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Full-Text Articles in Chemistry

General Character Of Electrochaemically Adsorbed Cobalt On Smooth Platinum In Solutions Of Various Ph, Gülcemal Yildiz, Sadiq Kuluyev, Figen Kadirgan Jan 1997

General Character Of Electrochaemically Adsorbed Cobalt On Smooth Platinum In Solutions Of Various Ph, Gülcemal Yildiz, Sadiq Kuluyev, Figen Kadirgan

Turkish Journal of Chemistry

The adsorption of cobalt adatoms on to a smooth platinum electrode at different potentials was studied by voltammetric methods. The amount of cobalt coverage was determined from the hydrogen region of the platinum electrode. The number of electrons per adatom species was calculated. The experiments were carried out in the pH interval between 0-3 in H_{2}SO_{4}-containing solutions.


A Computational Study On The Conformational Behaviour Of 1,1,2-Trihydroxyethane In Solution, Safiye Sağ Erdem, Tereza Varnali, Viktorya Avi̇yente Jan 1997

A Computational Study On The Conformational Behaviour Of 1,1,2-Trihydroxyethane In Solution, Safiye Sağ Erdem, Tereza Varnali, Viktorya Avi̇yente

Turkish Journal of Chemistry

The conformational space of 1,1,2-trihydroxyethane were investigated with the PM3 method both in gas phase and in solution. Ab initio calculations at 6-31G level were also conformational equilibria in solution were studied and used to explain the behaviour of 2-hydroxycyclohexanone propylene and ethylene ketals.


Complexes Of Zn(Ii), Pd(Ii), Hg(Ii), Pb(Ii), Cu(I), Ag(I) And Tl(I) With 4-Amino-5-Mercapto-3-(O-Tolyloxymethyl)-1,2,4-Triazole, B. Narayana, M. R. Gajendragad Jan 1997

Complexes Of Zn(Ii), Pd(Ii), Hg(Ii), Pb(Ii), Cu(I), Ag(I) And Tl(I) With 4-Amino-5-Mercapto-3-(O-Tolyloxymethyl)-1,2,4-Triazole, B. Narayana, M. R. Gajendragad

Turkish Journal of Chemistry

The synthesis and characterization of complexes of Zn(II), Pd(II), Cd(II), Hg(II), Pb(II), Cu(I), Ag(I), and Tl(I) with 4-amino-5-mercapto-3-(o- tolyloxymethyl)-1,2,4-triazole are described. Based on analytical results, electronic and infrared spectral data and magnetic susceptibility measurements suitable structures have been proposed.


Topological Constraints On Hmo Hetereoatom Parameters, Lemi Türker Jan 1997

Topological Constraints On Hmo Hetereoatom Parameters, Lemi Türker

Turkish Journal of Chemistry

Within the Hückel molecular orbital framework, the effect of topological factors on the selection of heteroatom parameters for heteroconjugated systems is discussed.


Factors Influencing The Angle Of Total Ii-Electron Energies Of Alternant Hydrocarbons, Lemi Türker Jan 1997

Factors Influencing The Angle Of Total Ii-Electron Energies Of Alternant Hydrocarbons, Lemi Türker

Turkish Journal of Chemistry

Within the framework of the Hückel molecular orbital theory, the topological factors affecting the angle of total \pi-electron energies of alternant hydrocarbons were investigated.


Controlled Release Of Aldicarb From Carboxymethylcellulese Microcapsules, M. Yakup Arica, Mustafa Yi̇ği̇toğlu, Mustafa Lale, Fatma N. Kök, Vasıf Hasirci Jan 1997

Controlled Release Of Aldicarb From Carboxymethylcellulese Microcapsules, M. Yakup Arica, Mustafa Yi̇ği̇toğlu, Mustafa Lale, Fatma N. Kök, Vasıf Hasirci

Turkish Journal of Chemistry

Sodium carboxymethyl cellulose was converted into microspheres by crosslinking with aluminum chloride. Various microsheres with different amounts of crosslinker, biopolymer of various concentrations and molecular weights, and with different pesticide (Aldicarb) contents and pesticide to polymer ratios were prepared. The pesticide encapsulation efficiencies and aldicarb release kinetics of the resultant microcapsules were investigated. It was possible to modify the release behaviour by varying the above parameters and to have drug release with half-lives longer than 100 hours in aqueous media. The release kinetics were described by first order and zero order kinetics.


Spectrophotometric Determination Of The Pk_A Values Of Some Aminoacid Complexes Of Pentacyanoferrate(Ii) And Pentacyanoruthenate(Ii), Yakup Baran, Şebnem Baran, N. Kemal Tunali Jan 1997

Spectrophotometric Determination Of The Pk_A Values Of Some Aminoacid Complexes Of Pentacyanoferrate(Ii) And Pentacyanoruthenate(Ii), Yakup Baran, Şebnem Baran, N. Kemal Tunali

Turkish Journal of Chemistry

The syntheses, pK_a and spectrospcopic characterization of [Fe(CN)_5(H_2O)]^{-3} and [Ru(CN)_5(H_2O)]^{-3} complexes of alanine(Ala), glycine(Gly), valine(Val), lysine(Lys), arginine(Arg) and cysteine(Cys) complexes were investigated in aqueous solution. The spectra of the complexes containing amino acid ligands were similar to that of [Fe(CN)_5(NH_3)]^{-3}. The pK_a values of the complexes were measured by spectrophotometric titration at 22^{\circ}C and \mu =0.100 M(NaClO_4).


Carbonic Anhydrase From Nicotiana Tabacum Leaves, Nazan Demi̇r, Yaşar Demi̇r Jan 1997

Carbonic Anhydrase From Nicotiana Tabacum Leaves, Nazan Demi̇r, Yaşar Demi̇r

Turkish Journal of Chemistry

In this study, carbonic anhydrase (CA: carbonate hydrolyase; E.C.4.2.1.1) was purified from adult {\it Nicotiana tabacum} leaves and studied biochemically. The enzyme was purified twice times by using (NH$_4)_2SO_4 precipation and DEAE-cellulose column chromatography, and its activity was determined for two different substrates (CO_2 and p-nitrophenyl acetate). The enzyme obtained from the ion exchange column was purified 40.7 fold and the purity was controlled by 3\%-10\% discontinuous SDS-PAGE. The pH of the purified enzyme varied between 6.0 and 7.2, the optimum being 6.9. V_{max} and K_m values were calculated with p-nitrophenyl acetate (0.1524 mM, 0.5446 mM, respectively) as substrate. The …


Electron Spin Resonance Studies On Cobalt Carbonic Anhydrase-Substrate Complexes, Çigdem Nuhoğlu, Nazan Demi̇r, Barbaros Nalbantoğlu, Ö. İrfan Küfrevi̇oğlu, Y. Kemal Yoğurtçu, Hasan Özdemi̇r, Enise Ayyildiz Jan 1997

Electron Spin Resonance Studies On Cobalt Carbonic Anhydrase-Substrate Complexes, Çigdem Nuhoğlu, Nazan Demi̇r, Barbaros Nalbantoğlu, Ö. İrfan Küfrevi̇oğlu, Y. Kemal Yoğurtçu, Hasan Özdemi̇r, Enise Ayyildiz

Turkish Journal of Chemistry

The native zinc atom of bovine erythrocyte carbonic anhydrase purified by affinity choromatography was removed by dialysis against pyridine 2,6-dicarboxylic acid. Cobalt carbonic anhydrase was prepared from the zinc-free apoenzyme. The binding conditions of CO_2 and p-nitrophenylacetate to cobalt carbonic anhydrase were investigated by electron spin resonance at different pH levels.


A Novel Glycosidicly Linked Piperidine Alkaloid From Cyclamen Coum, Nurettin Yayli, Cemalettin Baltaci Jan 1997

A Novel Glycosidicly Linked Piperidine Alkaloid From Cyclamen Coum, Nurettin Yayli, Cemalettin Baltaci

Turkish Journal of Chemistry

The structure of a novel piperidine type alkaloid from {\it Cyclamen coum} was established as 2-\beta-D-glycopyranosyl-2-undecil-3,5-dihydroxy-6-carboxypiperidine, {\bf 1,} whose structure has been deduced from spectral data.


A Quantum-Chemical Investigation On 3-(4h-1,2,4-Triazol-4-Yl)-1h-1,2,4-Triazole, Rıza Abbasoğlu, Necdet Saltek, A. Aykut İki̇zler Jan 1997

A Quantum-Chemical Investigation On 3-(4h-1,2,4-Triazol-4-Yl)-1h-1,2,4-Triazole, Rıza Abbasoğlu, Necdet Saltek, A. Aykut İki̇zler

Turkish Journal of Chemistry

The molecular conformations and electronic properties of the 3-(4H-1,2,4-triazol-4-yl)-1H-1,2,4-triazole molecule containing various reaction centers were investigated by the semiempirical methods MNDO, AM1 and PM3. The most stable conformation of the molecule was determined to be the planar conformation. The total energies, heats of formation, dipole moments, rotational barriers, geometric parameters, ionization potentials, full atomic charges, energies of frontier molecular orbitals (E_{HOMO} and E_{LUMO}) and their electron densities were calculated and discussed. In order to determine the protonation sites of the 3,4'-bitriazole system, the molecular electrostatic potential (MESP) of the molecule has also been calculated. The conformations and electronic properties of …


Influence Of Some Crosslinkers On The Swelling Of Acrylamide-Crotonic Acid Hydrogels, Erdener Karadağ, Dursun Saraydin, Olgun Güven Jan 1997

Influence Of Some Crosslinkers On The Swelling Of Acrylamide-Crotonic Acid Hydrogels, Erdener Karadağ, Dursun Saraydin, Olgun Güven

Turkish Journal of Chemistry

Acrylamide-crotonic acid hydrogels in the form of rods are prepared by \gamma-irradiation of quaternary mixtures of acrylamide-crotonic acid-crosslinker-water with 2.6 and 5.2 kGy \gamma-rays. The influence of the applied dose, the relative content of crotonic acid and crosslinkers such as ethylene glycol dimethacrylate, 1.4 butanediol dimethacrylate and N,N' methylenebisacrylamide on the swelling properties of the gel, the diffusional behaviour of water, the diffusion coefficient, and the network parameters of hydrogel systems are examined. Acrylamide-crotonic acid hydrogels containing various crosslinkers had a maximum swelling in the range 240-850 \%. Water diffusion to hydrogels was non-Fickian. The diffusion coefficients varied between 4.6 …


Investigation Of H-Bond On Fluorescence Changes In Benzene Derivations And Different Acceptor Systems, Nursel Acar Bayri, Özgül Koçak Jan 1997

Investigation Of H-Bond On Fluorescence Changes In Benzene Derivations And Different Acceptor Systems, Nursel Acar Bayri, Özgül Koçak

Turkish Journal of Chemistry

In this study, benzene derivatives of phenol and naphtol were selected as donor systems and mixed with dioxane and TEA (triethylamine), which were chosen as acceptors. H-bond formation in the phenol-triethylamine binary system was investigated by both UV absorption and emission spectroscopies. The changes in the absorption and emission spectra by H-bond formation and the equilibrium of the H-bonded complexes were studied at both the ground and excited states. In addition, equilibrium constants at different temperatures and thermodynamic properties related to equilibrium (enthalpy, fere energy change and entropy values of H-bond formation) were calculated. A shift to longer wavelengths and …


Determination Of Ponceau 4r And Tartrazine In Various Food Samples By Derivative Spectrophotometric Methods, Sedat Sayar, Yüksel Özdemi̇r Jan 1997

Determination Of Ponceau 4r And Tartrazine In Various Food Samples By Derivative Spectrophotometric Methods, Sedat Sayar, Yüksel Özdemi̇r

Turkish Journal of Chemistry

Derivative spectrophotometric methods were originally developed for determining Ponceau 4R and Tartrazine in order to resolve their binary mixtures. The method permits the simultaneous determinations of these food colorants in various food samples. Recovery by derivative methods was nearly 100 \%.


Thermodynamics Of Dissociation Of Strontium, Barium And Nickel Caproates In Water, Hüseyin Topallar, Yüksel Bayrak, Mehmet İşcan Jan 1997

Thermodynamics Of Dissociation Of Strontium, Barium And Nickel Caproates In Water, Hüseyin Topallar, Yüksel Bayrak, Mehmet İşcan

Turkish Journal of Chemistry

The critical micellar concentration (CMC) and thermodynamic parameters (heat \DeltaH_d, free energy \DeltaG_d, and entropy \DeltaS_d, of dissociation) of aqueous solutions of strontium, barium and nickel caproates were determined by conductivity measurements. A Kraus and Bray-type expression was used to evaluate molecular conductance at infinite dilution and theromdynamic parameters. The results confirm that CMC remains unaffected by temperature in the range of 25-55^{\circ}C, and show that the dissociation of soaps is an exothermic reaction and nonspontaneous.


Effect Of Various Additives On The Hydration Of Perlite-Gypsum Plaster And Perlite-Portland Cement Pastes, Emin Erdem Jan 1997

Effect Of Various Additives On The Hydration Of Perlite-Gypsum Plaster And Perlite-Portland Cement Pastes, Emin Erdem

Turkish Journal of Chemistry

Perlite is a volcanic glass which forms a light-weight cellular aggregate when ground and heated to about 1000\ci. It is used in the production of light-weight masonry blocks and concrete in the building industry as well as in insulation, fire protection, agriculture and pharmacology. In this study, the effects of admixtures such as lime, sodium citrate and various superplasticizers on the hydration of perlite-gypsum plaster, perlite-white Portland cement and perlite-blended Portland cement mixtures were investigated by measurement of flexural and compressive strengths and by DTA-TG. It was found that the addition of lime caused pozzolanic reactions and, consequently, increased strength …


The Synthesis Of Some Novel Chromans, M. Yalçinkaya, O. Bi̇lgi̇ç, S. Bi̇lgi̇ç Jan 1997

The Synthesis Of Some Novel Chromans, M. Yalçinkaya, O. Bi̇lgi̇ç, S. Bi̇lgi̇ç

Turkish Journal of Chemistry

The inverse-electron demanded Diels-Alder reaction of 1-N,N-dimethylaminomethyl-2-naphthol (1) with substituted styrenes were investigated. With 2-, 3-, 4-methylstyrenes, 2-(2'-,3'- and 4'-methylphenyl)-benzo-5,6-chromans (5, 6 and 7) were obtained in 12, 18 and 53 \% yields respectively. With 2-, 3- and 4-chlorostyrenes, 2-(2'-, 3'- and 4'-chlorophenyl)-benzo-5,6-chromans (8,9 and 10) were obtained in 8, 20 and 33 \% yields respectively. With 4-vinyl-pyridine, 2-($4'-pyridyl)-benzo-5,6-chroman (11) was obtained in 48\% yield. In all pyrolysis no quinone-methide dimer (4) was encountered.


Dielectric Studies Of Various Olefin/So2 Copolmers, B. Baysal, Candan Erbi̇l, Paul L. Morganelli, W. H. Stockmayer Jan 1997

Dielectric Studies Of Various Olefin/So2 Copolmers, B. Baysal, Candan Erbi̇l, Paul L. Morganelli, W. H. Stockmayer

Turkish Journal of Chemistry

Dielectric constant and loss have been measured at low and high frequencies for several poly(1-olefin sulfones) as well as for the polysulfones of allybenzene and allyl cyclopentane. The low-frequency dispersion in allylbenzene due to helical sequences is weaker in benzene than in dioxane, and in both solvents is much lower than for the 1-olefin polymers. Solvent effects on the high frequency process are also reported, but yield no simple uniform picture.


Some Remarks On Solid State Polymerization, George Adler Jan 1997

Some Remarks On Solid State Polymerization, George Adler

Turkish Journal of Chemistry

No abstract provided.


Synthesis Of The New Cation Exchange Resins Having Poly (Styrene-Caprolactone) Units, S. Savaşkan Yilmaz, Hulisi Özbayrak, Baki Hazer Jan 1997

Synthesis Of The New Cation Exchange Resins Having Poly (Styrene-Caprolactone) Units, S. Savaşkan Yilmaz, Hulisi Özbayrak, Baki Hazer

Turkish Journal of Chemistry

The crosslinked polystyrene-polycaprolactone , PS-PCL-, block copolymers were prepared by the copolymerization of styrene and poly(caprolacton dimethylmethacrylate) (PCL-DM). The molecular weights of polycaprolactone, PCL, PCL-DM were 1250 and 2000. The swelling in H_2O or CHCl_3 of the sulfonated and unsulfonated block copolymers were determined under comparable conditions and investigated. The capacities of the obtained ion exchange resins were 1.31 and 1.10 meq/g.


Thermal Stabilities Of Hydroxyalkyl Terminated Polydimethylsiloxane Oligomers, İskender Yi̇lgor, Emel Yi̇lgor Jan 1997

Thermal Stabilities Of Hydroxyalkyl Terminated Polydimethylsiloxane Oligomers, İskender Yi̇lgor, Emel Yi̇lgor

Turkish Journal of Chemistry

The thermal stabilities of \alpha,\omega-hydroxypropyl, \alpha,\omega-hydroxybutyl \alpha,\omega-2-hydroxypentyl and \alpha,\omega-hydroxyhexyl terminated polydimethylsiloxane oligomers were investigated. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating through the loss of functional end groups, as determined by FTIR spectroscopy and gel permeation chromatography. \alpha,\omega-Hydroxyhexyl and \alpha,\omega-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. The instability of the end groups is due to the backbiting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5-and 6-membered stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the …


New Synthetic Approach For The Synthesis Of Liquid Crystalline Block And Graft Copolymers, Yeşim Hepuzer, İ. Ersin Serhatli, Yusuf Yağci Jan 1997

New Synthetic Approach For The Synthesis Of Liquid Crystalline Block And Graft Copolymers, Yeşim Hepuzer, İ. Ersin Serhatli, Yusuf Yağci

Turkish Journal of Chemistry

Liquid crystalline block and graft copolymers were synthesized according to the macroinitiator and macroinimer concept. For this purpose, side chain block copolymers (polytetrahydrofuran-b-polymethylmethacrylate) having liquid crystalline 4,4'- cyanobiphenyl blocks were prepared and characterized. Unlike the liquid-crystalline homopolymer with mesogenic units in the side chain, all block and graft copolymers showed a smectic A mesophase. The transition temperatures are hardly affected by the composition and molecular weight of the blolck copolymers.


Conducting Polymer Grafts Of Polypyrrole, Levent Toppare Jan 1997

Conducting Polymer Grafts Of Polypyrrole, Levent Toppare

Turkish Journal of Chemistry

Conducting polymer grafts of pyrrole with poly[(methyl methacrylate)-co-(2-(N-pyrollyl) ethyl methacrylate)] wwere synthesized via elctrochemical polymerization of pyrrole in different media. Samples were characterized by SEM, thermal analysis and conductivity measurements.


Electrical Conductivities Of Poly (Alkyl Vinyl Ketones) Reacted With Dopant Solutions, Jun Hui Ma, J. David Tauber, Ülkü S. Ramelow Jan 1997

Electrical Conductivities Of Poly (Alkyl Vinyl Ketones) Reacted With Dopant Solutions, Jun Hui Ma, J. David Tauber, Ülkü S. Ramelow

Turkish Journal of Chemistry

Poly ethyl vinyl ketone (PEVK) and poly methyl vinyl ketone (PMVK) were prepared using photochemical processes. The irradiation of monomers with UV light provides a new method, different from the methods previously used for the polymerization of these monomers. FTIR and UV spectroscopies were used for the structure and reaction mechanism of the polymers. NMR was used to calculate the conversion percentage of MVK and EVK polymers. The conductivity change at various temperatures was traced during reactions of PMVK and PEVK with various dopant concentrations and the activation energy of these reactions were calculated by adding dopants and by adjusting …


A Two-Dimensional Monte Carlo Polymerization Of 5-Membered Rings, Okan Esentürk, H. Önder Pamuk, E. Yurtsever Jan 1997

A Two-Dimensional Monte Carlo Polymerization Of 5-Membered Rings, Okan Esentürk, H. Önder Pamuk, E. Yurtsever

Turkish Journal of Chemistry

A modification of the kinetic growth model in two dimensions for the polymerization of 5-membered rings is presented. The preliminary results reveal the validity of the modified model.


Calculation Of Spreading Pressure Of Water On Cellulosic Films From Contact Angle Data, H. Yıldırım Erbi̇l Jan 1997

Calculation Of Spreading Pressure Of Water On Cellulosic Films From Contact Angle Data, H. Yıldırım Erbi̇l

Turkish Journal of Chemistry

The correlations between the surface properties of the modified cellulose papers with their toner compatibility were investigated. The surface tension components of the cellulosic films, their interfacial tension with the liquid drops and the work of adhesion components were calculated using van Oss-Good's One-Liquid contact angle approach. The electron donor (or Lewis base) \gamma^- components of the cellulosic films were found to represent the main interactions with the the electron acceptor (acidic) \gamma^+ components of the contacting liquids. Allyl ketene dimer (AKD) grafting of the cellulose affected the surface properties; the higher the substitution of the hydroxyl group, the smaller …


A Quantum-Chemical Investigation On 5,5'-Bi(1h-1.2,4-Triazole)), A. A. İki̇zler, R. Abbasoğlu, N. Saltek, M. Şeri̇fova Jan 1997

A Quantum-Chemical Investigation On 5,5'-Bi(1h-1.2,4-Triazole)), A. A. İki̇zler, R. Abbasoğlu, N. Saltek, M. Şeri̇fova

Turkish Journal of Chemistry

The conformational analysis of flexible 5,5'-bi(1H-1,2,4-triazole) molecule containing various reaction centers has been performed by the semiempirical methods MNDO,AM1 and PM3, and the internal rotation barrier calculated. The most stable conformation of the molecule has been determined to be the planar trans conformation. According to the three methods, 5,5'-bi(1H-1,2,4-triazole) molecule (C) has been found to be relatively more stable than its tautomer 3,3'-bi(1H-1,2,4-triazole)(B) and to be less stable than its other tautomer 3,3'-bi(4H-1,2,4-triazole)(A). Moreover, the electronic properties of 5,5'-bi(1H-1,2,4-triazole) molecule and the effect of conformational changing on electronic and geometric properties have also been investigated. To determine the protonation sites …


High Rates Of Fluorescence Quenching Between Perylene Dodecyldiimide And Certain \Pi-Electron Donors, S. İçli̇, H. İci̇l, İ. Gürol Jan 1997

High Rates Of Fluorescence Quenching Between Perylene Dodecyldiimide And Certain \Pi-Electron Donors, S. İçli̇, H. İci̇l, İ. Gürol

Turkish Journal of Chemistry

Perylene bis-n-dodecyl diimide is found to quench fluorescenc emissions of naphthalene, phenanthrene and dihydrocarbazolocarbazole molecules at rates of 4.4\times10^{11}, 2.8\times10^{12} and 2.5\times10^4 M^{-1} sec^{-1}, in respective order of aromaticity. These unusulally high rates of fluorecence quenchings are attributed to Perrin model static quenching and presence of electron transfer through singlet excited state of perylene diimide. Calculated free energy of electron transfer, \Delta G_{ET}=-120.5 kJ/mol, between perylene diimide and dihydrocarbazolocarbazole is taken as evidence for observation of high fluorescence quenching rate for carbazolocarbazole molecule. Keywords: Fluorescence quenching, Photoenergy transfer, Perylene diimide and Carbazolocarbazole


Constituents Of Salvia Verticillata, Ufuk Sönmez, Gülaçtı Topçu, Ayhan Ulubelen Jan 1997

Constituents Of Salvia Verticillata, Ufuk Sönmez, Gülaçtı Topçu, Ayhan Ulubelen

Turkish Journal of Chemistry

Three new and fourteen known compounds were isolated from the roots of {\it Salvia verticillata L.} Spectral methods were used for the structure determination besides TLC comparisons with authentic samples for the known compounds.


The Reliability Of Jung-Biggs-Moorhead Method For Cholesterol Determination In The Presence Of Ergosterol, Lemi Türker, Şahinde Demi̇rci̇, Marjan Akdağ Jan 1997

The Reliability Of Jung-Biggs-Moorhead Method For Cholesterol Determination In The Presence Of Ergosterol, Lemi Türker, Şahinde Demi̇rci̇, Marjan Akdağ

Turkish Journal of Chemistry

In the present study, the reliability of Jung-Biggs-Moorhead method for cholesterol determination has been tested in the presence of another steroid, ergosterol. It was observed that presence of ergosterol interferes with the absorbance measurement of cholesterol. When both steroids are present in the sample maximum absorption wavelength are not shifted by the mutual interaction but absorbance values are changed considerably. Therefore this method may be used only for qualitative bu not quantitative analysis for cholesterol in the presence of ergosterol.