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PubMed1995

Aqueous nitrite ion determination by selective reduction and gas phase nitric oxide chemiluminescence.

An improved method of flow injection analysis for aqueous nitrite ion exploits the sensitivity and selectivity of the nitric oxide (NO) chemilluminescence detector. Trace analysis of nitrite ion in a small sample (5-160 microL) is accomplished by conversion of nitrite ion to NO by aqueous iodide in acid. The resulting NO is transported to the gas phase through a semipermeable membrane and subsequently detected by monitoring the photoemission of the reaction between NO and ozone (O3). Chemiluminescence detection is selective for measurement of NO, and, since the detection occurs in the gas-phase, neither sample coloration nor turbidity interfere. The detection limit for a 100-microL sample is 0.04 ppb of nitrite ion. The precision at the 10 ppb level is 2% relative standard deviation, and 60-180 samples can be analyzed per hour. Samples of human saliva and food extracts were analyzed; the results from a standard colorimetric measurement are compared with those from the new chemiluminescence method in order to further validate the latter method. A high degree of selectivity is obtained due to the three discriminating steps in the process: (1) the nitrite ion to NO conversion conditions are virtually specific for nitrite ion, (2) only volatile products of the conversion will be swept to the gas phase (avoiding turbidity or color in spectrophotometric methods), and (3) the NO chemiluminescence detector selectively detects the emission from the NO + O3 reaction. The method is free of interferences, offers detection limits of low parts per billion of nitrite ion, and allows the analysis of up to 180 microL-sized samples per hour, with little sample preparation and no chromatographic separation. Much smaller samples can be analyzed by this method than in previously reported batch analysis methods, which typically require 5 mL or more of sample and often need chromatographic separations as well.

Colorimetry↗
PubMed2006

Electroanalytical determination of paroxetine in pharmaceuticals.

Electroanalytical methods based on square-wave adsorptive-stripping voltammetry (SWAdSV) and flow-injection analysis with SWAdSV detection (FIA-SWAdSV) were developed for the determination of paroxetine (PRX). The methods were based on the reduction of PRX at a mercury drop electrode at -1.55V versus Ag/AgCl, in a borate buffer of pH 8.8, and the possibility of accumulating the compound at the electrode surface. Because the presence of dissolved oxygen did not interfere significantly with the analysis, it was also possible to determine PRX using FIA-SWAdSV. This method enables analysis of up to 120 samples per hour at reduced costs. Both methods developed were validated and successfully applied to the quantification of PRX in pharmaceutical products.

Electrochemistry↗
PubMed2005

Study of the voltammetric behaviour of metam and its application to an amperometric flow system.

The electrochemical behaviour of the pesticide metam (MT) at a glassy carbon working electrode (GCE) and at a hanging mercury drop electrode (HMDE) was investigated. Different voltammetric techniques, including cyclic voltammetry (CV) and square wave voltammetry (SWV), were used. An anodic peak (independent of pH) at +1.46 V vs AgCl/Ag was observed in MT aqueous solution using the GCE. SWV calibration curves were plotted under optimized conditions (pH 2.5 and frequency 50 Hz), which showed a linear response for 17-29 mg L(-1). Electrochemical reduction was also explored, using the HMDE. A well defined cathodic peak was recorded at -0.72 V vs AgCl/Ag, dependent on pH. After optimizing the operating conditions (pH 10.1, frequency 150 Hz, potential deposition -0.20 V for 10 s), calibration curves was measured in the concentration range 2.5 x 10(-1) to 1.0 mg L(-1) using SWV. The electrochemical behaviour of this compound facilitated the development of a flow injection analysis (FIA) system with amperometric detection for the quantification of MT in commercial formulations and spiked water samples. An assessment of the optimal FIA conditions indicated that the best analytical results were obtained at a potential of +1.30 V, an injection volume of 207 muL and an overall flow rate of 2.4 ml min(-1). Real samples were analysed via calibration curves over the concentration range 1.3 x 10(-2) to 1.3 mg L(-1). Recoveries from the real samples (spiked waters and commercial formulations) were between 97.4 and 105.5%. The precision of the proposed method was evaluated by assessing the relative standard deviation (RSD %) of ten consecutive determinations of one sample (1.0 mg L(-1)), and the value obtained was 1.5%.

Electric Impedance↗
PubMed2001

(Immuno)affinity chromatography: a versatile tool for fast and selective purification, concentration, isolation and analysis.

Today, thanks to the availability of tailor made biomolecules with the desired biological functions, separations based upon (immuno)affinity techniques are more and more common in a large field of applications. By using the high selectivity of biomolecules (antibodies, receptors, specific proteins), this technique offers the possibility of isolating compounds from complex samples with a selectivity which cannot be achieved by other chromatographic methods. In order to succeed, however, the solid phase support for the immobilisation of the ligand of interest plays a prominent role. For this reason, numerous supports have already been introduced while research on new materials with additional advantages is continued. Here, a new solid phase support will be discussed for (immuno)affinity applications. This material demonstrates low non-specific adsorption and high ligand accessibility, which enables an enhanced selectivity and capacity. Because the material is available in large quantities and exhibits superb mechanical and physical stability, selective isolations have been performed on analytical as well as preparative scale. To demonstrate the potential of this new support, several applications will be presented. Based upon immunoaffinity, two applications for the determination of oestradiol in serum respectively vitamin B12 in fermentation broth will be presented. Regarding affinity chromatography, an enzyme reactor in which the enzyme glucose oxidase is immobilised on the new material, is made for the detection of glucose by Flow Injection Analysis and electrochemical detection. Next, to isolate, identify and test components on their xeno-oestrogenic activity, an affinity column is produced in which human oestrogen receptor is covalently coupled. Several components are screened on their biological activity and the results obtained will be presented here.

Chromatography, Affinity↗
PubMed1999

Determination of platinum in rat dorsal root ganglion using ICP-MS.

This study evaluated the performance of inductively coupled plasma mass spectrometry for the determination of platinum (Pt) in rat dorsal root ganglion. The method detection limit was found to be 0.008 ng/mL of Pt, which corresponds to 4 pg of Pt per milligram of ganglia. The standard deviations in the tissue matrix were 5.7% or better and minimum matrix effect was observed. Compared to indium, the use of iridium or a combination of iridium and bismuth as internal standard(s) provided more accurate measurement. The Pt in the tissue digestate was stable for a minimum of 46 d at levels above 0.05 ng/mL. Flow injection analysis using undiluted digestates resulted in approximately 20% signal enhancement. Internal standard correction was necessary to obtain accurate results. The method was used in initial studies in which rats were dosed with cisplatin and has shown that Pt accumulates and persists in dorsal rat ganglion following treatment.

Animals↗
PubMed1993

Effect of an ultraviolet light-activated coating material on reduction of the leaching of methyl methacrylate and formaldehyde from denture acrylic resins.

Effect of glazing with an ultraviolet light-activated coating material on reduction of the leaching of methyl methacrylate and formaldehyde from denture acrylic resins was quantitatively evaluated. Disks prepared from auto-polymerized resins were painted with the material and radiated with ultraviolet light. The disks were immersed in artificial saliva and the concentrations of methyl methacrylate and formaldehyde leached were determined by high-performance liquid chromatography and flow injection analysis. Compared to untreated controls, the glaze significantly decreased concentrations of both leachable substances. Treatment with an ultraviolet light-activated coating material is effective in suppressing the leaching of methyl methacrylate and formaldehyde from acrylic resins as well as in smoothing the denture surfaces.

Acrylic Resins↗
PubMed2002

Open-access liquid chromatography/mass spectrometry in a drug discovery environment.

The use of open-access mass spectrometry to monitor synthetic chemistry reactions, and also the integrity and purity of new chemical entities, has been a part of the medicinal chemist's tool-box for more than 5 years. Originally in our group at Wyeth Research there were two open-access methods available to the chemists, flow injection analysis (FIA) and liquid chromatography/mass spectrometry (LC/MS). The FIA method was approximately 3 min long, while the LC/MS method was approximately 20 min long (including an 8 min gradient). Within the first 2 years, the total number of open-access analyses increased by approximately 125%. It is interesting, however, that the number of LC/MS analyses increased by more than 285%. This is attributed to the fact that the chemists began using the LC/MS data to monitor reactions and also to check final product integrity and purity. In addition, the number of chemists performing parallel synthesis reactions has increased; thus, individual chemists can produce sample sets of up to 100 vials. This paper describes the implementation of new methodology, which accommodates the need for much faster run times and also the ability to acquire alternating positive and negative ion spectra within the same run. In addition, the instrument has been configured to e-mail the resulting processed data report to the submitting chemist. Several methods have been developed, including structure elucidation using in-source collision-induced dissociation (CID) and night-time analysis. The LC/MS methods for this system are described herein and are applicable to both industrial and academic synthetic chemistry optimization efforts.

Chromatography, Liquid↗
PubMed2002

Simultaneous dissolution profiles of two drugs, sulfadiazine-trimethoprim and amitriptyline-perphenazine, in solid oral dosage forms by a FIA manifold provided with a single spectrophotometric detector.

The simultaneous determination of two dissolution profiles wih the aid of a flow injection analysis assembly has been applied to: (a) sulfadiazine-trimethoprim in tablets and (b) amitriptyline-perphenazine in sugar coated pills. The selected combinations are drugs which have overlapping UV-vis spectra. The officially proposed procedure from the pharmacopoeias has been adapted for the FIA methodology and derivative spectrophotometry and zero crossing. Preliminary experiments on the suitability of the simultaneous determination of both drugs were performed. The empirical profiles were adjusted by regression analysis using different approaches. The 3-parameter plot method was finally selected as the most suitable for the sulfadiazine-trimethoprim and the 4-parameter equation plot for amitriptyline-perphenazine.

Administration, Oral↗
PubMed2003

Determination of bopindolol using the flow injection technique coupled with solid phase extraction.

In the proposed procedure, the determination of bopindolol using a flow injection analysis (FIA) technique, with spectrophotometric detection at 635 nm, is described. The method is based on the production of a green, water-soluble complex with ferric ions in acid medium. The automated lab-made FIA system was used for the direct determination of bopindolol in tablets. Bopindolol was adsorbed onto the solid phase in a mini-column, which was integrated directly into the flow system. The positive feature of the use of solid phase extraction (SPE) was the pre-concentration of bopindolol (seven times). The sample throughput was 50 samples per hour. Using the SPE method, bopindolol was determined with a linear range from 125 to 1000 microg ml(-1) (Relative standard deviation (R.S.D.)=1.87%), with a detection limit (3sigma) of 70 microg ml(-1). The method was applied to the determination of bopindolol in Sandonorm tablets. The results obtained were compared with a conventional HPLC method, both analytical techniques were in good agreement.

Calibration↗
PubMed2005

QCM-FIA with PGMA coating for dynamic interaction study of heparin and antithrombin III.

In this work, we describe a method of constructing a film of linear poly(glycidyl methacrylate) (PGMA) polymer onto the surface of quartz crystal microbalance (QCM) electrode as a coating material that allows easy coupling of heparin molecules onto the electrode and facilitates the determination of the interaction between heparin and antithrombin III (AT III). The PGMA film was characterized with atomic force microscopy (AFM) and infra-red spectroscopy. The coupling of heparin was accomplished in one step solution reaction. A home-made quartz crystal microbalance-flow injection analysis (QCM-FIA) system with data analysis software developed in our laboratory was used to determine the interaction. The interactions between immobilized heparin and AT III were studied with various concentrations under various conditions. The obtained constants are kass=(1.49+/-0.12)x10(3)mol-1ls-1, kdiss=(3.94+/-0.63)x10(-2)s-1, KA=(3.82+/-0.33)x10(4)mol-1l.

Adsorption↗
PubMed1991

An on-line immunoassay method for theophylline using a protein A immunoreactor.

A heterogeneous fluorescence immunoassay for theophylline has been automated using a flow injection analysis system containing a protein A solid phase reactor to separate antibody-bound and unbound fluorescein-theophylline. For each sample the antibody-protein A reaction takes place at near neutral pH, and the complexes are eluted at acid pH. The antibody-binding capacity of the reaction greatly exceeds the antibody level in each sample incubation mixture, and a single reactor can be repeatedly cycled between neutral and acid pHs. Experimental variations such as reactor size, flow rate, pH values, and reactant concentrations have been studied. Theophylline could readily be determined at the micrograms ml-1 level with on-line incubation with antibodies.

Automation↗
PubMed1997

Investigation of a new amoxicillin sodium impurity unstable in solution.

A new amoxicillin sodium impurity was detected by reversed-phase HPLC in commercial injectable preparations only when examined very soon after the drug was dissolved in the solvent vial (within about 10 min). The stability of this impurity was investigated by the degradation kinetic of its aqueous solutions. Ionspray mass spectrometry with flow-injection analysis and HPLC-MS methods were used to establish its nature. Some hypotheses concerning its chemical structure were formulated. The most likely assumption referred to the (5S,6R) amoxicillin piperazinedione diasteroisomer. The presence of the amoxicilloic acid methyl ester, an intermediate of the amoxicillin degradation process, was also hypothesized.

Amoxicillin↗
PubMed2004

Development of agmatine sensor using the combination of putrescine oxidase and agmatinase for squid freshness.

Agmatine (Agm) is an indicator of squid freshness. The Agm sensor was developed using flow injection analysis (FIA) that consisted of the putrescine oxidase (PuOx) reactor, the agmatinase (AUH)-PuOx reactor and two oxygen electrodes. In the proposed sensor, the first step is that coexisting cadaverine (Cad) and putrescine (Put) are removed by passing through the PuOx reactor and the initial decomposition is determined by the amount of oxygen consumed, simultaneously. The second step is that the amount of Agm is determined by the amount of oxygen consumed in the AUH-PuOx reactor. The optimum conditions for the use of the Agm sensor were as follows: 50 mM HEPES containing MnSO4 at a final concentration of 5 mM, pH 8.0, flow rate of 0.6 mL min(-1) and injection volume of 50 microL. A single assay could be completed in approximately 3 min. A linear relationship was obtained between the output and the Agm concentration in the range of 0.01-1 mM Agm with a correlation coefficient of 0.999. The detection limit was 0.005 mM. The relative standard deviations (RSDs) were 3.14 and 1.19% (n = 20) for 0.1 and 0.3 mM Agm, respectively. The extracts of squid were injected into the proposed sensor and the results were compared with those obtained using the conventional high-performance liquid chromatography (HPLC) method. A correlation was observed between the results obtained by the proposed sensor and those obtained by the conventional method. The determination of squid freshness is one of the good uses of the proposed Agm sensor.

Agmatine↗
PubMedDate not supplied

Library preparation of derivatives of 1,4,10,13-tetraoxa-7,16-diaza-cycloctadecane and their fluorescence behavior for signaling purposes.

In the present work, we report the library preparation on solid supports of 20 derivatives of 1,4,10,13-tetraoxa-7,15-diaza-cycloctadecane 1(a-e)(w,x,y,z) carrying a fluorescent dansyl group. The sensing fluorescence behavior of these materials toward alkali and alkali earth metal ions was studied by packing the beads into a conventional flow-through cell in a FIA (flow injection analysis) approach. The fluorescence emission of these materials' responses shows a fluorescence increase to Li+, Na+, K+, NH4+, Ca2+, and Mg2+ with maximum sensitivity for Mg2+ over the rest of the ions. The analytical potential of these materials is outlined, and the sensing response mechanism, based on a photoinduced electron-transfer process, is proposed.

Alkanes↗
PubMed2001

Electrochemiluminescence of tris(2,2'-bipyridine)ruthenium(II) immobilized in poly(p-styrenesulfonate)-silica-Triton X-100 composite thin-films.

The electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)3(2+)] immobilized in poly(p-styrenesulfonate) (PSS)-silica-Triton X-100 composite films was investigated. The cooperative action of PSS, sol-gel and Triton X-100 attached Ru(bpy)3(2+) to the electrode strongly, and the presence of Triton X-100 prevented drying fractures of the sol-gel films during gelation and even on repeated wet-dry cycles. The modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and NADH in a flow injection analysis (FIA) system with a newly designed flow cell. The detection scheme exhibited good stability, short response time and high sensitivity. Detection limits were 0.1, 0.1 and 0.5 micromol L(-1) for oxalate. TPA and NADH, respectively, and the linear concentration range extended from 0.001 to 1 mmol L(-1) for the three analytes. Applications of the flow cell in ECL and electrochemical detection, as well as the immobilization of reagents based on the cooperative action, are suggested.

Journal Article↗
PubMed2002

[Applications of phosphorimetry in pharmaceutical analysis].

Applications of phosphorimetry including solid substrate phosphorescence, liquid medium phosphorescence, low temperature phosphorescence and phosphorescence sensors were reviewed in pharmaceutical analysis. The drugs involved here included the varieties of alkaloid, Chinese traditional medicine, tetracyclines, quinolone, riboflavin, anticancer medicine, naphazoline, naproxen, nafronyl dipyridamole and so on. Solid surface phosphorimetry is characterized by sample volume of microliter grade, simple and fast operation procedures in pharmaceutical analysis. The combination of liquid phosphorescence with flow injection analysis and chemosensing technique has good advantages in fast, continuous and on-line monitoring of medicines. Modified low temperature phosphorimetry still remains its high sensitivity and overcomes some disadvantages in the procedures. Phosphorimetry will be more widely applied to pharmaceutical analysis as the development of sensitive and quenching, energy transfer, derivative and immunization luminescence.

Alkaloids↗
PubMed2000

Potentiometric flow-injection determination of vitamin C and glutathione with a chemically prepared tubular silver electrode.

This paper describes the preparation and use of a tubular electrode by means of chemical pretreatment of a silver tube with mercuric (II) chloride solution and iodide solution in flow injection analysis (FIA). The electrode was used as a potentiometric sensor for the indirect determination of vitamin C and glutathione in a carrier stream containing iodine. A simple FIA system that consists of a peristaltic pump, an injection T valve, a tubular silver electrode and a saturated calomel reference electrode (SCE) was used. Some typical FIA parameters such as flow rate, tube length, sample volume and composition of the carrier stream were varied. After optimisation of these parameters, the electrode was further characterised by a constant linear response within the concentration range for the vitamin C between 5 x 10(-5) and 5 x 10(-3) M at the slope of 60.5 +/- 1.0 mV/p (vitamin C). Glutathione has a linear concentration range between 5 x 10(-5) and 10(-2) M at a slope of 55.2 +/- 1.0 mV/p (glutathione). The experimental slope was in good agreement with the theoretical values. Some pharmaceutical products containing vitamin C were also tested. These results can be compared to the results obtained by the standard volumetric method for the determination of vitamin C and are also in good agreement with values declared by pharmaceutical manufacturers.

Ascorbic Acid↗
PubMed1997

Determination of lignocaine hydrochloride by ion-pairing flow injection with piezoelectric detection.

A rapid and simple method for the determination of lignocaine hydrochloride by ion-pairing flow injection analysis was developed. It is based on the formation of an ion pair between lignocaine hydrochloride and sodium dodecyl phenylsulfonate and piezoelectric detection. The calibration curve was linear between 0.01 and 2.00 mg ml-1, with a detection limit of 8 micrograms ml-1, an RSD of 0.29% (10 replicates) and a sampling frequency of 120 h-1. The proposed method was satisfactorily applied to the determination of lignocaine hydrochloride in pharmaceutical preparations.

Flow Injection Analysis↗