Product
Review
Taking the Show on the Road Portable GC and GC/MS
makes a gas chromatograph portaPortable instruments What ble? Contrary to popular belief, size alone is not the determining factor. In "portable" gas chromatographs can provide high-quality fact, weigh as much as 25 kg (that's more 50 pounds). Because the mass specdata and deserve than trometer adds bulk, portable GC/MS systems are larger than gas chromatomore respect than graphs, but the current generation is much smaller than the one that prethey get ceded it. Instead the characteristics that make these instruments portable are their independent power and carrier gas supplies. Richard Berkley of the U.S. Environmental Protection Agency has seen most of the commercially available portable gas chromatographs in operation. He compares the current state of portable gas chromatographs with the early days of the automobile—when vehicles had more widely varying individual styles. Right now, portable gas chromatographs are very different, with each one geared to a different type of appli-
cation. "These things are all very different. They do different things, and they do those different things very well." Portable gas chromatographs face a major hurdle in that people don't really know what the instruments can do for them, says Berkley. Therefore, they don't get the respect that he believes they deserve. Thomas Spittler, also of the U.S. EPA, says, "I think [portable gas chromatographs] are the most valuable tools we have in the environmental field bar none." And just what can field-based instruments do? First, they allow the collection and analysis of many more samples than would be possible if analyses were restricted to laboratory-based methods. Portable gas chromatographs make data available immediately. On-site chemical analysis provides project managers with the information to make immediate decisions as to the location for collecting the next sample and the type of analysis to be performed. This dynamic approach is de-
Analytical Chemistry News & Features, March 1, 1997 195 A
Product
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Table 1 . Summary of representative portable gas chromatographs. -
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Model 4100 Vapor Detector and Analyzer Electronic Sensor Technology 2301 Townsgate Rd. Westlake Village, CA 91361 805-495-9388 INA
311D GC
MSI-301
Ekho
P200 and P200H
HNU Systems 160CharlemontSt. Newton, MA 02161 617-964-6690
MSA Baseline Industries P.O. Box 649 Lyons, CO 80540 303-823-6661
MTI Analytical Instruments 41762 Christy St. Fremont, CA 94538 510-490-0900
INA
Microsensor Systems 62 Corporate Ct. Bowling Green, KY 42103 502-745-0099 $9,500
INA
INA
35.6 x 50.8 x 25.4
38.1 x 56.4x24.6
8.9 x 36.8 x 33
45x33x13.6
Weight (kg) Power supply
15.9 120 VAC with 12-VCAR inverter
25 110, 115, or 230 VAC
5.4 120 VAC or 12 VDC; optional battery pack
13 Rechargeable lead acid battery, 4- to 8-h discharge
Sample introduction
Cryo-focus chamber
Internal sampling pump
Heated injection port, sorbent cartridge
Carrier gas
He
Internal sampling pump, concentrator with 10port valve, and heated injection port Application dependent
15x36x36(200) 1 5 x 3 6 x 4 1 (200H) 10.4 (200); 13.2 (200H) 12-V rechargeable lead acid battery; 6- to 8-h (200) or 4-h (200H) discharge Silicon micromachined injector, internal sampling pump
Ambient air scrubbed with activated carbon
Rechargeable Ar cylinder
Temperature control
Programmable ramping to 200° C
Columns
Capillary
Isothermal to 200 °C Isothermal operation and temperature5-40 °C programmable oven with ramp rates 1-15 °C/min Capillary or packed Capillary or packed
Detectors
Surface acoustic wave resonator
PID, ECD, far UV, FID, FPD, orTCD
Chemically coated solid- ECD state microsensor, surface acoustic wave resonator
TCD
Data system
Pentium laptop configured to user's needs with optional modem capabilities for remote-site monitoring
Internal microprocessor, keypad, and LCD display, or PC with Peakworks software with analytical and search modes, can be operated remotely, with or without a PC
Results displayed on front-panel LCD and stored in onboard computer memory, stored data can be downloaded to PC, can be controlled remotely with PC and modem
Sorbat software stores and manipulates chromatograms, controls GC parameters, and stores methods; requires 386 or higher PC, 2-MB RAM, and 80-MB hard drive
EZChrom 200 software package for data collection, analysis, storage, and instrument control
Options
INA
INA
INA
INA
INA
Reader service #
401
402
403
404
405
Model Company
Price Size H x W x D (cm)
Programmable ramping to175°C
Multicapillary
Internal gas supply via refillable tank; external connection to He, H2, N2, or Ar Isothermal operation 30-180 °C (200) and 50-180 °C(200H) INA
INA, information not available
scribed in the May 1,1996, Federal Register and can indicate whether or not considerable sample degradation occurred be(61FR19431-19463) for the cleanup of tween collection and analysis. Berkley Superfund, RCRA, and Brownfield sites, says that he doesn't see portable instrusays Albert Robbat, director of the Center for Field Analytical Studies and Technology ments completely replacing lab-based methods, but he does predict that they at Tufts University. SpMer comments that will become a more integral part of the such flexibility in sampling strategies can field sampling and site-characterization result in cost savings by eliminating the process. Although portable instruments need for multiple sampling trips. are most widely used in environmental In addition, field instruments can proapplications, they are finding a place in a vide data to validate laboratory analyses 196 A
Analytical Chemistry News s Features, March 1, 1997
variety of other fields, including forensics, industrial hygiene, chemical warfareagent detection, and on-line process monitoring. Spittler enumerates the many analyses for which portable gas chromatographs can be used. Portable instruments can measure volatile organic compounds (VOCs) in water by headspace analysis to the sub-ppb level. If soil samples are properly prepared, portable gas chromato-
FM-2000
Snapshot
Voyager
Scentoscreen
Scentograph Plus II
0.1. Analytical CMS Field Products Group 200 Chase Park S., Ste. 100 Birmingham, AL 35244 205-733-6900
PE Photovac 330 Cochrane Dr. Markham, ON L3R 8E5 Canada 905-477-8088
Sentex Systems 553 Broad Ave. Ridgefield, NJ 07657 201-945-3694
Sentex Systems 553 Broad Ave. Ridgefield, NJ 07657 201-945-3694
INA
-$12,500
PE Photovac 330 Cochrane Dr. Markham, ON L3R 8E5 Canada 905-477-8088 ~$16,000-$18,900
~$14,000-$18,000
$21,000-$24,000
30 x 30 x 25
23x12.7x35.6
15x27x39
16x34x43
15.2x52.1 X50.8
8.1 110 VAC
4.4 Snap-on, rechargeable lead acid battery, 4- to 6-h discharge
6.8 Rechargeable NiCd battery, 6- to 9-h discharge
14 Internal power 12VDC, 110/220 VAC
21.8 Internal power 12 VDC (9 h), external power 110 VAC
Sorbent preconcentration or sample loop
Sample inlet port with particulate filter
Syringe or internal sampleloop injection
Internal preconcentrator, sample loop, or injection port
Internal preconcentrator, sample loop, or heated injection port
N2 or He
CO2 or N 2 in disposable cylinders
Ultra-zero air or N 2
Ar or He
Ar or He
INA
Isothermal operation 45 °C
Isothermal operation 55-80 °C
Isothermal, programmable to180°C
Isothermal or programmable to 180 °C
Capillary
Interchangeable factoryprogrammed application modules with wide-bore capillary columns
Packed columns to 12 ft, 30-m stainless steel capillary
Packed columns to 12 ft, capillary columns to 105 m, dual-column capability
FID;PID;FPD;XSD;PFPD; or tandem FID/FPD, PID/FID, or PID/XSD
PID
Fixed three-column set with automatic precolumn backflushing, wide-bore capillaries or micro-packed PIDorECD
Micro-argon ionization, ECD, PID, orTCD
Micro-argon ionization, argon ionization, ECD, PID, orTCD
MINI-LINK software for multipoint calibration, methods storage, chromatogram display and storage, and methods library; MININET data communications network for remote data reporting from up to 50 monitoring systems
Compound library, analyzer setup, and analytical method software included in application modules; data can be downloaded to PCcompatible computer via RS-232 serial port
On-board assay (library and method), on-board data logger, Site Chart software (Windows) for instrument operation and data handling
Compound library, automatic peak identification and quantification, programmable run via detachable laptop PC, 700-MB (or larger) hard drive
Compound library, automatic peak integration, identification, and quantification; programmable run via detachable laptop PC with 700-MB (or larger) hard drive
Stack sampling accessory, Calibration system, fieldheated sample lines, dilution replaceable carrier gas system, heated injection port cartridges, high-impact carrying case
Field application kit, extended-reach sample probe
INA
Purge-and-trap unit, heated injection port, stack gas sampler
406
408
409
410
407
graphs can be used for determining VOCs in soil by converting the sample to an aqueous slurry or methanol solution, depending on the concentration expected. They can perform direct ambient air analysis for aromatic hydrocarbons and chlorinated alkenes. "The importance of these capabilities is that the majority of sites involve hazardous volatile organic compounds getting into the soil and groundwater," Spittler says.
Table 1 lists several representative portable gas chromatographs, which range from the hand-held Snapshot by PE Photovac to several competitive instruments whose performance rivals that of the traditional benchtop gas chromatograph; Table 2 enumerates the features of three portable GC/MS systems. The instruments are equipped with microprocessors that allow them to be operated independently, but they can also be interfaced
with computers for more sophisticated control and data manipulation. The instruments The various portable gas chromatographs differ from one another most prominently in their detectors. Generally, any detector that is available for a benchtop instrument is also available for a portable instrument, although not necessarilyfroma single company. Because most companies offer
Analytical Chemistry News & Features, March 1, 1997 197 A
Product
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T a b l e 2. R e p r e s e n t a t i v e p o r t a b l e GC/MS s y s t e m s
Model Company
URL Price Size H x W x D (cm) Weight (kg) Power
Sample inletting
EM 640 and EM 640 S Bruker Instruments 19 Fortune Dr., Manning Park Billerica, MA 01821 508-667-9580 www.bruker.com
Hapsite Inficon Two Technology Place East Syracuse, NY 13057 800-223-0633 www.inficon.com
INA
INA
55 x 45 x 35 60 24-V DC, 220/110-V external power supply
18x43x46 16, including battery 24VDC
Split/splitless injector, thermal desorber, automatic air and water samplers, real-time sampler
INA
Three-stage program (max. 300 °C) or isothermal N 2 or air (640) He or N 2 (640 S) Quartz capillary all i.d. to 25 m long (640) Quartz capillary 0.2-mm i.d. to 30-m long (640 S)
INA
SpectraTrak 572 Viking Instrument 3800 Concorde Parkway Chantilly, VA 22021 703-968-0101
[email protected] ~ $89,000 46 x 61 x 29 34 110 VAC (switch selective to 220 VAC), operates reliably with portable generator Direct injection with split/splitless injector, preconcentration/thermal desorption with built-in sampling pump, direct real-time MS (bypassing GC) via membrane interface
Gas chromatograph Temperature control Carrier gas Columns
Mass spectrometer Mass range Maximum scan rate Mass stability Ionization Detector
N2
Programmable to 325 °C or isothermal He; N 2 or H2 optional
0.32-mm i.d. capillary; 30 m long
Capillary to 0.32-mm i.d.; 60 m long
1-640 amu 2000 amu/s Weeks Electron impact Digital and analog channeltrons
1-300 amu 1000 amu/s INA 70-eV electron impact INA
Vacuum system
Ion getter pump
Non-evaporable getter pump
Sensitivity
1 ng/s in source; S/N 10:1
INA
Dynamic range
109
INA
Data system
Pentium 2-GB hard drive, 32-MB RAM; OS Warp Connect, Bruker software with special peak-recognition routine
INA
Options
Connectable to laboratory gas chromatograph
INA
Special features
Usable while underway in ship or vehicle (640); membrane inlet system (640); direct inlet and built-in pumping systems (640 S); easily exchangeable peripherals, including gas chromatograph oven (both)
Analytical and survey modes of operation, built-in NIST library to tentatively identify non-target compounds, built to operate reliably under adverse conditions, can be washed down for decontamination
Reader service #
411
412
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1.6-700.0 amu 1800 amu/s ±0.15 amu over 12 h 70-eV electron impact Continuous dynode electron multiplier Turbomolecular with diaphragm roughing pump Full-scan mode: 100 pg hexachlorobenzene (S/N > 10) Selected ion monitoring: 1 pg hexachlorobenzene (S/N >10) 10 6 ; linear over 4 orders of __jriajjnitude Pentium microcomputer, 120 MHz, 16-MB RAM, 750-MB hard drive; Viking SpectraScan Operating System integrated with HewlettPackard ChemStation running under Windows 3.11, NIST library standard, additional special libraries available Purge-and-trap concentrators, headspace sampler, autosamplers, automated remote air sampling, analysis module Analytical versatility to handle a wide range of compounds, robust construction, easy transport, operable during transport, ready to analyze within minutes of arrival at site, remote operation via modem, interfacing and control of sampling devices
413
only a few detectors (Sentex, CMS, and HNU are the exceptions) and those detectors are selective for different classes of compounds, Berkley believes that it is vitally important to keep firmly in mind the type of analysis that the instrument will be performing. Photoionization detectors, electron capture detectors, and solidstate detectOfS g|*g evenly distributed among the instruments in Table 1. The Ekho from MSA Baseline Industries has only an electron capture detector, but according to Berkley, it is one of the most robust electron capture detectors that he has ever seen. When testing the Ekho in the laboratory, he flooded the detector with chlorinated solvents, and the instrument returned to a stable baseline in only a short time. The Model 4100 from Electronic Sensor Technology is equipped with a surface acoustic wave (SAW) piezoelectric detector, which is fully solid state. The dynamic range of the SAW extends over five orders of magnitude. According to George Pappas of Electronic Sensor Technology, the Model 4100 is capable of obtaining 10-s chromatograms in < 1-min intervals. He says that the user more often determines the limit of rapid analysis. The mass spectrometer in a GC/MS system could be viewed as just another detector for the gas chromatograph. The GC/MS systems are larger than the gas chromatographs and might better be described as transportable. However, the GC/MS systems do meet the requirement of being self-contained systems. Stephan DeLuca of Inficon stresses, however, that the Hapsite instrument, at 16 kg including the battery, is truly portable. Jeff Christenson of Viking Instruments says, "Calling a mass spectrometer just another detector is like calling a Ferrari just another automobile. Whereas a portable gas chromatograph with a conventional detector will only tell you that something came out at some time,he maas spectrometer rerves sa a highly intelligent and sensitive detector providing a wealth of information to positively identify and dqantifv each hompound and as a universal detector that sensitivelv ' responds to virtually all tvnes of oreanic m n l o r i i l e c Fur+Vior ncinrr t h e m a o c c r w >
trnmeter as the CC detector solves nroblems that a standard tras chromatooranh 4 i *
v
u
i
it:
detector can t, such as coeluting peaks, retenbontimeshifts, unexpected unknowns, and matrix interferences. Thus, a portable X.
T. /
4
-
4
.
gas chromatograpn/mass spectrometer will give you the full story right at the site, maintaining sample integrity, without the
need for laboratory confirmatory analysis." Robbat has developed a software program for GC/MS analysis (portable or laboratory), called Ion Fingerprint Detection, that he says will allow all lhe pesticides, PCBs, and PAHs to be analyzed in a single 7-min run. It has been licensed to Ion Signature Technology and will first be avaiiable for use with Hewlett Packard ChemStation data files, which will make it directly applicable to the Viking instrument Robbat has used the software to deconvolute the mass spectra of coeluting compounds separated with short columns. He believes that the program will increase the use of field instruments because one of theirffOcilsis to be cible to run the necessarv samples
PE Photovac's Snapshot is the only truly "hand-held" instrument in Table 1. The column is in an "application module", which is the size of a deck of cards, that also contains the flow-control hardware and the software for a specific set of compounds. To change sets of compounds, one module must be removed and replaced with another. Most of the portable gas chromatographs are powered by batteries (NiCd or lead acid) or generators (110 VAC). The batteries last 4-9 h during discharge and require 6-8 h for recharging. Robbat feels that batteries and generators are somewhat unstable and make the oven temperature more difficult to control precisely. Berkley, on the other hand, says that flucin ?m tuations in ambient conditions are far short a time a,s possible more likely to wreak havoc on an analysis. Portable gas chromatographs generally The electronics and ovens are temperaaccept either capillary or packed columns, ture sensitive, and sudden changes in amalthough several (which are noted in Table bient conditions C3.I1 CetUS6 fluctuations. 1) will accept both. The ovenn tend to ob For this he recommends using the miniaturized, so the columns cannot be as instruments in a protected area where they won't be affected by direct sunlight or temperature changes "Unless you use them in a sheltered environment they'll bite you" he says Berkley has complained that manufacturers fail to use enough insulation but he also savs that they are no worse than benchtoo instruments in that respect Portable gas chromatographs usually have one of two carrier gas setups, an internal gas canister or a means of scrubbing ambient air. However, many of the instruments can also be plumbed to an external carrier gas supply. When an internal canister is used, the choices of carrier gas are generally the same as those for laboratory systems (hydrogen, helium, nitrogen, and long as those used in benchtop instruargon). The actual choice depends on the ments, although the Sentex and HNU inapplication and the type of detector used. struments do accept columns as long as 125 m. The GC311 ffom HNU has an oven Manufacturers recommend that only one large enough to accommodate two columns type of carrier gas be used in a given inter(either packed or capillary) from any com- nal croc mercial manufacturer. However, shorter cylinder; that is, an empty cylinder column lengths need not be considered a should be refilled with the same gas. disadvantage; although they often mean When using an electron capture detecless chromatographic resolution, they also tor, nitrogen or helium should be used as provide a faster analysis time. the carrier gas. Stephen Kane of PE PhoThe Ekho uses a short column (150tovac says that when using a photoioniza1000 mm) consisting of more than a thou- tion detector, an advantage of air as the sand 40-um diameter capillaries fused to- carrier gas is that there is no baseline disgether in a glass block column; the cross ruption when an air sample is injected. section of the assembly looks like a honRobbat says, "You're trying to determine eycomb. According to Hank Braly of what's in the air. At temperature condiMSA the short column length coupled tions [suitable for volatiles analysis] the with the high sample capacity allows a column will be relatively stable for long much faster analysis than ordinary capilperiods of time, even with air as the carlary or packed columns. rier gas Most people believe that the columns fall apart when you use air as the
Portable instruments can be used in forensics, ,ndustrial hygiene, and process monitoring applications.
Analytical Chemistry News & Features, March 1, 1997 199 A
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carrier gas, but that's not true." However, Jack Driscoll of HNU says that using air as a carrier gas can be a problem with carbowax columns, which can be affected by water in the air. Here to stay and growing "Field analytics is here and should be growing," Robbat says. What needs to happen to ensure such growth is for peo ple to use the right instrument for their application and to understand their objective, he says. "If you know you're only looking for two chlorinated solvents, why not just take a good gas chromatograph with an electron capture detector into the field?" Robbat believes that portable gas chromatographs are best suited for screening or semiquantitative work. However, he says that if the proper instrument is chosen for a specific application, no more than 5-7% of the samples should need laboratory analysis and that in a "perfect world" no samples would need to be sent for confirmation. "If you have a IT13SS spectrometer or two detectors (such as a flame ionization detector and an electron capture detector) that are being used as a complementary pair you shouldn't have to send any sample to the lab for confirmation But even if you do send samples to the laboratory you should send only those samples for which you've gotten a hit rather than arbitrarily selecting every 10th or 20th sample for confirmation " Spittler sounds a similar th i g that it ma be advisable to
graphs can achieve excellent reproducibility of retention times and integration values, which allows them to provide results comparable to those of laboratory gas chromatographs. With the use of the microargon ionization detector or other available detectors, a wide range of compounds, including chlorinated alkenes and alkanes, can be detected at sub-ppb levels. A main point to consider, however is not the quality of the gas chromatograph but the quality of the sample. Samples, especially water samples may lose a considerable amount of their constituents by the time they reach the laboratory Even if we accept that portable gas chromatographs are less accurate than laboratory gas chromatographs the choice is whether to obtain less accurate results from an accurate sample that contains all the constituents at their inal concentrations or to obtain accurate re sults from a sample that may have lost a considerable t of its constituents, and in some cases, all of them. Spittler says that field-based measurements provide more accurate data than laboratory measurements. When samples are analyzed in the field, ,here's sess need to store them and the loss of volatile constituents is prevented. "Field analysis eliminates major sources of error and eliminates huge costs," Spittler says. The most important consideration when purchasing an instrument is the intended use. "There are a lot of portable chromatographs on the market that are targeted to certain jobs " says John Schneider of Argonne National Laboratory "They tend to be restricted in what they can do but can do the thing that they're targeted to do very well If vou want to flook for more than one tvne of analvte] it becomes more difficult to use a portahle'instrument The ones that have more flexibility are a little harder to come h " Robbat agrees: "Many instruments are only geared to a particular analysis. It's up to the end user of the instrument and, ultimately, the end user of the data to know what the instrument is best used for and whether or not it best meets the data qualCelia Henry ity objective."
Portable instruments save time and money through judicious selection ofsamples for lab confirmation.
J
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1
A
t-V.
1 -U
4-
send some samples to the laboratory in J
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