Meinhard

TTie membrane interface coupled to an ICP is shown schematically in Fig. S.l. Two separators have been studied with membrane thicknesses of 12 and IS pm respectively. TTie interface with the thicker membranes used a Meinhard TR-20-C2 nebulizer rather than the more common TR-20-B2, because it is cheaper and better suited for this application (less cavitation). TTie outlets of the separators were at room temperature (20°C). 

Q. If you wished to nebulize sea-water with a Meinhard nebulizer, what would you have to do first, bearing in mind that sea-water contains 3.5% NaCl ... 

From the sample solution to be analyzed, small droplets are formed by the nebulization of the solution using an appropriate concentric or cross-flow pneumatic nebulizer/spray chamber system. Quite different solution introduction systems have been created for the appropriate generation of an aerosol from a liquid sample and for separation of large size droplets. Such an arrangement provides an efficiency of the analyte introduction in the plasma of 1-3 % only.6 The rest (97 % to 99%) goes down in the drain.7 Beside the conventional Meinhard nebulizer, together with cooled or non-cooled Scott spray chamber or conical spray chamber, several types of micronebulizers together with cyclonic spray chambers are employed for routine measurements in ICP-MS laboratories. The solvent evaporated from each droplet forms a particle which is vaporized into atoms and molecules... 

Meinhard or MicroMist nebulizer and cyclonic spray chamber... 

Figure 5.1 Main parts of an inductively coupled plasma mass spectrometer sample introduction systems (left column), e.g., Meinhard or MicroMist nebulizer with cyclonic spray chamber, ultrasonic nebulizer, microconcentric nebulizer and laser ablation system (all from CETAC Technologies), ion source (middle column) and several types of mass spectrometers, (a) Agilent 7500 from Agilent, (b) Platform from CV Instruments, or (c) Element from Thermo Fisher Scientific. (Parts of this figure were reproduced with permission from CETAC Technologies, Agilent, CV Instruments and Thermo Tisher Scientific, respectively.)...

Figure 5.14 Schematics a) of DIHEN (j.E. Meinhard Associates, Santa Ana, CA) ().S. Becker, H.J. Dietze, ].A. McLean and A. Montaser, Anal. Chem., 71, 3077 (1999). Produced by permission of American Chemical Society) and b) of microconcentric nebulizer (MCN 100, CETAC Technologies, Ohama. Reproduced by permission of CETAC Technologies)...

Characteristics such as the solution uptake rate, the sensitivity and the limit of detection for uranium determination using several nebulizers (Meinhard, MicroMist nebulizer, Q-DIHEN,... 

Meinhard, Andreas. The Dialogues of Andreas Meinhardi. A Utopian Description of Wittenberg and Its University. Ed. and trans. E. Reinke. Ann Arbor, 1976. 

Figure 5 Micronebulizers (a) Meinhard high-efficiency nebulizer (HEN), (b) Cetac microconcentric nebulizer (MCN).

Figure 7 Effect of nebulizer gas flow rate and sample uptake rate on primary and tertiary aerosol drop size distributions. A Meinhard TR-30 nebulizer was used with a double-pass spray chamber, (a) Primary aerosol produced by nebulizer as a function of nebulizer gas flow rate for a 1-mL/min sample uptake rate, (b) Tertiary aerosol exiting spray chamber as a function of nebulizer gas flow rate, (c) Primary aerosol as a function of sample uptake rate at a nebulizer gas flow rate of 0.8 L/min. (d) Tertiary aerosol exiting spray chamber as a function of sample uptake rate. (From Ref. 18.)...

The second type of direct injection nebulizer, called the direct injection high-efficiency nebulizer (DIHEN), is a specific type of the Meinhard HEN [38] that is inserted into the ICP torch in place of the center, injector tube. The main advantage of the DIHEN compared to the Cetac DEN is that a high-pressure pump is not needed to deliver sample to the nebulizer. An unusually low nebulizer gas flow rate (0.25 L/min) and high ICP power (1.5 kW) were found to provide optimal ICP-MS sensitivity when DIHEN is used [38]. 

To quantify the trace elements of interest plasma-based techniques were used, namely (i) ICP-AES using an Optima 3100 instrument (Perkin-Elmer, Norwalk, CT, USA) equipped with a cross-flow nebulizer and a Ryton Scott spray chamber (ii) Dynamic Reaction Cell (DRC) Q-ICP-MS using an Elan 6100 spectrometer (PerkinElmer, Norwalk, CT, USA) equipped with a quartz cross-flow Meinhard nebulizer and a cyclonic spray chamber (iii) SF-ICP-MS using an Elementl (ThermoElectron, Bremen, Germany) with a pneumatic nebulizer and a Ryton Scott spray chamber. 

ICP-MS is a multi-element technique suitable for the analysis of liquid samples, which provides higher selectivity and detection power and LoDs lower than other multi-element techniques, such as ICP-AES. These characteristics make ICP-MS an excellent tool for the detailed characterization of the elemental composition of beverages. In this context, ICP-MS was the technique selected for the determination of 31 trace elements in wine at concentrations ranging from 0.1 to 0.5 ng ml-1 [82]. Samples were diluted 1 + 1 and it was investigated whether a matrix effect derived from the presence of ethanol could be overcome by using a microconcentric nebulizer with membrane desolvation. The authors compared their results with those obtained using a conventional Meinhard nebulizer and concluded that the matrix effect observed could only be minimized by using an internal standard with the Meinhard nebulizer, but not with the other one. 

H. Meinhard and A. Gierer, J. Cell. Sci. 15 (1974) 312 H. Haken, Synergetik, Springer-Verlag, Berlin, 1990. 

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