Peptide sequencing labs frequently use sodium dodecyl sulfate (SDS) or other detergents to solubilize peptides and proteins from electrophoresis gels. Unfortunately, the SDS in the samples often ruins subsequent runs by reversed-phase HPLC (RPC). Moreover, in automated peptide sequencers, SDS in samples can lead to bubble formation in the sample intake lines, which blocks further sample intake. SDS can also accumulate on the PVDF membranes used for sequencing, washing off at an inconvenient time. All in all, it's a good idea to get it out of your samples. The Nest Group offers both an in-line as well as an off-line technique to accomplish this:

By RP HPLC:

The 10SDS, 4SDS, 2SDS and 1SDS guard cartridges are 5µm, wide-pore hydrophilic materials packed into 10x10mm, 4.6x20mm, 2.1x20mm and 1.0x10mm cartridges, respectively. They selectively remove SDS from peptide mixtures, and are used as guard cartridges with reversed-phase columns.

When one of these cartridges is used with a RPC column, conventional TFA/acetonitrile gradients can be used. Accumulated SDS is reportedly washed off the SDS removal cartridges by levels of acetonitrile higher than 70%, allowing SDS containing and non-SDS samples to be run sequentially.

See SDS Removal Cartridges for Part Numbers and Prices.

By HILIC LC or micro-SPE:

Alternatively, use of a HILIC HPLC technique for SDS or other detergents allows direct LC-MS analysis with up to a 40x increased sensitivity over RPC.

HILIC pre-treatment of the sample with a MiniSpin micro-SPE or TIP (p/n: SUM HIL, or STU HIL) column can remove detergents and contaminating dyes prior to injection onto your RPC column or for direct ESI-MS infusion. As an example, 8.6% SDS was removed by microSPE from a peptide mixture prior to RPC analysis.

The size of the column is determined by the capacity needed for the retained molecules only, since detergents come off during the loading (in 60-80% ACN) and do not take up capacity on the HILIC cartridge. Peptide is eluted at 0% ACN and is thus ready for RPC loading directly, or for direct ESI-MS analysis.

Operating instructions are available for individual Spin columns (p/n: PUMSCHY1203 or PMASCHY1203) or for packages of UltraMicroSpin, MicroSpin and UltraMicro TIP HILIC (p/n: SUM HIL and SEM HIL, or STU HIL) columns.