In this study, we evaluated the preparation and utilization of NH2-MIL-101(Al) and NH2-MIL-101(Cr) as two efficient adsorbents for the extraction of metronidazole and cephalexin in water samples using the syringe filter-SPE method. The synthesized MOF was placed inside a syringe filter to extract the target antibiotics from the water solution following their quantification by high-performance liquid chromatography (HPLC). Various characterization methods such as SEM, FTIR, XRD, TGA, and BET were used to assess and confirm the synthesis of the studied MOFs. The comparison of the adsorption capability of the synthesized MOFs revealed that NH2-MIL-101(Al) had the greatest adsorption capability. The experimental factors affecting the extraction efficiency such as sample volume and pH, and the type and volume of the adsorption solvent were thoroughly studied and optimized. Under the optimal conditions, the detection limits were calculated to be in the range of 0.5 to 10.0 μg L−1, and a linear range between 2.0 and 800 μg L−1 was obtained. Very good repeatability with RSD values ranging between 3.2% and 5.3% was achieved. The calculated relative recovery ranged from 95% to 104% at the spiked levels of 60–150.0 μg L−1.

In this work, for the first time, low-density organic solvents were employed in continuous sample drop flow microextraction (CSDF-ME) by changing the design of extraction vessel. To examine the effectiveness of the modified extraction method, different organophosphorus pesticides (OPPs) were extracted using proposed method followed by detection by gas chromatography–mass spectrometry (GC–MS). In fact, unlike conventional CSDF approach, in this study, we applied halogen-free organic solvents that are lighter than water for analytes extractions. These solvents are not only less toxic but also more environmentally friendly compared to the halogenated solvents. A conical open-end vial fixed in a small container filled with double-distilled water was used as the extraction vessel. A small amount of extraction solvent was placed at the bottom of the vial and the sample solution was pumped into the extraction vessel through a needle located inside the vial using a peristaltic pump. The sample droplets were continuously passed through the extraction solvent (hexane; 13 μL) to extract the analytes. Once the extraction was completed, the extraction solvent left at the top of aqueous phase was collected and injected into the GC–MS for further analysis. Under optimized conditions, the repeatability of the proposed method was found to be in range of 3.9–5.8 % for samples with low concentration of 5.0 μg L−1. The LOD (limit of detection) and LOQ (limit of quantification) of the method were determined in the ranges of 0.02−0.30 and 0.07–1.0 μg L−1, respectively. The EF (enrichment factor) was found to be between 510 and 960 for 8.0 mL sample solutions. The proposed method allows an extraction recovery ranging between 25.5 % and 48.0 %.

A simple, precise and sensitive analytical method, which is a combination of modified ultrasound-assisted extraction (UAE), continuous sample drop flow microextraction (CSDF-ME) and GC–MS, was developed for the extraction and determination of organophosphorus pesticides in fruit and vegetable samples. In this study, for the first time, a very small amount of organic solvent was used for the UAE, almost three times less than conventional UAE. To this end, first, the raw vegetables and fruits were finely chopped and mashed. Then, 0.8 mL of acetonitrile was added and the entire mixture was sonicated for 20 min. Afterward, in order to remove acetonitrile from the mixture and to reduce the amount of organic solvent 6.0 mL of ultra-pure water was added to the mixture, and the aqueous phase was filtered out. Next, the extracted analytes were concentrated by pumping the aqueous phase across a few microliters of organic solvent (chloroform) placed inside the bottom of a conical vial at a flow rate of 0.45 mL min−1. Finally, the extracted analytes were transferred into the GC–MS for further detection. Under the optimum conditions, the relative recovery ranged from 83.0% to 108.0%. The repeatability of the method was examined at two concentration levels (60.0 and 120.0 ng g−1), and it was obtained between 4.0 and 7.6%, and 3.2 and 6.2%, respectively (n = 5). Finally, the LOD and LOQ were found to be 0.2–20.0 ng g−1, and 1.0–60.0 ng g−1, respectively.

In this paper, the technique of continuous sample drop flow microextraction (CSDF-ME) is developed by the addition of a narrow-necked conical vessel. In the developed technique, an organic solvent denser than water is used for the extraction of organophosphorus pesticides (OPPs) from fruit juice and river water, followed by analysis with GC-MS. Eight milliliters of the sample solution is pumped at 0.5 mL min−1 flow rate into 12.0 μL extraction solvent (chloroform) and placed in the narrow-necked conical vessel for extraction and pre-concentration processes. Under optimal condition, the enrichment factor (EF) and linearity are found to be in the range of 102–380 and 500.0 μg L−1 with correlation coefficient greater than 0.98, respectively. The detection limit is in the range of 0.3–1.0 μg L−1 and LOQ ranged from 2.0–5.0 μg L−1. The relative standard division (RSD) of six replicate measurements for three different concentrations (i.e., 15.0, 50.0, 150.0 μg L−1) is 3.8–8.4%, 2.6–6.0%, and 2.2–4.8%, respectively. Values of RSD% of the target pesticides at 50.0 μg L−1 concentration levels are less than 6.0%.

In this study, the imine‐graphene hybrid material (HM) was used as an adsorbent for the removal of Fe(III) and Cr(III) metal ions from the drinking waters. The adsorbent material (HM) was prepared at three steps. At the first step, the graphite was oxidized by Hummer's method for preparation of graphene oxide (GO), in the second step, the silanization derivative (GO‐APTES) was obtained from the reaction of the 3‐(trimethoxysilyl) propylamine and GO. In the final step, the hybrid material (HM) was synthesized from the reaction of the 3,5‐diiodosalicylaldehyde and GO‐APTES. The chemical structures of three materials GO, GO‐APTES and HB were characterized by using the FT‐IR, XRD, EDX, SEM, TEM and UV‐vis methods. Thermal properties of the materials GO, GO‐APTES and HB were investigated by TGA/DTA methods in the 25–1000°C temperature range. Adsorption and desorption studies of the hybrid material toward Fe(III) and Cr(III) metal ions were investigated using the Batch method. The effect of pH, contact time, temperature, concentration on the adsorption properties of the hybrid material were investigated by ICP‐OES. The Fe(III) and Cr(III) ions have the maximum adsorption at the pH 7. The adsorption capacity decreases with the increase in pH values because above pH 9 the adsorption decreases due to the precipitation of metal hydroxide.