Roberto A. Olsina

Cloud point extraction, preconcentration and spectrophotometric determination of erbium(III)-2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol

The extraction and preconcentration of metal chelates via surfactant-mediated phase separation was studied. The effects on extraction parameters of several experimental variables were evaluated. A successive approximation method, using a least-squares computer program, was employed for the calculation of partition and acid dissociation constants of the chelating reagent. A new, high-sensitive and low-cost methodology for the determination of Er(III)-2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol — with the nonionic surfactant, polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5), with a cloud point extraction step prior to absorptiometric determination — was developed and optimized. Under the optimal experimental conditions, the molar absorptivity was 1.27 × 105 1 mol−1cm−1. Calibration plot of absorbance (584 nm) vs. concentration was linear within the range 0.02–2 mg l−1 Er(III). The lower limit of detection (LOD) was 1.48 × 10−7 mol l−1. The proposed procedure was successfully applied to the determination of Er(III) in synthetic samples, reproducing superconducting materials and permanent magnets.

Monitoring the elimination of gadolinium-based pharmaceuticals. Cloud point preconcentration and spectrophotometric determination of Gd(III)-2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol in urine

An extraction methodology based on cloud point phase separation of non-ionic surfactants has been developed for the preconcentration of ppb amounts of gadolinium in urine as a prior step to its determination by an absorptiometric procedure. A method based on the formation of complexes with 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol was used for the extraction of Gd(III) in the surfactant-rich phase of non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5). The variables affecting the combined preconcentration-absorptiometric method have been evaluated and optimised. The extraction efficiency, linearity, and the limit of detection (LOD) of the method were determined. The optimised procedure was applied to determine total and free Gd(III) contents in real urine samples of patients after the NMR imaging diagnostic examination with contrast agent.

On-line cloud point preconcentration and determination of gadolinium in urine using flow injection inductively coupled plasma optical emission spectrometry

The on-line incorporation of cloud point extraction (CPE) into flow injection analysis (FIA) associated with ICP-OES for determining metal ions is presented and evaluated. The methodology is based on the complexation of Gd(III) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of non-ionic micelles of PONPE-7.5. The micellar system containing the complex was thermostated at 25 °C and loaded into the FIA manifold at a flow rate of 5 ml min−1, and the surfactant rich-phase was retained in a micro-column packed with cotton, at pH 9.2. The surfactant-rich phase was eluted with 4 mol l−1 nitric acid at a flow rate of 1.5 ml min−1 directly into the nebulizer of the plasma. An enhancement factor of 20 was obtained for the preconcentration of 10 ml of sample solution. The detection limit for the preconcentration of 10 ml of aqueous solution of Gd was 40 ng l−1. nThe precision (RSD) for 10 replicate determinations at the 2.0 µg l−1 Gd level was 1.9%, calculated from the peak heights obtained. The calibration graph using the preconcentration system for gadolinium was linear, with a correlation coefficient of 0.9997 at levels near the detection limit up to at least 50 µg l−1. The method was successfully applied to the determination of gadolinium in urine.

Assessment of trace aluminium content in parenteral solutions by combined cloud point preconcentration—flow injection inductively coupled plasma optical emission spectrometry

A micelle-mediated phase separation without added chelating agents to preconcentrate trace levels of aluminium in parenteral solutions as a prior step to its determination by flow injection inductively coupled plasma optical emission spectrometry has been developed. The enrichment step is based on the cloud point extraction of aluminium with the non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5). The chemical variables affecting the sensitivity of the extractive-spectrometric procedure were studied in detail. After optimization, a preconcentration factor of 200 and a %E higher than 99.9 were achieved. The detection limit (DL) value of aluminium for the preconcentration of 50 ml of parenteral solution was 0.25 microgl(-1). The calibration graph using the preconcentration system for aluminium was linear with a correlation coefficient of 0.9997 at levels near the DLs up to at least 200 microgl(-1). The developed hyphenated assay, which thoroughly satisfies the typical requirements for pharmaceutical control processes, is appropriate to monitor the aluminium concentration in parenteral nutrition.

On-line preconcentration of cobalt in drinking water using a minicolumn packed with activated carbon coupled to electrothermal atomic absorption spectrometric determination

Abstract An on-line flow injection preconcentration-electrothermal atomic absorption spectrometry method is developed for trace determination of cobalt in drinking water samples by sorption on a conical minicolumn packed with activated carbon at pH 9.5. The cobalt was eluted from the minicolumn with 10% (v/v) nitric acid. An enrichment factor of 190-fold for a sample volume of 10 ml was obtained. The detection limit (DL) value for the preconcentration method proposed was 5 ngxa0l −1 . The precision for 10 replicate determinations at the 50 ngxa0l −1 Co level was 4.7% relative standard deviation. The calibration graph using the preconcentration system for cobalt was linear with a correlation coefficient of 0.9993 at levels near the DLs up to at least 0.35 μgxa0l −1 . The method was successfully applied to the determination of cobalt in drinking water samples.

Multielemental analysis in vegetable edible oils by inductively coupled plasma mass spectrometry after solubilisation with tetramethylammonium hydroxide.

Trace metals have negative effects on the oxidative stability of edible oils and they are important because of possibility for oils characterisation. A single-step procedure for trace elemental analysis of edible oils is presented. To this aim, a solubilisation with tetramethylammonium hydroxide (TMAH) was assayed prior to inductively coupled plasma mass spectrometry detection. Small amounts of TMAH were used, resulting in high elemental concentrations. This method was applied to edible oils commercially available in Argentine. Elements present in small amounts (Cu, Ge, Mn, Mo, Ni, Sb, Sr, Ti, and V) were determined in olive, corn, almond and sunflower oils. The limits of detection were between 0.004 μg g(-1) for Mn and Sr, and 0.32 μg g(-1) for Sb. Principal components analysis was used to correlate the content of trace metals with the type of oils. The two first principal components retained 91.6% of the variability of the system. This is a relatively simple and safe procedure, and could be an attractive alternative for quality control, traceability and routine analysis of edible oils.

A New Fluorescent Assay for Enalapril Maleate

A new spectrofluorimetric method for the enalapril maleate monitoring was studied. Enalapril maleate was found to be highly photolabile. This drug was evaluated according to photodegradation assay at pH 2.5 and 6. Enalapril maleate was exposed to UVA–UVB radiations. Under these specific conditions was found as degradation product, the diketopiperazine. The modification of the fluorescent properties of enalapril maleate in solution after exposure UV-radiation and the degradation mechanisms were studied. The photodegradation was followed by the developed spectrofluorimetric assay.

Rapid and sensitive HILIC–MS/MS analysis of carnitine and acetylcarnitine in biological fluids

AbstractMonitoring carnitine and acetylcarnitine levels in biological fluids is a powerful tool for diagnostic studies. Research has recently shown that the analysis of carnitine and related compounds in clinical samples can be accomplished by different analytical approaches. Because of the polar and ionic nature of the analytes and matrix complexity, accurate quantitation is a highly challenging task. Thus, sample processing factors, preparation/cleanup procedures, and chromatographic/ionization/detection parameters were evaluated. On the basis of the results obtained, a rapid, selective, sensitive method based on hydrophilic interaction liquid chromatography–tandem mass spectrometry for the analysis of carnitine and acetylcarnitine in serum and urine samples is proposed. The matrix effect was assessed. The proposed approach was validated, the limits of detection were in the nanomolar range, and carnitine and acetylcarnitine levels were found within the micromolar range in both types of sample.n FigureExperimental workflow for the carnitine and acetylcarnitine determination in biological samples by HILIC-MS/MS

A novel and rapid method for determination of natamycin in wines based on ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry: validation according to the 2002/657/EC European decision

A novel, simple, and rapid reversed-phase liquid chromatography–tandem mass spectrometric methodology was developed for the analysis of natamycin in wine samples. Natamycin was protonated to form singly charged ions in an electrospray positive ion mode. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring (MRM) of three fragment ion transitions (666.3u2009→u2009648.2, 666.3u2009→u2009503.3, and 666.3u2009→u2009485.2) to provide a high degree of sensitivity and specificity. Chromatographic separation was performed on a rapid resolution column using a mobile phase consisting of an acetonitrile/water mixture with a total run time of 5.0xa0min. After only filtration as pretreatment, the sample was injected into the chromatographic system. The proposed method was validated in terms of selectivity, trueness, precision, decision limit (CCα), and detection capability (CCβ) according to 2002/657/EC Commission decision. The values for trueness, reported as bias (%), agreed with those established by the aforementioned document. Repeatability (intraday variability) values were 12.37% at a concentration of 1.0xa0μgxa0L−1 and 8.99–4.19% at concentrations between 2.5 and 10xa0μgxa0L−1. The overall within-laboratory (interday variability) reproducibility was 15.47% at a concentration of 1.0xa0μgxa0L−1, which was significantly lower than the indicative value reported in the EU decision. The results indicated that the proposed approach is a sensitive, fast, reproducible, and robust methodology suitable for the analysis of natamycin levels in wine samples.

Analysis of nordihydroguaiaretic acid in Larrea divaricata Cav. extracts by micellar electrokinetic chromatography.

INTRODUCTIONnLarrea divaricata Cav. is a common shrub used in folk medicine to treat a variety of diseases. The main product extracted from this bush is nordihydroguaiaretic acid (NDG), which is a potent antioxidant.nnnOBJECTIVEnIn this paper we propose a novel method for the quantification of NDG in different extracts of Larrea divaricata. The concentration of NDG in two different aqueous extracts (I and D) and an ethanolic extract (Eet) was analysed, in order to evaluate the safe use of the extracts for pharmacological purposes.nnnMETHODOLOGYnMicellar electrokinetic chromatography (MEKC) was performed under the following conditions: the background electrolyte used consisted of 20 u2009mm phosphate buffer (pH 7.5), 10 u2009mm sodium dodecyl sulphate and 10% acetonitrile.nnnRESULTSnThe limits of detection and quantitation of NDG were 4.54 × 10(-4) and 10.6 × 10(-4) u2009 mg/mL, respectively. The concentration of this acid in both aqueous extracts was within the safe levels. However, the decoction must be used carefully because the concentration of the acid was almost over the recommended limit. In the case of ethanolic extracts, the amount of NDG was above the safe concentration, which is in agreement with the solubility of the active compound in ethanol.nnnCONCLUSIONSnThe conclusions of this study demonstrate that most of these plant extracts should be used with care, especially those which are used with medicinal purposes. This is the first research on the quantification of NDG using MEKC in jarilla extracts.