Sequential injection technique for determination of phenoxybenzamine hydrochloride and metoclopramide in pharmaceutical formulations

A sequential injection analysis (SIA) system is described for the determination of phenoxybenzamine hydrochloride and metoclopramide using spectrophotometer as detector. The method is based on the detection of an unstable red intermediate compound resulting from the reaction of phenoxybenzamine hydrochloride or metoclopramide with the diazotizating product of p-phenylenediamine with sodium nitrite in hydrochloric acid medium. The sampling frequency is 69 h⁻¹ and 75 h⁻¹ for phenoxybenzamine hydrochloride and metoclopramide, respectively. The linear range is 10–400 μg/mL for phenoxybenzamine hydrochloride with a detection limit of 0.081 μg/mL and 20–250 μg/mL for metoclopramide with a detection limit of 0.034 μg/mL. The RSD is 1.01 and 0.45% for phenoxybenzamine hydrochloride and metoclopramide, respectively. The proposed methods were used to determine phenoxybenzamine hydrochloride and metoclopramide in pharmaceuticals. The results are compared with those obtained by pharmacopoeia method. The article is published in the original.     

Investigating the post-chemiluminescence behavior of phenothiazine medications in the luminol–potassium ferricyanide system: molecular imprinting–post-chemiluminescence method for the determination of chlorpromazine hydrochloride

A new post-chemiluminescence (PCL) phenomenon was observed when phenothiazine medications were injected into the reaction mixture after the chemiluminescence (CL) reaction of luminol and potassium ferricyanide had finished. A possible reaction mechanism was proposed based on studies of the kinetic characteristics of the CL, CL spectra, fluorescence spectra, and on other experiments. The feasibility of determining various phenothiazine medications by utilizing these PCL reactions was examined. A molecular imprinting–post-chemiluminescence (MI-PCL) method was established for the determination of chlorpromazine hydrochloride using a chlorpromazine hydrochloride-imprinted polymer (MIP) as the recognition material. The method displayed high selectivity and high sensitivity. The linear range of the method was 1.0×10⁻⁸∼1.0×10⁻⁶, with a linear correlation coefficient of 0.9985. The detection limit was 3×10⁻⁹ g/ml chlorpromazine hydrochloride, and the relative standard deviation for a 1.0×10⁻⁷ g/ml chlorpromazine hydrochloride solution was 4.0% (n=11). The method has been applied to the determination of chlorpromazine hydrochloride in urine and animal drinking water with satisfactory results.      

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

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

Selective spectrophotometric determination of paracetamol with sodium nitroprusside in pharmaceutical and biological samples

A novel simple method to determine paracetamol with good selectivity has been established by using sodium nitroprusside as the chromogenic reagent. The experiment indicates that sodium nitroprusside can react with paracetamol in a basic solution to form a product with colored O-nitrosamines. The maximal absorption wavelength (λ_max) and the apparent molar absorption coefficient of the product are 700 nm and 3.4 × 10³ L/mol cm, respectively. A Good linear relationship is obtained between the absorbance and the concentration of paracetamol in a wide range of 0.19–96 μg/mL. The linear regression equation is A = 0.01695 + 0.02240C (μg/mL), with a correlation coefficient of 0.9993. The detection limit (3σ/κ) is 0.10 μg/mL, and the relative standard deviation (RSD) is 0.90% (n = 11). The parameters with regard to determination are optimized, and the reaction mechanism is discussed. The method has been successfully applied to the selective determination of paracetamol in pharmaceutical and biological samples.     

Flow‐Injection Chemiluminescence Analysis of Cloperastione Hydrochloride

Abstract

A new chemiluminescence (CL) reaction was observed when cloperastine hydrochloride was injected into the reaction mixture after the CL reaction of Ce(IV) and sodium sulfite finished. A new flow injection CL method for the determination of cloperastine hydrochloride was established based on the CL reaction. The relative standard deviation (RSD) for the determination of cloperastine hydrochloride was 1.3% (n=11, c=1.0×10^?6 g/mL). The CL intensity responded linearly to the concentration of cloperastine hydrochloride in the range 2.0×10^?7～2.0×10^?5 g/mL (r=0.9962). The detection limit was 5×10^?8 g/mL cloperastine hydrochloride. The method had been applied to the determination of cloperastine hydrochloride in tablets with satisfactory results.     

Extraction–thermal lens quantification of cobalt with Nitroso-R-Salt in two-phase aqueous systems with water-soluble polymer polyethylene glycol

A novel method is proposed for the extraction-thermal lens quantification of cobalt with Nitroso-R-Salt based on the distribution of the colored complex in a two-phase aqueous system on the basis of poly-ethylene glycol (PEG) and an ammonium sulfate solution followed by its thermal lens detection in the extract. The limit of detection is 0.3 μM (20 ng/mL); the lower limit of the analytical range is 0.7 μM (40 ng/mL); the relative standard deviation for the concentrations 1–50 μM makes 1–3% (n = 6, P = 0.95). In the determination of cobalt by spectrophotometry under the same conditions, the detection limit is 10 μM (0.6 μg/mL) and the lower limit of the analytical range is 40 μM (2.5 μg/mL). The precision of thermal lens measurements in PEG solutions is higher in comparison to that in aqueous ones because of the weaker interference of convection in aqueous solutions of PEG.     

Quantification of cis-Abienol in Oriental Tobacco Leaves by LC

A rapid and accurate method for the quantification of cis-abienol in oriental tobacco leaves by normal phase liquid chromatography was developed. Freeze-dried tobacco samples were sonicated in methylene chloride for 10 min. The supernatant was purified using a silica gel solid phase extraction cartridge. Ten milliliter of the resulting methylene chloride eluate was collected, then separated on a 250 × 4.6 mm, 5 μm particle-size CN column with n-hexane: ethyl acetate, 100:2 (v/v) at a flow rate of 1 mL min⁻¹. cis-Abienol was detected by UV absorption at 254 nm. The linear range was from 2.14 × 10⁻⁴ to 4.28 × 10⁻² mg mL⁻¹ and the correlation coefficient was 1.000. The average recovery was 98.7, 105.2 and 103.1% in five replicated sets of tobacco samples spiked with 0.2856, 0.7140 and 1.904 mg cis-abienol. The relative standard deviations (RSDs) were 1.04, 0.63 and 1.25%, respectively (n = 5). Limit of detection (S/N = 3) was 21.84 μg g⁻¹ and limit of quantification (S/N = 10) was 72.80 μg g⁻¹. The method was found to be suitable for determination of cis-abienol in oriental tobacco leaves. Furthermore, pure cis-abienol used for method validation was obtained by preparative reversed phase high-performance liquid chromatography. Identification was performed by UV detection, nuclear magnetic resonance and mass spectrometry.     

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.     

Separation ofN-carbamoyl aspartate andl-dihydroorotate from serum by high-performance liquid chromatography with fluorimetric detection

Summary A high-performance liquid chromatographic method, with 9-anthryldiazomethane as derivatizing agent, has been developed for the simultaneous determination ofN-carbamoyl aspartate andl-dihydroorotate in serum. Sample preparation for 1 mL serum was by simple liquid-liquid extraction and then derivatization. The compounds were separated on a Luna C18(2) column by use of a gradient prepared from acetonitrile and 10 mM sodium acetate buffer, pH 6.0, and fluorimetric detection was performed at excitation and emission wavelengths of 365 nm and 412 nm, respectively. The response was found to be linearly dependent on concentration between 0.8 and 60 μg mL⁻¹ forl-dihydrooratate and between 0.9 and 90 μg mL⁻¹ forN-carbamoyl aspartate; the mean recovery rates were 50 and 51%, respectively. The limits of detection and quantification were 0.33 μg mL⁻¹ and 0.6 μg mL⁻¹, respectively, forl-dihydroorotate and 0.4 μg mL⁻¹ and 0.7 μg mL⁻¹ forN-carbamoyl aspartate. This method can be used to assess accumulation ofN-carbamoyl aspartate andl-dihydroorotate in body fluids in situations where cellular pyrimidine de novo synthesis is impaired.     

Liquid chromatographic determination of meloxicam in serum after solid phase extraction

A liquid chromatographic method for the determination of meloxicam in serum has been developed. The technique includes a solid phase extraction of the serum samples on [poly (divinylbenzeneco-N-vinylpyrrolidone)] as a solid phase extraction sorbent. After conditioning, the cartridge was loaded with 1 mL of acidified serum containing an internal standard. Elution was carried out using 1 mL of water-acetonitrile (φ _r = 1: 1) mixture. After evaporation of the eluate to dryness and reconstitution of the residue with 0.1 mL of methanol, the samples were analyzed on a Symmetry C18 column. Mobile phase consisted of 1 % aqueous acetic acid/THF/acetonitrile (φ _r = 60: 30: 10) + 0.1 mL of 1-octane sulfonic acid. Detection was carried out using a photodiode array detector. Full validation of the proposed method is provided. Linearity of the method was proven over the range of 0.01–10 φg mL⁻¹ of meloxicam. Meloxicam assay was accurate and reliable with average intra- and inter-day precisions lower than 5.0 % and the intra- and inter-day accuracy higher than 97 %. Limits of detection (LOD) and quantitation (LOQ) found were 0.003 μg mL⁻¹ and 0.01 μg mL⁻¹, respectively. The proposed method was successfully utilized to quantify meloxicam in serum.     

Sensitive determination of phenothiazines in pharmaceutical preparation and biological fluid by flow injection chemiluminescence method using luminol-KMnO4 system

A flow injection chemiluminescence method was described for the determination of four phenothiazine drugs, namely, chlorpromazine hydrochloride, perphenazine hydrochloride, fluphenazine hydrochloride and thioridazine hydrochloride. Strong Chemiluminescence (CL) signal was produced when above-mentioned drug was injected into the mixed stream of luminol with KMnO₄. The linear ranges of the method were 0.0020-1.0 μg/mL chlorpromazine hydrochloride, 0.0040-3.0 μg/mL perphenazine hydrochloride, 0.0020-5.0 μg/mL fluphenazine hydrochloride and 0.0050-1.0 μg/mL thioridazine hydrochloride. The detection limits were 0.4 ng/mL chlorpromazine hydrochloride, 0.7 ng/mL perphenazine hydrochloride, 2 ng/mL fluphenazine hydrochloride and 0.7 ng/mL thioridazine hydrochloride. The proposed method was applied to the determination of chlorpromazine hydrochloride in injections and in mental patient's urine samples and the satisfactory results were achieved. The possible CL reaction mechanism was also discussed briefly.     

Spectrophotometric determination of methimazole in pharmaceutical,serum and urine samples by reaction with potassium ferricyanide-Fe(III)

This paper describes a novel method to determine methimazole by spectrophotometry using a potassium ferricyanide-Fe(III) reaction. The study indicates that at pH 4.0 Fe(III) is reduced to Fe(II) by methimazole and in situ formed Fe(II) reacts with potassium ferricyanide to give soluble Prussian Blue which is characterized by means of XRD analysis. The absorbance of Prussian Blue is measured at the absorption maximum of 735 nm, and the amount of methimazole can be determined based on this absorbance. Beer’s law is obeyed in the range of methimazole concentrations of 0.02–6.00 μg/mL. The equation of the linear regression is A = −0.0058 + 0.49988c (μg/mL), with a correlation coefficient of 0.9998 and RSD of 0.80%. The detection limit (3σ/k) is 0.015 μg/mL, and the apparent molar absorption coefficient of indirect determination of methimazole is 5.7 ± 10⁴ L/mol cm. This method has been successfully applied to the determination of methimazole in pharmaceutical, serum and urine samples, and average recoveries are in the range of 98.6–102.4%. Analytical results obtained with this novel method are satisfactory.     

Resolution of an intense sweetener mixture by use of a flow injection sensor with on-line solid-phase extraction

An integrated solid-phase spectrophotometry–FIA method is proposed for simultaneous determination of the mixture of saccharin (1,2-benzisothiazol-3(2H)-one-1,1-dioxide; E-954) (SA) and aspartame (N-l-α-aspartyl-l-phenylalanine-1-methyl ester; E-951) (AS). The procedure is based on on-line preconcentration of AS on a C₁₈ silica gel minicolumn and separation from SA, followed by measurement, at λ=210 nm, of the absorbance of SA which is transiently retained on the adsorbent Sephadex G-25 placed in the flow-through cell of a monochannel FIA setup using pH 3.0 orthophosphoric acid–dihydrogen phosphate buffer, 3.75×10^–3 mol L⁻¹, as carrier. Subsequent desorption of AS with methanol enables its determination at λ=205 nm. With a sampling frequency of 10 h⁻¹, the applicable concentration range, the detection limit, and the relative standard deviation were from 1.0 to 200.0 μg mL⁻¹, 0.30 μg mL⁻¹, and 1.0% (80 μg mL⁻¹, n=10), respectively, for SA and from 10.0 to 200.0 μg mL⁻¹, 1.4 μg mL⁻¹, and 1.6% (100 μg mL⁻¹, n=10) for AS. The method was used to determine the amounts of aspartame and saccharin in sweets and drinks. Recovery was always between 99 and 101%. The method enabled satisfactory determination of blends of SA and AS in low-calorie and dietary products and the results were compared with those from an HPLC reference method.     

Catalytic kinetic spectrophotometric determination of trace amounts of palladium with dahlia violet after separation and preconcentration on sulphydryl dextran gel

A sensitive and selective kinetic catalytic spectrophotometric method has been described for the determination of trace amounts of palladium(II). The method is based on the catalytic effects of palladium(II) on the reduction reactions of Dahlia Violet with sodium dihydrogen hypophosphite (NaH₂PO₂) in a sulfuric acid medium. Under optimal conditions, trace amounts of palladium(II) can be determined. A good linear range has been obtained in the concentration range of Pd(II) over 0.001–0.028 μg/mL with a detection limit of 5.9 × 10⁻¹⁰ g/mL. The method has been successfully applied to the determination of palladium(II) in ore and soil samples. The relative standard deviation was less than 5.0% (n = 11). The coexisting ions were eliminated by preconcentration and separation on sulphydryl dextran gel with satisfactory results. The text was submitted by the authors in English.     

Development of spectrofluorimetric methods for the determination of levosulpiride in pharmaceutical formulation

Simple, accurate, rapid, and sensitive spectrofluorimetric methods for the determination of levosulpiride in pharmaceutical formulation were developed utilizing its fluorescence reaction with Fe³⁺ (method A) and Al³⁺ (method B). The calibration curves were found to be linear in the concentration range 0.239–3.44 μg/mL and 0.310–2.730 μg/mL with limit of detection 0.005 μg/mL and 0.0032 μg/mL, respectively, for method A and method B. The reaction conditions were studied and optimized. In addition, the complexation of Mg²⁺ and Ca²⁺ was also studied. In all cases, an enhancement in fluorescence emission of levosulpiride upon formation of complex with metal ions was observed. A 2: 1 (drug: metal) stoichiometry for all the complexes was established. Benesi-Hildebrand method was applied for calculation of association constant at 25 and 35°C. The thermodynamic parameters obtained in this study revealed that the interaction process was spontaneous and mainly ΔS-driven.     

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.     

Determination of cadmium in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

The formation of a complex with 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) and cloud point extraction have been applied to the preconcentration of cadmium followed by its determination by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation were optimized. At pH 7.0, preconcentration of only 10 mL of sample in the presence of 0.05% TritonX-114 and 2.5 × 10⁻⁶ M 5-Br-PADAP enabled the detection of 0.04 μg/L cadmium. The enrichment factor was 21 for cadmium. The regression equation was A = 0.0439C(μg/L) + 7.2 × 10⁻³. The correlation coefficient was 0.9995. The precision for 10 replicate determinations at 10 μg/L Cd was 2.7% relative standard deviation (RSD). The proposed method has been applied to the determination of cadmium in water samples. The text was submitted by the authors in English.     

Flow injection spectrophotometric determination of iron(III) using diphenylamine-4-sulfonic acid sodium salt

A highly sensitive and very simple spectrophotometric flow-injection analysis (FIA) method for the determination of iron(III) at low concentration levels is presented. The method is based on the measurement of absorbance intensity of the red complex at 410 nm formed by iron(III) and diphenylamine-4-sulfonic acid sodium salt (DPA-4-SA). It is a simple, highly sensitive, fast, and low cost alternative method using the color developing reagent DPA-4-SA in acetate buffer at pH 5.50 and the flow-rate of 1 mL min⁻¹ with the sample throughput of 60 h⁻¹. The method provided a linear determination range between 5 μg L⁻¹ and 200 μg L⁻¹ with the detection limit (3S) of 1 μg L⁻¹ of iron(III) using the injection volume of 20 μL. FIA variables influencing the system performance were optimized. The amount of iron(III) and total iron in river and seawater samples was successfully determined. Repeatability of the measurements was satisfactory at the relative standard deviation of 3.5 % for 5 determinations of 10 μg L⁻¹ iron(III). The accuracy of the method was evaluated using the standard addition method and checked by the analysis of the certified material Std Zn/Al/Cu 43 XZ3F.     

Spectrophotometric determination of piroxicam

The possibility of the spectrophotometric determination of piroxicam based on the extraction of its ion associate (IA) with the polymethine dye, 5-thiocyanate-1,3,3-trimethyl-2[(1E)-3-[(2E)-1,3,3-trime-thyl-1-H-indol-2-ilidine]-propenyl]-3H-indolium chloride. The maximal recovery of IA with toluene is achieved when pH of the aqueous phase is 8.0–12.0 and the concentration of the dye is (1.0–2.0) × 10⁻⁴. The molar absorption coefficient of IA is 8 × 10⁴, the detection limit of piroxicam is 0.49 μg/mL. A procedure has been developed for the extraction-spectrophotometric determination of piroxicam in the concentration range 1.0–20.0 μg/mL.     

A simple flow injection spectrophotometric determination method for iron(III) based on O-acetylsalicylhydroxamic acid complexation

A simple and rapid flow-injection spectrophotometric method for the determination of iron(III) and total iron is proposed. The method is based on the reaction between iron(III) and O-acetylsalicylhydroxamic acid (AcSHA) in a 2 % methanol solution resulting in an intense violet complex with strong absorption at 475 nm. Optimum conditions for the determination of iron(III) and the interfering ions were tested. The relative standard deviation for the determination of 5 μg L⁻¹ iron(III) was 0.85 % (n = 10), and the limit of detection (blank signal plus three times the standard deviation of the blank) was 0.5 μg L⁻¹, both based on the injection volumes of 20 μL. The method was successfully applied in the determination of iron(III) and total iron in water and ore samples. The method was verified by analysing a certified reference material Zn/Al/Cu 43XZ3F and also by the AAS method.