2-acetylpyridine Thiosemicarbazone Research Articles

One-Step Synthesis of Biocompatible Thiosemicarbazone Functionalized Copper Oxide Nanoparticles: Evaluation of Enhanced Antibacterial Activity

Organic–inorganic hybrid bioactive nanomaterials were sonochemically synthesized by covalent anchoring of 2-acetylpyridine thiosemicarbazone on the surface of CuO nanoparticles using two different approaches. The prepared nanoparticles were characterized by a combination of physico-chemical and spectroscopic techniques. The synergetic bactericidal activity of CuO and thiosemicarbazone moieties in prepared nanomaterials was tested in vitro using the zone inhibition methods against Gram positive and Gram negative bacterial strains. Additionally, the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were also determined. Results prove that CuO and functionalized CuO nanoparticles synthesized by the sonochemical method in present study show improved antibacterial activities and they could be used in the design of more efficient antibacterial materials for pharmaceutical applications.

Cooordination compounds of Cu(II) and Bi(III) with aminopolycarboxylate ligands and 4-ethyl-, 4-phenyl- thiosesemicarbazones of 2-acetylpyridine

The paper deals with the synthesis and analysis of two series of homometallic coordination compounds with 2-acetylpyridine thiosemicarbazones, with different substituents in the N4 position, having the general formulas {Cu(4XAcpytsc)}2Cu(APC)·nH2O in case of Cu(II) and Bi(HAPC)(4XHAcpytsc)m·nH2O for Bi(III) ions. Targeting at getting synergistic effects, two series of heterometallic coordination compounds of general formula {Cu(4XAcpytsc)}Bi(APC)·nH2O with two aminopolycarboxylate ions have been synthesized (n=1-8; m = 1 or 2; APC = edta4-, cdta4-), (4XAcpytsc) monodeprotonated or non-protonated (4XHAcpysc) form of 4-ethyl- or 4-phenyl-thiosemicarbazones of 2-acetylpyridine (Acpytsc). The antioxidant property of the obtained homo- and heterometallic compounds was identified. The results have shown that the highest antioxidant property has the homometallic compound of Bi(III) with 2-acetylpyridine 4-phenyl-thiosemicarbazone and edta4- anion, with IC50 = 0,71 μM which is approximately 13 times higher than the free ligand and 56 times higher than the reference Trolox.

A Lindqvist-Type [W <sub>6</sub>O <sub>19</sub>] <sup>2</sup>‒ Organic-Inorganic Compound: Synthesis, Characterization, Antibacterial Activity and Preliminary Studies on the Mechanism of Action

In this paper, a new organic-inorganic hybrid compound [Co(L)2]2 [W6O19](1) (HL = 2-acetylpyridine thiosemicarbazone) was prepared and characterized. The compound exhibits remarkable antibacterial activity by determination of minimum inhibitory concentration (MIC) against Staphylococcus aureus (S. aureus, 0.06 µg/mL) and Escherichia coli (E. coli, 0.24 µg/mL), respectively. Furthermore, the potential mechanism of 1 was studied in detail. The potential causes of bacteria death were cell wall/membrane disruption, inhibition of intracellular respiratory chain dehydrogenases activity (RCD), breach of reactive oxygen species (ROS) and glutathione (GSH).

A New Cobalt(III)/[Mo6O19]2− Heterogeneous Catalyst for Promoting the Oxidative Coupling of Amines to Imines

Currently, the efficient preparation of imines is still a great challenge under mild conditions. In this article, by incorporating 2-acetylpyridine thiosemicarbazone (HL), Co(NO3)2·6H2O and Na2MoO4·2H2O, a new compound [Co(L)2]2[Mo6O19] (1) was prepared and characterized by elemental analysis (EA), infrared (IR) spectra, ultraviolet–visible (UV–Vis) spectra, powder X-ray diffractometry (PXRD) spectra, X-ray photoelectron spectroscopy (XPS) and X-ray single-crystal diffraction. 1 could be used as a heterogeneous catalyst for oxidative coupling of amines in a comparatively mild condition. Furthermore, 1 exhibited remarkable catalytic performance for oxidation coupling of amines to imines with high yield in the presence of tert-butyl hydroperoxide (TBHP) (up to 92%). Kinetic measurements of the oxidation of benzylamine suggest that the rate law is r = k′[BnNH2][TBHP] (k′ = k[cat] = 0.2338 L mol−1 h−1). Additionally, 1 can be recycled at least three times without a distinct loss of activity. A new compound [Co(L)2]2[Mo6O19] (1) (HL = 2-acetylpyridine thiosemicarbazone) has been synthesized and characterized. Furthermore, 1 can efficiently catalyze the oxidative coupling of amines to imines with high activity and exhibited good recyclability and high stability.

A comparative study of α- N -pyridyl thiosemicarbazones: Spectroscopic properties, solution stability and copper(II) complexation

Abstract The effects of methyl substituents at different positions on the 2-formylpyridine thiosemicarbazone (FTSC) core structure on various physico-chemical properties were investigated. Proton dissociation processes, aqueous solution stability, isomer distribution in different solvents, fluorescence properties and lipophilic character of FTSC, pyridine-2-carboxaldehyde N 4 , N 4 -dimethylthiosemicarbazone (PTSC), 2-acetylpyridine thiosemicarbazone (AcFTSC) and 2-acetylpyridine N 4 , N 4 -dimethylthiosemicarbazone (AcPTSC) were studied and compared under the same conditions. There are more and more indications that Cu(II) ions play an important role in the biological activity of anticancer thiosemicarbazones. Therefore, the complex formation equilibria of FTSC with Cu(II) ions were studied by pH-potentiometry, UV–visible spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy to determine stoichiometry, stability constants and solution structures of the complexes formed in aqueous solution (with 30% DMSO). Mono-ligand complexes in different protonation states were identified such as [CuLH] 2+ , [CuL] + and [CuL(OH)] with (N pyridyl ,N,S)(H 2 O), (N pyridyl ,N,S − )(H 2 O) and (N pyridyl ,N,S − )(OH) coordination modes, respectively. At ligand excess two kinds of isomers of a bis complex [CuL 2 ] were detected at pH > 7, in which binding of the ligands via (N pyridyl ,N,S − )(N) and (N pyridyl ,N,S − )(S − ) donor sets is probable at the equatorial positions. Based on the stability data, [CuL] + complexes of the α- N -pyridyl thiosemicarbazones are predominant at pH 7.4 at 1:1 metal-to-ligand ratio possessing such high solution stability that their decomposition is not likely even at biologically relevant micromolar concentrations. In addition, FTSC and all methylated derivatives investigated show similar Cu(II) binding abilities which is in contrast to the respective Fe(II)/(III) complexes where terminal dimethylation distinctly increases the solution stabilities.

Trace determination of zinc in soil and vegetable samples by spectrophotometry using pyridoxal thiosemicarbazone and 2-acetyl pyridine thiosemicarbazone

The rapid and continuous progress in trace analysis of metals is associated with development of several new techniques such as spectrophotometry. Thiosemicarbazones have been used as chromogenic re...

Structure-Activity Relationships of Di-2-pyridylketone, 2-Benzoylpyridine, and 2-Acetylpyridine Thiosemicarbazones for Overcoming Pgp-Mediated Drug Resistance.

Multidrug resistance (MDR) mediated by P-glycoprotein (Pgp) represents a significant impediment to successful cancer treatment. The compound, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), has been shown to induce greater cytotoxicity against resistant cells than their nonresistant counterparts. Herein, the structure-activity relationships of selected thiosemicarbazones are explored and the novel mechanism underlying their ability to overcome resistance is further elucidated. Only thiosemicarbazones with electron-withdrawing substituents at the imine carbon mediated Pgp-dependent potentiated cytotoxicity, which was reversed by Pgp inhibition. Treatment of resistant cells with these thiosemicarbazones resulted in Pgp-dependent lysosomal membrane permeabilization (LMP) that relied on copper (Cu) chelation, reactive oxygen species generation, and increased relative lipophilicity. Hence, this study is the first to demonstrate the structural requirements of these thiosemicarbazones necessary to overcome MDR. We also demonstrate the mechanism that enables the targeting of resistant tumors, whereby thiosemicarbazones "hijack" lysosomal Pgp and form redox-active Cu complexes that mediate LMP and potentiate cytotoxicity.

Spectrophotometric determination of Cu(II) in soil and vegetable samples collected from Abraha Atsbeha, Tigray, Ethiopia using heterocyclic thiosemicarbazone.

Two selective and sensitive reagents, 2-acetylpyridine thiosemicarbazone (2-APT) and 3-acetylpyridine thiosemicarbazone (3-APT) were used for the spectrophotometric determination of Cu(II). Both reagents gave yellowish Cu(II) complex at a pH range of 8.0–10.0. Beer’s law was obeyed for Cu(II)–2-APT and Cu(II)–3-APT in the concentration range of 0.16–1.3 and 0.44–1.05 µg/mL, respectively. The molar absorptivity and of Cu(II)–2-APT and Cu(II)–3-APT were 2.14 × 104 at 370 nm, and 6.7 × 103 L/mol cm at 350 nm, respectively, while the Sandell’s sensitivity were 0.009 and 0.029 µg/cm2 in that order. The correlation coefficient of the standard curves of Cu(II)–2-APT and Cu(II)–3-APT were 0.999 and 0.998, respectively. The detection limit of the Cu(II)–2-APT and Cu(II)–3-APT methods were 0.053 and 0.147 µg/mL, respectively. The results demonstrated that the procedure is precise (relative standard deviation <2 %, n = 10). The method was tested for Cu(II) determination in soil and vegetable samples. Comparisons of the results with those obtained using a flame atomic absorption spectrophotometer for Cu(II) determination also tested the validity of the method using paired sample t test at the 0.05 level showing a good agreement between them.

Zinc(II)-Thiosemicarbazone Complexes Are Localized to the Lysosomal Compartment Where They Transmetallate with Copper Ions to Induce Cytotoxicity.

As the di-2-pyridylketone thiosemicarbazone (DpT) and 2-acetylpyridine thiosemicarbazone (ApT) series show potent antitumor activity in vitro and in vivo, we synthesized their fluorescent zinc(II) complexes to assess their intracellular distribution. The Zn(II) complexes generally showed significantly greater cytotoxicity than the thiosemicarbazones alone in several tumor cell-types. Notably, specific structure-activity relationships demonstrated the importance of the di-2-pyridyl pharmacophore in their activity. Confocal fluorescence imaging and live cell microscopy showed that the Zn(II) complex of our lead compound, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which is scheduled to enter clinical trials, was localized to lysosomes. Under lysosomal conditions, the Zn(II) complexes were shown to transmetallate with copper ions, leading to redox-active copper complexes that induced lysosomal membrane permeabilization (LMP) and cytotoxicity. This is the first study to demonstrate direct lysosomal targeting of our novel Zn(II)-thiosemicarbazone complexes that mediate their activity via transmetalation with copper ions and LMP.

Kinetico-mechanistic studies on methemoglobin generation by biologically active thiosemicarbazone iron(III) complexes

The oxidation of human oxyhemoglobin (HbO2) to methemoglobin (metHb) is an undesirable side effect identified in some promising thiosemicarbazone anti-cancer drugs. This is attributable to oxidation reactions driven by FeIII complexes of these drugs formed in vivo. In this work the FeIII complexes of selected 2-benzoylpyridine thiosemicarbazones (HBpT), 2-acetylpyridine thiosemicarbazones (HApT), and the clinically trialled thiosemicarbazone, Triapine® (3-amino-2-pyridinecarboxaldehyde thiosemicarbazone, H3-AP), have been studied. This was achieved by time-resolved UV–Visible absorption spectroscopy and the sequential oxidation of the α- and β-chains of HbO2 at distinctly different rates has been identified. A key structural element, namely a terminal –NH2 group on the thiosemicarbazone moiety, was found to be an important common feature of the most active HbO2 oxidising complexes that were investigated. Therefore, these studies indicate that an unsubstituted –NH2 moiety at the terminus of the thiosemicarbazone group should be avoided in the design of future compounds from this class.

Synthesis, molecular structure, spectral analysis, natural bond order and intramolecular interactions of 2-acetylpyridine thiosemicarbazone: A combined DFT and AIM approach

2-Acetylpyridine thiosemicarbazone was synthesized and characterized by elemental analysis, 1H, 13C NMR, IR, UV and ESI-MS mass spectrometry. Quantum chemical calculations have been performed at DFT level of theory using B3LYP functional and 6-31G (d, p) as basis set. Potential energy distribution (PED) for the normal modes of vibrations was done using Gar2ped program. The time dependent density functional theory (TD-DFT) was used to assign the various electronic transitions within molecule in gas as well as solvent phase. Non linear optical (NLO) behavior of title compound was investigated by the computed value of first hyperpolarizability (β0). Stability of molecule as a result of hyperconjugative interactions and electron delocalization was analyzed using NBO analysis. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Intramolecular interactions were analyzed by AIM approach. The chemical reactivity descriptors were calculated to study the reactive sites within molecule.

Synthesis, characterization and crystal structure of cobalt(III) complexes containing 2-acetylpyridine thiosemicarbazones: DNA/protein interaction, radical scavenging and cytotoxic activities

The synthesis, structure and biological studies of cobalt(III) complexes supported by NNS-tridentate ligands are reported. Reactions of 2-acetylpyridine N-substituted thiosemicarbazone (HL1–3) with [CoCl2(PPh3)2] resulted [Co(L1–3)2]Cl (1–3) which were characterized by elemental analysis and various spectral studies. The molecular structure of the complex 1 has been determined by single crystal X-ray diffraction studies. In vitro DNA binding studies of complexes 1–3 carried out by fluorescence studies and the results revealed the binding of complexes to DNA via intercalation. The binding constant (Kb) values of complexes 1–3 from fluorescence experiments showed that the complex 3 has greater binding propensity for DNA. The DNA cleavage activity of the complexes 1 and 3 were ascertained by gel electrophoresis assay which revealed that the complexes are good DNA cleavage agents. Further, the interactions of the complexes with bovine serum albumin (BSA) were also investigated using fluorescence spectroscopic method, which showed that the complexes 1–3 could bind strongly with BSA. The antioxidant property of the complexes was evaluated to test their free-radical scavenging ability. Furthermore, in vitro cytotoxicity of the complexes against MCF-7 and A431 cell lines was assayed which showed higher activity and efficiently vanished the cancer cells even at low concentrations.

N4-Phenyl-substituted 2-acetylpyridine thiosemicarbazones: Cytotoxicity against human tumor cells, structure–activity relationship studies and investigation on the mechanism of action

N4-Phenyl 2-acetylpyridine thiosemicarbazone (H2Ac4Ph; N-(phenyl)-2-(1-(pyridin-2-yl)ethylidene)hydrazinecarbothioamide) and its N4-ortho-, -meta- and -para-fluorophenyl (H2Ac4oFPh, H2Ac4mFPh, H2Ac4pFPh), N4-ortho-, -meta- and -para-chlorophenyl (H2Ac4oClPh, H2Ac4mClPh, H2Ac4pClPh), N4-ortho-, -meta- and -para-iodophenyl (H2Ac4oIPh, H2Ac4mIPh, H2Ac4pIPh) and N4-ortho-, -meta- and -para-nitrophenyl (H2Ac4oNO2Ph, H2Ac4mNO2Ph, H2Ac4pNO2Ph) derivatives were assayed for their cytotoxicity against human malignant breast (MCF-7) and glioma (T98G and U87) cells. The compounds were highly cytotoxic against the three cell lineages (IC50: MCF-7, 52–0.16nM; T98G, 140–1.0nM; U87, 160–1.4 nM). All tested thiosemicarbazones were more cytotoxic than etoposide and did not present any haemolytic activity at up to 10−5M. The compounds were able to induce programmed cell death. H2Ac4pClPh partially inhibited tubulin assembly at high concentrations and induced cellular microtubule disorganization.

Gold(I) complexes with thiosemicarbazones: Cytotoxicity against human tumor cell lines and inhibition of thioredoxin reductase activity

Complexes [Au(H2Ac4DH)Cl]∙MeOH ( 1) [Au(H 22Ac4Me)Cl]Cl ( 2) [Au(H 22Ac4Ph)Cl]Cl∙2H 2O ( 3) and [Au(H 22Bz4Ph)Cl]Cl ( 4) were obtained with 2-acetylpyridine thiosemicarbazone (H2Ac4DH), its N(4)-methyl (H2Ac4Me) and N(4)-phenyl (H2Ac4Ph) derivatives, as well as with N(4)-phenyl 2-benzoylpyridine thiosemicarbazone (H2Bz4Ph). The compounds were cytotoxic to Jurkat (immortalized line of T lymphocyte), HL-60 (acute myeloid leukemia), MCF-7 (human breast adenocarcinoma) and HCT-116 (colorectal carcinoma) tumor cell lines. Jurkat and HL-60 cells were more sensitive than MCF-7 and HCT-116 cells. Upon coordinating to the gold(I) metal centers in complexes ( 2) and ( 4), the cytotoxic activity of the H2Ac4Me and H2Bz4Ph ligands increased against the HL-60 and Jurkat tumor cell lines. 2 was more active than auranofin against both leukemia cells. Most of the studied compounds were less toxic than auranofin to peripheral blood mononuclear cells (PBMC). All compounds induced DNA fragmentation in HL-60 and Jurkat cells indicating their pro-apoptotic potential. Complex ( 2) strongly inhibited the activity of thioredoxin reductase (TrxR), which suggests inhibition of TrxR to be part of its mechanism of action.

Zinc(II) complexes of 2-acetyl pyridine 1-(4-fluorophenyl)-piperazinyl thiosemicarbazone: Synthesis, spectroscopic study and crystal structures – Potential anticancer drugs

2-Acetyl pyridine thiosemicarbazone containing an 1-(4-fluorophenyl)-piperazinyl ring incorporated at N(4)-position, HAcPipPheF (1) and the zinc(II) complexes [Zn(AcPipPheF)(2)] (2) and [Zn(OAc)(AcPipPheF)](2) (3) have been prepared and structurally characterized by means of vibrational and NMR ((1)H and (13)C) spectroscopy. The crystal structures of the compounds 1-3 have been determined by X-ray crystallography. The metal coordination geometry of [Zn(AcPipPheF)(2)] is described as distorted octahedral configuration in a trans-N-cis-N-cis-S configuration. In [Zn(OAc)(AcPipPheF)](2) one of the acetato group exhibits monoatomic bridge and the other bridges in a bidentate manner. The zinc(1) metal ion is coordinated in a distorted octahedral configuration while the metal coordination of Zn(2) is described as distorted square pyramidal. Biomedical studies revealed that, compounds 1-3 displayed potent anticancer activity. The antiproliferative activity of 1-3 was found to be considerably stronger than that of cis-platin. The IC(50) values range from 26 to 90nM, against all cell lines tested, while for cis-platin the IC(50) values range from 2 to 17microM and for the zinc salt, ZnCl(2), the IC(50) values range from 81 to 93microM. The complex 3 shows the highest activity against all four cancer cell lines and the highest selectivity against K562 and MDA-MB-453 cancer cell lines. The compounds inhibited tumor cell proliferation by arresting the cell cycle progression at the S phase.

Synthesis and structural studies of gallium(III) and indium(III) complexes of 2-acetylpyridine thiosemicarbazones

Four 2-acetylpyridine 4 N-alkyl thiosemicarbazones, and their Ga(III) and In(III) complexes have been prepared and characterised by fluorescence, UV–Vis, IR, 1H and 13C NMR spectroscopy, mass spectrometry and X-ray crystallographic analysis. Comparison of the crystal structures gave an insight into the nature of the complexes formed, demonstrating a preference for [ ML 2] + type complexes with gallium and [ MLX 3] species with indium. Stability studies on two candidates indicated that complex [InL 3Cl 2MeOH] was stable to chemical degradation for prolonged periods in human serum, giving this complex potential for further biological evaluation.

Impact of Metal Coordination on Cytotoxicity of 3-Aminopyridine-2-carboxaldehyde Thiosemicarbazone (Triapine) and Novel Insights into Terminal Dimethylation

The first metal complexes of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine) were synthesized. Triapine was prepared by a novel three-step procedure in 64% overall yield. In addition, a series of related ligands, namely, 2-formylpyridine thiosemicarbazone, 2-acetylpyridine thiosemicarbazone, 2-pyridineformamide thiosemicarbazone, and their N(4)-dimethylated derivatives (including the N(4)-dimethylated analogue of Triapine) were prepared, along with their corresponding gallium(III) and iron(III) complexes with the general formula [M(L)(2)](+), where HL is the respective thiosemicarbazone. The compounds were characterized by elemental analysis, (1)H and (13)C NMR, IR and UV-vis spectroscopies, mass spectrometry, and cyclic voltammetry. In addition, Triapine and its iron(III) and gallium(III) complexes were studied by X-ray crystallography. All ligands and complexes were tested for their in vitro antiproliferative activity in two human cancer cell lines (41M and SK-BR-3), and structure-activity relationships were established. In general, the coordination to gallium(III) increased the cytotoxicity while the iron(III) complexes show reduced cytotoxic activity compared to the metal-free thiosemicarbazones. Selected compounds were investigated for the capacity of inhibiting ribonucleotide reductase by incorporation of (3)H-cytidine into DNA.

2-Acetylpyridine Thiosemicarbazones are Potent Iron Chelators and Antiproliferative Agents: Redox Activity, Iron Complexation and Characterization of their Antitumor Activity

Through systematic structure-activity studies of the 2-benzoylpyridine thiosemicarbazone (HBpT), 2-(3-nitrobenzoyl)pyridine thiosemicarbazone (HNBpT) and dipyridylketone thiosemicarbazone (HDpT) series of iron (Fe) chelators, we identified structural features necessary to form Fe complexes with potent anticancer activity (J. Med. Chem. 2007, 50, 3716-3729). In this investigation, we generated the related 2-acetylpyridine thiosemicarbazone (HApT) analogues to examine the influence of the methyl group at the imine carbon. Four of the six HApT chelators had potent antitumor activity (IC(50): 0.001-0.002 microM) and Fe chelation efficacy that was similar to the most effective HBpT and HDpT ligands. The HApT Fe complexes had the lowest Fe(III/II) redox potentials of any thiosemicarbazone series we have generated. This property, in combination with their ability to effectively chelate cellular Fe, make the HApT series one of the most potent antiproliferative agents developed by our group.

Preparation and Biological Evaluation of a [55Co]-2-Acetylpyridine Thiosemicarbazone

Due to the anti-proliferative properties of cobalt-thiosemicarbazone complexes, the production of [55Co](III)-bis-(2-acetylpyridine thiosemicarbazone) ([55Co](III)[APTS]2) was investigated. Co-55 (T1/2=17.53 h) was produced by 150 μA irradiation of a natural nickel target by 15 MeV protons. The 55Co was separated from the irradiated target material using a two-step method with a radiochemical yield of &gt;95% followed by radionuclidic and chemical purity control. [55Co](III)chloride was mixed with 2-acetylpyridine thiosemicarbazone for 30 min at room temperature to yield [55Co](III)[APTS]2 (radiochemical purity &gt; 98% shown by RTLC/HPLC). A specific activity of about 10–20 Ci/mmol was obtained. The final solution was diluted in normal saline to 5% ethanolic solution for biological evaluation. The stability of the final product was checked in the absence and presence of human serum at 37°C to 24 h. The partition co-efficient of the final complex at the pH of 7 was 1.00±0.08. A significant tumor accumulation (%ID/g; 3.5%) was observed in tumoral tissue 21 h post injection in fibrosarcoma-bearing mice by biodistribution studies. Co-incidence imaging also demonstrated tumor uptake from 21–35 h however at 35 h tumor uptake is more specific and significant.

Spectrophotometric determination of cobalt in biological samples using 2-acetylpyridine semicarbazone

Analytical application of 2-acetylpyridine thiosemicarbazone (APT) and 2-acetylpyridine semicarbazone is described for the direct non-extractive spectrophotometric determination of cobalt. The reagents react with cobalt in acidic medium (pH 6.0, sodium acetate-acetic acid buffer) to form orange yellow colored 1: 2 (M: L) complexes. The colour reactions are instantaneous and absorbance values remain constant for over 24 h. The molar absorptivity and Sandell's sensitivity of APT and APS methods are found to be 1.25 x 10 4 and 1.45 x 10 4 L mol -1 cm -1 and 0.0047 and 0.004 μg cm -2 of Co II respectively. The systems obey Beer's law in the range of 0.236-2.357 μg/ml of Co II . Since APS method is more sensitive it was applied for the determination of cobalt in biological samples.