FI-KR-FAAS空气混合吸附二次气体分隔洗脱法测定海洋生物样中的痕量铅

建立了流动注射（flow injection, FI）空气混合吸附预富集编结反应器（knotted reactor, KR）二次气体分隔洗脱法与火焰原子吸收光谱法（flame atomic absorption spectrum, FAAS）联用测定海洋生物样中的痕量铅。在预富集步骤，空气、络合剂和铅溶液在线混合，空气的引入，大大提高了铅的螯合物在KR内壁的吸附效果。在洗脱前，通入一段空气流，在洗脱过程中，即在非完全洗脱时，加入一段空气流，两段空气流的引入，大大降低了被分析物在洗脱液中的分散，提高了信号响应值，从而提高了浓集系数（enhancement factor, EF）。将空气混合吸附预富集与二次气体分隔洗脱法联用，使得KR吸附富集效果和洗脱效果达到了更高的水平。和微柱的低寿命、高反压相比，KR反压小，耐酸耐碱，寿命几乎无限长，对蠕动泵的要求很低，不易造成溶液渗漏等问题。在洗脱过程进行到第5秒时输入1 s空气流作为间隔，而不是等整个洗脱过程完成以后再输入空气流，此方法的优点是：洗脱完全，而且大大降低了被分析物在洗脱过程中的分散，吸收信号值大大增加。如果单纯地把洗脱时间降到5 s，那么洗脱会非常不完全，也就是没有洗脱干净，在管路中还会残存大量的被分析物，残存的被分析物被带入下一个样品分析中，会对整个实验造成很大的误差，所有的实验数据都将不准，失去数据利用价值。所以完全的洗脱是非常必要的，必须保证一定的洗脱时间。由于随着洗脱过程的进行，洗脱下来的被分析物呈逐渐减小的趋势，在以往洗脱方法中，等到整个洗脱过程全部进行完以后，被分析物在洗脱液中的分散已经相当严重了，导致所得到吸收信号值大大减小。在洗脱过程中插入空气流，即在非完全洗脱时插入空气流，降低了被分析物在洗脱过程中的分散，同时保证了洗脱的完全，大大提高了吸收信号峰值。优化了络合剂种类、浓度和酸度，样品富集时间和流速，空气混合吸附时的空气流速和时间，洗脱前第一次通气时间，预洗脱时间，洗脱过程中第二次通气时间等实验参数。在最佳实验条件下，铅在0.005～0.6 mg·L-1浓度范围内呈现良好的线性关系，铅的检出限（3σ）为2.2 μg·L-1。将新方法与直接火焰原子吸收法、传统的FI-KR空气混合吸附预富集普通洗脱法进行了比较，结果显示本方法的浓集系数更高。将该方法应用于海洋生物样中痕量铅的测定，测得鳝鱼、对虾、虾姑、鲟鱼、舌鳎和贻贝标准中的铅含量为0.34~1.92 μg·g-1；加标量为1.0 μg·g-1时，加标回收率为93.5%~96.4%；相对标准偏差为0.52%~2.94%。用FI-KR-FAAS空气混合吸附预富集，二次气体分隔洗脱法测定海洋生物样中的痕量铅，具有富集效果好，准确度高，精密度好，浓集系数高等优点，分析结果令人满意。

FI-KR-FAAS Twice Gas Isolation Elution Method for the Determination of Trace Lead in Marine Biological Samples

In this paper, trace lead in marine biological samples was determined by using flow injection ( FI ) air mixture adsorption preconcentration and twice gas isolation elution method in knotted reactor (KR) coupled with flame atomic absorption spectrometry (FAAS) . Air, complexing reagent and lead solution were mixed on-line during the preconcentration step, and the introduction of air greatly improved the adsorption effects of the lead chelate on the inner walls of KR. By the introduction of air flow before elution and adding part of air flow during elution, through these two parts of the introduction of air flow bubble partition, the dispersion of the lead chelate in KR was greatly reduced, and the peak of the atomic absorption signal was increased, and the enhancement factor (Enhancement factor, EF) was increased. By the combination with the KR of the air mixing sorption preconcentration and twice gas isolation elution method, the KR adsorption effect and elution effect reached a higher level, and compared with high back pressure and short lifetime of the micro column, KR has the characteristics such as acid and alkali resistance, low back pressure and almost unlimited lifetime. What’s more, it has no critical requirement for the peristaltic pump and is not easy to cause leakage of the solution. In the elution process, 1 s air flow was used as a spacer at the fifth second, instead of entering the air flow after the entire elution process was completed. The advantage of this method is not only being eluted completely, but also greatly reducing the dispersion of the analyte during the elution process, and the value of the absorption signal is greatly increased. If the elution time is simply put down to 5 s, then the elution will be very incomplete, the tube being not clean, a large number of analytes still remaining in the tube, and the remnants of the analyte were brought into the analysis of the next sample. All the experimental data will be inaccurate, and the value of data utilization will be lost. So complete elution is necessary and must ensure a certain elution time. As for the elution process, the elution of the analyte decreased gradually, in the past elution method, until the entire process is performed after elution, the analyte in the elution dispersion has been quite serious, which leads to the great reduction of absorption signal value. Operational parameters such as types, concentration and pH of complexing agents, sample preconcentration time and flow rate, flow rate and time of air mixing sorption process, the first ventilation time, pre elution time, the second ventilation time were optimized for the purpose of determining trace lead. Using the optimized conditions, a linear relationship existed between the peak absorbance and the concentrations of lead in the range of 0.005～0.6 mg·L-1 respectively. The method was applied in the determination of trace lead in marine biological samples with a detection limit（3σ） of 2.2 μg·L-1. In this paper, the detection results of FAAS method, traditional FI-KR-FAAS air mixing sorption preconcentration method and normal elution method were compared with this method, and it showed that the new method obtained the highest enhancement factor value. This method was applied to detect the trace lead in biological samples such as eel, pawn, slipper lobster, sturgeon, tonguefish and mussel. The trace lead content in these biological samples were among 0.34~1.92 μg·g-1. When the 1.0 μg·g-1 standard Lead solution was added, the recovery was 93.5%~96.4%, and the relative standard deviation (RSD) was 0.52%~2.94%. The method of FI-KR-FAAS twice gas isolation elution for the determination of trace lead in marine biological samples obtains several merits. It has good preconcentration effect, high precision，high degree of accuracy and high enhancement factor. This method can satisfy the analysis requirement for the marine biological samples.