Liquid Sample Introduction in ICP Spectrometry

A Practical Guide


  • José-Luis Todoli, Department of Analytical Chemistry, Nutrition and Bromatology, University of Alicante, Spain
  • Jean-Michel Mermet, Spectroscopy Forever, Tramoyes, France

Inductively coupled plasma atomic or mass spectrometry is one of the most common techniques for elemental analysis. Samples to be analyzed are usually in the form of solutions and need to be introduced into the plasma by means of a sample introduction system, so as to obtain a mist of very fine droplets. Because the sample introduction system can be a limiting factor in the analytical performance, it is crucial to optimize its design and its use. It is the purpose of this book to provide fundamental knowledge along with practical instructions to obtain the best out of the technique.
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Practitioners, researchers, instrumentation company engineers


Book information

  • Published: September 2008
  • Imprint: ELSEVIER
  • ISBN: 978-0-444-53142-1

Table of Contents

1. History-Introduction2. Specifications of a sample introduction system to be used with an ICP2.1 Introduction2.2 Physical properties of a plasma2.3 Energy delivered by the plasma2.4 Carrier gas flow rate and droplet velocity2.5 Desolvation and vaporization2.6 Plasma loading2.7 Organic solvents2.8 Ideal aerosol2.9 Chemical resistance2.10 Other constraints in sample introduction systems3. Nebulizers. Pneumatic designs.3.1 Introduction3.2 Mechanisms involved in pneumatic aerosol generation3.2.1 Wave generation3.2.2 Wave growing and break – up3.2.3 Need for a supersonic gas velocity3.2.4 Main pneumatic nebulizer designs used in ICP spectrometry3.2.5 Sample delivery3.3 Pneumatic concentric nebulizers3.3.1 Principle3.3.2 Different designs3.3.3 Possibility of free liquid uptake rate3.3.4 Critical dimensions3.3.5 Renebulization3.3.6 Nebulizer tip blocking3.3.7 Aerosol drop characteristics3.3.7.1 Influence of the gas and delivery rates on drop size distribution3.3.7.2 Spatial distribution and velocity 3.4 Cross flow nebulizers3.5 High solids nebulizers3.6 Parallel path nebulizer 3.6.1 Principle3.6.2 Critical dimensions3.7 Comparison of the different conventional pneumatic nebulizers3.8 Pneumatic micronebulizers3.8.1 High Efficiency Nebulizer (HEN)3.8.2 Microconcentric Nebulizer (MCN)3.8.3 MicroMist nebulizer (MMN)3.8.4 PFA micronebulizer (PFAN)3.8.5 Demountable concentric micronebulizers3.8.6 High efficiency cross-flow micronebulizer (HECFMN)3.8.7 Parallel Path Micronebulizer (PPMN) 3.8.8 Sonic Spray Nebulizer (SSN)3.8.9 Oscillating Capillary Nebulizer (OCN)3.8.10 High Solids MicroNebulizer (HSMN)3.8.11 Direct Injection Nebulizers3.8.11.1 Direct Injection Nebulizer (DIN) Direct Injection High Efficiency Nebulizer (DIHEN) Vulkan Direct Injection Nebulizer3.9 Comparison of micronebulizers4. Spray chambers4.1 Introduction4.2 Aerosol transport phenomena4.2.1 Droplet evaporation4.2.2 Droplet coagulation4.2.3 Droplet impacts4.3 Different spray chambers designs4.3.1 Double pass spray chamber4.3.2 Cyclonic type spray chamber4.3.3 Single pass spray chambers4.4 Comparison of conventional spray chambers4.5 Low inner volume spray chambers4.5.1 Aerosol transport and signal production processes at low liquid flow rates4.5.2 Low inner volume spray chamber designs4.5.3 Tandem systems4.6 Conclusions on spray chambers5. Desolvation systems5.1 Introduction5.2 Overview of the effect of the solvent in ICP-AES and ICP-MS5.3 Processes occurring inside a desolvation system5.3.1 Solvent evaporation5.3.2 Nucleation or recondensation5.4 Aerosol heating5.4.1 Indirect aerosol heating5.4.2 Radiative aerosol heating5.5 Solvent removal5.5.1 Solvent condensation5.5.1.1 Nucleation problem in the condenser5.5.1.2 Design of desolvation systems5.5.2 Solvent removal through membranes5.6 Design of desolvation systems5.6.1 Thermostated spray chambers. 5.6.2 Two steps desolvation systems. 5.6.3 Multiple steps desvolation systems.5.6.4 Desolvation systems based on the use of membranes5.6.5 Radiative desolvation systems5.6.6 Desolvation systems for the analysis of microsamples5.7 Comparison among different desolvation systems.6. Matrix effects6.1 Introduction6.1.1 Effect of physical properties on the sample introduction system performance Effects on the aerosol generation Effects on the aerosol transport6.2 Inorganic and organic acids 6.2.1 Physical effects caused by inorganic acids Influence on the sample uptake rate Influence on the aerosol characteristics Effect on the solution transport rate 6.2.2 Effects in the excitation/ionization cell 6.2.3 Effect of acids on analytical results. Key variables Acid concentration and nature Effect of the design of the sample introduction system Effect of the plasma observation zone and observation mode Effect of additional variables Effect on the equilibration time 6.2.4 Methods for overcoming acid effects 6.3 Easily and non easily ionized elements 6.3.1 Physical effects caused by easily ionized elements Influence on the aerosol characteristics Effect on the solution transport rate 6.3.2 Effects in the excitation/ionization cell 6.3.3 Effect of elements on ICP-AES analytical results. Key variables Effect of the interfering element concentration and nature Effect of the analyte line properties Effect of the nebulizer gas flow rate and RF power Effect of the plasma observation zone Effect of the plasma observation mode Influence of the liquid flow rate Effect of the liquid sample introduction system 6.3.4 Proposed mechanisms explaining the matrix effects in ICP-AES 6.3.5 Effect of elements on ICP-MS analytical results. Key variables6.3.5.1 Effect of the nebulizer gas flow rate6.3.5.2 Effect of the plasma sampling position6.3.5.3 Influence of the interferent and analyte properties and concomitant concentration Effect of the spectrometer configuration Additional variables 6.3.6 Proposed mechanisms explaining the matrix effects in ICP-MS 6.3.7 Methods for overcoming elemental matrix effects Internal standard and related methods Methods based on empirical modeling Methods based on the use of multivariate calibration techniques Sample treatment and other methods 6.4 Organic solvents 6.4.1 Effects on the performance of sample introduction system 6.4.2 Plasma effects 6.4.3 Effect of the operating conditions 6.4.4 Effect of the solvent nature 6.4.5 Effect of the liquid sample introduction system and the related parameters Conventional liquid sample introduction systems Low sample consumption systems Desolvation systems6.5. Conclusions7. Selection and maintenance of sample introduction systems7.1 Selecting a liquid sample introduction system. General aspects.7.2 Conditions that must be fulfilled by a liquid sample introduction system7.3 Sample introduction systems for particular kinds of samples or applications7.4 Selecting a nebulizer7.5 Selecting an aerosol transport device7.6 Peristaltic pump7.7 Diagnosis7.7.1 Use of Mg as a test element7.7.2 Measurement of the Mg II/Mg I ratio7.7.3 Procedure7.7.4 Non-exhaustive list of possible malfunctions7.8 Operation and troubleshooting of concentric nebulizers7.9 Operation, maintenance and troubleshooting of parallel pneumatic nebulizers7.10 Operation, maintenance and troubleshooting of spray chambers8. Applications8.1 Introduction8.2 Description of applications of low sample consumption systems8.3 Selected applications