Development of hybrid monoliths incorporating metal-organic frameworks for stir bar sorptive extraction coupled with liquid chromatography for determination of estrogen endocrine disruptors in water and human urine samples.

A novel coating based on hybrid monolith with metal-organic framework (MOF) onto conventional Teflon-coated magnetic stir bars was developed. For this purpose, the external surface of the Teflon stir bar was firstly vinylized in order to immobilize a glycidyl methacrylate (GMA)-based polymer onto the magnet. Then, an amino-modified MOF of type MIL-101 (NH2-MIL-101(Al)) was covalently attached to the GMA-based monolith. After the synthesis process, several parameters affecting extraction of target estrogens by stir bar sorptive extraction (SBSE) including pH, ionic strength, extraction time, stirring rate, desorption solvent, and desorption time were also investigated. The resulting hybrid monolith was evaluated as SBSE sorbent for extraction of three estrogens (estrone, 17ß-estradiol, estriol) and synthetic 17ß-ethinylestradiol from water and human urine samples followed by HPLC with fluorescence detection (excitation and emission wavelengths, 280 and 310 nm, respectively). Under the optimal experimental conditions, the analytical figures of the method were established, achieving satisfactory limits of detection in the range of 0.015-0.58 µg L-1, recovery results ranging from 70 to 95% with RSD less than 6%, and precision values (intra- and inter-extraction units) below 6%.

Identification of prometon, deisopropylprometon, and hydroxyprometon in groundwater by high resolution liquid chromatography/mass spectrometry.

Prometon, a major soil sterilant, and its main transformation products, deisopropylprometon (N(2)-isopropyl-6-methoxy-1,3,5-triazine-2,4-diamine) and hydroxyprometon (4,6-bis(isopropylamino)-1,3,5-triazin-2-ol), were identified as the dominant triazine herbicides in groundwater samples from 51 locations in Colorado, USA, over a two-year time period. They were concentrated from water by solid phase extraction and detected using an ultrahigh pressure, liquid chromatography-quadrupole time of flight tandem mass spectrometry (UHPLC/QTOF-MS). The transformation products, deisopropylprometon and hydroxyprometon, were confirmed using MS-MS experiments. An original strategy was applied to form the degradation standards for deisopropylprometon and hydroxyprometon, which consisted of photo-degradation of prometon followed by MS-MS analysis. The concentration of prometon ranged from the detection limit of 3 ng·L(-1) to 87 ng·L(-1), hydroxyprometon ranged up to 50 ng·L(-1), and deisopropylprometon up to 100 ng·L(-1), with a frequency of detection of 80%, which was greater than the other triazines detected in the groundwater samples. A new ratio is proposed for prometon degradation called the "deisopropylprometon to prometon ratio" or the DIP ratio, as an indicator of prometon residence time in groundwater. Furthermore, these data suggest that prometon is more of an issue for groundwater contamination in urban areas rather than agricultural areas.

New method for the determination of carbamate and pyrethroid insecticides in water samples using on-line SPE fused core column chromatography.

A new HPLC column-switching method using large volume sample injection and fused-core columns for on-line solid phase extraction have been developed for the determination of the following carbamates and pyrethroids: aldicarb, carbaryl, pirimicarb, carbofuran, kadethrin, flumethrin, fenpropathrin, fenoxycarb, tau-fluvalinate and fenvalerate, in surface water samples. Sudan I was used as internal standard. The proposed method was performed using 100 µl sample injection followed by an on-line solid phase extraction procedure and finally the compounds were identified and quantified by liquid chromatography with ultraviolet detection. The separation was carried out on C-18 reversed phase column based on fused-core particle technology. The influence of the injected sample volume, the variables affecting to SPE process and the conditions for the separation on an analytical column, were studied and optimized. The limits of detection ranged from 5.5 to 8.9 µg L(-1), and limits of quantification from 18.4 to 29.7 µg L(-1), while inter- and intra-day variability was under 15%. This new analytical procedure was satisfactorily applied for the determination of these organic pollutants in surface water samples located in Czech Republic. Concentration levels were found for some of these pollutants up to 26.11 µg L(-1) in the river Elbe and up to 34.53 µg L(-1) in the closed lakes samples.

Fluorimetric SIA optosensing in pharmaceutical analysis: determination of paracetamol.

The coupling of sequential injection analysis (SIA) and fluorimetric solid phase transduction is here applied to the determination of paracetamol in pharmaceuticals. The reaction product between the analyte and sodium nitrite in acidic medium is inserted, after alkalinization, in the system. This product is transitorily retained on the active solid sensing phase (the anionic solid support QAE A-25) developing its native fluorescence signal, which is measured at 325/430 nm for the excitation and emission wavelengths respectively. The described system is linear within the range 6.6-80 microg ml(-1), with a 2 microg ml(-1) detection limit and a 2.5% R.S.D (n=10). The proposed fluorimetric SIA optosensor has been applied to the determination of paracetamol in several pharmaceutical preparations, obtaining satisfactory results.

Fluorescence optosensing implemented with sequential injection analysis: a novel strategy for the determination of labetalol.

The coupling of sequential injection analysis and optosensing has been developed for the first time. It has been applied to the determination of labetalol in both pharmaceuticals and urine samples, with the analytical signal (native fluorescence) being monitored directly on sensing zone microbeads. The solid support used was the nonionic silica gel C18, using 20% methanol-water (v:v) as a carrier. By using a 1.5-ml sample volume, we achieved a detection limit of 3.3 ng ml-1. This sensitivity allowed the determination of the compound in urine samples. A recovery study was carried out at the labetalol levels usually found in urine after pharmaceuticals administration, and recovery percentages close to 100% were obtained. The relative standard deviation was 3.4% for 100 ng ml-1 labetalol. No pretreatment was needed for urine samples, only an appropriate dilution, therefore minimizing the time required per sample analysis. In addition, the determination of the analyte was also carried out in one pharmaceutical, with a satisfactory result being obtained.

Automation of simultaneous release tests of two substances by sequential injection chromatography coupled with Franz cell.

This presented paper deals with a methodology for the separation and simultaneous determination of two active substances in topical pharmaceutical formulation composed of lidocaine (L) and prilocaine (P). The methodology described is based on the sequential injection chromatography (SIC) with UV detection. Monolithic Column Chromolith Flash RP-18, 25mmx4.6mm (Merck, Germany) was used. Separation was performed using elution with binary mobile phase composed of acetonitrile-phosphate buffer 0.05M (40:80 (v/v))+0.01% triethylamine (adjusted to pH 7.1 with H(3)PO(4)) at a flow rate of 0.6mlmin(-1). The analysis duration was <7min. The method was linear over the range of 2.5-200mgl(-1) with a detection limit of 0.25mgl(-1) for both substances. The system was then coupled with Franz cell. Fully automated system for the in vitro release testing of semisolid dosage forms based on sequential injection analysis (SIA) was developed. Simultaneous measurement of L and P release was done by this system. Samples were taken in 10.5min intervals during 4h of the release test. Each test was followed by calibration with five standard solutions. Receiving medium was replenished automatically by the system.

Determination of rhodamine 123 by sequential injection technique for pharmacokinetic studies in the rat placenta.

The sequential injection (SIA) technique was applied in pharmacokinetic studies of the transporter-mediated passage of a model substrate, rhodamine 123 (Rho123), through the dually perfused rat term placenta. The method described was used for real-time monitoring of Rho123 concentrations in both the maternal and fetal compartments. Determination was processed by fluorescence detection (lambda(ex)=480 nm, lambda(em)580 nm); calibration curve was linear over the range 0.01-50 mumoll(-1) (r=0.99965), detection limit was 10 nmoll(-1) (3sigma) and RSD2% (10 readings). Transport of Rho123 was scanned under various conditions (ATP-synthesis inhibition) and several inhibitors of P-glycoprotein transporter were tested (e.g. quinidine). The advantages of the modern SIA method-an automated analytical tool providing both fast and precise analysis-were successfully demonstrated for examination of transport profiles to investigate the effect of P-glycoprotein on the placental transfer of Rho123.