Tailing in an IEC method
Posted: Thu Jun 04, 2009 3:26 pm
I developed a gradient IEC method with great peak shape, horrible baseline. But under isocratic conditions, better baseline but there is severe tailing...although we believe that we have enough of the salt to elute all of the NTA.
The analyte is nitrilotriacetic acid. I am using CuNO3 to increase the sensitivity of the molecule as it chelates like EDTA. The stock of CuNO3 was 10mg/mL and we are trying to cut it down to 1mg/mL this morning which should be enough for our lower NTA limit. The problem I am having is accumulating back pressure and tailing of 2.3-2.7, lesser tailing at lower concentrations. Here are the method parameters:
Column = 4.6x150 mm NH2 (tried SAX but too strong)
IV=25µL
FR=0.5 ml/min
MP A = 5mM NaH2PO4 pH = 7
MP B = 5mM NaH2PO4/100mM Na2SO4 pH = 7
MP C = IPA (tried blending in MeCN 2, 5, 10, 15%, no difference noticed)
Column @ 25C (40C makes no difference)
Any suggestions?
The analyte is nitrilotriacetic acid. I am using CuNO3 to increase the sensitivity of the molecule as it chelates like EDTA. The stock of CuNO3 was 10mg/mL and we are trying to cut it down to 1mg/mL this morning which should be enough for our lower NTA limit. The problem I am having is accumulating back pressure and tailing of 2.3-2.7, lesser tailing at lower concentrations. Here are the method parameters:
Column = 4.6x150 mm NH2 (tried SAX but too strong)
IV=25µL
FR=0.5 ml/min
MP A = 5mM NaH2PO4 pH = 7
MP B = 5mM NaH2PO4/100mM Na2SO4 pH = 7
MP C = IPA (tried blending in MeCN 2, 5, 10, 15%, no difference noticed)
Column @ 25C (40C makes no difference)
Any suggestions?