March 5, 2008

Among the many liquid handling systems on display at Pittcon 2008 in New Orleans this year, the GX-281 stood out for its combination of time- and cost-saving features with compact design and powerful operation.

Intended for injection and fraction collection, the GX-281 features a large-bed capacity, and occupies 90 cm of linear bench space. Despite the compact design, the instrument can hold up to six racks for a capacity of 12 microtiter plates, 576 tubes of 9 ml or 1.5 ml vials. It can also accommodate tubes or bottles and NMR tubes as high as 220 mm.

The GX-281 uses an integrated bar code scanner for automatic bed layout generation and pre-run bed verification. The Z-arm can accommodate vessels of 220 mm in height, and an optional 200 mL/min fraction collection valve is located on the base of the Z-drive.

New solvent delivery method

The stand-out feature by far of the GX-281 is its handy delivery system: there are no syringes to replace or change to accommodate various volumes and flow rates. The solvent delivery system allows for a large dynamic range of 5 µL to several 100ml and flow rates of 1 µL/min to 25 mL/min.

The preparative solvent system is a bi-directional pump that significantly reduces aspiration and dispensing times compared to a conventional syringe pump. Because it can instantly go from aspiration mode to dispense mode, there is no time spent drawing up the solution, switching a valve and then dispensing the solution. The solvent system incorporates a large-bore solvent selection valve for up to five different rinse reservoir solvents. A sixth position is reserved for waste, and is always inline when the pump is in aspiration mode. This ensures that sample or contaminant solvent cannot be aspirated back into the system fluids.

All GX-281 injection modules feature a continuous flow path design for flow rates up to 200 mL/min. The GX-281 can accommodate large injection volumes up to 25 mL with minimal sample waste and carryover.

Revised rinse station

A new rinse design incorporates a flowing jet wash and can accommodate up to three different solvents. There are two rinse locations for each position close to the injection valves for fast cycling times and less X/Y movements. Each rinse location can accommodate three flowing jet wash stations. Each jet station can accommodate a different solvent, allowing for up to three separate solvents to be used in the rinsing process. If the rinse pump is not used, the rinse station performs a static rinse using the solvent delivery system. The rinse stations are available in three heights: 125, 175 and 210 mm.

Expanded flow options

Gilson has introduced two new injection options for the GX-281, both of which feature a continuous flow path design for flow rates up to 200 ml/min. Switching injection valves at preparative flow rates may cause pressure spikes which can ultimately rupture tubing and/or cause fitting to burst, resulting in surpassed high pressure limits. The continuous flow design allows liquid flow to continue even when the injection valve is switching between load and inject.

1. The Z-injection module is mounted on the Z-drive and the probe is plumbed directly to the injection valve, eliminating the need for injection port. This removes one potential source of plugging and carryover. It also allows for faster injection cycle times, reduced injection rinsing requirements and fraction collection of early eluting peaks.
2. The direct injection module is a classical injection module that is fixed and stationary on the bed. The Gilson design features an injection port that connects direct to the injection valve. This eliminates the need for calibrated tubing, which is a source of plugging, dead volume and carryover. Two modules are available: one for 1/16" OD tubing and one for 1/8" OD tubing for sample loops up to 25ml.

Gilson Instruments’ product presentation page includes a video demonstrating the GX-281: http://www.gilson.com/Products/product.asp?pID=268#

SOURCES: Gilson, Pretech Instruments, Lab Technologist