Discussion Category:  Sample Preparation

Low Recovery for Water Standards

Hello,

We purchased this instrument around 2 years ago, as of recently we have been getting consistantly low recoveries for our water standards. I am concerned that we are losing it in the transfer line, what are the possible causes? We are only recovering around 95% of the standard value.

 

Thanks

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Asked by

jbhill2
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Chemist Tamer SalahReply by
Chemist Tamer Salah

Hi there,

What kind of water standards do you use?

Is the transfer line heating ok?

Is your crimper ok?

Are your septa the same?

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avatar placemarkReply by
jbhill2

We use Fluka, Hydranal Stds. We have the 140-160C and 220-230C stds. The recoveries are low for both. Our caps are tight so the crimper is working fine. The septa gets replaced regularly on the vessel and we have the recommended vail caps for this instrument.  I was thinking maybe the moisture was being lost in the transferline. I'm not sure if this is a common issue over time. The only other issue I could see is that the Standards are somehow losing moisture.

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Chemist Tamer SalahReply by
Chemist Tamer Salah

Is the heating of transfer line ok?

 

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avatar placemarkReply by
rderickson

Feel the transfer line. It should be warm to the touch. What is you blank value. Are you running a blank. Fluka standards are usually very reliable. Is the reagent fresh. How accurate is the weighing. You may be experiencing a problem from the probe. Can you remove it and clean it. Replace if necessary. How are you transferring the sample. Are you using a nitrgogen line or the pump from the sample processor. Check the dessicant in the bottle on the side of the processor. You may need a service technican to give the system a PM to see if that works.

 

Roger

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Chemist Tamer SalahReply by
Chemist Tamer Salah

Quote rderickson

Feel the transfer line. It should be warm to the touch. What is you blank value. Are you running a blank. Fluka standards are usually very reliable. Is the reagent fresh. How accurate is the weighing. You may be experiencing a problem from the probe. Can you remove it and clean it. Replace if necessary. How are you transferring the sample. Are you using a nitrgogen line or the pump from the sample processor. Check the dessicant in the bottle on the side of the processor. You may need a service technican to give the system a PM to see if that works.

 

Roger

 

Totaly agree....

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avatar placemarkReply by
jbhill2

Yes, I checked the line yesterday and it is working fine. I took it up to 50C and felt it to make sure. Our blanks are right where they always are, around 58-70 micro grams. We change the reagent after the water counter gets to ~50,000. Our blanace is connect to the instrument and we transfer the weight so it is fairly solid, its a 5 place balance.  I'll clean the probe and switch out the dessicant, let you know if that improves our results.

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jbhill2

Thanks again for the help. Turns out that it was indeed the crimper. We did a study with between two different crimpers and found the one we had been using yeilded lower results. Visually and by hand you couldnt tell a difference between the two capped vials so we didn't think it would be a crimping issue.

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