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

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。

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

Organic extraction spectrophotometry —a method to determine iron was studied.3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine(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 2.4×104 L·mol-1·cm-1 to 1.9×105 L·mol-1·cm-1.The calibration graph was constructed in a concentration range of 0~0.3mg/L,the linear regression equation was A= 0.3582C+0.002(r2=0.9974),and the limit of the detection(LOD) is 0.96 ng/mL(S/N=3).Organic extraction ion-pair spectrophotometry can be satisfactorily applied to determining the concentrations of Fe(Ⅱ) and total iron in the fountain and surface lake water samples.