Liquid phase microextraction associated with flow injection systems for the spectrometric determination of trace elements

Condensed Phase Membrane Introduction Mass Spectrometry: A Direct Alternative to Fully Exploit the Mass Spectrometry Potential in Environmental Sample Analysis

Membrane introduction mass spectrometry (MIMS) is a direct mass spectrometry technique used to monitor online chemical systems or quickly quantify trace levels of different groups of compounds in complex matrices without extensive sample preparation steps and chromatographic separation. MIMS utilizes a thin, semi-permeable, and selective membrane that directly connects the sample and the mass spectrometer. The analytes in the sample are pre-concentrated by the membrane depending on their physicochemical properties and directly transferred, using different acceptor phases (gas, liquid or vacuum) to the mass spectrometer. Condensed phase (CP) MIMS use a liquid as a medium, extending the range to new applications to less-volatile compounds that are challenging or unsuitable to gas-phase MIMS. It directly allows the rapid quantification of selected compounds in complex matrices, the online monitoring of chemical reactions (in real-time), as well as in situ measurements. CP-MIMS has expanded beyond the measurement of several organic compounds because of the use of different types of liquid acceptor phases, geometries, dimensions, and mass spectrometers. This review surveys advancements of CP-MIMS and its applications to several molecules and matrices over the past 15 years.

Preconcentration and determination of five antidepressants from human milk and urine samples by stir bar filled magnetic ionic liquids using liquid-liquid-liquid microextraction-high performance liquid chromatography

A sensitive and straightforward liquid-liquid-liquid microextraction method was developed to preconcentrate and cleanup antidepressants, including mirtazapine, venlafaxine, escitalopram, fluoxetine, and fluvoxamine, from biological samples before analyzing with high-performance liquid chromatography. The essential novelty of this study is using magnetic ionic liquids as the extraction phase in the lumen of hollow fiber and preparing a liquid magnetic stir bar. In the method, polypropylene hollow fiber was utilized as the permeable membrane for the analyte extraction. Six magnetic ionic liquids consisting of the transition metal and rare earth compounds were synthesized and then injected hollow fiber lumen as acceptor phase to extract the antidepressants. Besides, 3-pentanol as a water-immiscible solvent was impregnated in the hollow fiber wall pores. The effective factors in the method were optimized with the central composition design. The resultant calibration curves were linear over the concentration range of 0.8-400.0 ng mL^-1 (R² ≥ 0.996). The method displayed the proper detection limit (0.11-0.24 ng mL^-1 ), the reasonable limit of quantification (≤0.79 ng mL^-1 ), wide linear ranges, high preconcentration factors (≥294.3), and suitable relative standard deviation (2.31-5.47%) for measuring antidepressant medications. Analysis of human milk and urine samples showed acceptable recoveries of 96.5-103.8% with excellent relative standard deviations lower than 5.95%. This article is protected by copyright. All rights reserved.

In-syringe dispersive liquid-liquid microextraction

Dispersive liquid-liquid microextraction (DLLME) has recently been widely used in the separation and preconcentration of various chemical species. Among the various approaches using DLLME are systems that use a syringe as an extraction environment. In this review, details of some methods that use this approach are presented. The ways to promote dispersion, analytical characteristics, and the advantages and disadvantages of the methods, among other aspects, are discussed critically. Finally, some trends in the use of in-syringe microextraction systems are described.

Dispersive liquid-liquid microextraction of Cd, Hg and Pb from medicines prior to ICP OES determination according to the United States Pharmacopeia

A simple, sensitive and matrix-effect free analytical method for simultaneous determination of Cd, Hg and Pb in drug samples (i.e., commercial dosage tablets) by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to the United States Pharmacopeia (USP) Chapter 232, those metals are considered elemental impurities from class 1 and they must be assessed in pharmaceutical production as well as in quality control evaluation. In order to increase the sensitivity of the analysis, dispersive liquid-liquid microextraction (DLLME) was performed and seven factors affecting analyte extraction were optimized by multivariate analysis. A microvolume of analyte enriched phase was directly introduced into the plasma using a multi-nebulizer, providing a high enrichment factor. When compared to conventional ICP OES analysis, DLLME improves the limit of quantitation (LOQ) values on average 40-fold for all analytes. Consequently, LOQ values were significantly lower than their permissible daily exposure limits for oral drugs. Accuracy was evaluated by addition and recovery experiments following USP recommendations in eight commercial drug samples. Recovery and RSD values were within the range of 90-108% and 1-9%, respectively.

Dispersive liquid-liquid microextraction based on deep eutectic solvent for elemental impurities determination in oral and parenteral drugs by inductively coupled plasma optical emission spectrometry

A simple, fast, sensitive and green pretreatment method for determination of Cd, Co, Hg, Ni, Pb and V in oral and parenteral drug samples using inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to United States Pharmacopoeia (USP), those metals must be reported in all pharmaceutical products for quality control evaluation (i.e., elemental impurities from classes 1 and 2A of USP Chapter 232). To improve the analytical capabilities of ICP OES, a dispersive liquid-liquid microextraction (DLLME) has performed using a safe, cheap and biodegradable deep eutectic solvent (DES) as extractant solvent (a mixture of 2:1 M ratio of DL-menthol and decanoic acid). Seven parameters affecting the microextraction efficiency have carefully optimized by multivariate analysis. Under optimized conditions, the DES-based DLLME-ICP OES procedure improved limit of quantitation (LOQ) values on range from 12 to 85-fold and afforded an enrichment factor on average 60-times higher than those obtained to direct ICP OES analysis. Consequently, LOQ values for Cd, Co, Hg, Ni, Pb and V have been on average 10-times lower than target limits recommended for drugs from parenteral route of administration. Trueness has evaluated by addition and recovery experiments following USP recommendations for three oral drug samples in liquid dosage form and three parenteral drugs. Recovery and RSD values have been within the range of 90-109% and 1-6%, respectively. All analytes were below the respectives LOQ values, hence, lower than the limits proposed by USP Chapter 232.

Multivariate optimization of a dispersive liquid-liquid microextraction method for determination of copper and manganese in coconut water by FAAS

In this study, multivariate methodologies were applied in the optimization of a dispersive liquid-liquid microextraction (DLLME) method, aiming at the determination of Cu and Mn in coconut water samples by flame atomic absorption spectrometry. Some extractors (chloroform and CCl₄), dispersants (ethanol, methanol and acetonitrile) and complexing agents (5-Br-PADAP and Dithzone) were previously tested in the extraction. A mixture design was used to optimize the component proportions formed by chloroform (10%), acetonitrile (76%), and 0.020% 5-Br-PADAP solution (14%). Doehlert design optimized the variables pH, NaCl, and buffer amounts for the extraction of both metals. The following analytical characteristics, respectively for Cu and Mn, were accessed: limit of quantification (4.83 and 3.32 µg L^-1), enrichment factors (11 and 8 fold), and precision (6.6 and 6.0% RSD, n = 10). Addition/recovery tests of the analytes allowed to find values in the range of 96.5-120% for Cu and 99-107% for Mn.

Nonionic surfactants based hydrophobic deep eutectic solvents for liquid-liquid microextraction of Sudan dyes in tomato chili sauces

A new type of high-density hydrophobic deep eutectic solvents (DESs) were synthesized with nonionic surfactants as hydrogen bond acceptors and hexafluoroisopropanol (HFIP) as hydrogen bond donor. Brij-35 was selected as the optimal nonionic surfactant for the preparation of Brij-35-HFIP-DES (molar ratio 1:20). A vortex-assisted DES-based liquid-liquid microextraction method was proposed for determination of Sudan dyes in tomato chili sauces. The whole pretreatment process only needs 5 min and 1.1 mL of organic solvent. The method with HPLC-DAD shows high efficiency (enrichment factors 89-176 and extraction rates 61.0-74.6%) and good performance with linearity (R ≥ 0.9997) in 0.04-2 μg g^-1 range, detection limits of 0.0045-0.0118 μg g^-1, recoveries of 91.6-104.5% and intra-/inter-day precision below 8.0%. A "DES in water in DES" aggregate microstructure was observed in DES-rich phase. The proposed method is simple, quick, eco-friendly, and suits for the efficient extraction and accurate determination of Sudan dyes in tomato chili sauces.

A novel direct-immersion single-drop microextraction combined with digital colorimetry applied to the determination of vanadium in water

In this study, a method based on direct-immersion single-drop microextraction was developed for the determination of vanadium in water. The detection system uses digital images obtained directly from the solvent drop after the sorption of V(V). The extraction solvent used was the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]). The images were obtained directly from the solvent drop, with the aid of a camera. The digital images were stored, and the RGB (red, green, and blue) data were obtained. The data collected by the red channel were used to construct the analytical curve since it showed higher sensitivity compared with green and blue channels. Under optimized conditions, the method presented an enrichment factor of 50 and a limit of detection of 0.6 μg L^-1 for 3.5 mL sample volume. The limit of quantification and the relative standard deviation (50.0 μg L^-1) obtained were 1.8 μg L^-1 and 4.8%, respectively. Certified reference material (Plankton) was used to assess the accuracy of the method. The simple, fast, efficient, and low-cost procedure was successfully applied to the determination of V(V) in water samples. The proposed method is also following the principles of green chemistry since it uses minimal volumes of samples, reagents, and solvents and yields a small amount of waste.

Combined liquid phase microextraction and fiber-optics-based cuvetteless micro-spectrophotometry for sensitive determination of ammonia in water and food samples by the indophenol reaction

The Berthelot reaction for ammonia is revisited with the aim of miniaturization and addressing interferences as encountered with food and water samples. Headspace single drop microextraction of ammonia in phosphoric acid served to attain selectivity in complex matrices, and liquid-liquid microextraction of red or blue indophenol species into 1-octanol-isooctane (60:40, v/v) resulted into high sensitivity. Fiber-optics-based cuvetteless micro-spectrophotometry has been used for colorimetric determination on microliter volumes of extract. The linear dynamic range, limit of detection and enrichment factor have been found to be 0.2-3 mg kg^-1, 0.14 mg kg^-1 and 38, respectively, measuring red species for milk, cheese and beer (4.9-5.5% error; 4.8-6.3% RSD; n = 5); and 5-400 µg L^-1, 0.4 µg L^-1 and 137, respectively, measuring blue species for water samples (3.3-5.7% error; 3.6-6.8% RSD; n = 5). A plausible reaction scheme has been proposed for nitroprusside catalysis in indophenol reaction.

Direct immersion single-drop microextraction of semi-volatile organic compounds in environmental samples: A review

Single-drop microextraction (SDME) techniques are efficient approaches to pretreatment of aqueous samples. The main advantage of SDME lies in the miniaturization of the solvent extraction process, minimizing the hazards associated with the use of toxic organic solvents. Thus, SDME techniques are cost-effective, and represent less harm to the environment, subscribing to green analytical chemistry principles. In practice, two main approaches can be used to perform SDME - direct immersion (DI)-SDME and headspace (HS)-SDME. Even though the DI-SDME has been shown to be quite effective for extraction and enrichment of various organic compounds, applications of DI-SDME are normally more suitable for moderately polar and non-polar semi-volatile organic compounds (SVOCs) using organic solvents which are immiscible with water. In this review, we present a historical overview and current advances in DI-SDME, including the common analytical tools which are usually coupled with DI-SDME. The review also focuses on applications concerning SVOCs in environmental samples. Currents trends in DI-SDME and possible future direction of the procedure are discussed.

Simultaneous quantification of peroxidase and ascorbic acid in biosamples with an automatic system based on a Fe(iii)/methylthymol blue-carbon dot simulative enzyme

Simultaneous and automatic quantification of peroxidase and ascorbic acid based on one reaction system and application of a carbon dot simulative enzyme.