How to Multiplex the Technology to Increase Throughput in LC/MS Analysis

The popularity of mass spectrometers (MS) in the food, clinical research and pharmaceutical markets has pushed labs to seek ways to improve the speed of their liquid chromatography (LC), thus increasing the throughput of their MS.


Problem: The popularity of mass spectrometers (MS) in the food, clinical research and pharmaceutical markets has pushed labs to seek ways to improve the speed of their liquid chromatography (LC), thus increasing the throughput of their MS. As mass spectrometers are used for a wider array of applications, labs are also seeking ways to improve the flexibility of their LC. Even while striving for the two above mentioned improvements, most labs are under budget constraints and have little or no more money to spend. This customer demand has driven suppliers to develop new products and techniques to help customers achieve their goals.

The Thermo Scientific Transcend Multiplexing System

Solution: An innovative technology for increasing throughput is multiplexing. Multiplexing is the ability to simultaneously run multiple LC systems into a single mass spectrometer. This novel technique takes advantage of the time a MS typically spends idle by time-staggering the LC methods so that each one elutes in succession. The MS is dedicated to each LC elution, thus providing the same quality data as a single LC/MS method. A typical LC/ MS method using multiplexing will gain a two- to four-times throughput increase while still using a single MS. Therefore, productivity is increased substantially, cost increase is low and there is no negative effect on data quality. Note that some multiplexing products do not time-stagger the samples into the MS. These LC systems alter the pump pressure or sample the eluting stream. Both result in poor chromatography or reduced data.

A leading pharmaceutical company recently approached vendors in an attempt to find a solution to increase the throughput of their LC/MS. Their expected chromatography and analysis time was about 85 seconds, a throughput of 42 samples per hour. The company required increased throughput without any loss in data quality and without purchasing more mass spectrometers. Using the Thermo Scientific Transcend LX-4 system, they were able to quadruple the throughput to 168 samples per hour using a single MS/MS. An initial test run was setup and 6912 samples were run unattended over the weekend in 41 hours.

Some of today’s multiplexing systems provide an additional benefit to complement their increased throughput. When each of the LC systems is individual and separate, they can be run simultaneously to increase throughput (as mentioned above) or each system can be set up and validated to a separate assay, allowing a scientist to choose which method to run without any change-over or set-up. With advanced multiplexing software now available, an LC/MS method can run on a single channel while another is started on any of the remaining LC systems. Even though the methods are started at different times, the multiplexing software will take advantage of the idle time of the MS and dynamically time-stagger the newly introduced method with the existing method(s) to achieve maximum throughput. Advanced multiplexing software can make dynamic decisions how to order samples to the MS to maximize throughput by priority status, time or system availability. For example, one option provides optimal performance for multimethod runs by starting the new samples as soon as the MS data collection window allows. Another option completes all the samples in a batch with multiplexing before proceeding to multiplex the next batch.

The ability to run multiple methods on a two- or four-channel parallel system provides flexibility to meet today’s demanding lab workflows. Demonstrated on a Transcend™ TLX-2 system, a method for simultaneous analysis of opiates and benzodiazepines for forensic toxicology testing was set-up. The system was used to run two LC-MS/MS methods, one for each class of compound. While different analytical columns were used for each method, the system utilized one set of solvents and one MS. Using Thermo Scientific Aria operating software, multiplexing technology and data windowing was used to enable these methods to be run simultaneously and robustly, leading to increased throughput with minimal operator intervention. Along with multiplexing, these methods also utilized Thermo Scientific TurboFlow technology for automated sample preparation allowing direct injection of the biological matrices into the LC/MS system.

Multiplexing products can help customers to substantially increase their LC/MS throughput without any loss in data quality and with a single MS. The technology also allows customers the flexibility to validate multiple methods on a single LC/MS multiplexing system, allowing scientists to choose and run completely separate methods without any change-over or set-up on their MS. These separate methods can be started at different times and will still run simultaneously to increase throughput.

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Categories: How it Works

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Published: October 1, 2009

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So far, nearly 5,000 grants totalling over $1 billion have been awarded by NIH. Most have been awarded to research labs at large universities and small colleges, while some have been awarded to small, privately owned research and product development companies.