What is the accuracy of hydrogen sulfide detection tubes in detecting hydrogen sulfide?
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I have a gas sample, which is refinery dry gas; due to its high hydrogen sulfide content, I used a detection tube with a large range (5%-80%) for testing. I added 10 ml of this sample to 100 ml of diluent, and the result showed that the color turned dark brown at 30%. If this value is multiplied by the dilution factor of 10, it becomes 300% – which is impossible, right? ), so I tried it with chromatography (I usually don’t use chromatography to analyze such samples), and the result was 24%? The problem is that it’s not clear which result can be reported; the result from the test tube is definitely incorrect, and it’s unknown what its accuracy level is.
This post was last edited by qugd on 2016-1-26 22:36. The test tube must have expired and become ineffective. Additionally, when using a test tube for measurement, the gas flow rate during aeration also has an impact. Since it is already a constant hydrogen sulfide concentration, it should be detected using redox titration.
The unit we use for testing tubes is PPm, not %.
I think diluting it by 10 times and then multiplying by 10 isn’t correct. I’m not sure what gas you used for dilution; there are several components in refinery dry gas. If everything is diluted by 10 times at the same time, then those other gas components will also be diluted, so shouldn’t the proportions remain unchanged? , for reference only
I would like to ask a senior expert: is it titration at a specific point? Since it’s a gas, do you have any appropriate methods or materials available? Thank you. (The test tube is new.)
According to the instructions for the test tube, dilute it by a factor of ten; there is no need to multiply by ten again. Check on the chromatogram whether the range of the calibration curve falls within the acceptable limits.