Abstract: This article details the methods and necessity for detecting solvent residues in composite packaging, and also introduces the functions and services of the Languang Chromatography Analysis Laboratory. Keywords: Solvent residue, laboratory, gas chromatography, detection. The safety of polymer materials used in food packaging has always been a highly controversial issue. In the past, the debate often revolved around whether polymer materials would produce harmful free monomers during use. However, in recent years, numerous incidents of excessive residual solvents on packaging bags have brought the safety of polymer packaging bags back into the spotlight. With the mandatory implementation of 3C certification for food packaging, solvent residue testing of polymer materials is no longer optional. Composite materials are a commonly used packaging material, combining the excellent properties of various polymer materials to effectively extend the shelf life of products. Solvent residues in composite packaging generally originate from inks, solvents, and the production process. The quality and performance of the ink, the drying speed of the diluent solvent, the performance of the machine, the environment, and the packaging structure all affect the amount of solvent residue. Currently, the domestic packaging printing industry mainly uses organic inks, with high-temperature drying as the primary method for removing organic solvents. However, the evaporation rates of solvents such as toluene, methyl ethyl ketone (MEK), and ethyl acetate in the ink vary, resulting in inconsistent residual levels. When solvent residue exceeds a certain limit, it can contaminate the contents of the packaging, posing a health hazard to consumers. Solvent residue in composite packaging is generally sampled and tested after printing. The testing methods and standards follow national standards, stipulating that the total residual solvent content in packaged food should be ≤10mg/m2, with benzene-based solvent residue ≤3mg/m2. Residual solvents in packaging typically include toluene, xylene, MEK, isopropanol, butyl acetate, and ethyl acetate, varying depending on the specific materials and inks used. For flexible packaging manufacturers, many factors contribute to excessive solvent residue, such as improper substrate selection, non-standard production processes, outdated and rudimentary equipment, and a lack of necessary testing and control at each stage of production. Furthermore, issues such as unsuitable heating temperatures in the drying tunnel, insufficient drying airflow, uneven additive coating, and unreasonable production speeds in flexible packaging production equipment can also lead to excessive solvent residue levels in composite packaging. In fact, solvent residue testing of both raw materials and finished products is essential. Flexible packaging manufacturers can adjust production materials and processes based on actual test results to effectively improve product quality. Residue detection equipment is crucial. A specially configured gas chromatography workstation (software) can directly detect the names of various residual solvents in composite packaging and display their residual content (mg/m2), facilitating data analysis by testing personnel using relevant standards. It can also detect the purity of the solvents used. The Labthink GC-7800 gas chromatograph can complete the test in just 13 minutes. Programmed temperature rise is unnecessary, as it can cause baseline drift and introduce errors into the analysis. In principle, programmed temperature rise should be avoided unless there is a need for multi-component separation. The entire testing process mainly consists of several steps: gas chromatograph preheating, sample preparation, baking, sample gas sampling, injection into the gas chromatograph for testing, and obtaining test results (see Figure 2). [align=center] Figure 1. Standard Spectrum Figure 2. Solvent Residue Detection Structure Diagram[/align] Labthink Chromatography Analysis Laboratory Labthink expanded its laboratory in 2005, establishing the Labthink Chromatography Analysis Laboratory (Figure 3). This laboratory primarily focuses on research using chromatographic technology for aromatic odor blocking and solvent residue analysis in composite packaging. Equipped with multiple high-end gas chromatographs and complete auxiliary facilities, it provides services such as analytical method establishment, data detection, and personnel training for controlling solvent residue in packaging materials. Labthink GC-6890 and GC-7800 gas chromatographs specifically designed for detecting solvent residue in composite packaging are used in this laboratory to provide testing services for customer-submitted samples and to conduct inter-laboratory data comparison. In the future, the laboratory will also conduct in-depth and detailed exploration of the world's high-end research project on the permeation mechanism, selective control, and detection of organic gases into polymers. [align=center]Figure 3. Chromatography Analysis Laboratory[/align] Looking ahead, the development and use of benzene-free inks, water-based inks, and various environmentally friendly adhesives offer a bright prospect for completely solving the solvent residue problem in composite packaging. However, current price factors and the need to replace existing equipment limit their widespread use. Currently, achieving solvent residue standards in composite packaging requires improving existing production processes and strengthening detection mechanisms.