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PubMed2003

Flow injection determination of isoniazid using N-bromosuccinimide- and N-chlorosuccinimide-luminol chemiluminescence systems.

A chemiluminescent method for the determination of isoniazid is described. Method is based on the chemiluminescence (CL) generated during the oxidation of luminol by N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in alkaline medium. It was found that the isoniazid could greatly enhance this CL intensity when present in the luminol solution. Based on this observation, a new flow-injection CL method for the determination of isoniazid is proposed in this paper. The detection limits were 4 and 3 ng ml(-1) isoniazid for the NBS- and NCS-luminol CL systems, respectively. The relative CL intensity was linear with the isoniazid concentration in the range of 8-600 and 600-5000 ng ml(-1) for the NBS-luminol CL system, and 6-200 and 200-2000 ng ml(-1) for the NCS-luminol CL system. The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official method and demonstrated good accuracy and precision.

Bromosuccinimide↗
PubMed2003

Determination of potassium ions in pharmaceutical samples by FIA using a potentiometric electrode based on ionophore nonactin occluded in EVA membrane.

A simple and rapid method was developed for the K(+) ions determination employing a flow injection system using a flow-through electrode based on the naturally-occurring antibiotic ionophore nonactin occluded in a polymeric membrane. The nonactin ionophore was trapped in poly(ethylene-co-vinyl acetate) (EVA) matrix (40% w/w in vinyl acetate) and dispersed on the surface of a graphite-epoxy tubular electrode. The plasticizer-free all-solid-state potassium-selective electrode showed a linear response for K(+) concentrations between 5.0 x 10(-5) and 5.0x10(-2) M (r=0.9995) with a near-Nernstian slope of 51.5 mV per decade, when Tris-HCl buffer (pH 7.0;0,1 M) was employed as a carrier. The potentiometric-FIA system allows an analytical frequency of 120 samples per hour with a precision of 3.6%. The relative standard deviations (R.S.D.) for K(+) determination in pharmaceuticals samples, without any previous treatment, were lower than 4.0%, comparable to those obtained by flame photometry. Ammonium is the main analytical interference and the electrode response time was 5 s at 25 degrees C. The useful lifetime of the tubular sensor is longer than 3 months in continuous use.

Anti-Bacterial Agents↗
PubMed2003

On-line preconcentration and determination of chromium in parenteral solutions by flow injection-flame atomic absorption spectrometry.

An on-line chromium preconcentration and determination system implemented with flame atomic absorption spectrometry (FAAS) associated to flow injection (FI) was studied. For the retention of chromium, 4-(2-Thiazolylazo)-resorcinol (TAR) and Amberlite XAD-16 were used, at pH 5.0. The Cr-TAR complex was removed from the micro-column with ethanol. An enrichment factor of 50 was obtained for the preconcentration of 50 ml of sample solution. The detection limit value for the preconcentration of 50 ml of aqueous solution of Cr was 20 ng l(-1). The precision for ten replicate determinations at the 5 microg l(-1) Cr levels was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for chromium was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 microg l(-1). The method was successfully applied to the determination of chromium in parenteral solution samples.

Buffers↗
PubMed2003

A flow injection sensor for simultaneous determination of sulfamethoxazole and trimethoprim by using Sephadex SP C-25 for continuous on-line separation and solid phase UV transduction.

A flow-through sensor based on integration of spectrophotometric detection and the different kinetics of retention/elution of analytes on a solid support is proposed for the simultaneous determination of sulfamethoxazole (SMZ) and trimethoprim (TMP). The solid support (Sephadex SP C-25) fills both, a microcolumn placed on-line and the sensing microzone. The intrinsic absorbance of both compounds is monitored directly on the solid phase at 269 nm and so, no derivatization step is required. Using two alternate solutions, 10(-4) M hydrochloric acid and 0.20 M NaAc/HAc (pH 5.0) buffer, the sensor responds linearly in the measuring range of 50-250 and 10-70 microg ml(-1) with detection limits of 9.5 and 0.6 microg ml(-1) (500 microl of sample volume) for SMZ and TMP, respectively. The main advantages of the sensor are simplicity, rapidity and low reagents consumption. Its application to SMZ and TMP determination in synthetic samples and pharmaceutical preparations is demonstrated. The results obtained by the proposed method were compared with those obtained by a standard HPLC method.

Chromatography, High Pressure Liquid↗
PubMed2003

Multi-pumping flow system for the spectrophotometric determination of dipyrone in pharmaceutical preparations.

A novel flow system for the spectrophotometric determination of dipyrone with p-dimethylaminobenzaldehyde exploiting the multi-pumping approach was developed. The proposed methodology utilises several micro-pumps for propelling the involved fluids under improved mixing conditions, introducing sample/reagent aliquots and providing commuting facilities. As a consequence the multi-pumping system presents high versatility and manifold simplicity, as well as a straightforward operational control and enhanced analytical capabilities. Linearity of the analytical curve was observed within 10 and 400 mg l(-1) dipyrone (r=0.9997; n=6), results were precise (r.s.d.<0.12%; n=20) and sampling rate was 50 h(-1). Detection limit was estimated as 1 mg l(-1) dipyrone. The method was applied to pharmaceutical preparations and the results were in agreement with those obtained by the reference procedure with relative deviations within -1.7 and +2.2%.

Dipyrone↗
PubMed2003

A novel chemiluminescence method for determination of terbutaline sulfate based on potassium ferricyanide oxidation sensitized by rhodamine 6G.

This work reports a novel flow injection-chemiluminescence (FI-CL) system for determination of terbutaline sulfate, a drug for treatment of asthma and chronic obstructive pulmonary disease (COPD). It is based on the reaction of potassium ferricyanide with terbutaline sulfate in sodium hydroxide medium sensitized by the fluorescent dye rhodamine 6G. With the peak height as a quantitative parameter applying optimum working conditions, terbutaline sulfate is determined over the range of 0.01-1.2 microg ml(-1) with a detection limit of 6.7 x 10(-3) microg ml(-1). The relative standard deviation (R.S.D.) is 3.7% for 0.1 microg ml(-1) terbutaline sulfate (n = 11). The proposed method is sensitive, simple, rapid, and was applied to determination of terbutaline sulfate in pharmaceutical preparations. The possible chemiluminescence (CL) reaction mechanism was also discussed briefly.

Adrenergic beta-Agonists↗
PubMed2003

Flow-injection biamperometric direct determination of calcium dobesilate in irreversible couple system.

A flow-injection biamperometric method for direct determination of calcium dobesilate had been proposed based on biamperometric detection for irreversible couple. The detection was realized by coupling the oxidation of dobesilate at one platinum wire electrode with the reduction of MnO(4)(-) at another one with the applied potential difference of 0 V between two platinum wire electrodes. Dobesilate was determined in the range of 4.0 x 10(-6) to 1.0 x 10(-4) M with the detection limit of 8.0 x 10(-7) M (S/N=3). The relative standard derivation of 1.7% was obtained for 24 successive determinations of 4.0 x 10(-5) M dobesilate. The proposed method had been shown to be sensitive, simple and rapid.

Calcium Dobesilate↗
PubMed2003

Flow-injection spectrophotometric determination of paracetamol in tablets and oral solutions.

A flow injection method is proposed for the determination of paracetamol in pharmaceutical dosage forms. The method is based on the nitration of paracetamol with sodium nitrite, and the absorption of the reaction product is measured at 430 nm in alkaline medium. Unlike other colorimetric methods used for determination of paracetamol, this method does not require the use of heat. The influence of several operating parameters is studied. The method was applied to the determination of paracetamol in oral solutions and in tablets, alone or associated with caffeine. When the results were compared with those obtained by the official HPLC method (USP 24) the relative differences found were from 0.4 to 2.3%, with relative standard deviations below 1%.

Acetaminophen↗
PubMed2003

Trimipramine determination in pharmaceutical preparations with an automated multicommutated reversed-flow system.

In this work an automated multicommutated flow methodology was implemented for the spectrophotometric determination of trimipramine in pharmaceutical preparations by oxidation with ammonium monovanadate in acidic medium. The developed procedure exploits a new approach for sample/reagent intermixing by combining binary sampling with flow-reversal. Rather than inserting the sample as a single continuous volume the intercalation of multiple small sample and reagent aliquots, under a time-based control, created multiple reaction interfaces that promoted reaction zone homogenisation even in limited dispersion conditions. Additionally, the reaction interfaces were reversed, increasing mutual zone penetration, which contributed to a faster reaction development while assuring a low dispersion pattern. A linear range of determination was verified for trimipramine concentrations between 1.0 and 18.0 microg ml(-1) with a relative standard deviation (n=10) lower than 1.69% and a sample throughput of about 26 samples per hour. The results were in agreement with those obtained by the reference procedure with relative deviations lower then 2.37%.

Flow Injection Analysis↗
PubMed2003

Direct injection HPLC method for the determination of selected benzodiazepines in plasma using a Hisep column.

A direct plasma injection HPLC method has been developed for the determination of selected benzodiazepines (nitrazepam, clobazam, oxazepam, lorazepam). The method uses an analytical hydrophobic shielded phase (Hisep) column equipped with a Hisep guard column, are easy to perform and requires 20 ul of a filtered plasma sample. The chromatographic run time is less than 15 min using a mobile phase of 15:85 v/v acetonitrile-0.18 M ammonium acetate pH 2.5. The method is good for 175 injections before replacement of the guard column. The method was linear in the range 0.5-18 ug ml(-1) (r>0.99, n=6) for the analytes with R.S.D. less than 10.82%. Interday and intraday variability were found to be less than 14%. The limits of detection and quantitation were 0.16 (s/n>3) and 0.5 ug ml(-1) (s/n>10), respectively, for each of the four benzodiazepines.

Benzodiazepines↗
PubMed2003

Specific determination of myo-inositol in multivitamin pharmaceutical preparations by a flow injection system using a myo-inositol dehydrogenase reactor coupled with a glucose eliminating enzyme reactor.

A flow injection system for myo-inositol determination in multivitamin pharmaceutical preparations using two enzyme reactors was developed. Myo-inositol was detected using a fluorophotometer, to measure the fluorescence of NADH produced from NAD+ by a myo-inositol dehydrogenase reactor (IDR) containing myo-inositol dehydrogenase immobilized on porous glass. Enhanced interference due to excess glucose included in a multivitamin pharmaceutical preparation as a sweetener was eliminated by a glucose eliminating reactor (GER) co-immobilized with three enzymes (glucose oxidase, mutarotase and catalase). The calibration coefficient for the standard curve was 0.9993 for myo-inositol detection in the range of 1-5 microg/ml. Myo-inositol was determined even in the presence of glucose concentrations of 140-420 microg/ml. The recovery of myo-inositol added to the multivitamin pharmaceutical preparation was 99.6% (n=9).

Enzyme Reactivators↗
PubMed1997

Flow-injection spectrophotometric determination of frusemide or sulphathiazole in pharmaceuticals.

Two sensitive and fast flow-injection spectrophotometric methods are proposed for the determination of frusemide or sulphathiazole based on the formation of coloured complexes between these compounds and Pd(II) at pH 5.0 and 55 degrees C. Using the peak height as a quantitative parameter, frusemide or sulphathiazole was determined at 410 nm over the range 2.0 x 10(-5)-4.0 x 10(-4) M or 5.0 x 10(-5)-3 x 10(-4) M, respectively. The methods were applied to the determination of these sulphonamides in pharmaceuticals.

Diuretics↗
PubMed1997

Spectrophotometric methods for the determination of cephradine or ceftazidine in human urine using batch and flow-injection procedures.

Sensitive and fast spectrophotometric methods for the determination of cephradine or ceftazidine in human urine, based on the formation of compounds between these drugs and Pd(II), are described. In the batch procedures the calibration graphs resulting from the measurement of the absorbance at 330 nm is linear over the range 5.0-60.0 micrograms. ml-1 for cephradine and 3.0-60.0 micrograms ml-1 for ceftazidine. The methods were successfully adapted to FI-systems, the peak heights being proportional to cephalosporin concentration over the range 5.0-60.0 micrograms ml-1 for cephradine and 3.0-60.0 micrograms ml-1 for ceftazidine. The sampling frequency was 60 h-1 with a sample injection of 72 microliters.

Ceftazidime↗
PubMed1997

Optimization of a polarized photometric detector equipped with a split-type flow cell and its analytical application to oligo-saccharides.

A novel, non-modulated polarimeter called a polarized photometric detector (PPD) was previously described by the authors. The PPD enables the measurement of the optical rotation of chiral compounds as a change in absorbance by placing two linear polarizers on either side of a flow cell of a conventional photometric detector. The present study describes the optimization of the conditions of PPD for highly sensitive detection of saccharides. To maximize the light intensity, the light balancing filter and slit were removed from the detector (Shimadzu model SPD-10AV). These modifications resulted in an approximately 15-fold increase in the incident light intensity when the maximum current was applied to the lamp. When this intense light was transmitted through the polarizers, the signal intensity followed the theoretical equation for phase angles up to around 1 rad. If the energy of the transmitted light was less than 700 mV, however, the baseline noise was too great to determine the chiral analyte accurately. Setting the phase angle between two polarizers at 50 degrees and the detection wavelength at 400 nm provided the most suitable conditions. This detector was applicable for the determinations of oligosaccharides in foodstuffs separated by HPLC using gradient elution.

Flow Injection Analysis↗
PubMed1997

Potentiometric flow injection determination of serum bromide in patients with epilepsy.

A flow injection system was constructed using a bromide-selective electrode and used to determine serum bromide in patients with epilepsy. A 10-microliter serum sample was injected into a carrier stream flowing at 0.12 ml min-1. Potential changes and bromide concentrations were linearly related in the range 3-50 mM. The lower limit of detection for serum bromide was 1 mM and this electrode sensitivity spanned the entire concentration range required for bromide therapy (9-24 mM). The results compared favourably with those obtained by colorimetry.

Autoanalysis↗
PubMed1997

Flow-injection biamperometric determination of epinephrine.

A flow-injection manifold is proposed for the determination of epinephrine. The experimental procedure is based on the indirect biamperometric detection of the drug by using Fe(III)-Fe(II) as an indicating redox system and a flow-through detector with two polarized Pt wire electrodes. The calibration graph is linear over the range 0.3-20 micrograms ml-1 of epinephrine. The relative standard deviation for the determination of 10 micrograms ml-1 of epinephrine is 1.5% (n = 25) and the sample throughput is 153 h-1. The method was applied to the determination of epinephrine in two commercially available pharmaceutical preparations.

Electrochemistry↗
PubMed1997

Flow extraction spectrophotometric method for the determination of diclofenac sodium in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of diclofenac was carried out by liquid-liquid extraction using acridine yellow with a flow system. The determination of diclofenac sodium in the range of 3-80 micrograms ml-1 was possible with a sampling frequency of 40 samples h-1. The method was satisfactorily applied to the determination of diclofenac in pharmaceutical preparations.

Aminoacridines↗