ASI QuickSplit™ Post-Column Adjustable Flow Splitters

Description

Unlike conventional splitters that use long lengths of capillary tubing, the ASI QuickSplit Adjustable Flow Splitter uses fluid resistors to achieve a wide range of split ratios. The flow path of the QuickSplit Adjustable Flow Splitter contains two fluid resistors that form a parallel flow path. The low flow rate stream passes through a fixed resistor cartridge, while the high flow rate stream passes through an adjustable fluid resistor (metering valve). The ratio of these two resistors creates the split flow ratio. The compact fluid resistor elements are designed as cartridges for easy replacement with resistance values (L2) rated in PSI/mL/min. Because of the extremely low internal volume of the fluid resistors, the solvent composition in both resistors at any instant in time is the same,and therefore viscosity changes associated with gradient runs do not impact the split ratio. Due to the rugged design, the split ratio repeatability is +/- 1 % of setting, and unlike alternative splitter valves or tees, will not be affected by actions that effect input flow such as turning the pump off and on, or pressure spikes. Because the QuickSplit Adjustable FlowSplitter incorporates a metering valve, split ratios can be changed frequently with flow changes that are stable and reproducible. The QuickSplit Adjustable Flow Splitter will create split ratios that are not affected by changes in solvent viscosity or pressure and provides direct real time control over split ratio optimization.

Schematic flow diagram of the QuickSplit™ Adjustable Flow Splitter
L1=Adjustable fluid resistor (metering valve)
L2=Fixed fluid resistor (resistance value varies depending on cartridge rating)
R=Split ration = Q1/Q2=Resistance ration =L2/L1

Since the flow rate is indirectly proportional to resistance, changing the resistance in either flow path results in a change to the split ratio. Changing resistance is accomplished by adjusting the metering valve on the high flow rate channel or exchanging the fixed fluid resistor cartridge in the low flow rate channel with a resistor cartridge which has a different resistance rating. Adjusting the metering valve is analogous to changing the capillary tubing length or diameter on conventional tee type flow splitters. The QuickSplit Adjustable Flow Splitter has a convenient mounting bracket and hand adjustment knob to control the split ratio. The split ratio is adjusted by turning the adjustment knob. Split ratios are increased by turning the adjustment knob clockwise, and decreased by turning the knob counter-clockwise. Split ratios are not affected by changes in solvent viscosities or pressure, which makes this product suitable for gradient applications as well as isocratic. The QuickSplit Adjustable Flow Splitter is shipped configured for either post-column or pre-column applications.

610 Series Note: ASI has developed a new design of Adjustable Flow Splitter, which is the 610 series. The 610 series splitters provide ASI customers with extended dynamic range, precise split setting and reduced dead volume. In particular, the Vernier scale feature enables the users to set splits reproducibly and to operate the adjustable knob smoothly. The outside dimensions (4.8" h x 4" w x 5.1" d) are almost identical to the old 600 series.

Post-Column Details

Post-column splitting is fairly straight forward. Like pre-column flow spitting, any significant additional pressure (resistance) down stream from the splitter may affect the split ratio. Post-column devices also contribute to chromatographic dispersion so care must be given to connecting tubing and fittings, especially at low flow rates.