Programmed secondary parameters

Method Primary parameter(s) (program) Secondary parameter(s) (selectivity)... 

The second aspect of optimization in programmed analysis involves adapting the selectivity by variation of secondary parameters. The various secondary parameters listed in table 3.10 may be used to vary the selectivity of a chromatographic system without affecting retention to a great extent (see the discussion in section 3.6.1). 

If the program is optimized so that all sample components are eluted under optimal conditions, then other (secondary) parameters may be used for the optimization of the selectivity. However, changes in the secondary parameters may imply that the parameters of the program need to be re-optimized. For example, if the selectivity in a temperature programmed GC analysis is insufficient, then another stationary phase may be used to enhance the separation. However, the optimum program parameters obtained with one stationary phase cannot be transferred to another column that contains another stationary phase. The re-optimization of the temperature program for the other column will require at least one additional experiment to be performed. 

The primary and secondary parameters that may be used for the optimization of the program and the selectivity in programmed analysis, respectively, are listed in table 6.3 for the various chromatographic techniques. 

In programmed solvent LC the nature of the modifier(s) in the mobile phase is the most common secondary parameter that may be used for the optimization of the selectivity. This is an attractive parameter, because different modifiers may be selected and programmed automatically on various commercial instruments. Therefore, the possibilities for selectivi-... 

Parameters for the optimization of programmed analyses in various chromatographic techniques. Primary parameters may be used to optimize the program parameters (initial and final conditions, slope and shape). Secondary parameters may be used to optimize the selectivity. 

The most useful secondary parameter for the optimization of the selectivity in programmed solvent LC is the nature of the modifter(s) in the mobile phase. The selectivity can be varied by selecting various solvents (pure solvents for binary or ternary gradients mixed solvents for pseudo-binary gradients). Analogous to the situation in isocratic LC, it is possible to use different modifiers (and hence to obtain different selectivity) while optimum retention conditions are maintained for all solutes. This possibility to optimize the selectivity in programmed solvent LC will be discussed below. 

Of course, the simultaneous optimization of different (primary) program parameters (initial and final composition, slope and shape of the gradient) and secondary parameters (nature and relative concentration of modifiers) may involve too many parameters, so that an excessive number of experiments will be required to locate the optimum. This problem may be solved by a separate optimization of the program (primary parameters) and the selectivity (secondary parameters) based on the concept of iso-eluotropic mixtures (see section 3.2.2). This will be demonstrated below (section 6.3.2.2). However, the transfer of... 

A second reason not to become involved in extensive calculations for the complete mathematical optimization of the (primary) program parameters is that a more powerful way to optimize the separation of all sample components in the mixture may be to optimize the selectivity of the gradient by varying the nature of the mobile phase components (secondary parameters). 

A number of scliools use MATLAB as their basic software package. The disadvantage of the MATLAB ODE solver is that it is not particularly user friendly when trying to determine the variation of secondary parameter values. MATLAB will be used for the same four types of programs as POLYMATH. 

Table3 Further hydration and volume data (Si, V) for anhydrous and hydrated proteins as obtained by simple calculation procedures, together with some secondary parameters (V/M, Ny,/S, Vw(2rw) /5 ). Calculation procedures hydration Si according to Kuntz (K) volumes V according to Traube (T) or Cohn and Edsall (CE) these calculations were performed without ligands, using the molar masses M from the SWISS-PROT database (Table 1). Volumes V obtained by the programs SIMS (Table 1) or HYDCRYST (HC) and/or HYD-MODEL (HM) (Table 2) are inclusive of the contributions of ligands for calculating the V/M ratios, the molar masses from the crystal structure (Mcryst, Table 2) were used if these were different from the SWISS-PROT data...

XRF nowadays provides accurate concentration data at major and low trace levels for nearly all the elements in a wide variety of materials. Hardware and software advances enable on-line application of the fundamental approach in either classical or influence coefficient algorithms for the correction of absorption and enhancement effects. Vendors software packages, such as QuantAS (ARL), SSQ (Siemens), X40, IQ+ and SuperQ (Philips), are precalibrated analytical programs, allowing semiquantitative to quantitative analysis for elements in any type of (unknown) material measured on a specific X-ray spectrometer without standards or specific calibrations. The basis is the fundamental parameter method for calculation of correction coefficients for matrix elements (inter-element influences) from fundamental physical values such as absorption and secondary fluorescence. UniQuant (ODS) calibrates instrumental sensitivity factors (k values) for 79 elements with a set of standards of the pure element. In this approach to inter-element effects, it is not necessary to determine a calibration curve for each element in a matrix. Calibration of k values with pure standards may still lead to systematic errors for unknown polymer samples. UniQuant provides semiquantitative XRF analysis [242]. 

In this chapter we will take a look at some aspects of programmed analysis, particularly those which bear relation to the chromatographic selectivity. The parameters involved in the optimization of programmed analysis will be divided into primary or program parameters and secondary or selectivity parameters. These parameters will be identified for different chromatographic techniques and procedures will be discussed for the optimization of both kinds of parameters. 

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