Organic Elemental Analyzer - CHN

440 Elemental Analyzer

  • Manufacturer: Control Equipment Corp. (now Exeter Analytical)
  • Model: CEC 440HA (2 units)
  • Features:
    • High-temperature combustion analysis
    • Simultaneous determination C, H, and N as weight percents
    • Horizontal combustion tube with removal of spent sample capsules
    • Autosampler tray (64 sample positions) sealed under helium during run
    • 5 - 6 minute analysis time per sample

General Description

Our instruments determine organic carbon, hydrogen, and nitrogen by means of high-temperature (1000C) combustion (Dumas method) of microgram to milligram size samples in an oxygen-enriched helium atmosphere. The combustion products (CO2, NOX (reduced to N2), and H2O), after chemical removal of potentially interfering gasses, are separated by means of sequential, selective chemical traps, and measured with three pairs of high-precision thermal conductivity detectors. Samples, which have been precisely weighed into small aluminum capsules, placed in protective nickel sleeves, and loaded into the autosampler wheel, are introduced into the combustion furnace by means of a mechanically operated quartz ladle. When combustion is complete, the ladle is withdrawn, and the sample and capsule residue in the nickel sleeve is deposited in a waste chamber (also sealed under helium during the run), thus avoiding buildup of sample residue in the combustion tube. Analysis results are reported in weight percent of the element.

In addition to solid sample materials, particulate organic matter trapped on glass fiber filters can be analyzed. Filters are not weighed, but are placed directly into nickel sleeves for analysis. (A nickel sleeve can accommodate a filter of up to 25mm diameter.) An arbitrary weight of 100mg is assigned to the sample, so the reported results are given directly in micrograms of the element on the filter.

The control software for the instruments is capable of having the autosampler deposit two sample capsules on the ladle for a single analysis. In this mode, called 'double-drop,' larger total sample weights (for low organic-content materials) and larger diameter glass fiber filters (up to 47mm) can be analyzed.