Analytical performance quantification range

Bings77 quantified 11 trace metals in lubricating oil with the aid of solution based calibration in LA-ICP-MS using a ToF mass spectrometer. It has been shown that good analytical performance in terms of precision (6 % on average) and low detection limits in the ng g-1 range can be obtained with this easy and fast quantification procedure in LA-ICP-MS.77... 

With certain toxicokinetic studies or therapeutic drugs dosed in high concentrations, the expected concentration in the sample may be well outside the quantification range as defined by the ULOQ. These samples must be diluted into the accepted range of the standard curve to determine an initial concentration and then multiplied by the dilution factor to determine the final concentration of the analyte in the sample. Although it is preferable to dilute the sample in matrix, in many cases, the process is performed in a buffer diluent. 

To reduce the possibility of false positives, the intensities of one to three selected ions are compared to the intensity of a unique target ion of the same spectrum. The sample ratios are compared to the ratios of a standard. If the sample ratios fall within a certain range of the standard, and the retention time matches the standard within specifications, the analyte is considered present. Quantification is performed by integrating the response of the target ion only. 

It is therefore essential that the variability of an assay be known precisely (Ezan and Grassi, 2000). The performance of an assay in terms of accuracy, reproducibility (CV, interassay variation), and repeatability (CV, intraassay variation) should be determined. For an ELISA, accuracy in the range of 85 to 115% of the standard value and CVs in the range of 15 to 20% are common. The assay limit of quantification is then taken as the lowest concentration of analyte that provides CVs under, e.g., <10% and accuracy within, e.g., 15% of the standard value. A discussion of factors leading to imprecision of microarrays will be addressed later. 

The authors determined specificity using the known hydrolytic degradation products. The precision of spiked samples of these degradation products were determined and found to be acceptable (99.9 0.4%). Accuracy of the method was determined using spiked recoveries of piroxicam benzoate, and the recoveries were acceptable (99.1-100.5%). Assay precision n = 6, RSD = 0.4%) was in accord with recommended criteria [7]. Within-day precision was performed on two instruments on two separate days, and the overall intermediate precision was 1.0%. The method was linear over the expected analyte concentration range giving a regression line of 1 = 0.999. The detection (DL) and quantification levels (QL) were assessed, and the latter was determined as 0.185 pg/ml (ca. 0.04%). 

Determination of water solubility of ionic liquids Quanfitative ESI MS has been applied fo determine water solubility of several ILs [18]. The ion currenf (infensify) of the analyte signals was found to depend on the analyte concentration over a restricted range of concenfra-tions. Nevertheless, relative quantifications performed by the use of infernal standards deliver more reliable results. Isotopically labeled analogs of fhe... 

The purpose of an analytical method is the deliverance of a qualitative and/or quantitative result with an acceptable uncertainty level. Therefore, theoretically, validation boils down to measuring uncertainty . In practice, method validation is done by evaluating a series of method performance characteristics, such as precision, trueness, selectivity/specificity, linearity, operating range, recovery, LOD, limit of quantification (LOQ), sensitivity, ruggedness/robustness, and applicability. Calibration and traceability have been mentioned also as performance characteristics of a method [2, 4]. To these performance parameters, MU can be added, although MU is a key indicator for both fitness for purpose of a method and constant reliability of analytical results achieved in a laboratory (IQC). MU is a comprehensive parameter covering all sources of error and thus more than method validation alone. 

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%. 

At about the same time, our laboratory has reported the development and validation of an LC tandem MS assay for as much as six TKIs simultaneously. The proposed LC-MS/MS method allows the simultaneous determination of clinically relevant ranges of concentrations for the six major TKIs currently in use imatinib, dasatinib, nilotinib, sunitinib, sorafenib, and lapatinib [122], Plasma is purified by acetonitrile protein precipitation followed by reversed-phase chromatographic separation. Analyte quantification is performed by electrospray ionization-triple quadrupole mass spectrometry by selected reaction monitoring (SRM) detection using the positive mode. This was the first broad-range LC-MS/MS assay covering the major currently in-use TKIs. 

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