Rapid and accurate determination of carboxyl groups in carbon materials by headspace gas chromatography

This paper reports a novel and rapid method for determining carboxyl groups in carbon materials by headspace gas chromatography (HS-GC). Taking carboxylated carbon nanotubes (CNTs) as an example, the experiment based on GC measurement of carbon dioxide (CO₂) generated by complete reaction between carboxyl groups and sodium bicarbonate in a sealed vial, which showed that carboxyl groups in CNTs could be completely transformed into CO₂ under the equilibrium temperature at 60 °C for 10 min. The relative standard deviation (RSD) of this method in the repeatability test was less than 1.52%, and the limit of quantitation (LOQ) for carboxyl content was 0.014 mmol/g in CNTs. More significantly, appropriate ultrasound of the sample before headspace injection could greatly improve the detection efficiency by reducing the equilibrium time. All in all, the HS-GC method provides an automated and accurate analysis for testing carboxyl groups in carbon materials, and it is of profound significance to develop a new way for quantitative research of carbon materials.