Fast determination of Ziziphora tenuior L. essential oil by inorganic–organic hybrid material based on ZnO nanoparticles anchored to a composite made from polythiophene and hexagonally ordered silica

In this paper, for the first time, an inorganic–organic hybrid material based on ZnO nanoparticles was anchored to a composite made from polythiophene and hexagonally ordered silica (ZnO/PT/SBA-15) for use in solid-phase fibre microextraction (SPME) of medicinal plants. A homemade SPME apparatus was used for the extraction of volatile components of Ziziphora tenuior L. A simplex method was used for optimisation of five different parameters affecting the efficiency of the extraction. The main constituents extracted by ZnO/PT/SBA-15 and PDMS fibres and hydrodistillation (HD) methods, respectively, included pulegone (51.25%, 53.64% and 56.68%), limonene (6.73%, 6.58% and 8.3%), caryophyllene oxide (5.33%, 4.31% and 4.53%) and 1,8-cineole (4.21%, 3.31% and 3.18%). In comparison with the HD method, the proposed technique could equally monitor almost all the components of the sample, in an easier way, in a shorter time and requiring a much lower amount of the sample.     

Anodized aluminum wire as a solid-phase microextraction fiber for rapid determination of volatile constituents in medicinal plant

Headspace solid phase microextraction using anodized aluminum fiber in combination with capillary GC–MS was utilized as monitoring technique for the collection and detection of the volatile compounds of Echinophora platyloba DC. Experimental parameters, including the sample weight, extraction temperature, extraction time and humidity effect, desorption time and desorption temperature were examined and optimized. Using HS-SPME followed by GC–MS, 53 compounds were separated and identified in E. platyloba DC, which mainly included E-β ocimene (47.63%), R-D-decalactone (13.28%), α-pinene (7.43%) and nonane (6.71%). Compared with hydrodistillation (HD), HS-SPME, provides the advantages of a small amount of sample, timesaving, simplicity and cheapness. To the best of our knowledge, this is the first report on using anodized aluminum fiber in solid-phase microextraction coupled to headspace for the investigation of volatile fraction of medicinal plant.     

Analysis of volatile oil composition of Citrus aurantium L. by microwave‐assisted extraction coupled to headspace solid‐phase microextraction with nanoporous based fibers

Nanoporous silica was prepared and functionalized with amino propyl‐triethoxysilane to be used as a highly porous fiber‐coating material for solid‐phase microextraction (SPME). The prepared nanomaterials were immobilized onto a stainless steel wire for fabrication of the SPME fiber. The proposed fiber was evaluated for the extraction of volatile component of Citrus aurantium L. leaves. A homemade microwave‐assisted extraction followed by headspace (HS) solid‐phase apparatus was used for the extraction of volatile components. For optimization of factors affecting the extraction efficiency of the volatile compounds, a simplex optimization method was used. The repeatability for one fiber (n = 4), expressed as RSD, was between 3.1 and 8.6% and the reproducibility for five prepared fibers was between 10.1 and 14.9% for the test compounds. Using microwave‐assisted distillation HS‐SPME followed by GC‐MS, 53 compounds were separated and identified in C. aurantium L., which mainly included limonene (62.0%), linalool (7.47%), trans‐β‐Ocimene (3.47%), and caryophyllene (2.05%). In comparison to a hydrodistillation method, the proposed technique could equally monitor almost all the components of the sample, in an easier way, which was rapid and required a much lower amount of sample.     

Double-charged ionic liquid-functionalized layered double hydroxide nanomaterial as a new fiber coating for solid-phase microextraction of phenols

Double-charged diazabicyclo[2.2.2]octane (DABCO) was immobilized on the inner surface of a nanomaterial composed of the layered double hydroxides (LDHs) of Zn(II) and Cr(III). The resulting material was characterized by SEM, FT-IR and XRD techniques. This novel nanocomposite has been used as a highly porous fiber coating for solid-phase microextraction (SPME) of phenol and various chloro-, nitro- and aminophenols. The LDH nanocomposite was deposited on a stainless steel wire and then evaluated with respect to the extraction of phenolic compounds from water samples. The effects of temperature, extraction time, ionic strength, stirring rate, pH, and desorption temperature and time on the extraction were optimized. The compounds were then separated and quantified by GC-MS. Under optimum conditions, the repeatability for a single fiber (for n = 3 and expressed as the relative standard deviation) is between 2.3 and 7.2 %. The detection limits are between 0.02 and 6.3 pg mL⁻¹. The method is simple, rapid, and inexpensive. The fiber is thermally stable and its use gives high recoveries.

Double-charged diazabicyclo[2.2.2]octane (DABCO) was immobilized on the inner surface of a nanomaterial composed of the layered double hydroxides (LDHs) of Zn(II) and Cr(III). This novel nanocomposite has been used as a highly porous fiber coating for solid-phase microextraction (SPME) of phenol and various chloro-, nitro- and aminophenols.

     

Development of direct microwave desorption/gas chromatography mass spectrometry system for rapid analysis of volatile components in medicinal plants

A new direct microwave desorption–gas chromatography‐mass spectrometry method was developed for the analysis of the essential oils of medicinal plants. A homemade direct microwave desorption system was fabricated and used for the desorption of volatile components of medicinal herbs. The desorbed volatiles are transferred directly into the gas chromatography injector for analysis in a one‐step process. Approximately 0.3 g of the herb was needed for the desorption of samples in 60 s. In this study, more than 53 volatile compounds were identified and quantified for Echinophora platyloba DC as model herb sample. The results were found to be in good agreement with the conventional hydrodistillation extraction data. The described results show that direct microwave desorption is fast, simple, and easy to automate and requires only a small amount of sample. The results indicate that essential oil components valuable for varietal identification and characteristic of each variety analyzed when direct microwave desorption–gas chromatography‐mass spectrometry was used for analysis.     

Synthesis of carbon nanotube/layered double hydroxide nanocomposite as a novel fiber coating for the headspace solid‐phase microextraction of phenols from water samples

In this research, a carbon nanotube/layered double hydroxide nanocomposite was synthesized by an in situ growth route by electrostatic force. The prepared carbon nanotube/layered double hydroxide nanocomposite was successfully prepared and deposited on a stainless‐steel wire for the fabrication of the solid‐phase microextraction fiber. The fiber was evaluated for the extraction of phenolic compounds from water samples. Analytical merits of the method, under optimum conditions (extraction temperature: 75°C, extraction time: 30 min, desorption time: 2 min, desorption temperature 260°C, salt concentration: 10% w/v) are 0.01–300 ng/mL for the linear dynamic range and 0.005–0.08 for the limit of detection. In optimum conditions, the repeatability for one fiber (n = 3), expressed as relative standard deviation, was between 6.5 and 9.9% for the phenolic compounds.     

NOx photocatalytic degradation over ZnO–CdS heterostructure composite under visible light irradiation

Research on Chemical Intermediates - ZnO–CdS composites with different loadings of CdS were prepared by a simple wet chemical synthesis method for NOx degradation under visible light. The...     

Synthesis of a metal–organic framework confined in periodic mesoporous silica with enhanced hydrostability as a novel fiber coating for solid‐phase microextraction

A metal–organic framework/periodic mesoporous silica (MOF‐5@SBA‐15) hybrid material has been prepared by using SBA‐15 as a matrix. The prepared MOF‐5@SBA‐15 hybrid material was then deposited on a stainless‐steel wire to obtain the fiber for the solid‐phase microextraction of phenolic compounds. Modifications in the metal–organic framework structure have proven to improve the extraction performance of MOF/SBA‐15 hybrid materials, compared to pure MOF‐5 and SBA‐15. Optimum conditions include an extraction temperature of 75°C, a desorption temperature of 260°C, and a salt concentration of 20% w/v. The dynamic linear range and limit of detection range from 0.1–500 and from 0.01–3.12 ng/mL, respectively. The repeatability for one fiber (n = 3), expressed as relative standard deviation, is between 4.3 and 9.6%. The method offers the advantage of being simple to use, rapid, and low cost, the thermal stability of the fiber, and high relative recovery (compared to conventional methods) represent additional attractive features.