A new fast, sensitive, and environmentally friendly analytical method has been developed for the simultaneous determination of Ba, Be, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in wastewater samples using inductively coupled plasma optical emission spectroscopy (ICP OES). A preconcentration step using a magnetic dispersive solid-phase extraction (MDSPE) technique with a new magnetic sorbent was performed. The new sorbent material was a carbon containing magnetic cobalt and nitrogen groups. This material was synthetized using controlled pyrolysis of a zeolitic imidazolate framework (i.e., ZIF-67). In order to optimize the experimental parameters that affect the MDSPE procedure, a multivariate optimization strategy, using Plackett–Burman and circumscribed central composite designs (CCD), was used. The method has been evaluated employing optimized experimental conditions (i.e., sample weight, 10 g; sample pH, 7.6; amount of sorbent, 10 mg; dispersive agent, vortex; complexing agent concentration, 0.5%; ionic concentration, 0%; eluent, HCl; eluent concentration, 0.5 M; eluent volume, 300 μL; elution time, 3 min and extraction time, 3 min) using external calibration. Limits of detection (LODs) in a range from 0.073 to 1.3 μg L⁻¹ were obtained, and the repeatability was evaluated at two different levels, resulting in relative standard deviations below 8% for both levels (n = 5). An increase in the sensitivity was observed due to the high enrichment factors (i.e., 3.2 to 13) obtained compared with direct ICP OES analysis. The method was also validated through carrying out recovery studies that employed a real wastewater sample and through the analysis of a certified reference material (ERM^®-CA713). The recovery values obtained with the real wastewater were between 94 and 108% and between 90 and 109% for the analysis of ERM^®-CA713, showing negligible matrix effects.

In this work, the surface nature‐dependent behaviors of magnetic deep eutectic solvents (MDESs) and magnetic low‐transition‐temperature non‐volatile mixtures (MLTTMs) are reported for the first time. It has been observed that the surface of the material where the MDES or the MLTTM is placed could considerably affect the dispersion and the magnetic and structural properties of these magnetic mixtures. Different techniques and analyses have been carried out to highlight the differences observed in the properties depending on the material on which these magnetic mixtures are placed. To that end, differential scanning calorimetry (DSC), surface tension, contact angle and scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX) measurements have been performed. As a result, it has been shown that the MDESs or MLTTMs are retained and adhered to glass surfaces, resulting in a loss of magnetism of the mixture in addition to a loss in the performance of synthesis carried out on the closeness of glass materials as the interaction between the glass and the mixture modify the composition and therefore the properties. As a preliminary result, when using these magnetic mixtures as extractant solvents in dispersive liquid‐liquid microextraction, the MDES or MLTTM is retained on the walls of the glass tubes reducing the extraction efficiency, repeatability and the extraction recovery using an external magnetic field. For all these reasons, polypropylene materials should be recommended when handling magnetic deep eutectic solvents and non‐volatile MLTTMs.

A new multinebulizer is combined/associated with an on-line standard dilution analysis for wear metal determination in lubricating oils by MP AES.

In the present work, a simple, fast, sensitive and accurate method was developed to determine Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn in essential oil samples at trace levels by inductively coupled plasma optical emission spectrometry (ICP OES). Vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) was employed to preconcentrate the analytes, with a hydrophilic magnetic eutectic mixture (MEM) acting as the extractant. The MEM used was a mixture of ethylene glycol (EG) and CoCl₂ in a molar ratio of 2:1. The optimal extraction conditions, sample amount, MEM volume and extraction time were determined through two-stage multivariate analysis: the first stage consisted of a 2³ full factorial design, and the second stage was a central composite design. The optimal extraction conditions obtained were: 7.0 g of diluted sample amount, 150 μL of MEM, and 1 min of extraction time. Under these extraction conditions, the analytical method (VA-DLLME/ICP OES) was validated and demonstrated linearity in the range of 10-500 μg kg^-1, excellent precision (RSD ≤7%) and limits of detection in the range of 0.04-1 μg kg^-1. The method accuracy was assessed using a matrix certified reference material (MCRM). Finally, the proposed method was successfully applied to analyze three commercial essential oil samples (eucalyptus, lavender, and tea tree).