SPECTROCHIMICA ACTA

PART B

ELSEVIER Spectrochimica Acta Part B 52 (1997) 1923-1927

An expert system program for ICP-AES system diagnosis 1

Christine Sartoros a, Jean-Franqois Alary a, Eric D. Salin a'*, Jean-Michel Mermet b

aDepartment of Chemistry, McGill Universio,. Montreal H3A 2K6, Quebec. Canada bLaboratoire des Sciences Analytiques, UniversitO Claude Bernard-Lyon L Lyon. France

Received 28 January 1997; accepted I 1 July 1997

Abstract

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by two diskettes containing the installation program for the application. The main article discusses the purpose of this work and the Appendix provides instructions on the use of the program. ICP-AES performance can be followed by monitoring a series of atomic lines. QUID Expert is a Windows based program which uses line intensities from a standard solution in conjunction with a series of rules to determine when an ICP-AES is degrading and where the probable fault lies. The software provides other features such as a logbook and automatic recording to allow users to monitor system performance over extended times. In the tradition of modern expert systems, QUID Expert provides guidance as to what possible fault(s) might be present in the system and recommends remedial action(s). © 1997 Elsevier Science B.V.

Keywords: Expert system; ICP-AES; Diagnostics

1. I n t r o d u c t i o n

Inductively coupled plasma atomic emission spectrometer (ICP-AES) systems have been exten- sively automated and are handling many samples for extensive periods while often being run by inex-

perienced operators. The software included with these instruments provides basic information about the instrument such as plasma on/off, loss of gas

pressure, or communication failure between computer and instrument. These systems require a diagnostic

* Author to whom correspondence should be addressed. t This article is an electronic publication in Spectrochimica Acta

Electronica (SAE), the electronic section of Spectrochimica Acta Part B. The accompanying diskettes are identified as 'QUID Expert', Spectrochimica Acta Electronica B, E00 (1997). Readers of this journal are permitted to copy the contents of the diskettes for their personal use under the conditions stated under 'Copyright and Disclaimer' at the end of this article, and, generally, in the 'Instruc- tions for Authors', published elsewhere in this issue.

program which would inform the operator of instru- ment malfunctions such as nebulizer blockage, poor energy transfer, or instrumental drift. Mermet and

his colleagues have devised a sequence of steps which monitors system performance and identifies many malfunctions [1]. This sequence of steps can be considered as a number of simple tests performed in a specific order. A standard test solution consisting of 5 ppm of barium, magnesium and zinc, is used to perform several tests. Seven atomic and ionic lines are monitored including several argon lines. The diagnosis of the components of the ICP system is enabled by using the information extracted from

the measurements of a line profile, absolute line intensities, relative standard deviations (RSD) of intensities, signal-to-background ratios (SBRs), and ionic to atomic line intensity ratios. These tests are useful since each one examines a specific compo- nent of the system. The major components of the

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1924 C. Sartoros et al./Spectrochimica Acta Part B 52 (1997) 1923 1927

ICP system examined are: (i) the generator (energy transfer); (ii) the sample introduction system (nebuli- zer efficiency and precision); (iii) the optics (disper- sive and collimating systems); (iv) stability of the instrument. The tests are easy to perform although the interpretation of the data may be difficult for an inexperienced operator. To overcome this problem, we have written a diagnostic application called QUID Expert, based on the knowledge presented in several of Mermet 's papers [1]. The system was designed specifically for a sequential scanning spec- trometer but could run on less flexible systems using an appropriate selection of lines.

2. Design considerations

The first version of this diagnostic application, QUID Expert, was written in AI Corporation's First Class expert system shell and ran under DOS.

With the increasing popularity of Windows TM and the arrival of Windows 95 TM, it became apparent that the graphical user interface provided by Windows TM

would be more effective. The latest version can be implemented to run concurrently with most existing vendors' WindowsfM-based software.

This version of the program uses sequential tests with data being manually entered by the user, which is best tbr illustration and educational purposes; however, a future version of the program would ideally read the data from a database (or file), run all the tests simultaneously and give the results. At the top level, there is a simple color code interface which provides the results of the tests performed by assigning a color to the status of the test (e.g., green is a normal state, yellow is a warning state, etc.) and providing a message as a brief explanation of the outcome (Fig. 1). To evaluate the performance of the tests (dispersion, collimation, energy, nebulizer efficiency, and nebulizer precision) previous values

Setup Report MalnMenu ~lndmv F.~lltProgram Help

Test Status Message

F1 ~ HELP

Fig. 1. On-screen display of the Test Menu window. Individual tests are accessed by the buttons on the left hand side of the window (under the heading 'Test'). The results of these tests are displayed on the right hand side (under the heading 'Message').

c. Sartoros et al./Spectrochimica Acta Part B 52 (1997) 1923-1927 1925

for a test are retrieved from the database and their average and standard deviation are calculated. This is historical information provided during previous runs of the software or during setup. For our example database all of the data sets have been arranged with a mean of about 100 and a standard deviation of 10. The number of historical (database) values used in the calculation can be set by the user in the program. When running each of the tests, the program deter- mines if the new value exceeds the thresholds (see Appendix, Section A.4, for a brief explanation on thresholds) and returns the outcome as to the status of the test and an explanation on possible faults (where applicable). The above tests provide a basic set of diagnostics for monitoring the health of an ICP-AES instrument. Clearly, other tests are possible. Buttons for additional tests of short term nebulizer precision and long term instrumental stability are included in this menu, but are not implemented in this basic version of the software.

The program provides both a graphical history of the instrument performance as well as expert advice that is usually quite specific as to the cause of any problem. Other features of the program include the ability to view the data in the database in tabular format or graphically (see Section A.3. for a brief explanation of the View menu command) and the ability to maintain a logbook. The logbook provides the user with a place to view the results and take down notes relevant to the experiment. It resembles a regular notebook and it is divided into six sections: dispersion, collimation, energy, nebulizer, drift, and general information. The logbook can be searched based on date and time, or can be viewed sequentially.

3. Conclusions

We believe that QUID Expert provides the first major step in the development of an 'expert' diagnosis system. Ideally a QUID-like system will directly interface with a manufacturer's database, and we are now looking into this; however, it is usable in the form in which we have provided it. We are working on other types of 'expert' software [2] which will recog- nize problematic samples as well as forms that will use pattern recognition techniques to recognize samples [3]. We encourage interested users to contact

us with recommendations or comments. We would be pleased to have people contact us if they would be interested in more advanced versions, perhaps manufacturer-specific variants. If there is sufficient interest we would consider working through a world wide web site.

Appendix A

Appendix A. 1 Technical information

The program was written in Microsoft ® Visual Basic v.3.0 for Windows TM 3.0 (or later) and is provided in compiled form. The program works on IBM compatible personal computers (80386 or higher microprocessor) and will run on a CGA, EGA, VGA, 8514, Hercules, or other display compatible with Windows TM. It requires 1 MB of memory and a mouse. The program is stored in compressed form on two diskettes (1.44 MB).

Appendix A.2 Diskette contents

(1) Readme.txt is a text file which explains how to get started and how to contact the authors for technical information.

(2) The user should start up Windows and then from the File menu item, Run should be selected. Using the Browse button go to the floppy drive (e.g., a:), select the Setup file (i.e., Setup.exe) and run it. The user should then follow the instructions on the screen. At the end of the installation two warning messages may appear. We did not heed the warnings when we did the installation and the program still ran well.

The following files are required for the application to be run under WindowsTM:

cmdialog.vbx graph.vbx grid.vbx msmasked.vbx threed.vbx commdlg.dll delay.dll gswdll.dll msajt 110.dll

1926 C. Sartoros et al./Spectrochimica Acta Part B 52 (1997) 1923-1927

msaes110.dll vbdb300.dll vbrun300.dll gsw.exe

The following files are the databases used by QUID. They are Microsoft ® Access TM compatible:

logbook.mdb record2.mdb recorder.ldb recorder.mdb

The last file, quidhelp.hlp, is the help file for QUID in the Windows TM format.

Appendix A.3 Getting started

The Setup program has created an icon for QUID. To run QUID, simply double click on the icon. The introductory animated screen will appear and the user should select the Continue button. The main menu will then be encountered. Below is a list of the main menu options, along with a brief explanation of each.

(a) Reset. Reset permits the user to reset the data- base to its original form. All information in the database is lost after this operation.

(b) View. The user can view the values in the data- base using this option. There are two ways that the values can be viewed. The first method presents the values listed in a grid and multiple test results can be viewed at the same time. These values can also be printed. The second method presents data graphically, however only the results of a single test can be viewed at one time.

(c) Test Sequence. This is the main menu option and accesses the major component of the application in which all the tests may be performed.

(d) Logbook. This feature provides the user with an area to write down notes. Data is also stored auto- matically in the Logbook. (Details can be found in Appendix A.5.

(e) Instrument. This option has not been implemen- ted in this version. It allows the System Manager to alter critical settings in QUID such as the password for turning off the recorder, or setting the frequency at which the tests should be performed.

(f) Quit. Exits the application.

(g) Help. This option accesses the help file for QUID which is in the standard Windows help format. This file contains a table of contents along with search capabilities. This file can also be accessed by pressing the FI key. Depending on where the user is in the application when the F1 key was pressed, the user will be linked to the most related help topic or the table of contents.

Appendix A.4 Option 'test sequence' and its submenu

Selection of 'Test Sequence' causes a submenu to appear. The new window represents the coordinating screen for all the available tests. Below is a list of the menu and button options, along with a brief explanation.

(a) Setup. Allows the user to set various parameters for performing the tests.

(i) Points. This option permits the user to set the number of points retrieved from the database in order to perform the tests. The default number of points is set to 20. (ii) Thresholds. This option allows the user to choose which values should be used for warning thresholds in the expert system. These thresholds are stored (if the user chooses) for all future tests. The thresholds are set as a certain number of standard deviations above or below the average value for a test. There are two threshold values, the first is the warning value and the second is a critical warning value. The default thresholds are 1 and 2 standard deviations from the average.

(b) Report. This permits the user to have a report of the results from the tests performed.

(i) Save. This will save the conclusions of the tests in ASCII format. The user will be prompted for a filename. The ASCII format is very general and can be used by all word processors. (ii) Print. This will print the conclusions of the tests along with graphs.

(c) Main Menu. This option allows the user to return to the Main Menu.

(d) Window. This option permits the user to open the logbook and have it open while performing the tests. This allows the user to take notes at any time.

(e) Exit Program. Exits the program.

C. Sartoros et aL/Spectrochimica Acta Part B 52 (1997) 1923-1927 1927

(f) Help. Same as Help in the Main Menu. Buttons in Tests window. (g) Dispersion UV. This evaluates the performance

of the dispersive system in the ultraviolet region of the spectrum.

(h) Dispersion VIS. This evaluates the performance of the dispersive system in the visible region of the spectrum.

(i) Energy. This evaluates the energy transfer from the generator to the plasma, and the energy transfer from the plasma to the sample.

(j) Collimation. This evaluates the performance of the collimating system.

(k) Neb. efficiency. This evaluates the nebulizer's efficiency.

(1) Neb. precision. This evaluates the nebulizer's precision. Under development.

(m) Drift. This evaluates the stability of the instrument's performance. Under development. Note that Mermet [ 1 ] has described how this should be done.

Appendix A.5 Option 'logbook'

When this option is selected, a picture of a

notebook is displayed on the screen. Each page is devoted to a test and is divided into two sections. The top section displays the results of the test performed and this section cannot be altered. The bottom section is where the user can write down any notes. The last page is devoted to any general information the user wishes to write down. The logbook has its own database and therefore entries should be saved after they have been entered. The entries are saved along with the date and time. The database can be searched using the date and time as search keys or can be looked through entry by entry.

References

[11 E. Poussel, J.M. Mermet, Spectrochim. Acta, 48B(67) (1993) 743, and references therein.

[2] Wayne Branagh, Ciara Whelan, Eric D. Salin, A system for automatic selection of operating conditions for ICP-AES, submitted to J. Anal. At. Spectrom.

[3] Sartoros, Eric D. Salin, Pattern recognition for sample classification using elemental composition--application for ICP-AES, submitted to J. Anal. At. Spectrom.