Redefining Material Analysis

Federico Izzia explores the trends and benefits of the development of portable and handheld Raman Spectroscopy The attractiveness of Raman spectroscopy for chemical identification analysis is well known and easily explained. Raman provides the unique combination of very material-specific spectral information ? similar to infrared spectroscopy – with the convenience of non-contact, non-destructive sampling. It has the ability to measure materials through packaging, vials and other containers, which are typical characteristics of near infrared (NIR) spectroscopy. Until recently, Raman instrumentation was a complex technique which required spectroscopy, optics, safety precautions and manual setup skills set. These factors limited its acceptance exclusively to academic laboratories and basic research applications. Today, Raman instruments have benefited from tremendous advancements in ease of use, performance, reliability and miniaturisation. As a result, Raman analysis has become increasingly popular in two distinct forms: multi-task microscopy spectrometers configurable to optimise spatial or spectral high resolution, ultra-fast chemical, imaging and depth profiling for research applications particularly in material science, and portable or handheld instruments that are widely adopted for identifying unknowns or verifying the consistency of raw materials. Raman spectroscopy is now a recognised technique in the U.S. Pharmacopoeia (USP) and the European Pharmacopoeia (EP) for raw material identification (RMID) purposes. In addition, it has become a well-established analytical technique for safety and security applications ranging from defence to drug enforcement agencies. The pharmaceutical, biopharmaceutical and more recently the nutraceutical and cosmetic industries are facing increasingly rigorous regulatory standards challenging the sustainability of their traditional laboratory analysis processes. No matter how highly diversified, safety and security chemical identification must be achieved on-site and must provide executable information (risk analysis) as responsively as possible. Despite these applications being very different, one of the key drivers for miniaturisation is the same: rather than waiting for samples to be delivered to an instrument for analysis, the instrument now needs to be taken directly to the sample instead. The form factor is not the only driver for miniaturisation, as ease of use is an increasingly important consideration. Laboratory equipment can be controlled by full-size desktop computers, while handheld or portable devices must be operated by smartphone-like processors, screens and a simplified user interface.   This makes integration into existing workflows a seamless process. Finally, due to the transportable nature of these devices, electronics and other components must be operated by batteries, hence the need for low consumption, miniaturised technology. The handheld form factor is driven by necessity. For example, reaching the polymer packaging inside a raw material drum can be accomplished through fibre optic probes with NIR, but measuring materials using an all-in-one device that can be comfortably operated by a hand directly pointing at the packaging is certainly more efficient. [caption id="attachment_40676" align="alignright" width="200"] Implementation of handheld Raman enables the analysis of incoming materials in warehouse drums[/caption] The challenges associated with the miniaturisation of analytical systems are well documented and Raman spectroscopy is no exception. Combined with end-user expectations for lab-quality analysis and customisable, application-specific solutions that can be easily integrated into existing workflows, manufacturers of portable and handheld Raman analysers have had their work cut out for them. The size of the components in an analytical system dictate the size of the system overall and in the past, this has meant that miniaturising cumbersome lab-based systems has been a challenge. Raman instrumentation has advanced significantly in recent years due to improvements in the components used in Raman spectrometers. Lasers, detectors and electronics are continually getting smaller, more reliable and sensitive, narrowing the gap between full-size equipment and portable spectrometers for material identification/verification purposes.  This enables the collection of data within a few minutes, if not seconds. The usability of handheld devices is a completely different paradigm compared to laboratory equipment. The environment, user skill set, size of the display and the limited operating time –although no longer an issue, thanks to lithium ion batteries advancements – also represent significant challenges. Handheld instruments must withstand a wide range of environmental temperature and humidity conditions. The small display has to be optimised to provide only the strictly necessary functionality and output results, avoiding complex setup and difficult to read result screens. The instrument chassis must also resist mechanical shocks and comply with industry standards normally not required for laboratory equipment. The industrial design has to be inspired by cross-contamination prevention, outdoor operation and robustness for in-field use. Despite their size and “user simplicity,” handheld devices integrate highly sophisticated components, contain the most modern optical technologies, and require an incredible engineering effort. The miniaturisation of Raman instruments has largely contributed to a shift in the materials identification analytical process – both in the industrial sectors and in the way first responders now measure unknown and potentially threatening materials. Previously available technologies represented a significant step ahead compared to traditional lab-based procedures, but the latest developments in handheld Raman devices clearly represents an additional leap toward specificity, safety and actionable information at the point of need. In the RMID process, NIR technology removed significant workload and cost from QC laboratories, but it required extensive chemometric modelling of the raw material classes and variability. In many cases, it lacked in specificity distinguishing materials due to the limited specificity of the spectral information provided. In the safety and security area, portable Fourier Transform Infrared (FT-IR) has certainly been a breakthrough, however, it still required intimate contact with the sample. Raman is a highly specific technique and doesn’t require contact with the sample which has contributed to its rapid and widespread adoption. The good news is that there is always room for improvement. One of the well documented limitations of the Raman technique (no matter the instrument shape and size) has been the issue of fluorescence interference when analysing problematic materials such as sodium carboxy methoycellulose and cell culture media or when measuring through polymer or dark glass bottles. Raman spectroscopy traditionally uses visible laser excitation wavelengths, such as 532 and 785nm, and it is these shorter wavelengths that are susceptible to fluorescence interference. Longer excitation wavelengths like 1064nm minimise the fluorescence limiting factor by far, but until recently, there were no compact size lasers available operating at that wavelength. With the introduction of miniaturised 1064nm lasers, users of handheld Raman will be able to measure more materials and cover more scenarios than ever before. The new generation of handheld Raman instruments are designed to be customisable for seamless integration into any work environment, from industrial routine verifications to emergency situations, measure a broader range of materials, integrate modern electronics for intuitive smartphone-like operation and video capturing, and comply with more stringent industry regulations (data security) and standards. Portable and handheld Raman has a bright future providing users with fast, accurate and point of use analysis across a wide range of applications and will continue to evolve to provide a solution for challenging material analysis. Author Federico Izzia, VP Sales and Marketing at Rigaku Raman Technologies