External calibrator

The necessary material to perform annual verification of flaw detector is mainly composed of an electronic function generator, an external calibrated attenuator and an oscilloscope. 

In addition to fulfilling the in-house requirements for quality control, state and local air monitoring networks which are collecting data for compliance purposes are required to have an external performance audit on an annual basis. Under this program, an independent organization supplies externally calibrated sources of air pollutant gases to be measured by the instrumentation undergoing audit. An audit report summarizes the performance of the instruments. If necessary, further action must be taken to eliminate any major discrepancies between the internal and external calibration results. 

Do require external calibration laboratories to provide calibration certificates and results. 

A matrix extract was prepared from poison-free scallop and spiked at the level of 200 ngg of scallop hepatopancreas. The toxins were determined by using LC-MS with calibration employing external standards prepared in methanol. The matrix extract was then spiked further with 300 ngg of each of the toxins and redetermined. The results obtained for each analyte are summarized in Table 5.17 and show that, when using the external calibration method, the values obtained range from 138 to 170 ngg a reduction in accuracy of between 15... 

Quantitation was performed in all cases using the external calibration method. A series of standards were injected and the responses plotted against their known concentrations. Peak responses in samples were compared with the calibration plots to obtain the amount found (nanograms). A fresh calibration plot was generated with each analytical set of samples. 

Combine a 0.5-mL aliquot of the final sample exfract or a 0.5-mL aliquot of the tebu-conazole portion [0.004 mgL in acetone-water (3 1, v/v)] of an external calibration standard, with a 0.5-mL aliquot of the [ NsJtebuconazole internal standard (IS) portion [0.004 mg L in acetonitrile-water (1 4, v/v)] of the external calibration standard. Combination may be made using other volumes as long as the solutions are... 

Since the internal standard (IS) solution is added to the sample at a point just after extraction, no addition of IS to the final sample extract is required. An external calibration standard solution with a 0.05 mg concentration of both native and... 

With the FT-ICR mass spectrometer it is possible to obtain high mass accuracy (about 1-5 ppm calibrated externally, 0.5-1-0 ppm if calibrated internally here an external calibration has been carried out using a tune mix containing compounds with m/z from... 

The 2 pi of the concentrated peptide solution was mixed with 4 pi of 2,5-dihydroxybenzoic acid [ 7 mg in 500 pi of the mixture of acetonitrile/0.1% trifluoroacetic acid, 1/2 (v/v)]. The resulting mixture was applied to the MALDI steel plate and left to crystallise. Afterwards, the MALDI-TOF mass spectra were measured by a BIFLEX IV instrument (Bruker, Germany) under appropriate conditions (potential 19 kV on the plate and 15.05 kV on the deflector, positive reflector mode potential 20 kV, laser intensity 50 or 60%). The range of detected masses was from 600 to 3000 Da. For the external calibration the standard mixture of peptides M-Pep was used. 

A combination of FIA with ICP-MS was applied for direct determination of lead in aqueous samples. Calibration of the 208Pb signal by addition of standard was found to be better than external calibration and isotope dilution. In the 50 pg Pb/L range RSD was 1% for wine and 3.5% for urine62. 

Pfaffl MW, Hageleit M (2001) Validities of mRNA quantification using recombinant RNA and recombinant DNA external calibration curves in real-time RT-PCR. Biotech Lett 23 275-282... 

Quantification is usually achieved by a standard addition method, use of labeled internal standards, and/or external calibration curves. In order to allow for matrix interferences the most reliable method for a correct quantitation of the analytes is the isotope dilution method, which takes into account intrinsic matrix responses, using a deuterated internal standard or carbon-13-labeled internal standard with the same chemistry as the pesticide being analyzed (i.e., d-5 atrazine for atrazine analysis). Quality analytical parameters are usually achieved by participation in interlaboratory exercises and/or the analysis of certified reference materials [21]. 

Cousin, H. and Magyar, B. (1994). Precision and accuracy of laser ablation-ICP-MS analysis of rare earth elements with external calibration. Mikrochimica Acta 113 313-323. 

Note The numerous ionization methods and mass analyzers in use have created a demand for a large number of calibration compounds to suit their specific needs. Therefore, mass calibration compounds will occasionally be addressed later in the chapters on ionization methods. It is also not possible to specify a general level of mass accuracy with external calibration. Depending on the type of mass analyzer and on the frequency of recalibration, mass accuracy can be as high as 1 mmu or as low as 0.5 u. 

Note Besides from elongated deteetion intervals, mass aeeuraey of FT-ICR-MS also benefits by a faetor of 3-10 from internal mass ealibration compared to external calibration (Chap. 3.3.5). External calibration works the better, the closer the cyclotron radius and the number of calibrant ions fit the conditions of the intended analytical measurements. [200]... 

Chiral or achiral assay and purity determinations are done according to an external calibration calculation procedure, either with or without internal standardization. The calibration is performed against a 10% w/w (compared to the nominal concentration of the sample solution at 100% w/w) reference standard solution. The sample solution for the purity determination remains at the 100% w/w level, while that of the assay determination is diluted 10 times. The reason for the difference in concentration levels is similar to the purity method. A suggested sample injection sequence can be... 

To obtain absolute concentrations of metabolites, calibration techniques are necessary. For this purpose an external calibration compound of known concentration can be measured to which the metabolite signals are referenced. Another possibility is the use of spectral signals from a tissue compound with known concentration serving as internal reference. 

There are different concepts for the calibration. External calibration uses the measurement of separate samples containing known amounts of analyte and we compare the signal from both, the calibration sample and our unknown sample. This method requires that the differences in the matrix of sample and calibration sample does not significantly influence the response. The use of an internal... 

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