Miniaturized extraction techniques are well established in analytical protocols following the guidelines of green chemistry. In spite of this, analytical chemistry researchers continue to look for alternatives and modifications that minimize or solve problems associated with the application of microextraction techniques. This manuscript goes over the most significant advances proposed from mid-2016 to the end of 2018. Thus, different possibilities are reported to minimize the major shortcoming of each modality of liquid-phase microextraction (LPME). The necessity of reducing extraction time and the toxicity of solvents used, and also enhancing the selectivity and precision of these methods has increased the possibilities and applications of LPME.

Optimum conditions for flotation-spectrophotometric determination of iron with 4-(2-pyridylazo)resorcinol (PAR) based on a 1:2 FeII-PAR complex were found to be as follows: flotation solvent (chloroform), shaking time (2 min), pH (4.5±0.5), concentration of PAR (2.0×10–4 mol L–1), reducing agent (hydroxylamine hydrochloride), solvent for the floated compound (dimethylsulphoxide, DMSO), wavelength for spectrophotometric measurements (718 nm), and volumes of the organic solvents (5 mL of chloroform and 3 mL of DMSO). Calibration graphs were compared for different volumes of the aqueous phase – 10 mL and 40 mL; the corresponding linear ranges were 0.30–1.3 mg mL–1 and 0.25–1.0 mg mL–1. The iron content was successfully determined in soil samples, reference standard materials (PS-1, COOMET No. 0001-1999 BG, SОD No. 310а-98; PS-2, COOMET No. 0002-1999 BG, SOD No. 311а-98; and PS-3, COOMET No. 0003-1999 BG, SOD No. 312а-98) and zinc sulfide concentrates

For the first time an optical probe is proposed as the microdrop holder and simultaneously the measuring cell in a direct immersion single-drop microextraction (DI-SDME) procedure. This approach enables the analytical signal (absorbance of organic phase) to be monitored and recorded online during the extraction process. Based on the suggested approach, a novel on-probe DI-SDME method for the determination of thiocyanate ions using the extraction of the ion pair formed between SCN⁻ and Astra Phloxine reagent in acidic medium into 40 µL of amyl acetate is suggested. The final experimental conditions were found to be: the pH of the aqueous phase being 3, the stirring rate at 500 rpm, a 150 s extraction time, the absorption maximum at 555 nm and 700 nm as the reference wavelength. The calibration plot was linear in the range of 0.29–4.35 mg L⁻¹ of SCN⁻, with a correlation coefficient of 0.9981. The limit of detection (LOD) was found to be 0.12 mg L⁻¹. The method was applied for analysis of human saliva samples. Furthermore, the possibility of using the optical probe not only for DI-SDME but also for liquid–liquid–liquid microextraction (LLLME) and reverse mode microextraction techniques is shown in separate experiments.