Elemental mapping of cocoa beans with laser-induced breakdown spectroscopy

Area of Science:

• Analytical Chemistry
• Food Science
• Materials Science

Background:

• Cocoa beans are a vital food source, rich in essential minerals and trace elements.
• Traditional methods like ICP-MS and AAS quantify elements but lack spatial distribution data.
• X-ray fluorescence with micrometer resolution (µXRF) offers elemental mapping but can be time-consuming.

Purpose of the Study:

• To evaluate the capabilities and limitations of laser-induced breakdown spectroscopy (LIBS) for elemental distribution imaging in cocoa beans.
• To compare LIBS imaging with µXRF for elemental mapping in cocoa beans.
• To assess LIBS as a rapid, low-sample-preparation technique for the cocoa sector.

Main Methods:

• Laser-induced breakdown spectroscopy (LIBS) was used to image elemental distribution in cocoa beans.
• Experimental parameters and data preprocessing were optimized to minimize sample melting and ensure resolution.
• A carbon-based normalization method was employed to correct for variations in laser ablation.
• µXRF was used for side-by-side comparison on the same samples.

Main Results:

• LIBS successfully mapped mineral and trace element distribution in cocoa beans within 90 minutes.
• LIBS elemental images showed similar results to µXRF, with slightly lower resolution.
• The study identified variations in elemental distribution within individual cocoa beans using LIBS.
• A carbon normalization method proved effective in rectifying experimental variations.

Conclusions:

• LIBS is a capable technique for mapping elemental distribution in cocoa beans, offering speed and minimal sample preparation.
• LIBS presents a viable alternative or complementary method to µXRF for elemental analysis in the cocoa industry.
• The multi-elemental analysis, speed, and ease of use make LIBS a promising tool for cocoa quality assessment.