A microwave assisted desolvation system based on the use of a TM010 cavity for inductively coupled plasma based analytical techniques

Abstract

A new microwave assisted desolvation system based on the use of a TM 010 cavity (MWDS2) has been developed and evaluated in plasma based analytical techniques: inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The new design overcomes the main experimental drawbacks shown by previous designs based on the use of domestic ovens: (i) lack of control on microwave generation and application; and (ii) inappropriate MW cavity characteristics. The evaluation has been performed in terms of the effect of the incident microwave power and the sample uptake rate and the results obtained has been compared with those afforded by a conventional sample introduction system (nebulizer and double pass spray chamber) and a desolvation system based on the use of a domestic microwave oven (MWDS). The new MWDS2 give rise to higher analytical signals and lower limits of detection and stabilization times (2-3 times) than those obtained with the MWDS in ICP-AES and ICP-MS.

Introduction of organic solvent solutions into inductively coupled plasma-atomic emission spectrometry using a microwave assisted sample introduction system

“…Therefore, the aerosol vaporization process improves and, as a consequence, the analyte transport rate (W tot ) increases. 33 As regards the effect of Q l on the Mn emission signal, it can be observed in Fig. 1 i.e., 290 W, an increase in the sample uptake rate from 200 to 400 mL min À1 does not result in a signal reduction.…”

“…This factor is related to the amount of energy available by aerosol mass unit (i.e, to the amount of energy-to-mass ratio, EMR). [29][30][31]33,37 Thus, at low microwave incident powers, an increase in Q l gives rise to a decrease in the EMR, thus reducing the aerosol vaporization efficiency of the system. As a consequence, analyte losses along the sample introduction system increase due to: (i) drop impacts against the inner walls of the spray chamber; (ii) turbulence; and (iii) nucleation processes in the condensation unit.…”

“…30,31 Recently, a new and more appropriate design that overcomes the main experimental drawbacks shown by the older one has been presented (MWDS2). 33 The main advantages of the MWDS2 can be summarized as: (i) precise control of the incident and reflected microwave power; and (ii) adequate microwave cavity that makes it appropriate for the aerosol heating. 33 Using aqueous solutions, the MWDS2 provides higher analytical signals and lower limits of detection and stabilization times than those obtained with the former system both in ICP-AES and ICP-MS.…”

“…The nebulizer was coupled to the different microwave assisted sample introduction systems described in detail formerly: the previous design (so-called MWDS) and the MWDS2. 29,30,31,33 The main difference between the two systems was the microwave cavity employed. The MWDS uses the cavity of a domestic microwave oven, [29][30][31] whereas the MWDS2 employs a TM 010 microwave cylindrical cavity, specially designed for this purpose.…”

“…The MWDS uses the cavity of a domestic microwave oven, [29][30][31] whereas the MWDS2 employs a TM 010 microwave cylindrical cavity, specially designed for this purpose. 33 Its dimensions (9 cm inner diameter and 9.5 cm length) were calculated so as to obtain the maximum microwave field intensity in the spray chamber zone. The cavity has a hollow tuning screw (4.3 cm of internal diameter, 0.4 cm wall thickness and 20.5 cm length) placed at the center of the cavity to maintain the resonance frequency at (or close to) the nominal magnetron one.…”