Motion sensitivity of flame ionization detectors

Abstract

A portable gas chromatograph, using a single flame ionization detector, was constructed. The unit was tested for response to surge, sway and heave accelerations up to 0.3g. Also the detector's response was studied for roll and pitch up to 25 degrees with periods ranging from 3 to 20 seconds. The effect on the detector's response of variation in hydrocarbon concentrations in the parts per million range was investigated and response increased with increasing concentration. Samples containing 1, 10, 100, 1000, and 10,000 parts per million dodecane were analyzed, and under the higher accelerations trace distortion was evident for concentrations below 10 parts per million. Stationary isothermal chromatograms of a normal alkane sample (nC6 - nC32) were compared with those obtained under the various test conditions and no detectable difference in peak area (which represented approximately 1 microgram of the particular hydrocarbon) or retention time was evident. The limits of detection for the Aerograph detector were found to be 21.8 x 10-6 mg/sec for a 30 degree roll, 29.1 x 10-6mg/sec for 20 degree pitching and 21.8 x 10-6 mg/sec for a 0.6g heave acceleration. For the range of translational and angular accelerations that might be expected on a platform at sea, it was found that medium resolution gas chromatography using a flame ionization detector can be conducted, but in the trace analysis region, trace distortion can be expected.