Sodium laurly sulfate use as ion pair in Mobile phase

[surajjadhav]

I am using SLS as ion pair in mobile phase with potassium dihydrogen phosphate but getting nise in chromatogram, please any one suggest the solution or which other Ion pair can i used?

[M Farooq]

I am using SLS as ion pair in mobile phase with potassium dihydrogen phosphate but getting nise in chromatogram, please any one suggest the solution or which other Ion pair can i used?

Sodium lauryl sulfate forms a precipitate with potassium ions, often quantitatively under the right conditions. The solids or colloids passing through your detector must be generating baseline disturbance.

Regards,

[kubowicz.tomasz]

Hello

As ion pair reagents are difficult to remove from column you should use dedicated column for your method. Do you use this column for other methods? (non ion pair)
Please provide more details about your method (parameters) and instrument (model, pump details). It really matters

Regards

Tomasz Kubowicz

[Vlad Orlovsky]

Hello

As ion pair reagents are difficult to remove from column you should use dedicated column for your method

....and that is why there are mixed-mode columns, where ion-pairing reagent is attached to the surface of silica. You don't need to dedicate any columns for IP and all your methods become fully MS and preparative chromatography compatible

[mattmullaney]

Good Morning,

If you're committed to a column (Vlad has a good point) and want to try other additives, why not try perchlorate, hexafluorophosphate or tetrafluoroborate?

J Chromatogr A. 2005 Jan 28;1064(1):9-18. Reversed-phase high-performance liquid chromatography behavior of chaotropic counteranions. Kazakevich YV, LoBrutto R, Vivilecchia R.

Abstract
The retention behavior of inorganic liophilic anions in reversed-phase HPLC columns was studied. Usually, the addition of these ions to the mobile phase influences the retention of protonated basic analytes similar to the effect of amphiphilic ions (ion-pairing agents). The nature of this influence is the subject of this paper. HPLC retention of perchlorate (ClO4-), tetrafluoroborate (BF4-), and hexafluorophosphate (PF6-) ions was studied on six columns with different bonded phases including alkyl, phenyl and perfluorophenyl phases. The effect of the mobile phase ionic strength on the retention of liophilic ions was investigated. The influence of the type of organic modifier, acetonitrile and methanol, on the retention of inorganic ions was also studied and interpreted on the basis of adsorption from solutions. Semi-empirical expression is suggested for the description of the retention profile of studied liophilic ions versus the eluent composition. Significant retention of these ions is observed in acetonitrile-water eluents. Multilayer-type adsorption of the acetonitrile on the reversed-phase surface and its strong dispersive (or pi-pi) interactions with liophilic ions are responsible for significant retention of these ions. This accumulation of liophilic ions in the adsorbed layer on the surface of reversed-phase material introduces an electrostatic component in the retention of protonated basic analytes.

Please, see what you think, and thank you.