Analysis of the Matrix Effect of Metal Elements in Soil Measured by a Laser-Induced Breakdown Spectrometer (LIBS)
A. Data Conversion and Calibration
Raw data files are converted into wavelength units using the Channel-Wavelength Conversion module. The wavelengths are calibrated in reference to the stored library data file of the same element.
B. Data Integration and Measurement
The converted data files are downloaded into the Peak Identification module for analysis and measurements. The data can be measured in terms of peak height, position, and width. ACAS uses high powered algorithms that can measure 100 integrated spectra in 15 seconds.
C. Search, Calibration, and Quantitative Identification
The fitted peak data is downloaded to the Spectral Analysis module, which carries out a search in order to analyze, calibrate, and identify the input data.
Example of Application:
In this tutorial, the user will search for three elements in a soil
sample. The results of the search will then be used to determine the detection
limit of an analyte. First, the user should open the Peak
Identification module and open the file 4ap04.dat. This is the raw
data of the soil matrix sample. The user should fit the peaks and save
the fitted parameters. ACAS will automatically save the file under the
name 4ap04.asd. After the peaks have been fitted, the user should open
the Spectral Analysis module, and load 4ap04.asd.
The user should then conduct a search, using the same file and the elements
Al, Be, and Si. The
Search Results Report shows
that they are all present in the sample. After searching, the results can
be viewed graphically for easy comparison. The
user should open the graphs of each of the elements as well as the graph
of the soil sample simultaneously. The user should also make sure that
each graph is using the same scale so that the peaks will line up evenly.
By viewing the graphs of each element (the first three graphs) and comparing
them against the graph of the original soil sample (the bottom graph),
the user can clearly see which elements are present, and where the strongest
peaks are located. In this example, the strongest
peak (located at 288.175 nm) is identified as Si. The peaks located around
309 nm are identified as Al. The presence of Be is clearly revealed by
the fingerprint around 313.12 nm. The user can now determine the concentration
ratio of each of the input files (4ap02.dat, 4ap03.dat, and 4ap04.dat)
using the
Concentration Analysis Module.
After the peaks in each input file have been identified, the graphs can
be compared. (The peaks in the other two graphs were identified using the
same process.) The concentration of Be in each data file can be determined
using the Concentration Analysis Report.