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 PRODUCTS
MODI Mobile Dual-pulse Instrument for LIBS analysis of materials |
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Modi is a fully integrated and transportable system for
LIBS multi-elemental analysis of materials. The possible fields of application
include:
LIBS analysis is a simple and fast technique. Operating Modì simply requires connecting the instrument to a 220 V power line. No sample preparation or transportation is necessary. The device can be installed close to the sample under examination, without need for expensive and risky transportation of large and valuable objects. Data acquisition is rather quick: you can get a LIBS spectrum in just a few seconds. Data analysis can be performed right after acquisition with the LIBS++ software. Qualitative elemental analysis is straightforward: you can identify an element on the acquired spectrum in less than one minute. A unique property of Modi is the possibility of standard-less quantitative analysis with the CF-LIBS® option of LIBS++ software. FEATURES AND TECHNICAL SPECIFICATIONS
The instrument includes:
 
PRINCIPLE OF OPERATION Modi performs multi-elemental analysis with LIBS (Laser Induced Breakdown Spectroscopy) technique. Basically, this means extracting information on the atomic composition from the fluorescence spectrum of the plasma generated by a laser pulse on the sample surface.
In particular, Modi employs a dual-pulse laser. That is, the plasma is generated by two successive pulses separated by a few microseconds. The use of double-pulse LIBS results in lager signal-to-noise ratio, corresponding to lager sensitivity and lower detection limits, as compared to single-pulse LIBS. The time delay between laser pulses is accurately controlled, so to give good reproducibility in the resulting spectra. The spectrum of plasma fluorescence is recorded through a broadband Echelle spectrometer coupled to an intensified CCD camera. The Echelle technology allows simultaneous acquisition of the whole visible spectrum with high resolution. The image intensifier serves at the same time as a signal amplifier and as a fast shutter, to selectively detect the short plasma fluorescence after the laser pulses. The recorded spectra can be analyzed with the LIBS++ software. For qualitative analysis, different elements are identified by comparing the position of the peaks in the spectrum with an in-built database. The height and width of peaks give information on the relative amount of the corresponding element within the sample. The LIBS analysis provides information on the elemental composition of the sample surface. However, the ablative action of laser pulses gives also access to the material layers beneath the surface. A stratigraphic analysis is possible by recording several spectra corresponding to successive laser shots taken at the same point of the sample surface.
The sample under analysis can be either placed inside a chamber or externally accessed through an articulated arm for laser pulse delivery. The latter configuration applies to large samples, whenever it is not possible/convenient to detach a portion of material to fit in the internal chamber. Use of the internal chamber is normally recommended, both for positioning precision of the spot under analysis and for safety reasons. The internal chamber is equipped with an accurate positioning system, made of a tri-axial translation stage that is controlled through the joystick on the front panel. With the aid of an internal viewer, the user can select the exact point of the sample surface to analyze; and he/she can precisely focus the laser radiation on the sample.
INTERNAL CHAMBER: SAMPLE POSITIONING AND IMAGING Modi is equipped with an internal chamber to perform
analysis in safe conditions, and to precisely direct the laser beam on
the sample surface. The user can track the sample positioning on the laptop
monitor through an internal viewer; the motorized tri-axial translation
stage is controlled through the joystick on the front panel. All motorized
stages are from Physik Instrumente (PI) s.r.l. In the chamber, the sample is positioned on a mobile base that can be translated along the X and Y horizontal axes. The laser beam hits the sample from the upper vertical direction, and is tightly focused around the centre of the chamber. With the horizontal controls, the user can precisely select a spot on the sample surface to analyze. The Z-axis translation stage moves the laser focus along the vertical direction.
ARTICULATED ARM FOR ANALYSIS ON EXTERNAL SAMPLES
QUANTITATIVE ANALYSIS The atomic spectral lines are used to determine elemental composition or elemental concentrations in the sample. Emission spectrum is characteristic for each emitting element in the plasma, which allows qualitative and quantitative multi-elemental analysis. Emission intensity allows the measurement of the concentration of the element in the sample. Thanks to a new methodology (standardless CF-LIBS© software), standard
reference samples or calibrations curves are not necessary.
APPLICATIONS LIBS allows to realize multi-elemental analysis on untreated samples. It is a very versatile elemental technique enabling analysis of very small amounts of material, 0.1 µg to 1 mg, of solids, liquids or gases (non conducting and conducting materials), with little or no sample preparation; moreover LIBS is non invasive, due to very small sampling area. The LIBS technique, for its wide variety of applications, is particularly suitable for in-situ analysis, monitoring of industrial processes and environmental diagnostics. The range of applications include instant analysis of a variety of materials, as metallurgical, ceramics, polymers, biomedical, biological, in-vivo medical samples, forensic, pharmaceutical, environmental, and so on. Here we report some examples. See also the application notes below.
Surface scan on a steel pipe with LIBS analysis, showing hot spots in the concentration of several elements.
Comparison between CF-LIBS and cupellation on gold samples:
Analysis of a bronze door (Gilberti's Paradise door, Florence Baptistery); comparison between LIBS and other analytical techniques:
Hair Tissue Mineral Analysis (HTMA) is one of the most diffused techniques for screening of metal poisoning in individuals exposed to working or environmental risks. Most recently, this kind of analysis has been extended to the analysis of non-poisonous elements in hair, since it is believed that the measure of mineral content of the hair can give an insight of the general health conditions of the subject. The pictures below show a typical LIBS spectrum on human hair, and correlation with analytical data:
APPLICATION NOTES
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If
the sample cannot fit into the internal chamber, the laser can be directed
externally through the articulated arm (optional). If the instrument is
equipped with an articulated arm, the optical fibre for light collection
is Y-shaped, and one end is laid externally along the arm.
