Erlotinib: Characteristics, properties and analytical methods—Comprehensive review

Erlotinib (ERL), a first-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), continues to be a mainstay treatment for EGFR-driven cancers, especially non-small cell lung cancer. It is analytically challenging to determine ERL in pharmaceutical products and biological matrices with accuracy and reliability due to its limited therapeutic window, variable bioavailability, substantial metabolism, and low plasma concentrations. Therefore, quality control, pharmacokinetic analysis, stability evaluation, and therapeutic drug monitoring all depend on strong analytical techniques. The analytical methods for ERL determination that have been published over the last 20 years are critically compiled and assessed in this review. The spectroscopic, chromatographic, hyphenated, and electrophoretic techniques such as capillary electrophoresis, high-performance liquid chromatography (HPLC), high-performance thin-layer chromatography (HPTLC), UV-visible spectrophotometry, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are methodically examined. Alongside new developments like automation, green analytical chemistry, and sophisticated sample-preparation techniques, current analytical issues including matrix interference, solvent usage, and method scalability are discussed. This review offers a thorough analytical perspective intended to guide future development and technique selection for ERL analysis in clinical and pharmaceutical settings.