Chromatography Forum

Dear Experts

A. I am facing one problem . In one HPLC column ( YMC AM-302 C18 ) I get impurity before the main peak & in another HPLC column ( YMC A- C18 ) , impurity is detected after the main peak . During this time Mobile phase is unchanged .

I need information Y it is so .

B. Is there any HPLC columns set with software by which any HPLC method can be developed for any molecule or product .

Thanks in advance to all .

The two columns are not the same, the packing inside the columns is different. Column manufacturers have often a lot of different C18 columns. They have aften been designed to give different selectivities. Therefore, it is not a surprise that a different type of column gives you a different result. If you want consistent results, you need to use the saem column.

Uwe answered the first question.

The answer to the second question is a bit more complex. Selectivity (the relative spacing of the peaks) in reversed-phase LC is really affected by six things:
- mobile phase strength (the percent organic or the steepness of the gradient)
- temperature
- mobile phase type (the identity of the organic solvent used; usually either acetonitrile, methanol, or tetrahydrofuran
- column chemistry (as described briefly by Uwe)
- pH (for ionizable analytes)
- additive type and/or concentration (e.g., use of ion-pairing reagents or complexing agents).

Given that there are five other variables to play with, my contention is that most separations can be accomplished on most columns. The catch is that other conditions will be different.

For more detailed information, there were a couple of articles a year or so ago dealing with mobile phase adjustment to compensate for column differences:
http://www.lcgcmag.com/lcgc/data/articl ... rticle.pdf
http://www.lcgcmag.com/lcgc/article/art ... 3&pageID=1

Dear Sir,
Please be noted that that YMC ODS-A and ODS-AM columns are different, even though both are Reverese phase C18 columns.
ODS-A is very hydrophobic, 17 % Carbon loading ,totally endcapped.
ODS-AM is less hydrophobic comaped with ODS-A, 17 % carbon loading and SUPER ENDCAPPED,i.e. an additional proprietory endcapping step.
Due to additional treatment of endcapping of ODS-AM may be changing its selectivity and order of impurity might be shifting.

warm regards,
A.L.N. MURTHY
CHIEF EXECUTIVE
CHEMINDIA/HYDERABAD
TEL:+91-40-55904780/ 55904781