In analytical chemistry, the Limit of Detection (LoD) is a widely accepted metric used to evaluate the performance of a chemical measurement process. Informally, the LoD represents the lowest concentration of an analyte that can be detected with a reasonably high degree of confidence. According to the conventional definition by IUPAC the LoD is determined as the signal level equal to the mean of the blank plus 3.3 times the standard deviation of the blank measurement.
However, in two-dimensional (2D) imaging data, signals with concentrations below this traditional 3.3σ threshold are often still visually discernible, in contrast to their detection in one-dimensional (1D) data settings. This discrepancy highlights the unique capability of visual perception in interpreting spatial data. A useful analogy to this is found in the field of visual perception theory, specifically the concept of the "Just Noticeable Difference" (JND), which refers to the smallest detectable difference between two stimuli that the human senses can perceive.
In this work, we explore the application of the JND concept to 2D mapping experiments to better predict and assess the visually perceivable concentrations in elemental maps. This approach provides a novel framework for improving the interpretation of detection limits in 2D data. It allows for the recognition of subtle signals that might not meet traditional LoD criteria but are nonetheless detectable due to their spatial context in imaging.
This methodology is particularly applicable to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Laser-Induced Breakdown Spectroscopy (LIBS) and other imaging/mapping techniques like. By incorporating principles of human visual perception, we offer a refined approach to understanding detection in 2D datasets, enhancing sensitivity and offering insights into signal interpretation across a variety of elemental imaging applications. The potential for this approach could lead to more accurate assessments of trace elements and better utilization of spatial information inherent in mapping techniques.