Synthetic colorants extraction methods

A sequential analysis protocol includes three steps (1) extraction in water or other appropriate solvent for the colorant, (2) purification or concentration of the colorant, and (3) separation coupled with detection of the target molecule. Different methods of extracting synthetic colorants from foods have been developed using organic solvents followed by SPE protocols using as adsorption support RP-C18, amino materials, or Amberlite XAD-2. Eor qualitative evaluations, the easiest option for separating colorant molecules from unwanted ingredients found in an extract is SPE on polyamide or wool. 

Relevant Methods for Extracting, Separating, and Identifying Synthetic Colorants... 

The identification of synthetic colorants (pure or mixtures) in foods is usually carried out using spectrophotometry but the resolution of complex mixtures in food requires a previous separation of extract components by SPE and chromatographic techifiques. Dual wavelength, solid phase, and derivative spectrophotometric methods combined with chemometric approaches have been used. ... 

All these methods give similar results but their sensitivities and resolutions are different. For example, UV-Vis spectrophotometry gives good results if a single colorant or mixture of colorants (with different absorption spectra) were previously separated by SPE, ion pair formation, and a good previous extraction. Due to their added-value capability, HPLC and CE became the ideal techniques for the analysis of multicomponent mixtures of natural and synthetic colorants found in drinks. To make correct evaluations in complex dye mixtures, a chemometric multicomponent analysis (PLS, nonlinear regression) is necessary to discriminate colorant contributions from other food constituents (sugars, phenolics, etc.). 

A calibration set containing between 7-9 gg mL of Apt, 1-3 gg mL" of Ace-K, and 2-4 gg mL of Sac was used. The designed and optimized training set of calibration was applied to the determination of three sweeteners of several synthetic mixtures. The method was also applied to commercial drinks and satisfactorily results were obtained. The procedmes do not require any separation step for colorless sample (powder drink), but only an extraction step for colored beverages (powder and liquid) was used. The effect of cyclamate (CA) and ascorbic acid (AA) was also investigated. 

Polyamide powder has been proposed in batch experiments for the extraction and HPLC-DAD determination of Sunset Yellow and 13 other synthetic food colorants in fish roe and caviar [23]. This extraction method obtained better recovery rates than other solid materials (AI2O3, XAD-2, anion exchangers) also tested in this work. The sample preparation proposed by Kirschbaum consisted of the extraction of colorants from roe with 1 M aqueous ammonia, defatting with n-hexane, adjustment of the extract to pH 2, adsorption of colorants on polyamide, and desorption with a mixture of aqueous ammonia (25% v/v) and methanol (10 90% v/v) [23]. 

Five synthetic and five natural colorants were identified and quantified in lyo-philized dairy products and fatty foods using an automatic method based on solid phase extraction using a stationary phase followed by RP-HPLC C,g columns for the sequential retention of colorants and diode array detection. Lyophilization of the samples coupled with the separation procedure provided clean extracts despite the complexity of the food matrices and preserved the sample for at least 2 months without changes in colorant concentrations. The detection limits achieved for the colorants were found in a wide range from 0.03 to 75 pg/g of the lyophilized sample, according to the limits established by the European Union. ... 

The principle behind the test method(s) is that antibodies are made of proteins that recognize and bind with foreign substances (antigens) that invade host animals. Synthetic antibodies have been developed to complex with petroleum constituents. The antibodies are immobilized on the walls of a special ceU or filter membrane. Water samples are added directly to the cell, while soils must be extracted before analysis. A known amount of labeled analyte (typically, an enzyme with an affinity for the antibody) is added after the sample. The sample analytes compete with the enzyme-labeled analytes for sites on the antibodies. After equilibrium is established, the cell is washed to remove any um-eacted sample or labeled enzyme. Color development reagents that react with the labeled enzyme are added. A solution that stops color development is added at a specified time, and the optical density (color intensity) is measured. Because the coloring agent reacts with the labeled enzyme, samples with high optical density contain low concentrations of analytes. Concentration is inversely proportional to optical density. 

Pine oil n. Colorless to amber colored volatile oil with characteristic pinaceous odor, consisting principally of isomeric tertiary and secondary cyclic terpene alcohols, with variable quantities of terpene hydrocarbons, ethers, ketones, phenols and phenolic ethers, the amount and character of which depend on the source and method of manufacture. The four commercial kinds of pine oil are (1) Steam distilled pine oil. Obtained from pine wood by steam distillation or by solvent extraction followed by such distillation. (2) Destructively distilled pine oil. Obtained from the lighter distillate from the destructive distillation (carbonization) of pine wood. (3) Synthetic... 

The pH-differential method is of special importance for investigations of anthocyanins suspectedly adulterated with synthetic red food colorants. Adulteration with synthetic food colorant is overlooked by the simple UVA IS measimement described before as those food colors are stable imder extraction/hydrolysis conditions and may add substantial absorption at 510-540 mn masking perfectly the lack of anthocyanins. 

For confirmatory purposes, aqueous bilberry extract solutions resulting fi om the test protocol of the pH-differential method were injected onto a HPLC system used in om- laboratory for the determination of synthetic food colorants (adopted from [138]). 

The conditions used were ethyl acetate-glacial acetic acid-formic acid-water (100 11 11 26 v/v/v/v) as mobile phase and silica gel (F 254) as stationary phase [159]. Likewise, for qualitative analysis of elderberry silica gel (F 254 run) developed with hexane-ethyl acetate (8 2, v/v) and anisaldehyde solution as spray reagent were used [160]. Only recently a new method for detection of synthetic food colorants in bilberry extract with High Performance Thin Layer Chromatography has been published [161]. 

Vanilla extracts are very expensive flavorants the composition of which is defined in the U.S. legislation. However, to satisfy a user demand, numerous products are offered that contain both natural extract and synthetic vanillin or other flavoring chemicals having a flavor resembling or compatible with that of vanilla. Such products are much cheaper than the authentic material and the problem of establishing the authenticity of vanilla extracts has been the subject of much research over the past 30+ years. Traditionally, tests concentrated on vanillin content, color, lead number and organic acid content, but these could quite easily be circumvented. This has lead to the development and use of very sophisticated methods of monitoring adulteration. 

Cmde dried or fresh herb, fresh or dried flowers in olive oil, extracts, tinctures, synthetic hypericin, and so on. Hypericum oil, prepared by maceration of fresh flowers in sunlight for several weeks (usually in olive oil) acquires a red hue usually ascribed to hypericin or lipophilic substituted compounds with a hypericin-like color and fluorescence. Hyperforin is found in freshly macerated oil but is unstable, breaking down within 30-90 days stability can be increased to 6 months in storage by excluding air and using alternate preparation methods. ... 

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