ABSTRACT
Laser-induced breakdown spectroscopy (LIBS) is a well-established technique for elemental analysis and has been widely used for qualitative and quantitative analysis of different solid samples. LIBS is also well-known for not requiring sample preparation, but the analysis of liquids is actually a great challenge. In the present work, a novel approach of elemental analysis of liquids with an organic matrix has been performed, to the best of our knowledge, making a liquid-to-solid matrix conversion by drying wine samples on aluminum and silicon wafers, which have demonstrated an increase in the analytical performance of LIBS. A red wine from Slovakia (not blended with any other variety or wine from other regions or adulterants) was prepared according to the procedure consisting of drying 2 ml of wine dropped on a solid wafer having a flat surface area of about 25 cm2. Surface-assisted LIBS in combination with the conversion of liquid into solid avoids the difficulties and limitations of working with liquid samples by LIBS, improving the limit of detection (LOD), repeatability, and sensitivity. The quantification of strontium (Sr) has been realized by addition of the known concentration of SrCl2·6H2O in wine before the drying process. Sr is an important element among those usually used as markers for identification of the soils on which the vines grow. Two ionic (407.771 nm and 421.552 nm) and two neutral (460.733 nm and 481.188 nm) Sr lines were used to plot the calibration curves in order to study the LODs and the matrix effects for the analysis of Sr in the tested wines and for different wafer materials. This direct surface-assisted LIBS measuring method has been successfully applied for the determination of Sr in a red wine sample from Slovakia, and the obtained results with two kinds of substrates (Al and Si) were compared. Finally, a validation sample has been employed to test the accuracy of the established calibration curves.
ABSTRACT
Paleoclimate studies play a crucial role in understanding past and future climates and their environmental impacts. Current methodologies for performing highly sensitive elemental analysis at micrometre spatial resolutions are restricted to the use of complex and/or not easily applied techniques, such as synchrotron radiation X-ray fluorescence micro-analysis (µ-SRXRF), nano secondary ion mass spectrometry (nano-SIMS) or laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Moreover, the analysis of large samples (>few cm²) with any of these methods remains very challenging due to their relatively low acquisition speed (~1-10 Hz), and because they must be operated in vacuum or controlled atmosphere. In this work, we proposed an imaging methodology based on laser-induced breakdown spectroscopy, to perform fast multi-elemental scanning of large geological samples with high performance in terms of sensitivity (ppm-level), lateral resolution (up to 10 µm) and operating speed (100 Hz). This method was successfully applied to obtain the first megapixel images of large geological samples and yielded new information, not accessible using other techniques. These results open a new perspective into the use of laser spectroscopy in a variety of geochemical applications.
