Direct resolution and quantitative analysis of flurbiprofen enantiomers using microcrystalline cellulose triacetate plates: applications to the enantiomeric purity control and optical isomer determination in widely consumed drugs.

Flurbiprofen enantiomers have very different pharmacological properties, since the (S)-(+) form has a much higher anti-inflammatory activity than the (R)-(-) isomer, the latter being responsible for very undesirable side effects, such as gastrointestinal irritation. Based on the different biological properties of flurbiprofen enantiomers, the development of chiral chromatographic methods for the control of the enantiomeric purity is a very important topic. In this study the separation of flurbiprofen enantiomers was achieved using for the first time noncommercial MCTA layers with polyvinyl alcohol as binder, which gives to these plates a mechanical stability equivalent to that of marketed ones. Baseline resolution (α = 1.31; RS = 2.0) was obtained with ethanol-acetic acid solution (pH 3.0 ± 0.1; 60:40, v/v) as eluent and a migration distance of about 14.5 cm. Under these experimental conditions, the thin-layer chromatography determination of the enantiomeric purity of the pharmacologically active (S)-(+)-flurbiprofen in the presence of 1% of the undesired (R)-(-) form was demonstrated. Moreover, the quantitative analysis of flurbiprofen enantiomers was achieved, obtaining quantification limits and detection limits of 50 and 25 ng of each enantiomer applied to the plate, respectively. The method was succesfully applied to the enantiomer determination in widely consumed drugs, obtaining results consistent with the flurbiprofen content declared in the drug facts.

Total and hexavalent chromium removal in a subsurface horizontal flow (h-SSF) constructed wetland operating as post-treatment of textile wastewater for water reuse.

In this study we investigated total and hexavalent chromium removal in an h-SSF constructed wetland (CW) planted with Phragmites australis and operating as post-treatment of effluent wastewater from an activated sludge plant serving the textile industrial district of Prato (Italy). Two measurement campaigns were carried out in 2006 and 2008-2010 in which more than 950 inlet and outlet samples were analyzed. When inlet and outlet concentrations were compared one to the other, the latter were found to be significantly lower than the former (p < 0.001); during the entire period of investigation, removal of hexavalent chromium equal to about 70% was achieved. Outlet concentrations ranged between values lower than the quantification limit (0.5 microg L(-1)) and 4.5 microg L(-1), and in all cases were therefore lower than the limit indicated for hexavalent chromium in the Italian regulation for water reuse (5 microg L(-1)). The comparison of the removal efficiencies achieved for hexavalent and trivalent chromium during the two campaigns suggested that the removal of the former can be sustained in the long term, while for the latter, the treatment efficiency is more sensitive to the age of the CW, being that it is it based on trivalent chromium retention in the reed bed.

Polycyclic aromatic hydrocarbons (PAHs) in human milk from Italian women: influence of cigarette smoking and residential area.

The presence of PAH in breast milk collected from 32 smoking and non-smoking lactating women, residing in urban and rural areas of Tuscany (Italy) was investigated. The results indicated a significant contribution of tobacco smoke to the PAH contamination of milk: the condensate contained in the cigarettes smoked daily by each subject was strongly related with the polynuclear hydrocarbon content (R(2)=0.92, P<0.005). An experiment carried out under controlled exposure conditions to cigarette smoke allowed to demonstrate that individual metabolic activity and smoking habits affect the PAH concentration in milk samples. Mothers living in rural environments showed significantly lower PAH concentrations than those observed in urban subjects. The risk evaluation due to PAH ingestion via breast milk was assessed on the basis of the acceptable daily intake of Benzo(a)pyrene in drinking water, evidencing that a hazard cannot be excluded for heavy smokers residing in urban areas.

Performance of horizontal subsurface-flow treatment wetlands in fecal bacteria removal.

This work evaluated sub-surface flow (SSF) constructed wetlands and activated sludge plant efficiency in pathogen removal. The two were also compared. The removal of fecal bacteria (total coliforms, fecal coliforms, fecal streptococci) was evaluated. Analysis was carried out during one year by determining the amount of bacteria in the inflow and the outflow of four systems: three SSF systems (two were pilot plants and one a fully operating plant) and an activated sludge plant. MPN techniques were used to determine the quantity-value of the microorganisms. Percentages of fecal bacteria removal in wetlands systems were as good as (and sometimes better than) those recorded in the activated sludge plant. Optimal values of these bacteria were obtained in the outflow of the post-treatment pilot plant: very high bacterial removal percentages (>99%) were recorded. SFS constructed wetlands are a valid solution for the final treatment of the outflow of existing plants.

Chiral separations and quantitative analysis of optical isomers on cellulose tribenzoate plates.

In this paper new cellulose tribenzoate/gypsum layers in the ratio up to 8/1 (w/w) were investigated for the chiral resolution of closely related aromatic ketones (e.g. tetralones and indanones), alcohols (e.g. benzhydrols) and racemates or enantiomers of other compound classes (e.g. dinitrophenyl amino acids). Among 22 investigated compounds, 16 racemates were baseline or partially resolved by eluting with methanol or 2-propanol/water mixtures on 4/1 (w/w) layers. The best results were compared with those achieved on microcrystalline cellulose triacetate plates and on cellulose tribenzoate columns. The study of structurally related solutes allowed us to increase the knowledge of the retention and resolution mechanisms on this chiral stationary phase and to highlight the role of π-π interactions between cellulose tribenzoate and solutes with different substituents on the aromatic ring. However, some results were unexpected and confirmed the complexity of enantioseparation mechanisms, thus evidencing the importance of experimental tests. Densitometric scan in the visible region of cellulose tribenzoate/gypsum plates after their exposure to iodine vapours allowed us to successfully perform the quantitative analysis of the investigated compounds, thus overcoming the detection problems normally encountered with this stationary phase.

Reversed-phase and soap thin-layer chromatography of amino acids.

The chromatographic characteristics of 33 amino acids have been studied using soap thin-layer chromatography (TLC). The influence of the type of detergent, the organic solvent and the acid concentration in the eluent on the chromatographic behaviour of the amino acids was investigated. Many interesting separations that cannot be effected by ion-exchange TLC have been performed.

Separation and identification of water-soluble food dyes by ion-exchange and soap thin-layer chromatography.

Eighteen water-soluble food dyes have been studied by chromatography on thin layers of anion-exchange (AG 1-X4, DEAE-cellulose, PAB-cellulose and chitosan) and cation-exchange (Dowex 50-X4, Rexyn 102 and humic acid) materials; layers of silanised silica gel impregnated with cationic or anionic detergent were also used. Fourteen of the dyes were separated, but the two orange and the two black dyes were not. Some applications of the techniques to commercial products are reported.

Chromatographic behaviour of nucleic acid constituents and of phenols on chitosan thin layers.

The chromatographic characteristics of several nucleic acid constituents and of 36 phenols have been investigated on mixed layers of powdered chitosan and microcrystalline cellulose, with water, water-methanol mixtures and aqueous salt solutions at different pH values at mobile phases. The behaviour of the phenols was strongly correlated with the form in which these compounds were present in solution and therefore with the pH of the eluent. Chitosan was more effective than PEI- and DEAE-cellulose as adsorbent in separating phenols. Analytical applications of chitosan layers are reported.

Chromatographic behaviour of alkaloids on thin layers of anion and cation exhangers. I. AG 1-X4 and cellex D.

The chromatographic behaviour of 48 alkaloids has been studied on Bio-Rad AG 1-X4, Cellex D and microcrystalline cellulose, eluting with solutions of different pH but constant ionic strength (0.5). Many interesting separations were effected on both AG 1-X4 and Cellex D layers. The influence of pH on the chromatographic behaviour of alkaloids has been quantitatively studied and an equation was used that expresses the behaviour of the alkaloids on both AG 1-X4 (AcO-) and microcrystalling cellulose layers. The nonapplicability of this equation to Cellex D layers is discussed.

Chromatographic behaviour of phenols on thin layers of cation and anion exchangers. II. Dowex 50-X4 and Rexyn 102.

The chromatographic characteristics of 58 phenols on Rexyn 102 and Dowex 50-X4 thin layers in both the acidic and sodium salt forms have been studied, using elution with water, water-alcohol mixtures and aqueous salt solutions at different pH values. The influence of the percentage of alcohol, the pH and the ionic strength on the chromatographic behaviour of these phenols was investigated. The validity of the relationships among the RF values, the pH of the eluent and the pKa of the phenol has been verified on Dowex 50-X4 (Na+) thin layers. It has been shown that from the RFac, RFalk and pKa values of the different phenols, it is possible to predict their behaviour over the whole pH range and therefore to select the best conditions for their chromatographic separation.

Reversed-phase planar chromatography of some enantiomeric amino acids and oxazolidinones.

The resolution of two enantiomeric amino acids and four structurally related oxazolidinones was evaluated by reversed-phase planar chromatography using both home-made microcrystalline cellulose triacetate (MCTA) layers and mobile phase additivies, such as beta-cyclodextrins (beta-Cy), modified alpha, beta, gamma cyclodextrins and bovine serum albumin (BSA), on commercially available RP-18W/F254 and SilC18-50/UV254 plates. All the enantiomers were partially or baseline resolved by at least one of the chiral phases tested. Densitograms of optical antipodes and their mixtures were measured on MCTA layers developed with hydroalcoholic solvents.

Chromatographic behaviour of alkaloids on thin layers of cation exchangers. II. Alginic acid, Rexyn 102, Dowex 50-X4 and CMCNa.

The chromatographic behaviour of 48 alkaloids on cation exchangers with cellulose, paraffin and polystyrene matrices in both the acid and sodium salt forms has been investigated. Water-organic solvent mixtures, aqueous buffer solutions and organic and mineral acid solutions in both water and in aqueous-organic solvents have been used as eluents. The retention mechanisms of these compounds on alginic acid, Rexyn 102 (Hplus) and Dowex 50-X4 (Hplus) thin layers are discussed. Interesting separations of the alkaloids were carried out on alginic acid and Rexyn 102 (Hplus).

Effect of pasteurization and storage on some components of pooled human milk.

Pooled human milk was subjected to Holder pasteurization and storage at -20 degrees C up to 90 days and examined for its content of fat and L-lactate and for lipid composition. This treatment reduced fats by 6% and L-lactate by at least 7%. In addition, pasteurization and storage induced triglyceride hydrolysis. The absolute amount of free fatty acids (FFAs) which was 0.5% after collection, doubled after pasteurization and rose even more after storage. Different FFA compositions were found by several authors using the same analytical method even for milk samples subjected to the same treatment. More detailed information on procedures must be given to explain the different results.

Simultaneous separation and determination of hydrocarbons and organochlorine compounds by using a two-step microcolumn.

The simultaneous separation and determination of a mixture of hydrocarbons and organochlorine compounds was successfully carried out by using sorption chromatography on a two-step microcolumn of silica and aluminium oxide for their fractionation, and a dual detector system. In addition to the separation and identification of hydrocarbons and heterocompounds containing nitrogen, oxygen and sulphur atoms, separation and identification of chlorinated hydrocarbons (dichlorobenzenes, p-chlorotoluene, hexachlorobutadiene, 1,2,4-trichlorobenzene and 2-chloronaphthalene), pesticides (chlorpicrin, aldrin, lindane, alpha- and beta-benzene hexachloride (BHC), endrin, dieldrin, endosulphan, methoxychlor) and herbicides (propanil, dichlobenil, trifluralin, difolatan) were achieved in mixtures containing polychlorinated biphenyl, strobane and chlordane.