Mr. Bassford et al., AN AUTOMATED-SYSTEM FOR NEAR-REAL-TIME MONITORING OF TRACE ATMOSPHERIC HALOCARBONS, Analytical chemistry, 70(5), 1998, pp. 958-965
A new gas chromatographic method developed to quantitatively determine
important atmospheric halocarbons is described. Target compounds incl
ude replacement CFCs, chlorinated solvents, and biosynthesized (natura
lly produced) organohalogens, all trace gases in the atmosphere at con
centrations ranging from 0.1 to 600 pptv (where pptv = 1 part in 10(-1
2) by volume), A combination of ultralow concentrations and relatively
small electron attachment cross sections renders these compounds very
difficult to routinely measure in the background air typical of remot
e atmospheric monitoring stations, Detection is achieved by preconcent
ration of a 200-mL air sample using an adsorbent filled microtrap and
enhancement of electron capture detector response by oxygen doping one
of two detectors connected in series. Oxygen doping specifically targ
ets halocarbons with relatively poor electron attachment rate coeffici
ents. The work described here details construction of a novel analytic
al system, laboratory trials, and optimization followed by an extended
field campaign at a remote atmospheric monitoring station, Mace Head,
Ireland, A calibration standard or ambient air sample was acquired ev
ery hour using a cyclic, automated procedure without employing cryogen
ic preconcentration or refocusing. Overall precision of the analytical
method for the target compounds is between 0.3 and 1.5%.