Commands and Tips for Third-Party Devices
Agilent 1100/1200 HPLC System: Recording Absorbance Spectra (VWD Detector)

For the Agilent 1100 and 1200 VWD detectors, you can record absorbance spectra of substances used in an analysis, and thus identify optimum wavelengths for method development. Spectrum scans can only be performed within a sample program.

Before you can record an absorbance spectrum (Scan command), an intensity spectrum of the baseline (blank spectrum) must have been recorded (ScanBaseline command). The baseline spectrum is saved in the detector's memory. After power on of the detector, a new baseline spectrum must be recorded.

Set the pump flow to 0.000 ml/min at a time when you expect the peak for which you want to scan the spectrum (in the example below: 1.200 min) and then start the scan. In the chromatogram, the signal is freezed during the scan process and continues after the scan was completed. Use the parameters ScanStartWvl and ScanEndWvl to define the wavelength range to be scanned (190-600 nm). The ScanStepSize defines the step size for the scan (1 ... 10 nm).

The program below is for a 1100 Series VWD detector and can be used as an example for recording a baseline and absorbance spectrum:

Tip:

To adopt the program for use with an 1200 Series VWD SL detector, the PeakWidth command "UV_VIS_1.PeakWidth" has to be changed to "UV.PeakWidth".

When the scan is finished, a message appears in the Audit Trail of the sample. To retain the data, Chromeleon saves both spectra automatically to a Spectra Library named HP1100VWD.lib. The spectra library is saved to the sequence directory of the current sample. The location where the spectra are saved is also indicated in the Sample Audit Trail.