Linear temperature programming

Van Den Dool, H. and P.D. Kratz (1963), Generalization of the retention index system including linear temperature programmed gas-liquid partition chromatography . J. Chromatogr, Vol. 11, p. 463. 

The purity of 1 and 2 is assessed by analytical gas-liquid chromatography (GC) on a Hewlett-Packard 5890 gas chromatograph equipped with a flame-ionization detector and fitted with a 50 m x 0.2 mm HP-5 fused silica glass capillary column using linear temperature programming from an initial temperature of 150°C for 5 min to a final temperature of 200°C for 10 min at a rate of 5°C/min. 

FIGURE 15.6 (a) A linear temperature program, (b) Applying the temperature program in (a) to a sample that... 

More recently, programmes are also available that features both in linear and non-linear temperature programming as sample and reference columns The compartment temperature can also be raised at various rates upto a maximum of 60 °C min 1 in the lower-temperature ranges and about 35 °C min 1 at higher temperatures. 

Habgood and Harris (5) derived the following equation showing the relationship between isothermal retention volumes and retention volumes obtained under linear temperature-programming ... 

Although the combined asymptotic density/linear temperature program is usually the best approach, such a gradient is difficult to achieve without computer control of the pump and oven. Even an asymptotic (or linear) density gradient alone is beyond the capability of some SFC pumps. When faced with such limitations, it is reasonable to use a linear pressure program instead. The curvature of the density pressure-isotherms for some supercritical fluids (e.g., pure CO2) is such that a linear increase in... 

Discs of paper, %-in diameter, were punched from sheets. The discs were placed in 4-in diameter aluminum foil pans and covered with 80-mesh stainless steel screen to prevent coiling. The samples were then linearly temperature programmed at various rates in a DuPont 990 differential thermal analyzer under a 50-cc/min flow of air or oxygen. The paper reaction peaks were recorded, and the peak maximum temperatures were measured and corrected for thermal resistance, thermo-... 

Figure 3. Chromatogram of the aroma of Spartan 30mx0.5mm RSL-150 FS capillary column, linear temperature programming 20 C 220 C, FID-detection. 1 = ethyl acetate, 2 butanol, 3 = ethyl propionate, 4 = propyl acetate, 5 = 2-methylbutanol, 6 = 2-methylpropyl acetate,...

The proposed form of data presentation became highly popular and opportune in gas chromatography. Up to the present, some thousand references to the Kovat s work [1] have been known. The RI values are proportional to the free energies of sorption this is their thermodynamic interpretation. Further development of the RI concept was aimed at its application to nonisothermal conditions of gas chromatographic (GC) analysis. For linear temperature programming regimes (which are characterized by two variables initial temperature, Tq, and rate of its increase, r, deg X min ), the linear relationship (3) does not hold. In some partial cases, other linear dependence seems more precise for the retention time approximation ... 

This is a reason to change the formula for the RI calculation (the set of reference compounds and their attributed RI values remain the same). This version of RIs developed especially for a linear temperature programming regime (linear retention indices) have been proposed by Van den Dool and Kratz in 1963 [2] ... 

This procedure is a general method for calculating the effect of the program rate on retention time. Basically, the corrected retention volume must be measured for each solute of interest at two different temperatures to provide the thermodynamic constants. The above equations will then allow the effect of different linear temperature programs on the corrected retention volume to be calculated for each solute. The effect of program rate on resolution can also be observed if some solutes elute close together. In fact, the... 

Figure 41. Effect of linear temperature programs on tx (a) and E (b) estimates and variations. Theoretical value of tm, 100 weeks theoretical value of / ]. 25.00 kcal/mol assay error (standard deviation) 2%. (Reproduced from Ref. 334 with permission.)...

Figure 20.6 shows a temperature programmed separation of a complex hydrocarbon mixture with stepwise linear temperature programming. The first 12 gaseous or light compounds are readily eluted d resolved at a low fixed (100°C) temperature for 5.5 min, while the others require higher temperatures. After 5.5 min, the temperature is linearly increased at 5°C/min for 20 min to 200°C, and then the temperamre is held at that value until the last two compoimds are eluted. 

Tf = final program temperature. To = initial program temperature, t = time, tp = program time for a linear temperature program, tM = column hold-up time, k = initial value of the retention factor at the start of the temperature program, wp = peak width at base and N = column plate count. 

Rosea I.D., R. Granger, and J.M. Vergnaud. 2004. Linear temperature programming rheometers for the cure of rubbers Effect of various parameters. Polym. Polym. Composites. 12 87-98. 

The moving die rheometer, MDR, still widely used, is only run under isothermal conditions. Thns, three experiments are necessary to determine the three parameters that are able to describe the effect of temperature on the rate of cure. A better use of the MDR technique is surely obtained by programming the temperature, in the same way as calorimetry was run. Hence, the rubber process analyzer (RPA), which can be run either nnder isothermal conditions or with a programmed temperature, has been recently launched on the market. Nevertheless, as shown in Chapter 3, by using various ways of heating, the usual linear temperature programming is perhaps not the best. 

In 1963 van den Dool and Kratz [9] proposed the use of a linear interpolation (using tn instead of log t n) in Equation (3)) for linear temperature-programmed operation, since in this case there is an approximately linear relationship for homologous series between retention times and number of carbon atoms z ... 

---