Rapid, synergistic extractive spectrophotometric determination of copper(II) by using sensitive chromogenic reagent N″,N″′-bis[(E)-(4-fluorophenyl) methylidene]thiocarbonohydrazide

•The sensitivity and absorptivity is greater than our previous 2′,4′-dinitro APTPT chromogenic reagent [59].•Dilute pyridine is used as a synergent.•The proposed method is very simple, selective and rapid.•The developed analytical method is proved to reliable for analysis of real samples, which is confirmed by AAS.

A rapid and simple spectrophotometric method was developed for the determination of copper(II) by using newly synthesized chromogenic reagent, N″,N″′-bis[(E)-(4-fluorophenyl)methylidene]thiocarbonohydrazide [bis(4-fluoroPM)TCH]. The reagent is highly sensitive and it forms yellow colored ternary complex with copper(II) in presence pyridine having composition 1:1:2 (M:L:Py) in the acidic pH range. Absorption of colored complex in amyl acetate is measured with reagent as a blank at λmax 375 nm. The synergistic effect is observed due to pyridine forming adduct with reagent in the organic phase. Beer’s law was obeyed in the concentration range from 2.0 to 14 μg mL−1 for copper(II)–[bis(4-fluoroPM)TCH]–Py complex. Molar absorptivity and Sandell’s sensitivity values for Cu(II)–bis(4-fluoroPM)TCH]–Py complex are 0.42545 × 105 and 0.0014 μg/cm2, respectively. The selectivity of the developed method was checked in the presence of various foreign ions. The developed method showed relative standard deviation (R.S.D.) of 0.13% for n = 10. The composition of Cu(II)–[bis(4-fluoroPM)TCH]–Py complex was determined by known methods such as Job’s method of continuous variation, mole ratio method and slope ratio method. It is found that the ternary complex is stable for more than 24 h. Various factors influencing on the degree of complexation, such as, effect of pH, reagent concentration, synergent concentration, solvent etc. were studied. The accuracy and reliability of method was verified by AAS. This method is found to be simple, rapid and reproducible.

Graphical abstract(A) Absorption spectra of [bis(4-fluoroPM)TCH] vs. amyl acetate blank: (B) absorption spectra of Cu(II)–[bis(4-fluoroPM)TCH]–pyridine complex vs. [bis(4-fluoroPM)TCH] blank Cu(II) = 10 μg mL−1; [bis(4-fluoroPM)TCH] = 5.0 mL of 0.01 mol L−1; pyridine = 5.0 mL of 0.5 mol L−1; pH = 2.5; shaking time = 5 min.Figure optionsDownload full-size imageDownload as PowerPoint slide