Rosario Blanc

Determination of ciprofloxacin in human urine and serum samples by solid-phase spectrofluorimetry

A method for the determination of trace amounts of ciprofloxacin has been developed, based on solid-phase spectrofluorimetry. The relative fluorescence intensity of ciprofloxacin fixed on Sephadex SP C-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. The wavelengths of excitation and emission were 272 and 448 nm, respectively. Using a sample volume of 1000 ml, the linear concentration range of application was 0.3-10.0 ng.ml(-1) of ciprofloxacin, with a R.S.D. of 1.2% (for a level of 4.0 ng.ml(-1)) and a detection limit of 0.1 ng.ml(-1). The method was applied to the determination of ciprofloxacin in human urine and serum samples. It was validated applying the standard addition methodology and using HPLC as a reference method. Recovery levels of the method reached 100% in all cases.

Simultaneous determination of naproxen, salicylic acid and acetylsalicylic acid by spectrofluorimetry using partial least-squares (PLS) multivariate calibration

Determination of naproxen, salicylic acid and acetylsalicylic acid has been carried out in mixtures of up to three components by recording emission fluorescence spectra between 300 and 520 nm with an excitation wavelength of 290 nm. The excitation-emission spectra of these compounds are strongly overlapped, which does not permit their direct determination without previous separation by conventional methodologies. Here, a method is proposed for the determination of these chemicals by the use of a full-spectrum multivariate calibration method, partial least-squares (PLS). The experimental calibration matrix was designed with 18 samples. The concentrations were varied between 0.1 and 1.0 mug ml(-1) for naproxen, 0.5 and 5.0 mug ml(-1) for salicylic acid and from 2.0 to 12.0 mug ml(-1) for acetylsalicylic acid. The cross-validation method was used to select the number of factors. To check the accuracy of the proposed method, the optimized model, obtained using PLS-1, was applied to the determination of these compounds in pharmaceuticals and human serum samples previously spiked with different amounts of each chemical.

Determination of polyphenolic compounds in wastewater olive oil by gas chromatography-mass spectrometry

A simple and sensitive method for the determination of 21 polyphenolic compounds in wastewater from olive oil production plants is proposed. The method involves a liquid-liquid microextraction (LLME) procedure with ethyl acetate followed by a silylation step. Identification and quantification have been performed by gas chromatography-mass spectrometry (GC-MS). MS measurements were carried out using selected ion monitoring mode (SIM). alpha-Naftol was used as internal standard. The proposed method was applied to the determination of these compounds in wastewater from an olive oil production factory in Jaén (Spain) at concentration levels ranging from 1.0 to 75.0mugml(-1) for each compound. The autodegradation process by own microbiota in samples collected in three different points of the factory was also studied. The method was validated by a recovery assay with spiked samples.

On the estimate of blanks in differential pulse voltammetric techniques : application to detection limits evaluation as recommended by IUPAC

A new method to obtain the signal associated with a blank in differential pulse voltammetry and stripping voltammetry techniques is applied. The signal assigned to the blank is obtained by direct integration of the background noise extrapolated values of the base-peak width at different concentrations in order to obtain the zero concentration. Detection limits more amenable to a statistical evaluation are thus implemented, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).

Determination of 1-naphthylacetic acid in commercial formulations and natural waters by solid-phase spectrofluorimetry

A method for the determination of trace amounts of 1-naphthylacetic acid (NAA) has been developed, based on solid-phase spectrofluorimetry. The relative fluorescence intensity of NAA fixed on Sephadex QAE A-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. The wavelengths of excitation and emission were 280 and 336 nm, respectively. The applicable concentration range was from 0.3 to 18 ng/ ml, with a relative standard deviation of 1.4% (for a level of 9 ng/ml) and a detection limit of 0.09 ng/ml. The method was applied to the determination of NAA in commercial formulations and natural waters. The method is more sensitive and selective than other methods described in the literature.

Determination of Trace Amounts of Molybdenum in Waters with Carminic Acid by Ion-Exchange Spectrofluorimetry

Abstract A spectrofluorimetric method for the determination of trace amounts of molybdenum was developed, based on ion-exchange spectrofluorimetry (IEF). Molybdenum reacts with carminic acid to give a red fluorescent complex, which was fixed on a dextran-type anion-exchange gel. The fluorescence of the gel, packed on a 1-mm quartz cell, was measured directly using a solid-surface attachment. The applicable concentration range was from 1.0 to 15.0 μg-l-1, with a relative standard deviation of 1.4 % and a detection limit of 0.3 μg-l-1. The method was applied to the determination of molybdenum in natural waters. This method is more sensitive and selective than that using carminic acid alone.

Simultaneous spectrofluorimetric determination of 1-naphthylacetic acid and 1-naphthalenacetamide in commercial formulations and soil samples

A spectrofluorimetric method for the simultaneous determination of 1-naphthylacetic acid (NAA) and 1-naphthalenacetamide (NAD) was developed. The sample solution containing both analytes was equilibrated with Sephadex QAE A-25 gel by agitation and then only NAA was fixed on gel, while the remaining NAD stayed in the solution. The relative fluorescence intensity of NAA fixed on Sephadex QAE A-25 gel was measured directly after packing the gel beads in a 1-mm silica cell, using a solid-phase attachment. NAD was determined spectrofluorimetrically in the solution. The wavelengths of excitation and emission chosen for the determination of NAA were 280 and 336 nm, respectively, and for NAD determination 222 and 337 nm, respectively. The applicable concentration range was 12-60 ng ml(-1) for NAA and 6-120 ng ml(-1) for NAD. The detection limit was 3 ng ml(-1) for NAA and 2 ng ml(-1) for NAD. The method was applied satisfactorily to the determination of NAA and NAD in commercial formulations of phytohormones and soil samples.

Determination of alcohol sulfates in wastewater treatment plant influents and effluents by gas chromatography-mass spectrometry.

In the present paper, we developed an accurate method for the analysis of alcohol sulfates (AS) in wastewater samples from wastewater treatment plant (WWTP) influents and effluents. Although many methodologies have been published in the literature concerning the study of anionic surfactants in environmental samples, at present, the number of analytical methodologies that focus in the determination of AS by gas chromatography in the different environmental compartments is limited. The reason for this is that gas chromatography-mass spectrometry (GC-MS) technique requires a previous hydrolysis reaction followed by derivatization reactions. In the present work, we proposed a new procedure in which the hydrolysis and derivatization reactions take place in one single step and AS are directly converted to trimethylsilyl derivatives. The main factors affecting solid-phase extraction (SPE), hydrolysis/derivatization and GC-MS procedures were accurately optimised. Quantification of the target compounds was performed by using GC-MS in selected ion monitoring (SIM) mode. The limits of detection (LOD) obtained ranged from 0.2 to 0.3 μg L(-1), and limits of quantification (LOQ) from 0.5 to 1.0 μg L(-1), while inter- and intra-day variability was under 5%. A recovery assay was also carried out. Recovery rates for homologues in spiked samples ranged from 96 to 103%. The proposed method was successfully applied for the determination of anionic surfactants in wastewater samples from one WWTP located in Granada (Spain). Concentration levels for the homologues up to 39.4 μg L(-1) in influent and up to 8.1 μg L(-1) in effluent wastewater samples.

Determination of alcohol sulfates and alcohol ethoxysulfates in marine and river sediments using liquid chromatography-tandem mass spectrometry

A novel and successful method has been developed for the identification and quantification of alcohol sulfates (AS) homologues and alcohol ethoxysulfates (AES) ethoxymers in marine and river sediment samples. The method involves the extraction of 5.00 g of dry sample with methanol using pressurized liquid extraction (PLE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). 2-Octylbenzene sulfonic acid sodium salt (2ØC8-LAS) was used as internal standard. The analytical methods were applied to marine sediments collected from the coast of Almeria (South-east Spain) and river sediments collected from the Monachil river (Granada, South-east Spain). For AS homologues, the found limits of detection were 0.04-0.08 μg g(-1) for marine and river sediments. For AES ethoxymers, the found limits of detection were 0.03-0.09 μg g(-1) and 0.06-0.22 μg g(-1) for marine and river sediments, respectively. The highest concentrations of AS and AES were found in river sediment samples. Significant differences were also observed between the behavior of short-chain compounds (C12) and long-chain compounds (C14 to C18). The influence of the physic-chemical properties of water on the occurrence of these compounds was also evaluated, and differences between long- and short-chain compounds were also observed. Additionally, principal components analyses were carried out in order to study the relationship between variables and to evaluate the sources of data variability and behavior patterns. Finally, important conclusions were drawn regarding the environmental behavior of AS and AES.

A new procedure of determination of alcohol sulfates and alcohol ethoxysulfates in agricultural soils

The number of analytical methodologies that focus in the determination of alcohol sulfates (AS) and alcohol ethoxysulfates (AES) in terrestrial environment is very limited. In the present work, a new methodology to improve the extraction and determination of AS and AES in agricultural soil samples has been developed. Prior to instrumental analysis, an extraction procedure using pressurized liquid extraction with methanol (PLE) was carried out in order to obtain the highest recoveries and improve sensitivity. The most influential variables affecting the PLE procedure were optimized. Then, the separation and quantification of analytes were performed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The limits of detection (LOD) ranged from 0.03 to 0.08μgg(-1) for AS homologues and in the case of AES ethoxymers from 0.03 to 0.09μgg(-1) for AES-C12Ex and from 0.03 to 0.08μgg(-1) for AES-C14Ex. Matrix-matched calibration was used. Trueness was evaluated by using a spike recovery assay with spiked blank samples, and the recoveries ranged from 98.3% to 101.0% for AS and from 99.9% to 100.1% for AES. The method was satisfactorily applied in a field study designed to evaluate the environmental behavior of these compounds in agricultural soil.