Ce ms data import and parsing

CE-MS data import and parsing

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Summary

Load and parse raw capillary electrophoresis–mass spectrometry (CE-MS) data from standard formats (mzML, netCDF) into R memory structures that preserve spectral, mobility, and mass-to-charge information for downstream transformation and feature extraction. This is the foundational step that enables reproducible analysis of CE-MS electropherograms.

When to use

You have raw CE-MS instrument output in mzML or netCDF format and need to extract specific ion traces (by m/z value), filter by effective mobility windows, or apply transformations to migration time data. Use this skill when beginning a CE-MS analysis pipeline or when integrating new CE-MS datasets from different instruments or electroosmotic flow regimes.

When NOT to use

• Input data is already a feature table, peak list, or aggregated matrix — use this skill only for raw instrument files.
• You need only summary statistics (total ion chromatogram, mass accuracy report) without storing full spectral detail — lighter summarization tools may be more efficient.
• Data has already been converted to a different format (e.g. mzXML, HDF5) in a prior step — use format-specific parsers for those formats.

Inputs

• Raw CE-MS data file (mzML format)
• Raw CE-MS data file (netCDF format)
• Instrument metadata (electroosmotic flow parameters, capillary dimensions, applied voltage)

Outputs

• Spectra object (R) containing all scans with m/z, intensity, and migration time
• MSnbase Spectrum2 collection with spectral annotations
• Data table of scan-level metadata (scan number, migration time, polarity, precursor m/z if applicable)

How to apply

Load raw CE-MS data using the Spectra or MSnbase package, which parse mzML or netCDF files into R spectral objects preserving m/z, intensity, and retention time (migration time) metadata. Verify that the loaded object contains the expected m/z range, number of scans, and scan-level metadata (polarity, activation, precursor masses if MS/MS). Check that migration time values span the expected range for your CE method and that no scans are missing or corrupted. Store the parsed object for use in downstream m/z extraction, effective mobility transformation, and peak detection workflows.

Related tools

• Spectra (Primary package for loading and representing CE-MS spectral data from mzML and netCDF into R; provides low-level access to m/z and intensity arrays and metadata.)
• MSnbase (Alternative/complementary package for importing and working with mass spectrometry data objects, including CE-MS; supports object-oriented access to spectral data.)
• msdata (Provides reference CE-MS test datasets in mzML format for development and validation of import and parsing workflows.)
• BiocManager (Bioconductor package manager used to install Spectra, MSnbase, and related CE-MS analysis packages.)

Examples

library(Spectra); library(msdata); mzml_file <- system.file('TripleTOF5600/PestMix_Pos_5uLInj_01_Infusion.mzML', package='msdata'); sp <- Spectra(mzml_file); sp

Evaluation signals

• Spectra or MSnbase object is successfully created with non-zero scan count and all expected metadata fields (m/z array, intensity array, migration time, polarity).
• m/z values span the expected instrument range (e.g. 50–2000 m/z for typical CE-MS) and match the known analyte mass ± instrument accuracy.
• Migration time values are positive, monotonically increasing across scans, and consistent with the expected CE run duration (typically 10–100 min).
• No NaN, Inf, or missing values in critical fields (m/z, intensity, migration time); any flagged scans have documented reasons (e.g. low signal, detector saturation).
• Extracted ion trace for a known internal standard or reference compound (e.g. Lysine m/z 147.112806) returns a non-empty signal and peak-like intensity profile across the migration time window.

Limitations

• Effective mobility transformation requires electroosmotic flow correction metadata that may not always be embedded in raw mzML/netCDF files; manual entry or external calibration may be needed.
• Some older CE-MS instruments or local data export formats may not produce standards-compliant mzML or netCDF; custom parsers or format conversion may be required.
• Large raw files (>1 GB) may exceed available RAM if fully loaded into memory; chunked or lazy-loading strategies may be necessary.
• netCDF format support depends on system netCDF library availability; mzML is more portable across platforms.

Evidence

• [other] Load raw CE-MS data (mzML or netCDF) containing Lysine signal using Spectra or MSnbase.: "Load CE-MS raw data (mzML or netCDF) containing Lysine signal using Spectra or MSnbase."
• [intro] The transformation is performed using functionality from the packages Spectra, MSnbase, xcms, and MetaboCoreUtils.: "The transformation is performed using functionality from the packages r BiocStyle::Biocpkg("Spectra")"
• [intro] There is no R implementation for CE-MS effective mobility transformation prior to MobilityTransformR.: "there is no implementation in R that performs effective mobility transformation of CE-MS(/MS) data"
• [intro] CE-MS test data are provided in the msdata package for development and validation.: "The CE-MS test data are from the r BiocStyle::Biocpkg("msdata") package"
• [readme] Installation via BiocManager provides stable versions of import and analysis packages.: "To install MobilityTransformR, use the stable version available at Bioconductor."