A simple, fast and green homogeneous liquid–liquid microextraction (HLLME) method based on solvents volume ratio alteration (SVRA) combined with gas chromatography–mass spectrometry (GC–MS) was developed for the preconcentration and determination of caffeine in tea and coffee samples. In the proposed HLLME-SVRA method, the primary extraction from solid samples was achieved by a 2:1 ethanol-water mixture. A micro-volume of dichloromethane (DCM) formed a homogeneous solvent with this mixture after choosing an appropriate volume ratio between the three solvents. After vigorous shaking, an extra volume of water was added that resulted in phase separation due to the solvents volume ratio alteration. As a result, complete extraction of caffeine was achieved after centrifugation. The sedimented dichloromethane phase was then injected into GC–MS for the analysis. The influence of a number of parameters influencing the efficiency of the extraction was investigated and optimized. Under the optimal conditions, an enrichment factor of 11, a limit of detection of 0.05 μg mL⁻¹ and a limit of quantification of 0.16 μg mL⁻¹ were obtained for caffeine. A linear dynamic range of 0.16 to 50 μg mL⁻¹ and a determination coefficient (R²) of 0.9980 were achieved. The precision of the method, expressed as relative standard deviation, was 4.8% for six replicated measurements. The method was successfully applied to the determination of caffeine in tea and coffee samples.

建立了一种基于溶剂体积比变化（SVRA）结合气相色谱-质谱（GC-MS）的简单，快速，绿色均质液液微萃取（HLLME）方法，用于茶叶和咖啡样品中咖啡因的预浓缩和测定。在提出的HLLME-SVRA方法中，通过2：1乙醇-水混合物完成了从固体样品中的初步提取。在三种溶剂之间选择适当的体积比后，微量的二氯甲烷（DCM）与该混合物形成了均相溶剂。剧烈摇动后，由于溶剂体积比的改变，加入了额外体积的水，导致相分离。结果，在离心后，咖啡因被完全提取。然后将沉淀的二氯甲烷相注入GC-MS中进行分析。研究和优化了许多影响萃取效率的参数的影响。在最佳条件下，富集因子为11，检出限为0.05μgmL咖啡因的定量值为^-1，定量限为0.16μgmL ^-1。线性动态范围为0.16至50μgmL ^-1，测定系数（R ²）为0.9980。对于六次重复测量，该方法的精度（以相对标准偏差表示）为4.8％。该方法已成功应用于茶叶和咖啡样品中咖啡因的测定。