Detection of lipophilic substances

Nondestructive Dection Using Other Physical Methods 43 Table 7. Nondestructive detection of lipophilic substances with water as detecting reagent. 

Table 8. Employment of fluorescent substances for the nondestructive detection of lipophilic substances.

In the same way aqueous dye solutions, like methylene blue or patent fast blue, are employed instead of water. Lipophilic substances, like anion active detergents, appear pale on a transparent blue background. This phenomenum is contrary on RP phases. The lipophilic part of the detergent is aligned with the RP chains, whereas the hydrophilic part is colored by the dye, and therefore deeply colored blue zones appear on a pale backgound. Using lipophilic dye solutions for the detection of lipophilic substances on a hydrophilic phase yields dark zones on a pale background. 

Both cell culture with a lipophilic extraction phase and with a polar extraction phase have been reported to be helpful for the accumulation and detection of secondary substances [7,8]. Plant cell cultures release lipophilic and volatile substances such as ethylene, ethanol, and acetaldehyde. The addition of a lipophilic phase to the culture medium can be used as a means of accumulating and detecting these substances. Maisch et al. [8] found that the addition of XAD-4 resin to Nicotiana tabacum cultures enhanced the production of phenolic secondary metabolites several times compared to the adsorbent-free control. Kim and Chang [9] reported in situ extraction for enhanced shikonin production by Lithospermum erythrorhizon. When n-hexadecane was added to the cultivation, higher specific shikonin productivity was obtained than that from the cultures of free cells without extraction. They also suggested that n-hexadecane addition at an early stage in calcium alginate immobilized cell cultures was effective for shikonin production. Most of the produced shikonin was dissolved in n-hexadecane, so it would reduce the costs for shikonin separation. 

Spots of lipophilic substances can he detected by spraying with water this depends on the different wetting properties of adsorbent and substance. Detection is easiest in transmitted light. This method, which has been used occasionally to detect steroids [39, 70, 212, 794], is generally too insensitive. 

Treatment of the solvent-free chromatogram with iodine vapor or by dipping in or spraying with iodine solution (0.5 — 1%) is a rapid and economical universal method of detecting lipophilic substances. Molecular iodine is enriched in the chromatogram zones and colors them brown. 

Since DEHP is a lipophilic substance, it has the potential to accumulate in maternal milk and be transferred to suckling offspring. Both DEHP (216 pg/mL) and MEHP (25 pg/mL) were detected in the milk collected from lactating Sprague-Dawley rats 6 hours after the last of three daily gavage doses of 2,000 mg DEHP/kg (Dostal et al. 1987b). At this time, no DEHP could be detected in dams plasma, but substantial amounts of MEHP were detected. Pups plasma had no detectable DEHP or MEHP. No other dose levels were tested in this study. Dostal et al. (1987b) noted that exposure to DEHP was associated with an increase in milk solids and lipids. Addition of 14C-DEHP to milk in vitro resulted in 94% of the... 

Exposure. Because DEHP is rapidly metabolized and excreted, it is difficult to monitor anything but recent human exposures through the body fluids. MEHP and several oxidized MEHP metabolites can be measured in blood and urine and are biomarkers of exposure, and DEHP has been detected in human milk. Since DEHP is a lipophilic substance, it has the potential to deposit in adipose tissues. More chronic exposures can be detected with a fat biopsy, but there are no validated approaches for assessment of chronic exposure by fat biopsy analysis. Additional studies of methods for monitoring DEHP exposure would be of value. 

The fatty/waxy products contained the lipophilic substances, including fatty oils, waxes, resins and colorants. Valuable pharmacological effects were proved for some minor constituents of these products (e.g. triterpenes, diterpenes, sterols and carotenoids). Thin layer chromatography and on-line UV-VIS spectroscopy were used for the quick identification and quantity determination of these compounds using authentic samples as standards. The SFE method proved favorable in terras of both extraction yield and speed of carotenoids. The CO2 extracts of the lavandin, clary sage and thyme have been enriched in triterpenic compounds (a-es P-amyrin, oleanic acid, ursolic acid, etc.) and phytosterols. Both free and esterified triterpenoids were present in the extracts of the different samples. Furthermore camosol and other diterpenes were detected in the SFE extract of Lamiaceae plants. The fatty acid composition was only slightly different for extracts obtained by SFE and conventional hexane extraction. 

The papers dealing with the GC/MS detection of 10 different opiates in hair are listed in Table 7. The first report was published in 1984 about codeine detection in animal hair after administration of the drug. One paper is included with direct insertion of the probe and Cl. As heroin samples always contain codeine as an impurity, this substance also can be detected in cases of heroin abuse. Morphine is a metabolite of codeine and can be detected when codeine is abused. The quantitation of both drugs allows differentiation between codeine and heroin abuse. The detection of heroin or 6-acetylmorphine opens the possibility to prove directly the abuse of heroin.2 2" Here also, the more lipophilic 6-acetylmorphine exceeds the morphine in most samples. 

Coal tar is composed of hydrocarbons, which are lipophilic substances and are therefore likely to distribute to lipid-rich tissues (Agency for Toxic Substances and Disease Registry 1995). For instance, PAHs and their metabolites are known to cross the placenta (Agency for Toxic Substances and Disease Registry 1995) and have been detected in human breast milk (Madhavan and Naiduka 1995). A study of the distribution of intratracheally administered radioactive benzo[a]pyrene mixed with a benzene extract of coal fly ash in pregnant rats found that a small proportion of the radioactivity was distributed to the fetal lung and liver and to the placenta (respectively 1.9, 1.4, and 4% of the amount in maternal lung). 

Fractionation of the material is recommended because certain substances interfere with some detection methods. Percolation with petroleum ether removes lipophilic substances. Proteins and mucilages can be removed by precipitation with metal ions or 5% (w/v) trichloroacetic acid (TCA). Discoloration of biological materials is achieved with charcoal. Owing to the insolubility of benzylidine derivatives of sugar alcohols in water, they can easily be crystallized and purified from adhering matter by washing with water. 

Applications. Acetylated cellulose powder is in principle suitable for separation of all lipophilic substances. Separation alone is not enough however the separated substances must be detectable. This fact has been responsible for the relatively modest extent of application of Ac-cellulose layers. They may be recommended for coloured substances and for those which are detectable in UV light. Some examples of use are separation of polynuclear aromatic compounds [31, 309, 357, 599, 600, 755], anthraquinone dyes [768], antioxidants [596], cutin acids [98], sweetening materials [595], rhodanine derivatives of acetoacetic acid and acetone in urine [574] and ketocarboxylic acids [575]. 

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