When we think about a mobile version of an environmental analytical lab, we might imagine a stripped down operation designed to provide minimal or rudimentary services. If so, H&P, a San Diego-based fleet of mobile environmental laboratories, belies the image. To be sure, H&P must accomplish its tasks in much more limited space than a conventional fixed-base lab, but thanks to the miniaturization in instrumentation and methods achieved in recent years, the concept of a fully functional mobile environmental lab is a working reality.
Founded by the author, Ms. Rebecca Johnson and Dr. Blayne Hartman, analytical chemists and geologists with significant environmental lab analysis experience, H&P got its start during the early years of the U.S. Underground Storage Tank Program. This program was initiated by the U.S. Environmental Protection Agency and adopted in one form or another by the individual states after it became known that many underground storage tanks were leaking hazardous materials such as petroleum or other chemical products into the environment. As a result, owners of gas stations, tank farms and related installations were under mandate to replace the leaking tanks and decontaminate the environment polluted by the leakage.
Determining the extent of the contamination at storage tank sites pursuant to remediation required the sampling and analysis of soils to establish a contamination boundary. This approach requires an ongoing process of sampling and analysis, a technique termed "dig and chase." Depending upon a fixed-base environmental lab remote from the site to perform this type of analysis would have caused inordinate and expensive delays between successive rounds of sampling. With a mobile environmental lab on site, synchronized sampling and analysis could be carried out expeditiously, enabling the concentration gradient and boundary of contamination across the site to be rapidly determined. Thus, a project that might have taken weeks to months using a fixed-base facility could be completed in hours to days by a mobile lab operating on site. H&P Laboratories was created to fill this type of need.
It soon became apparent that time-critical analysis was in demand. Soon H&P's tasks were expanding to all phases of environmental restoration, from simple on-site remediation to initial site assessment through analytical support of monitoring wells used in ongoing contamination assessment. The variety of sites that H&Ps environmental laboratories supported included gasoline stations, bus stations, airports and military installations, all of which handle significant quantities of materials such as gasoline, diesel fuel, jet fuel, heating fuel, and chlorinated solvents for cleaning engine parts. Other sites with comparable ground contamination from stored hazardous materials included dry cleaners and tank farms. In all of these applications, on site analysis by the mobile lab provided an efficient means for assessing site contamination pursuant to subsequent environmental cleanup. In commercial real estate transactions, for example, a question of possible contamination could be settled by sending out a Mobile lab to determine if contamination was present and the nature and extent of it.
Over the years, H&P has streamlined its methods, focusing on a need for speed. Today, an analysis that might require a one-week turnaround for a fixed-base lab can be handled by an on-site Mobile environmental lab in 20 minutes. This high-throughput capability makes H&P cost competitive when quick turnaround is required. Typically, analysis fees plus additional rush charges levied by fixed-base laboratories often exceed the cost of using the mobile laboratories faster analysis turnaround capability.
Instrumentation in a modern fixed-base lab and H&P's mobile environmental lab fleet are virtually identical. However, space constraints, the need for a road worthy installation, and intermittent connection to the power grid, demands the exercise of significant creativity in putting together a mobile configuration that is flexible enough to execute a broad variety of analytical tasks with state-of-the-art performance.
Currently, H&P is meeting this challenge with five (ten as of 5/06 note added in print) mobile environmental laboratories and one fixed-base installation. Four of the laboratories are installed in vans (Fig. 1) and the fifth, the most recent addition, is housed in a 16-foot "fifth wheel" trailer (Fig. 2). Each mobile lab is built to H&P's custom specifications which includes power supplies--A.C generators with backup, environmental controls, lighting, refrigerators, sinks with running water and lab benches. Instruments are secured to the counter top with an "industrial-strength" type of VelcroTM called Dual LockTM (3M Corp., St. Paul, Minnesota). A special harness was custom designed for the autosampler towers to prevent rocking while in transit. As a concession to road shock, the mass spectrometers were ordered with diffusion pumps instead of less rugged turbopumps.
Solvents, which might be thought a potential hazard in a mobile lab installation, are not at all problematic. Modern analytical protocols minimize solvent usage, so each laboratory carries no more than 500 ml. of methanol for volatiles analysis. Other extractions are carried out in a fume hood with non-flammable methylene chloride. To guard against breakage, solvents are racked in their Styrofoam shipping packages and all waste is retained for proper disposal.
.Each laboratory is operated by a degreed chemist. Although many of the analyses performed are routine, we feel that the need to adapt methods to the non-routine circumstances of each assignment requires a level of independent scientific judgement that is beyond the skills and training of the average laboratory technician.
Typically, the mobile environmental lab operators begin their workday by starting up the generators, loading daily calibration samples and running both calibration checks and blanks en route to the analysis site. Analysis of samples, spikes and duplicates continue on the return trip. The biggest challenge in choosing to perform analyses in transit was overcoming the prior belief that it could not be done. Now, running analyses in a vehicle moving at 50-60 mph is considered routine.
For the most part, standard environmental analytical methods are not affected by the vehicle's movement, although certain adjustments are made to compensate for the absence of a standard power supply. For one, the mobile labs are equipped with a sophisticated electrical system to ensure uninterrupted vacuum and heating for instruments and detectors. Each mobile environmental lab is equipped with an inverter which seamlessly switches to battery power as soon as the vehicle is unplugged from the power grid. When the vehicles start up, the supply of electricity is shifted from battery to generator without interruption. In addition to power management, the inverter is designed to protect the instruments from power surges. As an additional failsafe, battery backup keeps the MS under vacuum in the event that both line and standby generators go down.
Analytical data processing and data management is handled by onboard computers using report templates. Once the analyses are complete, preliminary reports are generated for clients on site. On return to base, the data is transferred to the system computer and a final report is generated.
H&P began its operations analyzing sites contaminated by fuels such as gasoline or diesel. This type of analysis can be performed by a standalone GC with flame ionization detector. However, over time, fuel analyses have become more sophisticated with increasingly stringent requirements for component identification. Under the current regulatory regime, one must determine both the total gasoline or diesel content as well as the individual concentrations of benzene, toluene, ethyl benzene, and xylenes (BTEX). Originally, this analysis (EPA Method 8020) was performed by GC with photoionization detector (PID). To conform completely to the method, confirmation of the GC analysis requires running a second or dual-column determination. With GC/MS, the MS spectra provide absolute confirmation of the chromatogram assignments and no second analysis is required. Similar benefits are achieved with the GC/MS analysis of chlorinated solvents.
Starting in the mid 1980s, in an effort to reduce the smog generated from motor vehicle exhaust, oil companies began to reformulate gasoline with methyl t-butyl ether (MTBE). Unfortunately, it was soon determined that this additive was a potential carcinogen and that it was leaking from storage tanks and contaminating groundwater. GC/MS analysis of MTBE is simpler than analysis by GC alone. In the later case, there is potential interference from co-eluting hydrocarbons. With GC/MS, MTBE can be easily identified by an ion of characteristic mass. In addition to MTBE, other fuel oxygenates, such as t-butyl alcohol--a breakdown product of MTBE--and MTBE substitutes such as diisopropyl ether (DIPE) and ethyl t-butyl ether (ETBE), can be quickly and accurately determined by GC/MS.
Diesel fuel is a much heavier refinery fraction than gasoline and can contain a range of polynuclear aromatic hydrocarbons (PNAs). Many of these substances are known carcinogens and therefore it is important to determine the extent of their concentration in the event of site contamination. PNAs are classified as semivolatiles and may be analyzed by EPA Method 8270C--a GC/MS method*. This is also the case for PCBs. However the MS, although a more specific detector, is not quite as sensitive as the electron capture or Hall detectors generally employed for chlorinated hydrocarbons.
As with gasoline, a diesel analysis with PNA quantitation can be achieved by utilizing GC/MS in place of GC. USEPA GC-MS Methods 8260 (volatiles) and 8270 (semivolatiles) have become the defacto test for environmental contamination because they incorporate a large target list and provide MS conformation of GC in the same run. Currently, H&P is analyzing the full list of semivolatiles.
Because of the advantages inherent in GC/MS analysis of PCBs, H&P has modified Method 8270C. Addition of a large volume injector improves sensitivity by concentrating the sample and thereby delivering a higher concentration of analyte to the head of the column. The large volume injector is also employed in PNA analysis because of its ability to eliminate both time-consuming concentration of large volumes of solvent. Method 8270C calls for the extraction of a 30-gram soil sample with several hundred milliliters of solvent followed by evaporation to a volume of 1 milliliter. This operation takes at least 4-5 hours, and for processing multiple samples, requires a bank of large extractors and concentrators--equipment which can't easily be accommodated in the limited space of a mobile lab. By contrast, a method which employs a large volume injector requires extraction of a much smaller 10-gram sample with only 10 milliliters of solvent. Since the sample is injected directly onto the column, there's no need for a concentration stage.
The improved sensitivity and rapid throughput gained with the large volume injector is such that it is increasingly being applied to the analysis of other semivolatiles. Currently, H&P is using this technique to determine both N-nitrosodimethylamine and 1,4-dioxane. Dioxane is classed as a volatile, but its high water solubility makes it very difficult to analyze by purge and trap. Accordingly, we treat it as a semivolatile and extract it with dichloromethane. The use of MS affords some elegant modifications, which cannot be used in a GC analysis. For example, the analysis of dioxane by GC/MS makes it possible to use a technique known as isotope dilution. In this application, a known amount of 1,4-dioxane-d8, referred to as labeled standard, is added to the sample prior to preparation. The virtual identity in chemical properties of the hydrogen- and deuterium-substituted analogs guarantees that there will be no unequal partitioning under sample preparation and chromatographic operations, thus ensuring an accurate assessment of the dioxane.
H&P's first mobile environmental lab was installed in 1990, in a Dodge Van, and was built for less than $55,000 complete with two small GCs. By contrast, the most recent installation, a "fifth wheel" trailer with truck equipped with two GC/MS and GC cost more than $250,000. Overall, the cost of vehicle purchase, modification for lab installation and running a mobile lab is roughly comparable to that of a fixed-base.
H&P's most recent acquisition is a 16' "fifth wheel trailer. The interior space is divided into a sample preparation area (1/3) which contains a regulation size lab hood, a sink, storage for gas cylinders, gas regulators, and sample preparation apparatus which includes an ultrasonic horn for sonnicating soils. The remaining 2/3 of the interior space houses the analytical instrumentation which comprises two Agilent Technology 6890/5973 GC/MS systems (Agilent Technologies, Inc., Palo Alto, CA) . One system is configured with a purge and trap "front end" for volatiles analysis and the other configuration is dedicated for the analysis of semivolatiles and equipped with an automatic liquid sampler.
Jim Picker earned a BS in Chemistry at Fordham University and a Ph.D. at the University of Colorado. He has considerable experience in environmental and pesticide analysis at EPA contract laboratories. Prior to forming H&P in 1990, Dr. Picker was a co-founder of Pacific Analytical, in Carlsbad, California.