Third-derivative Spectrophotometry Research Articles

First- and Third-Derivative Spectrophotometry for Simultaneous Determination of Dexamethasone and Cytarabine in Pharmaceutical Formulations and Biological Fluids

The derivative spectrophotometric method was established for simultaneous determination of dexamethasone and cytarabine (cytosine arabinoside). Measurements were made in the zero-crossing wavelengths at 268.0 nm (first derivative) and 264.0 nm (third derivative) for determining dexamethasone and cytarabine, respectively. The calibration graphs were linear in the concentration ranges 0.10 to 10 μg/mL of dexamethasone and 0.25 to 50.0 μg/mL of cytarabine. The limits of detection 0.08 and 0.10 μg/mL and relative standard deviations 3.0 and 1.0% were obtained for dexamethasone and cytarabine, respectively. The possible interfering effect of other substances was also studied to investigate selectivity of the developed method. The proposed method was applied satisfactorily for the simultaneous determination of both drugs in the pharmaceutical formulation and biological fluid samples.

Simple and sensitive method for the determination of trace amounts of thorium using a benzoquinone derivative

A novel simple, sensitive, rapid, direct, and spectrophotometry-based procedure was investigated to determine Th(IV) at trace amounts. The new method is based on Th(IV) chelation with 3,6-dichloro-2,5-dihydroxy-l,4-benzoquinone (DDBQ). The reagent reacts with Th(IV) in 0.1 M HCl to form an orange 1:2 complex. The stability constant value is 6.62 × 104 for the Th(IV) complex. The Th(IV)-DDBQ obtained shows one peak with a maximum at about 346 nm. The chelate forms immediately and the absorbance remains stable for over 24 h. Beer’s law was obeyed in the concentration range 0–10 µg mL−1. The molar absorptivity and Sandell’s sensitivity were 4.4 × 104 L mol−1 cm−1 and 0.0053 μg cm−2, respectively. Different analytical parameters were tested in detail. Interfering ion (cations and anions) effects were tested. Methods for Th(IV) determination by second and third-derivative spectrophotometry were also introduced at about 344 and 341 nm, respectively. These two derivative orders offer the feature of sensitivity without the necessity for solvent extraction, heating, or pre-concentration steps. Finally, the methods were successfully utilized for Th(IV) determination in monazite, environmental water, and wastewater samples.

Determination of Er3+ Ion at Nano Level Based on Newly Synthesized Schiff Base As a Neutral Carrier By Coated Graphite Electrode

The rare earth elements (REEs) are mainly of two series Lanthanides and Actinides. Despite of their name REEs are not so rare in environment, they widely distributed in throughout the earth’s crust in low concentration. The REEs have significant industrial application as competitive to transition elements and wide application have been found in bioinorganic, inorganic chemistry. Erbium is mainly used as laser beams to resurfacing skin, transdermal drug delivery, transdermal peptide delivery, skin vaccination and enhances the RNA delivery. It is estimated that the erbium concentration of the earth’s crust reaches 24 ppm. The commercial sources of erbium are monazite and bastnasite. Even though the conclusion of the investigators, the rare earth elements are considered as low acute toxicity rating, these causes several problems to living species. Due to their enhanced discharge, toxic properties and other adverse effects, determination of erbium is essential in a variety of environmental samples.A number of instrumental techniques such as second order derivative spectrophotometry, third-derivative spectrophotometry, X-ray fluorescence, graphite furnace atomic spectrometry techniques, inductively coupled plasma mass spectrometry, rutherford backscattering spectrometry and spectrophotometric determination are available for its estimation. These methods provide accurate determination of erbium content but involve large infrastructure backup and support of expertise. We found ion-selective electrode to overcome these problems. Ion-selective electrodes are electrochemical ideal sensors in many respects for use in the analysis of industrial and environmental samples.Plasticized membranes using N-(-3-((thiazol-2-ylimino)methyl)benzylidene)thiazol-2-amine (S1) and 5-((-3-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)-benzylidene)amino)-1,3,4-thiadiazole-2-thiol (S2) have been prepared and explored as Er3+ selective electrodes. Effect of various plasticizers viz. dibutylphthalate (DBP), tri-n-butylphosphate (TBP), dioctylphthalate (DOP), acetophenone (AP), 1-chloronapthalene (1-CN), o-nitrophenyloctylether (o-NPOE), and anion excluders viz. sodium tetraphenylborate (NaTPB) and potassium tetrakis-p-(chlorophenyl)borate (KTpClPB) was studied in detail and improved performance was observed. Optimum performance was observed for the membrane electrode having a composition of S2: PVC: o-NPOE: KTpClPB in the ratio of 4: 38: 55: 3 (w/w, mg). The performance of the polymeric membrane electrode (PME) based on S2 was compared with coated graphite electrode (CGE). The electrodes exhibit Nernstian slope for Er (III) ions with limit of detection of 5.4 × 10-8 mol L−1 for PME and 6.1 × 10-9 mol L−1 for CGE. The response time for PME and CGE was found to be 12 s and 9 s respectively. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0-9.0 for PME and 3.0-9.5 for CGE. The CGE could be used for a period of 7 weeks. The practical utility of the CGE has been demonstrated by its usage as an indicator electrode in potentiometric titration of EDTA with Er (III) solution and determination of F- ion in mouthwash solution. The proposed electrode was also successfully applied to the determination of Er3+in water, binary mixtures. Table 1. Response characteristics of Er3+ ion selective electrodes based on PME and CGE. PropertiesElectrode ResponsePMECGEWorking concentration range (mol L-1)7.9 × 10-8 - 1.0 × 10-1 9.4 × 10-9 - 1.0 × 10-1 Detection limit (mol L-1)5.4 × 10-8 6.1 × 10-9 Slope (mV decade-1 of activity)19.8 ± 0.419.6 ± 0.3Response time (s)129pH range4.0-9.03.0-9.5Fig. 1. Structure of ligands N-(-3-((thiazol-2-ylimino)methyl)benzylidene)thiazol-2-amine (S1) and 5-((-3-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)-benzylidene)amino)-1,3,4-thiadiazole-2-thiol (S2)

Validated Spectrophotometric Methods for Simultaneous Determination of Food Colorants and Sweeteners

Two simple spectrophotometric methods have been proposed for simultaneous determination of two colorants (Indigotin and Brilliant Blue) and two sweeteners (Acesulfame‐K and Aspartame) in synthetic mixtures and chewing gums without any prior separation or purification. The first method, derivative spectrophotometry (ZCDS), is based on recording the first derivative curves (for Indigotin, Brillant Blue, and Acesulfame‐K) and third‐derivative curve (for Aspartame) and determining each component using the zero‐crossing technique. The other method, ratio derivative spectrophotometry (RDS), depends on application ratio spectra of first‐ and third‐derivative spectrophotometry to resolve the interference due to spectral overlapping. Both colorants and sweeteners showed good linearity, with regression coefficients of 0.9992–0.9999. The LOD and LOQ values ranged from 0.05 to 0.33 μgmL−1 and from 0.06 to 0.47 μgmL−1, respectively. The intraday and interday precision tests produced good RSD% values (<0.81%); recoveries ranged from 99.78% to 100.67% for all two methods. The accuracy and precision of the methods have been determined, and the methods have been validated by analyzing synthetic mixtures containing colorants and sweeteners. Two methods were applied for the above combination, and satisfactory results were obtained. The results obtained by applying the ZCDS method were statistically compared with those obtained by the RDS method.

Modified analcime loaded with zincon as a useful material for the separation and preconcentration of trace palladium and its determination by third-derivative spectrophotometry

This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5 to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO) and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996. Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d 3 A/dλ3 (peak-to-peak signal between λ2 = 625 and λ1 = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d 3 A/dλ3) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in various synthetic and water samples.

Stability-Indicating Methods for the Determination of Disopyramide Phosphate

Four methods were developed for the determination of intact disopyramide phosphate in the presence of its degradation product. In the first and second methods, third-derivative spectrophotometry and first derivative of the ratio spectra were used. For the third-derivative spectrophotometric method, the peak amplitude was measured at 272 nm, while for the derivative ratio spectrophotometric method, disopyramide phosphate was determined by measuring the peak amplitude at 248 and 273 nm. Both methods were used for the determination of disopyramide phosphate in the concentration range 12.5-87.5 microg/mL, with corresponding mean recovery 100.8 +/- 0.7% for the first method and 99.9 +/- 0.7% and 99.6 +/- 0.7% for the second method at 248 and 273 nm, respectively. In the third method, an ion selective electrode (ISE) was fabricated using phosphotungstic acid as an anionic exchanger, PVC as the polymer matrix, and dibutylsebacate as a plasticizer. The ISE was used for the determination of disopyramide phosphate in pure powder form in the concentration range 10(-2)-10(-5) M. The slope was found to be 58.5 (mV/decade), and the average recovery was 99.9 +/- 1.6%. The fourth method depended on the quantitative densitometric determination of the drug in concentration range of 0.25-2.5 microg/spot using silica gel 60 F245 plates and ethyl acetate-chloroform-ammonium hydroxide (85 + 10 + 5, v/v/v) as the mobile phase, with corresponding mean accuracy of 100.3 +/- 1.1%. The 4 proposed methods were found to be specific for disopyramide phosphate in presence of up to 80% of its degradation product for the spectrophotometric methods, 90% of its degradation for the densitometric method, and 40% for the ISE method. The 4 proposed procedures were successfully applied for the determination of disopyramide phosphate in Norpace capsules. Statistical comparison between the results obtained by these methods and the official method of the drug was done, and no significant differences were found.

Determination of binary mixtures of analgesic and spasmolytic drugs in pure and dosage forms by derivative spectrophotometry

Binary mixtures of dipyrone and pitophenone hydrochloride are assayed by zero-crossing second- and third-derivative spectrophotometry and by ratio-spectra first- and second-derivative spectrophotometry. In the first method, calibration plots are linear at 266.5 and 302.5 nm (dipyrone, second derivative), and 257 and 286 nm (pitophenone second derivative) and 242 and 278.3 nm (dipyrone third derivative), and 228.5 and 300 nm (pitophenone, third-derivative). By the second method, lines of regression are linear at 235 and 262 nm (dipyrone, first derivative), and 229.5 and 288.5 nm (pitophenone, first-derivative), and 249.7 and 268 nm (dipyrone, second derivative), and 280.5 and 300 nm (pitophenone, second-derivative). In all methods calibration curves follow the Beer's law up to 40 μg/ml of each drug. LOD and LOQ values were calculated. The developed derivative spectrophotometric methods were applied to laboratory mixtures and to vials for these drugs. The procedures are simple, rapid, and did not require any preliminary separation or treatment of the samples.

Stability-Indicating Spectrophotometric and Densitometric Methods for Determination of Aceclofenac

ABSTRACTThree methods were developed for the determination of aceclofenac in the presence of its degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D3) is used. The D3 absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4–24 µg mL−1 with mean percentage accuracy of 100.05±0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42±0.94. The second method depends on ratio-spectra first-derivative (RSD1) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4–32 µg mL−1 for both aceclofenac and diclofenac with mean percentage accuracy of 99.81±0.84 and 100.19±0.72 for pure drugs and 100.17±0.94 and 99.73±0.74 for laboratory-prepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283 nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2–10 and 1–9 µg spot−1 with mean percentage accuracy of 100.20±1.03 and 100.14±0.98 for pure drugs and 99.77±0.74 and 100.07±0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug.The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed statistically with those obtained by the reported method.

Evaluation of lipid ultraviolet absorption as a parameter to measure lipid oxidation in dark chicken meat.

The application of lipid UV absorption (235, 269, and 280 nm) to follow up lipid oxidation in dark chicken meat has been evaluated using raw and cooked samples with different alpha-tocopherol contents (modulated by dietary supplementation). To this purpose, when absorption was measured at 235 nm, second-derivative spectrophotometry did not show any significant advantage over nonderivative spectrophotometry. For absorption at 269 and 280 nm, nonderivative spectrophotometry more sensitively monitored lipid oxidation than second- and third-derivative spectrophotometry. In addition, only direct measurements at 235 and 269 nm and second-derivative measurements at 235 nm showed a limited usefulness to follow up lipid oxidation in our samples. However, these UV absorption parameters were much less effective than lipid hydroperoxide values measured through a ferrous oxidation-xylenol orange method and 2-thiobarbituric acid values determined by a third-derivative spectrophotometric method with acid aqueous extraction.

Derivative Spectrophotometric Determination of Cobalt in Alloys and Biological Samples after Preconcentration with the Ion Pair of Disodium 1-Nitroso-2-naphthol-3,6-disulfonate and Tetradecyldimethylbenzylammonium Chloride on Microcrystalline Naphthalene or Column Method

Cobalt was quantitatively retained by disodium 1-nitroso-2-naphthol-3,6-disulfonate (nitroso-R salt) and tetradecyldimethylbenzylammonium chloride (TDBA+Cl-) on microcrystalline naphthalene in the pH range 3.6 - 8.2 from large volumes of aqueous solutions of various alloys and biological samples. After filtration, a solid mass consisting of the cobalt complex and naphthalene was dissolved with 5 ml of dimethylformamide (DMF), and the metal was determined by third-derivative spectrophotometry. The cobalt complex could alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. The detection limit was 30 ppb (signal to noise ratio = 2) and the calibration curve was linear for 0.1 - 11 ppm in dimethylformamide solution with a correlation coefficient of 0.9996 by measuring the distance, d3A/d λ3, between λ1 (612 nm) and λ2 (579 nm). Eight replicated determinations of 2 ppm of cobalt in dimethylformamide solution gave a mean intensity (peak to peak signal between λ1 and λ2) of 0.436 with a relative standard deviation of ±0.91%. The sensitivity of the method was 0.215 (d3A/dnm3) ml/µg, which was found from the slope of the calibration curve. Various parameters, such as the effect of the pH, the volume of the aqueous phase and the interference of a number of metal ions on the determination of cobalt has been studied in detail to optimize the conditions for the determination cobalt in various alloys and biological samples.

Stability-Indicating Methods for Determining Omeprazole and Octylonium Bromide in the Presence of Their Degradation Products

Four stability-indicating assays were developed for determining omeprazole and octylonium bromide. Omeprazole is photodegraded and estimated in the presence of its degradation products sulphenamide (I) and benzimidazole sulphide (II) by 2 methods. The first method depends on use of first-, second-, and third-derivative spectrophotometry at 290.4, 320.6, and 311.6 nm, respectively. The second method is based on applying the charge-transfer technique with chloranil as pi acceptor to form a complex with omeprazole, the absorbance of which is measured at 377 nm. These methods determine omeprazole in concentration ranges of 5-20 micrograms/mL by first-, second-, and third-derivative spectrophotometry and 10-50 micrograms/mL by charge-transfer complexation with mean accuracies of 99.92 +/- 0.73, 99.71 +/- 1.02, 99.64 +/- 0.66, and 100.24 +/- 0.81%, respectively. Octylonium bromide is determined by a densitometric method using thin-layer chromatography in the presence of its degradation products p-[2-(n-octyoxy)benzoyl]-aminobenzoic acid (III) and diethyl-(2-hydroxyethyl)-methyl ammonium bromide (IV) without any interferences. Alternatively, octylonium bromide is evaluated by a colorimetric method using the acid dye rose bengal. The ion pair formed is extracted in chloroform at pH 4, and its absorbance is measured at 562 nm. These methods determine octylonium bromide in the presence of its degradation products in concentration ranges of 0.1-0.5 microgram/microL by densitometry and 4.5-22.5 micrograms/mL by colorimetry, with mean accuracies of 100.21 +/- 0.93 and 99.73 +/- 0.89%, respectively. The suggested methods were used to determine drugs in bulk powder, laboratory-prepared mixtures, and pharmaceutical dosage forms. Results were compared statistically with those obtained with reference methods.

Simultaneous determination of neodymium, erbium and holmium in rare earth mixtures with 2-phenyltrifluoroacetone and octylphenol poly(ethyleneglycol) ether by third-derivative spectrophotometry

The complexes of the rare earth metals with 2-phenyltrifluoroacetone in the presence of TX-100 are reported. The characteristic absorbances of neodymium, holmium and erbium complexes can be increased by factors of 8.5, 31 and 15 respectively, compared to those of the cholrides. The third-derivative spectra have been used to eliminate the interference of cerium, and the sensitivities are increased again by factors of 7.4, 5.5 and 6.5. A method for the direct determination of neodymium, erbium and holmium in rare earth mixtures is proposed.

TLC separation and derivative spectrophotometry of some amino acids

Chromatographic systems for the separation of amino acid mixtures on RP-18 as a stationary phase have been elaborated. The best results were obtained using methanol-water (1:1, v/v; 1:3, v/v; 1:5, v/v) as a mobile phase. The following amino acids have been examined: asparagine, arginine monohydrochloride, cystine, cysteine chloride, glycine, histidine monohydrochloride, hydroxyproline, isoleucine, leucine, lysine monochloride, methionine, ornithine monohydrochloride, phenylalanine, proline, threonine, tryptophan, tyrosine, serine, valine. Histidine (as monohydrochloride) and methionine were determined by first-, second- and third-derivative spectrophotometry in a mixture of several amino acids.

Determination of ternary mixtures of antibiotics, by ratio-spectra zero-crossing first- and third-derivative spectrophotometry

The ratio-spectra zero-crossing first- and third-derivative spectrophotometry have been used for determining ternary mixtures of penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts. The procedures are accurate, nondestructive and do not require resolutions of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 30 μg ml −1 of penicillin-G sodium and penicillin-G procain, and up to 42 μg ml −1 of dihydrostreptomycin sulphate. r = 0.9999 in each instance. Working wavelengths, 218.5, 211 and 236 nm, respectively, in the first-derivative mode, and 222.5, 311.5 and 242 nm in the third-derivative mode. Detection limits for each drug at p = 0.01 level of significance were calculated to be 0.058, 0.010 and 0.014 μg ml −1 and 0.14, 0.012 and 0.34 μg ml −1, in the first- and third-derivative methods, respectively. Both methods apply favourably to either laboratory mixtures or commercial injections.

Determination of a ternary mixture of penicillin-G sodium salt, penicillin-G procain salt and dihydrostreptomycin sulphate, by third-derivative spectrophotometry

Ternary mixtures of antibiotics, i.e. penicillin-G sodium salt, penicillin-G procain salt and dihydrostreptomycin sulphate salt, are assayed by ‘zero-crossing’ third-derivative spectrophotometry. Calibration plots follows Beer's law up to 40 μg/ml of penicillin-G sodium at 222.5 nm ( r = 0.9997), 46 μg/ml of penicillin-G procain at 217 nm ( r = 0.9999) and 36 μg/ml of dihydrostreptomycin sulphate at 211.5 nm ( r = 0.9999), in the presence of one another. Detection limits at p = 0.05 level of significance were calculated to be, respectively, 0.66, 0.41 and 0.25 μg/ml. The procedure is rapid, simple, nondestructive and does not require solution of equations. The method was successfully applied for determining laboratory mixtures and commercial injections.

Preconcentration of 1-(2-pyridylazo)—2-naphthol—iron(III)-capriquat on a membrane filter, and third-derivative spectrophotometric determination of iron(III)

Iron(III) was preconcentrated by collection on an organic solvent—soluble membrane filter (nitrocellulose (NC)) of the iron(III)–1-(2-pyridylazo)—2-naphthol (PAN) complex in the presence of capriquat as an oily quaternary ammonium salt. Third-derivative spectrophotometry was used for measurement of the third-derivative distance (d 3 A/dλ 3) between λ 1 = 520 nm and λ 2 = 590 nm or λ 3 = 660 nm and λ 4 = 724 nm of the iron(III)—PAN—capriquat complex or PAN—capriquat in dimethylsulfoxide (DMSO) following preconcentration. The calibration curve was linear in the range of 1–10 μg iron(III)/5.0 ml DMSO solution. The proposed method was about five-fold more sensitive and more selective than using zero-order spectrophotometry.

Determination of Silver(I) by an Association Complex Formation between Silver-Adenine and Eosin

A sensitive and selective spectrophotometric determination of silver(I) based on an association complex between silver-adenine and eosin was established. The apparent molar absorptivity of the complex, without solvent extraction, was 1.1x105 dm3 mol-1 cm-1 at 560 nm. No metal ion interfered in an equimolar ratio of silver(I) among the metal ions examined. The method was applied to assays of silver in silver solder and silver protein: the results were in good agreement with those obtained by ICP-AES. The sensitivity could be further enhanced about 5-10 times over that of spectrophotometry with the third-derivative spectrophotometry and/or the fluorescence quenching method. Thermodynamic parameters (ΔG=—6.34 kcal mol-1, ΔH=—28.17 kcal mol-1 and ΔS=—72.73 cal mol-1 K-1) and the binding parameters (n=0.98 and K=4.10x104 M-1 at 27°C) suggest that colored complex formed in this reaction system is an association complex between silver-adenine and eosin.

Simultaneous third-derivative spectrophotometric determination of copper and nickel in iron alloys and aluminium alloy

A method is proposed for the simultaneous determination of copper and nickel by third-derivative spectrophotometry based on the absorption spectra of their complexes with cyanide ion in the ultraviolet range. The method allows the determination of 0.55–5.8 μg/ml of copper and 0.55–6.8 μg/ml of nickel. The relative standard deviation for 11 determinations of 1.5 μl/ml of copper and nickel were 0.78 and 0.72%, respectively. The detection limits were 0.10,μg/ml for nickel and 0.13 μg/ml for copper. The method has been applied to direct determination of copper and nickel in iron alloys and an aluminium alloy without any separation.

Simultaneous Determination of Carboxyhemoglobin and Total Hemoglobin in Carbon Monoxide-Intoxicated Patients by Use of Third-Derivative Spectrophotometry

Abstract A third-derivative spectrophotometric method for measuring the carboxyhemoglobin (HbCO) percent content and the amount of hemoglobin not bound to the toxic gas and hence available for oxygen transport (functional Hb) is proposed. The method is quite straightforward, rapid and inexpensive and can be used to diagnose CO intoxications with a high precision as regards the severity of the clinical picture involved.

Direct Determination of Copper in Iron Alloys and Aluminium Alloys by Ultraviolet Third-Derivative Spectrophotometry

Abstract In this paper the absorption spectra of the copper complex with cyanide ion have been studied by conventional and derivative spectrophotometry. The use of third-derivative spectra both eliminates the interference from other metals and improves the sensitivity. Beer's law is obeyed for 0.64–3.2 μg/ml of copper. The relative standard deviation for 7 determinations 1.5 μg/ml of copper was 0.78%. The detection limit, corresponding to a signal-to-noise ratio of 2, was found to be 0.15 μg/ml. The suggested method has been applied successfully to the analysis of some iron alloys and aluminium alloys without any separation.