Portable and handheld spectrometers bring detection and identification capabilities off of the bench and out of the lab, enabling research to take place in the field, quality control to take place at the loading dock and instruments to be taken right to the sample rather than vice versa, increasing efficiency and convenience. There are a wide range of portable spectrometry methods available, including but not limited to Raman scattering, Fourier transform infrared (FTIR) spectroscopy, X-ray fluorescence (XRF) and visible spectroscopy, and applications range from screening of raw materials to detection of illicit drugs to investigations of minerals and environmental samples.
While compact and portable instruments may have some practical limitations compared to their benchtop counterparts, such as resolution or sensitivity constraints, they are often fit for purpose to provide specific answers in otherwise inaccessible settings or conditions.1 There are many factors and features to keep in mind when purchasing a portable spectrometer that will determine its suitability for your specific purpose and applications. Weighing these factors can ensure your new instrument delivers the performance and benefits you expect and require.
Spectral Range, Resolution and Limits of Detection
Specifications like spectral range, resolution and limits of detection are common sense considerations for any spectrometer purchase, and this includes portable and handheld spectrometers. Like traditional benchtop spectrometers, there are a wide range of scientific fields and industries in which handheld spectrometers are used, and each application involves its own target analytes with different concentrations and spectra that need to be addressed. In some applications, such as QC for incoming raw materials, a simple pass/fail determination for one or a handful of analytes might be sufficient, while in other applications, such as geological exploration in the field, accurate identification and quantification of a diverse range of components may be needed.
Looking beyond just the plain numbers, is it useful to also look into resources such as application notes to have confidence that an instrument can do the work you need it to do. Seeing data and spectrograms demonstrating an instrument’s performance in representative situations, such as trace level detection in a specific matrix, can give you a better idea of how the instrument’s spectral range, resolution, sensitivity and other technical specifications will translate into results once you’re holding it in your own hand. Additionally, you’ll want to look into the spectral libraries built in or readily accessible for the instrument to detect and identify the targets you’re interested in, and whether these libraries are comprehensive, customizable and can be easily updated to account for evolving circumstances and regulations, for example, for the emergence of new illicit drugs in forensic applications.
Products to Consider:
- RMP-510 Portable Raman Spectrometer from JASCO
- Metrohm Instant SERS Analyzers (Misa) from Metrohm USA
Sampling Capabilities and Flexibility
The sampling capabilities of a portable spectrometer are some of the most important aspects to examine when considering a purchase, and flexibility is a virtue in this area, especially when you’re dealing with multiple different sample types or unique and difficult samples. It’s advisable to take account of the sample formats that are coming in to you (or that you’re going out to): Are they solids, liquids, powders or tablets? Packed in transparent or opaque containers? Have irregular shapes or heterogenous compositions? Are they especially large or especially small? Are they stored in vials? Are they hazardous? Are they light- or temperature-sensitive?
Ask yourself these questions and then ask whether an instrument has the capabilities and options to address all of the checked boxes. An instrument that makes it as convenient as possible to handle a sample as-is without further preparation or processing can certainly shave time off of workflows and make it faster and easier to achieve reliable results. For example, handheld spectrometers with the ability to sample raw materials through transparent, translucent or even opaque packages eliminates the need to transfer samples into a different, usable format or even open the package at all, which saves time that will ultimately add up. Sampling through the package rather than through direct contact with the sample also lessens the risks of cross contamination. For potentially hazardous materials such as narcotics or unknown chemicals in a public safety setting, through-package sampling also reduces the user’s exposure to the sample. Some instruments further have the ability to automatically detect packaging type and optimize scan parameters without manual adjustment.
Often, specific sampling capabilities are facilitated through the use of purpose-built modules, accessories or attachments, such as tablet sampling or vial sampling modules designed to accommodate specific shapes, sizes and formats. The flexibility to attach different probes to modify spot size can allow you to gain the best results from heterogeneous samples, pinpoint specific areas of interest or reduce power density to avoid damaging sensitive samples. Immersion probe attachments may optimize analysis of certain powders and liquids. Built-in cameras can allow the user to view and document the exact area being sampled. For non-handheld portable systems ensure the sample compartment is large enough for your needs and consider whether it will accommodate diverse and irregular sample shapes - some handheld systems also allow special compartments to be attached for irregular or difficult sample types.
Products to Consider:
- Vaya Raman Raw Material Identity Verification System from Agilent Technologies
- ResQ CQL Handheld Raman Analyzer from Rigaku Americas Corporation
Size and Shape
Portable, handheld, compact, miniaturized – these are all similar words that are not necessarily interchangeable when it comes to laboratory instruments. Not all portable spectrometers are handheld and not all handheld spectrometers will have the same shape or weight, and so on. Some portable instruments may look like smaller versions of their benchtop counterparts and still need a level place to sit during analysis, even if that place is outside the lab; other portable spectrometers can be held and operated in one hand, similarly to a smartphone, small tablet or household drill. Ergonomics and weight are factors you’ll want to keep in mind when considering the length of time the device will be used by a single operator, and whether high-up or hard-to-reach sample locations are involved. Dimension figures, photos and videos can give you an idea of what “portable” really means for each instrument, and any opportunity to demo a device in person is also a big plus.
Products to Consider:
- 5500 Series Compact FTIR from Agilent Technologies
- TerraSpec Halo Portable Mineral Analyzer from Malvern Panalytical
Speed and Efficiency
In one way, speed can be thought of as the time between the start of a scan and the output of a result, and this is an important consideration for any instrument, with many portable instruments capable of delivering a result within seconds. However, speed and efficiency are also closely tied to other factors such as sampling capabilities, ease of use and data management; features in these areas can address potential bottlenecks, streamline your overall workflow and maximize throughput. In many ways, portable instruments inherently excel over benchtop instruments in this area, with many requiring little-or-no sample prep and enabling “point-and-shoot” sampling techniques. However, specific capabilities offer further time savings that can make a big difference, and some more of these efficiency-boosting features will be included in the sections below.
Interface and Ease-of-Use
Design developments in recent years have made portable spectrometers easier to use than ever, with many now available that require very little training and can even be operated by non-specialists.1 One aspect that can determine the difficulty and complexity of operating an instrument is the quality of its display and interface; many if not most modern handheld instruments include either a digital screen and keypad or touchscreen. Ideally, navigating this interface should be intuitive and easy to read with all the information you need available in minimal clicks or taps. The abilities to store and load methods, use barcode scanning for sample and batch tracking, and receive rapid and clear feedback or instructions from the instrument are other examples of features that can make analyses run more simply and smoothly. Features that minimize confusion and reduce steps between scans enable faster and more streamlined workflows overall.
Connectivity and Data Management
The mobile, wireless nature of portable spectrometers means it is important you can be confident the data stored on the instrument can be easily, quickly and securely synchronized with your data management and laboratory information management systems (LIMS). Various pathways for transferring and uploading data can include Wi-Fi, Bluetooth and USB connectivity - consider whether your measurements can be reported from the site or whether a wired connection is needed for data transfer, which may or may not be suitable for your specific purpose. The instrument’s on-board software and compatibility with other software systems should be assessed - for example, does the software make it easy to track samples and batches, generate necessary reports, and view or analyze data on-site via the instrument display or connection to another mobile device? How much data can be stored on the instrument and can you be confident this data is stored safely and securely, with proper user permissions? For some applications, such as geological exploration and field mapping, or environmental research, GPS capabilities allow location data to be seamlessly and automatically integrated into reports. As with other laboratory systems, features that minimize manual data entry make the analysis process more efficient and reduce the risk of human error.
Products to Consider:
- Handheld Raman Analyzer from Zolix Instruments Co., Ltd.
- ASD QualitySpec Trek Portable Spetrometer from Malvern Panalytical
- spetro2guide Portable Spectrophotometers from Paul N Gardner Company
- BRAVO Handheld Raman Spectrometer from Bruker Optics
Durability and Battery Life
Portable instruments that are brought out into the field, into worksites, mines, crime scenes and the great outdoors, should be designed with a greater degree of durability than those offered the protection of a clean and controlled laboratory environment. Dust, water, fluctuating temperatures and vibrations can all easily skew sensitive measurements made from the benchtop – portable spectrometers will likely encounter these factors on a regular basis and require built-in ruggedness to resist interference and damage.Additionally, accidents happen, and the ability to not only survive a drop, but maintain calibration after a minor mishap, is especially important for handheld instruments.1 One thing to keep in mind is that spectrometers that utilize transmissive optics are less likely to be majorly impacted by impacts or vibrations than those that use reflective optics.2 If reflective components are used, it is more important that even minor disruptions can be resisted or avoided.
Lastly, battery life and power consumption need to be taken into consideration when selecting a portable spectrometer. You never want to be in a position where you need to stop in the middle of your process because your spectrometer is about to run out of juice. In addition to just the number of hours the device can operate on a single battery, you should determine whether batteries can be easily changed with little interruption (“hot swapped”) and how long a single battery pack takes to charge. Remaining battery life information should be readily available in the device display, as well as low battery alerts to ensure the instrument can be kept running continuously and reliably.
Products to Consider:
- NF2000 Fiber Optic FT-NIR Spectrometer from Galaxy-Scientific
- Progeny ResQ Handheld Raman Spectrometer from Rigaku Americas Corporation
References
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Crocombe RA. Portable Spectroscopy. Applied Spectroscopy. 2018;72(12):1701-1751. doi:10.1177/0003702818809719
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"Handheld Raman spectrometer," Ibsen Photonics. https://ibsen.com/technologies/raman-spectroscopy/handheld-raman-spectrometer/