Question

I am trying to analyze a sample containing hexamethylenediamine (HMD) dissolved in ethanol using GC-FID for an undergraduate chemical engineering project. The column used is Agilent DB-FFAP (high polarity). The program used was 95°C (hold for 6 min) followed by 7°C/min increase until 235°C (hold for 2 mins). Different concentrations of HMD were used, the highest being 0.1g/ml however none of the chromatograms showed peaks for HMD. There was always only one peak in each chromatogram. This was attributed to the solvent (ethanol). Are there any potential solutions to this problem? Is the problem with the type of column used? Should higher sample concentrations be used? Thanks in advance.

Answer 1

The issue with detecting HMD using GC-FID may be due to its low volatility and interference from the ethanol solvent. Considering derivatization to increase volatility or switching to an HPLC-MS/MS method with a C18 reversed-phase column could provide better results for separating and detecting HMD.

Step-by-step explanation:

If you are not obtaining peaks for hexamethylenediamine (HMD) on your GC-FID using the Agilent DB-FFAP column, it may be due to several reasons. Firstly, the volatility and the polarity of HMD could mean that it is not effectively separating on the high polarity column you are using.

Considering the low volatility of HMD, a derivatization step might be necessary before analysis to increase its volatility and therefore its detectability by GC. Derivatization would convert HMD into a more volatile compound suitable for GC analysis.

Secondly, the solvent choice and the concentration of HMD in your sample might also affect its detection. Ethanol could be masking the presence of HMD, especially if the HMD peak is small or close to the ethanol peak.

It might also be worth exploring the use of HPLC-MS/MS with a reversed-phase column such as C18 and a mobile phase that could better separate HMD from the solvent. HPLC methods, like the ones described above, offer more versatility for the detection of non-volatile and polar substances like HMD.

Appropriate mobile phases and gradients would need to be optimized to achieve good separation and detection of HMD.