Chromatography Forum

I have developed an LC method for 2 sulphonic acids (Triflic and benzenesulphonic) using anion exchange (Spherisorb SAX).

However when I try to monitor low levels using MS I'm getting a lot of noise from column bleed.

Are there any more modern phases less susceptible to bleed ?

Could I get round this using other modes of detection ie electochemical ?

Advice needed before I start randomly ordering

Thanks.

My suggestion would be to redevelop the method on a resin-based column, such as Waters IC-Pak anion HR column or similar. Resin-based columns are expected to show much less bleed than the column that you are currently using.

HILIC is an alternative for triflic and benzenesulphonic acid. A good thing with HILIC compared to ion exchange is the possibility of using high organic solvent/low ionic strength mobile phases which allows simple connection with MS. This will give you a higher sensitivity and also much less noise from column bleed.

To exemplify this, I've attached an application note on separation of organophosphonate nerve agent metabolites, that is phosphonic acids with different substituents. In this example (isocratic) you will see that as the analyte becomes more polar (less hydrophobic substituents) it gets more retained.

This application can easily be improved by a gradient but it is suitable as an illustration on how a small change in a side change can increase/decrease retention on the column.

http://www.sequant.com/sn/ufiles/SeQuan ... 00-18A.pdf

If you have not yet evaluated HILIC, I'd suggest that you try our ZIC®-HILIC phase, and if an alternative detection mode is of interest, I'd suggest you combine it with ELSD.

Stanlee,

I just finished the this separation minutes ago.

Conditions:

Column: Acclaim Mixed-Mode WAX-1, 150x4.6 mm
Isocratic
Mobile phase: MeCN/0.1 M NH4OAc, pH5 v/v 80/20 (20 mM NH4OAc total)
Flow rate: 1 mL/min
Temperature: 30 C (ambient works, too)
Detection: ELSD (Sedex 85, 50 C, gain set -8)

Result:
bezene sulfonate - 10.9 min, As-0.94, Eff. 17,719 plates
triflic - 12.0 min, As-1.05, Eff. 13,882 plates
resolution - 3.01

Other information:
150x2.1 mm column format is available.
A method for the Analysis of melamine and cyanuirc acid by LC-MS using this column was devloped successfully.

Please let me know if you need additional information.

Stanlee,

I just developed a method for benzene sulfonate and triflate moments ago. Here are the details:

Conditions:
Column: Acclaim Mixed-Mode WAX-1, 5 µm
Dimension: 150x4.6 mm
Mobile Phase: 80/20 v/v MeCN/0.1 M ammonium acetate, pH5 (20 mM total concentration)
Temperature: 30 °C
Flow Rate: 1 mL/min
Detection: ELSD

Results:
Benzene sulfonate: 10.9 min; As-0.94; Eff.-17,719 plates
Triflate: 12.0 min; As-1.05; Eff.-13,882 plates
Resolution: 3.01

Other information:
150x2.1 mm column format is available
A LC-MS method for melamine and cyanuric acid has been developed on this colulmn
Product information: http://www1.dionex.com/en-us/columns_ac ... 48519.html