称取经粉碎研磨的聚氯乙烯（PVC）塑料样品（2.500 0 g），加入碱性提取剂（每升溶液中含20.0 g氢氧化钠和30.0 g无水碳酸钠）50 mL和pH 7.0的磷酸盐缓冲溶液0.5 mL，再加入0.4 g无水氯化镁和2滴辛基苯基聚氧乙烯醚进行微波消解提取，所得提取液经减压过滤，收集滤液和洗涤液。调节此溶液的pH至7.5±0.5，并用水定容至100.0 mL，经0.45 μm滤膜过滤，取滤液供反相离子对色谱-电感耦合等离子体质谱法分析。选用XTerra-C₁₈反相色谱柱作为固定相，流动相为2 mmol·L^-1四正丁基硫酸氢铵溶液（此溶液每升中含甲醇50 mL，并调节pH至7.0），流量为1.0 mL·min^-1，进行等度洗脱。在此条件下，Cr（Ⅲ）与Cr（Ⅵ）可按其保留时间的不同达到很好分离，Cr（Ⅲ）与Cr（Ⅵ）的保留时间分别为1.732，4.966 min。质谱测定中采用单氦气碰撞反应模式消除多原子离子的干扰。Cr（Ⅵ）的质量浓度在0.50~200 μg·L^-1内与其对应的峰面积呈线性关系，检出限（3S/N）为0.10 μg·L^-1。应用此方法分析PVC标准物质[RMA 034，其中Cr（Ⅵ）的认定值为（9.3±0.9） mg·kg^-1]，Cr（Ⅵ）的测定值为9.19 mg·kg^-1，其相对标准偏差（n=6）为2.2%，还用此方法分析了3种PVC的日常用品，并用标准加入法进行回收试验，测得回收率为94.2%~101%。

A portion of the ground polyvinyl chloride (PVC) plastics sample (2.500 0 g) was taken and 50 mL of an alkaline extraction solution (containing 20.0 g of NaOH and 30.0 g of Na₂CO₃ per liter) together with 0.5 mL of pH 7.0 phosphate buffer solution, 0.4 g of MgCl₂ (anhydrous), 2 drops of Triton X-100 was added to the sample. The mixture was digested in a microwave oven. The extract was filtered by vacuum suction and the filtrate together with the washing water were collected and mixed, with its pH adjusted to 7.5±0.5 and its volume made up to 100.0 mL with water. The solution, after filtered through 0.45 μm filtering membrane, was used for RP-HPLC-ICP-MS analysis. The reversed phase chromatographic column of XTerra-C₁₈ was selected as stationary phase, and 2 mmol·L^-1 TBA solution (50 mL of CH₃OH was added to 1 L of this solution and its pH was adjusted to 7.0) was used as mobile phase in isogredient elution, with flow rate of 1.0 mL·min^-1. Separation of Cr(Ⅵ) from Cr(Ⅲ) was achieved by the difference of retention times[i.e., 1.732 min for Cr(Ⅲ) and 4.966 min for Cr(Ⅵ)] under the condition mentioned above. The interference of multiatomic ions was attained by applying the mode of single He collision reaction in MS determination. Linear relationship between mass concentration of Cr(Ⅵ) in the range of 0.50 to 200 μg·L^-1 and values of respective peak areas was obtained. Detection limit (3S/N) found was 0.10 μg·L^-1. A CRM of PVC[RMA 034, with certified value of Cr(Ⅵ) of (9.3±0.9) mg·kg^-1] was analyzed for its Cr(Ⅵ) content by the present method, giving result of Cr(Ⅵ) (9.19 mg·kg^-1), and with RSD (n=6) of 2.2%. Three PVC utensils were analyzed by this method, and using these samples as matrixes, test for recovery was made by standard addition method, giving results in the range of 94.2% to 101%.