## 1 Introduction
It is a safe and eco-friendly method that avoids the complexities associated with conventional analytical techniques like XRF, neutron activation analysis (NAA), AAS, X-ray photoelectron spectroscopy (XPS), ICP-AES, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). While these traditional methods are more precise, they are often less preferred due to the complexity of instrumentation and the demanding nature of sample preparation. The cost-efficiency, speed, and minimal waste generation of LIBS make it a compelling choice for elemental analysis. LIBS is a form of atomic emission spectroscopy [7; 8] widely acknowledged for its effectiveness in elemental analysis. LIBS uses a high-energy pulsed laser to interact with the sample surface, causing ablation and forming a high-temperature plasma. As atoms and ions in the plasma move from high to low energy states, they emit photons that provide elemental information in the resulting spectrum. Compared to conventional analytical techniques, LIBS offers numerous benefits. These include rapid analysis in real time with minimal or no sample preparation [9], capability for online, in situ, or stand-off detection, portability, non-destructiveness, remote analysis, and simultaneous multi-element detection [10]. As a result, LIBS has been widely applied across various fields such as materials science, metallurgy, jewelry analysis, cultural heritage preservation, soil and sediment studies [11], combustion processes, environmental monitoring, archeology, space exploration, biomedical research, medicine, and military applications. LIBS can analyze elements ranging from very light to heavy, and its instrumentation is cost-effective and easy to use [8; 12; 13]. These attributes have contributed to LIBS becoming a preferred choice among elemental analysis techniques, expanding its application from explosives detection to the analysis of biological materials [14]. In recent years, there has been a pressing need to improve and optimize the performance of LIBS, particularly by lowering the limit of detection (LOD) for certain elements and enhancing the signal intensity of emission lines across various applications. However, enhancing the signal can also be achieved by refining conventional LIBS systems [15]. One common criticism of LIBS is its poor signal repeatability from shot to shot, attributable to the complex interactions between the laser and sample, the transient and heterogeneous nature of plasma phenomena, and the sensitivity of the plasma to the physical and chemical characteristics of the sample and environmental conditions [16]. The presence of oxygen in the atmosphere has been observed to affect the persistence of LIBS emission lines [17]. Matrix effects pose a significant challenge in quantifying toxic elements using LIBS, an issue many reviewed studies have inadequately addressed. Typically, these studies have utilized a limited number of samples doped with varying toxic element concentrations. The authors of these studies argue that this approach is necessary to create a calibration set with a reasonable range of element concentrations, which is difficult to achieve with actual soil samples. However, this strategy has a major flaw: the calibration models are developed using samples with minimal matrix variation, which do not accurately represent actual soil conditions. Recent advancements in the LIBS technique for toxic element analysis have greatly improved signal strength and minimized matrix effects, representing significant progress in this area. Some studies have managed to minimize the matrix effect effectively. One such method involves normalization using an internal reference or background radiation. This technique employs an element with minimal variation among samples, like Fe in soil samples [18], as an internal reference. Background radiation can be evaluated by measuring the total plasma intensity [11] or examining a spectral region without peaks near the emission line of interest [1].