Below detection, limit characterization

Notes Tr, below limit of detection C, characterized but not quantified N, known to be present see Appendix 2 for references included in database. ... 

Water samples (drinking water, rain, sea, river or waste water and others) have been characterized by ICP-MS with multi-element capability in respect to metal impurities (such as Ag, Al, As, Ba, Be, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Na, Sb, Se, Mg, Mn, Mo, Ni, Pb, Tl, Th, U, V and Zn) in many laboratories in routine mode with detection limits at the low ng I 1 range using ICP-QMS, and below by means of ICP-SFMS. Drinking water samples are controlled in respect of the European legislation (Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption). For quality control of analytical data, certified standard reference materials e.g. drinking water standard (40CFR 141.51), river water reference material SLRS-4 or CASS-2 certified reference sea-water material and others are employed. 

Equilibrium FCC from a refinery contains these metals at levels that are usually below the limit of detection of most spectroscopic techniques of catalyst characterization. Furthermore, the simultaneous presence of several elements and coke further complicate the study of the effects that individual metals may have on catalyst performance. 

Kidney slices have been widely used to characterize renal uptake. The extracellular marker compounds, such as methoxyinulin and sucrose, were below the limit of detection in the luminal space of the proximal tubules, while they could... 

Continuous air monitoring for trace contaminants in ambient air has developed extensively since the mid-1960s as a result of stimulation from new air pollution measurement requirements. Workers expect that similar needs will develop as certain chemical constituents of particulate material are identified as factors in human health effects. Techniques for the continuous chemical characterization of particulate matter are slow in coming because the amounts of material sampled are small, often below the detection limits of instrumentation. In all cases so far, either a precollection method like filtration or a special detector of high sensitivity has been required. 

Therefore, none of the likely intermediates of the methanol oxidation reaction, such as methoxy (BE 285.2 eV) or formate (BE 287.7 eV), were observed under reaction conditions (Carley et al., 1996). All features in Cls spectra characterized by values of BE higher than 288 eV are assigned to gas-phase contributions of educts and products of the reaction. The corresponding Ols features at BE values greater than 533 eV are shown in Figure 22A. Because the elemental detection limit in XPS is of the order of 2% (McIntyre and Chan, 1990), we conclude that, if intermediates were present at the surface, their concentrations must have been below that value. 

Interpretation of Residues Present Below the Limit of Detection Corrections for Incomplete Field Recovery 363 Characterization of Dissipation Kinetics 363 Outliers and Atypical Observations 364... 

Figure 7.20 illustrates a west-east concentration profile (from left to right of the plot) at a latitude of about 68° S (west of the Antarctic Peninsula) of methylated Cd, Pb and Hg in surface sea water samples (7, 24) analyzed during April 1995. Chlorophyll-fl was determined by Templin and Bathmann (59). This profile is divided into two different areas, one characterized by pack-ice from 98° W to 84° W, the other one by a totally closed ice sheet from 84° W to 68° W. In the pack-ice section, the methylated heavy metal compounds could normally be determined with concentrations distinctly above the detection limit, whereas in the polar ocean under the closed ice sheet methylated heavy metals were mostly below or at the detection limit, except small concentrations near the shore of the Antarctic Peninsula (right side of Figure 7.20). 

Following a single intragluteal intramuscular injection of microencapsulated octreotide acetate in healthy cholecystectomized subjects, the pharmacokinetic profile of octreotide was characterized by an initial peak of octreotide followed by a sustained release of drug. Plateau concentration was sustained up to day 70, and gradually declined to below the detection limit by day 112. A population covariate pharmacokinetic model was constructed that consisted of two absorption processes, one for immediate-release portion from the surface, unencapsulated drug and another for sustained-release portion from the microencapsulated drug. ... 

Chemical data resulting from trace and ultratraee analysis are usually characterized by a certain percentage of observations that are below LOD. These data are generally reported as less than the detection limit and data sets with less-than observations are termed censored data in statistieal terminology. Censored data may not present a problem in monitoring studies when most of the concentrations of analytes of interest are well above detection limits. However, for most of environmental studies this is not the case. Analyses of trace metals in PM are one example of data sets with a considerable amount of observations being below the respective LOD. 

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