Methodological detection limits

The detection limits, accuracy, and precision of any analytical methodology, as well as the composition of the sample medium, are important parameters in determining the appropriateness of a method to quantify a specific analyte at the desired level of sensitivity within a particular matrix. The lower limit of detection (LLD) has been adopted to refer to the intrinsic detection capability of a measurement procedure (sampling... 

Table 8.80 shows the present status of speciation methodology. For trace-metal speciation, atomic absorption detectors feature a relatively high absolute detection limit (10 pg level), as compared to the 0.1 to 1 pg sensitivity level for molecular ion MS techniques as well as for MIP-AES. The detection limit of LEI-ToFMS is in the attogram range. Speciation has been reviewed [550]. Various monographs deal with speciation analysis [542,551,552]. 

Sometimes for some very potent pollutants analytical methodologies provide limits of detection (LODs) higher than the concentrations that cause effects, as derived from ecotoxicological studies. Therefore efforts in the field of analytical chemistry (see Sect. 2) are focused on making available the necessary analytical capabilities to detect pollutants at the required low levels found in the environment. This was the case of pharmaceuticals, illicit drugs, perfluorinated compounds (PFCs), sunscreens/UV filters, etc. few years ago. However, this list is likely to increase with new family candidates. 

Purification methodologies for estrogens have been carried out by SPE with C18 [53, 54], polymeric [56, 60-62], silica [56-59] and anion exchange materials [59], preparative LC [53, 62], gel permeation chromatography (GPC) [54, 59, 97], liquid-liquid extraction [56], combination of them, or simple filtration [51]. However, the latter corresponds to the method with the highest reported method detection limits (MDL) [up to 175 ng/g dry weight (dw)]. 

Using the described methodology, recoveries ranged from 53 to 84% for sediment, and between 52 and 103% for fish samples. Detection limits (LODs) were in... 

Dynamic headspace-extraction stripping and purge-and-trap methodology are used most often for determination of M-hcxanc in water and hazardous wastes. Dynamic headspace extraction techniques have been applied to water samples (Roberts and Burton 1994) and sediment (Bianchi et al. 1991). Detection limits of 0.5 g/L were reported for lake water (Roberts and Burton 1994) and 20 ng/kg (ppt) for sediment (Bianchi et al. 1991). Supercritical fluid extraction (SFE) is a relatively new technique that has been applied to -hcxane in soil (Yang et al. 1995). Membrane extraction of M-hexane from water samples has been developed to provide online, continuous monitoring (Wong et al. 1995 Xu and Mitra... 

The use of spiked batches (with levels approaching the specification limit) is recommended for the transfer of impurity or related substances methodology. In parallel, the receiving site should also assess the LOD/LOQ (Limit of Detection/Limit of Quantitation) of the method for each of the specified impurities or related substances. This can help to identify whether specificity and sensitivity are issues at the receiving laboratory. 

The Environmental Health Laboratory Sciences Division of the Center for Environmental Health and Injury Control, Centers for Disease Control, is developing methods for the analysis of bromomethane and other volatile organic compounds in blood. These methods use purge and trap methodology and magnetic mass spectrometry which gives detection limits in the low parts per trillion range. 

Detection limit/quantitation limit (LOD/LOQ) Appropriate ICH-recommended methodology... 

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