Speaker
Almaz Saifutdinov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.3013.pdf
Development and fundamental investigation of He micro-plasma detector
PLES for gas chromatography
A. I. Saifutdinov1, S. S. Sysoev1, A. A. Kudryavtsev1,2
1
Saint Petersburg State University, St. Petersburg. Russia
2
Harbin Institute of Technology, Harbin, China
In analytical chemistry, gas chromatography (GC) has been widely used because of the
short measurement time and the low running costs.
In this study, a new type of GC detector using atmospheric pressure He plasma was
developed. He has the highest ionization (24.58 eV) and metastable (19.82, 20.62 eV) energies
among the elements. This means that He plasma can effectively ionize and excite all elements. In
the helium plasma ionization detector, DC-powered He plasma and ring-like electrodes were
utilized for ionization of the samples. For an ionization detector, the generation of very stable
plasma is important. Therefore, we used next configuration to initiation of DC He microplasma.
Two layers of ceramic of a thickness of 0.15 mm are interleaved with three layers of
tungsten of a thickness of 0.1 mm to fabricate the device. The discharge volume is defined by a
hole through the center of the sandwiched layers, and the micro-discharge uses a ring cathode
created by the hole in the outer tungsten cathode layer. A similar hole in the opposite outer
tungsten layer is used as a hollow anode. Device has a hole diameter of 400 mkm. The metallic
walls of the discharge volume are used as a wall probe. The anode is grounded and the cathode is
connected to the negative pole of the dc voltage source via a resistor of a few hundred kOhm.
The desired discharge current is chosen by adjusting the voltage and the resistor values. The
device is connected to out of microchromatograph column.
Samples of mixture was previously separated in a microchromatographic column and
then detected in a micro-plasma PLES-detector [1].
In addition to the time-dependent detection of the impurities analyzed in helium, impurity
detection was performed at the characteristic energies of the Penning electrons.
The energy spectra of the Penning electrons were obtained by measuring the second
derivative of the probe VA-characteristic (d2I/dV2) with respect to the scanning voltage applied,
which, according to the Druyvesteyn’s relation, is proportional to the EEDF [1,2]. The
Penning electrons’ energy spectra were obtained in He as the main gas with small admixtures of
Ar, N2 and O2.
The recorded energy spectra of Penning electrons at atmospheric He pressures are
characterized by the appearance of maxima at characteristic energies corresponding to the energy
of the electrons released in Penning reactions involving Ar, N2, O2 impurities. Well-expressed
maxima in the electron energy spectra are easily obtained as a result of the high number of
Penning electrons collected by the large sensor surface.
The effectiveness of the micro-plasma PLES-detector for GC was demonstrated by these
results. To further improve the analytical ability, the use of a RF power supply to PLES detector
is recommended because high-density plasma can be generated without the electrode
overheating.
The work was supported by Russian Science Foundation (RSF, grant № 17-79-20032).
REFERENCES
[1] Kudryavtsev A., Pramatarov P., Stefanova M. and Khromоv N. Journal of Instrumentation 7, PO7002,
2012.
[2] Kudryavtsev A. A., Saifutdinov A. I., Stefanova M. S., Pramatarov P. M., and Sysoev S. S. Physics of Plasmas
24, 054507, 2017.
