A hydrophobic deep eutectic solvent based vortex-assisted liquid-liquid microextraction for the determination of formaldehyde from biological and indoor air samples by high performance liquid chromatography.

Hydrophobic deep eutectic solvents (DESs) are a new class of green solvents, and their research and application are a brand new area. So far, only a few hydrophobic DESs have been reported as extraction solvents. In this paper, five kinds of hydrophobic DESs composed of trioctylmethylammonium chloride and hydroquinone, 4-phenylphenol or 4-cyanophenol are designed and prepared for the first time. Melting point / glass transition temperature and density are also determined for these DESs. Coupled with HPLC, these hydrophobic DESs have been used as extractants in vortex-assisted liquid-liquid microextraction for the selective enrichment and indirect determination of formaldehyde. The optimization of reaction and extraction conditions, such as pH value, reaction time and temperature, concentration of 2,4-dinitrophenylhydrazine, type and dosage of the extraction solvent, speed and time of vortex, salt addition and centrifugation time are investigated in detail. It is found that under the optimized experimental conditions, the calibration curve of this method is linear in the range of 1.0-200.0 μg L-1 with the linear correlation coefficient (r2) of 0.9994. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) are 0.2 μg L-1 and 1.0 μg L-1, and the intra-day and inter-day precision (RSD, n = 5) are 1.1% and 3.5%, respectively. The interference of some common coexisting ions and neutral molecules have been also tested. The proposed method has been successfully used for the determination of formaldehyde from biological and indoor air samples. The recovery of formaldehyde is in the range from 83.1% to 104.4%, and the relative standard deviation is lower than 5.9%. Furthermore, the analytical parameters of the proposed method have been compared with other extraction and microextraction methods.

Zhang K ，Liu C ，Li S ，Fan J ... -  《-》

A hydrophobic deep eutectic solvent-based vortex-assisted dispersive liquid-liquid microextraction combined with HPLC for the determination of nitrite in water and biological samples.

In recent years, hydrophobic deep eutectic solvents as new generation of green solvents have attracted wide attention in liquid microextraction technique. In this article, four hydrophobic deep eutectic solvents composed of trioctylmethylammonium chloride and oleic acid were designed and prepared firstly. Combined with high-performance liquid chromatography, these deep eutectic solvents were used as an extraction solvent in vortex-assisted dispersive liquid-liquid microextraction for the selective enrichment and indirect determination of trace nitrite from real water and biological samples. This method is based on the diazotization-coupling reaction of nitrite with p-nitroaniline and diphenylamine in acidic water, and then the nitrite is quantified indirectly by measuring the obtained azo compounds. Some factors influencing the extraction efficiency, including the reaction and extraction conditions, were investigated. Under the optimized conditions, the method has a linear range of 1-300 μg/L with a correlation coefficient of 0.9924, limit of detection of 0.2 μg/L, limit of quantitation of 1 μg/L, intraday and interday relative standard deviations of 4.0 and 6.0%. This method was successfully applied in determination of nitrite from three environmental water and two biological samples with the recovery in the range of 90.5-115.2%. In addition, these results were well agreement with those obtained by the conventional Griess method.

Zhang K ，Li S ，Liu C ，Wang Q ，Wang Y ，Fan J ... -  《-》

Determination of some red dyes in food samples using a hydrophobic deep eutectic solvent-based vortex assisted dispersive liquid-liquid microextraction coupled with high performance liquid chromatography.

Faraji M 《-》

Hydrophobic deep eutectic solvents as extractants for the determination of bisphenols from food-contacted plastics by high performance liquid chromatography with fluorescence detection.

As a new kind of green solvents for potential replacement of traditional volatile organic compounds, deep eutectic solvents (DESs) have been attracting more and more attention in various applications. In this work, three types of hydrophobic DESs were synthesized by simple mixing of trioctylmethyl ammonium chloride (used as hydrogen bond acceptor) with decanoic acid, ketoprofen and gemfibrozil (hydrogen bond donors), respectively, at different molar ratios. In order to evaluate the solvent characteristics of these DESs, some of the physical properties such as melting point, density, viscosity, and water contact angle were determined. Then, these hydrophobic DESs were used for the vortex-assisted liquid-liquid microextraction of bisphenol-type contaminants in water, followed by quantitative determination of bisphenols contents with high performance liquid chromatography (HPLC-FLD) coupled with fluorescence detection. For this purpose, four bisphenols, namely, 2, 2-bis(4-hydroxydiphenyl)propane (BPA), 2, 2-bis (4-hydroxyphenyl)butane (BPB), 4, 4'-(1-phenylethylidene)bisphenol (BPAP) and 4, 4'-cyclohexylidenebisphenol (BPZ) were selected as model contaminants. It was found that the enrichment factors of the proposed method were in the range from 97 to 112, depending on the structure of the analytes. Under optimal experimental conditions, the linearity ranges of the method varied from 0.3 to 700 µg L-1 with linear correlation coefficients (R2) higher than 0.996. The limit of detections (LODs) and limit of quantifications (LOQs) were in the range of 0.3-0.5 µg L-1 and 0.06-0.08 µg L-1, respectively. Furthermore, the developed method was successfully used in the extraction and determination of four bisphenols from food-contacted plastic samples.

Li T ，Song Y ，Dong Z ，Shi Y ，Fan J ... -  《-》

Air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent for the analysis of ultraviolet filters in water samples by high performance liquid chromatography with the aid of response surface methodology.

For this work, a novel air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent (AA-LLME-SFDES), coupled with a high performance liquid chromatography (HPLC) method was developed for the detection of benzophenone and salicylate ultraviolet filters in water samples. Three types of fatty acid-based hydrophobic deep eutectic solvents (DESs) with low viscosity, low-density, and melting point close to room temperature were prepared and employed as extraction solvents. This air-assisted liquid-liquid microextraction was carried out in a glass centrifuge tube. Subsequently, the glass tube was introduced into ice-water bath and held for 3 min, during which the upper DES phase was solidified. The water phase was easily extracted using a syringe equipped with a long needle, and later, the glass tube was removed from ice-water bath. The solidified DES phase was immediately melted at room temperature and used for HPLC analysis. The response surface methodology was employed to optimize some influencing parameters such as the volume of the extraction solvent, the pH value of sample solution, the number of extraction cycles, and the addition of salt. A quadratic model, namely a central composite design, was used to replace the conventional single factor analysis. It was found that under optimal conditions, the limits of determination and quantification were 0.045-0.54 µg L-1 and 0.15-2.0 µg L-1, respectively. The relative standard deviations for inter-day (n = 5) and intra-day (n = 5) precision were ≤ 4.2%, whereas the enrichment factors for the ultraviolet filters were obtained from 41 to 50. Furthermore, this novel method was successfully employed for the detection of benzophenone and salicylate ultraviolet filters from real water samples. The recoveries ranged from 87.5% to 105.8%, whereas the RSDs were lower than 3.6%.

Zhang K ，Li S ，Wang Y ，Fan J ，Zhu G ... -  《-》