Automated Concentration Analysis System (ACAS)
Real-Time Calibration and Concentration AnalysisIntroduction
Many Situations require real-time calibration. ACAS features allow it to perform these real-time calibrations in connections with its sensors. The commonly used practice of pre-calibrating detectors in the laboratory before their use in the filed does not stand up to the challenge presented by the field conditions. This is because the laboratory calibrated “finger prints” can be masked and distorted by environmental matrix effects such as dust, moisture, smoke, pressure, etc. But the ACAS algorithms allow high quality calibration to be done quickly in the field or in-situ. Reliable databases with different matrix effects are extremely lacking. In the following we use sample data sets to demonstrate how to use ACAS for real-time calibration.
After completing the real time calibration, the concentration analysis can be started. The bestFiles from the concentration analysis are the files that have been selected because of their more accurate peaks. These files are used to determine the concentration of all files in their group.
Example Data Set
Groups: Each set of files within a group has
a very similar spectra
01.prn - 06.prn
07.prn - 12.prn
13.prn - 18.prn
18 raw files total
Reference Elements: Suspected elements in samples
Al, Be, Ca, Cu, Ti, Zn
Steps for Real-Time Calibration
1. Convert Raw Data
2. Analyze Converted Data
3. Preliminary Spectral Analysis
4. Select Database Files
Steps for Concentration Analysis
1. Spectral Analysis
2. Concentration Analysis
1. Convert Raw Data - To convert the raw .prn data, open the Raw Data Conversion module. Load all the files from a group and enter the highest and second highest wavelength from any selected file to configure the conversion. Left click the convert files button, and save the .dat files. This step can be skipped if ACAS has been interfaced with a sensor.
2. Analyze Converted Data - Open the Peak Identification module and load a .dat file that was just converted by the Raw Data Conversion module. Identify the peaks using the module. Pressing F5 will identify the peaks in the files, and pressing F6 will attempt to fit a line to the peak. The mouse function can be changed to add peaks if any are not identified. It can also be used to fit and refit peaks if a peak is not fitted properly. Save the file into .{d} format. Each file needs to be identified and saved into .{d} format.
3. Preliminary Spectral Analysis- Open the Spectral Analysis module and load all the .{d} files. Load the reference .asd files for the suspect elements Al, Be, Ca, Cu, Ti, and Zn. Analyze the files and save into .asd format. To help with the next step, you can optionally create an annotation graph for each file with the annotation graph module. Click on the file to make a graph of, and click the annotation graph button. This graph can be saved or printed.
4. Select Calibrated Data Files - Open the Database Viewer Module. This is used to calibrate the “best” file in each group, e.g. 6 files in 01.prn-06.prn group. The selection of the “best” file can be based on the accuracy of peak matches. If annotation graphs were made in the last step, they can be used to visually determine the best fit. A new folder called bestfiles should be created and the selected “best” file’s corresponding .{d} file in each group should be moved there. These bestfiles will be used to calibrate the database files for analysis. It takes less than 30 seconds to analyze one file. The time to determine the calibration curve used to determine the concentration of a given analyte (four files in less than two minutes).
1. Conduct Spectral Analysis - Open the Spectral Analysis module again. Load the reference .asd files Al, Be, Ca, Cu, Ti, and Zn. Load the first .{d} file from the bestFiles folder and analyze it. Save this as a .asd file. Load it again as a .asd file to use it as the reference data. Load the next bestfile, analyze it, save it, and load it as reference data for the next file. This process needs to be continued until all .{d} files have a corresponding .asd file. These files will be used as calibrated database files to determine the concentration in the next step.
2. Conduct Concentration Analysis- Open the Concentration Analysis module. Load all the .asd files in the bestFile folder. Analyze the files.
