Tadalafil Diastereomer

[Fernando]

Hi all

I have problem to separate Tadalafil from the 6R,12aS diastereomer of Tadalafil, in the USP 37 indicates L1 that is C8 but I cannot obtain any secondary peak.
I´ll try with C18.
Anyone has experience in Tadalafil?

Thank You

[sga]

Chiralpak AD for Enantiomeric purity !!

[HPLCaddict]

I have problem to separate Tadalafil from the 6R,12aS diastereomer of Tadalafil, in the USP 37 indicates L1 that is C8 but I cannot obtain any secondary peak.
I´ll try with C18.

USP L1 is C18, not C8. C8 would be L7.

[sga]

L51.

[Fernando]

Thank you sga and HPLCaddict for your replies

You were dead right the column is L7 (C8) but my problem is in the assay of tablets of Tadalafil. In the system suitability the USP requires a resolution of NLT 3 between the peaks of Tadalafil and the diastereomer (obtained attacking Tadalafil in basic media).
I tried with 3 different brand of columns with no succes, remember it is the assay! In the monography of Tadalafil drug susbtance this requirement does not exist.

I´m sorry if I was not clear in my first posting.

Fernando

[HPLCaddict]

If you're bound to the USP, using a C18 instead of C8 as described in the monograph is an absolute no-go! You may alter column dimensions, particle size, flow-rate etc. according to the limits described in the USP, but using a formally different stationary phase is a red flag.
Did you try exactly the column described in the USP - Zorbax SB C8, 150x4.6mm, 3.5µm? If not, I would try this one.

[mattmullaney]

Agree with HPLCAddict...and if you're not bound by the USP, try out Agilent's Bonus-RP or another polar-embedded phase, you'll likely do much better. These polar-embedded stationary phases work pretty well with the diastereomers created from forming DNPH-aldehyde derivatives.

Best wishes!

[Fernando]

Thank you mattmullaney and HPLC for your replies

Yes I´ll try with the Zorbax SB C8.

Fernando

[sucrose]

I too am having problem with the diastereomer peak. It does appear at all in assay but appears in the dissolution (whereit is not neeeded)

By USP 39, It is supposed to be generated in situ by adding 5N NaOH to 25 ml of std solution and letting sit still for 30 and then neutralizing to pH 7 by Trifluroaceti acid. Its relative retention time to tadalafil is 1.2.

My std soln has primary peak area is 6700000 and the NaOH treated one has the same of 4680000. The retention time is 14 min. But i get no other peak until 30 mins.


Someone help me pls
My HPLC parameters for assay is

Column: Sunfire C8 end capped, 4.6 mm diameter, 5 uM particle size, 150 cm length
Mobile Phase : Acetonitrile:H2O:TriFluroacetic (35:65:01)
Flow: 0.7 ml/min (Adjusted from 1ml/min to account for USP recommended column of 3.5 uM particle size)
Temp : 35
Inj vol : 10 ul
Solvent for Assay : ACN:H2O (1:1)
wavelength : 285

My HPLC parameters for dissolution is
Column : same as Assay
Mobile Phase : MeOH:H2O (1:1)
Temp : 40
Inj vol : 50 ul (but i used 10 ul as was done during assay )
Flow: 1.4 ml/min (Adjusted from 2ml/min to account for USP recommended column of 3.5 uM particle size)
Solvent for std soln : ACN:H2O (1:1)
wavelength : 225


maybe its the wavelength which is not suitable but I don't suppose USP got it wrong. How do i make the diastereomer appear in the assay

[sucrose]

update :
it seems the diastereomer peak does appear when i switched to normal C8 column instead of the end capped one. However the relative resolution is at 1.06 instead of 1.2 as given in the criteria

Altering pH or flow did not change the relative resolution at all!
What else can i do?