A. Segura Carretero

Determination of imidacloprid and its metabolite 6-chloronicotinic acid in greenhouse air by application of micellar electrokinetic capillary chromatography with solid-phase extraction.

A method is described for the analysis of the insecticide imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] and its metabolite 6-chloronicotinic acid by micellar electrokinetic chromatography with diode-array detection at 270 and 227 nm, respectively. The best results were obtained using sodium dodecyl sulphate at a concentration of 60 mM and a running buffer of NH4Cl/NH3 at 15 mM (pH 8.5). The selection of instrumental parameters such as voltage at 30 kV with an injection time of 20 s gave the best resolution with an analysis time of less than 6 min. The method yields similar sensitivity for the parent compound and for the metabolite, with detection limits of 0.71 and 1.18 microg/ml for imidacloprid and 6-chloronicotinic acid, respectively. The sampling and analysis of these two pesticides in greenhouse air was carried out using personal samplers connected to XAD-2 cartridges as sampling media, investigating the dissipation of analytes in a 24-h period after their application.

A sensitive fluorescence optosensor for analysing propranolol in pharmaceutical preparations and a test for its control in urine in sport

We describe a simple and selective method for analysing propranolol and a sensitive test for its control in urine. A flow-through fluorescence optosensor based on on-line immobilization in a non-ionic-exchanger (Amberlite XAD-7) solid support in a continuous flow was used in both cases. Determination was made in 5 mM H(2)PO(4)(-)/HPO(4)(2-) buffer solution at pH 6 at a working temperature of 20 degrees C. Fluorescence intensities were measured at lambda(ex/em) = 300/338 nm with a response time of 80 s, thus obtaining a linear concentration range of between 0 and 250.0 ng ml(-1) with a detection limit of 1.3 ng ml(-1), an analytical sensitivity of 6.0 ng ml(-1) and a standard deviation of 2.40% at a 150 ng ml(-1) concentration level for propranolol. We also propose a test to detect propranolol in urine with a linear concentration range between 0 and 100.0 ng ml(-1), a detection limit of 0.2 ng ml(-1), an analytical sensitivity of 1.0 ng ml(-1), and a standard deviation of 0.84% at a 75 ng ml(-1) concentration level. The effect of proteins presents in urine samples were evaluated. The two proposed methods were satisfactorily applied to commercial formulations and urine samples respectively.

Use of calixarene compounds as selectivity modifiers in capillary electrophoresis separations

The use of calixarene compounds as selectivity modifiers and potassium bromide as electrolyte in capillary electrophoresis (CE) was studied. Calixarenes are macrocyclic oligomers having the shape of a conical vase whose inner cavity can accommodate various guest molecules. These compounds absorb in the ultraviolet region, with maxima at approximately 204 nm, and can be employed for the indirect determination of various types of compounds. The use of water soluble sulphonated calixarene as mobile phase in combination with different salts allowed us to develop electrophoretic methods for the determination of special compounds which are transparent in the UV region. The potential of this buffer was assessed by separating various groups of analytes including amino acids, biogenic amines and inorganic cations and anions. A system consisting of seven amino acids, used as model compounds, was chosen to optimize the buffer. The different instrumental variables affecting sensitivity and resolution of the mixture were carefully optimized.

Fluorometric Determination of Folic Acid Based on Its Reaction With The Fluorogenic Reagent Fluorescamine

Abstract A spectrofluorimetric analysis of folic acid (pteroylglutamic acid) using fluorescamine as a fluorogenic reagent, has been developed. The analytical parameters for optimal reaction and sensitivity (pH, fluorescamine concentration, temperature, reaction time), have been studied. The present method may be employed for the analysis of small amounts of folic acid (< 20 ppb), without interferences from other compounds; the selectivity being increased by the application of the synchronous derivative technique to normal fluorescence spectra. The minimum detectable quantity, using the latter technique, is estimated to be 16 ppb, with a relative standard deviation of 2.7 % (10 determinations). A soft sport beverage, containing low concentrations of the vitamin, have been satisfactorily analyzed.

The use of dansyl chloride in the spectrofluorimetric determination of the synthetic antioxidant butylated hydroxyanisole in foodstuffs.

A sensitive method is presented for the determination of the synthetic antioxidant butylated hydroxyanisole (BHA) based on the dansylation process of the phenolic hydroxy group. The fluorescence developed can be measured directly without previous extraction or chromatographic separation of the labelled fluorescent compound. It is shown the effect of numerous experimental variables affecting the fluorescence intensity and the signal-to-noise ratio of the dansyl derivative. The compound was determined over the range 0.05-5 mug ml(-1), with a relative S.D. of 3.8% (300 ng ml(-1)) and a detection limit of 52 ng ml(-1). The selectivity conferred by the dansylation reaction has permitted to avoid the interference of normally accompanying antioxidants, such as butylated hydroxytoluene (BHT), due to steric impediment. The stability of the DNS-derivative is well suited for the analysis of different foodstuffs.

Determination of the Drug Naphazoline in Pharmaceutical Preparations by Heavy Atom-Induced Room-Temperature Phosphorescence

A simple, selective, and sensitive heavy atom-induced room-temperature phosphorimetric method (HAI-RTP) is described for the determination of naphazoline (NPZ) in pharmaceutical preparations. The phosphorescence signals are a consequence of intermolecular protection when analytes are, exclusively, in the presence of a heavy atom salt and sodium sulfite as an oxygen scavenger to minimize RTP quenching. This variable selection constitutes the basis of the HAI-RTP method for the determination of naphazoline (detection limit 43.5 ng/mL; 2.39% relative standard deviation at 500 ng/mL). The method has been applied to the analysis of pharmaceutical preparations.

Fluorimetric determination of procaine in pharmaceutical preparations based on its reaction with fluorescamine

A simple spectrofluorimetric analysis of a local anaesthetic named procaine using a specific labelling reagent for primary amino groups, has been developed. Because procaine shows very weak native fluorescence, the technique of spectrofluorimetry has been very much limited for its determination. A detail study of the variables affecting the derivatisation reaction (pH, fluorescamine (FC) concentration, temperature, reaction time), have minuciously been studied. The minimum detectable quantity is estimated as 7.7 ng ml(-1), with a relative standard deviation of 2.16% (ten determinations) for a procaine concentration of 100 ng ml(-1). The present method can be employed for the analysis of procaine by direct fluorescence measurements, without the interference from other compounds. The applicability of the present methodology have been demonstrated analysing three pharmaceutical preparations containing the analyte with satisfactory results.

Simple determination of propranolol in pharmaceutical preparations by heavy atom induced room temperature phosphorescence.

The applicability of heavy atom induced room temperature phosphorescence in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulphite as oxygen scavenger, were used to obtain phosphorescent signal of propranolol in solution. Thus a new simple, rapid and selective phosphorimetric method is proposed for propranolol determination in pharmaceutical preparations. The phosphorescence intensity was measured at 492 nm exciting at 294 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 0 and 500 ng ml 1 with a detection limit of 14.4 ng ml 1 , an analytical sensitivity of 6.7 ng ml 1 and a standard deviation of 1.4% at a 300 ng ml 1 concentration level. The method has been successfully applied to the analysis of propranolol in an antidepressive pharmaceutical preparation and it was validated using standard addition methodology. # 2002 Elsevier Science B.V. All rights reserved.

Facile and selective determination of the cerebral vasodilator nafronyl in a commercial formulation by heavy atom induced room temperature phosphorimetry

This paper presents a facile and selective method for the determination of the pharmaceutical compound nafronyl using heavy atom induced room temperature phosphorimetry (HAI-RTP) as analytical technique. The determination was performed in potassium iodide 1.6 M and sodium sulphite 0.002 M at a measurement temperature of 20 degrees C. The phosphorescence intensity was then measured at lambda(exc) = 292 nm and lambda(em) = 524 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 2.7 and 250 ng ml(-1) with the detection limit of 2.7 ng ml(-1), an analytical sensitivity of 5.1 ng ml(-1) and a standard deviation of 2.17%, at a 150 ng ml (-1) concentration level. The proposed method has been satisfactorily applied to the unique Spanish commercial formulation containing nafronyl at a 100 mg level per capsule. The recovery was 108%, with a 1.7%, standard deviation of the analytical measurement. The method has been validated using standard addition methodology.

Simultaneous Determination, by Capillary Zone Electrophoresis, of Multiple Components of Different Industrial Products

Four parabens (esters of 4-hydroxybenzoic acid), effective preservatives against the growth of bacteria, yeast, and mold in numerous industrial products, have been used in this work as model compounds to demonstrate the resolving power of capillary electrophoresis (CE). The simultaneous determination of methyl-(MP), ethyl-(EP), propyl-(PP), and butylparaben (BP) was achieved by capillary zone electrophoresis (CZE) with UV diode-array detection at 294 nm. When run voltage, temperature, and electrolyte concentration and pH were optimized the most effective separation was achieved within 7 min by use of 50 cm (effective length) fused silica capillary tubing and operation at 25kV and 20°C. Background electrolyte comprising 35 mM tetraborate buffer adjusted to pH 10.0 gave the best results. The limits of detection of the optimized method ranged from 0.65 μg mL−1 for BP to 0.81 μg mL−1 for MP; the relative standard deviation was between 0.35 and 0.50%. These results showed that the method enables the determination of the four parabens in commerially available cosmetic and pharmaceutical preparations containing some of the parabens and in an unidentified canned berry fruit juice.