Cost savings result from the use of non-dedicated instrumentation with little modification of either instrument. Off-line coupling is really fraction collecting. Most commercial CE instruments can collect fractions using built-in software for peak selection. Alternatives to the fraction collection systems built into many commercial CE instruments exist. An electrical connection is introduced to the central channel before the end of the capillary, permitting grounding of the capillary away from the terminus.
Droplets form at the end where they can be collected for further analysis.
However, reproducibly forming the crack is a difficult manufacturing problem, and the velocity of analyte zones changes after the crack. Losing the electroosmotic driving force at the crack can cause uncertainty about when the zone will elute from the end of the capillary for collection. Alternative 2 is depositing the material on membrane surfaces. For example, the end of the capillary touches a rotating disk of PVDF on top of grounded filter paper, depositing the material directly on the membrane. However, it can be difficult to select a membrane that will bind all substances of interest, and removing sample from the membrane requires additional handling.