Analysis of paraben preservatives in cosmetic samples: Comparison of three different dynamic hollow fiber liquid-phase microextraction methods

This study focused on a comparison of three different dynamic hollow fiber-based liquid-phase microextraction (DHF-LPME) methods for extraction and preconcentration of parabens from wastewater, toothpaste, cream, and shampoo samples. The first method is two-phase DHF-LPME, in which n-octanol was used as the extraction solvent. The second is three-phase DHF-LPME, in which n-octanol and basic aqueous solution were used as the extraction solvent and acceptor phase, respectively. High-performance liquid chromatography with UV detection (HPLC-UV) was applied for determination of the parabens in both methods. The third method is a recently introduced method; three-phase DHF-LPME based on two immiscible organic solvents (n-dodecane as organic solvent and acetonitrile as an acceptor phase). The quantitative analyses were performed by the use of gas chromatography-mass spectrometry (GC-MS) after injection port derivatization. The effect of different extraction conditions (i.e., extraction solvent, pH, ionic strength, stirring rate, and dynamic and extraction times) on the extraction efficiency of the parabens was investigated and optimized. All the three procedures provide similar working parameters characterized by high repeatability (3.9-6.3 %) and good linearity (correlation coefficient ranging from 0.989 to 0.998). Results of real sample analyses obtained by these three methods were highly correlated. Although all methods provide compatible alternatives for paraben analysis, the three-phase DHF-LPME based on two immiscible organic solvents may be a more appropriate technique due to its higher extraction efficiency and thus lower limits of detection (LODs). LODs for all the parabens ranged from 0.2 to 5.0 μg L-1 using the two first methods combined with HPLC-UV. An improvement in sensitivity of several orders of magnitude was achieved using three-phase DHF-LPME based on two immiscible organic solvents followed by single-ion monitoring GC-MS analyses (0.01-0.2 μg L-1) due to compatibility of this technique with GC instrument. © 2013 Springer-Verlag

An efficient sample preparation method based on dispersive liquid�liquid microextraction associated with back extraction for trace determination of acidic pharmaceuticals

Reduction of matrix effect seems to be a great challenge for the development of a practical method in bioanalysis. In this regard, a simple and efficient DLLME procedure along with a back-extraction step (DLLME-BE) was developed for the preconcentration of four common non-steroidal anti-inflammatory drugs (NSAIDs) in various biological fluid samples. Briefly, the analytes of interest were initially transferred into the extraction solvent followed by the back-extraction into an immiscible basic methanol (as an acceptor phase) for further preconcentration and clean-up. The main purpose of the work is reducing the matrix effect and sensitive determination of target molecules in the complex matrices. Following on, the separation and determination of the analytes were carried out using GC�MS (in-port derivatization) and HPLC-DAD instrument. The influential parameters affecting the DLLME-BE method were evaluated in detail and the best extraction conditions were established. Under the optimum conditions, low method detection limits in the range of 0.1�1.0 and 0.1�6.0 µg L�1 were obtained for GC�MS and HPLC-DAD analysis, respectively. Additionally, fair intra-day precisions of 2.7�14.5 and 2.8�7.8 as well as inter-day precisions of 3.9�14.5 and 3.5�8.1 were achieved for the GC�MS and HPLC-DAD analysis, respectively. Finally, the method was successfully applied for the determination of four common NSAIDs in different biological fluid samples. © 2018 King Saud Universit

An efficient sample preparation method based on dispersive liquid�liquid microextraction associated with back extraction for trace determination of acidic pharmaceuticals

Reduction of matrix effect seems to be a great challenge for the development of a practical method in bioanalysis. In this regard, a simple and efficient DLLME procedure along with a back-extraction step (DLLME-BE) was developed for the preconcentration of four common non-steroidal anti-inflammatory drugs (NSAIDs) in various biological fluid samples. Briefly, the analytes of interest were initially transferred into the extraction solvent followed by the back-extraction into an immiscible basic methanol (as an acceptor phase) for further preconcentration and clean-up. The main purpose of the work is reducing the matrix effect and sensitive determination of target molecules in the complex matrices. Following on, the separation and determination of the analytes were carried out using GC�MS (in-port derivatization) and HPLC-DAD instrument. The influential parameters affecting the DLLME-BE method were evaluated in detail and the best extraction conditions were established. Under the optimum conditions, low method detection limits in the range of 0.1�1.0 and 0.1�6.0 µg L�1 were obtained for GC�MS and HPLC-DAD analysis, respectively. Additionally, fair intra-day precisions of 2.7�14.5 and 2.8�7.8 as well as inter-day precisions of 3.9�14.5 and 3.5�8.1 were achieved for the GC�MS and HPLC-DAD analysis, respectively. Finally, the method was successfully applied for the determination of four common NSAIDs in different biological fluid samples. © 2018 King Saud Universit

Adsorptive removal of Hg2+ from environmental water samples using thioglycerol-intercalated magnetic layered double hydroxides

Herein, the removal of Hg2+ from environmental water samples was carried out using a novel nanoadsorbent based on magnetite nanoparticles coated by a thioglycerol-intercalated layered double hydroxide. The prepared material was characterized using scanning electron microscopy equipped with an energy dispersive X-ray analyzer and Fourier transform infrared spectrometry. The effective parameters of the removal procedure were identified and optimized through the one-variable-at-a-time method. Under the optimal conditions, the removal characteristics of the synthesized adsorbent including selectivity, distribution coefficient, and loading capacity were calculated in the presence of some interfering ions. The removal efficiency of 94.98 together with the distribution coefficient of 5.00 � 105 mL g-1 and loading capacity of 480.69 mg g-1 showed the considerable capability of this novel adsorbent in the selective removal of Hg2+ from aqueous samples. To evaluate the performance of the synthesized adsorbent in the removal of Hg2+ from environmental water samples, the removal of the desired analyte was carried out using four different real samples. The removal procedures were conducted at the analyte concentration levels of 10.0 and 50.0 mg L-1 for each aqueous sample. The obtained results showed that the removal efficiency was in the range of 91.99-94.97, which confirmed the high performance of the synthesized adsorbent in the removal of Hg2+ from real samples. Furthermore, the relative standard deviation of as low as 4.18-6.17 showed the acceptable repeatability of this method. © 2020 The Royal Society of Chemistry

Online Injection-Based Hollow Fiber Liquid-Phase Microextraction�High-Performance Liquid Chromatography as a Fully Automatic Sample Processing for Phthalate Esters Analysis

Recently, a novel analytical instrument setup was reported for automatic preconcentration and determination of organic compounds in various sample matrices based on online hollow fiber liquid-phase microextraction (HF-LPME)�high-performance liquid chromatography (HPLC). In the present work, this novel instrument has been developed for extraction and determination of phthalate esters samples located in the polyethylene (PET) bottles. By using an automated syringe pump for loading supported liquid membrane (SLM) and acceptor solvents, a platform lift for moving sample vial, and a sampling loop for online injection of extract to HPLC, along with an electronic board with AVR microcontroller for storage of data and instrument programs, an automated sample preparation-HPLC analysis was developed. Optimization of extraction parameters was carried out by Box�Behnken design (BBD) which required a minimum of 29 experiments; the entire set of experiments was performed completely automatically and consecutively without any human intervention. The limits of detection (three times the S/N) ranged from 0.3 to 0.5 μg L�1. Effective preconcentration of the analytes was also achieved (between 153 and 335). The method is highly precise, with relative standard deviations varying between 5.1 and 6.4 and also accurate (recovery percentages >94.6 ). The main advantages of the developed method are high sensitivity, selectivity, and reliability of results, minimum sample manipulation, full automation, suitable extraction time, low solvent consumption, and ease of use. The applicability of the online automated HF-LPME/HPLC-UV instrument was validated for quantitative extraction and determination of phthalate esters in aqueous samples located inside the PET bottles. © 2015, Springer Science+Business Media New York

A Highly Sensitive Dispersive Microextraction Method with Magnetic Carbon Nanocomposites Coupled with Dispersive Liquid�Liquid Microextraction and Two Miscible Stripping Solvents Followed by GC�MS for Quantification of 16 PAHs in Environmental Samples

Abstract: In this work, a highly sensitive solid-phase-dispersive microextraction method was designed based on magnetic carbon nanocomposites as a magnetic solid-phase extraction sorbent coupled with dispersive liquid�liquid microextraction and two miscible stripping solvents (MSPE�DLLME) followed by gas chromatography�mass spectrometry (GC�MS) for determination of 16 polycyclic aromatic hydrocarbons (PAHs). By adopting this research methodology, a mixture of two miscible organic solvents is used not only as stripping solvent for MSPE, but also as extraction and disperser solvents for DLLME procedure. Several parameters such as amount of extraction adsorbent, type of stripping, extraction solvents and their volumes, salt effect, and pH and volume of sample solution were optimized to obtain high extraction recoveries. Finally, 2 µL of extraction phase was injected into GC�MS. Under optimal conditions, the method attained satisfactory precisions (RSD � 8.66), excellent limits of detection in the range of 0.1�0.5 ng kg�1 at S/N = 3, and very high enrichment factors in the range of 28,187�33,149 for 500 mL sample solution of different PAHs. The calibration curves of 16 extracted PAHs were linear in the range of 0.4�10,000 ng kg�1, with coefficients of determination (r2) between 0.9989 and 0.9999. The optimized method to determine 16 PAHs has been successfully applied in the real environment including waters, waste water, sewage, and soil. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

A Highly Sensitive Dispersive Microextraction Method with Magnetic Carbon Nanocomposites Coupled with Dispersive Liquid�Liquid Microextraction and Two Miscible Stripping Solvents Followed by GC�MS for Quantification of 16 PAHs in Environmental Samples

Abstract: In this work, a highly sensitive solid-phase-dispersive microextraction method was designed based on magnetic carbon nanocomposites as a magnetic solid-phase extraction sorbent coupled with dispersive liquid�liquid microextraction and two miscible stripping solvents (MSPE�DLLME) followed by gas chromatography�mass spectrometry (GC�MS) for determination of 16 polycyclic aromatic hydrocarbons (PAHs). By adopting this research methodology, a mixture of two miscible organic solvents is used not only as stripping solvent for MSPE, but also as extraction and disperser solvents for DLLME procedure. Several parameters such as amount of extraction adsorbent, type of stripping, extraction solvents and their volumes, salt effect, and pH and volume of sample solution were optimized to obtain high extraction recoveries. Finally, 2 µL of extraction phase was injected into GC�MS. Under optimal conditions, the method attained satisfactory precisions (RSD � 8.66), excellent limits of detection in the range of 0.1�0.5 ng kg�1 at S/N = 3, and very high enrichment factors in the range of 28,187�33,149 for 500 mL sample solution of different PAHs. The calibration curves of 16 extracted PAHs were linear in the range of 0.4�10,000 ng kg�1, with coefficients of determination (r2) between 0.9989 and 0.9999. The optimized method to determine 16 PAHs has been successfully applied in the real environment including waters, waste water, sewage, and soil. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

Polydopamine-Functionalized Carbon Nanotubes for Pipette-Tip Micro-Solid Phase Extraction of Malathion and Parathion from Environmental Samples

In this study, a polydopamine-functionalized multi-walled carbon nanotube was utilized in an efficient pipette-tip micro-solid phase extraction followed by gas chromatography-mass spectrometry for determination of two organophosphorus pesticides called malathion and parathion. All the effective parameters were optimized using a one variable at-a-time protocol. Under the optimal conditions, broad calibration curves were obtained with the linearity in the range between 0.30�200 ng mL�1. Preconcentration factors as high as 42.7 and 47.3 for malathion and parathion, respectively, were obtained along with the relative standard deviations (RSD) lower than 6.37 . Real samples analysis was carried out using the optimized technique for quantitative analysis of the target analytes in environmental water samples. Relative recoveries in the range between 89.37�101.22 show the capability of the method in real sample analysis. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei