Calibrating a Trace Hydrogen Sulfide Detector from a 190 PPM Standard
Can you make three tandem dilutions day after day and still come up with the same final concentrations? With the Custom Sensor Solutions Model 1010, the answer is yes. While developing a method for detecting sub-PPM traces of H2S for a client, we needed to dilute a standard of 190 PPM so that we could get reliable concentrations of 0.1 PPM, or 100 PPB. And we had to do it time after time.
The solution was a three stage dilution using the Model 1010 Precision Gas Diluter. The first two stages used sample bags, and the third fed directly into the analysis system.
We started by diluting the 190 PPM standard to 19 PPM, using a 10% setting of the Model 1010-P. We then diluted the 19 PPM sample to 1 PPM, using a setting of 5.6%. This sample was connected to the input of the Model 1010-P and used to generate the graph below. For example, 100 PPB H2S was generated by setting the dilution dial to 10%. Calibration curves made on consecutive days, using this procedure, were nearly identical. The figure compares the dilutions made on consecutive days using this procedure. Even the accumulated errors of three tandem dilutions do not add up to a significant difference.