CHNS

CHNS stands for carbon, hydrogen, nitrogen, and sulfur. In scientific contexts, CHNS analysis refers to the qualitative and quantitative determination of these elements in a sample using elemental analyzers.

CHNS analyzers combust a weighed sample in oxygen at high temperature, converting carbon to CO2, hydrogen to H2O, nitrogen to N2, and sulfur to SO2. The combustion products are carried by a purge gas to detectors that quantify the amounts. Infrared detectors measure CO2 and H2O; nitrogen is typically measured by a chemiluminescence or by a thermal conductivity detector; sulfur as SO2 is detected by infrared or a specific detector. The data are converted to weight percentages or micrograms per gram; results may include oxygen not measured and mass balance check.

Commonly used in organic chemistry, polymer science, pharmaceuticals, petrochemicals, environmental science, and materials science to verify composition and purity. Samples are prepared as small, uniform masses, often in tin or quartz capsules; typical mass is a few milligrams to a few tens of milligrams for solids, or by using a microbalance for liquids. Instruments are automated and require calibration with certified reference materials.

Accuracy and precision depend on instrument type, calibration, and sample type but typical repeatability is around ±0.1–0.3 percentage points for major elements in well-behaved samples. CHNS analysis is widely used for quality control, method development, and research.