L. C. Robles

Bio: L. C. Robles is an academic researcher from University of León. The author has contributed to research in topics: Pharmacokinetics & Adsorption. The author has an hindex of 5, co-authored 7 publications receiving 59 citations.

Preconcentration of beryllium on the outer membrane of Escherichia coli and Pseudomonas putida prior to determination by electrothermal atomic absorption spectrometry

Abstract: A rapid, simple and selective preconcentration method involving retention of the analyte on the outer wall of Escherichia coli and Pseudomonas putida has been developed. Several factors affecting the retention of beryllium by the outer membrane of bacterial cells were optimized. This procedure was used to preconcentrate trace amounts of beryllium prior to determination by electrothermal atomic absorption spectrometry. Both batch and immobilization techniques for the two bacteria were compared, but the former methods showed better analytical capabilities. Beryllium ions are easily retained on the outer membrane at pH 6–9 for E. coli and pH 3–10 for P. putida. The bacterial mass that retained the beryllium was centrifuged and dispersed in 3.5 mol –1 nitric acid. The resulting slurry was introduced directly into the graphite tube. The best analytical figures of merit were obtained for E. coli using a slurry sampling technique with a sensitivity and detection limit of 0.015 and 0.05 ng ml–1, respectively, for the platform atomization of beryllium in the absence of a chemical modifier. No interferences from the main major and minor ions of environmental interest were found. The proposed method was applied to the determination of beryllium in an environmental reference material.

Development and Validation of an RP-HPLC-PDA Method for Determination of Paracetamol, Caffeine and Tramadol Hydrochloride in Pharmaceutical Formulations

Abstract: Paracetamol (acetaminophen) (PAR), caffeine (CAF) and tramadol hydrochloride (TRA) are important drugs widely used for many clinical purposes. Determination of their contents is of the paramount interest. In this respect, a quick, simple and sensitive isocratic RP-HPLC method with photodiode array detection was developed for the determination of paracetamol, caffeine and tramadol in pharmaceutical formulations. An improved sensitive procedure was also evolved for tramadol using a fluorescence detector system. A C18 column and a mobile phase constituted by methanol/phosphate were used. LODs were found to be 0.2 μg/mL, 0.1 μg/mL and 0.3 μg/mL for paracetamol, caffeine and tramadol hydrochloride, respectively, using photodiode-array detection. Alternatively, LOD for tramadol decreased to 0.1 μg/mL with the fluorescence detector. Other notable analytical figures of merit include the linear concentration ranges, 0.8-270 μg/mL, 0.4-250 μg/mL and 1.0-300 (0.2-40) μg/mL, for the same ordered analytes (including the fluorescence detector). The proposed method was successfully applied for the quantitative determination of the three drugs in tablet dosage forms.

Living Bacterial Cells Microextraction as a Tool for Speciation of Organoseleno Compounds

Abstract: A reliable method combining a time-controlled solid phase microextraction using living bacterial cells and electrothermal atomic absorption spectrometry is proposed for the speciation of organoseleno compounds. The extraction medium consists of a Pseudomonas putida strain cultivated in a culture medium based on glucose contaminated with an organoseleno compound. The adsorption process study was derived in order to develop an analytical procedure for determining several organoseleno compounds (selenomethionine, selenourea, and selenocystamine) in samples containing other selenium species. The best detection limits for the organoseleno compounds studied are 0.1–1.5 ng ml–1. The relative standard deviations of the retention and determination procedure are 1.9–5.6%.

Pharmacokinetic behavior of doxycycline after intramuscular injection in sheep.

Abstract: Objective—To determine the pharmacokinetics of a commercial formulation of doxycycline hyclate after IM administration of a single dose to sheep. Animals—11 healthy domestic sheep. Procedures—For each sheep, doxycycline was administered as a single dose of 20 mg/kg, IM. Blood samples were obtained prior to and for 84 hours after doxycycline administration. Plasma concentrations of doxycycline were determined via high-performance liquid chromatography with UV detection. Pharmacokinetic data were analyzed with noncompartmental methods. Results—Mean ± SD values for pharmacokinetic parameters included maximum plasma concentration (2.792 ± 0.791 μg/mL), time to reach maximum plasma concentration (0.856 ± 0.472 hours), mean residence time (91.1 ± 40.78 hours), elimination half-life (77.88 ± 28.45 hours), and area under the curve (65.67 ± 9.877 μg•h/mL). Conclusions and Clinical Relevance—Results indicated that doxycycline had prolonged absorption and elimination in sheep after IM administration. A daily dose of...

Biological substrates for metal preconcentration and speciation

Abstract: This article summarizes the state of the art of metal preconcentration and speciation using biological organisms such as algae, plant-derived materials, bacteria, yeast, fungi and erythrocytes. Although biosorption has been the subject of increasing research for a variety of reasons, including its potential application in the recovery of metals from manufacturing processes, the treatment of contaminated water and the recovery of precious metals in mining operations, only recently has it been exploited for analytical measurement. Basic techniques and principles are discussed and recent developments reviewed. Special attention is given to immobilization procedures and some biosorption mechanisms are considered.

Non-chromatographic hydride generation atomic spectrometric techniques for the speciation analysis of arsenic, antimony, selenium, and tellurium in water samples—a review

Abstract: Hydride generation (HG) coupled with AAS, ICP–AES, and AFS techniques for the speciation analysis of As, Sb, Se, and Te in environmental water samples is reviewed. Careful control of experimental conditions, offline/online sample pretreatment methods employing batch, continuous and flow-injection techniques, and cryogenic trapping of hydrides enable the determination of various species of hydride-forming elements without the use of chromatographic separation. Other non-chromatographic approaches include solvent extraction, ion exchange, and selective retention by microorganisms. Sample pretreatment, pH dependency of HG, and control of NaBH4/HCl concentration facilitate the determination of As(III), As(V), monomethylarsonate (MMA), and dimethylarsinate (DMA) species. Inorganic species of arsenic are dominant in terrestrial waters, whereas inorganic and methylated species are reported in seawater. Selenium and tellurium speciation analysis is based on the hydrides generation only from the tetravalent state....