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Re: EPA 515.4 Diazomethane
Posted: Sun Nov 06, 2016 7:11 pm
by Don Shelly
Hi Cody,
Sorry, but I've been offline for awhile. Have you had any success?
Don
Re: EPA 515.4 Diazomethane
Posted: Mon Dec 05, 2016 9:04 pm
by xie
Hi jdjaw,
I'm interested in your method of Diazomethane generation as I'm trying to get Method 515.4 going. Currently we use 515.1. Can you tell me specifically how much Diazald you put in the inner tube? Is that a solution or just the powder? The only other chemicals needed are MeOH, NaOH, MTBE? How many samples can you esterify with the amount produced? Do you have a part number for the apparatus? Much appreciated.
Looking forward to your response...
Re: EPA 515.4 Diazomethane
Posted: Tue Dec 27, 2016 4:27 pm
by Cody
Don (or anyone for that matter who has experience in making this method work), could you please email me at
cdickinson@stlwater.com. I'm still having issues and it's becoming increasingly frustrating. Please and thank you.
Re: EPA 515.4 Diazomethane
Posted: Tue Dec 27, 2016 10:40 pm
by jdjaw
Hi jdjaw,
I'm interested in your method of Diazomethane generation as I'm trying to get Method 515.4 going. Currently we use 515.1. Can you tell me specifically how much Diazald you put in the inner tube? Is that a solution or just the powder? The only other chemicals needed are MeOH, NaOH, MTBE? How many samples can you esterify with the amount produced? Do you have a part number for the apparatus? Much appreciated.
Looking forward to your response...
The diazald we do not measure out. We just make sure there is excess in the inside part of the apparatus. My understanding is that after the generation you want there to still be powder in the inside bulb. 2 mL of MeOH goes into the inside portion of the appartus with the diazald. 5 mL of MTBE goes into the outside tube. After everything is sealed 12-14 drops of 6N NaOH is added through the septa at the top slowly, about 1 drop every 5 seconds. We let the reaction go for 30 minutes. The part number is 281155 from wheaton.
Re: EPA 515.4 Diazomethane
Posted: Thu Jan 05, 2017 5:43 pm
by Cody
So, update on the problem I've been facing. I believe that I found where my problem was. However, I need some input on why this would have caused issues.
I looked through 515.3 and 515.4 side by side to see every single difference in the method. I noticed that 515.3 used sodium thiosulfate as the dechlorinating agent and 515.4 used sodium sulfite. I had been using sodium sulfite. I decided to switch to sodium thiosulfate and all of my samples stayed yellow for the entire 30 minutes of derivatization. I've repeated the process for a few days to see if this was in fact that problem. I even put in a few samples that had the sodium sulfite in it and sure enough, the ones with the sodium sulfite barely stayed yellow for 30 seconds and the others stayed yellow the entire 30 minutes.
So my question would be why the sodium sulfite is causing me this issue? Has anyone else faced this problem?
Re: EPA 515.4 Diazomethane
Posted: Tue Feb 28, 2017 3:41 pm
by xie
Hi jdjaw,
I'm interested in your method of Diazomethane generation as I'm trying to get Method 515.4 going. Currently we use 515.1. Can you tell me specifically how much Diazald you put in the inner tube? Is that a solution or just the powder? The only other chemicals needed are MeOH, NaOH, MTBE? How many samples can you esterify with the amount produced? Do you have a part number for the apparatus? Much appreciated.
Looking forward to your response...
The diazald we do not measure out. We just make sure there is excess in the inside part of the apparatus. My understanding is that after the generation you want there to still be powder in the inside bulb. 2 mL of MeOH goes into the inside portion of the appartus with the diazald. 5 mL of MTBE goes into the outside tube. After everything is sealed 12-14 drops of 6N NaOH is added through the septa at the top slowly, about 1 drop every 5 seconds. We let the reaction go for 30 minutes. The part number is 281155 from wheaton.
Re: EPA 515.4 Diazomethane
Posted: Tue Feb 28, 2017 4:07 pm
by xie
Jdjaw,
Your response has been very helpful. Thank you!!
I was wondering what size syringe you are using to deliver the NaOH solution and what size needle. 12-14 drops is about how much in milliters (or microliters)? Thanks.
Xie
Re: EPA 515.4 Diazomethane
Posted: Thu Mar 02, 2017 11:57 pm
by jdjaw
We are using a 1 mL syringe
Edit* The total amount we add is around 150 uL of NaOH according to our SOP but I have not really verified it myself since when we do it we just counted the drops
Re: EPA 515.4 Diazomethane
Posted: Thu Mar 09, 2017 2:26 pm
by xie
jdjaw,
Thank you for all the info. I'm curious where you found this method or if it was developed in your lab. The Wheaton manual references the use of MNNG in place of Diazald:
"Required Materials:
Diazomethane Generator
1 mmol (133 mg) 1-methyl-3-nitro-1-nitrosoguanidine (MNNG)
0.5 ml distilled water
3 ml ether
0.6 ml 5N sodium hydroxide solution
1 ml syringe
22 gauge needle
Ice bath"
I have no interest in using MNNG and will try the method you are using. However, if I have good results, I may need to provide some sort of reference.
Thanks,
Xie
Re: EPA 515.4 Diazomethane
Posted: Fri Mar 31, 2017 12:41 pm
by Bigbear
A related question.
For how long do you use the diazomethane for?
Up until our last NELAC audit we would use the diazomethane (stored at -80C ) until it lost color or ran out. It always esterified our extracts.
Our auditor made a big issue that EPA 531 says it must be stored at about -4 and only used for 72 hours.
How long do you all use it for?
Re: EPA 515.4 Diazomethane
Posted: Mon Apr 03, 2017 3:37 pm
by jdjaw
We made it every time for each batch and just neutralized it afterward. I think it mostly depends on the auditor you have it's just easier for us to avoid the issue all together by making it each time.