Development of a dispersive solid-liquid miniaturized method based on eutectic solvents for the determination of emerging nitrogenous compounds in aquatic plants

The aim of this study was to develop a novel vortex-assisted solid-liquid miniaturized (VSLME) method using deep eutectic solvent (DES) as extractant phase for the quantification of emerging polycyclic aromatic nitrogen heterocycles (PANHs) to carbazole, benzocarbazole and dibenzocarbazole subclasses in samples of aquatic plant Eichhornia crassipes. Analysis was performed using gas chromatography coupled with mass spectrometry. The DES composition was selected univariately, and parameters of the proposed method, such as the number of extraction cycles, extraction time, agitation time and the type of partitioning solvent, were optimized using a full factorial design and simplex-centroid mixture design, respectively. The optimized VSLME conditions consisted of extracting 75 mg of sample with 2 mL of choline chloride:glycol (1:2) through six 1-min vortex cycles at 2800 rpm, followed by partitioning with 600 µL of toluene:cyclohexane (3:2) using 1 min of vortex agitation. Under optimized conditions, the method demonstrated adequate linearity (between 0.015 to 0.300 mg L^-1, R² ≥ 0.99), low limit of detection and quantification (45.63 - 113.53 ng g^-1 and 151.95 - 378.06 ng g^-1, respectively), satisfactory recoveries (50 - 118%), precision (intra-day and inter-day < 20%), ruggedness, and selectivity. Greenness assessment of VSLME using the analytical greenness metric for sample preparation, blue applicability grade index, and sample preparation metric of sustainability confirmed an adequate profile of greenness, applicability, and sustainability, respectively. The method application to Eichhornia crassipes samples from anthropogenically impacted areas revealed PANHs in both roots and aerial tissues, at concentrations ranging from 299.3 ng g⁻¹ for Benzo[b]/Benzo[c]carbazole to 2367 ng g⁻¹ for 1,8/2,7-dimethylcarbazole. The approach combines operational simplicity, rapidity, low cost, and environmental compatibility, highlighting its potential for routine applications in environmental monitoring.