Presence of Other Compounds

The effects of cadmium may be modulated by environmental factors, including salinity and the presence of other compounds. The synergistic inhibition of limb regeneration in the hermit crab Uca pugilator caused by combinations of cadmium and methylmerciiry is only evident in water of high salinity. ... 

Thin-Layer Chromatography. A study using thin-layer chromatography both for separating components of a pyrethrum extract and for purifying single components has been made. Other reports have mentioned the use of thin-layer chromatography in various connections related to pyrethrin analysis. Stahl (14) reported on pyre-thrins I and II and evidence for presence of other compounds from... 

Frequently, the quantitative determination of anthocyanins is comphcated by the presence of other compounds that may interfere with the measurements. It is desirable to express anthocyanin determinations in terms that may be compared with results from different workers. The best way to express the results is in terms of absolute quantities of anthocyanins present. This is necessary to establish the identities of the pigments and their molar absorptivity coefQcients. 

But all these parameters are also sensitive to the presence of other compounds. Therefore, the AIT of ethylene is lower when the walls of a reactor are covered with diboron trioxide. 

Specificity is a measure of how selectively the analytical method measures the marker compound in the presence of other compounds. The descriptors used to establish specificity differ depending upon the guideline (see Table 3), but the purpose behind them is the same. In all cases, the method must be demonstrated to have no interference from several (at least five) confrol animals that represent variation in sex, age, and breed. Further, incurred residue samples or authentic metabolite standards must demonstrate no interference with the marker residue detection. The method must be tested with other approved dmgs for the target species to show that no interference exists if these compounds are also present. 

The major source of lycopene is tomato products but it also occurs in water melons, guavas, pink grapefruit, and in small quantities in at least 40 plants.14 The structure of lycopene is shown in Fig. 8.2. It is a long chain conjugated hydrocarbon and its structure suggests that it would be easily oxidized in the presence of oxygen and isomerized to cis compounds by heat. Both of these reactions occur in purified solutions of lycopene but in the presence of other compounds normally present in tomatoes, lycopene is more stable. Actually the absorption of lycopene in the human gut is increased by heat treatment probably because the breakdown of the plant cells makes the pigment more accessible. Preparations from tomatoes are widely used in pizza, pasta, soups, drinks and any product compatible with the flavor and color of tomatoes. 

The chief limitation of Pourbaix diagrams is that they show only the dominant compound in any particular area. They do not show the presence of other compounds, which may be of comparable concentration nor the fact that the activities of solution species are continuous functions. 

There has also been a report regarding the active transport of antibacterial agents in oral mucosa. In a cell line derived from oral epithelium, the uptake of ciprofloxacin and minocycline was not only saturable and inhibited in the presence of other compounds, but the intracellular levels of both antibiotics were 8 10-fold higher than the extracellular levels as well, demonstrating an active transport process [18]. Whether the permeability of these compounds across the entire oral mucosa occurs via an active transport process, however, remains to be determined. 

The rapid reaction rate of ozone with NOx makes the process highly selective for treatment of NOx in thn presence of other compounds such as CO and SO2. This... 

The selectivity of a method is a measure of how capable it is of measuring the analyte alone in the presence of other compounds contained in the sample. The most selective analytical methods involve a chromatographic separation. Detection methods can be ranked according to their selectivity. A simple comparison is... 

Effect of the Presence of Other Compounds The response (pharmacokinetics and pharmacodynamics) of an individual pharmaceutical compound may be predictable. By comparison, the response of the same compound in the presence of... 

The method was applied on a 6-component mixture of polycyclic aromates. Each compound was quantified, independently from the presence of other compounds, and within the error of preparing standards It means that the method is fully capable to handle unknown and uncorrected interferences. 

The GC-MS methods described here reflect the practice in the laboratory of the author. Organic acids are extracted from biological fluids by liquid-liquid extraction after mixing the specimen with an internal standard solution and a small amount of mineral acid (HC1) to bring the pH to < 2. Oximation of 2-keto acids with hy-droxylamine hydrochloride is not performed routinely, but only as a repeat analysis when the primary analysis reveals an abnormal excretion of 2-keto acids (e.g., lactic acidemia, ketonuria) and the potential presence of other compounds (e.g., glyoxylic acid, succinylacetone). 

Frequently, the qualitative and quantitative analysis of anthocyanins is complicated by the presence of other compounds that may interfere with the measurements. The solvent systems generally used for extraction purposes are by no means specific for anthocyanins (Markakis, 1974 Jackman et al 1987). Purification of anthocyanin-containing extracts is often necessary because considerable amounts of other compounds may also be extracted and concentrated. The variety and levels of other compounds will depend on the solvent and methodologies used. The presence of extraneous materials could influence the stability or analysis of anthocyanins. Therefore, the next step towards anthocyanin characterization is the prefractionation of those extracts. 

Samples, even at moderate concentrations, injected into the HPLC column may precipitate in the mobile phase or at the column frit. In addition, the presence of other compounds (e.g., lipids) in the injection sample may drive the carotenoids out of solution or precipitate themselves in the mobile phase, trapping carotenoids. It is best to dissolve the sample in the mobile phase or a slightly weaker solvent to avoid these problems. Centrifugation or filtration of the samples prior to injection will prevent the introduction of particles that may block the frit, fouling the column and resulting in elevated column pressure. In addition to precipitation, other sources of on-column losses of carotenoids include nonspecific adsorption and oxidation. These can be minimized by incorporating modifiers into the mobile phase (Epler et al., 1993). Triethylamine or diisopropyl ethylamine at 0.1% (v/v) and ammonium acetate at 5 to 50 mM has been successful for this purpose. Since ammonium acetate is poorly soluble in acetonitrile, it should be dissolved in the alcoholic component of the mobile phase prior to mixing with other components. The ammonium acetate concentration in mobile phases composed primarily of acetonitrile must be mixed at lower concentration to avoid precipitation. In some cases, stainless steel frits have been reported to cause oxidative losses of carotenoids (Epler et al., 1992). When available, columns should be obtained with biocompatible frits such as titanium, Hastolloy C, or PEEK. 

A microchip-atmospheric pressure thermospray ionization technique was developed to investigate ofloxacin in the presence of other compounds (09RCM3313). Ofloxacin was detected by a voltammetric method in human urine (08ELA144). The trace of ofloxacin was detected with poly (crystal violet) film modified electrodes (07MI48). 

SCHEME 4.1 Schematics of radiolysis and reducing species. As a result of ionization of the water molecule, hydroxyl radicals and hydrated electrons are formed. The final radiolytic yield depends on the secondary reactions in spurs and on the presence of other compounds. See Refs 25,26,190, and 191 for the detailed discussion and references. Solvated electrons are mobile enough to escape spurs and to react with the heme protein complexes even at 77K. All other reactive products of radiolysis are immobilized in the solid solvent matrix, or trapped by radical quenchers. 

In this context, CH4 oxidation with hydrogen peroxide holds a special place, because in the presence of other compounds (ethylbenzene, cyclohexane, etc.) the ratio ... 

One inert marker only indicates the diffusing species in that compound layer in which it is embedded or with which it borders. If this layer grows under conditions of diffusion control, then the very presence of other compound layers provides in itself evidence that another component is diffusing across their bulks. 

DNOC enters the air, water, and soil during its manufacture and transport. It also enters the environment when formulated products are prepared and used. Very small amounts of DNOC may form in the atmosphere in the presence of other compounds. Wastes containing DNOC are produced during its manufacture and use. These DNOC-containing wastes are often disposed in... 

Tandem mass spectrometry allows more structural information to be obtained on a particular ionic species, because the used ionization method yields relatively few structurally diagnostic fragments, or because its fragmentation is obscured by the presence of other compounds in the mixture introduced in the source, or because it is obscured by other ions generated from the matrix in the course of ionization. 

Hashizume and Samuta 1999). 3-Isobutyl-2-methoxypyrazine (IBMP) is the dominant compound and is located in the grape skin, and being water soluble is rapidly extracted into the must. Although there is unproven evidence that yeast can metabolise this compound, sensory studies suggest that its aroma impact is dependent on the presence of other compounds that partially mask its aroma, such as phenyl ethanol and its ester, which are produced in higher amounts by Saccha-romyces bayanus (Treloar and Howell 2006 Eglinton and Henschke, unpublished). 

Solubility can also be enhanced by the presence of other compounds. This phenomenon is caused by one or more compounds acting as solubility enhancers for other compounds present on a surface. This phenomenon is sometimes called the local cosolvent effect. A typical method of enhancing contaminant solubility is through the addition of a small amount of secondary solvent to the SCF cleaning system. Alcohols are commonly used in this manner to increase solubilities of more polar contaminants. However, more subtle local cosolvent effects have been observed. Perhaps a classic example was first reported by Kumik and Reid. In their study, they observed that the solubilities of both naphthalene and benzoic acid in supercritical CO2 were enhanced by 107% and 280%, respectively, when both species were present. It has also been shown that there needs to be enough of a secondary component present in solution about the local contaminant environment to enhance the solubility of another compound, This example demonstrated that an excess of phenanthrene promoted the solubility of anthracene in supercritical COj, but since anthracene was only present in very small quantities, it did not help to enhance the overall solubility of phenanthrene. A... 

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