Product
Review
ILLUMINATING Near-IR Near-IR spectroscopy is fast becoming a useful analytical tool at industrial process lines, in biological and polymer research laboratories, in the field as a portable method, and for quality control of raw materials. Its speed, noninvasive nature, and minimal sample preparation requirements make it attractive for a variety of sample types including liquids, slurries, coatings, powders, and solids. The ability of near-IR wavelengths to penetrate into and sometimes through a sample has led to some astonishing experiments: In the past five years, near-IR spectroscopy has been used to determine pH in the caustic brines of hazardous waste tanks, and prototype near-IR "cuffs" that fit over a person's finger and measure the light transmitted through the fingertip have been proposed for noninvasive determination of blood glucose. The enormous progress in chemometrics and computing power that has been achieved in the past decade makes both exotic and routine applications possible. Near-IR spectrometers range from simplified process instruments that monitor only a few wavelengths characteristic of a single analyte to full-fledged research in-
Advances in component design and calibration softwarefitnear-IR for both research and routine use
ysis. Table 1 presents characteristics and components for a representative selection of near-IR spectrometers. For more information on individual products, send an e-mail message with one of the keywords listed at the bottom of the table in the subject line to our reflector service at
[email protected]. For a more comprehensive list and more in-depth discussion of near-IR system components in general, see W. Fred McClure's Report on near-IR spectroscopy in the Jan. 1,1994, issue (Anal. Chem. 1994, 66,43A-53A).
struments that acquire spectra in the entire near-IR region (780-2526 nm) as well as mid-IR or UV-vis wavelengths. Some instruments can even perform near-IR imaging. We asked Mark A. Arnold of the University of Iowa, Lois Weyer of Hercules, and Patrick Treado of the University of Pittsburgh for their views on trends in near-IR instrumentation and applications and their advice for potential buyers. In the United States alone, there are well over 20 manufacturers of complete near-IR spectrometers and many more "third-party" vendors of components for sampling or detection and software packages for data anal-
Source optics Source optics differentiate commercial near-IR spectrometers into four major types: grating monochromator, Fourier transform (FT), acoustooptic tunable filter (AOTF), and light-emitting diode (LED). Perhaps because process-monitoring applications, whether on-line or at-line, make up one of the largest segments of the near-IR market, each of these spectrometer types is being pursued for adaptation to dedicated routine as well as research use. Each method has its strengths and tradeoffs with the others, and no one type is
Analytical Chemistry, December 1, 1995 735 A
Product
Review
Table 1 . Summary of representative products Product Company
SpectroChem 100 AnalytiChem P.O. Box 677 Rockville, MD 20848 301-924-3025
Genesis ATI Mattson 1001 Fourier Dr. Madison, Wl 53717 800-423-6641
Infra Prover Bran+Luebbe 1025 Busch Pkwy. Buffalo Grove, IL 60089 708-520-0700
Luminar 2000 Brimrose 5020 Campbell Blvd. Baltimore, MD 21236 410-931-7201
Price Type
$35,000 (complete system) Diffraction grating
$28,500 FT
ΙΝΑ FT
ΙΝΑ AOTF
Techniques
Transmission, reflectance
Transmission, reflectance
Optics
Diffraction grating with postdispersive detection using fiber-optic bundles to remote probes and cells
Fully sealed and desiccated Michelson corner-cube interferometer with internal HeNe wavelength refer ence; halogen source with CaF2 beamsplitter
Reflectance, transmission, transflectance Polarization interferometer
Reflectance, transmission, transflectance AOTF with software-selec table wavelength incre ments of 0.3-20 nm; dou ble-beam design with poly styrene reference
Detectors
I n As
Peltier-cooled InAs; LNgcooled InSb or InGaAs
Temperature-stabilized PbS
1 sample and 1 reference; Si (650-1050 nm);TEcooled InGaAs detectors for 900-1600 nm, 10001850 nm, or 1200-2200 nm
5 scans/s
1.1 s/scan
Up to 4000 discrete wavelengths/s in random access
1000-5000 nmwith InSb; 1000-3800 nm with InAs; 800-1700 nm with InGaAs 0.1 nmat 1000 nm
1000-2500 nm; 10002200 nm with fiber optics
650-1050 nm;900-1600 nm; 1000-1850 nm; 1200-2200 nm 1-3 nm; 2-6 nm; 3-7 nm; 5-10 nm, respectively
Yes
Yes
Yes
First and second derivatives
PLS, PCR
PLS, PCR, discriminate analysis
PLS, PCR, cluster analysis
PLS, PCA, PCR, KNN
No Yes
Yes ΙΝΑ
386 DX or higher PC; RS-232 communications; full data acquisitions and manipulation
386 PC standard, 486 PC optional; Ethernet communi cation, data acquisition and processing software; selfdiagnostics; process control language
Validation kit; NIST stan dards; bar code readers, remote switching probe for liquids; AOTF, filter, and grating systems also avail able
Fiber-optic probes, 16-channel multiplexer
403 ac NIR624
404 ac NIR625
Performance Spectral acquisition time 2 s
Spectral range
1000-2500 nm
Resolution
1 nm at 1000 nm; 2 nm at 2000 nm
Statistical functions Derivatives/data pretreatment Nonlinear regressions (PLS, PCR, etc.) Multiple linear regression Statistical fit diagnostics (overfitting) Data system
Yes Yes
Yes
IBM-compatible 386 or higher PC running Windows
386 or higher PC running Windows 3.1 or higher; RS232C communications; full data acquisition, manipula tion, reporting, and pro grammable control
Special features
Available as lab, process, or portable system
Options and accessories
Fiber-optic cables, probes, cells, battery pack
18 χ 17 in. footprint; exter nal beam for fiber-optic accessories Validation kit with manual and check standards; fiber optic probe for analysis of liquids and powders
Reader service number E-mail reflector keyword
401 ac NIR622
ΙΝΑ = Information not available at presstlme
736 A Analytical Chemistry, December 1, 1995
402 ac NIR623
ΙΝΑ
Quantum 1200 Plus LT Industries 6110 Executive Blvd. Rockville. MD 20852 301-468-6777
MagnaIR Nicolet 5225 Verona Rd. Madison, Wl 53711 800-356-8088
UV/Vis/NIR On-Line Instruments 130 Conway Dr. Bogart. GA 30622 800-852-3504
$43,000+ Grating monochromator Vis/near-IR Reflectance, transmission, transflectance Fast scan grating mono chromator; high-energy throughput
ΙΝΑ FT
$31,000 Double-beam, double-grating scanning monochromator Reflectance, transmission, transflectance Double-beam double mono chromator with W/halogen source; high-intensity lamp available
Reflectance, transmission, transflectance Michelson interferometer; quartz-halogen source; quartz, CaF 2 , or XT-KBr beamsplitters
Lab/Process Analyzers Perstorp Analytical/ NIRSystems 12101 Tech Rd. Silver Spring, MD 20904 800-343-2036 ΙΝΑ $40,000+ Holographic grating mono Grating monochromator chromator, Vis/Near-IR UV-vis/near-IR Transmission, reflectance, Transmission, reflectance, immersion diffuse reflectance Lab: Predispersive singleDouble-beam double beam diffraction grating. monochromator with Process: Vibration-isolated W/halogen and deuterium diffraction grating; pre/postsources; holographic grat dispersive monochromaings at 360 lines/mm for tors; dual-channel design; near-IR fiber-optic interface Peltier-cooled PbS for near- Si (400-1100 nm); PbS (1100-2500 nm); IR InGaAs (900-2200 nm) Lambda 900 Perkin Elmer 761 Main Ave. Norwalk, CT 06859 800-762-4000
Si, PbS. InGaAs single detectors; Si, InGaAr 256and 512-element array detectors
D-TGS (12,500-350 c m - 1 ) ; MCT (11,700-600 c m - 1 ) ; PbSe (13,000-2000 cm" 1 ); InSb (11,500-1850 c m - 1 ) ; PbS (10,000-4200 cm - 1 )
PMT for UV-vis; PbS for near-IR
Up to 5 full scans/s corres ponding to 6000 discrete wavelengths/s
Up to 50 full scans/s
ΙΝΑ
1200-2400 nm; 400-2400 nm expansion; 900-1800 nm; 400-800 nm 1 nm in near-IR; 0.3 nm in visible
400-2500 nm
185-2600 nm
Scan rates to 9600 nm/min for near-IR with 0.04-10 s integration; integration to 999 s 185-3300 nm
