Manual Parameter Selection

The setup of experiment parameters can be separated in different categories. The entry of experiment parameters is not just restricted to the dialog box of the Go I Check Experiment Parameters pull-down menu command. The rf channel option bar is an integral part of the NMR-SIM main window whilst the Parameters I... pull-down menu command opens several different dialog boxes. The various different categories of experiment parameters are listed in Table 4.4. 

NMR Spectroscopy Data Acquisition, Second Edition. C. Schorn, B. Taylor Copyright 2004 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-31070-3 

Spin system variable start values and increments 

Rf channel and frequency offsets (Ol, 02, OFS) Dimension of data acquisition (Parmode), detection mode (AQ mod), spectrometer proton frequency (SF), time domain (TD, TDl), scans (NS), delay, sweep width (SW), incrementation for n dimensional acquisition (ndO and inO) 

Delays (d0...d31), pulses (0...p31), pulse power levels (pll...pl31) 

---

The operator should consult the specific instruction manual for selecting the proper run parameters for the determination of heat capacity. 

In practice, it is nontrivial to manually select the parameter values to obtain successful results. Moreover, it is not obvious how to measure the quality of the results. Therefore, a well defined performance measure and an efficient parameter optimization method are desired. 

Use the Curve Fit tool to obtain optimal results automatically. Document the differences to the manually obtained results. Clicking CURVE-FIT will allow the selection of the variable to be fit to the experimental data and the parameters to be determined. For each parameter, two initial guessed values and the maximum and minimum allowable values can be entered. Limit k, and k2 to positive values. On running under CURVE-FIT, the values of the required parameters are repeatedly updated until the final converged values are obtained. The updated values can be found in the Parameter Window. 

After the number of test compounds which are to be selected from the basic set has been decided upon one can apply one of the series design techniques reported in the literature. Some of these methods apply to a restricted number of parameters (e.g. two in the Craig graphical method 12,13)) and structural variations (e.g. a limited number of aromatic and aliphatic substitution patterns as in the Topliss manual... 

How to choose the best tissue preparation technique for every application is a difficult question to address. Sample throughput, analyte recovery, analyte thermal stability, amount of available sample, sample preparation techniques available, precision, accuracy, manual labor involved, and operator safety are only a few of the parameters that must be considered when selecting the optimum sample preparation technique. 

This algorithm permits us to determine the number of parameters "manually on the basis of the reaction graph without derivation of a steady-state kinetic equation. For large-sized and complex-structure graphs it is recommended that the corresponding sets of spanning trees are selected using computations [60]. 

The use of computers enables laboratories to greatly improve their production capabilities, but it also creates new tasks and responsibilities. For example, laboratories must verify computer programs used for data reduction in order to confirm the correctness of the calculations. To create an analytical method using commercially available or custom analytical software, laboratory chemists must exercise professional judgment in the selection of appropriate method parameters often accompanied by data entry by hand, which opens the door for errors to creep in. Today, electronic spreadsheets replaced manual calculations, and their correctness must be also verified. 

There are several other factors that are important when it comes to the selection of equipment in a measurement process. These parameters are items 7 to 13 in Table 1.2. They may be more relevant in sample preparation than in analysis. As mentioned before, very often the bottleneck is the sample preparation rather than the analysis. The former tends to be slower consequently, both measurement speed and sample throughput are determined by the discrete steps within the sample preparation. Modern analytical instruments tend to have a high degree of automation in terms of autoinjectors, autosamplers, and automated control/data acquisition. On the other hand, many sample preparation methods continue to be labor-intensive, requiring manual intervention. This prolongs analysis time and introduces random/systematic errors. 

General operating conditions are described in the user s manual, including lists of commands, together with the program and microprogram sequences that are available. These sequences are periodically upgraded by the manufacturers. Once the NMR experiment and its sequence are selected, the operator has to choose the appropriate experimental parameters. 

The instrament Linomat 5 is fully controllable by the winCATS-Planar Chromatography Manager software. With this system, one can select various parameters, such as number of tracks, band length, and application volume sequence, x positions on the plates, track distances, as well as application methods. The instrument applies the samples onto a thin layer automatically however, only changing the sample, i.e., filling and rinsing the syringe, is carried out manually. ... 

---