Recoveries and limit of detection

The recoveries from untreated control samples fortified with orbencarb at 0.2 mg kg for crops and 0.5 mg kg for soils were 85-98 and 89-101%, respectively. The limit of detection was 0.005mgkg for crops and 0.01 mgkg for soils. The recovery of I was 92-102% from 0.2 mg kg -fortified crops and 95-98% from 0.5mgkg -fortified soils. The recovery of II was 68-79% from 0.2 mg kg -fortified crops and 73-77% from 0.5 mg kg -fortified soils. The limits of detection of I and n were the same as those of orbencarb. 

The residue R, expressed in mgkg orbencarb, I or II, is calculated from the following equation  

VEnd = terminal volume of sample solution from Section 6.2 (mL) y = portion of volume of VEnd injected into the gas chromatograph (qL) 

Wa = amount of orbencarb for y read from the calibration curve (ng) 

The partition rates of orbencarb and I in aqueous solutions (pH 2-12) into ethyl acetate-n-hexane (1 1, v/v) were as high as 87-90%, and the partition rate did not differ depending on the pH of the liquid. On the other hand, the recovery of II from aqueous solutions into ethyl acetate-n-hexane (1 1, v/v) was 85% at pH 2, 34% at 

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Recoveries, limit of quantitation, and limit of detection Calculation of residues Important points... 

In addition, each workbook contained a summary table of all results and limit of detection (LOD) determinations. The table was organized with sample identifications in the left-hand column. Eor each analyte, the analytical result and the LOD appeared in adjacent columns, and analyte recoveries appeared above the results columns. The summary table was generated automatically from the analytical results in the individual worksheets, without operator intervention or re-entry of any information. 

Fish tissue is homogenized with a Polytron apparatus using methanol as a solvent, or extracted in a ball mill with hexane. The extracts are evaporated to dryness, dissolved in ethyl acetate toluene, and cleaned up on a gel permeation column followed by an alumina column. Analysis is performed by GC/NPD (Muir et al. 1981). Recovery is acceptable (79-97%) and limit of detection is 10 ng/g (Muir et al. 1981). 

As stated above, most users of the headspace technique make no distinction between dynamic HS and PT. In one of the few publications that distinguished and compared these two HS modes, dynamic HS and PT were assessed as steps preceding high-resolution GC-electron capture detection for the determination of nitrous oxide in sea water. The process was found to exhibit a first-order kinetics in both cases and the matrix to exert a significant effect that was proportional to the nitrous oxide concentration in bidistilled water, as well as in synthetic and natural sea water. As expected, PT provided better extraction recovery, sensitivity and limits of detection — which fell in the pico-mole-per-millilitre range [46]. 

If carried out correctly, the process of validation enables performance characteristics, such as bias, recovery, precision and limit of detection, to be estimated with a high degree of confidence. Whether the performance characteristics determined are deemed acceptable, or not, is another matter but the... 

As wine is a very comphcated matrix, different approaches may be used for the trace quantification of TCA. Multiple SPME methods may be used for this purpose [66]. Tribromoanisole (TEA) or deuterated TCA ([ HsjTCA) may be used as an internal standard [63], and in the latter case, the quantification is based on the monitoring of two ions m/z 210 for TCA and m/z 215 for the deuterated analog. The wine matrix requires special care during calibration. The most important parameters that are infiuenced by the matrix include analyte recoveries, linearity, limits of detection, and quantification [67]. 

The method was validated for specificity, linearity, precision, recovery, the limit of detection, and limit of determination according to ICH guidelines. The linear... 

Analytical methods including recovery rates and limits of detection for toxicologically significant components in the following media ... 

Sample preparation and limits of detection are also important determinants of the efficiency of such methods. In particular, non-selective extraction procedures are necessary for good recovery of molecules in a wide polarity range, including highly polar drugs not amenable to GC-MS. 

An analytical method vahdation study should include demonstration of the accuracy, precision, specificity, limits of detection and quantitation, linearity, range, and interferences. Additionally, peak resolution, peak tailing, and analyte recovery are important, especially in the case of chromatographic methods (37,38). 

A multiresidue analytical method based on sohd-phase extraction enrichment combined with ce has been reported to isolate, recover, and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron, and metasulfuron) from soil samples (105). Optimi2ation for ce separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb (see Soil chemistry of pesticides). 

Under the experimental conditions used the method gave a limit of detection of 5 ng. Recoveries of W-nitrosoglyphosate from the fortified soil samples (10 g) at the 1 and 5 ppm levels were nearly quantitative (6). 

The limit of determination [or limit of quantitation (LOQ)] is defined in Directive 96/46/EC as the lowest concentration tested at which an acceptable mean recovery (normally 70-110%) and acceptable relative standard deviation (normally <20%) are obtained. The specific requirements for LOQ in crops, food, feed, soil, drinking and surface water, air, body fluids, and tissues are described in Section 4. Because the abbreviation LOD usually means limit of detection rather than limit of determination, the authors prefer not to use this abbreviation here in order to avoid confusion, and LOQ is used throughout. According to Directive 96/46/EC no data with regard to the limit of detection must be given. 

Residue study protocols typically either include quality specifications for analytical procedures or refer to a written analytical method that includes such specifications. The protocol for an LSMBS should also include analytical quality specifications, either directly or by reference to a method. Analytical specifications usually include minimum and maximum recovery of analyte from fortified control samples, minimum number of such fortifications per set of samples, minimum linearity in calibration, minimum stability of response to injection of calibration solutions, and limits of quantitation and of detection. 

The limit of detection (LOD) is an important criterion of the efficiency of an analytical method. It is characterized by the smallest value of the concentration of a compound in the analytical sample. The detectable amount of anilide compounds is in the range 0.01-0.5 ng by GC and 0.1 ng by HPLC. The limit of quantitation (LOQ) ranges from 0.005 to 0.01 mg kg for vegetables, fruits and crops. The recoveries from untreated plant matrices with fortification levels between 10 and 50 times the LOD and the LOQ are 70-120%. The relative standard deviation (RSD) at 10-50 times the level of the LOD and LOQ are <10 % and <20%, respectively. 

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