Meaning
Calibration methods in gas chromatography adjust the column inlet pressure to ensure that specific chemical compounds elute at identical times across different instruments. This software-driven technique of retention time locking allows laboratories to match chromatograms generated by different instruments or after column maintenance. It enables the quick identification of polymer additives and volatile impurities by comparing results directly with a master database.
The methodology is limited to gas chromatographic systems where electronic pneumatic control can dynamically regulate carrier gas pressure.
Chromatographic Control
Minor differences in column length, diameter and oven temperature can cause significant shifts in the peak positions of polymer extractables. Implementing retention time locking resolves this issue by standardizing the elution profiles across all connected systems in a global supply chain. It ensures that critical additives like slip agents always appear at their pre-defined times.
This consistency is essential when comparing resin datasheets from different polymer compounding plants.
Parameter Adjustment
Restoring column performance after injection-port contamination often requires trimming the head of the capillary column, which alters the carrier gas flow rate. With retention time locking, the system automatically adjusts the pressure to compensate for the shorter column length, returning the peaks to their locked positions. This calculation uses the elution time of a reference substance to calculate the necessary pressure offset.
It saves the technician from having to rebuild the entire calibration method from scratch, ensuring that the laboratory maintains a continuous testing schedule during peak production periods.
Laboratory Efficiency
High-volume moulding plants require continuous testing of incoming resins to prevent the processing of contaminated feedstocks. Using retention time locking reduces the time spent on manual peak identification and data verification. It allows for the automation of qualitative screening, raising the overall productivity of the quality control lab.
