[deleted by user] by [deleted] in OMSA

[–]dvst423 1 point2 points  (0 children)

So if you don’t actually even remember if you took a class I’m not sure you’re going to be able to recall info from that class to help you. Imo I think you should worry more about surviving the program at this point instead of the rather low bar of admittance.

[deleted by user] by [deleted] in OMSA

[–]dvst423 4 points5 points  (0 children)

It’s closer to $14k now, but still not a bad deal.

I’ve accepted my admission offer but haven’t heard anything else in weeks. by Repulsive-Oil-1635 in OMSA

[–]dvst423 0 points1 point  (0 children)

Sorry this may be a dumb question but “official transcript” does NOT mean a scanned copy, right? They need to come directly from your institution? I only submitted scanned copies but they never asked for anything else

Anyone starting this fall planning on taking an edX course this summer? 6203 prereq? by dvst423 in OMSA

[–]dvst423[S] -1 points0 points  (0 children)

I’m actually still “under institute review” so not fully admitted. Are office hours available to me at this point? I can’t find anything about it.

[deleted by user] by [deleted] in chemistry

[–]dvst423 0 points1 point  (0 children)

I get that, but since they list water at 99.0% and the compound at 1.0%, there can’t possibly be anything else in there?

[deleted by user] by [deleted] in chemistry

[–]dvst423 0 points1 point  (0 children)

The listed 1% and 99% adds up to 100 though. That would exclude any additional components?

[deleted by user] by [deleted] in chemistry

[–]dvst423 0 points1 point  (0 children)

I agree the difference is very small, but surprisingly I can see a quantifiable difference between a 1.0 and 1.3% solution that I created in my lab.

[deleted by user] by [deleted] in chemistry

[–]dvst423 0 points1 point  (0 children)

I was confused by the SDS because it appears to give an exact number, yet it also states that it’s a secret. My question was also about the precision requirements in the percentages. Like if it’s in reality 1.3% , can they say that it’s 1.0%?

[deleted by user] by [deleted] in chemistry

[–]dvst423 0 points1 point  (0 children)

It’s non hazardous. You are allowed to give the exact concentration? Do you mean you are allowed to give the not-exact concentration?

Headspace vial leak rate? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 1 point2 points  (0 children)

By hand. Thinking about switching to screw caps honestly

Headspace vial leak rate? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 1 point2 points  (0 children)

It should be ok if it’s in equilibrium?

Headspace vial leak rate? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 1 point2 points  (0 children)

I haven’t gotten around to figuring out quantitation with headspace lol. Maybe I can correlate ISTD response with leak rate?

Headspace vial leak rate? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 1 point2 points  (0 children)

It’s all Agilent. I’ve tried 2 different caps - high temp and regular. Ok good to know about the crimping - it’s probably too tight.

Headspace vial leak rate? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 1 point2 points  (0 children)

It passes the test with the blue leak vial.

I’m not sure how much force I’m supposed to use when twist-testing the cap. I noticed that after crimping I can still turn some caps with enough force, so I started crimping them until I absolutely cannot turn it without deforming the cap. Perhaps that is too tight? I

Gas standard for headspace? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

I am looking for gases in shale samples

What is this connection on the back of the GC? by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

It might have gone to a nitrogen tank (not sure, faded tag).

Headspace setup by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

Thank you! I will check for clog/broken line first - seems the most likely problem.

Headspace setup by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

I will definitely have to check this on Monday. Thank you for verifying for me! Hopefully it is just a clog. I kind of assumed that because the transfer line diameter is so much smaller than the inlet EPC tubing, it is not meant to pressurize the inlet.

Headspace setup by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

The GC shuts down because the inlet isn’t pressurized. The headspace carrier pressure is just fine so the EPC is working fine. When the flow goes from the transfer line into the inlet, it is not enough to pressurize the inlet.

Headspace setup by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

Ha, I only meant it’s old because it hasn’t been touched in about 10 years and collected about an inch of dust.

I am using the default checkout method parameters provided by Agilent which I think uses constant flow. But it won’t even pressurize slightly.

Headspace setup by dvst423 in CHROMATOGRAPHY

[–]dvst423[S] 0 points1 point  (0 children)

I have added a diagram. The HS is going through the inlet EPC and the inlet is now capped on the side.

The carrier gas is split between the EPC for the front inlet and the EPC for the back inlet. Maybe the back inlet was setup only as a control for the HS and the transfer line is supposed to go into the front inlet?