在火焰原子吸收光谱测定水样中痕量镉的方法中,提出了在流动注射-编结反应器对痕量镉离子作在线预富集中用两次引入作为镉离子的配位体的吡咯烷二硫代氨基甲酸铵(APDC)溶液的模式.在此模式中,预先将APDC溶液涂覆在编结反应器的内壁上(这就是第一次引入APDC溶液);第二次引入是将APDC溶液与试样溶液同时注入并在编结反应器中汇合.富集时样品溶液的流速为6.0 mL·min-1,富集时间为60 s.按此方法操作镉的富集系数达到21,此值均高于单独用APDC溶液预涂覆编结反应器模式的富集系数(9)或单独用APDC溶液与试样溶液同时注入并汇合模式的富集系数(16).方法的检出限(S/N=3)为0.32 μg·L-1,方法的进样频率为每小时36个样品,对20 μg·L-1镉标准溶液测定11次,测得方法的相对标准偏差为2.7%.应用此方法测定了几个水样中镉含量,并作回收试验,所得回收率在92.0%~99.0%之间.

In the FAAS determination of trace amounts of cadmium in water sample,on-line preconcentration of Cd2+ ion with flow injection knotted reactor was adopted,in which 1-pyrrolidine carbodithioic acid (ammonium salt,abbreviated as APDC) was used as ligand for Cd2+,and the mode of duplicate introduction of the APDC solution into the reactor was introduced. The APDC solution was pre-coated on the inner wall of the knotted reactor (KR),i.e.,the 1st introduction of APDC solution;and the 2nd introduction of APDC solution was carried out simultaneously with the introduction of sample solution. Flow-rate of sample solution in the FI-preconcentration was taken as 6.0 mL·min-1,and the time for preconcentration was taken as 60 s. Concentration factor of Cd2+ by this method attained to a value of 21,which is higher than the values 9 and 16 attained by either the mode of pre-coating on the inner wall of KR or the mode of introduction simultaneously with the sample solution separately. Detection limit (S/N=3) of the method found was 0.32 μg·L-1,and the sampling frequency of 36 samples per hour was achieved. Precision was tested at the concentration level of 20 μg·L-1 of Cd2+,value of RSD (n=11) obtained was 2.7%. In analyzing several water samples by this method,in which (w) 0.01% triethanolamine solution was added as masking agent,values of recovery found were in the range of 92.0%-99.0%.