Conventional methods such as Ripper titration and aeration-oxidation (A-O) are widely used for the analysis of sulfur dioxide (SO2) in wine. However, the free SO2 reported by these procedures is overestimated due to dissociation of weakly bound SO2 forms during the analysis, particularly from anthocyanin-bisulfite complexes. “Truly” free SO2 in wine can be determined from the headspace SO2 concentration of an equilibrated wine sample. A headspace SO2 method based on gas detection tubes (HS-GDT) was recently described but is not readily automated. While solid phase microextraction (SPME) yielded poor precision in our experiments, our new method, based on static headspace gas chromatography and sulfur chemiluminescence detection (HS-GC-SCD), is readily automated and achieves high precision (<5%) and low limits of detection (0.033 mg/L molecular SO2, or ~1 mg/L free SO2 in wine at pH 3.5). A-O, Ripper, HS-GC-SCD, and HS-GDT methods were compared on a diverse set of wine samples. Results from HS-GC were correlated with those from the HS-GDT method (r2 = 0.92) and achieved higher precision (relative standard deviation = 3.7%). HS-GC was highly correlated with A-O in white wines (r2 = 0.85, slope = 0.90) but had weaker correlation for red wines (r2 = 0.71, slope = 0.44). The flexibility of GC for other procedures as well as its stability and low operating costs per sample make it an attractive option, and headspace methods have been shown to be better for predicting microbial stability in red wines.

中文翻译：

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测定葡萄酒中分子和“真正”游离二氧化硫：顶空方法与常规方法的比较

Ripper 滴定法和曝气氧化 (AO) 等常规方法广泛用于分析葡萄酒中的二氧化硫 (SO2)。然而，这些程序报告的游离 SO2 被高估了，因为在分析过程中弱结合的 SO2 形式发生了解离，特别是来自花青素-亚硫酸氢盐复合物。葡萄酒中“真正”的游离 SO2 可以通过平衡葡萄酒样品的顶空 SO2 浓度来确定。最近描述了一种基于气体检测管 (HS-GDT) 的顶空 SO2 方法，但不容易实现自动化。虽然固相微萃取 (SPME) 在我们的实验中精度较差，但我们基于静态顶空气相色谱和硫化学发光检测 (HS-GC-SCD) 的新方法很容易实现自动化并实现高精度 (<5%) 和低检测限 (0. 033 mg/L 分子 SO2，或在 pH 3.5 的葡萄酒中约 1 mg/L 游离 SO2）。AO、Ripper、HS-GC-SCD 和 HS-GDT 方法在一组不同的葡萄酒样品上进行了比较。HS-GC 的结果与 HS-GDT 方法的结果相关 (r2 = 0.92) 并获得更高的精度（相对标准偏差 = 3.7%）。HS-GC 与白葡萄酒中的 AO 高度相关（r2 = 0.85，斜率 = 0.90），但与红葡萄酒的相关性较弱（r2 = 0.71，斜率 = 0.44）。GC 对其他程序的灵活性以及稳定性和每个样品的低运行成本使其成为一个有吸引力的选择，并且顶空方法已被证明更适合预测红葡萄酒中的微生物稳定性。HS-GC 的结果与 HS-GDT 方法的结果相关 (r2 = 0.92) 并获得更高的精度（相对标准偏差 = 3.7%）。HS-GC 与白葡萄酒中的 AO 高度相关（r2 = 0.85，斜率 = 0.90），但与红葡萄酒的相关性较弱（r2 = 0.71，斜率 = 0.44）。GC 对其他程序的灵活性以及稳定性和每个样品的低运行成本使其成为一个有吸引力的选择，并且顶空方法已被证明更适合预测红葡萄酒中的微生物稳定性。HS-GC 的结果与 HS-GDT 方法的结果相关 (r2 = 0.92) 并获得更高的精度（相对标准偏差 = 3.7%）。HS-GC 与白葡萄酒中的 AO 高度相关（r2 = 0.85，斜率 = 0.90），但与红葡萄酒的相关性较弱（r2 = 0.71，斜率 = 0.44）。GC 对其他程序的灵活性以及稳定性和每个样品的低运行成本使其成为一个有吸引力的选择，并且顶空方法已被证明更适合预测红葡萄酒中的微生物稳定性。