A three‐phase solvent extraction system combined with deep eutectic solvent‐based dispersive liquid–liquid microextraction for extraction of some organochlorine pesticides in cocoa samples prior to gas chromatography with electron capture detection

A sample pretreatment method based on the combination of a three‐phase solvent extraction system and deep eutectic solvent‐based dispersive liquid–liquid microextraction has been introduced for the extraction of four organochlorine pesticides in cocoa samples before their determination by gas chromatography‐electron capture detection. A mixture of sodium chloride, acetonitrile, and potassium hydroxide solution is added to cocoa bean or powder. After vortexing and centrifugation of the mixture, the collected upper phase (acetonitrile) is removed and mixed with a few microliters of N,N‐diethanol ammonium chloride: pivalic acid deep eutectic solvent. Then it is rapidly injected into deionized water and a cloudy solution is obtained. Under optimum conditions, the limits of detection and quantification were found to be 0.011‐0.031 and 0.036‐0.104 ng/g, respectively. The obtained extraction recoveries varied between 74 and 92%. Also, intra‐ (n = 6) and interday (n = 4) precisions were less than or equal to 7.1% for the studied pesticides at a concentration of 0.3 ng/g of each analyte. The suggested method was applied to determine the studied organochlorine pesticide residues in various cocoa powders and beans gathered from groceries in Tabriz city (Iran) and aldrin and dichlobenil were found in some of them.     

Development of a stir bar sorptive extraction method coupled to solidification of floating droplets dispersive liquid–liquid microextraction based on deep eutectic solvents for the extraction of acidic pesticides from tomato samples

A stir bar sorptive extraction method coupled with deep eutectic solvent based solidification of floating organic droplets–dispersive liquid–liquid microextraction has been used for the simultaneous derivatization and extraction of some acidic pesticides in tomato samples. In this method, initially the analytes are adsorbed on a coated stir bar from tomato juice filled in a narrow tube. After extraction, the stir bar is removed and a water–miscible deep eutectic solvent is used to elute the analytes. Afterward, a derivatization agent and a water–immiscible deep eutectic solvent (as an extraction solvent) with melting point near to room temperature are added to the obtained eluant at µL–levels and the obtained mixture is rapidly injected into deionized water. Under the optimum conditions, the introduced method indicated high enhancement (1543–3353) and enrichment (2530–2999) factors, low limits of detection (7–14 ng/L) and quantification (23–47 ng/L), good linearity (r² ≥ 0.9982), and satisfactory repeatabilities (relative standard deviation ≤12% for intra– and inter–day precisions at a concentration of 100 ng/L of each analyte). Finally, the proposed method was applied in analysis of the analytes in tomato samples.     

Determination of personal care products in water using UHPLC–MS after solid phase extraction with mesoporous silica‐based MCM‐41 functionalized with cyanopropyl groups

A silica‐based MCM‐41 mesoporous material functionalized with cyanopropyl groups has been synthesized by cocondensation, characterized and applied to preconcentrate six parabens and three UV filters in river and swimming‐pool waters. The analytes were quantified by ultra‐high performance liquid chromatography‐tandem mass spectrometry, according to the Directive 96/23/EC. Even though matrix effect was negligible, quantification in river water samples with the standard addition approach improved the recoveries obtained using solvent‐based and even with matrix‐matched calibration. The method quantification limits in river water samples were 0.05 ng/mL for 2,4‐dihydroxybenzophenone and 0.01 ng/mL for the rest. Recoveries, evaluated for a concentration level of 0.5 ng/L, were in the range 93.5‐107.6% for parabens and in the range 64.2‐85.8% for UV filters, with relative standard deviations intraday ≤10.2 and 10.8%, respectively. This parameter, evaluated for a concentration level of 0.1 ng/L, ranged between 98.3 and 110.4% for parabens and between 61.9 and 89.9% for UV filters, with relative standard deviation intraday ≤15.3 and 15.5%, respectively. The two UV filters with lower recoveries were the most affected by the addition of sodium chloride. River and swimming pool waters were analyzed and all the personal care products were found in the swimming pool water, whereas only methylparaben was detected in the river water.     

Effect of polymerization of synthetic glycolipids on their supramolecular assemblies

Sugar-derived surfactants bearing a polymerizable acryloyl moiety on one of the branches of the double-chain hydrophobic tail were prepared. The non–ionic hydrophilic head and the biantennary hydrophobic tail were built on, respectively, an aspartic acid and a tris(hydroxymethyl)aminomethane core. Ultraviolet irradiation of aqueous dispersions of these surfactants above their transition phase temperature (T_c) was achieved. The morphology of self-assemblies produced in such a way were investigated by transmission electron microscopy. TEM photographs revealed that irradiation leads to the formation of unilamellar vesicles. Neither fibers nor tubules were detected in contrast to what was observed before polymerization.     

Reactions of p-quinone monoimines with lawesson reagent and phosphorus pentasulfide

2, 4-Bis-(4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfide [Lawesson reagent (LR)] 1 reacts with p-quinone monoimine- 2a to give the novel benzo-1,3,2-oxathiaphosphol-5-(methanesulfonamido)-2-(4-methoxyphenyl)-2-sulfide 4 . On the other hand, the reaction of 2b and 3 with LR 1 leads to the formation of the benzo- and the naphtho-1,3,2-dithiaphosphol-5 -(benzenesulfonamido)- 2- (4-methoxyphenyl) -2-sulfide 5 , 6 . Thiation of 2a , 2b , and 3 with P₄S₁₀ yields phenoxathiin derivatives 8a , 8b , and 9 , respectively. The identity of the new products is established from analytical and spectroscopic evidence.     

Synthesis and crystal structure of a new lithium cyclohexaphosphate hydrate: Li6P6O18·10H2O

The synthesis and crystal structure of a novel hydrate of lithium cyclohexaphosphate are reported. Li₆P₆O₁₈·10H₂O crystallizes in the space group C2/c with a = 15.113(5), b = 12.006(2), c = 15.892(2) Å, = 122.85(2)°, and Z = 4. The structure consists of P₆O₁₈ ring layers stacked along the c direction in between which are located the lithiumions and water molecules. Two LiO₄ tetrahedra share common edges with LiO₅ pseudosquare pyramids to form two independant Li₃O₉ units. About 50% of the water molecules have fractional occupancy rates and form fragments of molecules. A linear relationship is established between the relative cell volume V/Z and the hydration degree, n, for all the known hydrates: Li₆P₆O₁₈·nH₂O.     

Design and development of a fiber-optic immunosensor utilizing near-infrared fluorophores

The design and application of a fluorescent fiber-optic immunosensor (FFOI) are reported. The FFOI is utilized for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region. The technique is developed through the combined use of fiber-optic, semiconductor laser-excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize an antibody sandwich technique. The assay involves the immobilization of the capture antibody on the sensing tip of the FFOI followed by the exposure of the immobilized sensing tip to the antigen. The antigen-coated FFOI is then introduced to a second antibody previously labeled with the NIR dye. Typical measurements are performed in about 15 min. A semiconductor laser provides the excitation (780 nm) of the immune complex. The resulting emission is detected by a silicon photodiode detector (820 nm). The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. The sensitivity of the analysis reaches 10 ng/ml and the response time is 10–15 min.