In the first study, a magnesium–aluminum layered double hydroxide coated on magnetic nanoparticles was synthesized and used as a sorbent to extract some selected phenolic acids. After extraction, the elution step was performed through dissolving double hydroxide layers containing the analytes by changing the solution pH. The linearity range of the method was between 2 and 500 µg L ?1 . Relative standard deviations for intra- and inter-day precision were in the range of 4.3–9.2% and 4.9–8.6%, respectively. The limits of detection were between 0.4 and 1.3 µg L ?1 . In the second study, a method based on the combination of hollow fiber liquid–liquid–liquid microextraction and solid-phase microextraction (SPME) followed by gas chromatography-electron capture detection was developed for the determination of chlorophenols. The precision of the method for the analytes at 0.02–30 µg L ?1 concentration level ranged from 7.1 to 10.2% (as intra-day relative standard deviation) and 6.4 to 9.8% (as inter-day relative standard deviation). The linear dynamic ranges were in the interval of 5–500 µg L ?1 , 0.05–5 µg L ?1 , 0.02–1 µg L ?1 and 0.001–0.5 µg L ?1 for 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol, respectively. The enrichment factors were between 432 and 785. The limits of detection were in the range of 0. 4 – 1200.0 ng L ?1 . In the third study, a new headspace liquid-phase microextraction technique based on using a copper foam nanostructure substrate followed by gas chromatography-flame ionization detection was developed for the determination of volatile organic compounds. Under the optimum conditions, the method detection limit was between 0.06 and 0.25 ?g L -1 . The relative standard deviation of the method for the analytes at 4-8 ?g L -1 concentration level ranged from 7.9 to 11 %. The enrichment factor was in the range of 615-744. In the fourth study, a simple, rapid, sensitive and cost-effective sample pretreatment technique was developed for the extraction and determination of methadone in human body fluid and hair samples. Methadone was extracted from the sample to the organic solvent immobilized in the pores of the prepared stir bar. Under the optimized conditions, the limit of detection (LOD) was 0.01 µg L -1 . Relative standard deviation of the method for the analyte at 1 µg L -1 was 7.5 % (as intra-day RSD) and 9.1% (as inter-day RSD). The enrichment factor (EF) was 425. The linear dynamic range (LDR) was in the range of 0.1-200 µg L -1 . In the fifth study, we present a simple, rapid and low cost strategy for the preparation of robust stir bar coatings based on the combination of montmorillonite with epoxy resin. The coated stir bar was implemented in a novel automated multisyringe stir bar sorptive extraction system. Under the optimum conditions, the detection limits were between 0.02 and 0.34 µg L ?1 . The relative standard deviations (RSD) of the method ranged from 3.5% to 4.1% (as intra-day RSD) and from 3.9% to 4.3% (as inter-day RSD). The enrichment factors were between 30 and 49. In the sixth study, thin layered double hydroxide (LDH) disks were in situ fabricated on the Al 2 O 3 /PVDF substrate by means of urea hydrolysis process and used as automated thin film microextraction method using a sequential injection analysis system. Under the optimized conditions, the detection limits were between 0.12-0.25 µg L -1 . Relative standard deviations ranged from 2.9%-4.2% and the linear dynamic ranges (LDRs) were in the range of 0.5-500 µg L -1 . In the final study, the use of metal-organic framework (MOF) mixed-matrix disks (MMD) for the automated flow-through solid-phase extraction (SPE) of environmental pollutants was reported. Detection limits ranged from 0.04 to 0.18 ?g L ?1 . Relative standard deviations ranged from 3.9 to 5.3% intra-day, and 4.7 to 5.7% inter-day. Membrane batch-to-batch reproducibility was from 5.2 to 6.4%.