RCD (Rapid Component Detection) is based on a “model ion” that represents a characteristic ion (m/z value in MS1 spectra) for every detected component. The algorithm starts with component candidate detection and model ion selection and continues with the correlation of model ion profiles to confirm or reject a candidate.

To start automated component detection and the spectra deconvolution procedure using RCD algorithm:

1. Click on the Components Detection and the Spectra Deconvolution button and choose the RCD pop-up menu item

2. When the parameters setup dialog window appears, change the settings if required, and then click the Calculate button

The RCD algorithm dialog window contains various parameters that can be optimized for specific types of analysis:

Threshold of Total Signal: The program uses a different threshold level from the one given in the data file. In especially noisy chromatograms, setting the threshold higher can reduce the number of false positive results. However, if you feel the algorithm is too restrictive and is missing some chromatographic peaks, you can lower the default value.

Minimum Model Ion Abundance: The algorithms search for spectral peaks that have the most rapid rise and fall of signal in a peak region. This peak is called “model ion” in the program. To eliminate spikes and random fluctuations there is a minimum abundance value that a model ion should exhibit.

Smoothing: This option is used when noisy data needs to be analyzed. The program automatically determines the smoothing factor according to the signal-to-noise ratio. This value can be changed or the smoothing can be switched off. The program employs an exponential filter similar to the analogue RC filter.

Spectra Difference Factor: To eliminate false positive component detection, the adjacent components must show some degree of spectral dissimilarity that is represented as the match factor used in library searching. The spectra Difference Factor value is the minimal match factor between spectra that detected components should exhibit.

Background Subtraction: If you choose the Automatic option, the program attempts to find a region of relatively constant signal intensity before and after every peak and sets two background scans there. If you want to use the Manual option, set the background scans using the Set Background Subtraction Scan button before starting the detection and deconvolution process. Two manual background scans can be set anywhere in the chromatogram. If you choose the None option, background subtraction will not be performed.

Precursor Ion Subtraction: If a product ion chromatogram is being deconvoluted, the selected precursor ion can be subtracted from all scans to improve component detection. However, if a component does not fragment and only a precursor ion can be observed, the subtraction should not be applied because this component can be overlooked. Please note that Mass Frontier does not support scan events that are often used in connection with product ion scanning.

Retention Time Range: Detection and deconvolution calculations are time-consuming processes. The computing time needed depends on a number of factors, but the most significant are the number of scans and the number of mixture peaks. To speed up your work you can select only a part of a chromatogram to be analyzed. Other regions will be ignored.

Spectra Deconvolution: Two extraction algorithms can be applied, the choice will depend on the use intended for the component spectra. If components are intended for a library search, Sharp spectra deconvolution should be used. If the purpose of component detection is target analysis, you can elect to use Soft deconvolution. Generally, Sharp deconvolution subtracts peaks from coeluting components with a higher multiplication factor and so it produces spectra with fewer peaks and lower intensities of isobaric peaks than Soft deconvolution.