Salicylic aldehyde derivative as a new reagent for spectrophotometric determination of copper (II)

A simple, rapid spectrophotometric method for determination of Cu (II) ions is described using a new analytical reagent — [(2-hydroxybenzaldehyde)-3-isatin]-bishydrazone (R), which is a product obtained by condensation of salicylic aldehyde with isatin hydrazone. NMR spectroscopy and X-ray diffraction analysis were used to confirm the composition and structure of the synthesized reagent. Complexation of Cu (II) with R in the presence of diantipyrylphenylmethane (DAPM) and 8-oxyquinoline (Ox) was also studied spectrophotometrically. Optimum conditions for complexation (λ_opt, pH_opt) of homogeneous (Cu (II)-R) and mixed-ligand (Cu (II)-R-Ox and Cu (II)-R-DAPM) complexes were determined. The molar absorption coefficients of the complexes and the region of subordination to Beer’s law were established. The stoichiometric ratio of the components in the complexes was confirmed by the methods of isomolar series, continuous changes (Job’s method), and equilibrium shift. The effect of some foreign ions and masking substances on the formation of Cu (II) complexes was studied. The proposed method was used to determine trace amounts of copper in various vegetable samples (pepper, onion and cabbage).

1. Locatelli M., Farina C. Role of copper in central nervous system physiology and pathology / Neural Regener. Res. 2025. Vol. 20. No. 4. P. 1058 – 1068. DOI: 10.4103/nrr.nrr-d-24-00110

2. Brewer G. J., Yuzbasiyan-Gurkan V. Wilson disease / Medicine (Baltimore). Vol. 71. No. 3. P. 139 – 164. DOI: 10.1097/00005792-199205000-00004

3. Bagherian G., Chamjangali M. A., Evari H. S., Ashrafi M. Determination of copper (II) by flame atomic absorption spectrometry after its preconcentration by a highly selective and environmentally friendly dispersive liquid-liquid microextraction technique / J. Anal. Sci. Technol. 2019. Vol. 10.3. DOI: 10.1186/s40543-019-0164-6

4. Özzeybek G., Erarpat S., Chormey D. S., et al. Sensitive determination of copper in water samples using dispersive liquid-liquid microextraction-slotted quartz tube-flame atomic absorption spectrometry / Microchem. J. 2017. Vol. 132. P. 406 – 410. DOI: 10.1016/j.microc.2017.02.031

5. Arain M. S., Kazi T. G., Afridi H. I., et al. Ultrasonic energy enhanced the efficiency of advance extraction methodology for enrichment of trace level of copper in serum samples of patients having neurological disorders / Ultrason. Sonochem. 2017. Vol. 37. P. 23 – 28. DOI: 10.1016/j.ultsonch.2016.12.020

6. Karimi M. A., Mohammadi S. Z., Mehrjardi A. H., et al. A new sorbent based on MWCNTs modification for separation/preconcentration of trace amounts of Cd (II), Cr (III), Cu (II), Ni (II), and Pb (II) and their determination by flame atomic absorption spectrometry / J. Anal. Sci. Technol. 2015. Vol. 6. 25. DOI: 10.1186/s40543-015-0065-2

7. Dos Santos L., dos Santos Q. O., Moreno I., et al. Multivariate optimization of a simultaneous cloud point extraction procedure of Cd, Cu and Ni from sediments samples and determination by ICP-OES / J. Braz. Chem. Soc. 2016. Vol. 27. No. 4. P. 745 – 752. DOI: 10.5935/0103-5053.20150325

8. Carvalho R. N., Brito G. B., Korn M. G., et al. Multi-element determination of copper, iron, nickel, manganese, lead and zinc in environmental water samples by ICP OES after solid phase extraction with a C18 cartridge loaded with 1-(2-pyridylazo)-2-naphthol / Anal. Methods. 2015. Vol. 7. No. 20. P. 8714 – 8719. DOI: 10.1039/c5ay01929j

9. Pourmand N., Sanagi M. M., Naim A. A., et al. Dispersive micro-solid phase extraction method using newly prepared poly(methyl methacrylate) grafted agarose combined with ICP-MS for simultaneous determination of Cd2+, Ni2+, Cu2+ and Zn2+ in vegetable and natural water samples / Anal. Meth. 2015. Vol. 7. No. 7. P. 3215 – 3223. DOI: 10.1039/c4ay02889a

10. Bithi N., Ricks D., Walker B. Method validation of an inductively coupled plasma mass spectrometry (ICP-MS) assay for the analysis of magnesium, copper and zinc in red blood cells / J. Mass Spectrom. Adv. Clin. Lab. 2024. Vol. 34. P. 21 – 27.

11. Pratskova S. E., Khudaiberdina D. R. Spectrophotometric determination of copper (II) in soil in the form of a pyrogallol red complex in the presence of surfactants / Vestn. Mosk. Univ. Ser. 2. Khimiya. 2024. Vol. 65. No. 1. P. 67 – 72 [in Russian].

12. Kumar A., Mohanb B., Modi K., et al. A highly selective ratiometric and colorimetric detection of Ni2+ and Cu2+ ions using Schiff base ligand / J. Mol. Struct. 2022. Vol. 1268. 133609. DOI: 10.1016/j.molstruc.2022.133609

13. Nayif A. A., Al-Da’amy M. A., Kadhim S. H. Spectrophotometric determination of Cu (II) using (DMIPNI) as a new reagent derived from 4,5-diphenyl imidazole / Int. J. Drug Delivery Technol. 2022. Vol. 12. No. 2. P. 522 – 527.

14. Hatam R. S., Shaheed I. M., Hussain A. F. Spectrophotometric determination of copper (II) using 2,2-[O-tolidine-4,4-bisazo]bis[4,5-diphenylimidazole] (MBBAI) / Baghdad Sci. J. 2020. Vol. 17. No. 1 (Suppl.). P. 287 – 294. DOI: 10.21123/bsj.2020.17.1(suppl.).0287

15. Javadzade T. A., Mammadov P. R., Sucayev A. R., Mammadova R. E. New simple method for the determination of trace level copper (II) using 1-[2-(allylamino)-1-methylethyl]thiourea in presence of hydrofob amines by molecular absorption spectral method in the UV and visible region / Az. J. Chem. News. 2022. Vol. 4. No. 2. P. 40 – 50. DOI: 10.32010/ajcn04022022-40

16. Mamedova C. A., Gadzhieva S. R., Alieva F. S., Chyragov F. M. Structure of 2-(((1-(3-bromophenyl) ethylidene)hydrazono)methyl)phenol and its application in the spectrophotometric determination of iron(III) / J. Anal. Chem. 2024. Vol. 79. No. 8. P. 1020 – 1026. DOI: 10.1134/s1061934824700400

17. Korostelev P. P. Preparation of solutions for chemical and analytical work. — Moscow: Nauka, 1964. — 261 p. [in Russian].

18. Bulatov M. I., Kalinkin I. P. A practical guide to photometric and spectrophotometric method of analysis. — Leningrad: Khimiya, 1972. — 407 p. [in Russian].

19. Raafid E., Al-Da’amy M. A., Kadhim S. H. Spectrophotometric determination of Cu (II) in analytical sample using a new chromogenic reagent (HPEDN) / Indonesian J. Chem. 2020. Vol. 20. No. 5. P. 1080 – 1091. DOI: 10.22146/ijc.47894

20. Turabov N. T., Khusanov B. M., Todjiev Zh. N., et al. A new method for spectrophotometric determination of copper (II) ions / Universum Chem. Biol. 2023. No. 6 (108) [in Russian]. https://7universum.com/ru/nature/archive/item/15620 (accessed 29.01.2026).