A cartridge-based device for automated analyses of solid matrices by online sample prep-capillary LC-MS/MS

Sample preparation is an essential step focused on eliminating interfering compounds while pre-concentrating the analytes. However, its multiple steps are laborious, time-consuming, and a source of errors. Currently, automated approaches represent a promising alternative to overcome these drawbacks. Similarly, miniaturisation has been considered an ideal strategy for creating greener analytical workflows. The combination of these concepts is currently highly desired by analytical chemists. However, most automated and miniaturised sample preparation techniques are primarily concerned with liquid samples, while solids are frequently overlooked. We present an approach based on a cartridge packed with solids (soil samples) coupled with a capillary LC-MS, combining sample preparation and analytical steps into a unique platform. As a proof-of-concept, nine pesticides used in sugarcane crops were extracted and analysed by our proposed method. For optimisation, a fractional factorial design (2(5-1)) was performed with the following variables: aqueous dilution of the sample (V-1), extraction strength (V-2), matrix washing time (V-3), extraction flow (V-4), and analytical flow (V-5). After, the most influential ones (V-1, V-2, and V-3) were taken into a central composite design (2(3)) to select their best values. Under optimised conditions, the method reported linear ranges between 10 and 125 ng g(-1) with R-2 > 0.985. Accuracy and precision were in accordance with the values established by the International Council for Harmonisation (Q2(R1)). Therefore, the proposed approach was effective in extracting and analysing selected pesticides in soil samples. Also, we carried out initial qualitative tests for pesticides in honeybees to see if there is the possibility to apply our method in other solids.

Automated summary

This study presents a method that combines solid-packed cartridges and capillary LC-MS to integrate sample preparation and analytical steps. The proposed method effectively extracts and analyzes selected pesticides in soil samples, with potential applications in other solid samples. Initial qualitative tests on pesticides in honeybees were also conducted.