Pigments purifying samples

Fractions are concentrated under vacuum below 35°C. Alternatively, they can be purified and concentrated by solid phase extraction (SPE) before identification and quantification, which is a valuable procedure for samples containing low amounts of pigments. After concentration, fractions can be stored in small flasks, protected from light, sealed under inert atmosphere, and kept below -20°C until analysis. 

Store purified anthocyanin extract at 4°C if subsequent analysis will be performed within 24 hr. Store sample for longer periods at -15°C or lower (preferably at -70°C) in a freeze-resistant container to minimize pigment degradation. 

These materials, the original galena, the refined lead metal, lead oxide, glass, and pigment were put into solution. The lead was purified by anodic electrodeposition and was analyzed by a mass spectrometer using previously published procedures (6). The results of the measurements of the isotopic ratios of the above samples are shown in Table II. 

The resulting purified material is more stable than the impure samples and could be characterized by a variety of spectroscopic and chemical conversion techniques. In addition, an assay of crude blood-cell extract for the presence of tunichrome was developed (162). Tunichrome blood pigments consist of a number of closely related polyphe-nolic compounds with a central triglycyl unit (Fig. 5). A tunichrome (designated An-1) isolated from the species A. nigra, for example, of... 

Pigment purification. Port wine samples were directly applied on a 250 x 16 mm i.d. Toyopearl HW-40(s) gel column (Tosoh, Japan) at a flow rate of 0.8 mL/min. A first elution was performed with 20% aqueous ethanol yielding fi action A. When practically no more colored compounds were eluted from the column, the solvent was changed to 99.8% aqueous ethanol yielding fraction B. The pH of alt the eluents was set to 2.0 with HCl. The major pigments reported in each fraction were purified by semi-preparative HPLC on a 250 x 4.6 mm i.d. reversed-phase C18 column (Merck, Darmstadt) using an injection volume of 500 pL, as described elsewhere 21). 

Two examples of modern clean-up methods that use columns that have been prepared commercially are the Extube (Analytichem International) and the Sep-Pak (Waters). The Extube was designed to isolate drugs from a complex biological sample by the principle of liquid-liquid extraction. Samples to be analyzed, such as urine, whole blood or bile, are introduced into a disposable Extube, which is packed with an inert fibrous matrix of large surface area. When a suitable solvent is poured into the Extube, it interphases film-on-film with the sample. The compound of interest is extracted by a solvent that passes freely through the matrix, whereas impurities such as water, pigment, particulate matter and other polar components are retained by the matrix. The Extube has been used to extract and purify cortisol from plasma by liquid-liquid partition with methylene chloride [40]. The Sep-Pak... 

Identification of plastics [34] is carried out by a systematic procedure preliminary test, detection of elements, determination of characteristic values, and, finally, specific tests. For an exact identification, however, the test sample should first be purified so that it contains no additives (plasticizers, fillers, pigments, etc.) that may affect the results of an analysis. Purification is achieved by solvent extraction either the material is dissolved out and polymer is obtained by reprecipitation or evaporation of the solvent, or the pure polymer remains as the insoluble residue. The solvent varies, and a general method cannot be given. However, for many materials particularly for those in which additives do not interfere, the unpurified material can be investigated and qualitative preliminary tests used. 

In some cases, purification steps are included in the procedure. For example, paint samples that contain interfering pigments need to be purified in order to identify proteinaceous binders on the basis of the quan-... 

Traditionally, UV-Visible spectra have been obtained in solution. Quantitative analysis is obtained based on the Beer-Lambert law. For quantitative analysis by solution spectrophotometry the colorant must be completely dissolved and other components in the sample must not interfere with the determination. In addition, purified standards containing known amounts of the pigment being determined are required. Since HPOPs are highly insoluble, strong organic solvents or concentrated sulfuric acid are usually employed in order to effect complete dissolution of the pigment. 

For quantitative analysis by solution spectrophotometry the colorant must be completely dissolved and other components in the sample must not interfere with the determination. In addition, purified standards containing the known amount of pigment being determined are required. 

Recently, a very useful method for fabrication of TBPs for OFETs has been developed. TBPs are a new semiconductor for OFETs, compared to Pcs. TBPs and Pcs are pigments (insoluble in organic solvents) and it is not easy to get pure samples. Ito et al. have found that heating a porphyrin (CP) fused with bicyclo[2.2.2]octadiene (BCOD) gives TBP in quantitative yield (Scheme 3) [125]. As CPs are soluble in organic solvents, they are purified by column chromatography. 

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