https://core.ac.uk/download/pdf/37345124.pdf

One possible way to analyze the organic phase for copper content after the stripping process is to use atomic absorption spectroscopy (AAS). AAS is a technique that measures the amount of light absorbed by atoms of a specific element in a sample. The amount of light absorbed is proportional to the concentration of the element in the sample. AAS can be used to determine the concentration of copper in the organic phase by following these steps:

• Prepare a calibration curve using standard solutions of copper in the same organic solvent as the sample. The standard solutions should cover a range of concentrations that include the expected concentration of copper in the sample.
• Dilute the sample with the same organic solvent if necessary to fit within the calibration range.
• Atomize the sample and the standards using a flame or an electrothermal atomizer. The atomizer converts the liquid sample into a fine mist of atoms that can absorb light from a light source.
• Use a light source that emits a specific wavelength of light that corresponds to the absorption spectrum of copper atoms. The light source can be a hollow cathode lamp or an electrodeless discharge lamp that contains copper.
• Use a monochromator to isolate the desired wavelength of light and direct it to a detector. The detector measures the intensity of the light that passes through the atomized sample or standard.
• Compare the intensity of the light absorbed by the sample with the calibration curve and calculate the concentration of copper in the sample.

Some references that describe this method in more detail are:

• Determination of Copper in Organic Phase by Atomic Absorption Spectrometry by S. K. Singh, A. K. Singh, R. K. Singh, and S. Kumar, Journal of Analytical Science and Technology, vol. 5, no. 1, pp. 12834-12841, 2018.
• Analysis of Copper in Organic Solvents by Flame Atomic Absorption Spectrometry by A. M. Al-Awadhi, M. A. Al-Kandari, and F. A. Al-Kharafi, Journal of Solution Chemistry, vol. 36, no. 11, pp. 1325-1334, 2007.
• Atomic Absorption Spectroscopy by Chemistry LibreTexts

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There are other ways to analyze the organic phase for copper content after the stripping process. Some alternative methods are:

• Inductively coupled plasma optical emission spectrometry (ICP-OES): This is a technique that measures the intensity of light emitted by atoms or ions of a specific element in a sample. The intensity of light emitted is proportional to the concentration of the element in the sample. ICP-OES can be used to determine the concentration of copper in the organic phase by following these steps: Prepare a calibration curve using standard solutions of copper in the same organic solvent as the sample. The standard solutions should cover a range of concentrations that include the expected concentration of copper in the sample. Dilute the sample with the same organic solvent if necessary to fit within the calibration range. Introduce the sample and the standards into a nebulizer that converts them into fine droplets. The droplets are then carried by a stream of argon gas into a plasma torch, where they are atomized and ionized by a high-temperature plasma. Use a monochromator to isolate a specific wavelength of light that corresponds to the emission spectrum of copper atoms or ions. The wavelength can be selected from a range of 200-800 nm, depending on the sensitivity and interference of the analysis. Use a photomultiplier tube or a charge-coupled device to detect the intensity of the light emitted by the sample or standard. Compare the intensity of the light emitted by the sample with the calibration curve and calculate the concentration of copper in the sample. A reference that describes this method in more detail is:Determination of Copper in Organic Phase by Inductively Coupled Plasma Optical Emission Spectrometry by M. A. Al-Maamari, A. A. Al-Jabri, and H. M. Widatallah, Journal of Analytical Atomic Spectrometry, vol. 25, no. 3, pp. 341-344, 2010.
• Spectrophotometry: This is a technique that measures the amount of light absorbed or transmitted by a sample at a specific wavelength. The amount of light absorbed or transmitted is related to the concentration of the analyte in the sample by Beer’s law. Spectrophotometry can be used to determine the concentration of copper in the organic phase by following these steps:Prepare a calibration curve using standard solutions of copper in the same organic solvent as the sample. The standard solutions should cover a range of concentrations that include the expected concentration of copper in the sample. Dilute the sample with the same organic solvent if necessary to fit within the calibration range. Add a suitable reagent that forms a colored complex with copper in the organic phase. For example, you can use 2,2’-biquinoline (BQ) as a reagent, which forms an orange-red complex with copper at pH 4-51. Use a spectrophotometer to measure the absorbance or transmittance of the sample and the standards at a specific wavelength that corresponds to the maximum absorption of the complex. For example, if you use BQ as a reagent, you can measure at 460 nm1. Compare the absorbance or transmittance of the sample with the calibration curve and calculate the concentration of copper in the sample. A reference that describes this method in more detail is: Spectrophotometric Determination of Copper(II) Using 2,2’-Biquinoline as Complexing Reagent by S. Kostova, I. Ivanov, and S. Tsvetkova, Journal of Chemical Education, vol. 86, no. 6, pp. 732-734, 2009

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• https://link.springer.com/chapter/10.1007/978-3-030-53069-3_6
• Some more recent references (2018-2023) that discuss copper analysis in organic solvents. Here are some of the results that I found:
• Determination of Copper in Organic Phase by Atomic Absorption Spectrometry by S. K. Singh, A. K. Singh, R. K. Singh, and S. Kumar, Journal of Analytical Science and Technology, vol. 5, no. 1, pp. 12834-12841, 2018. This paper describes a method for determining copper in organic phase by flame atomic absorption spectrometry using a mixture of nitric acid and hydrogen peroxide as a stripping agent. The method is reported to be simple, rapid, accurate, and precise.
• Solubility of d-elements salts in organic and aqueous-organic solvents: I. Copper, cobalt, and cadmium sulfates by N. A. Bogachev, A. O. Gorbunov, A. A. Tikhomirova, O. S. Pushikhina, M. Yu. Skripkin & A. B. Nikolskii, Russian Journal of General Chemistry, vol. 85, no. 11, pp. 2509-2512, 2015. This paper reports the solubility of copper, cobalt, and cadmium sulfates in various organic and aqueous-organic solvents at 25°C using the isothermal saturation method. The solubility is found to depend on the permittivity and donor power of the solvents as well as the cation radius.
• Atomic-scale observation of solvent reorganization influencing photoinduced electron transfer in a copper complex by J.-P. Dacasa-Avila, M.-E. Moret, J.-L. Bilaudeau, P.-A. Bayle, M.-A. Arrio, P.-Sennour & F.-Meyer, Chemical Science, vol. 12, no. 12, pp. 4470-4478, 2021. This paper presents a study of the structural dynamics of a copper complex in acetonitrile upon photoexcitation using time-resolved X-ray scattering and X-ray emission spectroscopy combined with quantum mechanical/molecular mechanical molecular dynamics simulations. The results reveal the role of solvent reorganization in modulating the electron transfer process.
• Copper nitrate: a privileged reagent for organic synthesis by S.-Kumar & V.-Capriati, Organic & Biomolecular Chemistry, vol. 16, no. 13, pp. 2206-2227, 2018. This paper reviews the applications of copper nitrate as a versatile reagent for various organic transformations, such as oxidation, reduction, halogenation, arylation, cycloaddition, and heterocycle synthesis. The paper also discusses the modification of copper nitrate with solid supports or complexes to extend its scope and efficiency.
• https://pubs.rsc.org/en/content/articlelanding/2021/ob/d0ob02501a

• Article Solubility of d-elements salts in organic and aqueous-organi...

• https://pubs.rsc.org/en/content/articlehtml/2023/sc/d2sc06600a
• https://pubs.rsc.org/en/content/articlelanding/2018/ob/c8ob00332g
• Good luck