| Chelating agents,containing at least two electron-donating groups in structure,coordinate certain metal ions to form stable chelates that can reduce metal ion activities,and are widely used in water softening,oxidative bleaching,corrosion and scale inhibition,soil remediation and other related research and production applications.Especially,as an important auxiliary in textile dyeing and finishing,it can prevent sedimentation,eliminate equipment scaling,prevent fabric from excessive oxidation,and improve the quality of textile processing effectively.There are many varieties of chelating agents,with different chelating capabilities affected by pH values for different metal ions.Different dyeing and finishing processes require different pH values,and the chelating capability at certain pH value can be referred to information as data.At present,the determination of chelating capability to calcium for textile auxiliaries is mainly based on GB/T 21884,and that is needed to be performed at pH=10.Other methods such as precipitation titration,gel filtration chromatography also need to be done under certain pH conditions,which cannot meet the actual test requirements of the chelating capability of chelating agents under different pH conditions.It is necessary to develop a new method that can be applied to determine the chelating capability at different pH,and provide a scientific basis for the correct use,in-depth development and quality monitoring of chelating agents.Amino trimethylenephosphonic acid(ATMP)was chosen as the chelating agent,and calcium chloride or copper chloride as the source of calcium ion or copper ion in this paper.A new method determing the chelating capability to calcium or copper of ATMP was developed at different pH,including sample pretreatment and influence factors.Separation of ATMP(calcium,copper)chelate,determination of calcium or copper content in chelate were focused,the repeatability and accuracy of new method were investigated,and this method was successfully applyied to determining calcium or copper chelating capability of ATMP at different pH values.After standardization,the new method was further popularized and applied to textile chelating agents.The ATMP(calcium,copper)chelate was characterized by UV-vis,FTIR and ESI TOF-HRMS,and the mechanism of chelation reaction was discussed.The results show that ATMP coordinate(calcium,copper)chloride quickly,and four times volume of the chelating reaction solution of ethanol is used to isolate ATMP(calcium,copper)chelate.The calcium ion content in ATMP calcium chelate is analyzed by complex indicator-EDTA titration method,and the recovery of calcium ion ranges from 98.25%to 101.50%.The chelated copper content in ATMP copper chelate is determined by flame atomic absorption spectrophotometry,and the recovery of copper ion ranges from 94.73%to 100.00%.pH=5 and pH=12 are selected to examine the repeatability of the ATMP(calcium,copper)chelating capability determination method.The results show that the RSD at pH=5 are 2.52%?4.98%(calcium)and 7.29%?8.92%(copper),RSD at pH=12 are 2.83%?7.14%(calcium)and 1.60%?3.33%(copper).Using the new method,the chelating capability of ATMP to calcium at pH=10 is 173.6 mg/g with a relative deviation of 3.76%compared by using the national standard method.It is speculated that ATMP coordinates calcium(copper)ion through the central nitrogen atom and the oxygen atom on the phosphate hydroxyl group with an amount ratio of 1:1,in which the coordination number of calcium ions is 3,and the coordination number of copper ions is 4. |
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