When Hg-containing samples were fed into the discharge,
volatile Hg0 vapor was produced. All generated products issuing
from the plasma were swept by an argon stream through a
gas-liquid separator (GLS) and then to a commercial ICP-AES
spectrometer (Horiba Jobin-Yvon ACTIVA ICP-AES spectrometer,
Longjumeau, France) for detection (cf. Figure 2). The transfer
tube between the GLS and the ICP was about 60 cm (i.d. 4 mm),
with an internal volume calculated to be about 18 mL. The GLS
(shown in Figure 2) is a condenser-based design consisting of
two concentric tubes. The water-cooled condenser is 20 cm
(length) × 1 cm (i.d.) × 2 cm (o.d.). Coolant water circulating
through the condenser is held at approximately 5 °C. The
operating conditions of the ICP-AES instrument are as follows:
forward power 1200 W, outer and intermediate gas flows
14 L min-1 and 0.6 L min-1, respectively. The inner diameter of
the injector tube of the ICP torch was 2 mm. The central-channel
gas flow was optimized, as will be discussed later; the studied
range was from 0.5 to 1.1 L min-1.