INDEX ubiquitousness

A more difficult criterion to meet with flow markers is that the polymer samples not contain interferents that coelute with or very near the flow marker and either affect its retention time or the ability of the analyst to reproducibly identify the retention time of the peak. Water is a ubiquitous problem in nonaqueous GPC and, when using a refractive index detector, it can cause a variable magnitude, negative area peak that may coelute with certain choices of totally permeated flow markers. This variable area negative peak may alter the apparent position of the flow marker when the flow rate has actually been invariant, thereby causing the user to falsely adjust data to compensate for the flow error. Similar problems can occur with the elution of positive peaks that are not exactly identical in elution to the totally permeated flow marker. Species that often contribute to these problems are residual monomer, reactants, surfactants, by-products, or buffers from the synthesis of the polymer. 

The most ubiquitous pesticide was simazine, present in 80% of the samples, followed by atrazine, diuron, DEA and diazinon, present in more than 50% of the samples (64%, 56%, 56% and 50%, respectively). Cyanazine, molinate, fenitro-thion and mecoprop were detected in less than 5% of the samples. The maximum individual concentrations were observed for alachlor (9,950 ng/L in M33, 2008), dimethoate (2,277 ng/L in M35, 2010), DEA (1,370 ng/L in M48, 2007) and linuron (1,010 ng/L in M33, 2008), while many others, such as terbuthylazine, DIA, atrazine and metolachlor, presented levels also higher than 500 ng/L. Results are consistent when evaluated with the GUS index (see Table 2). Mots triazines and metolachlor, i.e., the compounds with GUS index > 3 and therefore with higher leaching potential, were among the most ubiquitous an abundant compounds. In contrast, fenitrothion, which according to its GUS index (0.64) is a nonlixiviable pesticide, was detected at low levels in less than 5% of the samples. 

Chemical compounds are ubiquitous in the environment. Some are dispersed on purpose and some are released accidentally. Some have local effects while others have a global impact. This impact has been variously quantified (see Helm 2003 and chapter by Helm, p. 285 Bruggemann and Drescher-Kaden 2003 Halfon and Bruggemann 1989 Bruggemann and Munzer 1993). For example physico-chemical properties and environmental persistence, i.e. criteria, have been combined in an index function... 

Water does not ignite, does not burn, is odorless and colorless, and is ubiquitous important prerequisites for the solvent of choice in catalytic processes. The dielectric constant or the refractive index can be important in specific reactions and their analytical monitoring. The favorable thermal properties make water... 

Some type of melt viscosity is included in the specification for almost every polymeric or plastic product. This is because viscosity is related to the molecular weight and to the performance of a polymer. Equipment used for rheological measurements range from the simple and ubiquitous melt flow indexer to the precise and quantitative capillary and cone-and-plate rheometers. 

Crystalline silica is the most ubiquitous mineral on earth, being found as a component in almost all other mineral deposits. There are over 20 crystalline phases of silica, differing only slightly in physical properties. Most of these occur naturally, but only a few find any significant use in polymers, notably quartz, novacite and crystobalite. Quartz is the most widely used and is usually found as prismatic crystals. Mohs hardness is 7, specific gravity is 2.6 and refractive index 1.54-1.55. 

PAHs are ubiquitous and can be foimd everywhere in the environment. They occm in air, water, sediment, soil, and food samples. About 500 PAHs and their related compoimds have been detected in the air but most measurements have been made on benzo[a]p5n-ene, which is regarded as an index for the level of PAH contamination [7]. The natural backgroimd level for benzo[a]pyrene is nearly zero. Several monitoring studies indicate that there are higher concentrations of PAHs in the luban air than in the riu-al air. Atmospheric PAH concentration was approximately three to five times higher than those of the rural area, and winter concentration was approximately five to ten times higher than summer concentrations [12]. 

The compound at a retention index (RI) of 897 is tentatively identified as a methoxy-phenyl oxime and possesses a base peak at m/z 133 and a molecular ion of m/z 151. This compound is believed to originate from the glue that is used to attach the fiber to the syringe plunger. A series of compounds are observed that have a base peak of m/z 100. These compounds may be associated with the action of moisture with the Vespel ferrules. Other contaminants include the ubiquitous phthalic acid esters and antioxidants, butylated hydroxy toluene and butylated hydroxy anisole. Sources of these compounds are the packaging used for vials. 

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