Preparation and characterization of biodegradable nanocomposites derived from carboxymethyl cellulose and hydroxyapatite.

Development of a cost-effective technology for extraction and quantification of carcinogenic and toxic organic materials which are widely used in the industry are critical to humans. Membrane technology received much attention and has already been widely used in this area. In this work, we offer a newly developed bio-based nanocomposite membrane for removal of bisphenol-A (BPA) from water. Three natural components hydroxyapatite (HAp), carboxymethyl cellulose and lysine as a diluent were used for making the bio-based membrane. The membrane was fabricated by two different methods, the conventional casting method and the double decomposition method. Analysis and testing results showed that, membrane produced by the casting method is rough, stiff and partially soluble in water. However, the film made by the double decomposition method is smooth, flexible, and has low water solubility. The physicochemical characteristics of the prepared membranes were determined by Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA/DTA). The morphology and components interface were observed by X-ray wide angle (WAXD), scanning electron microscopy (SEM) and electron microscopy (SEM/FEG). The spectral and crystallographic data showed the presence of an effective interaction between hydroxyapatite and CMC plasticized with lysine. Results also show that, the particles size of the composite decrease as the content of CMC increases, with an increase of a 2% by weight of CMC the size increases by 18±3nm. Produced membrane composite could be classified as tri-functional material: it could be useful for extracting toxic material bisphenol A (BPA) from baby food containers; has antimicrobial and antifungal properties; and a valuable candidate for use in bone tissue engineering.

Fluorescent chemosensor for pyridine based on N-doped carbon dots.

Fluorescent carbon dots (CDs) and its nitrogen doped (N-CDs) nanoparticles have been synthesized from lactose as precursor using a bottom-up hydrothermal methodology. The synthesized nanoparticles have been characterized by elemental analysis, FTIR, Raman, TEM, DLS, XPS, and steady-state and life-time fluorescence. The synthesized carbon nanoparticles, CDs and N-CDs, have a size at about 7.7±2.4 and 50±15nm, respectively, and quantum yields of 8% (CDs) and 11% (N-CDs). These techniques demonstrated the effectiveness of the synthesis procedure and the functionalization of the CDs surface with amine and amide groups in the presence of NH3 in aqueous media. The effect of excitation wavelength and pH on the luminescent properties was studied. Under the optimal conditions, the nitrogen doped nanoparticles can be used as pyridine sensor in aqueous media because they show an enhancement of its fluorescence with a good linear relationship. The analytical method is simple, reproducible and very sensitive for pyridine determination.

Microwave-assisted synthesis of carbon dots and its potential as analysis of four heterocyclic aromatic amines.

Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the morphology shape (average 10nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450 nm with a lifetime of 2.1 ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35-0.45 mg L(-1) concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.

Pesticide residue levels in green beans cultivated in Souss Masa valley (Morocco) after multiple applications of bifenthrin and λ-cyhalothrin.

Dissipation of bifenthrin and λ-cyhalothrin pyrethroid insecticides, under environmental conditions, was evaluated on green beans grown in experimental greenhouses (Souss Massa valley, Morocco). Pesticide residues were determined by gas chromatography with micro electron-capture detector (GC-µECD) after dichloromethane extraction and cleanup on florisil phase cartridges. In the case of field experiments, a random block scheme was employed. Each block contained 25 plants in a single row and tests were carried out in triplicates applying pesticides at the recommended doses by the manufacturers. Fruit samples were periodically taken until the end of the preharvest interval (p.i.). The results obtained showed that the p.i of bifenthrin in green bean were 4 days in the winter and 3.5 days in the spring, whereas that for λ-cyhalothrin 8 days was found in the winter and 7.5 days in the spring. Consequently, it is possible to consider the European Union maximum residue limit (EU MRL) values compatible with the proper agricultural practices used for growing green bean in the plastic greenhouse of Souss Massa valley in South Morocco. Bifenthrin had a degradation of first-order kinetics, whereas that of levels for λ-cyhalothrin residue can not be interpreted by the use of a first order model.

Nanoparticle-based assay for the detection of virgin argan oil adulteration and its rapid quality evaluation.

A new method, based on the formation of gold nanoparticles (AuNPs) and spectrophotometric analysis, is proposed to determine total phenolic acids in virgin argan oil samples. These compounds have reducibility due to the presence of the phenol group in their molecular structure, and a redox reaction occurs in the presence of HAuCl(4). The formation of AuNPs as a result of the redox reaction leading to colour changes can be visually observed, resulting in strong light signals that show absorption at 555 nm. As ferulic acid represents more than 95% of the total phenolic acid content of virgin argan oil, this compound was used as an adulteration marker to carry out the screening of samples for the evaluation of the authenticity of virgin argan oils. The analytical features of this screening method also allowed a low precision quantization of the quality of the product. Then, a reference HPLC-DAD/FD method was used to confirm the potential adulterated samples, as well as to provide a detailed quantitative analysis of the most representative phenolic compounds in the samples. The overall screening-confirmation strategy was validated by analysing pure virgin argan oil samples and argan oil samples adulterated with other commercial vegetable oils, demonstrating the reliability of the results. This approach is characterised by its simplicity, low cost, rapid information and responded to practical laboratories needs.

Supercritical fluid extraction as an on-line clean-up technique for rapid amperometric screening and alternative liquid chromatography for confirmation of paraquat and diquat in olive oil samples.

A rapid and simple method for the direct screening of paraquat (PQ) and diquat (DQ) in olive oil samples is proposed. The sample screening method involves supercritical fluid extraction (SFE) (clean-up followed by the extraction of the analytes) followed by continuous flow electrochemical detection. Those samples for which the total concentration is close to or above the threshold limit established by the Columbian Society for Social Protection (0.05 microg g(-1)) are subsequently analyzed by liquid chromatography (LC) with diode array detection (DAD). This confirmation method allows the determination of PQ and DQ in the range between 0.04 and 1.0 microg g(-1), with average relative standard deviations lower than 3.5%, and 0.003 and 0.002 microg g(-1) detection limits for PQ and DQ, respectively. The proposed arrangement opens up interesting prospects for the direct determination of polar pesticides in complex samples with a good throughput and a high level of automation.

Self-assembled monolayer-based piezoelectric flow immunosensor for the determination of canine immunoglobulin.

A simple, highly sensitive immunosensor for the direct determination of immunoglobulin (Ig) in canine serum based on a piezoelectric crystal accommodated in a flow-cell was developed and optimized. The new biosensor is also useful for discriminating between Ig subclasses present in canine serum by using specific monoclonal antibodies binding to the coated crystal. Various canine monoclonal anti-IgG were deposited onto the surface of the gold-coated crystal resonator using the self-assembly technique to form a receptor layer. The highly ordered self-assembled monolayers thus obtained provide a well-controlled surface structure and many advantages as regards sensing performance. The results obtained with the proposed immunosensor were compared with those provided by a protein A-based orientation-controlled immobilization method for the same monoclonal antibodies and also with direct physical adsorption of the antibodies. The crystal was accommodated in a flow-cell that was inserted into a buffer flowing stream in order to make resonant frequency measurements.

Use of non-aqueous capillary electrophoresis for the quality control of commercial saffron samples.

A non-aqueous capillary electrophoresis (NACE) method for quantifying the seven crocin metabolites that are the major biologically active ingredients of saffron was developed. Separation is done by using a fused silica capillary filled with a 12.5 mM H3BO3/37.5 mM sodium tetraborate methanolic solution as background electrolyte. The results obtained were compared with the total index "safranal value", widely used as a quality measure of saffron products. The comparison revealed that the proposed NACE method provides useful information not obtained in the safranal value. Infact, samples with a similar safranal value can contain crocin metabolites in different concentrations and relative proportions. This new method is very useful for quality control in commercial saffron samples.

Automatic on line preconcentration and determination of lead in water by ICP-AES using a TS-microcolumn.

A simple, sensitive, low-cost and rapid, flow injection system for the on-line preconcentration of lead by sorption on a microcolumn packed with silica gel funtionalized with methylthiosalicylate (TS-gel) was developped. The metal is directly retained on the sorbent column and subsequently then eluted from it by EDTA. Five variables (sample flow rate, eluent flow rate, eluent concentration, pH and buffer concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using two level factorial and Box-Behnken designs. The optimum conditions established were applied to the determination of lead by flow injection inductively coupled plasma atomic emission spectrometry (FI-ICP-AES). The proposed method has a linear calibration range from 10 to at least 500ngml(-1) of lead. At a sample frequency of 24h(-1) and a 120s preconcentration time, the enrichment factor was 41, the detection limit was 15.3ngml(-1) (S/N=3) and the precision, expressed as relative standard deviation, was 0.9% (at 100ngml(-1)). Validation of the developed method was carried out against electrothermal atomic absorption spectrometry analysis without statistically significant differences between the proposed method and the atomic absorption method.

Determination of cadmium in water by ICP-AES with on-line adsorption preconcentration using DPTH-gel and TS-gel microcolumns.

Two flow injection inductively coupled plasma atomic emission spectrometric methods for the preconcentration and determination of trace amounts of cadmium in sea-water and waste-water samples are described based on the adsorption of the metal ion on a micro-column placed in the injection valve of the FI manifold and packed with silica gel funtionalised with 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide (DPTH-gel) and silica gel functionalised with methylthiosalicylate (TS-gel), respectively. Various parameters and chemical variables affecting the preconcentration and determination of this metal by ICP-AES are evaluated. The DPTH-gel preconcentration method has a linear calibration range from 5 to at least 100 ng ml(-1) of cadmium, with a R.S.D. of 1.1% for ten independent analyses of 100 ng ml(-1), a detection limit of 1.1 ng ml(-1) and a throughput of 40 samples per hour using a 60 s preconcentration time. The TS-gel preconcentration method shows a linear range between 10 and 100 ng ml(-1), with a R.S.D. of 2.5% for ten independent analyses of 100 ng ml(-1), a detection limit of 4.3 ng ml(-1) and a sample throughput of 24 samples per hour for a preconcentration time of 120 s. Validation was carried out against a certified reference water sample and by determining the analyte content in spiked synthetic sea-water, sea-water and waste-water.