Analytical chemistry studies and uses instruments and methods used to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separation isolates analytes. Analytical chemists assess the chemical structure and nature of substances. Their skills are needed for a variety of purposes including drug development, forensic analysis and toxicology. Analytical chemists can specialise in areas as varied as toxicology, pharmaceuticals and forensics.