Is It Possible To Convert a Shimadzu High-Flow LC to a Microflow LC System?

For research use only. Not for use in diagnostic procedures.

Answer

In order for a microflow LC system to perform optimally, the correct LC hardware must be installed. For example, a high-flow Shimadzu LC-20AD system cannot simply be converted to a microflow system because the 20AD is not equipped with the correct type of solvent mixer. The mixer in this case, a 5 µl mixer, is not reliable enough to deliver a robust gradient for microflow rates from 5–10 µl/min. It can only deliver a reliable isocratic microflow rate. If the 5 µl mixer is used with LC methods that involve gradients, then the retention times for analytes may show severe retention time shifts. The picture below describes the flow rate limitations and the flow rate specifications for the Shimadzu LC-20AD system. 

While the above table suggests a possible flow rate from 5–10 µl/min, the accuracy of the gradient concentrations over time will be compromised by at least ±1–2%. It might be working better for a simple isocratic infusion type experiment. 

In addition, to run a microflow method successfully, the autosampler loop needs to be small; using a 100 µl or 50 µl sample loop is not recommended. The tubing inner diameter and the ESI probe can also be adjusted, but not the robust gradient delivery. Therefore it is not recommend to convert such a system to a microflow system without any other hardware changes.