How to improve my detection limit?
The detection limit is the peak height that gives a significantly (at least 3 times) higher signal than the baseline noise. It is improved if the signal increases and/or the noise decreases. Signal and noise are not only determined by the detector but in fact by the settings and quality of the whole LC-EC system so no simple advice can be given. Improvement includes optimization of:
- Sample pre-treatment
- Flow rate and getting rid of pump pulsations
- LC parameters (mobile phase, column, injection volume, selectivity etc)
- Detector settings (range, potential etc.)
- Flow cell parameters (spacer, working electrode)
- Electronic noise suppression
Improving sensitivity in most cases goes hand in hand with improving detection selectivity. In many LC-EC analyses (blood, urine, CSF) interfering peaks (‘chemical noise’) in the chromatogram are the limiting factor. By a better sample pre-treatment this chemical noise can be suppressed. Flow rate fluctuations are a major noise source in LC-EC. Due to pump properties they have a regular pattern that can be calculated if the stroke volume is known. A pulse damper is a must in trace analysis.
For ALEXYS analyzers all this optimization has been done by Antec’s research lab. The result is ‘wrapped up’ in a system solution including guaranteed applications.