浊点萃取-石墨炉-原子吸收光谱法测定镍铬合金牙冠在人工唾液中浸出的铬(Ⅵ)

GF-AAS Determination of Cr(Ⅵ) Extracted by Artificial Saliva from Ni-Cr Alloy Dental Crown with Separation by Cloud Point Extraction

将镍铬合金牙冠样品置于人工唾液10mL中,于37℃浸泡4周。分取此唾液2.00mL,加入2g·L^(-1)二苯碳酰二肼(DPC)溶液0.1mL,Triton X-114(5+95)溶液0.6mL及硫酸(1+1)溶液0.5mL,加水定容为10 mL后,于40℃加热20min,使铬(Ⅵ)与DPC络合并溶入Triton X-114相中,实现铬(Ⅵ)的浊点萃取分离。将黏稠的Triton X-114液相分出,加入硝酸与甲醇(1+99)混合液定容至1mL。按所述仪器工作条件用石墨炉-原子吸收光谱法测定其中的铬(Ⅵ)量,进样量为10μL。铬(Ⅵ)的质量浓度在5.0μg·L^(-1)以内与相应的吸光度呈线性关系,检出限(3s/k)为0.088μg·L^(-1)。分别加1.0μg·L^(-1)铬(Ⅵ)标准溶液于6件牙冠样品溶液中,按方法测定后求得平均回收率为96%。对同一样品重复测定6次,计算其相对标准偏差为3.8%。

The Ni-Cr alloy dental crown was soaked in 10 mL of artificial soliva and kept at 37 ℃ for 4 weeks. An aliquot of 2. 00 mL was taken from the extract and 0. 1 mL of 2 g . L-1 diphenylearbazide （DPC） solution, 0.6 mL of Triton X-114 （5＋95） as well as 0.5 mL of H2SO4（1＋1） were added. After diluting to 10 mL with water, the solution was heated at 40 ℃ for 20 min, to have the Cr（Ⅵ） separated in form of its complex with DPC by the cloud point extraction. The viscous Triton X-114 phase was separated from the water phase and diluted to 1 mL with a mixture of HNO3 and methanol （1＋99）. Chromium（VI） in this solution was determined by GFAAS under the prescribed working conditions of the instrument with 10 μL of the sample solution introduced. Linear relationship between values of absorbance and mass concentration of Cr（ Ⅵ ） was obtained in the range within 5.0μg . L-1 , with detection limit （3s/k） of 0. 088μg . L-1. Test for recovery was made by addition of 1.0 μg .L-1 of standard Cr（Ⅵ） solution to 6 dental crown samples, results of average recovery found was 96%. Precision was tested by analyzing the same dental crown sample for 6 determinations, the value of RSD found was 3.8%.