A New Flow‐Injection Chemiluminescence Method for the Determination of Acyclovir and Gancyclovir

Abstract

A rapid and sensitive flow‐injection chemiluminescence (FI‐CL) method, which is based on the CL intensity that generated from the redox reaction of Ce(IV)‐rhodamine B in H₂SO₄ medium, for the determination of acyclovir and gancyclovir is described. For acyclovir, the determination range is 3×10^?8 g mL^?1–7×10^?5 g mL^?1, with 1.56×10^?8 g mL^?1 as its determination limit. During 11 repeated measurements for 1×10^?6 g mL^?1 acyclovir, the relative standard deviation was 2.08%. For gancyclovir, the determination range was 5×10^?8 g mL^?1–7×10^?5 g mL^?1, with 2.35×10^?8 g mL^?1 as its determination limit. The relative standard deviation is 2.83% with 11 repeated measurements of 1×10^?6 g mL^?1 gancyclovir. This method can be successfully used to determine the content of acyclovir and gancyclovir in injections, acyclovir in eye drops, and, maybe, also for other ciclovirs.     

Improved Multianalyte Determination of the Intense Sweeteners Aspartame and Acesulfame‐K with a Solid Sensing Zone Implemented in an FIA Scheme

Abstract

A multianalyte flow‐through sensor is proposed for the simultaneous determination of aspartame (AS) and acesulfame‐K (AK) in tabletop sweeteners. The procedure is based on the transient retention of AK in the ion exchanger Sephadex DEAE A‐25 placed in the flow‐through cell of a monochannel flow injection analysis (FIA) set‐up using pH 2.70 ortophosphoric acid/sodium dihydrogen phosphate buffer 0.06 M as carrier. In these conditions AS is very weakly retained, which makes it possible to measure the intrinsic ultraviolet (UV) absorbance of first AS and then AK after desorption by the carrier itself. The applicable concentration range, the detection limit, and the relative standard deviation were the following: for AS, from 10 to 100 µg mL^?1; 5.65 µg mL^?1; 3.4% (at 50 µg mL^?1); and for AK, between 40 and 100 µg mL^?1; 11.9 µg mL^?1 and 1.61% (at 50 µg mL^?1). The method was applied and validated satisfactorily for the determination of AS and AK blends in tabletop sweeteners. The results were compared against an HPLC reference method.     

The Determination of Perphenazine by a New Simple Flow‐Injection Chemiluminescence Method

Abstract

A rapid and simple flow‐injection chemiluminescence (CL) method is described for the determination of perphenazine, which is based on the CL intensity that generated from the redox reaction of Ce (IV)-perphenazine in HNO₃ medium is proportional to the perphenazine concentration without any sensitizers. The proposed method allows the determination range within 1.0×10^?7–7.0 ×10^?5 g mL^?1 with a detection limit of 8.0×10^?8 g mL^?1, and it has been successfully applied to the determination of the perphenazine in pharmaceutical tablet compared well with the official method.     

On the Effect of Hydrogen Peroxide on the Flow‐Injection Determination of Platinum Based on Luminol Chemiluminescent Reaction

Abstract

A flow‐injection chemiluminescent (CL) method for the determination of trace amounts of Pt(IV) based on the oxidation reaction of luminol in alkaline solution is proposed. The effect of Pt(IV) on the oxidation of luminol was studied in the absence and in the presence of hydrogen peroxide. The positive effect of hydrogen peroxide as well as chloride ions on the sensitivity of measurements was observed. The developed method is characterized by a low limit of detection of Pt (LOD=0.06 ng mL^?1) and good reproducibility (RSD=2.2%). The addition of hydrogen peroxide to the reaction medium resulted in decreasing of platinum detection limit to 0.03 ng mL^?1.     

Electrochemical Enzyme‐Linked Immunoassay for the Determination of Estriol Using Methyl Red as Substrate

Abstract

A new electrochemical substrate for horseradish peroxidase, methyl red, is reported. In this reaction system, horseradish peroxidase can catalyze the redox reaction of methyl red and H₂O₂. Methyl red exhibits a sensitive voltammetric peak at?0.51 V vs. Ag/AgCl reference electrode, the decrease of the peak current of methyl red is in proportion to the concentration of horseradish peroxidase (HRP). The linear range for determination of horseradish peroxidase is 5.0×10^?8～5.0×10^?7 g mL^?1 and the detection limit is 1.8×10^?8 g mL^?1. The relative standard deviation is 3.3% when 2.0×10^?7 g mL^?1 HRP was sequentially determined 11 times. A voltammetric enzyme‐linked immunoassay method for the determination of estriol was developed, based on this electrochemical system. The linear range for determination of estriol is 1.0～1000.0 ng mL^?1, and the detection limit is 0.33 ng mL^?1. The relative standard deviation for 11 parallel determinations with 200 ng mL^?1 estriol is 4.8%. Some pregnancy serum samples were analyzed with satisfactory results.     

Catalytic Square-Wave Voltammetric Determination of Acrylamide in Potato Chips

Abstract

Square-wave voltammetry is a fast technique used for determination of trace amounts of acrylamide. When cobalt(II) ions were added to the acrylamide solution, a catalytic peak at about ?1.35 V vs. Ag/AgCl was observed, which was proportional to acrylamide concentration. The calibration curve showed good linearity in the range of 200–800 ng mL^?1 of acrylamide with a regression coefficient of 0.9989. The limit of detection of the method was 3.52 ng mL^?1, and the relative standard deviations for concentrations of 300 ng mL^?1 and 700 ng mL^?1 were 99.8% × 10^?2 and 79.7% × 10^?2, respectively.     

Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol^?1 cm^?1 and 0.67 ng mL^?1, respectively. The detection limit of Hg(II) is 1.40×10^?2 ng mL^?1, and Beer's law is valid in the concentration range 0.05–2.40 µg mL^?1. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL^?1 of Hg(II) and 0.065–0.650 µg mL^?1 of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL^?1 of Hg(II) and 0.620 µg mL^?1 of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.     

Flow Injection Chemiluminescence Sensor with Novel Rhodanine Ramification for Determination of Fenfluramine Based on Molecularly Imprinted Polymer

Abstract

Flow injection chemiluminescence (FI-CL) with molecularly imprinted polymer (MIP) was applied to determine fenfluramine. The fenfluramine-imprinted polymer was prepared with acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Methyl and sulfonic group were introduced to rhodanine matrix, and a novel rhodanine ramification 3MORASP was synthesized by the author, and it was used as chemiluminescence reagent. 3-(3′-Methoxyphenyl)-5(2′-sulfonylphenylazo)-rhodanine (3MORASP), first synthesized by the authors, was used as chemiluminescence (CL) reagent. The novel flow path of FI-CL was designed, which made three merged streams of reactants injected into MIP column move through different pathways simultaneously. Fenfluramine was detected based on the reaction of fenfluramine, 3MORASP, and potassium permanganate in an acidic medium. The CL intensity was correlated linearly with the concentration of fenfluramine over the range of 1.0 × 10^?7 to 5.0 × 10^?6 g · mL^?1, and the detection limit was 9.48 × 10^?9 g · mL^?1. The relative standard deviation (RSD) was 2.4% for determination of 1.0 × 10^?6 g · mL^?1 fenfluramine (n = 11). This method was successfully applied to the determination of fenfluramine in weight-reducing tonic.     

Determination of Meclofenoxate Hydrochloride by Resonance Rayleigh Scattering Method Coupled with Flow Injection Technique

In pH 1.0 acidic medium, 12-Tungstophosphoric acid (TP) reacted with meclofenoxate (MFX) to form an ion-associate complex, which resulted in a significant enhancement of the resonance Rayleigh scattering (RRS) intensity. The RRS intensity at the maximum scattering peak of 374 nm was linear to the concentration of MFX in the range of 0.2–12.0 μg mL^?1. Therefore, a novel method for the determination of MFX by RRS method coupled with flow injection analysis (FIA) technique was developed. The method has highly sensitivity and the detection limit (3σ) was 5.6 ng mL^?1. The present method was applied to the determination of MFX in pharmaceutical preparations and the results agreed well with those provided by the pharmacopeia. The average recovery of standard addition in capsules was 97.0–103.1%. The proposed method exhibited the satisfactory reproducibility with a relative standard derivation (R.S.D.) of 3.7% for 9 successive determinations of 4.0 μg mL^?1 MFX. The maximal sample throughput in the optimized system was 48 h^?1. In addition, the optimum experiment condition, the effect of coexisting substance, and influence of FIA variables were investigated in the paper.     

Voltammetric sensing of triclosan in the presence of cetyltrimethylammonium bromide using a cathodically pretreated boron-doped diamond electrode

ABSTRACT

In the present study, a simple, cheap and sensitive electrochemical method based on a cathodically pretreated boron-doped diamond (CPT-BDD) electrode is described for the detection of triclosan with the cationic surfactant (cetyltrimethylammonium bromide, CTAB) media. The oxidation of triclosan was irreversible and exhibited an adsorption controlled process. The sensitivity of the adsorptive stripping voltammetric measurements was significantly improved with addition of CTAB. Using square-wave stripping mode, a linear response was obtained for triclosan determination in Britton-Robinson buffer solution at pH 9.0 containing 2.5 × 10^?4 M CTAB at around + 0.67 V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The method could be used in the range of 0.01–1.0 μg mL^?1 (3.5 × 10^?8–3.5 × 10^?6 M), with a detection limit of 0.0023 μg mL^?1 (7.9 × 10^?9 M). The feasibility of the proposed method for the determination of triclosan in water samples was checked in spiked tap water.     

Determination of Diethylstilbestrol by Time-resolve Fluoroimmunoassay

Abstract

A time-resolved fluoroimmunoassay (TRFIA) was developed for the determination of diethylstilbestrol (DES). The method was based on a competitive immunoassay using europium-labeled anti-DES antibody and DES-bovine serum albumin (DES-BSA) as coated antigen. The TRFIA exhibited a typical response for DES at concentrations of 0.001–100 ng · mL^?1, the linear correlation coefficient is 0.9933, and the detection limit (LOD) is 0.595 pg · mL^?1. Some serum and water samples have been analyzed by using this method with satisfactory results. Compared with the routine fluorescence immunoassay (FIA), this method was more sensitive. The TRFIA may offer a valuable alternative method for the DES detection and could be applied to routine analysis.     

A Sensitive Flow Injection Fluorimetry for the Determination of Carbamazepine in Human Plasma

Abstract

A simple, sensitive, and specific flow injection fluorimetric method has been developed for the determination of carbamazepine (CBZ). The proposed method is based on use of a solid‐phase reactor containing lead dioxide for on‐line oxidization of CBZ into a strongly fluorescent compound in a medium of phosphoric acid. The product has a green‐yellow fluorescence at a maximum excitation wavelength of 355 nm and an emission wavelength of 478 nm. Under the optimum conditions, the fluorescence intensity is proportional to the concentration of CBZ ranging from 0.0005 to 4.000 µg mL^?1. The detection limit is 5.7×10^?5 µg mL^?1 (2.4×10^?10 mol L^?1) and the relative standard deviation is 1.4% at the sampling rate of 45 h^?1. The proposed method has been applied to clinical estimation of CBZ in real patients' plasma samples with the results compared with those obtained by HPLC method.     

A Novel Method for the Determination of Streptomycin Using Sodium Nitroprusside as a Chromogenic Reagent by Spectrophotometry

Abstract

A rapid and simple spectrophotometric method for the determination of streptomycin has been developed and validated. The method was based on the reaction of streptomycin with sodium nitroprusside in the alkaline medium forming a red product measured at the maximum absorption of 495 nm. The stoichiometric ratio of the product is 1:1. Beer's law is obeyed in a range of 1.87 µg mL^?1 ～ 279.8 µg mL^?1 of streptomycin and ?₄₉₅ is 6.0 × 10³ L·mol^?1 cm^?1.Under the optimum condition, the equation of linear regression is A = 0.00742 + 0.05683 C (× 10⁵ mol·L^?1), with a linear correlation coefficient of 0.9990. The detection limit (3σ/k) is 0.96 µg mL^?1, the relative standard deviation (RSD) is 2.40%, and the average recovery rate is 98.3%–102.7%. Every parameter has been optimized, and the reaction mechanism has been studied. The proposed method has been successfully applied to the determination of streptomycin for injections and tablets of pharmaceutical preparation. Analytical results obtained by this new method were very gratifying.     

Static and Hydrodynamic Monitoring of Citalopram Based on its Electro-oxidation Behavior at a Glassy-Carbon Surface

Abstract

The electrooxidative behavior of citalopram (CTL) in aqueous media was studied by cyclic voltammetry (CV) and square-wave voltammetry (SWV) at a glassy-carbon electrode. The electrochemical behaviour of CTL involves two electrons and two protons in the irreversible and diffusion controlled oxidation of the tertiary amine group. The maximum analytical signal was obtained in a phosphate buffer (pH = 8.2). For analytical purposes, an SWV method and a flow-injection analysis (FIA) system with amperometric detection were developed. The optimised SWV method showed a linear range between 1.10 × 10^?5–1.20 × 10^?4 mol L^?1, with a limit of detection (LOD) of 9.5 × 10^?6 mol L^?1. Using the FIA method, a linear range between 2.00 × 10^?6–9.00 × 10^?5 mol L^?1 and an LOD of 1.9 × 10^?6 mol L^?1 were obtained. The validation of both methods revealed good performance characteristics confirming applicability for the quantification of CTL in several pharmaceutical products.     

Electroanalytical Study of the Pesticide Ethiofencarb

Abstract

A detailed study of voltammetric behavior of ethiofencarb (ETF) is reported using glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). With GCE, it is possible to verify that the oxidative mechanism is irreversible, independent of pH, and the maximum intensity current was observed at +1.20 V vs. AgCl/Ag at pH 1.9. A linear calibration line was obtained from 1.0×10^?4 to 8.0×10^?4 mol L^?1 with SWV method. To complete the electrochemical knowledge of ETF pesticide, the reduction was also explored with HMDE. A well‐defined peak was observed at –1.00 V vs. AgCl/Ag in a large range of pH with higher signal at pH 7.0. Linearity was obtained in 4.2×10^?6 and 9.4×10^?6 mol L^?1 ETF concentration range.

An immediate alkaline hydrolysis of ETF was executed, producing a phenolic compound (2‐ethylthiomethylphenol) (EMP), and the electrochemical activity of the product was examined. It was deduced that it is oxidized on GCE at +0.75 V vs. AgCl/Ag with a maximum peak intensity current at pH 3.2, but the compound had no reduction activity on HMDE.

Using the decrease of potential peak, a flow injection analysis (FIA) system was developed connected to an amperometric detector, enabling the determination of EMP over concentration range of 1.0×10^?7 and 1.0×10^?5 mol L^?1 at a sampling rate of 60 h^?1. The results provided by FIA methodology were performed by comparison with results from high‐performance liquid chromatography (HPLC) technique and demonstrated good agreement with relative deviations lower than 4%. Recovery trials were performed and the obtained values were between 98 and 104%.     

Flow Injection and Batch Spectrophotometric Determination of Ibuprofen Based on its Competitive Complexation Reaction with Phenolphthalein‐β‐Cyclodextrin Inclusion Complex

Abstract

Rapid, simple, and accurate spectrophotometric method is presented for the determination of ibuprofen by batch and flow injection analysis methods. The method is based on ibuprofen competitive complexation reaction with phenolphthalein‐β‐cyclodextrin (PHP‐β‐CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of ibuprofen was measured. Ibuprofen can be determined in the range 8.0×10^?6 ?3.2×10^?4 and 2.0×10^?5?5.0×10^?3 mol l^?1 by batch and flow methods, respectively. The limit of detection and limit of quantification were 6.19×10^?6 and 2.06×10^?5 mol l^?1 for batch and 1.77×10^?5 and 5.92×10^?5 mol l^?1 for flow method, respectively. The sampling rate in flow injection analysis method was 120±5 samples h^?1. The method was applied to the determination of pharmaceutical formulations.     

Flow-Injection Analysis Based on Extraction and Spectrophotometric Determination of Penicillins with Thiazine Dyes

Abstract

A new method for flow-injection analysis (FIA) for the determination of penicillins based on the extraction and spectrophotometric determination of ion associates with selected thiazine dyes (methylene blue, azure A, and azure B) is proposed. The reaction conditions (c_dye = 2 × 10^?4 mol l^?1, c_KCl = 1 mol l^?1, pH ? 6, λ = 635 nm) were found. The factorial design has been carried out to determine the optimum flow conditions. A wide linear dynamic range of calibration curves (5.1–700 µg ml^?1 for penicillin V with all dyes, R = 0.9985) and good repeatability (e.g., relative standard deviation [RSD] = 4.6–0.6% in this concentration range for the reaction with azure B) were found. The detection limit for penicillin V is 1.5 µg ml^?1, and the determination limit is 5.1 µg ml^?1. The maximum analysis rate is 35 samples per h. The practical samples of pharmaceutics were tested. There are no interferences from the additives in pharmaceutics.     

GC Determination of Cisplatin in Serum and Urine of Cancer Patients after Chemotherapy as Platinum (II) Pyrrolidinedithiocarbamate Chelate

A gas chromatographic procedure has been developed for determination of cisplatin from pharmaceutical preparation, serum and urine after chemotherapy of cancer patients as platinum(II) pyrrolidinedithiocarbamate chelate. The elution was carried from the column DB-1701 (30 m × 0.32 mm i.d.) coupled with FID detection. Cu(II), Ni(II), Co(III), Mn(II), Fe(III), Zn(II) and VO(II) when present together with Pt(II) separated completely and did not affect the determination of platinum. The linear calibration curve for platinum (II) was within 1–30 μg mL^?1 with a detection limit of 300 ng mL^?1. The amount of cisplatin detected from serum and urine was 250–325 and 20–116 ng mL^?1 with relative standard deviations (RSD) of 0.8–1.2%, and 0.9–1.2%. The % recovery of Pt from serum and urine by standard addition was 98 and 98.2% with RSD 1.4 and 1.1%.     

Removal, preconcentration and spectrophotometric determination of U(VI) from water samples using modified maghemite nanoparticles

Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples. The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10^?4–1.0 × 10^?2 mol L^?1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on A-MMNPs was 285 mg g^?1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L^?1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration graph was linear in the range 0.04–2.4 ng mL^?1 (1.0 × 10^?10–1.0 × 10^?8 mol L^?1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL^?1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL^?1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.     

Chemiluminometric Determination of the Pesticide Pirimicarb by a Flow Injection Analysis Assembly

Abstract

A flow injection (FI) method is described for the determination of pirimicarb. It was found that an enhanced chemiluminescence (CL) signal is obtained when employing the luminol–H₂O₂–horseradish peroxidase (HRP) system. Under the optimum experimental conditions, the enhanced CL intensity was linear with the concentration 4.25–30.75 ng mL^?1 (r = 0.997, n = 8) with a relative standard deviation of 0.99%, containing 12.75 ng mL^?1 (n = 8). The limit of detection of the investigated compound was 0.12 ng mL^?1. The method shows a moderate selectivity against other pesticides (Amitrole, Atrazine, 2,4,5-T, Dichlorprop, and Metamidophos).The proposed method was sensitive, simple, rapid, and successfully applied to the determination of pirimicarb when it is applied in freshwater; the mean recoveries were 98.3–118.5%.