Convert Agilent ChemStation .ch files to CSV (Beta)

Agilent ChemStation writes every detector signal of a run into its own .ch file inside the .D folder: DAD1A.ch for the first diode-array signal, FID1A.ch for a flame ionization detector, ADC1A.ch for an analog input. The files are binary and compressed, so Excel, Origin or Python cannot open them. This page turns them into a plain CSV with retention time and response, without ChemStation and without going back to the instrument PC to export.

How to convert a .ch file to CSV

1. Upload one or more .ch files, or the whole .D folder packed as a .zip.
2. Choose the number format: decimal point with commas between columns, or decimal comma with semicolons for Excel in most European languages.
3. Download one CSV per signal, or the Excel workbook with a chart for every signal.

What the CSV contains

Two columns: Time (min) and the response, with the signal description and unit from the file in the header, for example DAD1A, Sig=280,4 Ref=off (mAU) or FID1A, Front Signal (pA). The values are scaled with the factor stored in the file and carry the unit the file names: mAU for UV and DAD signals, pA for FID, nRIU for refractive index detectors.

Which versions work

The .ch format changed over the years and the version sits at the start of every file:

• versions 30 and 130: LC signals (DAD, MWD, analog inputs) compressed as differences;
• versions 81 and 181: GC signals (FID) compressed as second differences;
• version 179: signals stored as plain numbers, from both "Asterix" and "Mustang" ChemStation, and the signals written by OpenLab CDS.

Versions 30, 81, 130, 179 and 181 were checked against the open-source readers rainbow, chromConverter and entab. The older version 8 is read the same way as version 30, but no sample file was available to test it.

Pitfalls

• A CSV exported by ChemStation is already text; it is refused with a hint to upload the .ch file.
• Version 181 files end with a padding value that is not a data point; it is left out, so the times stay on the instrument's sampling interval.
• Peak areas are not part of the .ch file; add the Report.TXT or zip the .D folder for them.

For the spectra of a diode-array detector, upload the .uv file as well, or see Open an Agilent .D folder without ChemStation.

More about what this tool reads and writes: Chromatography Data Converter (Agilent, Shimadzu, Waters, AIA).