 Chromatogram of a neutral compound (toluene) with watenacetonitrile mobile phase. Chromatographic conditions — column 30 cm x 3.9 mm p-Bondapak C18 (10-pm particle size) mobile phase watenacetonitrile (50 50) flow rate 1.5 ml/min column temperature ambient detector wavelength 254 nm.

Figure 10 CC Internal Standard Method for step 1, scheme 1. Chromatographic conditions were column 12 m x 0.2 mm x 0.3 mm HP-1 injector temperature 300°C detector temperature 300°C column temperature 75°C for 3 min, then +10°C/min to 280°C.

Figure 14 Separation of 1,2/1,4 ketal with and without protection from oxidative degradation. Chromatographic conditions were column 25 cm x 4.6 mm Zorbax C8 (5-pm) column mobile phase 100 mM KH2P04 (pH 6.5) acetonitrile (50 50) flow rate 1.0 ml/min column temperature 35°C detector wavelength 220 nm. (A) Acetonitrile degassed. (B) Acetonitrile not degassed.

Figure 17 A typical chromatogram of LANA reaction (scheme 3). Chromatographic conditions— 45 55 100 mM KH2P04 acetonitrile at 2.0ml/min 25 cm x 0.46 mm Supelcosil LC-DB-18 (5-p) RPLC column column temperature ambient detector wavelength 254 nm.

The chromatoraphic profile of a tomato juice extract at a column temperature of 7°C, flow rate 2.0 ml/min and further chromatographic conditions (see caption) is shown in... 

RETENTION TIMES OF LYCOPENE AND FOUR /0-CAROTENE ISOMERS, USING DIFFERENT COLUMN TEMPERATURES BETWEEN 0°C AND 30°C, FLOWRATE 2.0 ML/MIN (FOR FURTHER CHROMATOGRAPHIC CONDITIONS SEE TEXT)... 

FIGURE 1.3 Enantiomer separation of the chiral acid iV-acetyl-a-allyl-glycine on CHIR-ALPAK QN-AX (a) and CHIRALPAK QD-AX (b) by an enantioselective anion-exchange retention process. Chromatographic conditions Column dimension, 150 x 4 mm ID eluent, 1 % (v/v) glacial acetic acid in methanol flow rate, 1 mLmin temperature, 25°C detection, UV 230 nm. (Reproduced from M. Lammerhofer, et ah, Nachrichten aus der Chemie, 50 1037 (2002). With permission.)... 

Chromatographic conditions were similar for all sample analyses. The temperature program was as follows initial temperature 120 C programmed at 2 C/min to a final temperature of 255 C injector 220 C and detector temperature 320 C. The carrier gas, hydrogen, was maintained at a column head pressure of 20 psi. The electron capture detector makeup gas was nitrogen with a flow rate into the detector of 17 mL/min. 

Supercritical fluid chromatography (SFC) is an intermediate chromatographic technique between GC and HPLC. It depends upon the fact that when a fluid becomes supercritical (both the temperature and pressure are at or above its critical point) it develops some of the solvating properties of a liquid whilst retaining the low viscosity of a gas. Hence, mass transfer (essential to efficient chromatography) is more akin to that of GC than HPLC, but many compounds can be chromatographed at temperatures much lower than what would be required by GC, so some thermally labile compounds are amenable to SFC where they would degrade under GC conditions [28]. 

Chromatographic Conditions. GC/MS-MS analyses were performed on a Varian 3800 gas chromatograph (Varian Chromatography Systems, Walnut Creek, CA) equipped with a 1079 split/splitless injector and a ion trap spectrometer (Varian Saturn 2000, Varian Chromatography Systems) with a waveboard for MS-MS analysis. The system was operated by Saturn GC/MS Workstation v5.4 software. The MS-MS detection method was adapted from reference. PCBs were separated on a 25 m length x 0.32 mm i.d., CPSil-8 column coated with a 0.25-pm film. The GC oven temperature program was as follows 90 °C hold 2 min, ramp 30 °C/min to 170 °C, hold for 10 min, rate 3 °C/ min to 250 °C, rate 20 °C/min to a final temperature of 280 °C, and hold for 5 min. Helium was employed as the carrier gas, with a constant column flow of 1.0 mL/min. 

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