Soon after the first spectrophotometer was built, the challenge of improving it began. How could we make spectrophotometers better? Could we make them smaller, faster, or perhaps improve the measurement that was made by them? Would extending the wavelength range make a difference in the measurements we made? Throughout the years we have seen a steady progression in the reduction of the size of the spectrophotometer to the point that we are now capable of bringing the instrument to the sample on a routine basis as opposed to the traditional method of bringing the sample to the instrument. This capability has transformed the way we solve problems, as we are now able to move the instrumentation to the process line and reduce the time it takes to make decisions concerning the process. It has also allowed instrumentation to become mobile. Communicating with and powering instrumentation has changed dramatically over the years. Gone are the days of needing thick communication cables, with the advent of USB connections and wireless communication.
Sample size is another area that has provided a challenge to the analyst. There are many times when sample volume is limited and diluting is not an option. Over the past decade, there have been many improvements made to enable the analyst to use less than 4 μL of solution to make an accurate measurement.
Pittcon® 2013 saw a continuation in the reduction in size of the spectrophotometer with the introduction of several new models by exhibitors. With these new introductions come additional improvements in the remote measurement field. In addition, new low-volume cells were exhibited that are easy to use.
Reduced sample volume
One of the big challenges over recent years has been: What is the best way to reduce the sample volume for analysis and not increase the problems of cleaning the cell? Small-volume cells are notorious for causing problems when you try to clean them. This year, two companies introduced similar products. SCINCO (www.scincoamerica.com) exhibited the Nano Stick-D, a short-pathlength cuvette. It comes in two configurations: single port and dual port. The cuvette is held together magnetically. To use the cuvette, one simply pulls it apart, places a drop of analyte on the window, and allows the other half of the cuvette to affix itself via magnets.
BioDrop (www.biodrop.co.uk) announced during Pittcon 2013 the release of the BioDrop cuvette. A cuvette held together by magnets, it makes use of small pins to reproducibly set the pathlength to be 0.5 or 0.125 mm. The BioDrop Cuvette can be used on any of BioDrop’s three new spectrophotometers the μLite, Duo, or Touch. It is intended for fast microvolume measurement.
Reduction in spectrophotometer size
A major emphasis in the new products introduced this year was the physical size of the spectrophotometer. Introductions of new hand-sized absorption and Raman spectrophotometers were seen. The units ranged in size from a few inches to a spectrometer on a chip. Tornado Spectral Systems (www.tornado-spectral.com) introduced compact models for both absorption and Raman spectroscopy. The OCTANE is designed to have a flexible center wavelength and has up to a 350-nm spectral range. Its major application is for use as an optical coherence tomography (OCT) spectrometer. The company also introduced the HyperFlux U1, and plans to release the HyperFlux Flash in the near future. Neither of these has slits; the systems are powered through a USB connection.
Ocean Optics (www.oceanoptics.com) also released a slitless Raman spectrometer called the Apex 785. It offers high throughput while being able to maintain resolution. Along with the Apex 785, Ocean Optics released the Ventana 787, which has a slit. The goal of these products is to allow the user to make fast, accurate measurements. This permits the user to move the measurement from the lab to the process line. Because of the speed of the measurement, one is able to look for transient signals.
Joining the ranks of companies offering a small spectrometer is Avantes (www.avantes.com), with the AvaSpec-Mini and AvaSpec-Micro. These units are further examples of the ability to take the system to the sample as opposed to taking the sample to the system. In the visible light region, the AvaSpec-Mini offers spectral resolution of 0.5 nm, which is more than sufficient for many applications, and is no larger than a deck of standard playing cards. Potential use in on-line process control is again a strong plus for this size instrument. This is further enhanced by the ability to select different detectors to optimize for the signal-to-noise ratio desired and the wavelength range. Digital inputs and outputs (also offered by other companies with their products) make the unit suitable as an OEM product, thereby opening up the applications.
First-level screening of gemstones is an ideal application for small spectrophotometers. Screening of this nature is done to provide information on the quality as well as the origin of the gemstone. For instance, it is possible to detect treated diamonds from natural diamonds. Historically, this has been done on a conventional size spectrophotometer, but with the downsizing of the instrument, it is easier to make this measurement.
While not as small as some of the other products seen, the i-RamanEx from B&W TEK Inc. (www.bwtek.com) is still a very portable Raman spectrometer. It is built around fiber optics that make use of 1064-nm light. The unit is useful for biological samples. The choice of 1064-nm light is based on the desire to eliminate as much fluorescence as possible. Typically, using 785-nm light can result in fluorescence occurring in the samples and impacts the ability to detect the analyte in question. By simply changing the source radiation, the user eliminates the need to use alternative methods to remove the fluorescence signal. The i-RamanEx is well-suited for chemical warfare agent detection as well as forensics analysis. Additional field applications include oil and drug analysis.
Rigaku Raman Technologies (www.rigaku.com) introduced FirstGuard™, the first handheld Raman instrument available on the market with 1064-nm, 785-nm, or 532-nm laser excitation. Battery powered to reduce potential downtime, it is 21CFR11 compliant, making it an ideal instrument for pharmaceutical companies desiring to perform raw material ID anywhere in the manufacturing plant. Applications include, but are not limited to, pharmaceutical raw material verification, finished drug product authentication, counterfeit drug verification, academia, and narcotics and explosives identification.
Additional spectrophotometer applications
In addition to the reduction in sample volume and physical size of the spectrometer, there were a number of new products worth mentioning that revolve around other applications. Some of these include the F10-ARc and aRTie from Filmetrics (www.filmetrics.com), which allow users to determine the film thickness of samples. Power is supplied to these instruments via the USB connection. Of particular interest is the F10-ARc’s ability to measure film thickness on a curved surface.
ATAGO (www.atago.net) exhibited the new Sac-i saccharimeter, which will work in combination with their other units to report International Sugar Scale, purity, and concentration determinations. While the method has been used for years, it has been less automated than the current ATAGO offering. The new combination reduces potential errors by eliminating the physical input of values with the automatic transfer of data via a USB connection.
Staying with the food industry, Next Instruments (www.nextinstruments.net) introduced the MultiScan Series 4000. The instrument and software are kept simple through the use of touchscreen commands. The company’s analyzers are particularly well-suited for the food and agriculture industries. Measurements of stock feed are very important to the agriculture industry. An important factor in making accurate measurements on whole or ground grain is the sampling technique. Next Instruments makes a number of measurements at different places on the sample to obtain a representative answer. Some other measurements that are of interest to food/agriculture include moisture content, protein concentration, and fat content, all of which can be made on the company’s analyzers.
A fascinating area of spectroscopy is the terahertz frequency (THz) range. Advantest (www.advantest.com) displayed the new TAS7500 series. In addition to the standard instrument, which has the ability to measure samples in the pharmaceutical blister pack, Advantest showed the TAS7500IM imaging system. This system has the ability to map out the various thicknesses of a tablet as well as determine the film strength of the coating. So far they have been able to show differences in the THz spectra of 20 different amino acids. Add the capabilities of the Bio-ATR Accessory and you have some very exciting potential. The Bio-ATR Accessory allows one to do fundamental studies of macro cell activities (live cells). This means it should be possible to add a pharmaceutical and watch the live interaction between it and the cells.
Returning to the area of monitoring transient or high-speed events, there are the new offerings from SpectraLine (www.spectraline.com): the ES 200 and the VS 100. The products were developed by SpectraLine’s parent company, En’Urga Inc. (www.enurga.com). The ES 200 collects spectra from 1.2 to 4.8 μm at 1.3 kHz, while the VS 100 collects spectra from 0.3 to 1.1 μm at a speed of 40 Hz. These capabilities allow such things as process monitoring in metal and glass foundries, explosion studies, following combustion inside engines, and determining rocket plume signatures.
Also introduced was the SPECTROSCOUT, a portable ED-XRF analyzer, by SPECTRO (www.spectro.com). Its small size and weight make it ideal for its purpose: field portable XRF measurements. The ability to make accurate measurements in the field will be a tremendous time and cost savings in the mining industry.
Finally, there were the innovative offerings of PiePhotonics (www.piephotonics.com). Following the release of Pie-in-a-Box™ at BIOS & Photonics West 2013, Pie Photonics brought out three new products at Pittcon 2013: PieWave™, PieDelta™, and MintPie™. The company received the Pittcon Editors’ Bronze Award for its innovative products. The heart of each system is an interferometer that has no moving parts. The technology also gives rise to the name Pie Passive interferometric engine. Because of the ability to easily use the products in different combinations to measure information, analyze quality, and sense changes using light, it can be said that Pie™ technology is the Swiss Army Knife of optical measurement. Traditional applications of interferometers will be enhanced by Pie technology because of the modular design of the Pie components. Their physical size and ruggedness will be an asset to a newfound mobility to make a measurement. Applications include, but are not limited to, optical coherence tomography (OCT) by providing spectral domain (SD) and temporal domain (TD) analyses, food and drink quality and contamination analysis through absorption measurement, material analysis through laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy, and medical sensors such as surface plasmon resonators.
There were many exciting and innovative offerings at Pittcon 2013. As with any review, there is a limitation on what can be covered. If a product was not covered, it was not an intentional slight. Optical spectroscopy encompasses a large number of techniques and it is next to impossible to cover every good product that was shown. Those products that have been discussed here will clearly enhance the ability of the researcher and analyst to make fast and accurate measurements.
Where will the field of spectroscopy go from here? Given the new products exhibited at Pittcon 2013, it is reasonable to imagine the continued “pushing of the size” envelope. New, innovative light sources could come into play next, as the ability to collect a signal is limited by the number of photons you start with and the overall signal-to-noise ratio of the measurement. We can all look forward to Pittcon 2014 and beyond to watch how optical spectroscopy moves forward.
Mark Fisher, Ph.D., is an Applications Engineer for Optical Spectroscopy, Agilent Technologies, 13000 Weston Pkwy., Cary, NC 27513, U.S.A.; tel.: 919-677-6807; e-mail: firstname.lastname@example.org.