Diazocoupling reaction for the spectrophotometric determination of physiologically active catecholamines in bulk and pharmaceutical preparations

A simple and sensitive spectrophotometric method for the determination of four catecholamines viz., adrenaline bitartarate (ABT), methyldopa (MDP), dopamine hydrochloride (DPH), and levodopa (LDP), in both pure form and in pharmaceutical formulations is described. The method is based on the reaction of diazotized sulphanillic acid (DSA) with catecholamines in a basic medium to yield orange-red colored products having absorption maxima at 507 nm for MDP and at 475 nm for others analytes. The colored species obeyed Beer’s law in the range of 1–27, 0.5–17, 0.6–15, and 1.5–19.2 μg/mL for ABT, MDP, DPH, and LDP, respectively. The molar absorptivity values as obtained from Beer’s law data were found to be 0.812 × 10⁴, 0.947 × 10⁴, 0.927 × 10⁴, and 0.709 × 10⁴ L/(mol cm), while Sandell’s sensitivity values were observed to be 412.03, 25.15, 20.44, and 27.81 ng/cm² for ABT, MDP, DPH, and LDP, respectively. Common excipients did not interfere with the proposed method. The results of the proposed methods compare favorably with those of official methods. The proposed method offers a simplicity, reliability, rapidity, and accuracy compared to the existing methods. The text was submitted by the author in English.     

Triphenyltetrazolium chloride as a new analytical reagent for molybdenum(VI): Application to plant analysis

Solvent extraction of molybdenum(VI) ion associate with triphenyltetrazolium chloride (TTC) has been studied. TTC was proposed as reagent for the spectrophotometric determination of micro amounts of molybdenum(VI) at λ_max 250 nm. The optimum conditions for extraction of molybdenum(VI) as an ionassociation complex with TTC has been determined. Beer’s law is obeyed in the range of 0.5–10 μg/mL molybdenum(VI). The molar absorptivity of the ion-pair is 1 × 10⁶ L/mol cm. The sensitivity of the method is 9.6 × 10⁻⁵ μg/cm². The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase are: distribution constant K _D = 32.64, extraction constant K _ex = 2.19 × 10¹⁰ association constant β = 6.71 × 10⁸. The interferences of different cations, anions on molybdenum(VI) determination were also investigated. A sensitive and selective method for the determination of microquantities of molybdenum(VI) has been developed. The determination was carried out without preliminary separation of molybdenum. A novel procedure of molybdenum(VI) extraction and spectrophotometric determination in different plant samples was examined.     

Spectrophotometric determination of nickel in biological samples using 1-azobenzene-3-(3-hydroxyl-2-pyridyl)-triazene

A new sensitive and selective chromogenic reagent, 1-azobenzene-3-(3-hydroxyl-2-pyridyl)-triazene (ABHPT), was synthesized. It has been found that ABHPT reacts with nickel(II) in a borax buffer solution (pH 10.0) to form 2: 1 red complexes with the maximum absorption at 530 nm. The apparent molar absorptivity of the complex is 2.6 × 10⁵ L/(mol cm). Most metal ions can be tolerated in considerable amounts, whereby only zinc and mercury may interfere with the determination of nickel(II). Nevertheless, this can be easily eliminated by prior separation with sulfhydryl dextran gel. A new method for the spectrophotometric determination of trace nickel(II) was developed. Beer’s law is obeyed for 0–15 μg of nickel(II) in 25 mL of solution. The limit of quantification, limit of detection, and relative standard deviation are 0.74 ng/mL, 0.25 ng/mL, and 1.0%, respectively. The method has been applied to the determination of trace nickel(II) in biological samples with satisfactory results. The text was submitted by the authors in English.     

Adsorptive Voltammetric Measurement of Trace Level of Iron(III) with 4–(2–Pyridylazo) Resorcin

Abstract

The polarographic behavior of the complex of iron–4– (2–pyridylazo) resorcin(PAR) was studied. In HAc– NaAc– EDTA buffer solution, the complex can be adsorped on a hanging mercury drop electrode giving a sensitive adsorptive complex reduction peak with a peak potential at -0.36V(vs. SCE). Optimum experimental conditions were found by the use of 0.08mol/L HAc, 0.06mol/L NaAc, 5.0 × 10^?3mol/L EDTA and 1.0 × 10^?5mol/L PAR. With preconcentration for 60s, the derivative peak height of the complex compound is linearly proportional to the concentration for Fe in the range from 1.0 × 10^?9mol/L to 1.0 × 10^?7mol/L. For a 2–min pre–concentration time, the detection limit found was 2.0 × 10^?10mol/L. This method has high sensitivity and selectivity. It has been applied to the determination of trace iron in food and water samples without any pre–separation step.     

Flow injection spectrofluorimetric determination of iron(III) in water using salicylic acid

A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed. Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used was 2 × 10⁻⁶ mol L⁻¹ salicylic acid in 0.1 mol L⁻¹ NH₄⁺/NH₃ buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L⁻¹ iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection was 0.3 μg L⁻¹ and the sampling rate was 60 h⁻¹. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully applied to the determination of low levels of iron in real samples (river, sea, and spring waters).     

A novel method for the determination of tiopronin by using potassium ferricyanide as spectroscopic probe reagent in pharmaceutical and urine samples

In this paper, a novel method has been established to determine tiopronin using potassium ferricyanide as spectroscopic probe reagent. It has been demonstrated that Fe(III) is reduced to Fe(II) by tiopronin, and the in situ formed Fe(II) reacts with potassium ferricyanide to form soluble Prussian blue. Beer’s law is obeyed in the range of tiopronin concentration of 0.040–9.00 μg/mL at the maximal absorption wavelength of 735 nm. The linear regression equation is A = 0.0153 + 0.1605c (μg/mL) with a correlation coefficient of 0.9997 and the apparent molar absorption coefficient of 2.6 × 10⁴ L/mol cm. The detection limit is 0.030 μg/mL and RSD is 1.3%. The parameters with regard to determination have been optimized and the reaction mechanism has been discussed. This method has been successfully applied to determine tiopronin in pharmaceutical and urine samples with satisfactory results.     

Spectrophotometric determination of trace cadmium in vegetables with 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid

A new highly sensitive and selective chromogenic reagent, 3,5-bis(4-phenylazophenylaminodiazo)benzoic acid (BPPABA) has been synthesized and applied to the determination of trace cadmium(II) in vegetables. The method is based on the color reaction between BPPABA and cadmium (II). In the presence of Triton X-100, cadmium(II) reacts with BPPABA in Na₂B₄O₇-NaOH buffer solution (pH 10.5), forming red complex with maximum absorption at 530 nm. Under the optimal conditions, Beer’s law is obeyed within 0–12 μg of cadmium within 25 mL of solution, and the apparent molar absorptive coefficient of the complex is 2.8 × 10⁵ L/mol cm. The detection limit and the relative standard deviation were found to be 0.92 μg/L and 1.0%, respectively. Interference of foreign ions was also investigated. Most of the metal ions are tolerated in considerable amounts except for Hg(II), Cu(II) and Ni(II). To eliminate the interference of foreign ions, metal ion imprinted polymer technique was utilized.     

Highly sensitive spectrophotometric determination of olanzapine using cerium(IV) and iron(II) complexes of 1,10-phenanthroline and 2,2′-bipyridyl

Two highly sensitive spectrophotometric methods have been developed for the determination of olanzapine (OLP) in pharmaceuticals using cerium(IV) and iron(II) complexes of 1,10-phenanthroline and 2,2′-bipyridyl as reagents. The methods are based on the oxidation of OLP in acidic medium by a known excess of cerium(IV) followed by the determination of the unreacted oxidant by reacting with either ferroin and measuring the absorbance at 510 nm (method A) or iron(II)-2,2′-bipyridyl complex and measuring the absorbance at 525 nm (method B). The amount of cerium(IV) reacted corresponds to the amount of OLP. In both the methods, the absorbance is found to increase linearly with OLP concentration as shown by the correlation coefficient (r) of 0.9980 and 0.9958 for method A and method B, respectively. The calibration graphs are linear over the concentration range of 0.2–2.0 μg/mL in both the methods. The calculated molar absorptivity values are 1.00 × 10⁶ and 7.03 × 10⁵ L/mol cm, for method A and method B. The LOD and LOQ values for method A are calculated to be 0.04 and 0.13 μg/mL and the values are 0.07 and 0.22 μg/mL for method B, respectively. The methods were validated as per the current ICH guidelines. Both the methods gave similar results in terms of accuracy and precision. The RSD was less than 3% and the accuracy, obtained from recovery experiments, was 98.76–101.4%. The methods developed were applied to the determination of OLP in tablets and results agreed well with the label claim.     

Fluorescent microscopic determination of gatifloxacin in milk,injection, human urine,and rabbit serum samples by self-ordered ring technique on glass slides support

A simple and sensitive self-ordered ring (SOR) technique, which was based on the capillary effect of solvent on a hydrophobic glass slide, was successfully applied to the determination of gatifloxacin in milk, injection, human urine and rabbit serum samples. In a medium of pH 3.20 (HAc-NaAc) with the aid of poly(vinyl alcohol)-124 (PVA-124), when 0.50 μL aluminum-sensitized gatifloxacin was dropped on glass slide with dimethyl dichlorosilane (DMCS) pretreated, a typical fluorescent SOR with diameter (2R) of the ring less than ca. 1.77 mm and the belt width (2δ) less than 29.3 μm can be obtained. The solute on the ring belt had strong fluorescence. Data of the imaged SOR showed that the gatifloxacin molecule across the SOR belt section follows a Gaussian distribution. The assay showed that when the droplet volume is 0.1 μL, the SOR method could be used to determine gatifloxacin in the range of 5.61 × 10⁻¹⁴ ∼ 1.50 × 10⁻¹² mol/ring (5.61 × 10⁻⁸∼1.50 × 10⁻⁵ M) and the limit of determination (LOD) reached 5.61 × 10⁻¹⁵ mol/ring (5.61 × 10⁻⁸ M) with three-fold signal-to-noise ratio (S/N = 3).     

Determination of EDTA in used fixing solutions by capillary electrophoresis

A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm × 75 μm I.D.) filled with a borate buffer (50 mmol L^–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved is 2 × 10^–6 mol L^–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions. Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998     

Determination of EDTA in used fixing solutions by capillary electrophoresis

A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm × 75 μm I.D.) filled with a borate buffer (50 mmol L^–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved is 2 × 10^–6 mol L^–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions. Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998     

Spectrophotometric determination of total inorganic arsenic with hexamethylene ammonium-hexamethylenedithiocarbamate in nonionic triton X-100 micellar media

We have developed a cost-effective and sensitive spectrophotometric method for the determination of arsenic at trace level using a new reagent, hexamethylene ammonium-hexamethylenedithiocarbamate (HMA-HMDTC). Here we show that arsenic reacts with HMA-HMDTC in acidic conditions to yield the As(HMDTC)₃ complex. We studied the Beer’s law at 256 nm, which showed linearity over the concentration range 0.2–1.0 μg/mL of arsenic. We have shown that molar absorptivity, Sandell’s sensitivity and the detection limit of the method are 6.06 × 10⁴ L/mol cm, 0.0012 μg/cm² and 0.060 μg/mL, respectively. We have applied this new method to the determination of arsenic in drinking water.     

Organic solvent-soluble membrane filters for the preconcentration and spectrophotometric determination of iron(II) traces in water with Ferrozine

An organic solvent-soluble membrane filter (MF) is proposed for the simple and rapid reconcentration with subsequent spectrophotometric determination of trace levels of iron (II) in water. Iron (II) is collected on a nitrocellulose membrane filter as ion associate of an anionic complex, which is formed by iron (II) and Ferrozine and a cation-surfactant. The ion-pair compound and the MF can be dissolved in small volumes of 2-ethoxyethanol and the absorbance of the resulting solution is measured at 560 nm against a reagent blank with molar absorptivity of 4.01 × 10⁴ L mol^–1 cm^–1. Beer’s law is obeyed over the concentration range 0–10 μg L^–1 of iron (II) in water and the detection limit is 0.03 μg L^–1 with a 50-fold enrichment factor. The proposed method can satisfactorily be applied to the determination of iron (II) in natural water and sea water. Received: 23 June 1998 / Revised: 21 July 1998 / Accepted: 25 August 1998     

Simple UV and visible spectrophotometric methods for the determination of doxycycline hyclate in pharmaceuticals

Doxycycline hyclate (DOX), a broad spectrum antibiotic with activity against a wide range of gram-positive and gram-negative bacteria, is widely used as a pharmacological agent and as an effector molecule in inducible gene expression system. Three simple, selective, rapid, accurate, precise and cost-effective spectrophotometric methods for the determination of DOX in bulk drug and in tablets have been developed and validated. First method (method A) is based on the measurement of absorbance of DOX in 0.1 M HCl at 240 nm. The second method (method B) is based on the measurement of yellow chromogen at 375 nm which is formed in 0.1 M NaOH. The third method is based on the measurement of 2: 1 complex formed between DOX and iron(III) in H₂SO₄ medium, the complex peaking at 420 nm (method C). The optimum conditions for all the three methods are optimized. Beer’s law was obeyed over the ranges 2.5–50.0, 1.50–30.0 and 10–100 g/mL for method A, method B and method C, respectively. The apparent molar absorptivity values are calculated to be 1.03 × 10⁴, 1.73 × 10⁴, and 5.21 × 10³ L mol⁻¹ cm⁻¹ for method A, method B, and method C, respectively. The Sandell sensitivity, limit of detection (LOD) and limit quantification (LOQ) values are also reported. All the methods were validated in accordance with current ICH guidelines. The developed methods were employed with high degree of precision and accuracy for the estimation of total drug content in commercial tablet formulations of DOX.     

Application of non-steroidal anti-inflammatory drugs for palladium determination

A highly sensitive spectrophotometric method for palladium determination using piroxicam and tenoxicam as new chromogenic reagents has been developed. In the presence of sodium lauryl sulfate (SLS), palladium reacts with piroxicam (PX) or tenoxicam (TX) to form stable yellow orange complexes in an acetate buffer solution of pH 5.0 at 424 nm and 426 nm with molar absorptivity of 7.16 × 10⁴ L mol⁻¹ cm⁻¹ and 1.20 × 10⁵ L mol⁻¹ cm⁻¹, respectively. Sandell sensitivity, detection, and quantitation limits were also calculated. Optimum conditions were evaluated considering pH, reagent concentration, time, temperature, and surfactant concentration. The complex system conforms to Beer’s law over the range of 0.07–1.28 μg mL⁻¹ palladium. The stoichiometric ratio and stability constant were also evaluated. Tolerance limits of many cations and anions were determined. Finally, the proposed method was applied successfully in the determination of palladium in jewellery, anode mud, synthetic mixtures, catalysts, and alloy samples.     

Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2–luminol–uranine chemiluminescent reaction

In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 × 10⁻¹⁰–5.0 × 10⁻⁶ mol L⁻¹ and a low detection limit (S/N = 3) of carbonate of 1.2 × 10⁻¹¹ mol L⁻¹. The average relative standard deviation for 1.0 × 10⁻⁹–9.0 × 10⁻⁷ mol L⁻¹ of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 × 10⁻⁶–6.0 × 10⁻² mg L⁻¹ and 0.08–30 mg L⁻¹ carbon, respectively. Recoveries of 97.4–106.4% for TIC and 96.0–98.5% for TOC were obtained by adding 5 or 50 mg L⁻¹ of carbon to the water samples. The relative standard deviations (RSDs) were 2.6–4.8% for TIC and 4.6–6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed. Figure Chemiluminescence profiles in batch system. 1, Injection of 100 μL of K₂CO₃ into 1.0 mL luminol-1.0 mL H₂O₂ solution; 2-3 and 4-5, Injection in sequence of 100 μL of K₂CO₃ and 100 μL of uranine into 1.0 ml luminol-1.0 mL H₂O₂ solution; C_luminol = 1.0 × 10⁻⁷ mol/L, C_H2O2 = 1.0 × 10⁻⁵ mol/L, C_uranine = 1.0 × 10⁻⁵ mol/L, C_K2CO3 = 1.0 × 10⁻⁷ mol/L except for 4-5 where C_K2CO3 = 1.0 × 10⁻⁴ mol/L     

Synthesis,crystal structure,and third-order nonlinear optical properties of a copper(I) one-dimensional coordination polymer

A copper(I) thiocyanate coordination polymer [Cu(Phen)(μ-NCS)]n (I) (Phen = 1,10-phenan-throline) has been synthesized by the low-temperature solid-state reaction. Single-crystal X-ray analyses reveal that compound I possesses a type of one-dimensional (1D) framework structure. Polymer I was characterized by elemental analyses, IR spectra, and UV-visifele spectra. The third-order nonlinear optical properties were also investigated, and they exhibit good nonlinear absorption and self-defocusing performance with modulus of the hyperpolarizability 4.94 × 10⁻³⁰ esu for I in a 6.35 × 10⁻⁴ mol dm⁻³ DMF solution.     

Spectrophotometric determination of <Emphasis Type="Italic">L</Emphasis>-ascorbic acid in pharmaceuticals

A simple and sensitive spectrophotometric method for the determination of L-ascorbic acid with leuco crystal violet is proposed. The determination is based on the oxidation of analyte by potassium iodate. The colourless oxidation products were formed in the quantity equivalent to iodide ions. The iodide ions react with the excess of iodate ions in acidic medium, to form free iodine which oxidized leuco crystal violet (LCV) to the liberated crystal violet (CV ⁺) dye, showing maximum absorption at 588 nm. The absorbance was measured at pH of 4.1–4.2 in 1 cm cuvettes. Beer’s law was obeyed in the concentration range 0.5–4.0 μg/mL. The molar absorptivity of the coloured compound is 4.14 × 10⁴ L/mol cm for L-ascorbic acid. The analytical parameters were optimized and the method was successfully applied to the determination of L-ascorbic acid in pharmaceuticals. The results were compared with those obtained by methods proposed in Polish Standard.     

Tetracyanoquinodimethanide adsorbed on a silica gel modified with titanium oxide for electrocatalytic oxidation of hydrazine

The electrocatalytical oxidation of hydrazine at low potential using tetracyanoquinodimethanide adsorbed on silica modified with titanium oxide was investigated by cyclic voltammetry and amperometry. The modified electrode was prepared modifying a carbon paste electrode employing lithium tetracyanoquinodimethanide adsorbed onto silica gel modified with titanium oxide. This electrode showed an excellent catalytic activity and stability for hydrazine oxidation. With this modified electrode, the oxidation potential of hydrazine was shifted toward less positive value, presenting a peak current much higher than those observed on a bare GC electrode. The linear response range, sensitivity and detection limit were, respectively, 2 up to 100 μmol l⁻¹, 0.36 μA l μmol⁻¹, and 0.60 μmol l⁻¹. The repeatability of the modified electrode evaluated in term of relative standard deviation was 4.2% for 10 measurements of 100 μmol l⁻¹ hydrazine solution. The number of electrons involved in hydrazine oxidation (4), the heterogenous electron transfer rate constant (1.08 × 10³ mol⁻¹ l s⁻¹), and diffusion coefficient (5.9 × 10⁻⁶ cm² s⁻¹) were evaluated with a rotating disk electrode.     

Capillary electrophoretic speciation of Cu(II) and Co(III) in the electroless copper plating baths

Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.) filled with an ethylenediamine sulfate electrolyte (20 mol L⁻¹ ethylendiamine, pH7.0 with H₂SO₄; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s hydrodynamic injection were 5×10⁻⁶ mol L⁻¹ for Cu(II) and 1×10⁻⁶ mol L⁻¹ for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively, with five consecutive injections of standard solution containing 5×10⁻⁵ mol L⁻¹ of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples is also demonstrated.