Method performance terms analytical range

PLC is used for separations of 2 to 5 mg of sample on thin-layer chromatography (TLC) plates (0.25-nun layer thickness) or high-performance TLC (HPTLC) plates (0.1-mm thickness). In these instances, the method is termed micropreparative TLC. The isolation of one to five compounds in amounts ranging from 5 to 1000 mg is carried out on thicker layers. PLC is performed for isolation of compounds to be used in other tasks, i.e., further identification by various analytical methods, such as ultraviolet (UV) solution spectrometry [1] or gas chromatography/mass spectrometry (GC/MS) [2], obtaining analytical standards, or investigations of chemical or biological properties [3]. 

The term detection capability (detection power) represents a generic term of the performance of analytical methods at the lower limit of applicability. Mostly it is used descriptively (detection capability of a method is high , good or sufficient ) or for giving order of magnitudes (detection capability is in the ppm-range or ppb-range ). 

During crop gathering, some parts of Solanaceae plants may be occasionally included. A method for the simultaneous determination of tropine, atropine, scopolamine, homatropine, anisodamine, a-solanine, and a-chaconine in grains and seeds (wheat, rye, maize, soybean, linseed) has been reported by Jandric et al. [84]. The analytes were separated by isocratic HPLC on a Chirobiotic V column and detected by ESl-MS/MS detector operating in the MRM mode. The method performances were presented in terms of linearity in the range 5-80 ng g, specificity, selectivity, accuracy (recoveries from 61 % to 111 %), precision (CV <5 %), and ruggedness. The limits of quantitation (LOQ) were in the range 2.2-4.9 ng g . ... 

If analytical methods are validated in inter-laboratory validation studies, documentation should follow the requirements of the harmonized protocol of lUPAC. " However, multi-matrix/multi-residue methods are applicable to hundreds of pesticides in dozens of commodities and have to be validated at several concentration levels. Any complete documentation of validation results is impossible in that case. Some performance characteristics, e.g., the specificity of analyte detection, an appropriate calibration range and sufficient detection sensitivity, are prerequisites for the determination of acceptable trueness and precision and their publication is less important. The LOD and LOQ depend on special instmmentation, analysts involved, time, batches of chemicals, etc., and cannot easily be reproduced. Therefore, these characteristics are less important. A practical, frequently applied alternative is the publication only of trueness (most often in terms of recovery) and precision for each analyte at each level. No consensus seems to exist as to whether these analyte-parameter sets should be documented, e.g., separately for each commodity or accumulated for all experiments done with the same analyte. In the latter case, the applicability of methods with regard to commodities can be documented in separate tables without performance characteristics. 

There is some help in terms of setting some of the performance characteristics. The European Community implementing Council Directive 96/23/EC has considered the level of bias (trueness) and precision appropriate for analytical methods used to monitor the concentrations of certain substances and residues of the substances in animal products for concentrations ranging from 1 ig kg-1 to 1 mg kg l. Their recommendations for the trueness and precision of analytical methods are shown in Tables 4.2 and 4.3, respectively. However,... 

Most manufacturers provide some indication of the performance of their analyzers with preferred reagents in terms of imprecision, linearity, and reportable ranges. All analytical methods should be assessed by the user for imprecision, accuracy, linearity, limits of detection, and carryover between samples. 

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