There have been significant advances in both analytical instrumentation and computerised data handling during the five years since the third edition was published in 1990. Windows-based computer software is now widely available for instrument control and real-time data processing and the use of laboratory information and management systems (LIMS) has become commonplace. Whilst most analytical techniques have undergone steady improvements in instrument design, high-performance capillary electrophoresis (HPCE or CE) and two- dimensional nuclear magnetic resonance spectrometry (2D-NMR) have developed into major forces in separation science and structural analysis respectively. The powerful and versatile separation technique of CE promises to rival high-performance liquid chromatography, particularly in the separ- ation of low levels of substances of biological interest. The spectral inform- ation provided by various modes of 2D-NMR is enabling far more complex molecules to be studied than hitherto. The electrophoresis section of chapter 3 and the NMR section of chapter 9 have therefore been considerably expanded in the fourth edition along with a revision of aspects of atomic spectrometry (chapter 8). New material has been included on fluorescence spectrometry (chapter 9), the use of Kovats Retention Indices in gas chroma- tography (chapter 3) and solid phase extraction for sample cleanup and concentration (chapter 12). Additions to high performance liquid chroma- tography (chapter 3) reflect the growing importance of chiral stationary phases, solvent optimization and pH control, continuous regeneration car- tridges for ion chromatography and HPLC-MS.