Sample preparation quality control

The quantification of drugs and metabolites in biological samples is performed by comparing peak areas or, less frequently, peak height of the analytes in the unknown sample with those obtained in quality control samples prepared by spiking the same matrix with known amounts of the analytes. The reproducibility of areas is mainly dependent on the volume of sample injected, which can... 

Table 9.7 An example of a Quality Control sample spiking scheme for the preparation of hquid quality control samples prepared in bulk at three concentrations (low, mid, high)...

Fresh oxamyl standards were prepared for each fortification event. Concentrations of 50 and 400 qg mL analytical-grade oxamyl were prepared in a 20% acetonitrile-80% FIPLC-grade water solution. The solutions were tranferred in 1-mL aliquots into uniquely identified vials so that each vial contained the correct volume of oxamyl standard to fortify one quality control sample. The vials were shipped as needed during the course of the study to each field site. 

Encouraged by this spectral reproducibility, we focused our efforts on the particularly challenging problem of distinguishing bacterial strains by MALDI MS. We developed a modified correlation approach22 that relies on two fundamental qualities of bacterial mass spectra. First, because different bacterial strains of the same species have substantial, if not complete, genetic overlap, most of the protein masses observed with two different strains will be identical. This feature limits the value of the biomarker approach that is commonly used to differentiate bacteria species. Second, as just noted, closely controlled sample preparation and mass analysis procedures can result in highly reproducible results.22 The modified correlation approach takes advantage of subtle, yet reproducible, differences in mass spectra obtained from dif-... 

Check reagents, standards and reference materials to ensure that adequate stocks of the correct grades are available. Where reagents and quality control samples require preparation, this may need to be done in advance. If stocks of prepared reagents already exist, these must be checked to ensure that they are still usable. All reagents should be well-labelled. 

The use of standard solutions, reference standards, and quality control samples, whether prepared by the laboratory or purchased commercially, is essential to valid analyses of test and control article/carrier mixtures and biological fluids (blood, serum, plasma, etc). 

As far as the preparation of the stock solutions for calibration standards and quality control samples is concerned, different labs use different approaches. In general, the calibrators used for the validation should be prepared from... 

The quality control samples are prepared as described in Table 1.4.3. Target values are calculated according to the amount of weighed product, and values obtained must be within 15% of the target value. 

Fill the autosampler with corresponding standard mixtures, quality control samples, and analytical samples. Prepare a working list using the ChromStar software and start the program by running the autosampler (autosampler starts ChromStar). Dilute oxidized urine 1 5 with water. All other samples are analyzed undiluted. Inject 10-20 p.1 of the sample. 

Chemical analyses by INAA were conducted at the Archaeometry Laboratory at the Missouri University Research Reactor Center (MURR). Aliquots of sample were oven-dried at 100 °C for 24 h. Amounts of approximately 150 mg were weighed into small polyvials used for short irradiations. At the same time, 200 mg of each sample was weighed into high-purity quartz vials used for long irradiations. Along with the majolica samples, reference standards of SRM-I633a (coal fly ash) and SRM-688 (basalt rock) were similarly prepared, as well as quality control samples of SRM-278 (obsidian rock) and Ohio Red Clay (standards treated as unknowns). 

All chemicals, reagents, mobile phases, reference standards, quality control samples with purity, grade, their source, or detailed instructions on their preparation. 

Quality control sample, often chosen randomly, from a batch of samples and undergoing separate, but identical sample preparation and analysis whose purpose is to monitor method precision and sample homogeneity. Duplicate testing also aids in the evaluation of analyst proficiency. Volume 1(10). 

Analytical measurements should be made with properly tested and documented procedures. These procedures should utilise controls and calibration steps to minimise random and systematic errors. There are basically two types of controls (a) those used to determine whether or not an analytical procedure is in statistical control, and (b) those used to determine whether or not an analyte of interest is present in a studied population but not in a similar control population. The purpose of calibration is to minimise bias in the measurement process. Calibration or standardisation critically depends upon the quality of the chemicals in the standard solutions and the care exercised in their preparation. Another important factor is the stability of these standards once they are prepared. Calibration check standards should be freshly prepared frequently, depending on their stability (Keith, 1991). No data should be reported beyond the range of calibration of the methodology. Appropriate quality control samples and experiments must be included to verify that interferences are not present with the analytes of interest, or, if they are, that they be removed or accommodated. 

Parallel to the preparation of proficiency test samples, some laboratories do prepare quality control samples by the same methods, to check... 

Ensuring quality during sample preparation requires that the samples do not come in contact with one another, nor should they be contaminated by chemicals from the laboratory or other samples, and the procedures are shown to be controlled. 

The calibration standards representing LLOQ, ULOQ, and a midpoint serve as quality control samples. These standards are freshly prepared in control plasma, extracted, and run in parallel to the all gels. 

Two independent solutions of the test subject were prepared in DMSO (1 mg/mL). One of these solutions was used for the preparation of the Calibration standard samples. The other one was used for making up the quality control samples. 

Stock solutions of the drug and the internal standard were prepared in methanol in a concentration of 2 mM (docetaxel) and 1 mM in case of the internal standard, paclitaxel. A separate stock solution was made up for the preparation of the calibration standards and quality control samples in order to uncover possible errors during the preparation of stock solutions. 

Standard and Quality Control Samples Standard and quality control samples have been prepared in mouse plasma (anticoagulant heparin) obtained from Biomeda, Foster City, USA. 

Two separate stock solutions were made up for the preparation of the calibration standards and quality control samples, in order to uncover possible errors during the preparation of stock solutions. 

Sample preparation for calibration standards, quality control samples and unknown urine samples ... 

The recovery has been assessed for this assay as well. Samples were prepared in 0.1 % formic acid in the same concentration as in the urine quality control samples. Very good recovery values in the range of 92.0 to... 

The stock solutions of the internal standards lovastatin and lovastatin acid were prepared in the same way (0.3 mg/mL). Combined working solutions of the analytes (5.0 [xg/mL) were prepared by dilution with acetonitrile. Two completely separate sets of stock solutions and dilutions were made up for the preparation of working solutions for calibration standards and quality control samples. 

A quality control sample, often known as a QC sample or check sample may be an in-house material prepared for this purpose or it may be from a previously analysed batch of samples. 

Control samples should have a high degree of similarity to the actual samples analyzed otherwise, one cannot draw reliable conclusions on the measurement system s performance. Control samples must be so homogeneous and stable that individual increments measured at various times will have less variability than the measurement process itself. Quality Control samples are prepared by adding known amounts of analytes to blank specimens. They can be purchased as certified reference material (CRM) or may be prepared in-house. In the latter case, sufficient quantities should be prepared to allow the same samples to be used over a longer period of time. Their stability over time should be proven and their accuracy verified, preferably through interlaboratory tests or by other analysis methods. 

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