Liquid chromatography-mass spectrometry testing services are now integral to clinical reference laboratories worldwide. Today companies providing liquid chromatography-mass spectrometry services have begun penetrating medium and large-sized regional clinical laboratories and hospitals. Moreover, the applications of liquid chromatography-mass spec services (LC-MS) within bioanalytical laboratories have expanded to several tests ranging from esoteric analytes to high-volume drug testing.
LC-MS method development and LC-MS method validation will always remain crucial for the success of LC-MS/MS services. However, with growing applications, the advantages and limitations of LC-MS/MS testing have now become apparent. Addressing critical aspects of LC-MS/MS method development and LC-MS/MS method validation will be vital for addressing the weaknesses of this technology and increasing its applications for future opportunities. Therefore, this article highlights advanced tools and methods required for LC-MS/MS services.
Enhancing LC-MS/MS Experimental Workflows
The primary inhibiting factors for the rapid adoption of LC-MS/MS instruments in local laboratories are the complexity of the instrument and the manual nature of its workflows. Besides, the initial instrumentation is costly and requires expert technicians with prior working experience in LC-MS systems. Therefore, bioanalytical laboratories should ideally hire technicians with expertise in the systems or have a planned and extensive training period for their existing staff.
Despite several hurdles to the adoption of LC-MS/MS systems in smaller laboratories, they have compelling bioanalytical and clinical benefits for analyzing low molecular weight molecules and substantial savings in reagent costs compared to immunoassays available commercially. Consequently, robotic liquid handlers have improved the preanalytical and analytical workflows of LC-MS/MS systems.
Improving throughput of LC-MS/MS analysis – Despite improvements in ease of use and workflows, LC-MS systems still need improvement in sample throughput. Generally, a single-channel LC system can perform around 70 to 250 tests daily. Although this number may be quite respectable, they are lower compared to the number of tests performed a day by large referral laboratories.
. LC-MS systems can employ the dilute and shoot method. In this approach, the sample is directly diluted and injected into the MS unit without prior cleanup. Such an approach provides analysis of 400 to 1300 samples per working day. However, this approach applies only to a small number of analytes. The time needed for introducing the sample into the LC unit and the time required for chromatography analysis are responsible for limited LC-MS throughput.
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Multiplexed LC systems are an alternative approach to increase the throughput of LC-MS/MS units. These systems have up to four separate chromatography columns operating simultaneously but in an overlapping fashion. Such an approach allows technicians to introduce specimens into the MS unit only when they elute from the chromatography column, thus increasing the throughput of LC-MS units.
Another interesting approach to increase LC-MS/MS throughput is injecting more than one specimen per injection. As low as two specimens directly double the capacity of an LC-MS instrument. Each increase further expands the throughput linearly. However, this approach requires study samples to be modified in a specific manner.
