Calibration file

The acquisition sequence is as follows a first acquisition calibration enables the acquisition operator to verify the data before storage. The row data, together with calibration files are transferred to the analysis program. The program transforms the row data into calibrated data, which is then analysed. 

Up to this point, all chromatographic information is in terms of elution volume. If a calibration file is available to the program, the chromatogram may be converted to log hydrodynamic volume. The chromatogram in terms of log hydrodynamic volume may be written to a file (with extension HYD) for later use. 

Mass Calibration (time-of-flight) A means of determining m/z values from their times of detection relative to initiation of acquisition of a mass spectrum. Most commonly this is accomplished using a computer-based data system and a calibration file obtained from a mass spectrum of a compound that produces ions whose m/z values are known. 

Any mass spectrometer requires mass calibration before use. However, the procedures to perform it properly and the number of calibration points needed may largely differ between different types of mass analyzers. Typically, several peaks of well-known m/z values evenly distributed over the mass range of interest are necessary. These are supplied from a well-known mass calibration compound or mass reference compound. Calibration is then performed by recording a mass spectrum of the calibration compound and subsequent correlation of experimental m/z values to the mass reference list. Usually, this conversion of the mass reference list to a calibration is accomplished by the mass spectrometer s data system. Thereby, the mass spectrum is recalibrated by interpolation of the m/z scale between the assigned calibration peaks to obtain the best match. The mass calibration obtained may then be stored in a calibration file and used for future measurements without the presence of a calibration compound. This procedure is termed external mass calibration. 

A mass spectrum of a calibration solution is acquired (calibration file) and matched against a table of the expected masses of the peaks in the calibration solution that are stored in a reference file. 

Each peak in the reference file is matched to a corresponding peak in the calibration file. 

The corresponding matched peaks in the calibration file are the calibration points. 

Peak maximum standard deviation or maximum difference between the predicted and actual mass. During calibration the difference between the measured mass in the acquired calibration file and the true mass in the reference file is taken for each pair of matched peaks. If this value exceeds the set value, the calibration will fail. Reducing the value of the standard deviation gives a more stringent limit, while increasing the standard deviation means that the requirement is easier to meet, but this may allow incorrect peak matching. 

If the acquired spectrum looks like the reference spectrum and all of the peaks expected pass the criteria above, the calibration is acceptable. If the instrument has never been calibrated before or the previous calibration file has been misplaced, a more detailed calibration routine must be used. This calibration procedure requires the location of known peaks, starting with the lowest mass ions. When a peak has been located, a digital-to-analog conversion value is assigned to the exact mass of the ion. 

Failed calibration. There are number of reasons for a calibration to fail. If an automated calibration method is used, it is possible that the reference peaks are not recognized when the reference file and calibration file are compared. This can be due to the following reasons ... 

Both 1D H spectra of glucose are now stored as calibrated files. Use the dual display to investigate both spectra and to check the identical calibration. 

Both 1D C spectra of glucose are now stored as calibrated files. 

Attention Before using another spectrum as an integral calibration file, the integral regions for this new reference must first have been defined and stored and the integrated spectrum must have been saved ... 

Now load the first DEPT spectrum. Using the third DEPT spectrum as the calibration file perform a peak picking. In the Page Layout dialog box check the X- and y- File Compare boxes and click on the File Compare... button to select the already plotted third DEPT spectrum as the calibration file. Click on the Edit Title... button to create an appropriate title. Click on the Preview button, accept clearing the Preview window and inspect the layout, which should now be the same as for the third DEPT spectrum. Plot the spectrum. 

When sample quantity is absolutely limited, the NMR measurements can be made first, followed by moisture determination by the reference method on one part of the sample and oil determination on the other. Later, the reference moisture and oil values can be entered into the calibration file for correlating NMR signal/gram to the observed moisture and oil by the reference method. 

InstFileGenerator — Instrument file eonversion program that combines Macintosh state and calibration files and generates an Analyst instrument file (INS file). 

The corresponding matched peaks in tire calibration file are tlie calibration points. 

After the deconvolution step, giving the contribution coefficients of reference spectra (see Chapter 2), the parameters calculation is possible by using the same coefficients and a corresponding calibration file (Fig. 11). This calibration file includes the corresponding concentrations for specific compounds (nitrate, nitrite, anionic surfactants, etc.) and the values related to the reference spectra of mixtures (Table 3). The latter are statistically calculated for the purpose, through a preliminary stepwise regression study, from a set of at least 30 samples (with 30 corresponding values of parameters and 30 sets of contribution coefficients). 

For each basis of reference spectra, the choice of which is guided either by the knowledge of the sample origin, or the restitution error value, a corresponding calibration file... 

Table 3. Reference spectra contribution for urban wastewater calibration file...

For quantitative determination, the semi-deterministic procedure needs to use both a reference spectra basis and the corresponding calibration files (see Chapters 2 and 4). The value of nitrate concentration can then be calculated using the following relation ... 

Bajjalieh, N. Calibration data set of calibration file for soybean NIR testing on NIRSsystems 6500 from Caltest, LLC, Ballston Lake, NY made possible by United Soybean Board funding. Personal... 

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