Divergent Techniques Fill Key Applications
Mass spectrometry (MS) has not quite become a routine acquisition for every lab that might benefit from it. Nor are MS instruments yet capable of serving routine users and experimenters equally well. But the characteristics and performance of instrumentation serving high- and low-end applications overlap more now than ever.
High-end MS instrument development is driven by performance, specifically sensitivity, mass accuracy, resolution, and dynamic range. Power users thereby achieve routine results more rapidly or find answers that are unachievable with low-end instruments.
Performance also drives mid- and low-end instrumentation, but these users don’t necessarily require topof- the-line spectrometers to get the job done. With performance a second-tier desirable, mid- to low-end users differentiate among vendors in terms of service, interface, and workflow suitability.
“How those users go about obtaining an answer becomes increasingly important,” says Steve Smith, Ph.D., senior director, MS product management at Waters (Milford, MA). “And it’s not just about ‘ease of use,’ an overused term that is losing its original meaning.”
User-instrument interactions represent the core of a Waters program, “user-centered design,” that puts hypothetical customers in front of instruments in simulated real-world situations before the operating software is written. As a company guide asks and answers questions, Waters films subjects and experts as they interact with the instruments and one another. “This has been standard practice for years in consumer electronics,” Dr. Smith notes.
Waters’ Xevo™ MS instrument line was the first to benefit from user-centered design. Xevo simultaneously mass-quantifies the target analyte and the matrix, which is critical where the sample milieu affects the target’s properties such as suppression or enhancement of ionization or it introduces interference effects.
Dr. Smith likens this approach to applying a zoom lens for the target and a wide-angle lens for the matrix. This concept arose from users who expressed a need for simultaneous quantitative analysis of analyte and background. “This information was there all along. We didn’t have to improve the resolution or sensitivity, just design the instrument more intelligently,” Dr. Smith tells Lab Manager Magazine.
Tandem Analysis Driving MS
Industry-wide, the shift from conventional liquid chromatography (LC) to ultra-high-performance LC (UHPLC) has provided a huge boost to MS as a detection mode. UHPLC is the generic term that describes high-performance LC run on a stationary sub-two-micron particle phase. Waters, which first commercialized the technology during the early 2000s, owns the UPLC® (ultra-performance liquid chromatography) brand.
UHPLC provides improved sensitivity, speed, and resolution at the chromatography end, thereby reducing matrix effects during mass detection, but it places speed demands on the MS instrument, which is why some analysts are switching from quadrupole to time-of-flight (TOF) MS. TOF has the benefit of acquiring spectral data at full sensitivity much more rapidly than a quadrupole instrument can. “That’s why we’re seeing TOF in more routine analyses, for ‘qual-quant’ applications where the exact mass number provides identification and the remaining data provides qualitative information,” Dr. Smith says.
Combining MS and fast LC has fueled adoption of MS by enabling laboratories to process complex samples within normal throughput requirements with no compromise in data quality.
Until relatively recently, the high-performance characteristics of modern MS were available only in very high-priced MS systems, mostly at large companies and core research facilities. For much of its history MS was an expert-based instrument driven by high-end applications.
Reaching Its Potential
While much has changed, and for the better, MS technology has not reached its full potential for serving all modern laboratories that might benefit, says Blas A. Cerda, Ph.D., senior business director for mass spectrometry at PerkinElmer (Waltham, MA). “MS still lags in terms of financial or cost issues and easeof- use requirements for a broad range of laboratories.”
Nevertheless, two recent developments have made MS more broadly attractive. LC single-quadrupole MS systems, particularly integrated with UHPLC and supported by intuitive data processing software, have emerged and provide significantly increased sensitivity and ion source flexibility (e.g., ESI and APCI) with dual probes. The second development is LC-TOF MS systems that offer mass accuracy to 1ppm, five orders of linear dynamic range, increased sensitivity, innovative direct sample analysis front ends, and flexible ion sources with dual probes. “The current generation of single-quadrupole and TOF instruments addresses a wide range of applications and thus allows the laboratory to leverage the investment and operational costs of adopting MS, which results in a cost-effective business model,” comments Dr. Cerda.
A View From The Field
Heribert Dollt, Ph.D., who heads a bioanalytics lab at Hoffmann-La Roche (Basel, Switzerland), uses LC-MS as well as uncoupled (flow injection or nanospray) MS. Because his group makes decisions on new projects based on MS results, control and analytic software need to be robust, reliable, and user friendly. “Unfortunately, we all too often discover quite rudimentary bugs, suggesting that the software was compiled without much input from MS experts.” Dr. Dollt notes “strange things” occurring in the areas of automatic data handling and interpretation, highthroughput analysis, and data deconvolution. He cautions that apparent user-friendliness can mask underlying deficiencies. “Scientists often blindly rely on software-generated results, with a dubious data ‘interpretation’ as the consequence.” Another area of concern is the addition of peripherals such as autosamplers, LC, and fraction collectors, which may lead to “time-consuming surprises.”
Vendors can improve the situation by employing open software architecture and providing facile interfacing to peripheral instruments as well as a more accessible interface for data handling, reporting, and data exchange to a laboratory information management system. The downside: “These tools quite often demand a higher degree of IT expertise, are not very user friendly, or are limited to only report writing.” A more universal tool such as macro recording, which was available on old Macintosh computer systems, “offers flexibility in adding functionality down to the level of instrument tuning,” Dr. Dollt says.
For additional resources on Mass Spectrometers, including useful articles and a list of manufacturers, visit www.labmanager.com/mass_spec