Comparison of desolvation effects with aqueous and organic (carbon tetrachloride) sample introduction for inductively coupled plasma atomic emission spectrometry

Pérez

et al. 2006

A microwave assisted sample introduction system based on the use of a TM 010 cavity (MWDS2) has been employed for the introduction of 10% w/w organic solvent solutions in inductively coupled plasma atomic emission spectrometry (ICP-AES). Ethanol, propan-2-ol, formic and acetic acids have been used. Firstly, the effect of the incident microwave power and the sample uptake rate on the emission signal was evaluated. For all matrices tested, the higher emission signals were obtained when operating at the highest microwave power (i.e., 290 W) and sample uptake rate (400 mL min À1 ). Results with the MWDS2 were compared with those afforded by a desolvation system based on the use of a domestic microwave oven (MWDS) and by a conventional sample introduction system (CS). The MWDS2 provides the highest emission signals (up to 7 and 17 times higher than those with the MWDS and the CS, respectively). As regards the matrix effects originated by the organic solutions, results demonstrate that the use of a microwave-based sample introduction system, mainly the MWDS2, affords a noticeable reduction in the matrix effects originated by the use of organic solvent solutions in ICP-AES with a conventional sample introduction system. This behaviour can be explained by taking into account the solution transport rates afforded by the different sample introduction systems. For all the analytical lines and matrices tested and operating at 400 mL min À1 , the MWDS2 gives rise to signal values that are, on average, 1.2 AE 0.2 times the signal obtained with water. For the MWDS and the CS, this factor takes values of 1.6 AE 0.2 and 2.0 AE 0.5, respectively. Transient matrix effects have been observed operating with the MWDS2 when switching between water and an organic matrix solution. These transient effects result in a drift time about 4.5 times higher than those with a CS.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Pérez

et al. 2006

“…Nonetheless, excessive solvent (or matrix) loading can deteriorate excitation conditions, giving rise to a decrease in the emission intensity. 27 W tot can be used to evaluate the analyte transport rate, and Mg ratio 28,29 or Ar intensity to measure the plasma excitation conditions. 30,31 Results indicate that there is no influence of MW power on Mg ratio and Ar intensity for all conditions studied in Fig.…”

Section: Resultsmentioning

confidence: 99%

Design and evaluation of an improved microwave-based thermal nebulizer for liquid sample introduction in inductively coupled plasma atomic emission spectrometry

Mora

et al. 2008

A re-designed microwave-based thermal nebulizer (MWTN) that overcomes all the drawbacks shown by previous prototypes (i.e. lack of robustness, poor heating efficiency) is presented. The new device employs an optimized TM 010 cavity and nozzle design. MWTN performance was evaluated in inductively coupled plasma atomic emission spectrometry (ICP-AES) and compared to that provided by a concentric pneumatic nebulizer. Current MWTN design improves sample heating efficiency and system robustness. As a consequence, a 10 times lower matrix concentration than previous designs can be employed. The minimum inorganic (i.e. acids and salts) and organic (i.e. alcohols) concentrations required to nebulize are 0.25 and 40% w/w, respectively. The influence of microwave power (180-290 W), matrix nature (acids, salts and organics), sample uptake rate (0.9-1.8 mL min À1) and nebulizer critical dimensions, such as nozzle and PTFE capillary internal diameter (150-300 and 300-800 mm) and PTFE capillary length (50-150 cm) on the behaviour of the MWTN was studied. Optimum operating conditions for this nebulizer are obtained employing high microwave powers, matrix concentration and sample uptake rate, as well as nozzle and PTFE capillary with a narrow internal diameter. Although the MWTN behavior depends on the samples physical properties, aerosol drop size distributions and analyte transport rate for inorganic solutions above 2% w/w are independent of matrix composition. Current MWTN shows higher sensitivity and lower limits of detection (up to 12 times for acid solutions) than a conventional pneumatic nebulizer. The performance of the new prototype has been evaluated analyzing a certified bovine liver (CRM 185 R) and a spirit sample. Experimental results indicate that MWTN can be employed successfully for routine sample analysis.

“…As a consequence, the plasma energy available for analyte atomization and excitation may decrease, thus reducing the expected sensitivity enhancement. 11,12 In order to avoid the negative influence of the amount of solvent reaching the plasma, the use of these so-called ''high efficient'' nebulizers usually demand a desolvation system. [13][14][15] In those systems, the aerosol generated by the nebulizer (primary aerosol) is firstly heated using either conductive (e.g., using a heating tape) 16 or radiative (e.g., infrared or microwave radiation) devices.…”

Section: 2mentioning

confidence: 99%

Design and evaluation of a new fully microwave-assisted liquid sample introduction device for inductively coupled plasma atomic emission spectrometry

Montiel

et al. 2010

A new fully microwave-assisted liquid sample introduction system (MASIS) is presented and evaluated in Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The device employs a single TM 010 microwave cavity for the simultaneous aerosol generation and desolvation. The different experimental requirements of both physical processes demand a careful system design and a judicious selection of the experimental conditions. The behavior of the MASIS depends on the: (i) microwave power; (ii) nebulizer nozzle inner diameter; (iii) sample uptake rate; and, (iv) matrix nature (i.e. acids, salts) and concentration. Thus, optimum operating conditions are obtained when increasing the microwave power, the matrix concentration and the sample uptake rate as well as when decreasing the nebulizer nozzle inner diameter. The analytical figures of merit afforded by the MASIS in ICP-AES are compared to those obtained with: (1) a pneumatic concentric nebulizer coupled to a cyclonic spray chamber (CS); (2) a microwave thermal nebulizer (MWTN) coupled to a cyclonic spray chamber; and (3) a pneumatic nebulizer coupled to a microwave desolvation system (MWDS). MASIS provides limits of detection up to 50 times lower than those obtained with the CS and up to 8 times lower than those with the MWTN and MWDS. No significant difference in the signal precision between the different devices tested is observed (i.e. 2-5%). Regarding the wash-out times, both MASIS and MWDS show the highest values of this parameter (i.e. 70 s) due to their higher inner volume. Wash-out time values for both MWTN and CS are lower than 30 s.