Spectrophotometric Determination of Copper and Iron

Reagents and Methods

Ajay Kumar Goswami, Shilpa Agarwal

• Publisher: De Gruyter
• Year: 2021
• eBook ISBN: 9781501515293
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Analytic Chemistry
• Index: Technology & Engineering

The book covers specific and selective reagents for the determination of iron and copper by spectrophotometry. It provides methods for each group or class of reagents, including conditions, wavelength and interferences of other ions in samples. It is a unique guide for researchers in analytical chemistry from pharmaceutical to environmental monitoring laboratories working on iron and copper based products.

Section A

Chapter 1 Analytical reagents having oxygen (O) as donor atom

1.1 Naphthols

1.1.1 1-(2-Imidazolylazo)-2-naphthol-4-sulfonic acid

Pan Fuyou et al. [1] have described spectrophotometric method for the detection of trace Cu in Mg alloys and Fe ores. For this 1-(2-imidazolylazo)-2-naphthol-4-sulfonic acid as a color reagent is used for the detection of Cu(II) in pH 3.0 solutions. The apparent molar absorptivity of the complex is 1.94 × 10⁴ L mol⁻¹ cm⁻¹ at 530 nm. The 1:1 complex has an apparent stability constant of 6.96 × 10⁶ and Beer’s law is obeyed in the range of 0–0.8 µg Cu mL^–1.

1.1.2 1-(2-Pyridylazo)-2-naphthol

Agnihotri Narinder Kumar et al. [2] have reported a photometric method for trace analysis of Cu(II) with 1-(2-pyridylazo)-2-naphthol (PAN) in the presence of a neutral surfactant, Triton X-100 in normal and derivative modes. At 555 nm the molar absorptivity (Ɛ) and Sandell’s sensitivity (S) of PAN–Cu(II) complex is 5.21 × 10⁴ L mol⁻¹ cm⁻¹ and 1.22 ng cm⁻², respectively. The detection limit of Cu(II) is 4.0 ng mL⁻¹ and Beer’s law is obeyed in the range 0.08–4.00 µg mL⁻¹ of the analyte. Cu content of a number of alcoholic beverages, biological and standard alloy samples is reported using this method.

Li Rong et al. [3] have developed β-cyclodextrin polymer adsorbed resin phase spectrophotometry with PAN for determination of copper at the µg level in soybean and human hair. Cobalt, nickel, zinc and manganese, which form colored species with PAN in the resin phase, can be completely masked using a solution composed of phenanthroline (2.78 × 10⁻⁵ mol L^–1) and sodium hexametaphosphate (3.27 × 10⁻³ mol L^–1). The method can be used to determine copper in the presence of cobalt, nickel, zinc and magnesium.

Thakur Manisha et al. [4] have described a simple and sensitive field detection and spectrophotometric method for determination of Cu that is based on the formation of a red-colored species of Cu(II) with 1-[pyridyl-(2)-azo]-naphthol-(2) (PAN), TX-100 and N,N′-diphenylbenzamidine (DPBA) at pH range 7.8–9.4. The red-colored Cu(II)–PAN–(TX-100)–DPBA complex in CHCl₃ shows maximum absorbance at 520 nm with molar absorptivity value of 1.14 × 10⁵ L mol⁻¹ cm⁻¹. The detection limit of the method is 2 ng mL⁻¹ organic phase. The system obeys Beer’s law up to 0.6 µg Cu(II) mL⁻¹ in organic solution. Most of the common metal ions generally found associated with Cu do not interfere. As reported by authors the repeatability of the method is checked by finding relative standard deviation (RSD, n = 10) value for solutions each containing 0.2 µg mL⁻¹ of Cu(II), and the RSD value of the method is 1.5%. The validity of the method is found satisfactory for the determination of Cu in soil and airborne dust particulate samples.

Hejazi Leila et al. [5] have presented a novel, sensitive and simple spectrophotometric method for rapid extraction, pre-concentration and simultaneous determination of trace amounts of Co, Ni and Cu as their PAN complexes using polytetrafluoro ethylene filter as solid phase. The proposed method has been successfully applied by authors to the simultaneous determination of Co, Ni and Cu in tap and pit water samples.

Wang Airong et al. [6] have presented a spectrophotometric method for the determination of Cu⁺² in H₂SO₄ medium anodizing liquor and PAN. Cu forms a stable complex with PAN in acid solution with a solubilizing and sensitizing agent Triton X-100 and gelatine as a protecting agent. The maximum absorption of the complex is 558 nm with apparent molar absorptivity of 2.25 × 10⁴ L mol⁻¹ cm⁻¹. The linear range of the method was 0–3.2 mg mL^–1, and the detection limit is 0.028 mg mL^–1. In this study, no interference was found in the presence of other coexisting ions as reported.

Karim-Nezhad Ghasem et al. [7] have developed multivariate calibration models (principal component regression (PCR) and partial least square (PLS)) for simultaneous determination of Fe(III) and Cu(II) with PAN. In this method AOT has been used as a micellizing agent, due to which spectrum of Fe(III)–PAN complex has been shifted to higher wavelength and the overlapping with Cu–PAN spectrum is decreased. It seems that this anionic surfactant enters the structure of the Fe–PAN complex to cause a shift in the absorption spectrum of it. The method has also been successfully applied to simultaneous determination of Cu and Fe in biological samples.

Karim-Nezhad Ghasem et al. [8] have developed a simple and selective derivative spectrophotometric for detection of copper and iron in human hair and serum samples. For this PAN in bis-2-Et hexyl sulfosuccinate (AOT) micellar solution has been used. In the presence of AOT, the absorption spectrum of Fe(III)–PAN complex shifts to higher wavelengths and the overlapping with Cu–PAN spectrum has been decreased under these conditions. In this condition, in ordinary spectrophotometry, Cu(II) has no interference in the detection of iron, but Fe(III) interfered in the detection of copper. In the first-order derivative mode the spectra of Cu(II)–PAN and Fe(III)–PAN complexes completely resolved together and can selectively detect them, as mentioned. The zero- and first-order derivative spectrophotometric calibration curves were drawn at working wavelengths of 558 and 580 nm for copper and 600 and 630 nm for iron. Molar absorptivity is found 1.82 × 10⁴ and 2.75 × 10⁴ L mol⁻¹ cm⁻¹, respectively, for Cu(II)–PAN and Fe(III)–PAN complexes. In derivative mode, the limits of detection (LOD) for Cu(II) and Fe(III) were 0.038 and 0.025 g mL⁻¹, respectively, as reported.

Afshan Soomro et al. [9] have reported a simple rapid new spectrophotometric method for the determination of copper at trace level using PAN in cationic micellar solution of cetyltrimethyl ammonium bromide (CTAB). By using this micellar system previous solvent extraction method can replaced, which reduces the cost and toxicity, while enhancing the sensitivity, selectivity and the molar absorptivity. At λ_max 559 nm the average molar absorption coefficient and Sandell’s sensitivity is found to be 2.45 × 10⁴ L mol⁻¹ cm⁻¹ and 2.6 ng cm⁻². Beer’s law linear calibration graph is obtained over the concentration range from 0.12 to 5.0 μg mL⁻¹ and the stoichiometric composition of the chelate is 1:2 (Cu:PAN). The developed method is successfully applied for the determination of copper from alloys and real samples as described by authors.

1.1.3 1-Nitroso-2-naphthol

Shar G. A. and Bhanger M. I [10] have reported a method for the spectrophotometric determination of Cu(II)-1-nitroso-2-naphthol complex in aqueous phase in the presence of Tween-40, non-ionic surfactant. The method obeys Beer’s law in the concentration range of 0.25–2.0 mg mL^–1. The detection limit of Cu(II) is 0.25 mg mL^–1. The method has been used for the determination of copper in industrial waste samples, and the results are comparable with those by flame atomic absorption spectroscopy.

Abdollahi H. et al. [11] have presented a spectrophotometric method for the simultaneous determination of Fe, Co and Cu together in many natural samples by using the reagent 1-nitroso-2-naphthol that forms complexes with these metals in the presence of aqueous solution of non-ionic surfactant, Triton-X 100. For individual determinations, molar absorptivity and the limit of detection have been obtained. The total relative standard error for applying the method on synthetic samples is 2.02%. The proposed m...

Table of contents

• Title Page
• Copyright
• Contents
• Preface
• Introduction
• Section A
• Section B
• Index