Chromatography Forum

ok so you wrongly named peak in the first picture as impurity C and as seen on SST chromatogram retention times don't match, but SST looks ok (i got my hands on BP:) )

what is now your responsibility is to check purity of your sample
1. you can run pda peak purity of mesna peak with waters column
2. or develop ortoghonal separation (MS friendly useful)

What is the sample dissolved in and what is the mobile phase?

dissolved in mobile phase

From BP 2009


Related substances:

Test solution Dissolve 0.10 g of the substance to be examined in the mobile phase and dilute to 25.0 ml with the mobile phase.

Reference solution (a) Dissolve 4.0 mg of mesna impurity C CRS in the mobile phase and dilute to 50.0 ml with the mobile phase. Dilute 2.0 ml of the solution to 20.0 ml with the mobile phase.

Reference solution (b) Dissolve 6.0 mg of mesna impurity D CRS in the mobile phase and dilute to 50.0 ml with the mobile phase.

Reference solution (c) Dilute 3.0 ml of the test solution to 10.0 ml with the mobile phase.

Reference solution (d) Dilute 1.0 ml of reference solution (c) to 100.0 ml with the mobile phase.

Reference solution (e) Dilute 6.0 ml of reference solution (c) to 20.0 ml with the mobile phase. To 10 ml of the solution add 10 ml of reference solution (a).

Column:
— size: l = 0.25 m, Ø = 4.6 mm;
— stationary phase: octadecylsilyl silica gel for chromatography R (10 µm).
Mobile phase Dissolve 2.94 g of potassium dihydrogen phosphate R, 2.94 g of dipotassium hydrogen phosphate R and 2.6 g of tetrabutylammonium hydrogen sulphate R in about 600 ml of water R. Adjust to pH 2.3 with phosphoric acid R, add 335 ml of methanol R and dilute to 1000 ml with water R.

Flow rate 1 ml/min.

Detection Spectrophotometer at 235 nm.

Injection 20 µl.

Run time 4 times the retention time of mesna.

Relative retention With reference to mesna (retention time = about 4.8 min): impurities A and B = about 0.6; impurity E = about 0.8; impurity C = about 1.4; impurity D = about 2.3.

System suitability Reference solution (e):

— resolution: minimum 3.0 between the peaks due to mesna and impurity C.

Hi Krickos,

Has anyone asked for the method description, or is it some kind of a cunning argument?

Best Ragards

Well, krickos suggested earlier:
"Well for me it is pretty clear that the Waters column should be used."

This chain is another example of how regulation can fail abysmally. Please you guys in the pharmaceutical industry: Have mercy with us pill swallowers and do science rather than law.