The azo coupling between 1-naphthol and the DS, formed by diazotation of immobilized m-APAA, ensures high efficiency of the pollutant pre-concentration and selectivity of SPE; intense color of azo product means low detection limit.
This means that detection limits of such devices are two to three orders of magnitude better than that of conventional macroelectrodes [22].
Arsenic concentrations in all soil and biological samples were determined by Instrumental Neutron Activation Analysis (INAA) at the Department of Nuclear Engineering, North Carolina State University (Raleigh, NC; mean As mass detection limit, 0.035 μg).
The detection limit and mean recovery of ACV was 1.8 ng/mL−1 and 95.6%, respectively, for molecularly imprinted solid phase extraction coupled with HPLC.
Nondetectable levels of OCCs were estimated as the mean between 0 and the detection limit.
For genes, where at least one sample in one of the conditions (MDCK or MDCK-Ras) was below the detection limit, the mean and its 95%% confidence interval in the condition with complete data were calculated.
To find these "potent responders," tests for mean response greater than the detection limit of the assay are performed using weighted t-tests with the same weighting scheme used for WNLS [see Supplemental Material, p. 4 (http://dx.doi.org/10.1289/ehp.1104688)].
Small samples from biased locations and test detection limits mean that errors may exist in the absolute prevalence estimates, but with standard methods and centralized personnel, trends and relative regional prevalence can be determined.
Neither was oxygen detectable by means of an O2-microelectrode (lower detection limit, 1 µM; Revsbech, 1989) in cultures supplied with NO2− or NO.
The assay precision is stated to be less than 8%, the mean recovery 99.9% and the detection limit better than 0.5 ng/ml (ARCHITEC T® CEAassay datasheet).
