An extraction-free method requiring microliter (μL) volumes has been developed for the determination of caffeine in beverages. Using a pyrolysis-gas chromatography mass spectrometry system, the conditions required for the direct thermal desorption-gas chromatography mass spectrometry (TD-GC/MS) determination of caffeine were optimised. A 5 μL aliquot was introduced to the thermal desorption unit, dried, and thermally desorbed to the GC/MS. The response was linear over the range 10 to 500 μg/mL (R² = 0.996). The theoretical limit of detection (3 σ) was 0.456 μg/mL. No interferences were recorded from endogenous beverage components or from commonly occurring drugs, such as nicotine, ibuprofen, and paracetamol. Replicate caffeine determinations on fortified latte style white coffee and Pepsi Max® gave mean recoveries of 93.4% (%CV = 4.1%) and 95.0% (%CV = 0.98%), respectively. Good agreement was also obtained with the stated values of caffeine for an energy drink and for Coca-Cola®. These data suggest that the method holds promise for the determination of caffeine in such samples.

中文翻译：

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通过热脱附-气相色谱质谱法在微升饮料中无萃取物直接测定咖啡因。

无萃取法需要微升（μ L）卷已被开发用于咖啡因的饮料的测定。使用热解-气相色谱质谱系统，优化了直接热解吸-气相色谱质谱（TD-GC / MS）测定咖啡因所需的条件。将 5μL等分试样引入热脱附单元，干燥，然后热脱附到GC / MS。的反应是线性范围10至500  μ克/毫升（- [R ²  = 0.996）。检测（3所述的理论极限σ）为0.456  μ克/毫升。没有记录到内源性饮料成分或常见药物如尼古丁，布洛芬和扑热息痛的干扰。对强化拿铁风格的白咖啡和百事可乐进行重复的咖啡因测定，得出的平均回收率分别为93.4％（％CV = 4.1％）和95.0％（％CV = 0.98％）。对于能量饮料和可口可乐，咖啡因的规定值也获得了很好的一致。这些数据表明该方法有望用于测定此类样品中的咖啡因。