[Lucek]

Hi everyone,

I am struggling to create precise naphthalene standards for HPLC analysis with the UV detector.

I was trying to make few standards: 1, 2, 5, 10, 15, 25, 50 and 100 ppb. I tried to dissolve them in methanol or in acetonic and then dilute with those organic solvents to obtain that low concentrations but it seems to be not possible to accomplish. What is happening:

1) if I prepare organic solvent base standards by weight - the organic solvent evaporate while measured. No way to stop it, I tired to cool it down.
2) by volume no way, to grab a proper volume of the liquid with pipette. The organic solvent doesn't stick to the pipette tip.
3) with water, for some reason concentration of naphthalene drops down with time (is it caused by methanol evaporation and insolubility of naphthalene in water?)

Does anyone know how can I create good, quality standards of naphthalene for HPLC?

cheers,
Lucek

[hypervalent_iodine]

I am confused by your troubles using a by volume approach. Are you using plastic pipette tips for this? If so, that might be your problem and I would recommend switching to a glass Hamilton syringe. Evaporation will also be a problem with what you are working with, so I would only use standards within a few days (or less) of their preparation.

[Lucek]

yes, plastic pipette tips to at least transfer the solution to the scale.

Ok I will try with the glass Hamilton Syringe option.

thanks

[hypervalent_iodine]

yes, plastic pipette tips to at least transfer the solution to the scale.

Ok I will try with the glass Hamilton Syringe option.

thanks

For future reference, I would avoid plastic pipette tips for organic samples, particularly if you are looking at low MW standards. Plasticisers can really mess with your analysis, and some solvents will straight up dissolve the tips.