Dear Samayita Chakraborty ,

Yes, polyhydroxybutyrate (PHB) or polyhydroxyvalerate (PHV) can be used as an external standard for measuring polyhydroxyalkanoates (PHAs) by gas chromatography (GC). The use of PHB or PHV as a standard allows for the quantification of PHAs in the sample by comparing the peak area or peak height of the PHA to that of the standard. However, it is important to ensure that the PHB or PHV used as the standard is of a similar molecular weight and structure to the PHA being measured, to ensure accurate and reliable results.

Quantifying polyhydroxyalkanoates (PHA) produced by methanotrophs, which contain both butyrate and valerate molecules, can be performed using a variety of analytical techniques such as high-performance liquid chromatography (HPLC), gas chromatography (GC), and Fourier Transform Infrared (FTIR) spectroscopy. In HPLC, the peaks corresponding to the butyrate and valerate molecules should appear as two separate peaks, each with its own retention time and peak area, allowing for quantification of each individual molecule.

For methylated PHA and PHB, quantification can be performed using similar techniques. However, the chromatography conditions may need to be optimized for the specific methylated PHA or PHB molecules being analyzed. Additionally, the use of mass spectrometry (MS) may be necessary for identification and quantification of methylated PHA and PHB molecules. The exact chromatography conditions and analytical techniques used for quantifying methylated PHA and PHB may vary depending on the specific sample and the molecule being analyzed.