Syringe-based systems

Resolution Stepper motor divides volume into 100,000 steps Limitations of syringe-based systems ... 

The concept of an integrated micro-fluidic-based system has now been developed (Zhang et al. 2006), with an example shown in Fig. 7. This particular system is based on conventional chromatographic instrumentation and employs a multi-valving system, located between two syringe pumps, shown in the foreground, to enable the introduction of multiple reagents from an auto-sampler to be loaded onto the micro-reactor. Because of the low diffussional distances obtained in this sys-... 

Basic SFE System. The base system used, (Isco SFE System 1200), consisted of a dual-chamber extraction module, 2.5 ml and 10 ml volume extraction cartridges, a 260 ml capacity syringe pump, a pump controller, and all the hardware used to connect the system to a C02 supply and collect the extracts. The syringe pump used was capable of 90 ml/min liquid flow at pressures up to 4500 psi and 45 ml/min flow at pressures between 4500 and 7500 psi. The extraction module was capable of withstanding pressures up to 10,000 psi and temperatures up to 150°C. 

Modifier Addition System. In the case where a continuous supply of modifier was desired, the base system was upgraded to perform continuous modifier addition with the addition of a second syringe pump module and a valving package (Isco SFE System 2200). The valving package consisted of two check-valves, a mixing tee, and the hardware necessary to install them in the system. Both pump modules were... 

The capillary tube-based system employs a set of tiny tubes of fixed length. When a tube is dipped into a source liquid, the tube is filled with liquid via capillary action, then compressed air blows the liquid in the tube into the destination well. Both types of tools can deliver nanoliter volumes with reasonable accuracy and precision. The limitation is that they can only deliver a fixed volume without changes of pin or tube settings. New syringe-type liquid handlers capable of delivering 100 nL or less are now on the market. 

Supercritical fluid chromatography has at least one extra control variable compared to HPLC. Many people still associate the name SFC with syringe-pump-based systems in which pure carbon dioxide was used with pressure programming. Modern SFC sometimes still operates in this manner but only for nonpolar solutes. SFC is somewhat different from HPLC. It is useful to discuss the relative effects of different control variable on retention and selectivity. The relative effects of several control variables are represented schematically in Fig. 5. 

Ammonium Waste waters, river waters Membraneless GD UV-Vis 2.20 mg L-1 Multi-syringe flow system BTB acid—base indicator solution as the acceptor stream donor stream stopped during gas diffusion [523]... 

The general operation of the pilot scale reactor has be previously described by Pareek et. al. [3]. However, modifications were required to allow the injection of the gas and liquid tracers, and their subsequent detection at the outlets. The liquid tracer, 5mL Methyl blue solution (lOgL" ), was injected via a syringe inserted into the liquid feed line. Outlet samples were measured with a Shimadzu 1601 UV-Vis Spectrophotometer at a wavelength of 635nm. A pulse (20mL) of helium gas tracer was introduced using an automated control system, with the outlet concentration monitored in real-time with a thermal conductivity detector. Runs were carried out based on a two-level... 

Figure 6 Schematic diagrams of atypical high-pressure SF-CL systems based on special mixing modes (a) system based on conventional propelling and stopping syringe and (b) system based on liquid chromatographic (LC) pumps and stopping the flow before the mixer (M). V, six-ports valve. (Adapted from Refs. 33 and 34.)...

In addition to the commercially available systems, several authors have described laboratory-built systems using commercially available components from companies such as Upchurch Scientific (Oak Harbor, WA). One of the first reported laboratory-built micro-bore HPLC systems was described by Simpson and Brown, which was a simple adaptation of a standard HPLC system to accept micro-bore columns built from guard columns. A complete system has been described based on dual microdialysis syringe pumps (CMA Microdialysis, Chelmsford, M A) or dual syringe pumps (Harvard Apparatus, Inc., Holliston, MA), a microinjection port, and a micro-column the latter components being obtained from Upchurch scientific (Figure 3.5). This system was coupled with a laser-induced fluorescence (LIF) detector and used to measure neuropeptides in sub-microliter samples. A further modification of this system was built to perform immunoaffinity isolations of biomedically important analytes from clinical samples. ... 

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