M. Conceição B. S. M. Montenegro

Contribution of hospital effluents to the load of pharmaceuticals in urban wastewaters: identification of ecologically relevant pharmaceuticals.

The impact of effluent wastewaters from four different hospitals: a university (1456 beds), a general (350 beds), a pediatric (110 beds) and a maternity hospital (96 beds), which are conveyed to the same wastewater treatment plant (WWTP), was evaluated in the receiving urban wastewaters. The occurrence of 78 pharmaceuticals belonging to several therapeutic classes was assessed in hospital effluents and WWTP wastewaters (influent and effluent) as well as the contribution of each hospital in WWTP influent in terms of pharmaceutical load. Results indicate that pharmaceuticals are widespread pollutants in both hospital and urban wastewaters. The contribution of hospitals to the input of pharmaceuticals in urban wastewaters widely varies, according to their dimension. The estimated total mass loadings were 306 g d(-1) for the university hospital, 155 g d(-1) for the general one, 14 g d(-1) for the pediatric hospital and 1.5 g d(-1) for the maternity hospital, showing that the biggest hospitals have a greater contribution to the total mass load of pharmaceuticals. Furthermore, analysis of individual contributions of each therapeutic group showed that NSAIDs, analgesics and antibiotics are among the groups with the highest inputs. Removal efficiency can go from over 90% for pharmaceuticals like acetaminophen and ibuprofen to not removal for β-blockers and salbutamol. Total mass load of pharmaceuticals into receiving surface waters was estimated between 5 and 14 g/d/1000 inhabitants. Finally, the environmental risk posed by pharmaceuticals detected in hospital and WWTP effluents was assessed by means of hazard quotients toward different trophic levels (algae, daphnids and fish). Several pharmaceuticals present in the different matrices were identified as potentially hazardous to aquatic organisms, showing that especial attention should be paid to antibiotics such as ciprofloxacin, ofloxacin, sulfamethoxazole, azithromycin and clarithromycin, since their hazard quotients in WWTP effluent revealed that they could pose an ecotoxicological risk to algae.

Optical sensors and biosensors based on sol–gel films

The sol-gel technology is being increasingly used for the development of optical sensors and biosensors, due to its simplicity and versatility. By this process, porous thin films incorporating different chemical and biochemical sensing agents are easily obtained at room temperature, allowing final structures with mechanical and thermal stability as well as good optical characteristics. In this article, an overview of the state-of-the-art of sol-gel thin films-based optical sensors is presented. Applications reviewed include sensors for determination of pH, gases, ionic species and solvents, as well as biosensors.

Sequential injection chromatographic determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations

A new separation method based on a novel reversed-phase sequential injection chromatography (SIC) technique was used for simultaneous determination of ambroxol hydrochloride and doxycycline in pharmaceutical preparations in this contribution. The coupling of short monolith with SIA system results in an implementation of separation step to until no-separation low-pressure method. A Chromolith((R)) Flash RP-18e, 25-4.6mm column (Merck, Germany) and a FIAlab((R)) 3000 system (USA) with a six-port selection valve and 5ml syringe were used for sequential injection chromatographic separations in our study. The mobile phase used was acetonitrile-water (20:90, v/v), pH 2.5 adjusted with 98% phosphoric acid, flow rate 0.48mlmin(-1), UV detection was at 213nm. The validation parameters have shown good results: linearity of determination for both compounds including internal standard (ethylparaben) >0.999; repeatability of determination (R.S.D.) in the range 0.5-5.4% at three different concentration levels, detection limits in the range 0.5-2.0mugml(-1), and recovery from the pharmaceutical preparation in the range 99.3-99.9%. The chromatographic resolution between peak compounds was >5.0 and analysis time was <9min under the optimal conditions. The method was found to be applicable for routine analysis of the active compounds ambroxol hydrochloride and doxycycline in various pharmaceutical preparations.

An efficient non-mediated amperometric biosensor for nitrite determination

In this paper we propose the construction of a new non-mediated electrochemical biosensor for nitrite determination in complex samples. The device is based on the stable and selective cytochrome c nitrite reductase (ccNiR) from Desulfovibrio desulfuricans, which has both high turnover and heterogeneous electron transfer rates. In opposition to previous efforts making use of several redox mediators, in this work we exploited the capacity of ccNiR to display a direct electrochemical response when interacting with pyrolytic graphite (PG) surfaces. To enable the analytical application of such bioelectrode the protein was successfully incorporated within a porous silica glass made by the sol-gel process. In the presence of nitrite, the ccNiR/sol-gel/PG electrode promptly displays catalytic currents indicating that the entrapped ccNiR molecules are reduced via direct electron transfer. This result is noteworthy since the protein molecules are caged inside a non-conductive silica network, in the absence of any mediator species or electron relay. At optimal conditions, the minimum detectable concentration is 120 nM. The biosensor sensitivity is 430 mA M(-1) cm(-2) within a linear range of 0.25-50 microM, keeping a stable response up to two weeks. The analysis of nitrites in freshwaters using the method of standard addition was highly accurated.

Application of amperometric sol-gel biosensor to flow injection determination of glucose

A glucose biosensor with enzyme immobilised by sol-gel technology was constructed and evaluated. The glucose biosensor reported is based on encapsulated GOX within a sol-gel glass, prepared with 3-aminopropyltriethoxy silane, 2-(3,4-epoxycyclohexyl)-ethyltrimetoxy silane and HCl. A flow system incorporating the amperometric biosensor constructed was developed for the determination of glucose in the 1x10(-4)-5x10(-3) moll(-1) range with a precision of 1.5%. The results obtained for the analysis of electrolytic solution for iv administration and human serum samples showed good agreement between the proposed method and the reference procedure, with relative error <5%.

Development of a simple analytical method for the simultaneous determination of paracetamol, paracetamol-glucuronide and p-aminophenol in river water

Paracetamol is among the most worldwide consumed pharmaceuticals. Although its occurrence in the environment is well documented, data about the presence of its metabolites and transformation products is very scarce. The present work describes the development of an analytical method for the simultaneous determination of paracetamol, its principal metabolite (paracetamol-glucuronide) and its main transformation product (p-aminophenol) based on solid phase extraction (SPE) and high performance liquid chromatography coupled to diode array detection (HPLC-DAD). The method was applied to analysis of river waters, showing to be suitable to be used in routine analysis. Different SPE sorbents were compared and the use of two Oasis WAX cartridges in tandem proved to be the most adequate approach for sample clean up and pre-concentration. Under optimized conditions, limits of detection in the range 40-67ng/L were obtained, as well as mean recoveries between 60 and 110% with relative standard deviations (RSD) below 6%. Finally, the developed SPE-HPLC/DAD method was successfully applied to the analysis of the selected compounds in samples from seven rivers located in the north of Portugal. Nevertheless all the compounds were detected, it was the first time that paracetamol-glucuronide was found in river water at concentrations up to 3.57μg/L.

Sequential determination of calcium and nitrate ions in waters by potentiometric flow injection

A compact and robust flow injection system for the simultaneous determination of calcium and nitrate in waters, with sequential detection by potentiometric sensors, is described. The effects of silver ionic strength adjuster (ISA) or lead ISA carrier solutions on the response of the tubular electrodes used and on the ability of the system to control interferences were studied in detail. Under the selected experimental conditions, the response slope and lower limit of linear response were 53.4 mV per decade and 10–4.3 mol l–1 for the nitrate sensor and 31.3 mV per decade and 10–4.75 mol l–1 for the calcium sensor. The reproducibility (relative standard deviation) was better than 1% and the sample throughput was approximately 145 h–1. The results provided by the flow system were shown to be accurate, reproducible and free from interferences. The results obtained for calcium and nitrate in 23 samples with the flow injection system and with a reference method were in good agreement with each other. No significant interferences from other ions, especially chloride and hydrogencarbonate, were observed in surface waters, excluding those with a high saline content. The sequential method described was shown to be useful in routine determinations with a high sampling rate at a low cost.

A phenobarbital ion-selective electrode without an inner reference solution, and its application to pharmaceutical analysis

Abstract This paper describes the construction and assessment of a phenobarbital ion-selective electrode and a rapid and reliable phenobarbital tablet assay potentiometric method that provides results which are in good agreement with those obtained by the British Pharmacopoeia (BP) method.

Construction and use of a tubular picrate ion-selective electrode for reducing sugar determination in Port wine by flow-injection analysis

Abstract A picrate ion-selective electrode without inner reference solution and based on bis(triphenylphosphoranylidene)ammonium picrate dissolved in 2-nitrophenyloctyl ether was constructed and its characteristics assessed. With respect to reducing sugar determination in Port wine, a tubular electrode based on the same sensor system was developed and incorporated into a flow-injection manifold devised for this determination. The methodology involves a reaction between the reducing sugar and picric acid, the decrease in the picrate concentration being monitored with the tubular electrode. A linear dependence between peak width, at a fixed potential and the logarithm of sugar concentration in the range 25–200 g l−1 was obtained. The proposed system allows wine samples to be injected with no previous treatment and allows a sample throughput of 50 determinations per hour, a relative standard deviation less than 4%, and the results are comparable to the reference procedures.

5,5-Diethylbarbiturate tubular electrode for use in flow-injection detection systems

Abstract The construction, assessment and pharmaceutical appalications of a tubular potentiometric detector sensitive to the 5,5-diethylbarbiturate anion based on quaternary ammonium salt (tetraoctylammonium5,5-diethylbarbiturate) dissolved in o-nitrophenyl octyl ether immobilized in PVC are described. The intrinsic characteristics of the tubular electrode were determined in a low-dispersion manifold and compared with those of a conventional-shaped electrode with no internal reference solution and incorporating the same sensor. The behaviour of a double-channel flow-injection manifold with the same potentiometric detector was evaluated to assess its applicability to the determination of 5,5-diethylbarbiturate in pharmaceutical preparations. Data obtained in the determination of the anion in the latter matrices are presented and compared with those obtained by the conventional British Pharmacopoeia method.