气浮浮选分离富集-紫外分光光度法测定水中痕量强力霉素

UV Spectrophotometric Determination of Trace Amounts of Doxycycline in Water with Separation and Enrichment by Gas Floatation

水样中痕量的强力霉素（DXCC）用正丙醇及无水乙醇（4＋1）作混合溶剂，从pH8的溶液中进行气浮浮选使之分离并富集。加入氯化钠作为分相剂，加入铁（Ⅲ）使与DXCC反应生成憎水的络合物而浮选入有机相，在383nm波长处测定有机相的吸光度。吸光度与DXCC浓度在3．1×10^-7～2．0×10^-5mol·L^-1范围内呈线性关系，方法的检出限（3S／N）为2．6×10^-7mol·L^-1，测定中采用自制的气浮浮选装置。应用所提出的方法分析了3种不同来源的水样，并以此样品作为基体用标准加入法对方法的回收率进行了测定，测得方法的平均回收率为99．7％，测定值的相对标准偏差（n=5）均小于2．5％。

Trace amounts of doxycycline （DXCC） in water sample were seParated and enriched by gas floatation with hydrophilic solvent mixture of n-propanol and absolute alcohol（4＋1）, from a solution adjusted to pH 8 with 0. 01 mol·L^-1 NaOH solution. Sodium chloride was added as phase separating agent, and 1 ×10^-4 mol·L^-1 Fe（NO3）3 solution was added to react with DXCC forming a hydrophobic complex, which was floated into the organic phase. Absorbance of the organic phase was measured photometrically at the wavelength of 383 nm. Linear relationship between values of absorbance and concentration of DXCC was obtained in the range of 3. 1×10^-7--2.0×10^-5 mol·L^-1. Detection limit （3S/N） of the method found was 2. 6×10^-7 mol·L^-1. A self-made floutation installation was used in the determination. Samples of water from different sources were analyzed by the proposed method, and test for recovery was made by standard addition method using these samples as matrixes, giving values of average recovery of 99. 7% and RSD＇s （n=5） less than 2. 5%.