Copper determination method

Berlin Institute Method. This method is for determination of invert sugar in products containing not more than 10% invert in the presence of sucrose. It is a copper reduction method that utilizes MbUer s solution, which contains sodium carbonate. 

Knight and Allen. This is a copper reduction method for reducing sugars in white sugar up to 0.02%. It utilizes EDTA to determine excess unreacted copper. Tests undertaken in 1994 to extend the range of this method were unsuccesshil. In spite of poor performance in ring tests, it remains an official ICUMSA method. 

Luff Schoorl. This method is for the determination of total reducing sugars in molasses and refined symps after hydrolysis. It is a copper-reducing method that forms the basis of some molasses purchasing contracts. 

Unreacted free sulfur can be determined to ISO 7269 1995 — Rubber — Determination of free sulfur. Three methods for the determination of free sulfur in vulcanized rubber are detailed two versions of the copper spiral method and the sodium sulfite method. The copper spiral methods are also applicable, subject to limitations, to unvulcanised rubber. The technique of DSC can detect non-reacted rubber curatives such as residual peroxides. 

Colorimetry. Copper (Duncombe 1963 Koops and Klomp 1977) or cobalt (Novak 1965) soaps of long-chain fatty acids (>C12) are soluble in chloroform and can be determined quantitatively by colorimetric determination of the extracted metal. Shipe et al. (1980B) have recently modified the original copper soap method to make it simpler, more rapid, and adaptable to automatic equipment. 

Koops, J. and Klomp, H. 1977. Rapid colorimetric determination of free fatty acids (lipol-ysis) in milk by the copper soap method. Neth. Milk Dairy J. 31, 56-74. 

Basic Protocol 1 Titrimetric Determination of Lipase Activity Basic Protocol 2 Colorimetric Assay of Lipase Activity Using the Copper Soap Method... 

Wager, H.G. 1954. An improved copper reduction method for the micro-determination of reducing sugars. Analyst 79 34-41. 

Bynum, D. G., Senyk, G. F., and Barbano, D. M. (1984). Determination of free fatty add content of Cheddar cheese by a copper soap method. J. Dairy Sci. 67,1521-1524. 

Lead, antimony, barium, mercury, and copper determinations were done using the instrumentation, materials, and methods detailed in reference 184. All other elements were analyzed using the standard conditions as detailed in the instrument manual. 

F. A. Honorato, R. S. Honorato, M. F. Pimentel, M. C. U. Araujo, Analytical curve or standard addition method how to elect and design a strategy applied to copper determination in sugarcane spirits using AAS, Analyst, 127 (2002), 1520-1525. 

L. F. Almeida, V. Lacerda Martins, E. C. Silva, P. N. Teles Moreira, M. C. Ugolino Araujo, Implementation of an automatic standard addition method in a flow-batch system application to copper determination in an alcoholic beverage by atomic absorption spectrometry, Anal. Chim. Acta, 486 (2003), 143-148. 

International Organization for Standardization ISO 7952, Fruits, Vegetables and Derived Products - Determination of Copper Content - Method Using Flame Atomic Absorption Spectrometry (1994)... 

Direct titrimetric method is a classic method for DE determination (National Research Council, 1972). In this method, pectin is first washed by acidic alcohol to convert the free carboxyl groups to the protonated form and is then washed with alcohol and dried. The washed sample is then dissolved in water and titrated with standard base and acid. The uronic content and DE are calculated from the neutralization and saponification equivalents of the pectic carboxyl groups. The existence of acetyl groups in some pectin samples leads to an overestimate of DE in the titration method. In this case, the copper binding method is an alternative approach (Keijbets and Pilnik, 1974). In the copper binding method, the amounts of copper ions that bind to the pectin molecules before and after saponification are measured by the complexometry, the ratio of which gives the DE. 

This can be performed successfully both on metal electrodes (e.g. copper) or with graphite electrodes which have been previously impregnated with a solution of Apiezon (e.g. in benzene). In the latter case carriers such as CsCl may be useful so as to increase the line to background ratios as a result of their influence on the current voltage characteristics [354]. The copper arc method has found use in the determination of the rare earths in solutions, which was historically important in radiochemistry related topics [355-357]. 

Unless otherwise indicated, metal content is given in micrograms per gram of protein. All zinc determinations by the dithizone method in duplicate, and in quadruplicate for the crystalline enzyme preparations. Copper determined by the sodium dithiocarbamate method. Spectrographic analyses were done in duplicate, and separately on two different instruments. 

The main interfering metals in the copper determination are Fe, Bi, Mn, Ni, Co, Cr, Mo and U, which form coloured complexes. The selectivity of the method is considerably enhanced by the use of EDTA as a masking agent. In a tartrate or citrate medium at pH 8-9, Fe, Mn, Ni and Co are masked by EDTA, as are Cd, Pb, Zn, and In, which form colourless complexes with DDTC. Of the metals forming coloured compounds with DDTC, only Bi, Tl(III), and Cu are not masked. Thallium, when reduced to T1(I), does not interfere. Bismuth can be stripped from the organic extract, containing copper and bismuth diethyidithiocarbamates, with 5 M HCl. Copper diethyidithiocarbamate is decomposed by cyanide, whereas the bismuth complex remains unaffected. 

The most time-honored and certainly dependable method for serum, urine, and tissue copper determination is that described by Eden and Green in 1940 (E3). Wet ashing with a combination of sulfuric, perchloric, and nitric acids is followed by the deionization of iron with citrate and/or pyrophosphate in strongly alkaline medium. Diethyldithiocarbamate is the color reagent and the complex is extracted into amyl alcohol. Provided blanks can be kept low, which can be achieved only by applying extreme care to avoid contamination of the many reagents, copper can be determined reliably in 0.5-1.0 ml of serum. While this method undoubtedly represents a great improvement over previous methods (M4, T5), it is somewhat cumbersome nevertheless it has proved its worth in many hands and has been the basis of a number of modifications and applications. 

The diethyldithiocarbamate copper complex is unstable in acid medium and is light-sensitive. Dibenzyldithiocarbamate (avaUable as zinc salt) lacks these disadvantages moreover, it is more sensitive (Table 1) and more specific (M13, S3). Maytum et al. (M17) and most recently Giorgio et al. (G5) have described methods for urinary copper determination with this reagent. The latter method does not require preliminary ashing. The only disadvantage of these methods is the use of carbon tetrachloride, which is potentially toxic. 

At present activation analysis is the most sensitive method for copper determination. However, it requires the analyst to have access to a nearby source of thermal neutron radiation, as well as a special laboratory and personnel for radiochemical work. 

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