Using laser-induced breakdown spectroscopy for quantitative analysis, the researcher aims to use linear regression in finding the relationship between signal intensity and the concentration of the substance. So far, laser-induced breakdown spectroscopy is a young but promising method (shown to be effective and quick in qualitative analyses) but on the aspect of quantitative analyses, it is still somewhat semi-quantitative (that is if it's interpreted from the view of a beginner using the device) such that the relationship in between the signal intensity and concentration is found rather than directly looking for a more direct unit such as grams, milligrams, or parts per million.
Using signal intensity as a variable is somewhat difficult especially when an undergraduate interested (but not highly skilled) in the use of Laser induced breakdown spectroscopy tries to interpret data. This is because the signal intensity can be disrupted by many other factors (such as the disruption of the atmosphere of the sample towards the light path as well as the need for uniformity of the sample compositions). For heavy metal analyses (such as cadmium, lead, and chromium), what can be a good calibration curve in order to prevent false results as well as underestimation/overestimation of data? :)
This is for our study on mycoremediation of tropical white-rot fungi on heavy metal contaminated soil sites, and we're very interested and set in the use of LIBS since unlike other spectroscopic methods, it does not need to have sample preparations and other tedious solubilizations of samples; which are methods that can contaminate our samples. :)
you can increase the no of replicates for which the concentration is calculated. This can be carried out using high numbers (for example 10 repetions for ten replicates).
I agree with you that simple libs signal intensity is not enough for testing the LIBS spectrometer for unknown sample concentration determination accurately. For calibaration the matrix effect and the fixed experimental condictions are important. Hence one should calibarte the lIBS spectrometer for same matrix which means one should have some standard samples of various concnetaryions of specic elements prepared in same matrix and then laser paptrameters should be same as well. In addition, one should take the lIBS sepctar for 10 aquisitions and average such spectra to avaoid any laser power fluctuations. The best envrieonment is if one does teh LIBS under clsoed envrioenmnt like vacuum and also oen should use some refernce lines as stanadard so that one can comare the LIBS spectar with those standrad elemmnst like Sodium , Ca or K lines. However all this also depends how one has experience gained on LIBS analaysis. There are calibration free sioftwares developed recently for determination of concentartions in unknown samples.
For LIBS quantification, use an internal standard. This could be either the matrix element, or another element whose concentration is known or can be determined by another independent method. When using high purity graphite disks as the backing material for liquids analysis, C peaks can be used. See some of our publications through Google search giving my name, Arnab Sarkar, D. Alamelu from FCD, BARC as authors. All the best. Let us know if this helps. Any more questions are welcome here or to : [email protected]
From BARC, Mumbai, India
Alright. From all your answers, it seems that I might need compositions of which are the same with the compound we'll be analyzing. It also seems that I shall try 10 trials or acquisitions to test the accuracy and validity of results! For that, thank you so much, Sir Aggarwal, Sir Gondal, and Sir Alashkar!!! :)
Sir Aggarwal, sure! :) Thank you so much!!! :) If I happen to continue this thesis, I would definitely ask for your help. :) Thank you! :)
Hi,
You should also follow various criteria given in different LIBS papers, to identify the best possible internal standard. For example, the ground state and the excited state, atomic line or ionic line etc.
In light of above discussions, It is clear that only two methods are possible for getting concentration of unknown samples, First is based on calibration curve and other on is calibration free technique. For getting a good calibration curve with minimum error, one should plot a calibration curve of required element in the similar matrix samples in similar experimental condition.
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