Subspeciation of nickel disulfide by carbon paste electrode voltammetry catalyzed by Ni2+

In subspeciation of sulfidic nickel, carbon paste electrode voltammetry was developed for the specific determination of Ni3S2 or NiS, but NiS2 was found to be unreactive. Ni2+ in pH 7.2 acetate solution was able to catalyze NiS2 to undergo redox reactions. The cyclic voltammogram showed two anodic peaks at -0.3 and +0.7 V and a cathodic peak at -0.6 V. The first anodic peak at -0.3 V and the cathodic peak were common among the three nickel sulfides, but the second anodic peak at +0.7 V was unique to NiS2. This peak current gave a linear dose response to NiS2 from 40 to 610 microg, with a correlation coefficient of 0.994, and a detection limit of 40 microg.     

Electron density distributions calculated for the nickel sulfides millerite, vaesite, and heazlewoodite and nickel metal: a case for the importance of ni-ni bond paths for electron transport

Bond paths and the bond critical point properties (the electron density (rho) and the Hessian of rho at the bond critical points (bcp's)) have been calculated for the bonded interactions comprising the nickel sulfide minerals millerite, NiS, vaesite, NiS(2), and heazlewoodite, Ni(3)S(2), and Ni metal. The experimental Ni-S bond lengths decrease linearly as the magnitudes of the properties each increases in value. Bond paths exist between the Ni atoms in heazlewoodite and millerite for the Ni-Ni separations that match the shortest separation in Ni metal, an indicator that the Ni atoms are bonded. The bcp properties of the bonded interactions in Ni metal are virtually the same as those in heazlewoodite and millerite. Ni-Ni bond paths are absent in vaesite where the Ni-Ni separations are 60% greater than those in Ni metal. The bcp properties for the Ni-Ni bonded interactions scatter along protractions of the Ni-S bond length-bcp property trends, suggesting that the two bonded interactions have similar characteristics. Ni-Ni bond paths radiate throughout Ni metal and the metallic heazlewoodite structures as continuous networks whereas the Ni-Ni paths in millerite, a p,d-metal displaying ionic and covalent features, are restricted to isolated Ni(3) rings. Electron transport in Ni metal and heazlewoodite is pictured as occurring along the bond paths, which behave as networks of atomic size wires that radiate in a contiguous circuit throughout the two structures. Unlike heazlewoodite, the electron transport in millerite is pictured as involving a cooperative hopping of the d-orbital electrons from the Ni(3) rings comprising Ni(3)S(9) clusters to Ni(3) rings in adjacent clusters via the p-orbitals on the interconnecting S atoms. Vaesite, an insulator at low temperatures and a doped semiconductor at higher temperatures, lacks Ni-Ni bond paths. The net charges conferred on the Ni and S atoms are about a quarter of their nominal charges for the atoms in millerite and vaesite with the net charge on Ni increasing with increasing Ni-S bond length. Reduced net charges are observed on the Ni atoms in heazlewoodite and are related to its Ni-Ni metal bonded interactions and to the greater covalent character of its bonds. Local energy density and bond critical point properties of the electron density distributions indicate that the Ni-S and Ni-Ni bonded interactions are intermediate in character between ionic and covalent.     

Electronic and vibrational properties of nickel sulfides from first principles

We report the results of first-principles calculations (generalized gradient approximation-Perdew Wang 1991) on the electronic and vibrational properties of several nickel sulfides that are observed on Ni-based anodes in solid oxide fuel cells (SOFCs) upon exposure to H2S contaminated fuels: heazlewoodite Ni3S2, millerite NiS, polydymite Ni3S4, and pyrite NiS2. The optimized lattice parameters of these sulfides are within 1% of the values determined from x-ray diffraction. The electronic structure analysis indicates that all Ni-S bonds are strongly covalent. Furthermore, it is found that the nickel d orbitals shift downward in energy, whereas the sulfur p orbitals shift upward with increasing sulfur content; this is consistent with the decrease in conductivity and catalytic activity of sulfur-contaminated Ni-based electrodes (or degradation in SOFC performance). In addition, we systematically analyze the classifications of the vibrational modes at the point from the crystal symmetry and calculate the corresponding vibrational frequencies from the optimized lattice constants. This information is vital to the identification with in situ vibrational spectroscopy of the nickel sulfides formed on Ni-based electrodes under the conditions for SOFC operation. Finally, the effect of thermal expansion on frequency calculations for the Ni3S2 system is also briefly examined.     

Synthesis of nickel sulfides in aqueous solutions using sodium dithionite

Reaction of nickel chloride with sodium dithionite in aqueous solutions at ambient temperature has been investigated systematically to obtain nickel sulfides. The products are characterized by X-ray diffraction, thermogravimetric analysis, and electrical resistivity and magnetic susceptibility measurements. It is found that the compositions and structures of the products are controlled by the reaction pH and the amount of the reactants. While reactions under highly acidic (pH < or = 2) and basic (pH > or = 7) conditions yield crystalline sulfur and amorphous or poorly crystalline NiySx, respectively, those at intermediate 3 < or = pH < or = 6 give crystalline NiySx. Both crystalline Ni3S2 (heazlewoodite structure) and Ni3S4 (spinel structure) have been obtained at room temperature. Additionally, NiS (millerite structure) is obtained by carefully heating Ni3S4 at 200 degrees C in a mixture of 90% Ar and 10% H2. Ni3S4 is found to be metastable, and it begins to disproportionate above 100 degrees C. Both Ni3S2 and Ni3S4 show metallic behavior. While Ni3S2 exhibits temperature-independent magnetic susceptibility, Ni3S4 shows ferrimagnetic ordering below 20 K.     

New low-temperature preparations of some simple and mixed co and ni dispersed sulfides and their chemical behavior in reducing atmosphere

A series of simple (CoS(2), Co(9)S(8), NiS(2), NiS, Ni(3)S(2)) and mixed sulfides (NiCo(2)S(4), Ni(0.33)Co(0.67)S(2), Ni(3)Co(6)S(8), CuCo(2)S(4), Cu(0.33)Co(0.67)S(2)) was prepared using low-temperature procedures. To obtain the mixed sulfides, the mixtures of the solutions of the corresponding salts were precipitated by Na(2)S and then heated in a sulfiding atmosphere at 300 degrees C. It has been found that the product phase composition depends on the sulfiding atmosphere. Using a H(2)S/Ar mixture leads to pyrite type sulfides, whereas treatment in H(2)S/H(2) flow allowed the preparation of Ni-Co and Cu-Co thiospinels. The as prepared highly dispersed single-phase materials were characterized by X-ray powder diffraction, scanning electron microscopy, temperature-programmed reduction (TPR), elemental analysis, and BET surface area measurements.     

CRYSTAL STRUCTURE OF ADDUCT OF BIS(O,O''''-DIBUTYLDITHIOPHOSPHATO)-NICKEL (II) WITH BIPYRIDYL

<正> Ni[(C8H9O)2PS2]2 bipy, Mr=697.57, triclinic, Ci-Pl, a=9.469(1)A, b=14.638(3)A, c=14.637(2)A, α=69.64(1)° , β=71.16(1)°, r=89.99(1)°, V= 1785.6A3, Z=2, Dc=1.297g.cm-3, Mo kα radiation, λ=0.71073A, F(000)=736e, R=0.081 for 4986 independent reflections. Ni(II) is coordinated by four sulfur atoms and two nitrogen atoms to form a distorted octahedron. The angles between each two among planes N2Ni, NiS(11)S(12) and NiS(21)S(22) are nearly 90°.     

Flow injection-pulse amperometric detection of ephedrine at a cobalt phthalocyanine modified carbon paste electrode

Direct detection of ephedrines and other underivatized amino compounds (amines, alicyclic amines, alkanolamines, and amino acids) can be carried out via electrocatalytic oxidation at a carbon paste electrode (CPE) modified with cobalt phthalocyanine (CoPC) in alkaline solution (0.10 mol L-1 NaOH). Most of the amino compounds tested could be determined using the CoPC/CPE in an amperometric flow detector. The analytical signal of ephedrine was stabilised by alternating the potential between an anodic detection potential of +0.30 V (+0.45 V for other amino compounds) applied for 220 ms and a cathodic reactivation potential of -0.30 V applied for 100 ms (potentials versus SCE). The linear response range for ephedrine was within 1-100 mumol L-1 and the detection limit was 0.8 mumol L-1 with a 100 microL sample loop and a typical sampling ra 60 h-1. The signal (oxidation peak current) reproducibility was 2-3%. The method was applied to the determination of ephedrine in pharmaceutical formulations with results comparable to those obtained with a standard spectrophotometric method.     

Combined theoretical and experimental analysis of the bonding in the heterobimetallic cubane-type Mo(3)NiS(4) and Mo(3)CuS(4) core clusters

X-ray structural data for the cubane-type clusters [Mo3CuS4(dmpe)3Cl4](+) and Mo3NiS4(dmpe)3Cl4 (dmpe = 1,2-bis(dimethylphosphino)ethane) with 16 metal electrons have been compared with optimized structural parameters calculated using "ab initio" methodologies. Compound Mo3NiS4(dmpe)3Cl4 crystallizes in the cubic noncentrosymmetric space group P213 with a Mo-Ni distance of 2.647 Angstrom, that is 0.2 Angstrom shorter than the Mo-Cu bond length in the isoelectronic copper cluster. The best agreement between theory and experiments has been obtained using the B3P86 method. In order to validate the B3P86 results, accurate infrared and Raman spectra have been acquired and the vibrational modes associated to the cubane-type Mo3M'S4 (M' = Cu or Ni) unit have been assigned theoretically. The electronic changes taking place when incorporating the M' into the Mo3S4 unit have been analyzed from a theoretical and experimental perspective. The bond dissociation energies between M'-Cl and Mo3S4 fragments show that formation of [Mo3CuS4(dmpe)3Cl4](+) is 135 kcal/mol energetically less favorable than the Ni incorporation. The more robust nature of the Mo3NiS4 fragment has been confirmed by mass spectrometry. The X-ray photoelectron spectroscopy (XPS) spectra of the trimetallic and tetrametallic complexes have been measured and the obtained binding energies compared with the computed electronic populations based on topological approaches of the electron localization function (ELF). The energies and shapes of the Cu 2p and Ni 2p lines indicate formal oxidation states of Cu(I) and Ni(II). However, the reductive addition of nickel into [Mo3S4(dmpe)3Cl3](+) causes a small decrease in the Mo 3d binding energies. This fact prevents an unambiguous assignment of an oxidation state in a conventional way, a circumstance that has been analyzed through the covariance of the electronic populations associated to the C(M') core and V(Mo3Ni) and V(S(2)') valence basins where Mo3NiS4 is a particularly electronically delocalized chemical entity.     

Spectrophotometric determination of tungsten with thiocyanate

The yellow W(V) thiocyanate complex is formed by shaking sodium tungstate solution in 0.2-0.8M potassium thiocyanate and 4-5M hydrochloric acid, with mercury. It is extracted with 2% tribenzylamine solution in chloroform and measured at 410 nm. U, Ti, V, Cr, Fe, Co, Ni, Mn, Al, Pb, Sn, Bi, Pd, Sb and Cu do not interfere. Pt and Mo in amount equal to that of tungsten give errors of up to 0.4 and 2% respectively. The sensitivity is 0.013 mug ml and Beer's law is obeyed up to 24 mug ml .     

Carbon paste electrode for trace zirconium(IV) determination by adsorption voltammetry.

A very sensitive and selective procedure was developed for trace measurement of zirconium based on the cathodic adsorptive stripping voltammetry of the zirconium-alizarin red S(ARS) complex at a carbon paste electrode (CPE). The 2nd-order derivative linear scan voltammograms of the zirconium-ARS complex were recorded by a model JP-303 polarographic analyzer from 0.0 to -1.0 V (vs. SCE). Optimal analytical conditions were found to be: an acetic acid (0.1 mol l(-1))-potassium biphthalate (0.08 mol l(-1)) buffer solution (pH 4.8) containing 4.0 x 10-6 mol l(-1) ARS; accumulation potential, 0.0 V; accumulation time, 180 or 90 s; rest time, 10 s; scan rate, 250 mV s(-1). The results showed that the complex can be adsorbed on the surface of the CPE, yielding one peak at -0.51 V, corresponding to the reduction of ARS in the complex at the electrode. The detection limit was found to be 1.0 x 10(-10) mol l(-1) (S/N = 3) for 240 s accumulation. The linear range was 2.0 x 10(-10)-4.0 x 10(-7) mol l(-1). The developed method was applied to the determination of trace zirconium in the ore samples with satisfactory results.     

Simultaneous kinetic spectrophotometric determination of vanadium(V) and iron(III)

Vanadium(V) and iron(III) can be determined simultaneously at pH 2 and 25 degrees C by a single experiment using their kinetic effect on the oxidation of indigo carmine by bromate which goes through an induction period and then decreases in absorbance, at lambda(max), 612 nm. The rate of the color-fading of indigo carmine is proportional to the concentration of vanadium and is independent of the concentration of iron. The length of the induction period of the reaction is related to the concentration of iron and is independent of the concentration of vanadium. Concentrations of 0.3-2 (mug ml(-1)) vanadium(V) and 6-12 (mug ml(-1)) iron(III) were determined with mean relative errors of 2.7 and 1.6%, respectively. The interference effects of various cations and anions on determination of mixtures of vanadium and iron is reported. Application of the method to real samples and several mixtures of standard solutions are performed which gave acceptable results.     

Simultaneous spectrophotometric determination of Fe and Ni with xylenol orange using principal component analysis and artificial neural networks in some industrial samples

Artificial neural networks (ANNs) are among the most popular techniques for nonlinear multivariate calibration in complicated mixtures using spectrophotometric data. In this study, Fe and Ni were simultaneously determined in aqueous medium with xylenol orange (XO) at pH 4.0. In this way, after reducing the number of spectral data using principal component analysis (PCA), an artificial neural network consisting of three layers of nodes was trained by applying a back-propagation learning rule. Sigmoid transfer functions were used in the hidden and output layers to facilitate nonlinear calibration. Adjustable experimental and network parameters were optimized, 30 calibration and 20 prediction samples were prepared over the concentration ranges of 0-400 mug l(-1) Fe and 0-300 mug l(-1) Ni. The resulting R.S.E. of prediction (S.E.P.) of 3.8 and 4.7% for Fe and Ni were obtained, respectively. The method has been applied to the spectrophotometric determination of Fe and Ni in synthetic samples, some Ni alloys, and some industrial waste waters.     

Determination of nickel by anodic adsorptive stripping voltammetry with a cation exchanger-modified carbon paste electrode

The behavior of a modified carbon paste electrode (CPE) for nickel determination by anodic adsorptive stripping voltammetry (AAdsSV) was studied. The electrode was built incorporating the Dowex 50W x 12 (H(+) form) ion exchanger to a Nujol-graphite base paste. Ni(2+) was preconcentrated on the electrode surface in open circuit conditions, with the reduction (-1300 mV)/reoxidation step carried out in HCl solution (pH 3). During deposition time (5 min), the hydrogen evolution did not present obstacle in the quantification of nickel. For 12 min of accumulation and 5 min of deposition, nickel can be quantified up to 600 mug l(-1). The detection limit was 0.005 mug l(-1) at a linear potential scan rate of 200 mV s(-1). Interferences from Hg(2+) and Ag(2+) up to a concentration of 1 and 0.6 mg l(-1), respectively, were eliminated with the aid of the anion exchanger Dowex-2 (mesh 200-400) which was added to the sample in the preconcentration step. The tolerance for some metal ions such as Cu(2+), Cd(2+), Fe(3+), Zn(2+), Co(2+) and Pb(2+) was improved in the same way. The method was applied for the determination of nickel in samples of tap and mineral water. At the concentration level of 50 mug l(-1) of Ni (2+), the results were in good agreement with those obtained using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). For a Ni(2+) concentration of 5 mug l(-1), the results obtained showed better accuracy than those obtained by ICP-AES.     

Ligand Substitution Reactions at the Nickel of [Mo(3)NiS(4)(H(2)O)(10)](4+) with Two Water Soluble Phosphines, CO, Br(-), I(-), and NCS(-) and the Inertness of the 1,4,7-Triazacyclononane (L) Complex [Mo(3)(NiL)S(4)(H(2)O)(9)](4+)

Comparisons (25 degrees C) are made of substitution reactions, X replacing H(2)O, at the tetrahedral Ni of the heterometallic sulfido cuboidal cluster [Mo(3)NiS(4)(H(2)O)(10)](4+), I = 2.00 M (LiClO(4)). Stopped-flow formation rate constants (k(f)/M(-)(1) s(-)(1)) for six X reagents, including two water soluble air-stable phosphines, 1,3,5-triaza-7-phosphaadamantane PTA (119) and tris(3-sulfonatophenyl)phosphine TPPTS(3)(-) (58), and CO (0.66), Br(-) (14.6), I(-) (32.3), and NCS(-) (44) are reported alongside the previous value for Cl(-) (9.4). A dependence on [H(+)] is observed with PTA, which gives an unreactive form confirmed by NMR as N-protonated PTA (acid dissociation constant K(a) = 0.61 M), but in no other cases with [H(+)] in the range 0.30-2.00 M. The narrow spread of rate constants for all but the CO reaction is consistent with an I(d) dissociative interchange mechanism. In addition NMR studies with H(2)(17)O enriched solvent are too slow for direct determination of the water-exchange rate constant indicating a value <10(3) s(-)(1). Equilibrium constants/M(-)(1) for 1:1 complexing with the different X groups at the Ni are obtained for PTA (2040) and TPPTS(3)(-) (8900) by direct spectrophotometry and from kinetic studies (k(f)/k(b)) for Cl(-) (97), Br(-) (150), NCS(-) (690), and CO (5150). No NCS(-) substitution at the Ni is observed in the case of the heterometallic cube [Mo(3)Ni(L)S(4)(H(2)O)(9)](4+), with tridentate 1,4,7-triazacyclononane(L) coordinated to the Ni. Substitution of NCS(-) for H(2)O, at the Mo's of [Mo(3)NiS(4)(H(2)O)(10)](4+) and [Mo(3)(NiL)S(4)(H(2)O)(9)](4+) are much slower secondary processes, with k(f) = 2.7 x 10(-)(4) M(-)(1) s(-)(1) and 0.94 x 10(-)(4) M(-)(1) s(-)(1) respectively. No substitution of H(2)O by TPPTS(3)(-) or CO is observed over approximately 1h at either metal on [Mo(3)FeS(4)(H(2)O)(10)](4+), on [Mo(4)S(4)(H(2)O)(12)](5+) or [Mo(3)S(4)(H(2)O)(9)](4+).     

2-pyrrolylthiones as monoanionic bidentate N,S-chelators: synthesis and molecular structure of 2-pyrrolylthionato complexes of nickel(II), cobalt(III), and mercury(II)

The metal-chelating ability of 2-pyrrolylthiones is described. The readily available ligands di-2-pyrrolyl thione (6), 2-thioacetylpyrrole (10), and 2-thiobenzoylpyrrole (11) constitute examples of monoanionic ligands with N,S-donor atom sets, although di-2-pyrrolyl thione (6) could theoretically also achieve chelation through an N,N-donor set. A square planar Ni(II) complex, 14, an octahedral Co(III) complex, 18, and a tetrahedral Hg(II) complex, 17, with the di-2-pyrrolyl thionato chelate have been prepared, and their structures have been characterized by 1H NMR, UV-vis, MS, IR, elemental analysis, and single-crystal X-ray diffraction. Crystal data for 14: C18H14N4NiS2.0.28H2O, trigonal, R3, a = 18.467(1) A, b = 18.467(1) A, c = 26.404(2) A, V = 7797(1) A3; Z = 18, R = 3.2%. Crystal data for 18-mer: C27H21CoN6S3.C3H6O (acetone), monoclinic, P21/n, a = 9.569(1) A, b = 23.152(1) A, c = 13.659(1) A, beta = 100.882(8) degrees, V = 2971.6(5) A3, Z = 4, R = 4.3%. Crystal data for 17: C18H14HgN4S2, triclinic, P1, a = 8.443(2), b = 14.278(1) A, c = 7.445(1) A, alpha = 90.561(9) degrees, beta = 97.64(1) degrees, gamma = 104.250(9) degrees, V = 861.3(2) A3, Z = 2, R = 4.2%. The bond lengths and angles of these metal complexes are comparable to those of known N,S-chelates. A comparison of the structural parameters of the ligand in the metal complexes with those for the free ligand 6 demonstrates the preorganization of the free ligand for complexation and demonstrates the spectator role of the noncoordinating pyrrolic unit. Chelation of Ni(II) by 2-thioacetylpyrrole (10) and 2-thiobenzoylpyrrole (11) to provide complexes 12 and 13 with structures analogous to complex 14 is also described.     

Influence of the coordination mode in [Ni{RC(S)NP(S)(OiPr)2}2] for the formation of nickel-containing nanoparticles

The complex [Ni{2-PyNHC(S)NP(S)(OiPr)(2)-1,5,7-N,N',S}(2)] ([NiL(I)(2)]) dissolved in tri-n-octylphosphine (TOP) is decomposed in hot hexadecylamine (HDA) to give TOP-capped Ni nanoparticles. The same procedure using [Ni{2-MeC(6)H(4)NHC(S)NP(S)(OiPr)(2)}(2)-1,3-N,S] ([NiL(II)(2)]) and [Ni{PhC(S)NP(S)(OiPr)(2)-1,5-S,S'}(2)] ([NiL(III)(2)]) leads to the formation of NiS nanoparticles with the rhombohedral and hexagonal structures, respectively. NiH(x) nanoparticles were also produced from a mixture of [NiL(I)(2)] and N(2)H(4). The obtained Ni nanoparticles can be used for the catalytic addition of Ph(2)S(2) to 1-, 2- and 3-hexynes.     

碳糊电极阴极吸附伏安法测定橙皮甙

在0.4mol/L的NH4Cl-NH3(pH9.0)缓冲液中,使用JP-303极谱分析仪,橙皮甙在碳糊电极(CPE)上有一灵敏的吸附伏安还原峰,峰电位为-1.2V(vs.SCE).该还原峰的二阶导数峰电流与橙皮甙的浓度在2.0×10-8～1.0×10-6mol/L(富集90s)范围内成良好的线性关系,相关系数为0.9963,检出限为1.0×10-8mol/L(S/N=3,富集110s).探讨了橙皮甙在碳糊电极上的伏安性质和电极反应机理,并且成功应用于中草药桔皮中橙皮甙含量的测定.     

Simultaneous determination of sulphide and sulphite by gas-phase molecular absorption spectrometry. Comparative study of different calculation methods

A method for the simultaneous determination of sulphide and sulphite is described, which involves continuous H(2)S and SO(2) generation, preconcentration in a liquid nitrogen trap and measurement of the molecular absorption spectra of volatiles in the gas phase in 190-220 nm range. Under the recommended conditions (sample flow: 50 ml/min and concentrated sulphuric acid flow: 12 ml/min; generation time: 4 min) linear response ranges from 0.05 mug/ml for S(2-) and 0.20 mug/ml SO(2-)(3) are obtained with detection limits of 0.05 and 0.20 mug/ml respectively. Synthetic mixtures of the two components have been solved and a comparative study of different calculation methods has been made. In conclusion, multiwavelength methods offer better precision and accuracy.     

碱性电镀光亮锌镍合金研究

在总结镀液的电化学特性和锌镍合金镀层的晶体结构与性能等实验结果的基础上,提出碱性电镀光亮锌镍合金的工艺规范和直接把锌酸盐镀锌液转化为碱性电镀光亮锌镍合金镀液的方法。生产实践证明,该工艺稳定,镀层光亮、耐腐性好、硬度较高、无氢脆,镍含量可在９～２０ｗｔ％范围内随意控制。     

Reversed-phase high performance liquid chromatographic method for the determination of lansoprazole, omeprazole and pantoprazole sodium sesquihydrate in presence of their Acid-induced degradation products

A simple sensitive, selective and accurate reversed-phase high performance liquid chromatographic method was developed and validated for the quantitative determination of lansoprazole, omeprazole and pantoprazole sodium sesquishydrate in the presence of their acid-induced degradation products. The three compounds were monitored at 280 nm using Nova-Pak C(18) column and a mobile phase consisting of 0.05 M potassium dihydrogen phosphate : methanol : acetonitrile (5 : 3 : 2 v/v/v). Linearity ranges were 2-20 mug ml(-1), 2-36 mug ml(-1) and 0.5-20 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The corresponding recoveries were 100.61+/-0.84%, 100.50+/-0.80% and 99.78+/-0.88%. The minimum detection limits were 0.55, 0.54 and 0.03 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The method could be successfully applied to the determination of pure, laboratory prepared mixtures and pharmaceutical dosage forms. The results obtained were compared with the reported methods for lansoprazole and pantoprazole or the official U.S.P method for omeprazole.