Microwave-assisted Cloud-point Extraction Research Articles

A novel, green environment-friendly cloud point extraction of polyphenols from pomegranate peels: a comparative assessment with ultrasound and microwave-assisted extraction

ABSTRACT Pomegranate peel is a potential source of polyphenols, antioxidants, pectin, organic acids. Cloud point extraction (CPE) process parameters were optimized for efficient separation of polyphenols. Maximum extraction was obtained at 1:70 solid: solvent ratio, 8% (v/v) Triton X-114 at 55°C, pH 4.5 with 14% NaCl for 30 minutes. Ultrasound assisted CPE showed maximum yield of total phenolic content (TPC; 96.28 mg GAE/g) and total flavonoids content (TFC; 12.27 mg QE/g) with 94.48% antioxidant activity (AA) to that of conventional, ultrasound and microwave-assisted CPE. These extractives can be labeled as green and may be used in food or dietary applications. Abbreviations: CPE: Cloud point extraction; AA: Antioxidant activity; TPC: Total polyphenol content; TFC: Total flavonoid content; CPT: Cloud point temperature; CMC: Critical micellar concentration; OVAT: One variable at a time; GAE: Gallic acid equivalent; QE: Quercetin equivalent; HLB: Hydrophilic lipophilic balance

Graphene oxide nanosheets in basic medium: a new potential adsorbent for microwave assisted cloud point extraction of beryllium from industrial effluents prior to ICP-OES determination

A novel graphene oxide mediated microwave assisted cloud point extraction is developed in basic solution, for the extraction of ultra trace beryllium from natural water and plant waste water.

Simultaneous extraction and separation of flavonoids and alkaloids from Crotalaria sessiliflora L. by microwave-assisted cloud-point extraction

Abstract A novel method of simultaneous extraction and separation of flavonoids and alkaloids from Crotalaria sessiliflora L., was developed by microwave-assisted cloud-point extraction (MACPE) using Triton X-100−NaCl−HCl system as extractant. The optimum conditions including Triton X-100 concentration, NaCl concentration, HCl concentration, solvent-to-material ratio, extraction temperature and time were investigated by orthogonal test on the single factor experiment. The extraction yields of vitexin, isovitexin and monocrotaline reached respectively up to 601.4, 386.7 and 105.5 μg/g under the optimum conditions. Compared with heating reflux extraction (HRE) and ultrasonic-assisted extraction (UAE), MACPE exhibited a significantly higher extraction yields and took a shorter time (only 10 min). The MACPE mechanism was discussed based on phase’s shift and extraction property. As a result, flavonoids and alkaloids can be transferred respectively to bottom phase and top phase after simultaneous extraction. The proposed method integrated MAE with cloud-point extraction (CPE) in one-step procedure took both advantages. It provided a simple and efficient alternative to extraction and separation of active constituents from the herb materials.

Cloud point extraction of platinum group elements and gold: elimination of nitric acid-related problems with sulphamic acid

Microwave-assisted cloud point extraction (CPE) of platinum group elements (PGEs) and Au in solutions containing aqua regia using 2-mercaptobenzothiazole (2-MBT) was studied. For comparison, the extractions were also performed in hydrochloric acid and nitric acid solutions. A previously published CPE method, employing 2-MBT in hydrochloric acid solutions, was used as a reference method in order to investigate the effect of added nitric acid on the recoveries of Ru, Rh, Pd, Ir, Pt and Au. The results indicated that the presence of nitric acid did not cause problems to the cloud point phenomenon, but had an effect on the complexation processes of 2-MBT, thus leading to low recoveries. Therefore, a novel approach of adding sulphamic acid to enhance the extraction efficiencies of the PGEs and Au in the CPE performed in solutions containing aqua regia was investigated. A clear increase in the recoveries of PGEs and Au in solutions containing aqua regia or nitric acid was observed when sulphamic acid was used. The recoveries for Ru, Rh, Pd, Pt and Au obtained in optimized conditions were between 80 and 100%. However, the recoveries of Ir remained below 40%. The accuracy of the developed method was evaluated by analysing a certified reference material NIST SRM 2557 (used automotive catalyst).

Determination of Pt from coke samples by ICP-MS after microwave assisted digestion and microwave assisted cloud point extraction

Platinum in coke samples was determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted sample digestion and temperature controlled microwave assisted cloud point extraction (MW-CPE). Interferences due to hafnium (179Hf16O) were successfully eliminated using MW-CPE with 2-MBT prior to the determination of platinum by ICP-MS. The validity of the method was studied by spike recovery tests and by analyzing certified reference material (BCR-723 street dust). The results obtained for platinum in the BCR-723 were generally in good agreement with the certified values. Furthermore, the preliminary platinum results obtained for coke sample by ICP-MS after MW-CPE were compared to those obtained by a reference method (NiS-Fire Assay preconcentration/Te coprecipitation and ICP-MS determination).

Investigation of ICP-MS spectral interferences in the determination of Rh, Pd and Pt in road dust: Assessment of correction algorithms via uncertainty budget analysis and interference alleviation by preliminary acid leaching

A method for classification of the potential spectral interferences in inductively coupled plasma mass spectrometry (ICP-MS) was proposed based on statistical assessment of the interfering signals. The concept was applied to investigate the variety of spectral interferences over the isotopes of Rh, Pd and Pt concerning their analysis in road dust samples. For the significant interferences the applicability of mathematical corrections using two alternative algorithms were studied by uncertainty budget analysis and the approach resulting in lower combined uncertainty of the corrected signals was selected. Further the uncertainty evaluation was used for assessment of the most appropriate Pd isotope to be measured. The adequateness of the mathematical corrections for Rh and Pd was highly relevant to the number of elements causing spectral interferences and the relative analyte/interferent concentrations. This was overcome by preliminary road dust leaching with 0.35 mol l −1 hydrochloric acid. Interferents present as easily soluble salts were substantially removed form the samples while the platinum group metals were not leached which allowed a relative analyte preconcentration to be obtained. For the leached samples the isotopes of Rh and Pd were still spectrally interfered from Sr, Y and Pb but at considerably lesser degree thus after mathematical correction the ICP-MS analysis of Rh, Pd and Pt was reliable and robust using the isotopes 103, 105 and 195, respectively. The method was validated via an alternative analysis based on selective separation of the platinum group metals by microwave-assisted cloud point extraction.

Microwave-assisted cloud point extraction of Rh, Pd and Pt with 2-mercaptobenzothiazole as preconcentration procedure prior to ICP-MS analysis of pharmaceutical products

New approaches for acceleration of cloud point extraction of Rh, Pd and Pt by microwave and ultrasound irradiation have been investigated. 2-Mercaptobenzothiazole and Triton X-100 were used as ligand and non-ionic surfactant, respectively. Microwave irradiation substantially increased the procedure efficiency. In contrast no significant effect was observed when a micellar solution was treated with ultrasound energy. The acceleration of complex formation reactions by reducing agents (KI and SnCl2) has also been studied. The use of SnCl2 was a prerequisite for quantitative extraction of Rh. Since the extraction kinetics of platinum depends on its oxidation state and presence of Pd, the addition of SnCl2 equalized the platinum extraction behavior. For the first time the whole cloud point procedure was successively accomplished in a microwave system. 10 min of irradiation were sufficient for gravimetrical phase separation and quantitative extraction of platinum group metals. As a result the procedure time was shortened by a factor of 9 in comparison to conventional hot plate cloud point extraction. The surfactant-rich phase was analyzed after dilution with 1 M HCl by continuous nebulization to ICP-MS. Quantitative recoveries and good plasma tolerance were reported. Detection limits of 1 ng.l−1 (Rh), 5 ng.l−1 (Pd), and 6 ng.l−1 (Pt) were achieved regarding a preconcentration factor of 8. The microwave-assisted cloud point extraction has been successfully applied for simultaneous determination of trace amounts of platinum group metals in pharmaceutical products (Tritace, Vivace, Laprilen and Enalapril).