CPSA Digest 2003

Day 3

Vendor/Exhibitor Session

A Staggered Elution LC/MS/MS System Using Integrated Control Software

Waters has demonstrated the application of an integrated software interface for staggered chromatography using MassLynx 4.0, SP2. This new functionality of MassLynx allows for increased throughput by a factor of four while maintaining sensitivity and data quality.

Staggered chromatography differs from the familiar MUX interface in the following way. MUX was developed for drug discovery applications to increase sample throughput when a large range of compounds need to be accommodated using a generic LC method. The system enables true parallel LC-MS and the entire LC run is acquired for each sample. In contrast to MUX, staggered chromatography is suitable for drug development applications. In drug development, the LC method for a long term study is well defined. Only part of the run, where the peak is eluting, needs to be acquired. In this situation staggered chromatography can increase sample throughput using a standard Z-spray source, as shown below.

ML4.0, SP2 is an integrated software package that has full independent control of four HPLC pumps and full control of the autosampler. In contrast to other commercial systems where the mass spec is running in the contact closure mode and the mass spec control software is basically a slave to the HPLC software, ML has total control of all the peripheral equipment. Any change to the inlet method or the sample list is logged in the audit trail. This is a very favorable situation in a regulated environment. In addition, data for each sample are acquired into separate data files. As a result, there is no additional compliance concern when the system is operated in the staggered elution mode.

The system consists of four Waters 1525u pumps, which are high pressure mixing, binary gradient pumps. These pumps are called micro because they are designed for flow rates between 50 μL/min to 300 μL/min. An important element of the system is the CTC autosampler with four injection valves, a dilutor for rapid washing and a self-wash station. This arrangement dramatically reduces the post-injection wash time as well as sample carryover. A 9-way flow selector valve is also part of the system.

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