An eco-friendly sample preparation procedure based on air-assisted liquid-liquid microextraction for the rapid determination of phthalate metabolites in urine samples by liquid chromatography-tandem mass spectrometry

Urinary phthalate metabolite (mPAEs) analysis is a reliable tool for assessing human exposure to phthalates. With growing interest in urinary biomonitoring of these metabolites, there is a need for fast and sensitive analytical methods. Therefore, a simple, rapid procedure for simultaneous determination of fifteen phthalate metabolites in human urine samples by liquid chromatography-tandem mass spectrometry was developed. The novelty of the present procedure is based on the use of diethyl carbonate as a green biobased extraction solvent and air-assisted liquid-liquid microextraction (AALLME) as a sample preparation step. A Plackett-Burman design was used for screening the factors that influence the AALLME extraction efficiency of mPAEs. The effective factors were then optimized by response surface methodology using a central composite rotatable design. Under the optimized conditions, good linearity can be achieved in a concentration range of 1.0-20.0 ng mL-1 with correlation coefficients higher than 0.99. The repeatability and reproducibility precision were in the range of 2-12% and 1-10% respectively. Recoveries ranging from 90% to 110%. This, and the low limits of detection, ranging from 0.01 to 0.05 ng mL-1, make the proposed procedure sensitive and suitable for human biomonitoring of phthalate exposures. For proof-of-principle, the new method was used to measure the urinary concentrations of mPAEs in 20 urine samples from Brazilian women. The high frequency of detections and in part high concentrations of mPAEs indicate to widespread exposure to several phthalates among Brazilian women.

Modified μ-QuEChERS coupled to diethyl carbonate-based liquid microextraction for PAHs determination in coffee, tea, and water prior to GC-MS analysis: An insight to reducing the impact of caffeine on the GC-MS measurement

A fast, sensitive and eco-friendly method was developed for the determination of fifteen polycyclic aromatic hydrocarbons (PAHs) in different environmental matrices through gas chromatography mass spectrometry (GC-MS). The method utilizes a modified and miniaturized quick easy cheap effective rugged and safe (QuEChERS) clean up procedure coupled to an air-assisted dispersive liquid-liquid microextraction (AA-DLLME) for the enrichment of the concerned compounds. The AA-DLLME uses diethyl carbonate (DEC) as a green bio-based solvent for the microextraction. DEC is considered as biodegradable (with octanol/water coefficient < 3, resulting in low potential of bioaccumulation), classified as a green solvent and considered as one of the recommended solvent alternatives based on SSG results. The AA-DLLME procedure was optimized by One-Variable-at-A-Time (OVAT) succeeded by experimental design applying Central Composite Face-centered (CCF) design. The method linear calibration was found in the range of 10-120 µg/Kg for Benzo[a]pyrene and 5-100 µg/Kg for all other PAHs with low detection limits ranging from 0.01 to 2.10 µg/Kg. It could enrich the PAHs up to 166-folds. The combination of modified μ-QuEChERS with the green AA-DLLME could sharply decrease the caffeine amount on the final extract injected to the GC-MS instrument. The method was successfully applied to coffee, tea, and water samples with acceptable % recovery (>90%). Finally, the impact of our procedure to the environment from green analytical chemistry view was assessed by a novel metric system called AGREE, proving the greenness of our procedure.

Explosion characteristics for Li-ion battery electrolytes at elevated temperatures

Li-ion batteries are used in electronic devices and electric cars, yet they create safety concerns due to the possibility of the release of combustible materials. The electrolyte, one of the main components in a Li-ion cell, consists of organic carbonates. Venting and thermal runaway release organic carbonates and when mixed with air, it can result in fires and explosions. A 20-liter explosion sphere was used to determine the explosion characteristics for three typical carbonates used in electrolytes, at 373 K, and 100 kPa absolute pressure. The explosion pressure and the maximum rate of explosion pressure rise are presented for the carbonates and for hydrogen, methane, and propane, and the explosive limits for the carbonates are also identified at the same conditions. This allowed a comparison of the explosion characteristics for the carbonates with those for hydrogen, methane, and propane. Theoretical calculations gave a higher explosion pressure than that from the experimental results most likely due to losses in the hydrocarbon experiments. The carbonates analyzed have very similar explosion pressures and rate of explosion pressure rise as propane. The explosion characteristics found for the three carbonates can be used in future consequence and risk assessments for Li-ion battery installations.

Environment-friendly synthesis of diethyl carbonate via ethyl carbamate alcoholysis over cerium oxide catalyst

A series of cerium oxide catalysts were prepared by simply calcination of nitrate cerium, and used for clean synthesis of diethyl carbonate (DEC) by ethyl carbamate (EC) alcoholysis. 51% conversion and 82% selectivity were obtained with catalyst CeO₂-600. Almost the same activity as the fresh sample could be regained if the used catalyst was recalcined at 600 °C. XPS, XRD, CO₂-TPD and BET study suggested that high surface area and the presence of abundant basic sites are important to achieve a higher catalytic performance.