A comparative assessment of ion pair sediment cloud point extraction and ultrasound-assisted dispersive magnetic solid phase extraction for Methyl Violet dye with environmental assessment metrics

This study compared two different single-step extraction methods (IPS-CPE and UA-d-MSPE) using environmental assessment tools (BAGI, MoGAPI, SPMS, AGREE and CACI) for the efficient determination and preconcentration of Methyl Violet dye. The first method, the IPS-CPE method, used the formation of ion pair (Methyl Violet-SDS) between the cationic dye and anionic Sodium Dodecyl Sulfate (SDS). This ion pair is less soluble in water and can aggregate using Triton X-114 as a non-ionic surfactant into a highly solidified, viscous, and allowing for facile separation by decantation. The second method, UA-d-MSPE method utilises a reusable porous MWCNT/Fe3O4 nanocomposite adsorbent. The MWCNT/Fe3O4 was characterised XRD, EDX and FESEM, both before and after adsorption of Methyl Violet dye. The UA-d-MSPE method worked under reasonable conditions (35°C and 15 min in an ultrasonic bath) and utilises ethanol as the only eluent, with external magnetic field for separation and adsorbent recovery. A UV-Visible spectrophotometric method was validated for Methyl Violet quantification, covering ranges of 0.1–1 mg.L−1 for IPS-CPE and 0.2–2 mg.L−1 for UA-d-MSPE. Both methods exhibited excellent linearity (R2 = 0.999), high accuracy (99.925 ± 3.469% for IPS-CPE and 99.661 ± 2.956% for UA-d-MSPE) and low RSDs (3.471% for IPS-CPE and 2.966% for UA-d-MSPE). For IPS-CPE, the LOD and LOQ were 0.034 mg.L−1 and 0.097 mg.L−1, respectively. For UA-d-MSPE, the LOD and LOQ were 0.042 mg.L−1 and 0.176 mg.L−1. Both methods showed a good sensitivity, with preconcentration factors (PF) of 20 and enhancement factors (EF) of 15.36 for IPS-CPE, and PF of 40 and EF of 10.56 for UA-d-MSPE. This work presents a comparative assessment of two single-step extraction mechanisms using environmental assessments metrics. The application of higher scores from BAGI, MoGAPI, SPMS, AGREE, and CACI tools confirmed that UA-d-MSPE can be considered a greener chemistry method than IPS-CPE. This is due to UA-d-MSPE's advantages, such as its simple process, reduced solvent consumption (only ethanol), recyclability of the porous MWCNT/Fe3O4 extractant, lower energy and time requirements, and minimal environmental effect.