三元离子缔合物萃取分光光度法测定环境水样中Fe(Ⅱ)和总铁含量

SPECTROPHOTOMETRIC DETERMINATION OF IRON BY ORGANIC SOLVENT EXTRACTION OF THE TERNARY CHELATE OF IONIC ASSOCIATION

以3-(2-吡啶基)-5,6-二苯基-1,2,4-三嗪(PDT)为络合衍生显色试剂,四溴酚酞乙酯钾(TBPE-K)为离子对试剂,Fe(Ⅱ)与PDT、TBPE-K生成三元离子缔合物[Fe(PDT)3][TBPE]2,用1,2-二氯乙烷作为有机萃取试剂,测定有机相中离子缔合物的吸光度。由于三元离子缔合物的生成,最大吸收波长由555 nm红移至610 nm,摩尔吸收系数由2.4×104L.mol-1.cm-1增加至1.9×105L.mol-1.cm-1,使得检测方法的灵敏度得到较大提高,并成功应用于泉水及表层湖水中Fe(II)及总铁含量的测定。

Organic extraction spectrophotometry -a method to determine iron was studied. 3-（2-pyridyl）-5,6-diphenyl-1,2,4-triazinc （PDT） was used as a derivatizing reagent and the potassium salt of tetrabromophenolphthaleinethyl ester （TPBE-K） was used as a ion-pair reagent. It was found that the sensitivity of the method was enhanced with the addition of the ion pair, TPBE-K; because TPBE- and Fe（ Ⅱ ）-PDT can form a ternary chelate of ionic association, the maximum absorbance wavelength was red shift, which would lead to an increase in molar absorption coefficient from 2.4 × 10^4 L ·mol^-1 · cm^-1 to 1.9 ×10^5 L × mol^-1 · cm^-1. The calibration graph was constructed in a concentration range of 0--0. 3mg/L, the linear regression e- quation was A=0. 3582C＋0. 002（r^2 =0. 9974）, and the limit of the detection （LOD） is 0.96 ng/mL（S/N=3）. Organic extraction ion-pair speetrophotometry can be satisfactorily applied to determining the concentrations of Fe（ Ⅱ ） and total iron in the fountain and surface lake water samples.