Quality control spiking

Standard and quality control samples have been prepared by spiking mouse brain homogenates with the calibration standard or quality control spike solution. 

Quality control Spiked samples, blanks, critical control points... 

An approximately 10-g water sample is acidified with 60 qL of formic acid and placed in a test-tube on the Benchmate Workstation along with up to 50 samples in total including any spiked quality control samples. 

When developing or routinely using an analytical method, quality control (QC) fortifications can be added to each sample at critical points in the procedure to ensure that sensitive steps in the method were conducted properly and to pinpoint where problems occurred if results are less than satisfactory. For example, if the QC fortification samples for detection and cleanup were to show acceptable results in a batch of samples, but the extraction QC spike gave low recovery and/or high variability, then the analyst could modify instrument conditions or altering cleanup parameters immediately. Likewise, if the QC spike added just before analysis gives poor results, then instrument maintenance could be done and the samples merely re-analyzed rather than re-extracted. 

To fortify a sample, the label from a fortification sampling vial was removed and secured to the pre-labeled sample jar. Spike vials were individually shaken before use. The cap was discarded, the contents of the vial were poured into the sample jar and then the vial was dropped into the sample. The sample jar was capped with a Tefion-lined lid, hand shaken to mix, placed in a Kapak bag and sealed. Jars were placed immediately in storage freezers. In all cases, quality control samples were transported and stored with their corresponding field plot samples throughout sample handling and shipment to the analytical facility. 

Brandt [200] has extracted tri(nonylphenyl) phosphite (TNPP) from a styrene-butadiene polymer using iso-octane. Brown [211] has reported US extraction of acrylic acid monomer from polyacrylates. Ultrasonication was also shown to be a fast and efficient extraction method for organophosphate ester flame retardants and plasticisers [212]. Greenpeace [213] has recently reported the concentration of phthalate esters in 72 toys (mostly made in China) using shaking and sonication extraction methods. Extraction and analytical procedures were carefully quality controlled. QC procedures and acceptance criteria were based on USEPA method 606 for the analysis of phthalates in water samples [214]. Extraction efficiency was tested by spiking blank matrix and by standard addition to phthalate-containing samples. For removal of fatty acids from the surface of EVA pellets a lmin ultrasonic bath treatment in isopropanol is sufficient [215]. It has been noticed that the experimental ultrasonic extraction conditions are often ill defined and do not allow independent verification. 

Aspila et al. [338] reported the results of an interlaboratory quality control study in five laboratories on the electron capture gas chromatographic determination of ten chlorinated insecticides in standards and spiked and unspiked seawater samples (lindane, heptachlor, aldrin, 5-chlordane, a-chlordane, dield-rin, endrin, p, p -DDT, methoxychlor, and mirex). The methods of analyses used by these workers were not discussed, although it is mentioned that the methods were quite similar to those described in the water quality Branch Analytical Methods Manual [339]. Both hexane and benzene were used for the initial extraction of the water samples. 

Based on the study results, decide how frequently and how rigorously the bias needs to be checked during routine use of the method (e.g. every batch using a single spike) and document it in the method as part of quality control. 

Good quality control procedures are crucial to allowing the results of this project to integrated year upon year. More than 10% of all samples analyzed are for quality control. About half of these are duplicates the others are blanks, certified or internal reference standards and spiked samples. 

The accuracy of an analysis can be determined by several procedures. One common method is to analyze a known sample, such as a standard solution or a quality control check standard solution that may be available commercially, or a laboratory-prepared standard solution made from a neat compound, and to compare the test results with the true values (values expected theoretically). Such samples must be subjected to all analytical steps, including sample extraction, digestion, or concentration, similar to regular samples. Alternatively, accuracy may be estimated from the recovery of a known standard solution spiked or added into the sample in which a known amount of the same substance that is to be tested is added to an aliquot of the sample, usually as a solution, prior to the analysis. The concentration of the analyte in the spiked solution of the sample is then measured. The percent spike recovery is then calculated. A correction for the bias in the analytical procedure can then be made, based on the percent spike recovery. However, in most routine analysis such bias correction is not required. Percent spike recovery may then be calculated as follows ... 

The laboratories have a quality manager and quality section. The quahty section prepares all of the analytical quality control (AQC) standards for the laboratories, including spiked and duplicate samples. The quality section is a separate laboratory with a separate supply of deionized water, glassware, balances and chemicals. The latter, wherever possible, are purchased from a different source to those for the analytical sections. These actions ensure a more independent approach to quality control. 

Quality Assurance/Quality Control. QA/QC measures included field blanks, solvent blanks, method blanks, matrix spikes, and surrogates. Percent recovery was determined using three surrogate compounds (nitrobenzene-d5, 2-fluorobiphenyl, d-terphenyl-diQ and matrix spikes (naphthalene, pyrene, benzo[ghi]perylene) the recoveries ranged from 80 to 102%. Separate calibration models were built for each of the 16 PAHs using internal standards (naphthalene-dg, phenanthrene-dio, perylene-di2). Validation was performed using a contaminated river sediment (SRM 1944) obtained from NIST (Gaithersburg, MD) accuracy was <20% for each of the 16 analytes. 

Quality control sample (QC) A spiked sample used to monitor the performance of a bioanalytical method and to assess the integrity and validity of the results of the unknown samples analyzed in an individual batch. 

A quality control (QC) standard mixture, a normal control and an abnormal control are run with each batch. The normal control is made by aliquoting 100-pl portions of a normal range pooled plasma into screw-cap vials. The abnormal control is made by spiking 50 ml of normal pooled plasma with defined concentrations of unlabeled acylcarnitine standards spanning the mass range covered by the analysis (see Reagents and Chemicals). The concentration for each standard should be chosen based on the upper limit of the reference range for the respective acylcarnitine species. The... 

For quality control, 100 pi pooled urine spiked with 8 pmol/1 sedoheptitol and 8 pmol/1 perseitol is included in each series. In addition, a 4 x dilution of this sample and a pooled urine spiked with 180 pmol/1 erythritol, 90 pmol/1 threitol, 218 pmol/1 arabitol, 36 pmol/1 xylitol, 18 pmol/1 ribitol, 36 pmol/1 sorbitol, 145 pmol/1 mannitol, 55 pmol/1 galactitol, 16 pmol/1 sedoheptitol and 16 pmol/1 perseitol are included in each series. These three urine samples were chosen to obtain concentrations in the low, middle and high part of the calibration curves. 

Extraction and determination of samples spiked with positive controls performed as quality control checks for each bioassay run. 

The identity of spikes and surrogates suitable for quality control checks of these determinations. 

Laboratories using these methods for regulatory purposes are required to operate a formal quality control program. The minimum requirements of the program consist of an initial demonstration of laboratory capability and an ongoing analysis of spiked samples to evaluate and document data quality. The laboratory must maintain records to document the quality of data that is generated. Ongoing data quality checks are compared with established performance criteria to determine whether or not the results of analyses meet the demonstrated performance characteristics of the method. When results of spike sample analyses indicate atypical method performance, a quality control check standard must be analyzed to confirm that the measurements were performed in an in-control mode of operation. 

If any individual P falls outside the designated range for recovery, that parameter has failed the acceptance criteria. When this situation occurs, a quality control check standard containing each parameter that failed the criteria must be analyzed independent of the matrix, that is, spiked reagent water, to demonstrate that the laboratory is operating in control. If this second test is failed, the sample results for those parameters are judged to be out of control, and the problem must be immediately identified and corrected. The analytical results for those parameters in the unspiked sample are suspect and may not be reported for regulatory purposes. 

As another phase of the ongoing quality control program, method accuracy for waste water samples must be assessed and records must be maintained. After the analysis of five spiked waste water samples as in the accuracy check just described, the average (P) and the standard deviation of the percent recovery (sp) are calculated. The accuracy is expressed as a percent interval or range from P — 2sp to P + 2sp. The... 

Together, raw data and results from calibration checks, spike recoveries, quality control samples, and blanks are used to gauge accuracy. Analytical performance on replicate samples and replicate portions of the same sample measures precision. Fortification also helps ensure that qualitative identification of analyte is correct. If you spike the unknown in Figure 0-5 with extra caffeine and the area of a chromatographic peak not thought to be caffeine increases, then you have misidentified the caffeine peak. 

E. Control chart. Volatile compounds in human blood serum were measured by purge and trap gas chromatography/mass spectrometry. For quality control, serum was periodically spiked with a constant amount of 1,2-dichlorobenzene and the concentration (ng/g = ppb) was measured. Find the mean and standard deviation for the following spike data and prepare a control chart. State whether or not the observations (Obs.) meet each of the criteria for stability of a control chart. 

For each of the three spike levels in the table below, find the precision and accuracy of the quality control samples. 

Ozone data includes measurements from 380 quality controlled Vaisala ECC-ozone soundings. Ozone profiles from soundings have been inspected visually and by comparing the profile based total column ozone to the spectrometric column ozone measured preferably by Dobson spectroradiometer in Marambio or by satellite based TOMS-instrument. No normalisation factor was used to correct the profiles dubious spikes were nevertheless corrected. Soundings were made twice a month from January until July and twice a week from August until January. Occasional interruptions of soundings have existed. 

Among the elements of quality control in mycotoxin analysis, proficiency tests, control materials (reference materials and certified reference materials), traceability in spiking, and recovery checks have been demonstrated to be particularly relevant. 

Quality Control (QC) QC samples are used to check the performance of the bioanalytical method as well as to assess the precision and accuracy of the results of postdose samples. QC samples are prepared by spiking the analyte of interest and the IS into a blank/control matrix and processing similar to the postdose samples. QC samples cover the low (3 x LLOQ LLOQ = lower limit of quantitation), medium, and high (70-85% of ULOQ ULOQ = upper limit of quantitation) concentration ranges of the standard curve and are spaced across the standard curve and the postdose sample batch. 

One of the most important trends to simplify these complications is the generation of simple, rapid, and reliable procedures for sample preparation. Method development and setup require the use of materials of known compositions, for example, certified reference materials. Therefore, spiking experiments have to be performed for method quality control. Under such experimental conditions, emphasis has to be placed on the spiking procedures as they exert an influence on the recovery values. Although present scientific knowledge is not perfect, the use of spiking experiments helps to minimize the errors. The integration and automation of all steps between sample preparation... 

An extraction recovery assessment is basically required for a good quality control. The most common procedure is to spike the sample to be analysed with known amounts of the chemical compounds of concern, and to determine the compound(s) after equilibration and extraction. It should be stressed that a good recovery of spiked compounds does not necessarily mean that a good recovery will be obtained for naturally bound compounds however, an extraction procedure which cannot quantitatively recover a spiked compound should be abandoned since it will certainly not be applicable to naturally bound compounds. 

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