Combination of online hollow fiber liquid phase microextraction with smartphone-based sensing for in situ formaldehyde assay in fabric and wastewater samples.

A miniaturized analytical methodology was introduced based on the combination of a direct and online hollow fiber microextraction method with smartphone color detection. The method was used for the determination of formaldehyde (target analyte) in fabric and wastewater samples. In this regard, two reagents including ammonium acetate buffer and acetylacetone were added to the formaldehyde samples to create a colored compound. The colored compound was extracted from the sample by using the hollow fiber liquid-phase microextraction method, the extracted phase was not taken out of the extraction box and was directly transferred into a specially designed detection cell, and a smartphone was applied for in-situ color sensing and data readout. This combination gathered the advantages of both state-of-the-art microextraction techniques and smartphone sensing. Formaldehyde, as a carcinogenic compound widely used in paint and clothing industries, was selected as a model test. Factors affecting extraction efficiency were investigated and optimized, including the type of organic solvents, reagent concentration, salt, pH, stirring speed, reaction temperature, and extraction time. The linear region of the method under optimal conditions was 40-1500 µg L-1 for wastewater samples and 0.3-11.2 mg kg-1 for fabrics. The limit of detection and limit of qualification were 13 and 40 µg L-1, respectively. The relative standard deviations for concentrations of 100 and 1000 µg L-1 were 6% and 4%, respectively. To evaluate the application of the method for real samples, types of fabric and two samples of oil refinery wastewater were selected. The relative recovery in real samples was 84-98%. The results of the analytical parameters of the method show that the developed method can be used as an efficient method to determine formaldehyde in real samples.

Preparation of kapa carrageenan-based acidic heterogeneous catalyst for conversion of sugars to high-value added materials.

A novel composite based on kappa-Carrageenan (κC) was prepared using N,N-methylene bisacrylamide (MBA) as the crosslinking agent. 5-Hydroxymethylfurfural (5-HMF) was produced by catalytic dehydration of fructose and glucose with MBA grafted κC (κC-g-MBA) as the solid acid catalyst due to sulfonic acid groups in biopolymer skeletons. Various reaction parameters such as optimization of the quantity of the catalyst, temperature, reaction time, and solvent were performed. It was established that for fructose dehydration, the best reaction conditions were the 160 °C as the optimized reaction temperature and 1 h reaction time, respectively. Under these conditions, the HMF yield and fructose conversion were 94.2% and 95.5%, respectively. Furthermore, 160 °C and 2 h were the best reaction temperature and reaction time for glucose dehydration, respectively. Under similar conditions, the HMF yield and glucose conversion are 47% and 93%, respectively. The catalyst was readily prepared from inexpensive materials with considerable reusability and reactivity.

Combination of paper-based thin film microextraction with smartphone-based sensing for sulfite assay in food samples.

Herein, a simple, green, and novel paper-based headspace-thin film microextraction in combination with smartphone-based on-cell detection was introduced. Sulfite was selected as a model compound to study the performance of the method. The method was based on converting sulfite to SO2 by acidification of the sample solution. A piece of cellulose paper impregnated with Fe(III), 1,10-phenanthroline, and acetate buffer (pH = 5.5) was used for headspace-thin film microextraction. The sulfur dioxide adsorbed on the thin film reduced Fe(III) to Fe(II). The red color complex formed between Fe(II) and 1,10-phenanthroline was on-cell detected by a smartphone. The effect of various parameters on the method sensitivity was investigated. The method had three individual linear ranges (0.1-1.0, 1-50, and 50-700 µg L-1) with a detection limit of 0.04 µg L-1. The method provided a simple and green assay for the determination of sulfite in food samples. Recoveries were higher than 94% with the relative standard deviations lower than 4.8%. Expensive and complicated facilities were not required in the method.

Covalent triazine-based framework for micro solid-phase extraction of parabens.

Herein, nano-sized covalent triazine-based framework grafted magnetic particles were synthesized by a facile Friedel-Crafts reaction between cyanuric chloride as node and biphenyl as linker. The formation of the material has been confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission-scanning electron microscopy, thermogravimetric analysis, and N2 adsorption-desorption measurement. With respect to the material structure, the large number of aromatic rings in the molecular framework provided a bed for extracting aromatic ring-containing compounds through π-π stacking interactions. The applicability of the prepared material as a new sorbent for micro solid-phase extraction of parabens was investigated. The effect of key experimental parameters affecting the extraction efficiency of the analytes including sorbent amount, sample pH, extraction time and desorption conditions were investigated. High-performance liquid chromatography with UV detection was used for determining the enriched analytes. The method was successfully applied for determining parabens in human urine, breast milk, personal care products, and shower wastewater. After optimization, the linearity range of 0.1-500 µg L-1 and detection limit of 0.02 µg L-1 were obtained for all the selected parabens. The relative standard deviations and recoveries for the real sample analysis were in the range of 2.3-5.0% and 86-102%, respectively.

Environmentally-friendly and ultrasonic-assisted preparation of two-dimensional ultrathin Ni/Co-NO3 layered double hydroxide nanosheet for micro solid-phase extraction of phenolic acids from fruit juices.

In this paper, we report an environmentally-friendly and low cost synthetic approach for large-scale fabrication of 2-dimentional porous Ni/Co-NO3-based layered double hydroxide (Ni/Co-NO3-LDH) nanosheet through ultrasonic-assisted process. The synthesis procedure used ethylene glycol/water system as an eco-friendly solvent system. The synthesized LDH was characterized by FE-SEM, TEM, XRD, and FT-IR techniques. FE-SEM and TEM images showed porous structure surface morphology of the synthesized LDH. Also, For Ni/Co-NO3-LDH, a hexagonal ultrathin layered was obtained owing to ultrasonic irradiation and applied processing conditions. The prepared LDH was used as sorbent in dispersive micro solid-phase extraction procedure. Two phenolic acids including p-hydroxybenzoic acid and p-coumaric acid were selected as model compounds. Some experimental factors affecting the extraction efficiency of the analytes were investigated and optimized. Finally, the sorbent was used for the extraction of model compound from fruit juice samples followed by high performance liquid chromatography. Linear dynamic range of 0.5-500µgL-1 with a low detection limit (0.1µgL-1) was obtained by the method. The relative standard deviations were 2.5 and 4.3% for p-hydroxybenzoic acid and p-coumaric acid, respectively. All recoveries were between 82 and 92%.

Metal-organic aerogel as a coating for solid-phase microextraction.

An iron-based metal-organic aerogel was synthesized using metal-organic framework nanoparticles and applied as a fiber coating for solid-phase microextraction (SPME). Chemical, thermal and morphological characteristics of the material were investigated. Headspace SPME followed by gas chromatography-electron capture detection was used for the determination of chlorobenzenes in the environmental samples. The key experimental factors affecting the extraction efficiency of the analytes, such as ionic strength, extraction and desorption temperature, and extraction time were investigated and optimized. The applicability of the coating for the extraction of chlorobenzenes from the environmental samples including river and tap water, sludge, and coastal soil was evaluated. The detection limits were in the range of 0.1-60 ng L-1. The relative standard deviations were between 2.0 and 5.0%. The extraction recovery of the analytes was in the range of 88-100%. Compared to the commercial PDMS fiber, the present fiber showed better extraction efficiency.