Principle of Operation - UV-VIS Detection
UV absorbance detection is the most popular form of detection. More than 50 % of all CE systems are equipped with UV absorbance detectors. Among the advantages of UV-VIS detectors are simplicity of use and the fact that almost any compound can be detected by UV absorbance, either direct or indirect. Typical limits of detection are 1 to 10 µM for compounds that show considerable absorbance at least one wavelength. Out of many UV-VIS detectors that are used in combination with PrinCE, Prince Technologies offers one of the most sensitive detectors, the Lambda 1010 UV-VIS Detector.
Some Features of the Lambda 1010 UV-VIS Detector
- Monochromator based wavelength selection in steps of 1 nm
- Simple operation conditions and compact design
- High Sensitive Special designed CE-cell
- Wavelength Switching
- Detection at the absorbance maximum
- On column measurement
Monochromator based wavelength selection
Many UV/VIS detectors are equipped with filters for wavelength selection. This limits the selection of wavelengths, which may cause measuring next to the maximum of absorption. The Lambda 1010 detector uses a monochromator for wavelength selection, making it possible to choose from each wavelength in the range of 190 - 800 nm.
Simple operation conditions and compact design
The Lambda 1010 is a programmable UV/VIS detector for CE. The advanced technology and the user-friendly design of the instrument generate superb results in routine and more sophisticated chromatographic applications.
High Sensitive special designed CE Cell by Prince Technologies
In general capillaries used have an outer coating of polyimide for flexibility. This coating is not UV transparent. For good measurements, a small window for detection is made on the capillary, most often by burning the coating and cleaning with alcohol.
For reproducible measurements it is necessary that the light beam is always focused on the centre of the capillary. Therefore the CE cell has been designed with a slit, capturing the capillary at the window. With this capturing, a ball lens is positioned to have the optimum light intensity inside the capillary, giving the best signal results. Because of this design, a reproducible installation from capillary to capillary is easily achieved. Actually, by checking the light intensity going through the capillary itself, it is possible to position the window of the capillary at the light beam and optimise for small deviations in the window performance.
For analyses of compounds which differ in their l max. and/or in concentration and therefore in the absorbance at the peak maximum, it is useful to switch the detection wavelength and the range during the run according to the migration time of the compound. For complex mixtures the Lambda 1010 offers switching of wavelength.
Detection at the absorbance maximum
To detect unknown compounds at their maximum absorbance, it is recommended to use the l max. wavelength. The Lambda 1010 offers the possibility to measure the UV-spectra of peaks during the run without stop-flow. Measuring first the absorbance of the background electrolyte and then the spectra of the separated compounds you will obtain the peak spectra by a subtraction process.
On column measurement
Using capillary columns, there is the need to detect directly on-column to avoid peak broadening and any other extra column effect. This is possible with the capillary CE cell of the Lambda 1010 where the fused silica separation capillary is mounted in the light beam. The capillary CE cell for the Lambda 1010 is retrofitable. An additional calibration of the detector to adapt the CE cell is not needed. The self aligning optics of the capillary flow cell guarantee the adjustment of different capillary diameters to the optics of the detector.
Due to the small illuminated volume, the low noise of ±2x10-5 AU, and the high separation efficiency of CZE, the mass-sensitivity for Uracil is approx. 1 pg. The capillary acts like a cylindrical lens and gives extraordinarily good linearity for the detector with absorbance < 0.1 AUFS.