Microwave-driven inductively coupled plasmas for analytical spectroscopy

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy Vol. 147; pp. 51 - 58
• Main Authors: Giersz, J., Jankowski, K., Ramsza, A., Reszke, E.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.09.2018; Elsevier BV
• Subjects: Analytical methods; Analytical spectroscopy; Annular-shaped microwave plasma; Argon; Components; Couplers; Detection; Erbium; Flow rates; Gas discharge tubes; Helium; Inductively coupled plasma; Metal detectors; Metals; Microwave-driven inductively coupled plasma; Microwaves; Plasma; Plasma jets; Shapers; Spectroscopic analysis; Spectroscopy; Spectrum analysis; Analytical spectroscopy; Microwave-driven inductively coupled plasma; Annular-shaped microwave plasma
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/j.sab.2018.05.022

New achievements in microwave-driven inductively coupled plasma (ICP) technology based on formation of homogeneous H-type field inside the plasma discharge tube by using both multi-helix and partial-turn couplers are discussed in detail. These couplers range from separate washers delivering longitudinal Ez and radial Er field components concentrated at the inner wall of the torch, through real multi-turn field shapers, which make the prevailing longitudinal Hz or hybrid EH field components, all the way to strait wires delivering a single radial Er field component with minimum at the axis. Two novel approaches utilizing either a ring washer coupler or a multi helix coupler are developed to generating atmospheric pressure annular-shaped microwave ICPs, suitable for analytical spectroscopy. They are stably operated with argon or helium at 1–2 L min−1 flow rates at a power level of 300 W while accepting up to 70 mg min−1 of water aerosol. For argon plasmas, rotational temperatures of OH (3300–4200 K) and electron number densities (1.9–2.2) × 1015 cm−3 are close to those measured in Ar ICP. Limits of detection for some metals were within the range of 0.006–0.035 mg L−1 using a portable OES detection system. [Display omitted] •New designs for generating ICP discharge at microwave frequency have been proposed.•Both multi-helix and partial-turn couplers provide H-type MW field distribution.•Both MICPs exhibit high rotational temperature values comparable to those for ICPs.