A green analytical flow method was developed for the determination of total sulfite preservative in white wine. The method employs membraneless vaporization (MBL-VP) technique for gas-sample separation allowing direct analysis of wine. Sulfite in an aliquot of sample was converted to SO₂ gas via acidification. Dissolution of the gas into the water acceptor led to the change in conductivity of the acceptor which was monitored using a ‘capacitively coupled contactless conductivity detector’ (C4D) flow cell. Only a minute amount of common acid (100 µL of 1.5 mol L^-1 H₂SO₄) is used. The MBL-VP unit was incorporated into the flow system to separate the SO₂ gas from the wine sample using the headspace above donor and acceptor compartments as a virtual membrane. There is neither expense nor environmental waste from use of non-degradable membrane. The method provides linear working range (10-200 mg L^-1 sulfite) which is suitable for most wines with calibration equation y = (0.056±0.002)x + 1.10±0.22 and r² = 0.998. Sample throughput is 26 samples h^-1. The lower limit of quantitation (LLOQ = 3SD of blank/slope) is 0.3 mg L^-1 sulfite for 20 s diffusion time with good precision (%RSD = 0.8 for 100 mg L^-1 sulfite, n=10). We also present a simple modification of the MBL-VP unit by the addition of a third cone-shaped reservoir to provide two acceptor zones leading to improvement in sensitivity of more than three-fold without use of heating to enhance the rate of diffusion of SO₂.

中文翻译：

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绿色分析流动法无接触电导检测无膜气液分离法测定葡萄酒中的亚硫酸盐总量

建立了一种绿色分析流动方法，用于测定白葡萄酒中的总亚硫酸盐防腐剂。该方法采用无膜汽化（MBL-VP）技术进行气体样品分离，从而可以直接分析葡萄酒。等分试样中的亚硫酸盐通过酸化转化为SO ₂气体。气体溶解到水受体中会导致受体电导率的变化，可使用“电容耦合非接触电导率检测器”（C4D）流通池对其进行监测。仅使用微量的普通酸（100 µL的1.5 mol L ^-1 H ₂ SO ₄）。MBL-VP单元被合并到流系统中以分离SO ₂使用供体和受体室上方的顶部空间作为虚拟膜，从葡萄酒样品中提取气体。使用不可降解的膜既没有费用，也没有环境浪费。该方法提供了线性工作范围（10-200 mg L ^-1亚硫酸盐），适用于大多数具有校准方程y =（0.056±0.002）x + 1.10±0.22和r ² = 0.998的葡萄酒。样品通量为26个样品h ^-1。定量下限（LLOQ =空白/斜率的3SD）为0.3 mg L ^-1亚硫酸盐，扩散时间为20 s，精度良好（100 mg L ^-1的％RSD = 0.8亚硫酸盐，n = 10）。我们还介绍了MBL-VP单元的简单修改，方法是添加第三个锥形容器以提供两个受体区域，从而使灵敏度提高了三倍以上，而无需使用加热来提高SO的扩散速率₂。