Temperature, column effect stability

Column stability, 161 Column temperature, 267 effect on retention, 192,200 effect on viscosity, 192 nonuniform temperature profile, 194 optimization of, 193 Column tubing, 145 cleaning of, 145 irmer surffice of, 145... 

The robustness of an analytical procedure is a measure of its capacity to remain unaffected by small but deliberate variations in the analytical procedure parameters. The robustness of the analytical procedure provides an indication of its reliability during normal use. The evaluation of robustness should be considered during development of the analytical procedure. If measurements are susceptible to variations in analytical conditions, the analytical conditions should be suitably controlled or a precautionary statement should be included in the procedure. For example, if the resolution of a critical pair of peaks was very sensitive to the percentage of organic composition in the mobile phase, that observation would have been observed during method development and should be stressed in the procedure. Common variations that are investigated for robustness include filter effect, stability of analytical solutions, extraction time during sample preparation, pH variations in the mobile-phase composition, variations in mobile-phase composition, columns, temperature effect, and flow rate. 

Temperature variation may also be a relevant factor in flowrate stability. Since the viscosity of the solvent is temperature dependent, wide swings in the ambient temperature can directly affect pump performance. The direct effects of temperature on pump performance usually are far smaller, however, than the effects on retention and selectivity therefore, control of column temperature is generally sufficient to obtain high reproducibility. 

Parameters that should be tested in HPLC method development are flow rate, column temperature, batch and supplier of the column, injection volume, mobile phase composition and buffer pH, and detection wavelength [2], For GC/GLC methods, one should investigate the effects of column temperature, mobile phase flow rate, and column lots or suppliers [38], For capillary electrophoresis, changes in temperature, buffer pH, ionic strength, buffer concentrations, detector wavelength, rinse times, and capillaries lots and supplier should be studied [35, 36], Typical variation such as extraction time, and stability of the analytical solution should be also evaluated [37],... 

Difficulties of work at high temperatures include stationary phase stability and analyte stability. However, it has been shown that the relatively short residence times in the column at high temperatures tend to minimize the effects of analyte instability... 

The high resolution power provides for a good profile analysis of the sample with a clear pattern and minor peak overlap compared to packed column GC. Furthermore, in view of the possible toxic, synergestic or antagonistic effects of the individual PAH, it is important to quantify each compound separately. The chromatograms also demonstrate the application of 0V-73 to PAH analysis, a stationary phase similar to SE-52, but with improved temperature stability. 

This stabilizing effect of another ring has also been shown in thermal reactions. Bishop, Cooper, and Murray16 injected methyl 3,6-anhydro-a-D-mannopyranoside ihto a gas chromatograph, operating at a column temperature of 225°, and found 75% conversion into the furanoside. 

Cole [18] found that in the identification of kerosine and aviation fuels, the usual packed columns provided sufficient detail only up to Ci3 //-alkane, a range readily altered by evaporation effects. A suitable capillary column was developed which revealed extra detail of minor components above Ci3 u-alkane, and consisted of a 45mx0.25mm stainless steel column coated with OV-101. This gave satisfactory resolution and stability in the 50-310°C temperature range. 

Other factors (pH, temperature, foam dispersity, foam column height, rate of gas and liquid feed, etc.) also affect the accumulation effectiveness (parameter //). Some of these, such as pH, temperature, type and concentration of the collector, are changing the adsorption, others, like dispersity and foam column height, are changing the drainage rate that determines foam stability and expansion ratio. The book of Rusanov et al. [23] summarises the results on the effect of these factors on foam accumulation of surfactants. 

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