Trends in miniaturization, particularly in electronics and microfabrication, have brought about a revolution in instrumentation. Benchtop instruments pack greater functionality into ever-smaller footprints and components. Increasingly, analysts perform routine analysis “where the action is”—locations of environmental interest, manufacturing suites, crime scenes, loading docks, and packaging facilities—through transportable instruments.
Convenience comes at a cost, however, as transportables generally lack the dynamic range, sensitivity, resolution, automation capability, and interoperability of their benchtop counterparts. Nevertheless, interest in portable instrumentation is exploding as users seek more real-time, actionable analytics.
Transportable instruments can be roughly divided into two groupings: briefcase-sized portables weighing up to about forty pounds, and handheld instruments in the one-to-five-pound category. All transportables exploit low-cost connectivity via data cards, RS-232 or USB cables, pen drives and, in some cases, wireless networks. Data processing occurs either on the device, through upload to personal computer software, or both.
Notable exceptions exist, but one can generally think of benchtop, portable, and handheld instruments as analogous to desktop, laptop, and handheld computers, respectively. The analogy holds for both portability and capabilities. Thus the performance gap between portables and either handhelds or benchtop instruments can be significant. While portables often approach the capabilities of benchtop instruments, handhelds tend to be self-contained and limited to a narrow range of analytes or outputs. Handhelds often provide “yes/no” or first-pass outputs sufficient for fieldwork.
Over the last decade markets for infrared and Raman spectroscopy have grown well beyond chemical analysis. This is in no small part attributable to portability advances in interferometry, a key FTIR operation. Conventional interferometers operate in just one geometric orientation, so their use in portable instruments is limited. A2 Technologies (Danbury, CT), which specializes in handheld FTIR, designed an interferometer that operates whether the instrument is pointing up, down, or sideways.
“A benchtop interferometer would not work if you were to stand it on its side,” notes Alan Rein, Ph.D., VP of business development at A2. Dr. Rein claims the instrument performs as capably as benchtop FTIR. “There’s no point in building a Tinkertoy that performs so poorly that it doesn’t tackle a range of applications.”
Where traditional IR requires some sort of sample preparation, handheld FTIR must operate at the point of use with no sample prep. This capability, made possible by bouncing the beam off the sample, is essential for nondestructive evaluation of valuable parts or structures. Limitations for handheld FTIR are the same as for IR spectroscopy in general, Rein explains. “IR is not the most sensitive analysis technique and doesn’t have the sensitivity of UV or MS. It comes down to physics.”
Depending on the user, handheld FTIR may provide as much information as benchtop instrumentation, Rein explains. But most field users are not trained spectroscopists or even chemists. “Some of our users can’t even spell spectroscopy, and they don’t need to.” For them, A2 offers instruments that provide “yes, no, maybe” readouts. “But spectroscopists can get full spectra if they need to.”
Output quality has traditionally been an issue for field instruments based on Raman, infrared, ultraviolet, and visible spectrometry. “All spectrometers collect spectra,” notes Richard Larsen, Ph.D., spectroscopy product manager at Jasco (Easton, MD). “The challenge is obtaining a quality spectrum under non-ideal conditions.” Spectral resolution among portables can vary by as much as sixteen- fold, Larsen notes; for example, 8 cm−1 vs. 0.5 cm−1 for FTIR, and 16 nm vs. 2 nm in UV/Vis. “The highs and lows represent the difference between research- and QA/QC-grade results.”
Sampling capability is another potential shortcoming, not just for spectrometers but also for all handhelds and portables. Many instruments are limited to one or two sampling modes, whereas general-purpose benchtop spectrometers accept samples in multiple formats.
The “desktop-laptop-handheld” is illustrated in how well field instruments stack up against benchtop systems. For example, Jasco’s portable UV/Vis instruments read 1.5 absorption units (AUs) vs. 6 AU for a bench spectrometer. Similarly, the company’s field Raman devices are limited to single-laser operation vs. eight lasers and multiple wavelengths for each benchtop version; and their IR instruments lack sample heating/cooling, advanced microscopy capabilities, and access to automation. On the other hand, some portable FTIR spectrometers, including one line sold by Jasco, can serve as fully functional lab instruments, according to Dr. Larsen.
Because of widely differing performance and prices, customers often have difficulty matching analytical needs with instruments, Larsen says. “They don’t always appreciate the distinctions and price differences between purpose-based instruments and full-function portables because they group all field instruments together. It is a product manager’s job to inform them so they get the capabilities they need without over- or underspending.”
Raman’s strength—identifying chemicals without direct contact or sample preparation—makes it a natural application for transportables. Thermo Fisher Scientific, through its recent acquisition of Ahura Scientific (Wilmington, MA) produces a line of rugged, handheld Raman spectrometers and a handheld FTIR device for identifying unknowns from a library of more than 10,000 explosives, toxic chemicals, chemical warfare agents, narcotics, and precursor compounds, even within mixtures. Instruments weigh between 0.8 kg and 1.8 kg. The target market is emergency first responders, homeland security, military, law enforcement, and forensics.
One of the Raman models, the FirstDefender RMX, operates in handheld mode or may be attached to a robot for operation in dangerous environments. Another Thermo Raman instrument, the TruScan, identifies raw materials used in pharmaceutical and consumer health industries through packaging, confirming their presence through a pass/ fail reading. In April 2010, the Nigerian National Agency for Food and Drug Administration and Control (NAFDAC) deployed TruScan for rapid identification of counterfeit and substandard drugs.
“Traditional laboratory instruments provide the user with just the raw spectra, while our instruments interpret the data and answer the users’ specific questions,” says Duane Sword, VP of marketing. In addition to yes/no outputs, FirstDefender and TruScan instruments can export full spectra for further analysis if desired.
From room- to briefcase-sized
Twenty years ago a mass spectrometer filled a room and required trained operators. Thanks to miniaturization in both electronics and the ion trap—a component inside the instrument that captures ionized molecules—the size and price tag of MS instrumentation has fallen steadily, to the point where mass detectors for LC and GC are common, and truly portable mass spectrometers are a reality. “The key,” observes Douglas Later, Ph.D., president of Torion (American Fork, UT), “is maintaining the same trapping capacity and sensitivity when the device is miniaturized.” A conventional ion trap measures approximately 1 cm across, while traps for portable or miniaturized instruments are about half that size. Torion has shrunk its trap to 2 mm across and combines the resulting hardware with a field-worthy GC into a suitcase-sized GC-MS system.
Torion employs a low thermal mass GC column system from RVM Scientific (since acquired by Agilent) that heats columns by up to 150 degrees per minute with high reproducibility. Rapid heating and cooling results in a run cycle of three to five minutes, according to Dr. Later.
Torion’s “GC-TMS” (its brand) can substitute for a benchtop system in a pinch, particularly for screening or determining dilution factors for full-scale GC-MS analysis. But the instrument does have limitations. It accepts samples through only solid phase extraction or small-volume direct injections of up to 0.2 microliter. Another shortcoming is limited access to spectrum libraries. The GC-TMS connects to a small, preconfigured ion trap library of compounds of interest. It can access much larger standard reference libraries, but these data are typically on quadrupole instruments, whose spectra differ significantly from those of ion trap instruments.
Evolutionary, not revolutionary
GE Power and Water Analytical Instruments’ (Boulder, CO) contribution to portable instrumentation involves total organic carbon (TOC), a measure of water quality. Utilities, environmental scientists, and users of ultrapure water are the principal markets. At five and twenty pounds in weight, GE’s two instruments both fall into the portable-but-not-quitehandheld category.
The smaller, lunchbox-sized unit, CheckPoint, can be moved to different locations or mounted permanently for continuous measurement, but it is not suitable for benchtop use. Stephen Poirier, growth and strategy leader at GE, describes the CheckPoint as a “sensor” rather than an instrument. “Its fundamental technology is not as robust or accurate as what you’d expect to find in a laboratory.” The larger instrument, Poirier says, is significantly more compact than a bench analyzer but has equivalent analytic capabilities. Both units connect to data systems through Ethernet, RS232, or USB cables.
Conventional TOC analyzers vaporize away water and combust organics in a high-temperature furnace, followed by infrared measurement of the carbon dioxide generated. In the GE devices, carbon materials are converted to carbon dioxide through low-wavelength ultraviolet light, then quantified by conductivity measurement.
Analysis methodology notwithstanding, Mr. Poirier describes the five-pound CheckPoint as an evolutionary rather than revolutionary design, where compromises were necessary due to the small footprint. “We considered the relevant applications and which technologies would be good enough to deliver a sensor in such a small footprint, rather than introducing a technologic breakthrough.”
The versatile approach
Forston Labs (Fort Collins, CO) has an interesting take on portable instrumentation. Its Lab Navigator handheld, modular field analyzer accepts up to five sensor plug-ins— four through proprietary ports and one via USB. Forston sells a variety of such sensors to measure, for example, flow, turbidity, calorimetry, carbon dioxide, dissolved oxygen, pH, conductivity, ammonium, calcium and global positioning. Perhaps the most intriguing “sensor” add-on is a UV/Vis/ fluorescence spectrophotometer.
By building versatility into its instruments, Forston occupies an interesting niche in the portable/handheld marketplace. Through its USB port, Lab Navigator accepts a wide range of third-party sensors. For example, there is a UV/Vis/ IR module from Ocean Optics (Dunedin, FL). “The Ocean Optics spectrometer scans from 200 to 1,500 nm and provides a wider range and better resolution than our sensor,” says Forston president Brian Williams.
The modular approach means that users can select only the capabilities they need. “Many sensor manufacturers produce products with standard zero to one-volt, zero to ten-volt, or four- to twenty-milliamp output,” Williams tells Lab Manager Magazine. “We have attachments that allow connecting up to four of those. And if we don’t have the right attachment, we can easily make one.”
Lab Navigator is somewhat unusual for a handheld in its “massive” data storage capabilities, according to Williams, and its ability to execute analysis on-instrument. Users may also upload data to a PC into standard formats through software Forston provides free with each instrument purchase.
Laboratory instrumentation has come a long way, from room- or benchtop-sized equipment to instruments with approximately the footprint of a vintage cell phone. There are two reasons to expect this trend to continue, both in terms of size reduction and analytic capability. The first is miniaturization and ongoing improvement at the bench scale, which is where innovation occurs first. The second is market demand for field-worthy instruments, which shows no sign of abating. For transportable instruments, this is a winning combination.