Chromatography Forum

Hi All,

I have acylated a biopolymer with Lauroyl Chloride to create Potassium Lauroyl biopolymer. I need to measure the amount of free Lauroyl Chloride in a sample for safety regulations.

I was thinking HPLC is probably going to be the best method to do this. Does anyone know a column and method that I could use that will allow me to detect just the lauroyl chloride?

Regards
Gavin

You first need to quench Lauroyl Chloride and convert it to amide or acid. If you try to do RP HPLC you will have very poor shape due to hydrolysis of acetyl chloride to acid. Quenching it with benzylamine will also address issue of low UV activity of Lauroyl Chloride. After you quench it you can use any RP column with C4 carbon chain or C8-C18 with lower loading.

What I was hoping to do is run some neat samples of Lauroyl Chloride at different concentrations. Presumably these will all give different sized peaks and generate a standard curve. And then run a sample of my product and see whereabouts it comes off at.
Can HPLC be used as a quantitative method like this?

We have a Luna C18 column which I will use.

Quenching it with benzylamine

How much benzylamine would I need to add to the lauroyl chloride?

I'm not too familiar with HPLC methods so what method would you recommend?
Eluent choice?
Flow rate?
Inj vol?
UV wavelength?

you will never have linearity if you don't quench your compound. At lower concentrations most of it will hydrolize and you might see a peak eluting faster (acid). If you use 3-5 equivalents of benzylamine it should be fine. You can quech all of the samples with the same amount of benzylamine. After you quench it you will see two peaks in UV - one for unreacted benzylamine and another one for layroyl amide. You will need to dissolve your sample in ACN and quench it with solution of benzylamine. This can be done in presence of water since reaction with amine is much faster than hydrolysis. By using higher organic concentration (50-70%) you will move bezylamine very close to the void. If you use for example Primesep B4 column (by SIELC) it will even come before void. Something like 60% ACN with 0.1% of organic acid (sulfuric or phosphoric) will let you separate both compounds (monitoring at 210-220 nm).

P.S. Let me see if I can find layroyl chloride and set up something in the lab (including quenching)