Why is the sensitivity usually used to evaluate the performance of TCD detectors, rather than the detection limit?
Thread Content
In gas chromatography, why is the sensitivity of the TCD detector typically used to evaluate its performance rather than its detection limit? Unit: How to read mv.ml/mg? Thank you! :)
It seems this question is a bit difficult. The typical sensitivity S is greater than or equal to 2000; values of over 10,000 or 20,000 also exist. I just don’t know what kind of concept it is. . . . How big is it?:) :)
The magnitude of the signal generated when a certain amount of a component can be detected by the detector is referred to as the detector’s sensitivity to that component; it is also known as the response value or response level, and it is an important indicator for assessing the quality of the detector. For concentration-type detectors (such as thermal conductivity and electron capture), the unit is mV·mL/mg for liquid samples and mV·mL/mL for gas samples. For mass-type detectors (such as flame ionization), the unit is mV·s/g; the higher the sensitivity, the better.
Here’s my personal opinion: In the past, we used sensitivity to evaluate instruments, but these days, the limit of detection is what is generally used in practice. The former is a bit like something on paper, while the latter is something tangible. Some instruments have a very high sensitivity indicated on them; when actual samples are tested and compared to this sensitivity, samples of similar concentration cannot be detected. So, I like to use the detection limit to judge the quality of an instrument. But measuring the signal value is also an important criterion for judgment. In such cases, it’s best to ask the chromatography installation technicians, as they have the deepest insights on this matter. A few more words. Sensitivity is like the best record of your performance, while the detection limit at each point in time represents every moment of your life. You can’t use your best record to last a lifetime!