Extraction tests, for the presence

Bioassay of Extracts. Extracts tested for the presence of cyclohexi-mide were also bioassayed for phytotoxicity. The extracts were redis-sOlved in acetone, and 0.2 mg in 2 pi was applied to 6-cm-dia disks of filter paper. The extract was distributed on the paper with 0.2 ml of methanol. The disks were dried with warm air, placed in 1.5 x 6 cm petri dishes, and moistened with 1.5 ml distilled water. Ten cress seeds were placed on the paper, and after incubation for 3 d at 28 C radicle length of the seedlings was measured. 

Samples first were washed in water with manual agitation in a Buchner funnel and then were successively rinsed with methanol, chloroform, methanol, and water. During this process, particulate debris separated from the fibers, and it was assumed that loosely attached water-, methanol-, and chloroform-soluble impurities largely washed out with the filtrate. Preliminary extraction tests for the presence of synthetic dyes were conducted as follows Samples were first boiled in water. If the solution colored, the water extract was analyzed with HPLC, and the sample was then boiled in dilute ammonia. If the ammonia extracts were strongly colored (natural dyes with the exception of very few do not extract into water or dilute ammonia), they were shaken with zinc dust, and if the ammonia extract reduced to a completely colorless solution, it was concluded that the sample was an azo dye (I). Early synthetic dyes often bleed into boiling water, and azo groups will reduce in the presence of zinc dust. 

For the tests described below use for acid extraction the residue in the alundum crucible from the water (or water-alcohol) extraction, as described in step 6 of "Standard Method No 32" Before proceeding with the extraction, test for the presence of starch in the above residue by placing a small portion in a 50-ml beaker, adding 10 ml of distd w and bringing it to a boil. Then cool and add a drop of iodine (1 in methanol) so In. Appearance of a blue color indicates the presence of starch Note A Rice hulls may give a faint starch test from small rice particles, and corn meal will give a positive test also. Determine the presence of these materials by examination of the sample to be extracted... 

Trichloroethanoic acid, CCI3COOH. A crystalline solid which rapidly absorbs water vapour m.p. 58°C, b.p. 196-5" C. Manufactured by the action of chlorine on ethanoic acid at 160°C in the presence of red phosphorus, sulphur or iodine. It is decomposed into chloroform and carbon dioxide by boiling water. It is a much stronger acid than either the mono- or the dichloro-acids and has been used to extract alkaloids and ascorbic acid from plant and animal tissues. It is a precipitant for proteins and may be used to test for the presence of albumin in urine. The sodium salt is used as a selective weedkiller. 

Diagnostic tests for the presence of HP can be either endoscopic or non-endoscopic. Endoscopic diagnosis requires the extraction of gastric tissue samples that are subsequently tested for... 

The ether extract and the water layer may be tested for the presence of /3-tetralone or the bisulfite addition product by the tetralone blue test. 

Hydrophobic Base Fraction. The hydrophobic base fraction was adjusted to pH 10. A 50-/uL aliquot of the aqueous solution was subjected to HPLC analysis to test for the presence of 5-chlorouracil. The remaining aqueous solution was solvent extracted with methylene chloride. The extract was first concentrated in a Kudema-Danish apparatus, then under a stream of N2, and analyzed by GC-FID and GC-MS. 

A third test for the presence of halogens consists in heating the compound along with an excess of pure lime in a glass tube. The mass is afterwards extracted with water, and tested with silver nitrate. 

Another major problem associated with the extraction of DNA from archaeological specimens is that the procedure often co-extracts impurities that can later complicate, or prevent, the study of the extracted DNA by inhibiting PCR amplification (reviewed by 5). Commonly encountered inhibitory substances found in aDNA extracted from teeth, bones, mummified tissue, and coprolites include humic acids, ftilvic acids, tannins, porphyrin products, phenolic compounds, hematin, and collagen type I (37—42). The formation of Maillard products, commonly encountered in coprolite samples, can also prevent PCR amplification by causing DNA to become inaccessibly trapped in these sugar-derived condensation products (12). As the negative results in many aDNA studies are attributed to the presence of PCR inhibitors, our extraction method outlined below pays particular attention to the problem and offers a simple test for the presence of PCR inhibitors in DNA extracts. 

If an aDNA extract frails to PCR amplify it should be tested for the presence of PCR inhibitors. This test requires the availability of an authenticated aDNA sample to be used as a positive control.8 Set up side-by-side PCR reactions containing 1) the template suspected to contain inhibitors, to which is added a volume of the ancient positive control equivalent to that of the template, 2) only the template suspected to contain inhibitors and 3) only the positive ancient control. This side-by-side comparison will allow for the preclusion of PCR failure due to factors other than inhibition (e.g. the stochastic nature of PCR amplification). If the template spiked with the positive ancient control (reaction 1) permits its amplification, while the template suspected of containing inhibitors (reaction 2) fails to amplify, the template is likely free of inhibitors and, therefore, does not contain a sufficient amount of DNA for analysis. Alternatively, if the first PCR reaction fails to amplify, whereas the third reaction does amplify, the template is concluded to contain inhibitors. In this case, the silica extraction should be repeated, as described above, and PCR reattempted. Our studies have shown that as may as four repeat silica extractions may be required to sufficiently remove PCR inhibitor from DNA extracts, despite the inherent loss of DNA yield associated with each repetition of the silica extraction (5). 

UVA lS-spectroscopy is commonly used in the quality control laboratories of the flavour industry particularly for those products where colour characteristics are important. The possible measurement of the absorption or transmission of the samples in wavelength maxima as well as the intake of a spectrum over the entire wavelength area between 250-800 nm is important for the routine check of colour identity. By constant measuring parameters (cuvette, dilution, etc.) exact evidence of the colour intensity can be established. This analysis is very important for coloured flavouring preparations, fruit- and plant extracts or essential oils with colouring properties, as well as for testing for the presence of non permitted colouring materials [1],... 

If, on boiling with ammonia, virtually no colour migrates into the liquor, a mordanted or premetallized dye is probably present. This is confirmed by testing for the presence appropriate metallic ions. To do this the material must be ashed, and the method recommended by Clayton is to heat about 1 sq in., if possible, in a platinum or silica dish until charring has taken place. The dish is then cooled and the residue is covered with a hot saturated solution of sodium nitrate, the water is evaporated, and heating is continued until all the carbon has burned away. The ash is extracted with water or dissolved with the aid of a little hydrochloric acid, and the usual qualitative tests for metallic ions are applied. 

In many cases, however, the saprophytic cultures of ergot described in the literature were tested for the presence of ergot alkaloids not only by means of color reactions, but also by biological methods (e.g. uterotonic activity). Nevertheless, when applied to complex material such as culture filtrates or extracts of mycelium, these methods of examination cannot be regarded as specific either, since other substances, e.g. histamine, also exert a more or less marked uterotonic action. 

There is actually no field test for psilocybin mushrooms. There is however, a relatively simple test for the presence of psilocin and psilocybin that can be carried out at home by anyone who has some familiarity with paper chromatography. The mushroom sample is dried, pulverized, and extracted into a small amount of unheated methanol by shaking for half an hour. After the debris in the methanol has settled the paper is spotted with the top fluid in a zone about 2mm. 

In a companion study, M. Palma et al. studied the extraction of grape seeds with pure SF CO2 and analyzed the derivatized extracts by GC-MS. These extracts were found to contain volatiles such as aliphatic aldehydes in addition to fatty acids and sterols. Even though we used similar conditions for our SF extraction and GC-MS analysis, we were unable to detect any similar volatile compounds. To further investigate the presence of volatiles in the cranberry seed extract, we adapted a solid phase microextraction (SPME) method from the work of Jelen et al. who had earlier developed it for the characterization of volatile compounds in different vegetable oils. SPME followed by gas chromatog[raphy was performed on the headspace of the cranberry seed extract to test for the presence of volatile compounds. The GC trace failed to show the elution of any components for either the SF or Soxhlet extract. 

Hexane Extraction and Bromination. Some of the fluorescent enones are extractable from the amorphous regions of the polymer matrix by cold hexane (1,13). This prpcess enables us to perform a simple chemical test for the presence of unsaturation, i.e., bromination (18). Figure 4 shows the fluorescence excitation and emission spectra of the cold hexane extract of commercial polypropylene before and after treatment with bromine. After bromination there is a significant reduction in the fluorescence intensity, confirming the presence of unsaturation. A similar result was obtained on brominating a cold hexane extract of poly-4-... 

At this stage a cursory test for the presence of alkaloids in the extract is in order. Mayer s reagent (potassium mercuric iodide solution) has proved very satisfactory, for it yields a precipitate with virtually all alkaloids. Unfortunately, the formation of precipitates by this reagent is not diagnostic for this group of natural products alone since plant extracts which are entirely free of alkaloids often give precipitates. Hence a positive test with this reagent must be interpreted with caution. 

However, methods have been developed to test for the presence of ionization suppression or enhancement of an analyte extracted from a complex matrix, to take its effects into account and thus hopefully alleviate the problem or even eliminate it altogether. An early systematic approach (Buhrman 1996), directed at detection and quantification of ionization suppression and other parameters, was later modified (Matuszewski 2003) to take account of the possibihty of ionization enhancement, and this modification is adopted here. The approach compares the results obtained for the mass spectrometric responses (peak areas) in three different LC/MS experiments for a target analyte, using the same known amount of analytical standard at the same final concentration in each case ... 

If unpreso ed ethyl ether is used as a mobile phase constituent, it must be routinely tested for the presence of peroxides. A visual ferrous ammonium sulfate test is conducted as follows [798] SmL 1% ferrous ammonium sulfate (fi eshly prepared), O.SmL IN sulfuric acid, and 0.5mL 0.1 N ammonium thiocyanate ate mixed (and decolorized with a trace of zinc dust if necessary) and shaken with an equal quantity of the ether to be tested. If peroxides are present, a red color develops. This method is significantly more sensitive than the KI test described in Chapter 1. However, inqrroper storage can drastically increase the rate of peroxide formation and present a safety hazard to the user. This is especially true when pre- or postanalysis sanqrle concentration stq>s involve ether (e.g., extractions or preparative LC). 

In most cases, the spleen is the best choice for antigen-specific lymphocyte isolation. The immunization regime used to immunize mice is identical in every respect to that used for conventional hybridoma production. In particular about ten days after each injection, test bleeds should be carried out to test for the presence of specific antibodies and only animals giving the best antiserum should be selected. Do not expect to recover high affinity antibodies from phage antibody libraries that are not foimd in the test serum. Three to five days before harvesting the spleen for RNA extraction, the immunized mouse is given a final boost. This is best achieved by an intravenous injection done concurrently with an intraperitoneal injectiou... 

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