Simple way to measure methanol purity?

Dear alls,

my question in in the project of extraction of caffein from fresh leaves. Recovery studies were also carried out to verify the precision and accuracy.

There are five calibration standards are 10ug/ml, 20ug/ml, 30ug/ml, 40ug/ml, 50ug/ml.

When 1ml of extract A was analysed directly by HPLC under suitable conditions, I got the result that leaves A had caffein amount 35,11ug/ml at the retention time 7,4.

How do I perform Spike Recovery in this case? Please help me.

Thank you for your consider,

For doing LCMS analysis of metabolites from crude samples of seeds, what is the procedure for fixing internal standards? Do we do multiple screenings until we get a detectable concentration peak of the standard and then use that for further analysis?

I am running a RP-HPLC system with a C18 column. In our group, we mainly use the system to analyze peptides.

The baseline of the system is not stable. In every run it is increasing over time.

The chromatogram shown is a 5 to 100 % ACN (+0.1 % TFA) gradient (in water (+0.1 % TFA)).

I exchanged the D2 lamp in the DAD recently. The chromatogram looks similar on another HPLC system. I think it's a problem with the column.

What can I do to get a better baseline? I tried cleaning the cloumn with different alcohols.

Do you have any other suggestions?

What is a solvent for folic acid?

I studied some literature that achieved this by dissolving salt into methanol. But I didn't get this concept or the chemistry behind this process. Also, this salt is not completely soluble in methanol.

I used diethyl 2-fluromalonate and diethyl 2-aminomalonate as a starting materials. Both of this were saponified with methanolic sodium hydroxide (2 M, 3.5 mL) in dichloromethane and methanol (9:1 v/v, 32 mL) and the sodium salt isolated by filtration through a Büchner funnel with a fine porosity glass frit. Once I did the all procedure, injected into mass but i couldn't detect the mass of corresponding acid.

I will be very grateful if any one suggest an efficient method for the synthesis of these two acid. Thanks much in advance.

I am interested in knowing the combined inhibition effect on gas hydrate formation in presence of various salts, methanol, other alchohols and MEG in water. Can someone suggest some research paper on this?

I want to make a solution of HCl and H2SO4, however mixing the two will create a lot of HCl gas and is quite dangerous. Is there a way to make this solution safely? Can I somehow mix HCl with a sulfate salt to get an acidic solution with all the ions present?

I have read that under mildly acidic or alkaline conditions alcohols can attack aldehydes/ketones to produce hemi-acetals. But the reaction is reversible, so the reactants and the hemi-acetal are in equilibrium. Let's say I have a solution of methanol to which I add mildly acidified glucose solution. In theory, a hemi-acetal should have formed. Now if I warm the solution for some time so that the methanol evaporates, the hemi-acetal should decompose back to maintain equilibrium. So I wouldn't be able to isolate such a compound. What experiment can I run then, to confirm the formation of the hemi-acetal?

What I have thought: Maybe I can use IR spectroscopy to confirm the presence of a new bond but considering the solvent is water, it seems infeasible to do this.