Comparison of intra-day and inter-day variation in LIBS spectra

- Additive log-ratio transformation (ALR) should be used for LIBS data.
- Variation in LIBS data collected on same day or different days is not different.
- ALR transformed LIBS data may be used to create a database for forensic purposes.
- LIBS may be a reliable instrument and may be used for forensic purposes in future.

Laser Induced Breakdown Spectroscopy (LIBS) is an analytical chemistry technique that has the potential to identify and measure the elements in a substance of interest. LIBS is applicable for any phase (solid, liquid or gas). LIBS has gained importance in the fields of material identification, biomedical science, forensics, military, art and archaeology in the recent years. In spite of its many advantages over other instruments, it has a few drawbacks such as poor precision and repeatability. That is, different spectra may be observed for the same sample over successive runs. This indicates poor precision of the instrument.This paper presents an experiment designed to investigate the claim that there is higher variation in the experiments conducted on different days as compared to the experiments conducted on the same day. This study examines the variability in the spectra between the runs on the same day, and the variability between runs on different days using samples from a standard reference glass, and discusses the conclusions that can be drawn from the results.