Is it the Motion or the Ocean?
James E. Picker, Ph.D.
H&P Mobile Geochemistry, Inc.
Carlsbad, CA
For over sixteen years, H&P Mobile Geochemistry, Inc. (and the partner firms that comprise H&P) have been in the business of providing field analytical services to a variety of environmental firms in the Southern California area. With as many as ten mobile laboratories and state of the art instrumentation, H&P Mobile Geochemistry, Inc. has virtually led the country in the sheer number of samples analyzed on client sites. From its beginnings analyzing soil samples for gasoline, diesel fuel and waste oil, H&P has expanded its analytical capabilities to include water, soil vapor and air matrices as well as field gas chromatography/mass spectrometry to its arsenal of weapons available to clients. H&P Mobile Geochemistry, Inc. is well known and respected by clients, regulators and even competitors.
One of our unique advantages is the ability to perform consistently day after day in a field setting. This ability to get the job done ensures that clients are always satisfied that their field work is performed with the highest quality available. H&P Mobile Geochemistry, Inc. uses the most modern and highest qualitynewest equipment available to the analytical chemist and does not hunt for bargain basement sales on used equipment. As such, clients are assured that the very latest instrumentation is used for their jobs.
Although we have been supplying quality services for a long time, it has come to our attention that a very small number of clients and members of the regulatory arena have questions concerning our time tested practice of performing our analyses from mobile vehicles and even while our laboratories are in motion. Notwithstanding the jokes concerning the rate of speed on the freeways of Los Angeles during rush hour, I will attempt to address this issue in purely scientific terms. To do so I would first like to anticipate some potential areas of objection and go on to explain why they should not be of concern. I will then give several examples of chemical analyses conducted in moving vehicles. Lastly I will point out the one and only consideration that needs to be answered.
GC/MS Vacuum Systems
The mass spectrometer is an instrument operated within a vacuum. In addition to a rough mechanical pump, which provides a first stage of vacuum (and is a fairly simple device), the system must have a pump to produce a high vacuum. These are currently provided by either turbomolecular pumps or diffusion pumps. Turbopumps operate with blades that spin at several thousand RPM and some are sensitive to shock, their bearings being the weak link. For that reason, all of H&P mobile labs are equipped with oil diffusion pumps. These have no moving parts and merely heat and condense oil to provide the vacuum. They are simple and reliable and have been functioning for us for years without any problems.
GC/MS Electronics
The first potential objection concerns the sheer mechanical stability of the analytical instruments. From the standpoint of a purely visceral reaction, no one likes to see their electronic gear bumped or shaken. It is clear that wires, solder points and other parts could be damaged by such treatment. It is certainly true that H&P Mobile Geochemistry, Inc. has had occasions when a part fails, likely owing to the constant vibrations that occur in the normal course of driving the labs. Instrument manufacturers routinely test all their instruments for shock and design them to withstand as much as they can. From a purely practical standpoint, the manufacturers have to ship the instruments. If they broke under the rigors of shipment they could not sell them in the first place. Besides, a complete failure of a part usually causes an error message in some part of the system or a catastrophic failure of the whole analytical system. In this rare instance, it is a question of not being able to do any work, not some slight effect on the data produced.
Merely having mechanical stability, though, is not enough. The instruments must have stability when operated. Again, given the history of mass spectrometers, the name alone conjures up images of gargantuan magnets operated in the basements of chemistry or physics departments. They were indeed placed in the basement to avoid the motion of the higher floors of a building. Also no one wanted to lift them to the upper levels of the building. Monster sector magnets aside, todays quadrupole analytical mass spectrometers contain neither permanent magnets nor, in some cases, metal machined rods but are built by applying a gold surface to a ceramic template. This allowed for the assembly line approach to the production of mass spectrometers, made them much more rugged and significantly brought down their price.
Since the heart of the mass spectrometer is now far more rugged, the only issue left must be the aversion to operate an electronic device on the move. If this is the objection, then I maintain that one should not step a foot inside ones automobile, not to mention onboard a commercial airliner. Certainly the level of mechanical jostling of the electronics on a jetliner must easily rival that of the mobile lab mass spectrometer. If a jet can find its way through the skies with the electronics subjected to takeoffs and landings, the same degree of reliability should be available in a ground based mobile lab. And if you think that the stress of commercial jet landings and takeoffs are of concern to electronics and vacuums, please do not attempt to launch scientific gear into the solar system. Do not even consider sending a Hewlett Packard (now Agilent) quadrupole mass spectrometer called Viking to Mars as it is bound to fail.
The proof of the viability of environmental GC/MS is already built into the methods which we perform. The same quality control procedures and specifications apply whether the analytical system is sitting on a concrete slab in Southern California or cruising down its freeway system at 65 mph. Initial Calibrations, daily calibrations, blank samples, spiked samples, etc. are required in both circumstances regardless of the relative motion of the laboratory container. If these are met, the system is under control and the data are valid.
