Flow Injection Tutorial

On the other hand, the two stage configuration of low pressure pFI manifold, combined with high pressure HPLC section is more versatile. Low pressure system ( miniSIA-2 instrument (1.4.3.) is interfaced with high pressure module (area shaded in red), by means of flow adjuster (FA), into which low pressure system delivers flow at a slightly higher flowrate, that the one aspirated into high pressure pump (P3). Because samples pass through this pump on the way to the column, the low internal volume of miliGAT pump (50 microliters,), is the essential component of this design, but it still imposes a limit on, how small sample volumes can be, in order to be reproducibly delivered on the column. Also because miliGAT pump is certified to pressure of 500 psi., it is suitable to serve only short (up to 100mm long) chromatographic columns, including monolithic and columns packed with fused-core particles (4.1.6.)

The two stage configuration can be modified to accommodate columns that require higher pressure by removing P3 and by replacing the flow adjuster (FA), by two position injection valve, the sampling loop of which, will capture the sample to be delivered on the column by high pressure syringe pump. In this way low and high pressure flow paths are independent, and therefore low pressure system can be rinsed while on column separation takes place. Synchronization of functions of low with high pressure module that comprises the pump , valve, column and flow cell will be facilitated by FLOpro software that controls miniSIA-2 instrument. Note that this design is the same, as if miniSIA-2 instrument was interfaced with a conventional HPLC instrument, but because these instruments are likely to use different software platforms, their functions will have to be synchronized.

Versatility of two stage manifold design, makes this configuration preferable. Interfacing of low with high pressure section allows rapid flushing of upper manifold, while separation column is bypassed. Selected segments of solution, captured from the passing carrier can be diverted onto the column. As in pFI work, deionized water should be used as a carrier, because it will perform efficient washout, it will fill pumps and channels during idle periods and thus facilitate startup of the system. Additional components can be integrated into low pressure section. An example is inclusion off solid phase extraction column (SPE) to be used for sample preconcentration , and hyphenation of HPLC. The feasibility of operation of SPE column in low pressure configuration has ben experimentally verified, (3.2.1.), while efficiency of combination of SPE with HPLC has recently been demonstrated (P. Chocholous, D. Satinsky, P. Solich, 2019)

It is unusual, in analytical chemistry, to present a novel concept without experimental proof. And should we attempted to submit this material for publication in a Journal, it would be frown upon by both editors and referees. Therefore we present it here because we can, because it is suitable for OUTLOOK , and because we hope that it will inspire others to pursue this line of research.

© Copyright September 2019. by

Jarda Ruzicka ( Honolulu) Petr Chocholous ( Hradec Kralove) Graham Marshall (Fox Island)

References and Selected Publications.

J. Ruzicka & G.D. Marshall, Anal. Chim. Acta, 237, 329, (1990)

D. Šatínský , P. Solich , P. Chocholouš , R. Karlícek : Anal. Chim. Acta, 499 (2003) 205-214.

J. Ruzicka, Talanta 176 (2018) 437-443.

P. Chocholous, D. Satinsky, P. Solich, Talanta 204 (2019) 272.