In-syringe low-density solvent dispersive liquid-liquid microextraction of Pd(II) from acidic solutions resulting from hydrometallurgical treatments and quantification by ICP-OES

An in-syringe low-density solvent dispersive liquid-liquid microextraction (IS-LDS-DLLME) is presented for the extraction of palladium from a highly acidic medium before its quantification by inductively coupled plasma optical emission spectroscopy. The extraction solvent was 1-undecanol, and benzil mono-(2-pyridyl) hydrazone was employed as a ligand. Here, no dispersive solvent is needed as the vortex disperses 1-undecanol in the aqueous sample solution. The experimental variables pH, concentration of the ligand, type and quantity of the extraction solvent, vortex time, and addition of NaCl were optimized. The described approach has detection and quantification limits of 0.13 and 0.43 μg L-1, respectively, an enrichment factor of 91, a linear analytical range from 0.4 to 250 μg L-1, and a precision of 1.7-2.0 % (25.0 μg L-1). The approach was used to analyze electronic waste samples and certified reference material.

A simple and portable vacuum assisted headspace solid phase microextraction device coupled to gas chromatography based on covalent organic framework/metal organic framework hybrid for simultaneous analysis of volatile and semi-volatile compounds in soil

Various microextraction methods have demonstrated a positive effect when assisted by vacuum. However, working with such systems is often laborious, they often require expensive and non-portable vacuum pumps, and may even suck off some sample vapor or solid particles during the evacuation process. To address these issues, a simple, and affordable vacuum-assisted headspace solid-phase microextraction (HS-SPME) device was developed in this study. The device, named In Syringe Vacuum-assisted HS-SPME (ISV-HS-SPME), utilizes an adjustable 40 mL glass syringe as a vacuum provider and sampling vessel. A new fiber coating, made from a hybrid of covalent triazine-based frameworks and metal-organic frameworks (COF/MOF), was prepared and characterized by Fourier transform infrared spectrometry, field emission scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis, and Brunauer-Emmett-Teller techniques for use in the ISV-HS-SPME. By optimizing parameters such as extraction temperature, extraction time, desorption temperature, desorption time, and, humidity using a simplex method, the ISV system was found to increase the extraction efficiency of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BTEX) in solid samples by up to 175%. The determinations were followed by GC-FID measurements. Compared to three commercially available fibers, the ISV-HS-SPME device with the COF/MOF (2DTP/MIL-101-Cr) fiber exhibited significantly higher peak areas for PAHs and BTEX. The linear dynamic ranges for BTEX and PAHs were 7.1-9000 ng g-1 and 0.23-9000 ng g-1, respectively, with limits of detection ranging from 2.1-5 ng g-1 for BTEX and 0.07-1.6 ng g-1 for PAHs. The relative standard deviation of the method was 2.6-7.8% for BTEX and 1.6-6.7% for PAHs. The ISV-HS-SPME was successfully used to simultaneously determine PAHs and BTEX in polluted soil samples with recoveries ranging from 80.4 to 108%.

Surface Functionalization with Polymer Membrane or SEIRA Interface to Improve the Sensitivity of Chalcogenide-Based Infrared Sensors Dedicated to the Detection of Organic Molecules

Priority substances likely to pollute water can be characterized by mid-infrared spectroscopy based on their specific absorption spectral signature. In this work, the detection of volatile aromatic molecules in the aqueous phase by evanescent-wave spectroscopy has been optimized to improve the detection efficiency of future in situ optical sensors based on chalcogenide waveguides. To this end, a hydrophobic polymer was deposited on the surface of a zinc selenide prism using drop and spin-coating methods. To ensure that the water absorption bands will be properly attenuated for the selenide waveguides, two polymers were selected and compared: polyisobutylene and ethylene/propylene copolymer coating. The system was tested with benzene, toluene, and ortho-, meta-, and para-xylenes at concentrations ranging from 10 ppb to 40 ppm, and the measured detection limit was determined to be equal to 250 ppb under these analytical conditions using ATR-FTIR. The polyisobutylene membrane is promising for pollutant detection in real waters due to the reproducibility of its deposition on selenide materials, the ease of regeneration, the short response time, and the low ppb detection limit, which could be achieved with the infrared photonic microsensor based on chalcogenide materials. To improve the sensitivity of future infrared microsensors, the use of metallic nanostructures on the surface of chalcogenide waveguides appears to be a relevant way, thanks to the plasmon resonance phenomena. Thus, in addition to preliminary surface-enhanced infrared absorption tests using these materials and a functionalization via a self-assembled monolayer of 4-nitrothiophenol, heterostructures combining gold nanoparticles/chalcogenide waveguides have been successfully fabricated with the aim of proposing a SEIRA microsensor device.

Determination of BTEX Compounds in Contaminated Water Using the Novel Vacuum-Assisted-Total Vaporization SPME Method and GO-APTES Fiber

A novel and reliable microextraction technique was used for the fast determination of benzene, toluene, ethylbenzene and xylenes (BTEX) from contaminated water without any extra steps for the preparation or extraction of the aqueous sample. Vacuum-assisted-total vaporization-solid-phase microextraction (SPME) eliminated one of the partitioning steps in conventional headspace SPME and caused an increase in the sensitivity and speed of the method. A home-made graphene oxide/3-aminopropyl-triethoxysilane nanocomposite SPME fiber was synthesized and used as the extraction phase for efficient extraction. Several crucial parameters were optimized, such as the vaporization time and temperature, extraction time and desorption conditions. At the optimum experimental conditions, a linear wide range calibration curve over a wide range of 1-5,000 ng mL-1 and a relative standard deviation (n = 6) of 6.6-7.3% were obtained. The result of the determination of BTEX as a human health risk from real samples, using the proposed method, revealed an acceptable agreement with a valid method.

Untargeted SPME-GC-MS Characterization of VOCs Released from Spray Paint

Paints are a common form of physical evidence encountered at crime scenes. This research presents an optimized method for the untargeted analysis of volatile organic compounds (VOCs) in spray paint using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The presence and persistence of VOCs were monitored in 30 minute intervals, over a 4 hour period, in a triplicate time study. As predicted, spray paint solvents are lost to the environment readily, whereas few VOCs remained present in the headspace in low concentrations beyond 4 hours. The VOCs that were observed to have the highest persistence in the headspace were aromatic compounds and those with longer hydrocarbon chains. We present this study in a forensic science context and suggest that the interpretation of the results may be useful for forensic applications in establishing a time since deposition of a spray-painted surface.

Headspace conditions and ingredients can affect artefactual benzene formation in beverages

A headspace sampling-gas chromatography/mass spectrometry (HS-GC/MS) method using mild HS conditions (40 °C, 30 min) was established, validated in terms of specificity, linearity (1.75-87.65 ng mL^-1), precision (0.3-9.1% RSD), and accuracy (81.1-117.7%); and applied for the monitoring of 900 commercial beverage samples of six different types. These mild (low-temperature) conditions were compared with 1) optimized (high-temperature) conditions and 2) a liquid-phase microextraction method involving no heat treatment. This method was desirable because a high equilibrium temperature induced artefactual benzene formation from benzoate and ascorbic acid. In a 2_IV^8-3 fractional factorial design, eight variables-ascorbic acid, benzoate, benzaldehyde, Cu²⁺, Fe²⁺, riboflavin, pyridoxine, and heat treatment-were tested as potential factors affecting benzene formation. All variables except Fe²⁺ and pyridoxine significantly affected benzene formation, both individually and interactively. The present study suggests an accurate and reliable method for benzene analysis and provides strategies to prevent unintentional benzene formation in beverages.

Central Composite Design for Dispersive Liquid-liquid Microextraction of 25-hydroxy-cholecalciferol in Human Serum

The human body's vitamin D levels are determined by measuring the level of 25-hydroxy-vitamin D3 (25-OH-vitamin D3) in human serum. In this research, a fast, simple, efficient and highly sensitive low-density solvent based on dispersive liquid-liquid microextraction (DLLME) was employed for the successful determination of 25-OH-vitamin D3 from complex human serum matrices. Reversed phase high-performance liquid chromatography was used as a powerful technique. The important parameters in the low-density solvent-DLLME method were optimized using response surface methodology based on central composite design. The calibration curves displayed a high level of linearity (R2 > 0.997) for 25-OH-vitamin D3 in the range of 2-500 ng mL-1. The limit of detection and limit of quantitation were 0.6 ng mL-1 and 1.9 ng mL-1, respectively. The relative standard deviation for the seven analyses was 7.1%. The relative recoveries of vitamin D3 in spiked human serum samples were between 85% and 97%. The amount of 25-OH-vitamin D3 in samples was determined using the proposed method and acceptable results were reported.