HPLC-based analysis software

In many HPLC-based analysis software packages with SEC module, the correction with the slope of the calibration curve is not done. This leads to wrong MMDs and partially wrong results, for example, amount below/above a defined molar mass border. The error caused by the missing correction will increase with sample polydispersity and when the data recording frequency is reduced. The qualitatively introduced correction by the slope of the calibration curve can associated with the first derivative of the calibration curve. 

Fully automated analysis is also an option wherein the samples are placed in an autosampler and predefined HPLC-NMR experiments are performed. This is covered in detail elsewhere in this volume, but in summary, the software allows automatic detection of UV peaks in the chromatogram based on predetermined time-windows or peak intensities. The successful detection of each UV peak triggers the system to stop the flow at an appropriate time to isolate the peak in the NMR flow probe. Then data relating to the peak (intensity, retention time, etc.) are transferred to the NMR host computer and used to define the parameters for the automatically acquired NMR spectrum. This automatic NMR operation includes field homogeneity optimisation, setting and optimisation of all NMR acquisition parameters, and the predefinition of the resultant signal-to-noise ratio required in the spectrum. The measurement of 2-dimensional (2D) NMR spectra can also be performed. 

There are two separate but interrelated aspects to QSAR modeling of antibacterial peptides the choice of QSAR descriptors and the choice of numerical analysis techniques used to relate these values to antibacterial activity. A simple example of a QSAR descriptor is the total charge of a peptide. A large number of QSAR descriptors is available for small compounds in the literature and from commercial software products that may be considered. A smaller subset is used in QSAR studies of antibacterial peptides and may be separated into two categories descriptors based on empirical values and calculated descriptors. An example of an empirical value is HPLC retention time, which is a surrogate measure of solubility or hydrophilicity/hydrophobicity. An example of a calculated descriptor is total peptide charge at pH 7. 

Analysis of Phenolic Compounds. A Hewlett-Packard (Palo Alto, CA) Model 1090 HPLC System, was used to determine the levels of specific phenolic components. The HPLC system was equipped with a ternary solvent delivery system, a diode array UV-VIS detector, and HP ChemStation software for data collection and analysis. Full chromatographic traces were collected at 280, 520, 316, and 365 nm, and spectra were collected on peaks. The stationary phase was a Hewlett-Packard LiChrosphere C-18 coliram, 4mm X 250 mm, with 5 pM particle size packing. Operating conditions include an oven temperature of 40 C, injection volume of 25 pL, and flow rate of 0.5 mL/minute. The mefriod was based on a previously published method for phenolic components in wine (30) and used the modified solvent gradient shown in Table II. Solvent A was 50 mM dihydrogen ammonium phosphate, adjusted to pH 2.6 with orthophosphoric acid. Solvent... 

The combination of the two methods in the 2D setup dramatically increases the resolution of the separation system and gives a clear picture of the complex nature of the sample mixture. A three-dimensional (3D) representation of the gradient HPLC-SEC separation is given in Figure 5 each trace represents a fraction transferred from HPLC into the SEC system and gives the result of the SEC analysis. The 3D view already indicates the complexity of the sample mixture. The point of view can be chosen deliberately in the software. Based on the 2D analysis, a contour map with 16 spots would be expected. Each spot would represent a component within the complex sample that is defined by a single composition and molar mass. The contour map should also reflect the (4 X 4)... 

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