Quantification limits assays

CV) ranged from 17 to 39%. The %CV was highest near the quantification limit of the assay. The results from the first- and second-generation assays were highly correlated (r = 0.96), allowing meaningful comparisons of virus concentrations in specimens tested with either assay. 

Quantitation limit is the lowest amount of analyte in a sample which can be quantitatively determined with suitable precision and accuracy. The quantification limit is a parameter of quantitative assays for low levels of compounds in sample matrices and is used particularly for the determination of impurities and/or degradation products. 

Orlando and Bonato [73] presented a practical and selective HPLC method for the separation and quantification of omeprazole enantiomers in human plasma. Ci8 solid-phase extraction cartridges were used to extract the enantiomers from plasma samples and the chiral separation was carried out on a Chiralpak AD column protected with a CN guard column, using ethanol-hexane (70 30) as the mobile phase, at a flow-rate of 0.5 ml/min. The detection was carried out at 302 nm. The method is linear in the range of 10-1000 ng/ml for each enantiomer, with a quantification limit of 5 ng/ml. Precision and accuracy, demonstrated by within-day and between-day assays, were lower than 10%. 

Zarghi et al. [76] developed an HPLC method, using a monolithic column, for quantification of omeprazole in plasma. The method is specific and sensitive with a quantification limit of 10 ng/ml. Sample preparation involves simple, one-step extraction procedure, and analytical recovery was complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100 x 4.6 mm) column with an isocratic mobile phase consisting of 0.01 mol/1 disodium hydrogen phosphate buffer-acetonitrile (73 27) adjusted to pH 7.1. The wavelength was set at 302 nm. The calibration curve was linear over the concentration range 20-1500 ng/ml. The coefficients of variation for intra- and interday assay were found to be less than 7%. 

Pharmacokinetic-pharmacodynamic models are becoming increasingly complex through the incorporation of covariate information, effect mechanisms, and lower quantification limits of assays which reveal compartments not previously known to exist. With sparse data collected during Phase 3 trials it may not be possible to develop and support such complex models because of... 

The quantification of ochratoxin A, at levels within the range 0.25-10 ng/ml from wine by HPLC-fluorescence detection, was described [193]. RP-HPLC - fluorescence method for the detection of ochratoxin A in wine with a detection limit of 0.05 ng/ml was also published [194]. A stable isotope dilution assay by LC-MS/MS was developed for quantification of the ochratoxin A by using [D5]-ochratoxin A as internal standard with a low detection and quantification limits of 0.5 and 1.4 pg/kg, respectively [195]. The LC-MS/MS method (ESI and APCI) was also applied to the analysis of contaminated coffee samples by ochratoxins A and B with absolute minimum detection limit around 10-20 pg per injection. Fragment ions from the [M+H]+ and [M+Na]+ ions of... 

The BIOKITS Soya Protein Assay (Tepnel) is intended to be used for the quantitation of soy protein, used as an additive, in raw or processed mixed meat products. The declared quantification limit is actually 0.5% (5000mg/kg). 

The HCP antiserum was also used to quantify HCP by ILA assay throughout the process of purification of P40. The reaction steps were the same as those described above for BBG2Na impurities (Fig. 6). The sensitivity range of the P40 HCP-ILA assay was comprised between 5 and 100 ng/ml (Fig. 15), and detection and quantification limits were 5 and 10 ng/ml respectively. 

Delete all but the first BQL observation in a continuous series of BQLs Assign the first BQL to 50% of the assay quantification limit (i.e., in NONMEM, DV = QL/2)... 

Use an additive plus proportional error model with the standard deviation of the additive component greater than or equal to 50% of the assay quantification limit... 

DL, detection limit QL, quantification limit Rec, recovery RSD, relative standard deviation Range, linear range Iso, analyte concentration that reduces the assay signal to 50%... 

The use of HPLC for quantification of phenols is often limited to a single class of phenolics and then often only to low-molecular weight compounds that are available as standards. It is, therefore, often necessary to use colorimetric assays such as the Folin-Ciocalteau assay which rely on the reducing ability of phenols to quantify the amount of total phenolics in a sample (Waterman and Mole, 1994 Singleton et al, 1999 Schofield et al, 2001). The degree of condensation of polyphenols can be quantified by colorimetric assays such as the acid-butanol assay and the vanillin assay (Waterman and Mole, 1994 Schofield et al, 2001). 

A prototype bDNA assay was developed for quantification of HGV/GBV-C RNA in serum (Pessoa et al, 1997). The assay employed target probes based on the relatively conserved sequence in the 5 untranslated region of the HGV/GB V-C genome. Preamplifier molecules and incorporation of isoC and isoG into the sequences common to bDNA assays were used to enhance the analytical sensitivity. The provisional limit of detection was 32,500 genome equivalents/ml based on dilutions of a 700-nucleotide synthetic HGV/GBV-C RNA transcript. The run-to-run variance of the assay was <15%. 

Standards, controls, and samples (250 fiL each) were treated with 500 fiL acetonitrile-acetic acid (99 1 v/v) containing IS (2.50 jUg/mL), vortexed for 10 sec, incubated for 5 min, and centrifuged at 15,000 g for 5 min. The supernatants (1650 //L) were loaded onto a polypropylene 96-well plate containing 900 fxL HPLC water under low vacuum. The SPE plates were conditioned with 500 fxL methanol followed by 300 jx. acetonitrile-water-acetic acid (30 69.5 0.5 v/v/v) (solvent A), washed with 1000 /xL solvent A, dried under full vacuum for 10 min, wiped dry with paper, eluted with 500 jxL methanol-trifluoroacetic acid (99.9 0.1 v/v) (solvent B) and then with 400 //L solvent B for 2 min, evaporated to dryness at 65°C under a gentle air stream, reconstituted with 200 /xL methanol-hydrochloric acid (0.1 M) (70 30 v/v) and assayed. The injection volume was 50 i L. Figure 11.3 shows chromatograms of blank plasma and spiked plasma with lumefantrine. A calibration curve was constructed in a concentration range of 25 to 20,000 ng/mL. Intra-assay and interassay coefficients of variation were below 5.2 and 4.0%, respectively. The limit of detection was 10 ng/mL. The limit of quantification was 25 ng/mL. 

A calibration curve was constructed over a concentration range of 1 to 50 fig/mL with a correlation coefficient of 0.998. Intra-assay and inter-assay coefficients of variation were less than 7.9 and 9.5%, respectively. Mean absolute recoveries at 10 and 20 fig/mL were 72 and 76%, respectively. Limit of detection was 0.3 fig/mL. Limit of quantification was 1.0 fig/mL. 

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