Simplified procedures for the analysis of polycyclic aromatic hydrocarbons in water, sediments and mussels

We describe in this paper simple and robust analytical protocols to determine the 16 polycyclic aromatic hydrocarbons (PAHs) of the US Environmental Protection Agency priority list in water, sediment and mussels. For water samples, eight different solid-phase extraction (SPE) sorbents have been compared and among them, C18 provided highest recoveries and limits of detection of 0.3-15 ng/L. For lyophilized sediments, Soxhlet and ultrasonic extraction were compared, and the last one permitted to recover all analytes with highest repetitivity and was validated by analysing a certified reference material. Finally, the analysis of mussels was undertaken using Soxhlet, ultrasonic and pressurized liquid extraction (PLE) and the performance of several clean-up steps are compared. Whereas for the former two, incomplete recovery or losses of some analytes were evidenced, PLE permitted a more efficient extraction and although alkaline digestion was necessary to remove coextracted compounds, the method gave acceptable recoveries and limits of detection of 0.5-7.7 microg/kg dry mass, as for sediments. In all cases, analysis was performed by gas chromatography coupled to mass spectrometry and internal standard quantification was performed using five deuterated PAHs. Each method performance is discussed for the three matrices analysed and the paper reports advantages and disadvantages of each for their routine application in monitoring programs.     

Thermosensitive gels incorporating polythioether units for the selective extraction of class b metal ions

Novel temperature-responsive copolymers of N-isopropylacrylamide and monoaza-tetrathioether derivative, were synthesized for the selective extraction of soft metal ions such as silver(I), copper(I), gold(III) and palladium(II) ion. The ratio between N-isopropylacrylamide group and monoaza-tetrathioether group in the copolymer was determined. The ratio between N-isopropylacrylamide group and monoaza-tetrathioether group varied in the range of 66:1–187:1. Each lower critical solution temperature (LCST) of the polymer solution was determined spectrophotometrically by the relative absorbance change at 750 nm via temperature of the polymer solution. Metal ion extraction using the copolymer with appropriate counter anions such as picrate ion, nitrate or perchlorate ion was examined. Soft metal ions such as silver(I), copper(I), gold(III) and palladium(II) ion were extracted selectively into the solid polymer phase. The extraction efficiency of a metal ion such as silver ion increased as the increase of the ratio of the monoaza-tetrathioether group to N-isopropylacrylamide group in the polymer. The quantitative extraction of class b metal ions as well as the liquid–liquid extraction of metal ions with monoaza-tetrathioether molecule was performed.     

A cost effective,sensitive, and environmentally friendly sample preparation method for determination of polycyclic aromatic hydrocarbons in solid samples

A simple, cost effective, and yet sensitive sample preparation technique was investigated for determining Polycyclic Aromatic Hydrocarbons (PAHs) in solid samples. The method comprises ultrasonic extraction, Stir Bar Sorptive Extraction (SBSE), and thermal desorption–gas chromatography–mass spectrometry to increase analytical capacity in laboratories. This method required no clean-up, satisfied PAHs recovery, and significantly advances cost performance over conventional extraction methods, such as Soxhlet and Microwave Assisted Extraction (MAE). This study evaluated three operational parameters for ultrasonic extraction: solvent composition, extraction time, and sample load. A standard material, SRM 1649 a (urban dust), was used as the solid sample matrix, and 12 priority PAHs on the US Environmental Protection Agency (US EPA) list were analyzed. Combination of non-polar and polar solvents ameliorated extraction efficiency. Acetone/hexane mixtures of 2:3 and 1:1 (v/v) gave the most satisfactory results: recoveries ranged from 63.3% to 122%. Single composition solvents (methanol, hexane, and dichloromethane) showed fewer recoveries. Comparing 20 min with 60 min sonication, longer sonication diminished extraction efficiencies in general. Furthermore, sample load became a critical factor in certain solvent systems, particularly MeOH. MAE was also compared to the ultrasonic extraction, and results determined that the 20-min ultrasonic extraction using acetone/hexane (2:3, v/v) was as potent as MAE. The SBSE method using 20 mL of 30% alcohol-fortified solution rendered a limit of detection ranging from 1.7 to 32 ng L⁻¹ and a limit of quantitation ranging from 5.8 to 110 ng L⁻¹ for the 16 US EPA PAHs.     

A new acetonitrile-free mobile phase method for LC-ELSD quantification of fructooligosaccharides in onion (Allium cepa L.)

Onion soluble non-structural carbohydrates consist of fructose, glucose and sucrose plus fructooligosaccharides (FOS) with degrees of polymerisation (DP) in the range of 3-19. In onion, sugars and FOS are typically separated using liquid chromatography (LC) with acetonitrile (ACN) as a mobile phase. In recent times, however, the production of ACN has diminished due, in part, to the current worldwide economic recession. A study was therefore undertaken, to find an alternative LC method to quantify sugars and FOS from onion without the need for ACN. Two mobile phases were compared; the first taken from a paper by Vågen and Slimestad (2008) [3] using ACN mobile phase, the second, a newly reported method using ethanol (EtOH). The EtOH mobile phase eluted similar concentrations of all FOS compared to the ACN mobile phase. In addition, limit of detection, limit of quantification and relative standard deviation values were sufficiently and consistently lower for all FOS using the EtOH mobile phase. The drawback of the EtOH mobile phase was mainly the inability to separate all individual sugar peaks, yet FOS could be successfully separated. However, using the same onion extract, a previously established LC method based on an isocratic water mobile phase could be used in a second run to separate sugars. Although the ACN mobile phase method is more convenient, in the current economic climate a method based on inexpensive and plentiful ethanol is a valid alternative and could potentially be applied to other fresh produce types.In addition to the mobile phase solvent, the effect of extraction solvents on sugar and FOS concentration was also investigated. EtOH is still widely used to extract sugars from onion although previous literature has concluded that MeOH is a superior solvent. For this reason, an EtOH-based extraction method was compared with a MeOH-based method to extract both sugars and FOS. The MeOH-based extraction method was more efficacious at extracting sugars and FOS from onion flesh, eluting significantly higher concentrations of glucose, kestose, nystose and DP5-DP8.     

Rapid removal of selected volatile organic compounds from gaseous mixtures using a new dispersive vapor extraction technique: A feasibility study

A new dispersive vapor extraction (DVE) technique for rapid removal of selected volatile organic compounds (VOCs) from gaseous mixtures was investigated. In this technique, less than 1.0 mL of a volatile solvent was vaporized for 8 min in a 250-mL flask containing a gaseous mixture. The flask was then cooled under running tap water for 2-3 min to induce condensation of the vapor and co-extraction of the VOCs from the headspace. The technique was tested over a concentration range of 4-23 ppb, and resulted in extraction efficiencies ranging from 80 to 97% for the VOCs tested. Because of its simplicity and the relatively short sampling time, DVE could potentially lead to high sample throughput and rapid air analysis.     

Ionic liquid-based microwave-assisted extraction of rutin from Chinese medicinal plants

An ionic liquid-based microwave-assisted extraction (ILMAE) method has been developed for the effective extraction of rutin from Chinese medicinal plants including Saururus chinensis (Lour.) Bail. (S. chinensis) and Flos Sophorae. A series of 1-butyl-3-methylimidazolium ionic liquids with different anions were investigated. The results indicated that the characteristics of anions have remarkable effects on the extraction efficiency of rutin and among the investigated ionic liquids, 1-butyl-3-methylimidazolium bromide ([bmim]Br) aqueous solution was the best. In addition, the ILMAE procedures for the two kinds of medicinal herbs were also optimized by means of a series of single factor experiments and an L₉ (3⁴) orthogonal design. Compared with the optimal ionic liquid-based heating extraction (ILHE), marinated extraction (ILME), ultrasonic-assisted extraction (ILUAE), the optimized approach of ILMAE gained higher extraction efficiency which is 4.879 mg/g in S. chinensis with RSD 1.33% and 171.82 mg/g in Flos Sophorae with RSD 1.47% within the shortest extraction time. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet detection was employed for the analysis of rutin in Chinese medicinal plants. Under the optimum conditions, the average recoveries of rutin from S. chinensis and Flos Sophorae were 101.23% and 99.62% with RSD lower than 3%, respectively. The developed approach is linear at concentrations from 42 to 252 mg L⁻¹ of rutin solution, with the regression coefficient (r) at 0.99917. Moreover, the extraction mechanism of ILMAE and the microstructures and chemical structures of the two researched samples before and after extraction were also investigated. With the help of LC-MS, it was future demonstrated that the two researched herbs do contain active ingredient of rutin and ionic liquids would not influence the structure of rutin.     

A surprising method for green extraction of essential oil from dry spices: Microwave dry-diffusion and gravity

Without adding any solvent or water, we proposed a novel and green approach for the extraction of secondary metabolites from dried plant materials. This "solvent, water and vapor free" approach based on a simple principle involves the application of microwave irradiation and earth gravity to extract the essential oil from dried caraway seeds. Microwave dry-diffusion and gravity (MDG) has been compared with a conventional technique, hydrodistillation (HD), for the extraction of essential oil from dried caraway seeds. Essential oils isolated by MDG were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by HD, but MDG was better than HD in terms of rapidity (45min versus 300min), energy saving, and cleanliness. The present apparatus permits fast and efficient extraction, reduces waste, avoids water and solvent consumption, and allows substantial energy savings.     

Extraction and isolation of catechins from tea

Tea is a major source of catechins, which have become well known for their antioxidant potential. Numerous human, animal, and in vitro studies have linked tea catechins with prevention of certain types of cancers, reduction of the risks for obesity, diabetes, and cardiovascular disease, and improvement of the immune system. Tea catechins are widely used in various neutraceuticals, pharmaceuticals, and cosmetics for either enhancing product shelf-life or for enhancing human health. Thus, the demand for catechins has increased considerably. Catechins have been extracted and isolated from tea leaves by numerous methods through several steps including: treatment of the tea leaves, extraction of catechins from teas into solvents, isolation of catechins from other extracted components, and drying the preparations to obtain catechin extracts in a powder form. This paper outlines the physical and chemical properties of the tea catechins and reviews the extraction steps of the various extraction methods, as a basis to improve and further develop the extraction and isolation of the tea catechins.     

Design and synthesis of a new series of amphiphilic peptide-β-cyclodextrins as phase transfer carriers for glucosamine

A new series of amphiphilic β-cyclodextrins were designed and synthesized by grafting peptide chains on to all primary hydroxyl groups via ester bond formation. The desired amphiphilic structures have been produced from ester connection between the C-6 of β-cyclodextrin and the carboxyl group of N-acetylated resides: H₂N-Leu-COOH, H₂N-Leu-Gly-COOH, H₂N-Leu-Gly-Leu-COOH, and H₂N-Leu-Gly-Leu-Gly-COOH (3a-d). The synthetic pathway involves selective bromination of all primary hydroxyls of β-cyclodextrins and then substitution with the carboxylate moiety of the mentioned N-acetyl residues in the presence of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene). The ability of the synthetic compounds for extraction and phase transfer of glucosamine, as a hydrophilic organic compound, was then studied. The results showed a considerable ability of these amphiphilic compounds for extraction and a selective tendency of 3c for phase transfer of glucosamine.