Of all the scientific techniques for analyzing matter, spectroscopy is one of the most useful. The highly specialized branch of science studies how matter absorbs and emits light, using data to study samples at the macroscopic, molecular and atomic levels.
Based on the concept of using a prism to split white light into a rainbow of colors, spectroscopy spreads out electromagnetic radiation into wavelengths to create a spectrum. Reactions are used to identify individual elements and gain insight into the unique properties of a sample.
The ability to study matter in such detail has made spectroscopy an important research tool in many sectors and industries, from medical imaging and tissue analysis to astronomical research. This led to the development of various types of spectroscopy, generally characterized by the source of radiant energy used to emit light and trigger reactions.
Different types of spectroscopy are suitable for different applications, with each technique offering its own advantages and disadvantages. Below, we take a closer look at the different types of spectroscopy and how the techniques are used for an incredible variety of applications.
X-ray spectroscopy
X-ray spectroscopy uses a beam of charged particles to excite atoms. This forces the electrons to move to a higher energy level. When the electrons return to their pre-excited level, the excess energy is emitted in the form of photons. X-ray spectrometers measure the wavelengths of these photons, using the data to identify and quantify the elements.
Scientists can choose between two techniques - WDXS and EDXS. Although slightly different, both techniques use radiation scattering patterns to map atomic structure and identify elements.
Wavelength dispersive X-ray spectroscopy (WDXS)
WDXS uses a crystal to bend light to create a single wavelength.
Energy Dispersive X-Ray Spectroscopy (EDXS)
EDXS uses a high-energy beam of charged particles to excite electrons and force them to emit radiation.
X-ray spectrometry is widely used for chemical analysis and is a valuable tool in mining, geology, plastics and medical research. X-ray spectrometry has also gained ground in the fields of astronomy and astrophysics, using sophisticated telescopes to study phenomena such as neutron stars and black holes. As a non-destructive analysis technique, X-ray spectrometry is popular with archaeologists who use it to analyze the chemical composition of artifacts.
flame spectroscopy
Flame spectroscopy measures the intensity of light emitted by matter when exposed to a flame. Wavelengths are used to identify elements, while flame color is used to calculate concentrations. Flame spectroscopy is commonly used to identify alkaline elements with weakly excited states, including sodium, potassium, and lithium.
atomic absorption spectroscopy
Atomic absorption spectroscopy (AAS) is suitable for both liquid and solid samples and uses a light source to generate wavelengths of electromagnetic radiation. These wavelengths are used to detect elements by comparing absorption rates with reference data.
The water industry is one of the most recent sectors to adopt AAS technology, with municipalities around the world using the technique to analyze samples and detect contaminants. The highly sensitive AAS spectrometers are capable of detecting extremely low concentrations of particles and impurities, making the technique ideal for H2O analysis.
spark spectroscopy
Also known as atomic arc emission spectroscopy, this analytical technique is used to detect metallic elements in solids. Samples without conductivity are mixed with graphite powder to force reactions.
Espectroscopia UV-Vis
UV-Visible Spectroscopy (UV/VIS) measures the rate at which a chemical substance absorbs light. In the quantitative technique, a source of UV or visible light is directed at a sample and the intensity of the rays passing through it is measured. Absorption patterns are used to identify and quantify various chemical compounds.
UV-Vis spectroscopy addressed the recent challenges it facedmRNA vaccine industry, which struggles with issues such as quality control and bacterial culture growth rates. UV/VIS was introduced as a solution to improve the quality of bacterial cultures with the aim of minimizing contamination and accelerating the production of mRNA vaccines.
UV-Vis spectroscopy is also used to perform important ibuprofen monograph tests in the US pharmaceutical industry. Using a Thermo Scientific™ Evolution™ 260 Bio UV-Vis Spectrophotometer in conjunction with specially designed software, teams use the technique to ensure that ibuprofen absorption levels are within the acceptable range.
near infrared spectroscopy
Near-infrared (NIR) spectroscopy is used for both quantitative and qualitative analysis and is unique because it operates in a specific region of the electromagnetic spectrum. The method analyzes data in the range of 780 nm to 2500 nm, i. H. in the near-infrared range. NIRS is particularly useful in the food and beverage industry, where it is used to analyze the fat, protein, starch and moisture content of products. NIR spectroscopy is also a mainstay in the pharmaceutical industry, with the technique being used to monitor moisture levels in freeze-dried pharmaceuticals.
NMR spectroscopy
Nuclear magnetic resonance (NMR) spectroscopy relies on specialized equipment to map the molecular structure of matter at the atomic level. The advanced technique is also used to determine solubility, phase changes and predict diffusion potential. A magnetic field is used to excite an atomic nucleus and force it to emit radiofrequency pulses. These pulses are used to determine the resonant frequency of the nucleus and ultimately to detect chemical elements.
Fourier transform infrared spectroscopy
Fourier transform infrared spectroscopy (FTIR) uses absorption, emission, and photoconductivity rates to collect high-resolution data for liquids, solids, and gases. The technique works over a wide spectral range, giving it a unique advantage over other methods such as scattering spectroscopy. Results are fast and reliable, making FTIR spectroscopy suitable for a wide range of applications. It is particularly useful for identifying unknown materials, making it a prime technique for screening processes.
FTIR is a workhorse in the pharmaceutical industry, where products must meet stringent regulatory requirements. High sensitivity and a wide spectral range make FTIR spectroscopy a valuable tool for product development, testing and quality control.
In the polymer and plastics industry, FTIR spectroscopy is used to identify compounds such as rubbers, resins and adhesives. From initial design and product development to molecular degradation assessment and failure analysis, the technique is widely used throughout the industry.
Raman spectroscopy
Raman spectroscopy is one of the newest techniques for making waves in the scientific field. The technique uses electromagnetic radiation to record the chemical composition of matter and has the ability to measure multiple variables simultaneously. Raman spectroscopy is not only highly accurate, it also provides real-time results.
In the last decade, it has become a valuable tool for analyzing geological materials. Applications of Raman spectroscopy extend far beyond mining and hydrocarbon exploration, with experts cultivating the analytical technique to predict natural disasters such as volcanic eruptions and earthquakes, graph climate change and manage water resources.
“Raman spectroscopy is an established analysis method for analyzing geological samples. It not only provides a quick and efficient way to identify specific materials, but also comprehensive information about molecular structures and chemical environments."read a reportWritten by Dr Robert Heintz, Thermo Fisher Scientific in-house expert.
Mid-infrared spectroscopy (MIR).
The growing medical cannabis industry has recently embraced mid-infrared spectroscopy (MIR) as an accurate and affordable form of process analytical technology (PAT). AStudy published in peer-reviewed journalSpectrochimica Acta Part A explored the benefits of MIR spectroscopy to quantify phytocannabinoids such as CBD and THC.
“Sample complexity (plant tissue or plant extract), sample variability in horticultural provenance and maturity, and non-uniformity in plant material and ATR flower-crystal contact (in the case of cannabis flowers) governed the accuracy descriptors” , says the summary. "Taking into account the presented results, the ATR-MIR should be considered a promising PAT tool for estimating THC and CBD content in relation to critical materials and quality parameters for cannabis flowers and extracts."
Spectroscopy vs. spectrometers
Although spectroscopy and spectrometry sound similar, it is important to understand the difference between the two terms.
Spectroscopy is the study of the interaction of matter with radiant energy, such as an electromagnetic light source. It is a theoretical term used to describe the absorption properties and behavior of a sample. Spectra generated by matter are analyzed and used to gain information about its unique physical and chemical properties.
In comparison, spectrometry is a practical application for collecting both quantitative and qualitative data. Interactions between light and matter are measured with special instruments that focus on a specific spectrum.
In summary, spectroscopy describes the theoretical science of studying the interactions between matter and radiant energy, while spectrometry is a practical application used to gain detailed information about the unique properties of matter.
Dive deeper into the realm of spectroscopy
The techniques listed above are just a few of the different types of spectroscopy used to analyze matter at the macroscopic, molecular, and atomic levels.reflectance spectroscopyis one of the latest players to enter the scene with the quantitative non-destructive technique being adopted by a wide range of industries, from biological sample analysis to food quality control. Rob Morris, writing for Ocean Insight Inc, dives deeper into the technique"Reflectance Spectroscopy - A Useful Technique for the Analysis of Solid Samples".