Packed Tip Versus Column Plus Emitter for PepMax™ Columns

Packed tip columns are usually regarded as having better performance than a separate packed column coupled to an ESI emitter (and this is definitely the case at flows below 300nl/min or when a column is not properly connected to a well made ESI emitter).  The advantages of a separate column and emitter are in ease of handling and robustness, as a fouled or broken tip only results in replacement of the emitter, rather than the replacement of the much higher cost column.

Although the PepMax material can be custom packed in the Packed Tip column format, PremierLCMS has standardized on providing packed columns that couple seamlessly to ESI emitters.  Our results show that there is no impact on resolution, sensitivity or throughput at flow rates above 250nl/min when using an equivalent PepMax packed tip column or a well designed column plus ESI emitter.

The trace above shows the separation of 5 femtomoles of a BSA digest in a 5 minute gradient at 300nl/min on a 75µ ID x 80mm 1.6µ 100Å PepMax C18P HT packed tip column (blank packed tip column from MicrOmics Technologies).

  

The trace above shows the separation of 5 femtomoles of a BSA digest in a 5 minute gradient at 300nl/min on a 75µ ID x 80mm 1.6µ 100Å PepMax C18P HT  column coupled to a 20µ ID x 50mm ESI emitter (MicrOmics Technologies).  

 

Coupling a Nano Capillary Column to an ESI Emitter

The trace below shows a TIC trace of 5 femtomoles of a BSA digest using a poorly coupled column and ESI emitter using a 1/16" OD x 0.016" ID Tefzel sleeve to sheath a 20µ ID x 50mm emitter to a 1/16" column outlet.  Trace leaks can cause micro bubbles in the flow stream resulting in excess noise in the TIC signal (making peptide MSMS IDs very difficult at low femtomole levels).

 

This trace below shows a TIC trace of 5 femtomoles of a BSA digest using a properly coupled column to a 20µ ID x 50mm emitter via a ZDV 1/16" to 365µ reducing union.  The low noise generated by a well made ESI emitter coupled to the same column above shows excellent response in the TIC signal for trace level samples (making peptide MSMS IDs possible).