Industries Information

 X-ray fluorescence spectrometers (XRFs) use a spectroscopic technique that is commonly used with solids, in which X-rays are used to excite a sample and generate secondary X-rays.  The X-rays broadcast into the sample by X-ray fluorescence spectrometers eject inner-shell electrons. Outer-shell electrons take the place of the ejected electrons and emit photons in the process. The wavelength of the photons depends on the energy difference between the outer-shell and inner-shell electron orbitals. The amount of X-ray fluorescence is very sample dependent and quantitative analysis requires calibration with standards that are similar to the sample matrix.

The solid samples used with X-ray fluorescence spectrometers are usually powdered and pressed into a wafer or fused in a borate glass. The sample is then placed in the sample chamber of the XRF spectrometer, and irradiated with a primary X-ray beam. The X-ray fluorescence is measured either in simultaneous or sequential modes, and is recorded with either an X-ray detector after wavelength dispersion or with an energy-dispersive detector.

X-ray fluorescence spectrometers measure the emitted X-ray fluorescence in either a simultaneous fashion, or sequential.  Simultaneous mode typically measures the entire wavelength range around the emission line of interest simultaneously, while sequential mode typically measures one wavelength at time.

Wavelength dispersive detectors use a nondestructive analysis technique for the identification and quantification of elements in a material. Wavelength dispersive spectroscopy is the measurement x-ray energies emitted from the bombardment of an energy source impinged upon the material, producing characteristic x-rays.  Energy dispersive X-ray fluorescence spectrometers also use nondestructive analysis techniques for the identification and quantification of elements in a material. Energy dispersive spectroscopy is the measurement x-ray energies emitted from the bombardment of an energy source impinged upon the material, producing characteristic x-rays.

XRF was originally used to analyze geological samples. The advancement of computers and other technologies allowed the technique to develop even further.  XRF found its place in many different types of analytical laboratories and some industrial inspection systems. X-ray fluorescence spectrometers provide a number of distinct advantages including easy sample preparation, nondestructive rapid multi-element analysis, and the ability to screen unknowns in a wide array of sample matrices such as liquids, solids, slurries, powders, pastes, thin films, air filters, and many others.  Because of these advantages the technique, it is widely used for research, in industrial settings, and by quality assurance analysts.

Spectrometers, UV and visible, measure the amount of ultraviolet and visible light transmitted or absorbed by a sample placed in the spectrometer. The wavelength at which a chemical absorbs light is a function of its electronic structure and the intensity of the light absorption is related to the amount of the chemical between the light source and the detector, so a UV / Visible spectrum can be used to identify some chemical species.

UV and visible spectrometers may come with one of three common photometric design systems.  Scanning single beam systems can be one of two types of instrument, either a single wavelength light source or a selector for a single wavelength. The light from the lamp is dispersed before reaching the sample cell.  A scanning double beam instrument measures both the transmittance of the sample and solvent at each wavelength simultaneously and computes the ratio. The light from the lamp is dispersed before reaching the sample cell.  All wavelengths pass through the sample and the dispersing element is between the sample and the array detector. This allows the detector to simultaneously record the transmitted light power at multiple wavelengths.  Commonly UV spectrometers and visible spectrometers will have a monochromator, which is used to separate the wavelengths of the light source before the light passes through the sample and enters the detector.

Common detector types found in UV spectrometers and visible spectrometers include photomultiplier tubes, diode arrays and charge-coupled devices (CCDs).  A photomultiplier tube, useful for light detection of very weak signals, is a photo emissive device in which the absorption of a photon results in the emission of an electron. These detectors work by amplifying the electrons generated by a photo cathode exposed to a photon flux.  A diode array detects which light is absorbed and which is reflected.  A CCD chip, is an array of light-sensitive elements. Which are, in fact, some small electronic capacitors. The electrons generated by the light charge these capacitors. In fact, each light element (commonly called photon), that reaches the CCD array’s atoms, displaces some electrons, which are providing a current source. These current sources, are localized in small, delimited areas (the capacitors), called pixels.

Important parameters in specifying spectrometers, UV and visible are wavelength range, resolution and accuracy.  Wavelength range is the dispersion of the grating across the linear array; also expressed as the "size" of the spectra on the array.  The spectral resolution is the width of an analytical peak at half its height expressed in nanometers. A measure of the instruments ability to separate two overlapping peaks. At the point of resolution, two peaks of equal height are said to be resolved if you can see a dip between the tops of the two peaks separate two overlapping peaks. At the point of resolution, two peaks of equal height are said to be resolved if you can see a dip between the tops of the two peaks.  The wavelength accuracy is the agreement between a mean measured value and a true or accepted value as quantified by error. Related to determinate errors and quantified by bias.  Detector sample volume and sample flow rate range are also important specifications pertaining to UV and visible spectrometers.

Many UV spectrometers and visible spectrometers will give measurement values for transmittance, absorbance and reflectance.  Transmittance is the ratio of the radiant power transmitted by a sample to the radiant power transmitted by a blank in an equivalent cell or by some other means of compensation for solvent absorption, reflection losses, etc.  Absorbance is a measure of concentration of material present: negative log (base 10) of Transmittance [- log 1/ T] of product of extinction coefficient, path length, and concentration, written as A = e bc.  Reflectance is the ratio of the radiant energy reflected by a body to the energy incident on it. Spectral reflectance is the reflectance measured within a specific wavelength interval.

Spectrometers are analytical instruments which disperse an emission (such as particles or radiation) according to some property of the emission (such as mass or energy) in order to measure the amount of the dispersion. This product area includes visible, infrared (IR), ultraviolet (UV), atomic absorption (AA), optical emission (OE), Raman, X-ray fluorescence (XRF) and mass spectrometers. Specific search forms are also available. Performance specifications for spectrometers include: spectral range, spectral resolution, mass range, mass resolution, and mass accuracy. Spectral range is the dispersion of the grating across the linear array, or the “size” of the spectra on the array. Spectral resolution is the width of an analytical peak at half its height as measured in nanometers (nm). This value indicates the spectrometer’s ability to separate two overlapping peaks. Spectral accuracy is the agreement between a mean measured value and a true or accepted value as quantified by error. Mass range is a measurement of atomic mass that is expressed in atomic mass units (amu) or Daltons (Da). Mass resolution is the ratio of the mass divided by the change in mass over the area of two peaks.  

There are many different types of spectrometers. UV and visible spectrometers measure the amount of ultraviolet (UV) and visible light transmitted or absorbed by a sample placed in the spectrometer. Infrared (IR) spectrometers measure the wavelength and intensity of the absorption of infrared light by a sample. Atomic absorption (AA) spectrometers use the absorption of light to measure the concentration of gas-phase atoms. Atomic emission (AA) and optical emission (OE) spectrometers determine analyte concentration via a quantitative measurement of the optical emission from excited atoms. Raman spectrometers are used to measure the wavelength and intensity of inelastically scattered light from molecules. X-ray fluorescence spectrometers (XRF) use a spectroscopic technique that is commonly used with solids, in which X-rays are used to excite a sample and generate secondary X-rays.  Mass spectrometers separate ions by their mass-to-charge (m/z) ratios. They are used to identify compounds by the mass of one or more elements in the compound. They are also used to determine the isotopic composition of one or more elements in a compound.

Specialty spectrometers and accessories are specialty or proprietary products and accessories related to spectrometers, analytical instruments that are used measure the amount of dispersion of a property such as mass or energy. Like other types of spectrometers, specialty spectrometers are used to determine chemical composition and to perform electromagnetic radiation analysis by measuring light intensity across the visible, ultraviolet (UV), and infrared (IR) spectrums. A specialty spectrometer can be built using optical detectors such as charged coupled devices (CCD) or photo diode arrays, or fiber optics.

Specialty spectrometers and accessories are often application-specific and differ in terms of performance specifications such as wavelength range, optical resolution, sensitivity or absorption, and data capture speed. Products used in thin film analysis are different from those used in biomedical applications, or for monitoring inline process control. Some specialty spectrometers are used in medical imaging applications. For example, nuclear magnetic resonance (NMR) spectroscopy is used to determine physical and chemical information about a specific molecule, typically organic compounds. Resonance spectroscopy is based on the magnetic property of an atom’s nucleus and its response to an electromagnetic field. This is the technique used in magnetic resonance imaging (MRI).

Many other types of specialty spectrometers are available. Secondary ion mass spectrometry (SIMS) is a technique for analyzing the surface of a thin film test sample. An ion mass spectrometer is used to analyze the particles emitted by an object after it is bombarded with a stream of ions or charged particles. Electron auger spectroscopy is also used to analyze surface composition of materials. Auger electron spectroscopy (AES) measures the energies of Auger electrons, which are created by bombarding the sample with an electron beam. Auger electron energies are tabulated based on the Auger effect or process.

Suppliers of specialty spectrometers are located across the United States and around the world. They conform to various quality standards and regulatory requirements.

Raman spectrometers measure the wavelength and intensity of inelastically scattered light from molecules. They are used to determine the chemical composition of a sample based on the wavelength and intensity of the light passing through the sample. Raman spectroscopy is based on the theory of Raman scattering, which states that light is scattered due to the vibrations of the molecules in the substance or substrate through which light passes. This vibration scatters the light and changes its energy from that of the incident light. In this way, Raman spectrometers use the Raman effect by comparing the different energies of the incident light and the scattered photons.

Raman spectrometers are similar to infrared (IR) spectrometers in that both an IR spectrometer and Raman spectometer measure the vibrational energies of the molecules in a sample. Infrared spectroscopy or IR spectroscopy measures the absorption of light of certain energies that correspond to the vibrational energy of the molecule. Since Raman scattering is different from infrared absorption, the two methods of spectroscopy are often used to provide complementary data.

Raman spectrometers often use lasers, the most typical being an argon ion laser. A laser spectrometer offers many benefits, including focused, high-powered excitation of the tested substance which results in a high incidence of light scattering. Because the Raman effect measures the difference between scattered and incident light, Raman spectrometers are particularly useful in gathering data from a small section of a sample. Consequently, Raman spectrometers are being used to develop confocal microscopy techniques. The incident laser radiation of the Raman spectrometer is focused with the microscope objective on a point in the sample. The resulting Raman spectrum contains data almost exclusively from a point within the sample.

Suppliers of Raman spectrometers are located across the United States and across the world. They meet a variety of regulatory requirements and quality standards.

Polarimeters are instruments used to measure the rotation of the plane of vibration in polarized light. Light polarization can be measured using a Stokes vector polarimeter. The polarization properties of a particular material can be measured with a Mueller matrix polarimeter. Typically, Mueller matrix polarimeters are used to determine the purity of materials such as sugar, vitamins, steroids, and antibiotics. Polarimetry of thin films and surfaces is called ellipsometry, which is used to provide information about layers that are thinner than the wavelength of the light itself, down to a single atomic layer or less. An interferometer uses the interference pattern of two beams of light to make very precise measurements. Interferometers can measure minute surface irregularities in optical devices such as mirrors. In astronomy, interferometers can measure the distances between celestial objects and their diameters. The most sensitive polarimeters are based on interferometers, while more conventional polarimeters use polarizing filters, wave plates or other devices.

Choices for polarimeters include: complete vs. incomplete, sequential vs. simultaneous, monochromatic vs. polychromatic, non-imaging polarimeter vs. imaging polarimeter, and manual (visual) vs. electronic (automatic). For pharmaceutical testing, most work is done using 589 nm light (sodium D line). For electronic (automatic) polarimeters, total accuracies of 0.01° are possible. The light source in a polarimeter can be a spectral arc lamp (sodium or mercury), or an incandescent lamp (tungsten). Spectral arc lamps can be designed for visible, ultraviolet (UV) and infrared (IR) wavelengths, and are suitable for stability of wavelength and long-term calibration. Incandescent lamps are less expensive than spectral arc lamps, but limited to visible and IR radiation.

ASTM International (formerly called the American Society for Testing and Materials (ASTM), maintains ASTM C1426 regarding the standard practices for verification and calibration of polarimeters. Other standards describe how to use polarimeters in standard tests (i.e. ASTM F218 for analyzing stress in glass). The Society of Manufacturing Engineers (SME) maintains SME EM930116 for the rapid contour measurement of composite structures utilizing a three-dimensional (3D) tracking interferometer.

Mass spectrometers are used in both quantitative and qualitative analysis, including high-resolution accurate mass measurements for the determination of elemental compositions. Mass spectrometry (MS) is an analytical spectroscopic tool primarily concerned with the separation of molecular (and atomic) species according to their mass. MS can be used in the analysis of many types of samples, from elemental to large proteins and polymers.

Important performance parameters to consider when specifying mass spectrometers include mass range, resolution, mass accuracy and mass spectrum.  Mass range is a measure of the atomic mass range detected by the spectrometer in Atomic Mass Units. May also be measured in Daltons.  The resolution is the ratio of the mass divided by the change in mass over the area of two peaks. (m/dm).  The mass spectrum is a spectrum obtained when ions (usually in a beam) are separated according to the mass-to-charge (m/z) ratios of the ionic species present. This plot is a graphical representation of m/z values versus measured ion abundance information.

Mass spectrometers have one of five common mass analyzer designs.  The mass analyzer is the part of the spectrometer that analyzes the process by which a mixture of ionic species is separated according to the mass-to-charge ratio (m/z). The analysis may be qualitative and/or quantitative.  Time of Flight (TOF) instruments utilize the times taken by ions to pass (fly) along an evacuated tube as a means of measuring m/z values and therefore of obtaining a mass spectrum.  Quadrupole mass spectrometers consist of an ion source, ion optics to accelerate and focus the ions through an aperture into the quadrupole filter, the quadrupole filter itself with control voltage supplies, an exit aperture, an ion detector, detection electronics, and a high-vacuum system.  The ion-trap mass spectrometer uses three electrodes to trap ions in a small volume. The advantages of the ion-trap mass spectrometer include compact size and the ability to trap and accumulate ions to increase the signal-to-noise ratio of a measurement.  Fourier-transform mass spectrometry takes advantage of ion-cyclotron resonance to select and detect ions.  Single focusing analyzers use a  circular beam path of 180, 90, or 60 degrees. The various forces influencing the particle separate ions with different mass-to-charge ratios. Double focusing analyzers have an electrostatic analyzer added to separate particles with difference in kinetic energies.

Mass spectrometers use one of four ionization methods to ionize the sample for analysis.  The electrospray ionization (ESI) source consists of a very fine needle and a series of skimmers. A sample solution is sprayed into the source chamber to form droplets. The droplets carry charge when they exit the capillary and, as the solvent evaporates, the droplets disappear leaving highly charged analyte molecules. ESI is particularly useful for large biological molecules that are difficult to vaporize or ionize.  In fast atom bombardment (FAB) a high-energy beam of neutral atoms, typically Xe or Ar, strikes a solid or low-vapor-pressure liquid sample causing desorption and ionization. It is used for large biological molecules that are difficult to get into the gas phase. The sample is usually dispersed in a matrix such as glycerol. FAB causes little fragmentation and usually gives a large molecular ion peak, making it useful for molecular weight determination.  An electron impact ionization (EI) source uses an electron beam, usually generated from a tungsten filament, to ionize gas-phase atoms or molecules. An electron from the beam knocks an electron off of analyte atoms or molecules to create ions.  Matrix-assisted laser deposition/ionization (MALDI) is a LIMS method of vaporizing and ionizing large biological molecules such as proteins or DNA fragments. The biological molecules are dispersed in a solid matrix such as nicotinic acid or dihydroxybenzoic acid. A UV laser pulse ablates the matrix that carries some of the large molecules into the gas phase in an ionized form so they can be extracted into a mass spectrometer.

 Infrared (IR) spectrometers measure the wavelength and intensity of the absorption of infrared light by a sample. Infrared light lies between the visible and microwave portions of the electromagnetic spectrum and has a range of wavelengths. Near infrared light is closest in wavelength to visible light. By contrast, far infrared light is closest to the microwave region. Mid-infrared light is energetic enough to excite molecular vibrations to higher energy levels. These vibrations, which are caused by changes to a molecule’s dipole moment, occur only at those frequencies where the molecule absorbs infrared light. Because the wavelengths of infrared absorption bands are characteristic of specific types of chemical bonds, infrared spectrometers are often used to identify organic and organometallic molecules.

There are two basic types of infrared spectrometers. Fourier transform infrared (FTIR) spectrometers are single-beam instruments that use an interferometer to spread a sample with infrared light and measure the intensity of the infrared light not absorbed by the sample. The application of a Fourier transform converts the resulting time domain digital signal into a frequency domain digital signal. Dispersive infrared spectrometers use visible lasers, a grating, and charged coupled devices (CCDs) to collect data. The laser acts as a light source and irradiates the sample. Most of the radiation scatters elastically at the same energy as the incoming laser radiation. A small amount, approximately one photon in a million (0.00001%), scatters from the sample at a wavelength shifted slightly from the original wavelength.

Selecting infrared spectrometers requires an analysis of performance specifications such as wavelength range, resolution, accuracy, and infrared range. Wavelength range is the dispersion of the grating across the linear array, or the “size” of the spectra on the array. Resolution, a measure of an instrument’s ability to separate two overlapping peaks, is the width of an analytical peak at half its height. Typically, resolution is measured in nanometers (nm). At the point of resolution, two peaks of equal height are said to be resolved if the dip between the tops of the peaks is visible. Accuracy, another important specification, is the agreement between a mean-measured value and a true or accepted value as quantified by error. Three are three infrared ranges for infrared spectrometers: near (0.75 – 3.00 µm ), mid (3.00 – 6.00 µm) and far (6.00 – 15.00 µm). Operating temperature and operating humidity are other performance specifications.   

There are several system configurations for infrared spectrometers. Monochromatic instruments such as Czerny-Turner designs consist of fixed entrance and exit slits, fixed focusing mirrors and a rotatable diffraction grating. As the grating rotates, a different wavelength is focused on the exit slit. Filter systems or polarizers use near infrared filters that are mounted on a temperature-controlled filter wheel and controlled by a microprocessor. Acousto-optical tunable frequency (AOTF) devices include a single-element detector and overcome many of the mechanical problems associated with multi-wavelength filter instruments. Michelson interferometers split infrared energy into beams which are then recombined optically. The  two beams interfere with each other to produce a complex waveform.

There are many detector types for infrared spectrometers. Examples include deuterated triglycine sulfate (DTGS), deuterated lanthanum triglycine sulfate (DLATGS), indium antimonide (InSb), lithium tantalate (LiTaO3), and silicon (Si). Mercury cadmium tellurium (MCT) exhibits a wavelength cutoff proportional to its alloy composition. In the long wavelength spectral region, photoconductive detectors (PC-MCT) are best suited for meeting low-noise requirements. At shorter wavelengths, photovoltaic devices (PV-MCT) are suitable choices. Photoacoustic detectors measure the energy transfer from a modulated infrared beam into a mechanical vibration.

Flame photometers use atomic emission for the routine detection of metal salts, principally sodium (Na), potassium (K), lithium (Li) and calcium (Ca). A flame photometer is an instrument used for measuring the spectral intensity of metals present in the metallic salt. A flame photometer at low temperature measures the concentration of sodium and potassium present in the metallic salt. To measure the concentration of potassium present in the soil, the soil is grind and then passed through a 2 mm mesh sieve. Next, approximately 20g of air dried soil is transferred into a bottle and about 50 ml of ammonium nitrate solution is poured into it. Before shaking, this mixture is passed through a flame ionization detector. The mixture is shaken using a shaking machine for 30 minutes and at a rate of 275 strokes per minute. The shaken mixture is filtered using filter paper to retain the extract of the solution. The amount of potassium in the extract is determined using flame photometry. This is a very effective salt detection process. There are many types of flame photometers. Examples include PFP7 and PFP7/C flame photometers. A PFP7 flame photometer is a single channel photometer used for measuring sodium and potassium salts. A PFP7/C is a clinical flame photometer and is used for salt detection at low temperature. Other flame photometers are commonly available.

There are several ways in which flame photometers function. Flame photometers are also generally known as spectrometers and work by vaporizing metallic salts in a very hot flame. The quantitative analysis of vaporized metallic salt is then performed to measure the intensity of metals present in the metallic salt. The size of a flame detector in a flame photometer should be 420*360*300mm. A flame photometer for performing atomic emission of salt requires an electrical voltage of 90 - 125 volts. In addition, it requires air as moisture and an oil free specification of 6 liter/minute. Flame photometers are designed and manufactured to meet most industry specifications.

Flame photometers are used in many applications. Some examples include analysis of salt presence in biological material, and identifying the composition of alkali and alkaline salts present in the earth composition. Flame photometers should adhere to the standards used for the construction of a model 410 clinical flame photometer.

Fiber optic probes collect light or spectra from extreme environments inside reaction vessels at high temperatures or pressures. Product types include UV-Vis spectroscopy probes, Raman spectroscopy probes, and refractometry probes. UV-Vis spectroscopy probes track the electronic transitions of molecules as they absorb light in the ultraviolet (UV) and visible (Vis) regions of the electromagnetic spectrum. These fiber optic probes can be used with a wide range of samples and are suitable for biochemical, biological, and pharmaceutical research. Raman spectroscopy probes collect scattered light from a sample that is illuminated with a laser. Molecular components are identified through an analysis of the wavelengths and intensities of the scattered light. Because of their ability to avoid sample contamination, Raman spectroscopy probes are often used in polymer and semiconductor applications. Refractometry probes are fiber optic probes that detect the deviation of light by a solution as a measure of specific gravity. They are sometimes used in the identification of gemstones.

Fiber optic probes differ in terms of optics technology. Choices include holographic optics, immersion optics and insertion optics. Holographic optics produce a hologram through the use of high-precision optical hardware such as collimators, mirrors, spatial filters, optical lenses, camera lenses, exposure meters and beam splitters. Immersion and insertion optics feature single, double or triple-window designs and can be directly inserted into high-temperature reaction vessels and process streams. Like holographic optics, immersion optics and insertion optics provide high signal-to-background measurements along various lengths of optic fiber. Optics working distance and optical fiber specifications are also important considerations when selecting fiber optic probes. As a rule, single fibers or single collection fibers are less expensive than multi-fiber fiber optic probes. In some products, standard telecommunications fibers are used to provide enhanced mechanical stability.

Fiber optic probes differ in terms of applications. Raman spectroscopy probes can be used to analyze samples, obtain chemical intermediate information from automated laboratory reactors, monitor in-situ crystallization, detect end-points, and identify polymorphs. UV-Vis spectroscopy probes are available in both dual beam and diode array designs. Dual-beam fiber optic probes offer superior flexibility and precision. Diode array fiber optic probes combine flexibility with relatively high speeds. Refractometry probes are used in medical fields such as hematology.