A high-throughput approach for the determination of pesticide residues in cucumber samples using solid-phase microextraction on 96-well plate

A high-throughput solid-phase microextraction (SPME) on 96-well plate together with gas chromatography–mass spectrometry (GC–MS) was developed for the determination of some selected pesticides in cucumber samples. Pieces with the length of 1.0 cm of silicon tubing were precisely prepared and then coated on the end part of stainless steel wires. The prepared fibers were positioned in a home-made polytetrafluoroethylene (PTFE)-based constructed ninety-six holes block to have the possibility of simultaneous immersion of the SPME fibers into the center of individual wells. Pesticides such as diazinon, penconazol, tebuconazol, bitertanol, malathion, phosalone and chlorpyrifos-methyl were selected for their highly application in cucumber field. The performances of the SPME fibers, such as intra and inter-fibers reproducibility, were evaluated and the results showed a good similarity in extraction yields. A volume of 1 mL of the aquatic supernatant of the cucumber samples was transferred into the 96-well plate and the array of SPME fibers was applied for the extraction of the selected pesticides. The important parameters influencing the whole extraction process including, organic solvent percent, salt addition, dilution factor, stirring rate and extraction time were optimized. The inter- and intra-day RSD% were found to be less than 15.4%. Limits of detection (LOD) and limits of quantification (LOQ) were below 60 and 180 μg kg⁻¹, respectively. The coefficient of determination was satisfactory (r² > 0.99) for all the studied analytes. The developed method was successfully applied to the monitoring of several samples gathered from local markets.     

Accurate quantification of endogenous androgenic steroids in cattle's meat by gas chromatography mass spectrometry using a surrogate analyte approach

Determination of endogenous steroids in complex matrices such as cattle's meat is a challenging task. Since endogenous steroids always exist in animal tissues, no analyte-free matrices for constructing the standard calibration line will be available, which is crucial for accurate quantification specially at trace level. Although some methods have been proposed to solve the problem, none has offered a complete solution. To this aim, a new quantification strategy was developed in this study, which is named “surrogate analyte approach” and is based on using isotope-labeled standards instead of natural form of endogenous steroids for preparing the calibration line. In comparison with the other methods, which are currently in use for the quantitation of endogenous steroids, this approach provides improved simplicity and speed for analysis on a routine basis. The accuracy of this method is better than other methods at low concentration and comparable to the standard addition at medium and high concentrations. The method was also found to be valid according to the ICH criteria for bioanalytical methods. The developed method could be a promising approach in the field of compounds residue analysis.     

An effort toward molecular biology of food deprivation induced food hoarding in gonadectomized NMRI mouse model: focus on neural oxidative status

Background

Environmental uncertainty, such as food deprivation, may alter internal milieu of nervous system through various mechanisms. In combination with circumstances of stress or aging, high consumption of unsaturated fatty acids and oxygen can make neural tissues sensitive to oxidative stress (OS). For adult rats, diminished level of gonadal steroid hormones accelerates OS and may result in special behavioral manifestations. This study was aimed to partially answer the question whether OS mediates trade-off between food hoarding and food intake (fat hoarding) in environmental uncertainty (e.g., fluctuations in food resource) within gonadectomized mouse model in the presence of food deprivation-induced food hoarding behavior.

Results

Hoarding behavior was not uniformly expressed in all male mice that exposed to food deprivation. Extended phenotypes including hoarder and non-hoarder mice stored higher and lower amounts of food respectively as compared to that of low-hoarder mice (normal phenotype) after food deprivation. Results showed that neural oxidative status was not changed in the presence of hoarding behavior in gonadectomized mice regardless of tissue type, however, glutathione levels of brain tissues were increased in the presence of hoarding behavior. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde in brain tissues of gonadectomized mice were also seen.

Conclusions

Although, food deprivation-induced hoarding behavior is a strategic response to food shortage in mice, it did not induce the same amount of hoarding across all colony mates. Hoarding behavior, in this case, is a response to the environmental uncertainty of food shortage, therefore is not an abnormal behavior. Hoarding behavior induced neural OS with regard to an increase in brain glutathione levels but failed to show other markers of neural OS. Decreased superoxide dismutase activity in brain and spinal cord tissues and increased malondialdehyde levels in brain tissues of gonadectomized mice could be a hallmark of debilitated antioxidative defense and more lipid peroxidation due to reduced amount of gonadal steroid hormones during aging.

     

Neuromorphic Liquids,Colloids, and Gels: A Review

Advances in flexible electronic devices and robotic software require that sensors and controllers be virtually devoid of traditional electronic components, be deformable and stretch-resistant. Liquid electronic devices that mimic biological synapses would make an ideal core component for flexible liquid circuits. This is due to their unbeatable features such as flexibility, reconfiguration, fault tolerance. To mimic synaptic functions in fluids we need to imitate dynamics and complexity similar to those that occurring in living systems. Mimicking ionic movements are considered as the simplest platform for implementation of neuromorphic in material computing systems. We overview a series of experimental laboratory prototypes where neuromorphic systems are implemented in liquids, colloids and gels.     

Identification of compounds that bind mitochondrial F1F0 ATPase by screening a triazine library for correction of albinism

A triazine-based combinatorial library of small molecules was screened in albino murine melanocytes to identify compounds that induce pigmentation. Six compounds (of 1536 screened) produced at least 3-fold increases in pigmentation. Immunohistochemical studies demonstrated that the compounds conferred correct routing of the mistrafficked enzyme tyrosinase, which is critical to normal melanogenesis. Affinity matrices of the immobilized compounds allowed the cellular target to be identified as the mitochondrial F1F0-ATP synthase. Oligomycin and aurovertin B, small molecules known to inhibit the mitochondrial ATP synthase, were shown to compete with the triazine-based compounds for their cellular target in albino melanocytes and confer similar effects on pigmentation and tyrosinase rerouting. This is the first demonstration of the mitochondrial ATP synthase as a potential therapeutic target for restoring pigmentation in albino melanocytes.     

Pressurized fluid extraction of essential oil from Lavandula hybrida using a modified supercritical fluid extractor and a central composite design for optimization

Essential oil components were extracted from lavandin (Lavandula hybrida) flowers using pressurized fluid extraction. A central composite design was used to optimize the effective extraction variables. The chemical composition of extracted samples was analyzed by a gas chromatograph-flame ionization detector column. For achieving 100% extraction yield, the temperature, pressure, extraction time, and the solvent flow rate were adjusted at 90.6°C, 63 bar, 30.4 min, and 0.2 mL/min, respectively. The results showed that pressurized fluid extraction is a practical technique for separation of constituents such as 1,8-cineole (8.1%), linalool (34.1%), linalyl acetate (30.5%), and camphor (7.3%) from lavandin to be applied in the food, fragrance, pharmaceutical, and natural biocides industries.     

Simultaneous determination of trichloroethylene,perchloroethylene and trichloroacetic acid in human urine using solid-phase microextraction fibre coated with single-walled carbon nanotubes

A reliable and sensitive method for simultaneous determination of perchloroethylene (PCE), trichloroethylene (TCE), and trichloroacetic acid (TCA) in human urine by gas chromatography-mass spectrometry (GC/MS) is described after extraction and preconcentration by a new solid-phase microextraction (SPME) adsorbent. The potential of single-walled carbon nanotubes (SWCNTs) as SPME adsorbent for the pre-concentration of environmental pollutants has been investigated in recent years. This work was carried out to investigate the feasibility of SWCNTs as a headspace SPME adsorbent for the determination of chloroethylenes in human urine. SWCNTs were attached onto a stainless steel wire through an organic binder. Potential factors affecting the extraction efficiency, including extraction time, extraction temperature, desorption time, desorption temperature, and salinity were optimized. The developed method showed good performance. For PCE and TCE, calibration curves were linear (r ^{2 ?}≥?0.994) over the concentration ranges from 15 to 8000?ng?L^?1 and the limit of detection (LOD) at signal-to-noise (S/N) ratio of 3 was 5?ng?L^?1. The analytical procedure also involves derivatization of TCA with dimethyl sulfate, before headspace sampling. For TCA the linear range and LOD were 45-8000 (r ^{2 ?}≥?0.992) and 15?ng L^?1, respectively. In addition, a comparative study between the SWCNT and a commercial carboxen/polydimethylsiloxane (CAR/PDMS) SPME fibre for the determination of chloroethylenes in human urine was carried out. SWCNT fibre showed higher extraction capacity, better thermal stability (over 350°C) and longer life span (over 200 times) than the commercial CAR/PDMS fibre. The developed method was successfully applied to determine chloroethylenes in human urine samples. As the results indicated, the mean concentrations of TCE, PCE and TCA in exposed workers (dry-cleaning industry workers) were significantly greater than that of control group.     

Isomerization of Keggin Al13 Ions Followed by Diffusion Rates

The solution chemistry of aluminum has long interested scientists due to its relevance to materials chemistry and geochemistry. The dynamic behavior of large aluminum–oxo‐hydroxo clusters, specifically [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺ ( Al₁₃ ), is the focus of this paper. ²⁷Al NMR, ¹H NMR, and ¹H DOSY techniques were used to follow the isomerization of the ?‐Al₁₃ in the presence of glycine and Ca²⁺ at 90 °C. Although the conversion of ?‐Al₁₃ to new clusters and/or Baker–Figgis–Keggin isomers has been studied previously, new ¹H NMR and ¹H DOSY analyses provided information about the role of glycine, the ligated intermediates, and the mechanism of isomerization. New ¹H NMR data suggest that glycine plays a critical role in the isomerization. Surprisingly, glycine does not bind to Al₃₀ clusters, which were previously proposed as an intermediate in the isomerization. Additionally, a highly symmetric tetrahedral signal (δ=72 ppm) appeared during the isomerization process, which evidence suggests corresponds to the long‐sought α‐Al₁₃ isomer in solution.     

An investigation of matched index of refraction technique and its application in optical measurements of fluid flow

Optical distortions caused by non-uniformities of the refractive index within the measurement volume is a major impediment for all laser diagnostic imaging techniques applied in experimental fluid dynamic studies. Matching the refractive indices of the working fluid and the test section walls and interfaces provides an effective solution to this problem. The experimental set-ups designed to be used along with laser imaging techniques are typically constructed of transparent solid materials. In this investigation, different types of aqueous salt solutions and various organic fluids are studied for refractive index matching with acrylic and fused quartz, which are commonly used in construction of the test sections. One aqueous CaCl₂·2H₂O solution (63 % by weight) and two organic fluids, Dibutyl Phthalate and P-Cymene, are suggested for refractive index matching with fused quartz and acrylic, respectively. Moreover, the temperature dependence of the refractive indices of these fluids is investigated, and the Thermooptic Constant is calculated for each fluid. Finally, the fluid viscosity for different shear rates is measured as a function of temperature and is applied to characterize the physical behavior of the proposed fluids.     

A simple and reliable stir bar sorptive extraction-liquid chromatography procedure for the determination of chlorpromazine and trifluoperazine in human serum using experimental design methodology

A sensitive and reproducible stir bar sorptive extraction and HPLC-UV detection method was used for the therapeutic drug monitoring of chlorpromazine and trifluoperazine in human serum. The separation was achieved using a C(18) column. The mobile phase consisted of methanol/sodium acetate buffer (pH 4.1; 0.1 M) (95:5, v/v) including 0.5% triethylamine. This miniaturized method can result in faster analysis, lower solvent consumption and less workload per sample while maintaining or even improving sensitivity. In the second part, stir bar sorptive extraction/HPLC-UV method was optimized by a chemometrics approach. An experimental design was therefore used to evaluate the statistically influential and/or interacting factors, among those described in the literature, and to find the best extraction and desorption conditions. Optimal sample volume of 1 mL, extraction time of 24 min at 31°C with pH 8.1 were obtained in a screening 2(5) half fractional factorial design followed by a Box-Behnken design. For the desorption conditions, a Box-Behnken design showed that the best conditions were 150 μL mobile phase for 20 min at 50°C. The optimized method was repeatable (CV<10%, linear (LOQ-500 ng/mL)), with the LOQs equal to 0.7 and 1.5 ng/mL for chlorpromazine and trifluoperazine, respectively.