Solvent-based interferences

Materials, such as strong acids, strong bases, biocides, or soils heavily contaminated with solvents, would interfere with this technology. Tight clays have the tendency to slow down the propagation of the bacteria due to tight soil structures. With certain salts, the soil pores can be kept open to allow the bacteria access to the contaminants. All information is from the vendor and has not been independently verified. 

External mold releases, sprayed onto the mold and not added to the compound itself, can still be valuable tools. These solutions are water- or solvent-based, and when applied condense into a semi-durable, heat-resistant film on the hot mold that may allow dozens of part releases or more before having to be reapplied. However, if an external agent has to be used repeatedly during a production run, it can interfere with productivity, making a mold-rdease lubricant added to the resin itself the more cost-effective approach [11-3,11-13],... 

KED using helium as the collision gas works very well when the interfering polyatomic ion is physically larger than the analyte ion. This is exemplified in Figure 10.4, which shows helium flow optimization plots for six elements in 1 10 diluted seawater. It can be seen that the signal intensity for the analytes—Cr, V, Co, Ni, Cu, and As—are all at a maximum, whereas their respective matrix, argon, and solvent-based polyatomic interferences are all at a minimum at a similar helium flow rate of 5-6 mL/min. All the analytes show very good sensitivity because the... 

The benefit of the QCell approach is seen in Fignre 10.9, which shows a list of analytes in the far left-hand column and the suggested cut-off mass in the next column. By using the appropriate cut-off mass, the potential polyatomic interferents in the third column will not be created because the majority of the parent ions shown in the final coliunn will be unstable and will not be present to react and combine with the other matrix- or solvent-based ions in the ceU. The only ions present wiU be the parents ions shown in bold in the final column, which are higher than the selected... 

Because they are weak acids or bases, the iadicators may affect the pH of the sample, especially ia the case of a poorly buffered solution. Variations in the ionic strength or solvent composition, or both, also can produce large uncertainties in pH measurements, presumably caused by changes in the equihbria of the indicator species. Specific chemical reactions also may occur between solutes in the sample and the indicator species to produce appreciable pH errors. Examples of such interferences include binding of the indicator forms by proteins and colloidal substances and direct reaction with sample components, eg, oxidising agents and heavy-metal ions. 

A number of techniques have been developed for the trace analysis of siUcones in environmental samples. In these analyses, care must be taken to avoid contamination of the samples because of the ubiquitous presence of siUcones, particularly in a laboratory environment. Depending on the method of detection, interference from inorganic siUcate can also be problematic, hence nonsiUca-based vessels are often used in these deterrninations. SiUcones have been extracted from environmental samples with solvents such as hexane, diethyl ether, methyl isobutylketone, ethyl acetate, and tetrahydrofuran (THF)... 

The mono-silylated or free acetamides, which are liberated during silylation with 22 a, can, furthermore, interfere with any subsequent reaction, e.g. with electrophiles. Thus in the one-pot/one-step silylation, Friedel-Crafts catalyzed, nucleoside synthesis starting from protected sugar derivatives and pyrimidine or purine bases, the mono- or bis-silylated amides such as 22 a can compete with less reactive silylated heterocycHc bases for the intermediate electrophilic sugar cation to form protected 1-acetylamino sugars in up to 49% yield [42, 47]. On silylation with trimethylsilylated urea 23 a the Hberated free urea is nearly insoluble in most solvents, for example CH2CI2, and thus rapidly precipitated [43]. 

Alternatively, LC is used for the separation and quantification of PAHs using both UV and fluorescence detection. The analytes are identified based on their relative retention times and UV and/or fluorescence emission spectra. For UV detection an efficient cleanup is a prerequisite since this detection method is not very selective (almost universal for PAHs), and hence it also responds to many coeluting compounds. Due to the high specificity of fluorescence detection for most PAHs, this LC detection method is less susceptible to potential interferences. As in the case of GC the apphcation of internal standard(s) is mandatory since solvents have to be evaporated during the cleanup, which may result in partial losses of some of the more volatile analytes. 

Beasley et al. developed a panel of immunoassays to monitor DDT, its metabolites, and structurally related compounds, but they found that milk has a severe effect on the assay performance. They found that when directly utilizing whole milk, color development was completely inhibited. Even when using 1 100 dilutions of whole milk, the assay sensitivity was reduced by 90% (based on the IC50 shift, not simply the dilution factor). A number of procedures were evaluated to eliminate the interferences from the fat-soluble analytes. However, many of the procedures that removed interferences also removed the analytes. Extraction with a mixture of solvents and the use of similarly processed blank milk to prepare the standards ultimately yielded more accurate results. This article demonstrates the difficulties encountered in analyzing lipid-soluble analytes. 

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