Agilent Technologies G6600-90006 manual Detector Sensitivity, Mdl

Detector Sensitivity

Detector sensitivity is an indicator reflecting the performance characteristics of a given system, and is a useful tool to determine when Detector maintenance is warranted. Sensitivity is typically reported as a minimum detection limit (MDL) as calculated from the following formula:

MDL

= 0.66 ⋅ ( Am'tN / S) ⋅ (PktoPkNoise)

(Wd1/2ht ) ⋅ (Signal)

Where Am't N/S (amount of nitrogen or sulfur) is the mass of nitrogen or sulfur in picograms that reaches the Detector, PktoPkNoise (peak-to-peak noise) is the measure of the noise (e.g. in mV), Signal is the height of the peak in the same units, and Wd1/2ht is the width of the peak at half height in seconds. The constant 0.66 is used in the calculation assuming the MDL S/N = 3.29.

Before it is released from the factory, each 355 SCD must pass an MDL level of <0.5 pg Sulfur/second and each 255 NCD must pass an MDL level of <3.0 pg Nitrogen/second. The response from individual detection systems may vary by a factor of 2 or 3; however, it is typical for Detectors to perform in the 0.1-0.3 pg S/second range for the 355 SCD and in the 1-2 pg N/second for the 255 NCD when tested at Agilent.

Operation and Maintenance Manual 89