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Here you'll find general information on Mass Spectrometry to further your education.
Accurate Mass: Experimentally determined mass
Area Threshold (Analyst): Used to discriminate between peaks and noise spikes. This parameter is used after the noise threshold to confirm the potential start of peaks that pass the noise threshold test. After passing the test, pairs of bunched data points must continue to exceed the noise threshold, and the cumulative sum of the area slices on the leading edge must eventually exceed the area threshold for peak to be confirmed.
Average Mass: Sum of the atomic weights of the elements in a compound
Background Subtraction: Reduces the amount of noise in a chromatogram by subtracting either one or two selections containing noise from the selection containing peak. When a range is selected in the TIC, all the scans from that selection are internally averaged, and the resulting spectrum is subtracted from all the scans. In some cases, the resulting file might look close to the original scan.
Base Peak Chromatogram (BPC): Depicts the intensity of the largest peak in a scan as a function of time or scan number. The display is useful since it can distinguish between co-eluting components.
Baseline Subtraction Window: A time window (in minutes) around each data point used to determine the height of the baseline correction to be applied to that point. This serves to remove large ‘humps’ from the chromatogram. The baseline is defined as the line connecting the data point of minimum intensity on the left side of a given data point to the data point of minimum intensity on the right side of the specified window. The valid range of values is 0.00 to 10.00 minutes. Note: The value entered for the BSW is actually half of the window so that the total window applied to the data points is twice the entered value.
Bunching Factor (Analyst): Specifies the number of data points that are grouped to form one bunched point. Ideally, this value should be set so that there are approximately 12 data points for each peak, from start to end. This field allows you to set a punching factor for mass spectrometer, analog-to-digital converter (ADC), and diode array detector (DAD).
Chromatogram: A graphical display of the data obtained from the analysis of a sample in which the signal intensity is plotted along an axis showing either time or scan number.
Dynamic Fill Time (DFT): Adjusts the Linear Ion Trap fill time on-the-fly as sample intensity varies. By allowing the Analyst software to dynamically calculate the fill time, you can reduce the space charge effect of having too many ions in the LIT by using a short fill time and increase weak signals by allowing a longer fill time.
Dynamic Threshold Calculation (Analyst): This selection is useful when processing similar data sets. When the checkbox is enabled, the algorithm uses default values, which are dynamically estimated from the chromatogram, for peak-finding parameters. If left uncheck, the following parameters become available: Noise Threshold and Area Threshold.
Exact Mass: Sum of the most abundant isotopes of elements in a compound – theoretical calculation only.
Exponential Peak Ratio (Analyst): The ratio of the baseline-corrected height of the parent peak to the baseline-corrected height of the child peak. It is used to determine whether an exponential kim line will be used to calculate the area of the child peak eluting on the trailing edge of the parent peak. This ratio must be greater than the set value for the child peak to be skimmed. To disable exponential skimming throughout a run, you can set this parameter to its maximum value (1.0e+06).
Extracted Ion Chromatogram (XIC): An ion chromatogram created by taking intensity values at a single, discrete mass value, or a mass range, from a series of mass spectral scans. An XIC indicates the behavior of a given mass, or mass range as function of time. The intensity of the ion, or the summed intensities of all ions in a given range, is plotted in a chromatographic pane.
Integer Mass: Sum of protons and neutrons of an element
Ion Chromatogram: A graphical display of the mass spectral data obtained from the analysis of a sample in which the signal intensity is plotted along an axis showing either time or scan number. In the chromatogram display, the intensity, in counts per second (cps) or relative intensity (%), appears on the y-axis, while time or scan number appears on the x-axis.Chromatograms are not generated directly by the instrument but are generated from mass spectra in several ways (TIC, XIC, BPC)
Isotope Pattern: As the number of carbon atoms in the molecule increases, the peaks due to higher mass isotopes increase in relative abundance
Isotopic Abundance: The percent abundance of naturally occurring isotopes.
LC-MS/MS: The combination of using an HPLC with a mass spectrometer capable of generating product ions or fragment ions
Mass Spectrum: Data obtained from the mass spectrometer representing the masses and intensity of the ions with particular mass-to-charge (m/z) values
Monoisotopic Mass: Sum of the exact masses of the most abundant isotopes of elements in a compound. For example, most carbon atoms have a mass of 12 Da, but in nature 1.1% of C atoms have an extra neutron making their mass 13 Da
Noise Threshold (Analyst): Specifies a threshold, measured in counts per second, below which all data points are regarded as noise for both the mass spectrometer ADC and DAD. If the vertical difference between two consecutive data points is greater than the noise threshold. Analyst recognizes the potential start of a peak. The lower the noise threshold, the more sensitive peak detection will be. Conversely, raising the noise threshold decreases sensitivity. If the threshold is too high, Analyst Software may not be able to detect desired peaks.
Nominal Mass: Sum of the integer (or whole number) masses of the most abundant isotopes of the elements in a compoundSeparation height –this parameter affects how the baseline is determined for closely eluting peaks. It is the ratio of the valley between peaks to the height of the smaller peak. If this ratio is less than the set value, the peaks are considered to be separate, otherwise they are considered to be overlapping.
Separation Width: This parameter affects whether exponential skimming takes place. It is the ratio of the baseline-corrected height of the child peak to the height of the valley between the parent and child peaks above the baseline. This ratio must be less than the set value for skimming to take place.
Total Ion Chromatogram (TIC): A display created by summing the intensity contributions of all ions from a series of mass scans. The TIC provides a way of viewing an entire data set in a single pane. It consists of the summed intensities of all ions in a scan plotted against time in a chromatographic pane.
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© 2019 AB Sciex. For Research Use Only. Not for use in diagnostic procedures. The trademarks mentioned herein are the property of AB Sciex Pte. Ltd. or their respective owners. AB SCIEX™ is being used under license.
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