Gas chromatography (GC) is a powerful analytical technique used to separate, identify, and quantify components of complex mixtures of gases or volatile liquids. It operates based on the differential partitioning of sample components between a stationary phase and a mobile phase, typically an inert gas such as helium or nitrogen. The sample is injected into a heated injector port, vaporizing the components and introducing them into the chromatographic column. As the components travel through the column, they interact with the stationary phase, causing separation based on differences in their partition coefficients. The separated components are detected by a detector at the end of the column, producing a chromatogram that represents the distribution of components over time. Gas chromatography is widely used in various fields including environmental analysis, pharmaceuticals, forensics, petrochemicals, food and beverage, and clinical diagnostics. It offers high sensitivity, resolution, and reproducibility, making it suitable for analyzing trace levels of analytes. Different types of detectors, such as flame ionization detectors (FID), electron capture detectors (ECD), and mass spectrometers (MS), can be coupled with GC to enhance selectivity and detection capabilities. GC analysis requires calibration with standards of known composition and validation to ensure accuracy and precision. Continuous advancements in GC instrumentation, column chemistry, and detector technology improve analytical performance and expand the range of applications for gas chromatography.