Sample recovery

Sample % Recovery Sample % Recovery Sample % Recovery ... 

To illustrate the effect of radial release interactions on the structure/ property relationships in shock-loaded materials, experiments were conducted on copper shock loaded using several shock-recovery designs that yielded differences in es but all having been subjected to a 10 GPa, 1 fis pulse duration, shock process [13]. Compression specimens were sectioned from these soft recovery samples to measure the reload yield behavior, and examined in the transmission electron microscope (TEM) to study the substructure evolution. The substructure and yield strength of the bulk shock-loaded copper samples were found to depend on the amount of e, in the shock-recovered sample at a constant peak pressure and pulse duration. In Fig. 6.8 the quasi-static reload yield strength of the 10 GPa shock-loaded copper is observed to increase with increasing residual sample strain. 

Third, the bulk of the items in Table 1 address method performance. These requirements must be satisfied on a substrate-by-substrate basis to address substrate-specific interferences. As discussed above, interferences are best dealt with by application of conventional sample preparation techniques use of blank substrate to account for background interferences is not permitted. The analyst must establish a limit of detection (LOD), the lowest standard concentration that yields a signal that can be differentiated from background, and an LOQ (the reader is referred to Brady for a discussion of different techniques used to determine the LOD for immunoassays). For example, analysis of a variety of corn fractions requires the generation of LOD and LOQ data for each fraction. Procedural recoveries must accompany each analytical set and be based on fresh fortification of substrate prior to extraction. Recovery samples serve to confirm that the extraction and cleanup procedures were conducted correctly for all samples in each set of analyses. Carrying control substrate through the analytical procedure is good practice if practicable. 

Field recovery samples are an important part of the quality control in DFR studies. Field fortifications allow the experimental data to be corrected for losses at all phases of the study from collection through sample transport and storage. Fresh laboratory fortifications monitor losses due to the analytical phase. This section details how the field recovery process was handled in the oxamyl tomato DFR study. 

Once method validation has been completed, the treated samples may be analyzed. The method should be under control so that no additional changes will be necessary. Analysis of laboratory-fortified samples and control samples will be used to monitor the quality of the study. The purpose of laboratory-fortified samples is confirmation of the recovery efficiency of residues from the sample matrix. A minimum of two laboratory recovery samples need to run with each set. Recoveries should average 70-120%. 

Weigh 20 g of homogenized sample into a 300-mL tail-form beaker. Begin recovery samples at this point by fortifying the control tissue matrix samples. Add 120 mL of acetone, and homogenize the mixture for approximately 5 min followed by the addition of 60 mL of laboratory-grade water with another 2 min of homogenization. 

Weigh 5.0 g of frozen homogenized sample into a 120-mL tail-form glass bottle. Begin recovery samples at this point by fortifying the control tissue matrix samples. 

Net recoveries of cyfluthrin from matrices fortified at 0.01-5.05 mg kg ranged from 77 to 119%. The limit of detection (LOD) is defined as the lowest concentration that can be determined to be statistically different from a blank or control. Calculate the value by taking the standard deviation of the residue values from the analysis of the recovery samples at the limit of quantification (LOQ) and using the equation... 

Low levels of 3,5,6-TCP were also observed in pre-exposure urine from most of the field workers. These 3,5,6-TCP levels were subtracted from urine field recovery samples and were used to correct levels of 3,5,6-TCP found in the post-exposure urine samples from these same workers. This procedure was necessary to calculate the amount of 3,5,6-TCP in the urine that was attributable to the exposure period. 

Note For this hypothetical exercise, Samples 1-3 have a target value of 3.60% absolute whereas Samples 4-6 are Spiked Recovery Samples with target values of 3.40 (No. 4), 3.61 (No. 5), and 3.80 (No. 6). 

Table 34-4 Individual sample analysis precision for hypothetical spiked recovery samples ...

To compute the results shown in Table 34-6 for the Spiked Recovery samples, the accuracy of each set of replicates for each sample, method, and location can be individually calculated using the root mean square deviation equation as shown in equations 34-5 and 34-6 in standard symbolic and MathCad 7.0 notation, respectively. The standard deviation of each set of sample replicates yields an estimate of the accuracy for each sample, for each method, and for each location. The accuracy is calculated where each yt is an individual replicate measurement and The Spiked or true values (TV) are substituted for GM in equations 34-5 and 34-6. The accuracy is calculated for each sample, each method, and each location and N is the number of replicates for each sample, method, and location. The results found in Table 34-6 represent samples 34-4 through 34-6. Note Each sample had a True Value given by a known analyte spike into the sample. 

Table 34-8 Individual sample precision and accuracy for combined Methods A and B and Labs 1 and 2 - Spiked Recovery samples ...

ENTER TRUE VALUES FOR EACH ROW (SPIKED RECOVERY SAMPLES) ... 

Falkner and Edmond [334] determined gold at femtomolar quantities in seawater by flow injection inductively coupled plasma quadrupole mass spectrometry. The technique involves preconcentration by anion exchange of gold as a cyanide complex, [AulCNjj], using 195Au radiotracer (ti/2 = 183 days) to monitor recoveries. Samples are then introduced by flow injection into an inductively coupled plasma quadrupole mass spectrometer for analysis. The method has a detection limit of 10 fM for 4 litres of seawater preconcentrated to 1 ml, and a relative precision of 15% at the 100 fM level. 

Recovery Samples of known concentration, preparation efficiency... 

Extraction solvent(s), solid phase, internal standard, recovery, sample pre-treatment, blanks, etc... 

An important precondition for the successful determination of carbon isotope ratios is the prevention of isotopic shifts as a result of the analytical procedures applied. Therefore, five recovery experiments were performed in order to detect changes of the carbon isotope ratios during sample preparation and measurement. The compounds selected for these experiments are known riverine contaminants and comprise hexachlorobutadiene, several musk fragrances, phthalates and other plasticizers, a flame retardant and a pesticide. All recovery samples were spiked with concentrations between approx. 800 ng/L and 1500 ng/L for each compound representing a common abundance level in river systems. 

The recovery of analyte in matrix should be evaluated at a minimum of two concentrations using a sufficient number of replicates (minimum of three). In practice the extraction efficiency is often determined by comparing the mean area response from processed QC samples that are used to determine intra-assay accuracy and precision to the mean area response from recovery samples at each QC concentration. 

Recovery assessment six replicates of QC samples (30, 500, and 3760 ng/mL) are used following sample preparation in Section 7.3.5 and LC-MS/ MS analysis in Section 7.3.6. Six replicates of recovery samples are analyzed directly on LC-MS/ MS. The recovery is estimated by comparing the... 

During plant operation, the purification and aftercooling system is activated depending on the results of coolant sampling in the primary circuit. The system is deactivated after coolant quality recovery. Sampling of the primary circuit coolant is carried out quarterly. 

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