The Basics of Spectrometers

What is a Spectrometer?
Applications of Spectrometers
How Do Spectrometers Work?
Noise
Raman Spectrometers
Applications for Portable Raman Spectroscopy
About Pacer International

What is a Spectrometer?

By definition, a spectrometer is any instrument or device for detecting and/or analysing various wavelengths of electromagnetic radiation. The term spectrometer can be applied to any instrument that covers any part of a very broad band from gamma rays to far infra-red wavelengths. Those operating over, or close to, the visible spectrum are commonly termed spectrophotometers.

Applications of Spectrometers

In the laboratory, a spectrometer will comprise a radiation source and its associated detection and analysis equipment. These instruments can be tuned for a variety of different applications in analytical chemistry, clinical diagnostics, colorimetry, process monitoring, food and agriculture, gas chromatography and many others. The latest generations of portable systems enable their use in the field for analysis of materials and natural phenomena.

How Do Spectrometers Work?

A spectrometer works by first allowing rays into the instrument via an entrance slit, and then employing a diffraction grating to form a spectral image of the incident light in the image plane. Modern spectrometers feature CCD and linear detector arrays – as the incident light strikes the individual pixels across the array, each pixel represents a portion of the spectrum that the electronics can then interpret and display with a given intensity. The two most common detector materials are Si and InGaAs.

Noise

Noise is a challenge to the performance of spectrometers. The main noise sources found in an array detector include readout noise, shot noise, dark noise, and fixed pattern noise. The effect of dark noise in particular can be mitigated by cooling the array detector with a built-in thermoelectric cooler (TEC) – this also enhances the dynamic range and detection limit.

Raman Spectrometers

Raman spectrometers use the principle of inelastic scattering (Raman scattering) of monochromatic light from a visible, UV or IR laser, and are particularly suited to gas analysis. In operation, the sample is illuminated by the laser beam, and the light from the illuminated sample is collected through a lens and passed to a monochromator. The monochromator filters out all those wavelengths close to the laser line, and the remainder of the collected light is dispersed onto a detector.

Applications for Portable Raman Spectroscopy

In recent years, spectrometer manufacturers such as B&WTek have developed lightweight, portable spectrometers which can be used “in the field” to analyse substances rather than having to take samples back into a laboratory.

The MiniRam III portable raman Spectrometer from B&WTek.

The following list details some of the many applications for affordable portable Raman spectrometers:

Application Area Examples
Bioscience and Medical Diagnosis
  • Subtle changes within biomolecules, such as drug interactions, tissue healing, cosmetics, disease diagnosis
  • Intercellular SERS localization and interaction. Identification of drug binding to cells for Drug-DNA and cellular interaction analysis
  • Investigation of microorganisms in single cells; yeast cell classifications, single bacterium
  • Oxygenation measurements of blood and tissue
  • Molecular level cancer detection (cervical, lung, etc.)
  • Cardiovascular disease diagnosis (atherosclerosis)
Pharmaceutical Industry
  • Analysis of tablets, liquids, and gel caps
  • High throughput screening techniques
  • Crystallization, end point detection
  • Process Analytical Technology (PAT) on-line, at-line monitoring and control: real-time monitoring of drying, coating, and blending
  • Identification and analysis of API, additives and excipients
  • Drug identification control device: Purity and Quality
  • Raw material inspection: 100% incoming material identification & verification
Raman Microscopy
  • Pharmaceutical drug analysis: micro-Raman and localized molecular species analysis in complex drug mixtures such as beta-carotene in multivitamins
  • Material science thin film analysis e.g. diamond film quality characterization
  • Trace forensic evidence analysis, including fibers, fabrics, pigments, inks, etc.
Polymers and Chemical Processes
  • Quality Control: Incoming/Outgoing
  • Identification of contaminants during manufacturing
  • Real time monitoring of polymerization
  • Predicting the morphological properties of polymers
  • Multivariate Analysis/Chemometrics to predict physical properties: glass transition temperature, crystallization temperature, etc.
  • Chemical composition analysis
Forensic Analysis
  • Nondestructive drug and narcotic drug identification
  • Explosives: exact chemical compositions of materials, PETN, RDX and binding agents within explosive materials
  • Identification and analysis of toxic solvents and bio-warfare agents
  • Trace forensic evidence analysis, including fibers, fabrics, pigments, inks, etc., by Raman microscopy
Gemology
  • Non-invasive gemstone identification and examination
  • Identify unknown gemstone by unique Raman signal
  • Identification of isomorph or subspecies of gemstone
  • Analysis of gemstone origin through Raman microscopy
  • Anti-counterfeiting, such as identification of diamond from zircon
Geology and Mineralogy
  • Identification of geological materials
  • Examination of inclusions in minerals
  • Analysis of cement clinker by Raman microscopy
  • Ancient fossil analysis
Food and Agriculture
  • Measuring the unsaturated fatty acid in food oils
  • Detecting bacteria and/or contaminants in food products
  • Identification of additive drugs: nutraceuticals in fruit drinks
  • Analysis of components in grain kernel
Environmental Science
  • Water pollution detection using SERS technology
  • Identification of contaminants in water
  • Petrochemical analysis
  • Identification and analysis of sediments in water
Semiconductor and Solar
  • Characterization of silicon crystallinity: Monitoring of the Raman band shift as silicon crystallinity changes from amorphous to a polycrystalline structure
  • Analysis of micron sized particles in situ to provide information on potential contamination
  • Mechanical stress monitoring for semiconductor process

About Pacer International

Pacer International is a leading specialist supplier of optoelectronic components, systems and displays. Their vast range of products fall into the following categories:

  • LEDs and Sensors
  • Photonics products
  • Information Displays
  • Design and production services

Source: Pacer International

For more information on this source, please visit Pacer International.

Date Added: Sep 22, 2011 | Updated: Oct 3, 2014
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