Quantification of β-carotene, retinol, retinyl acetate and retinyl palmitate in enriched fruit juices using dispersive liquid–liquid microextraction coupled to liquid chromatography with fluorescence detection and atmospheric pressure chemical ionization-mass spectrometry

Swellable Sorbent Coatings for Parallel Extraction, Storage, and Analysis of Plant Metabolites

Quantitative and qualitative measurements of trace-level analytes in plants or foodstuffs, e.g., secondary metabolites like carotenoids, are often performed at centralized core facilities or off-site laboratories. However, preparation, storage, and/or transport of both intact samples and sample extracts may be cumbersome and complicated, especially for air-sensitive analytes. We describe the development of inexpensive swellable microextraction (SweME) devices for extraction and storage of nonpolar analytes. SweME devices consist of a thin layer of poly(dimethylsiloxane) (PDMS) grafted onto a stainless steel support. Pretreating the SweME device with small volumes of the organic solvent causes the PDMS to swell. The swollen SweME device can then be immersed directly into complex matrices for absorptive extraction of low-molecular-weight, nonpolar analytes. Following storage, analytes can be solvent-desorbed prior to characterization. Proof-of-principle work with carotenoids from tomatoes and carrots demonstrates that SweME is appropriate for semiquantitative analyses and increases the stability of air-sensitive analytes during storage at ambient temperatures as compared to the solvent extracts. Carotenoid profiles (fractional carotenoid contributions) from tomato and carrot samples were well correlated between SweME and liquid-liquid extraction (R² = 0.97 and 0.94). Lycopene, the most abundant carotenoid in tomatoes, saw a less than 20% decrease in extracted mass during 1 month of ambient SweME storage. Extractions and desorptions can be run in parallel using multiwell plates. In summary, swelled sorbent extraction with SweME devices is a convenient and inexpensive approach for isolation and storage of analytes in complex matrices and may be particularly well suited for evaluating large numbers of plant samples through external laboratories.

A fast and simple method for determination of β-carotene in commercial fruit juice by cloud point extraction-cold column trapping combined with UV-Vis spectrophotometry

Cloud point extraction with cold column trapping (CPE-CCT) was used for the rapid preconcentration and UV-Vis spectroscopy of beta-carotene in fruit juice samples. A central composite design was employed to optimize parameters such as pH, incubation time, cloud point temperature and surfactant concentration. A detection limit of 0.01 mg/L of beta-carotene (3S_B/m), a coefficient of determination of 0.998 and a linear range of 0.04-10 mg/L were obtained. The CPE-CCT method was confirmed in comparison with the corresponding direct HPLC standard method. A simple, portable and cost-effective device was also utilized. Owing to eliminating centrifugation, the conditions of CPE-CCT were more moderate and its sample handling easier compared to conventional CPE.

A Dispersive Liquid-Liquid Micro-Extraction Technique for the Pre-concentration and Quantification of Vitamin D3 in Milk and Yogurt Samples Using a Non-Aqueous HPLC Method

In present study, a DLLME-HPLC-UV method was developed and validated for the extraction, pre–concentration, and subsequently quantification of vitamin D₃ (Vit D₃) in milk and yogurt samples. In order to be able to extract Vit D₃ from studied samples efficiently, the DLLME procedure was optimized with respect to the parameters affecting the extraction efficacy, where acetonitrile (2 mL as disperser solvent) resulting from the protein precipitation procedure was mixed with 80 µL carbon tetrachloride (as an extraction solvent) respectively. The extracted samples were quantitatively analyzed with a HPLC technique using a C₈ column (250 mm × 4.6 mm, 5 μm) at room temperature (25 °C), mobile phase of acetonitrile/methanol (90:10% v/v) in isocratic elution mode at a flow rate of 1.2 mL/min and UV detection at 265 nm. The method validation results revealed that the method was linear in the concentration range of 2 to 60 ng/mL (r = 0.9997) with a LOD of 0.9 ng/mL and LLOQ of 2 ng/mL; the method was accurate (-2.1% ≤ RE% ≤ +0.6%) and precise (1.2% ≤RSD% ≤ 11.3%) and its recovery was in the range of 86.6 to 113.3%. The obtained results indicated that the method could be utilized as an easy to use technique for the monitoring Vit D₃ in dairy products, especially milk and yogurt samples.

Effect of seaweed supplementation on tocopherol concentrations in bovine milk using dispersive liquid-liquid microextraction

A dispersive liquid-liquid microextraction (DLLME) method, combined with HPLC-UV detection, was developed for the extraction and preconcentration of δ-tocopherol from bovine milk. This method was used to study the effect of supplementing cow feed with the seaweed Ascophyllum nodosum on vitamin content in milk. The optimal experimental conditions were determined: 200 μL of chloroform (extraction solvent), 1.0 mL of ethanol (dispersive solvent), 5 mL of water (aqueous phase). Under these optimal conditions the DLLME method provided linearity in the range 0.01 μg/mL to 8 μg/mL with R² values of 0.998. Limit of detection (LOD) was 0.01 μg/mL, while the enrichment factor was 89. Cow feed that was supplemented with Ascophyllum nodosum was shown to increase δ-tocopherol levels from 3.82 μg/mL to 5.96 μg/mL.

Key blackening and stinking pollutants in Dongsha River of Beijing: Spatial distribution and source identification

Elimination of black-stinking water contamination has been listed as an urgent task in the Water pollution prevention action plan promulgated by State Council of China. However, the key blackening and stinking pollutants and their sources are still unclear. In this study, water quality of a black-stinking urban river in Beijing, Dongsha River, was evaluated firstly; then the distribution of the blackening and stinking pollutants was investigated, and the key pollutants and their potential sources were identified; and finally, the health risk of those pollutants was assessed. The results showed that NH₃N, total phosphorus, dissolved oxygen and chemical oxygen demand ranged from 1.3 to 5.3 mg/L, 0.7-3.0 mg/L, 1.0-3.2 mg/L and 29-104 mg/L, respectively. The value of TP-based trophic level index indicated that Dongsha River reached severe eutrophication level; the maximum value of chroma and odor level reached 32 and 4, respectively. The main dissolved organic compounds included aromatic protein II, soluble microbiological metabolites, fulvic acids and humic acids. The blackening pollutants Fe, Mn, Cu and S^2- were extensively detected, with significantly spatial differences along the river. Dimethyl sulfide, β-ionone, 2-methylisoborneol and geosmin were identified to be the stinking pollutants. Their concentrations covered wide ranges, and even the lowest concentration value was thousands of times higher than its olfactory threshold. Correlation analysis indicated that in the overlaying water S^2- was the key blackening pollutant, while β-ionone and geosmin were the key stinking pollutants. Principal components analysis combining with the site survey revealed their potential sources. S^2- was mainly associated with the decomposition of endogenous sulfur-containing organics; β-ionone might be generated by the endogenous β-carotene bio-conversion and the exogenous discharges, while geosmin might originate from the endogenous humus bio-conversion and anthropic wastes. Furthermore, multi-metals in the sediment posed health risks to children, while dimethyl sulfide had non-cancer health risk for adults and children.

A novel extraction method for β-carotene and other carotenoids in fruit juices using air-assisted, low-density solvent-based liquid-liquid microextraction and solidified floating organic droplets

Green extraction using air-assisted, low-density solvent-based liquid-liquid microextraction and solidified floating organic droplets (AA-LDS-LLME-SFOD) prior to spectrophotometry was successfully applied for quantitation of carotenoids in fruit juices. Under optimal conditions, β-carotene could be quantified with a linear response up to a concentration of 60 μg mL(-1). The procedure was performed in a microcentrifuge tube with 40 μL of 1-dodecanol as the extraction solvent and a 1.0 mL juice sample containing 8% NaCl under seven extraction cycles of air pumping by syringe. This method was validated based on linearity (0.2-30 μg mL(-1), R(2) 0.998), limit of detection (0.04 μg mL(-1)) and limit of quantification (0.13 μg mL(-1)). The precision, expressed as the relative standard deviation (RSD) of the calibration curve slope (n=12), for inter-day and intra-day analysis was 4.85% and 7.92%, respectively. Recovery of β-carotene was in the range of 93.6-101.5%. The newly proposed method is simple, rapid and environmentally friendly, particularly as a useful screening test for food analysis.

Advanced development in phytochemicals analysis of medicine and food dual purposes plants used in China (2011-2014)

In 2011, we wrote a review for summarizing the phytochemical analysis (2006-2010) of medicine and food dual purposes plants used in China (Zhao et al., J. Chromatogr. A 1218 (2011) 7453-7475). Since then, more than 750 articles related to their phytochemical analysis have been published. Therefore, an updated review for the advanced development (2011-2014) in this topic is necessary for well understanding the quality control and health beneficial phytochemicals in these materials, as well as their research trends.

Analytical tools for the analysis of β-carotene and its degradation products

β-Carotene, the precursor of vitamin A, possesses pronounced radical scavenging properties. This has centered the attention on β-carotene dietary supplementation in healthcare as well as in the therapy of degenerative disorders and several cancer types. However, two intervention trials with β-carotene have revealed adverse effects on two proband groups, that is, cigarette smokers and asbestos-exposed workers. Beside other causative reasons, the detrimental effects observed have been related to the oxidation products of β-carotene. Their generation originates in the polyene structure of β-carotene that is beneficial for radical scavenging, but is also prone to oxidation. Depending on the dominant degradation mechanism, bond cleavage might occur either randomly or at defined positions of the conjugated electron system, resulting in a diversity of cleavage products (CPs). Due to their instability and hydrophobicity, the handling of standards and real samples containing β-carotene and related CPs requires preventive measures during specimen preparation, analyte extraction, and final analysis, to avoid artificial degradation and to preserve the initial analyte portfolio. This review critically discusses different preparation strategies of standards and treatment solutions, and also addresses their protection from oxidation. Additionally, in vitro oxidation strategies for the generation of oxidative model compounds are surveyed. Extraction methods are discussed for volatile and non-volatile CPs individually. Gas chromatography (GC), (ultra)high performance liquid chromatography (U)HPLC, and capillary electrochromatography (CEC) are reviewed as analytical tools for final analyte analysis. For identity confirmation of analytes, mass spectrometry (MS) is indispensable, and the appropriate ionization principles are comprehensively discussed. The final sections cover analysis of real samples and aspects of quality assurance, namely matrix effects and method validation.