Comparison of gas chromatography–mass spectrometry and capillary electrophoresis in analysis of phenolic compounds extracted from solid matrices with pressurized hot water

Pressurized liquid extraction as a green approach in food and herbal plants extraction: A review

Pressurized liquid extraction is a "green" technology for the extraction of nutraceuticals from foods and herbal plants. This review discusses the extraction principles and the optimization of the extraction parameters that improves the extraction efficiency. The use of different solvent mixtures and other extraction additives to enhance the efficiency of the extraction are discussed. Dynamic mode of extraction in Pressurized liquid extraction, and the use of combined and hyphenated sample preparation and analytical techniques are presented. This work discusses how different studies used Pressurized liquid extraction to enrich phenolic compounds, lignans, carotenoids, oils and lipids, essential oils and other nutraceuticals from foods and herbal plants.

Determining the Oleic/linoleic Acid Ratio in a Single Peanut Seed: a Comparison of Two Methods

Peanut varieties with high oleic/linoleic acid ratios have become preferred by the peanut industry due to their increased shelf life and improved health benefits. Many peanut breeding programs are trying to incorporate the high oleic trait into new and improved varieties and are in need of diagnostic tools to track its inheritance early in development and at the single seed level. Traditionally, gas chromatography has been used to accurately determine the properties of peanut oil. Recently a method was developed to carry out this analysis by capillary elecrophoresis providing researchers with an alternative analytical platform. In this study, the use of capillary electrophoresis and gas chromatography for analysis of oleic/linoleic acid ratios are compared. Oil was extracted from approximately 0.10 g of peanut seed tissue taken from the distal end, leaving the embryonic end of the seed intact for subsequent germination. Over 100 samples inclusive of runner, Spanish and Virginia market types were processed. Oil extracts were analyzed for oleic/linoleic acid ratio using (1) capillary electrophoresis (CE) and (2) gas chromatography (GC). Results showed that the two methods are 100% in agreement in determining whether a peanut seed is “high-oleic” or “normal oleic” in oil content. Furthermore, the two methods are highly correlated (r  =  0.96; p < 0.0001) with respect to determining the exact oleic/linoleic acid ratio from each sample. Results from this study validate the use of CE as a diagnostic tool for breeding programs to identify individual high oleic peanut seed for further testing and development.

Pressurized hot water extraction (PHWE)

Pressurized hot water extraction (PHWE) has become a popular green extraction method for different classes of compounds present in numerous kinds of matrices such as environmental, food and botanical samples. PHWE is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and soils/sediments for environmental monitoring purposes. The main parameters which influence its extraction efficiency are namely the temperature, extraction time, flow rates and addition of modifiers/additives. Among these different parameters studied, temperature is described as the most important one. It is reported that the extraction of certain compounds is rather dependent on pressurized water with different applied temperature. Thus, the stability and reduced solubilities of certain compounds at elevated temperatures are highlighted in this review. With some modifications, a scaled-up PHWE could extract a higher amount of desirable compounds from solid and powdered samples such as plant and food materials. The PHWE extracts from plants are rich in chemical compounds or metabolites which can be a potential lead for drug discovery or development of disease-resistant food crops.

Water-Induced Coacervation of Alkyl Carboxylic Acid Reverse Micelles: Phenomenon Description and Potential for the Extraction of Organic Compounds

Coacervates made up of alkanoic (C8-C16) and alkenoic (C18) acid reverse micelles were described for the first time, and their potential for the extraction of organic compounds prior to liquid chromatography was examined. The coacervation process occurred in miscible binary mixtures of water and a variety of protic and aprotic solvents. The phase behavior of alkyl carboxylic acids was found to be a function of both the Hildebrand solubility parameter, delta, and the hydrogen-bonding capability of the solvent. The best solvents for analytical extractions were those featuring the lowest delta values. The phase behavior of alkyl carboxylic acid/water/tetrahydrofuran (THF) ternary systems as a function of component concentration, pH, ionic strength, and temperature was investigated. The efficiency and the time required for phase separation depended on the experimental procedure used (i.e., standing, centrifugation, stirring, and sonication). The formation of alkyl carboxylic acid reverse micelles in THF was proven using both hydrophilic fluorescent probes and scattered light measurements. The structure of the coacervates consisted of spherical droplets dispersed in a continuous phase. Phase volume ratios were a function of both alkyl carboxylic acid and THF concentration. The low volume obtained (e.g., 1.5 microL per mg of decanoic) compared to that obtained by other coacervates (e.g., 5.1 microL per mg of dodecane sulfonic acid and 11.3 microL per mg of Triton X-114) greatly improved the concentration factors reached by coacervation-based extractions. Parameters affecting the extraction efficiency were assessed. Analytes in a wide range of polarity were efficiently extracted on the basis of the hydrophobic (e.g., PAHs) and hydrogen bond (e.g., chlorophenols, bisphenols, pesticides, phthalates, nonionic surfactants, dyes, and photographic developers) interactions that reverse micelles can establish. The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. They were successfully applied to the extraction of alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates (C12-C16) from influent and effluent wastewater and river water samples. Nonionic surfactants in the coacervate were directly separated and quantified by liquid chromatography-ion trap mass spectrometry. Concentration factors were around 160. The recovery of nonionics in the environmental water samples ranged from 90 to 104%.

Gas chromatography-mass spectrometry following pressurized hot water extraction and solid-phase microextraction for quantification of eucalyptol, camphor, and borneol inChrysanthemum flowers

Chrysanthemum flower is a common traditional Chinese medicine (TCM). In this work, pressurized hot water extraction (PHWE) followed by headspace solid-phase microextraction (HS-SPME) and GC-MS was developed for the determination of three main active volatile compounds of eucalyptol, camphor, and borneol in Chrysanthemum flowers from four different growing areas in China by internal standard method. The parameters of PHWE and HS-SPME were optimized. The method was also validated. The results showed that PHWE-SPME-GC-MS is a simple, rapid, efficient, and solvent-free technique for the quantitative determination of eucalyptol, camphor, and borneol in TCMs and is potentially useful for the TCM quality assessment.

Amperometric tyrosinase biosensor based on polyacrylamide microgels

An amperometric enzyme sensor using tyrosinase (PPO) entrapped in polyacrylamide microgels has been developed for determination of phenolic compounds. Polyacrylamide microgels were obtained by the concentrated emulsion polymerization method. The crosslinking of the polymer matrix optimum to retain the enzyme and to allow the diffusion of the compounds involved in the enzyme reaction has been studied (4.0%) as well as the influence on the response of analytical parameters such as pH, temperature, enzyme load and working potential. The useful lifetime of the biosensor was 27 days and it was useful to determine monophenolics compounds (e.g. cresol, chlorophenol) and diphenolics compounds (e.g. catechol and dopamine) by amperometric measurements at -100mV (versus SCE) in a batch system. The results showed that the substrate structures have a great influence on the sensor response.

Pressurized hot water extraction of bioactive or marker compounds in botanicals and medicinal plant materials

To reduce the use of organic solvent, pressurized hot water extraction (PHWE) has been shown to be a feasible option for the extraction of bioactive and marker compounds in botanicals and medicinal plants. The parameters that may affect the extraction efficiencies in PHWE include temperature, extraction time and addition of small percentage of organic solvent or surfactants. Currently, applications of PHWE for the extraction of thermally labile compounds in botanicals are still rather limited. PHWE with and without the additional of a small percentage of organic solvent such as ethanol is highly suited for the chemical standardization and quality control of medicinal plants. At the same time, it can be applied at the pilot scale as a manufacturing process for medicinal plants. Surfactant assisted PHWE was found to enhance the extraction of thermally labile and more hydrophobic species in medicinal plants at a lower temperature. The addition of small amount of surfactants in PHWE is highly suited for the determination of bioactive or marker compounds in medicinal plants. With proper optimization, PHWE was observed to have good extraction efficiency and precision when compared to other reference methods of extraction.

Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants

Recent advances in the CE and CEC separation, detection, and sample preparation methodologies applied to the determination of a variety of compounds having current or potential environmental relevance have been overviewed. The reviewed literature has illustrated the wide range of CE applications, indicating the continuing interest in CE and CEC in the environmental field.