薄层树脂相预浓集与光度法联用同时测定痕量Fe(Ⅲ)和Mo(Ⅳ)的研究

Determination of trace iron(Ⅲ) and molybdenum(Ⅳ) by ion exchange resin preconcentration and spectrophotometry

在酸性条件下,Fe（Ⅲ）和Mo（Ⅳ）可与邻苯二酚生成有色配阴离子Fe（Ⅲ）-邻苯二酚体系和Mo（Ⅳ）-邻苯二酚体系,该二配阴离子易与Cl-型717#阴离子交换树脂中的Cl-进行等离子对交换缔合,形成三元等离子对缔合体系R＋（阴离子交换树脂）-Fe（Ⅲ）-邻苯二酚体系和R＋-Mo（Ⅳ）-邻苯二酚体系.两种三元缔合体系的最大吸收波长分别为520和402nm,与水相中最大吸收波长相同,对比度△λ=118nm,互不干扰,故而建立了薄层树脂相光度法同时测定Fe（Ⅲ）和Mo（Ⅳ）的新方法.方法灵敏度高,εFe520（Ⅲ）=4.8×10^4L·mol^-1·cm^-1,比水相光度法提高16倍,εMo402（Ⅳ）=1.0×10^5L·mol^-1·cm^-1,比水相光度法提高24倍;精密度理想;选择性强.实测了合成水样和天然水样中Fe（Ⅲ）和Mo（Ⅳ）,加标回收率分别为97%～99%和97%～101%,检出限分别为35和28ng/mL,线性范围分别为0～12和0～9.6μg/mL.与AAS法测定值相比较,结果令人满意.

A new method for the determination of Fe（ Ⅲ ） and Mo （ Ⅳ ） by fin layer resin phase spectrophotometer was developed. The colored complexes anion is formed by Fe（ Ⅲ ） and Mo（ Ⅳ ） with 1,2-benzendiol.These coordination compound can exchange with Cl^- on the surface active sites of model 717 cation exchange resin, and complexes were concentrated on 717 ^# resin（ R ^＋ ） in lower acidic aqueous solution. The system of R^＋ -Fe（ Ⅲ ）-1,2- benzendiol and R ^＋ -Mo（ Ⅳ ）-1,2-benzendiol were prepared. The maximum absorption wavelength of R^＋ -Fe （ Ⅲ ）-1,2-benzendiol and R^＋ -Mo（ Ⅳ ）-1,2-benzendiol is at 520nm and 402nm, respeetively, as same as that in the water phase. The contrast （ △λ ） is is about llSnm. The apparent molar absorptivity （ε520^Fe（Ⅲ） ）4.8 × 10^4L· mol^-1· cm^-1 which is about 16 times higher than in the aqueous phase, and the apparent molar absorptivity （ ε402^Mo（Ⅳ） ） is 1.0 × 10^5L·mol^- 1·cm^-1 ,which is about 24 times higher than that in the aqueous phase. It has an ideal precision （7.0μg Fe （Ⅲ）,n =6,RSD= 1.41%;7.0μg Mo（Ⅳ）, n =6, RSD = 1.67%） .Beer＇s law was obeyed in the range of 0- 12μg/mL and 0 - 9.6μg/mL for Fe（ Ⅲ ） and Mo（ Ⅳ ） respectively. It has a good selectivity for this method, Fe（ Ⅲ ） and Mo（ Ⅳ ） were determined in synthetic water sample and natural water. The recoveries determined by standard addition method for Fe（ Ⅲ ） and Mo（ Ⅳ ） are 97% - 99% and 97% - 101% respectively. The detection limit of Fe（ Ⅲ ） and Mo（ Ⅳ ） are 35ng/mL and 28ng/mL respectively.