Ultrasound-assisted magnetic solid-phase extraction of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons from water samples with a magnetic polyaniline modified graphene oxide nanocomposite

A novel magnetic graphene oxide nanocomposite modified with polyaniline (Fe₃O₄@GO-PANI) was synthesized and applied for the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) (i.e. fluorene, phenanthrene and pyrene) and nitrated polycyclic aromatic hydrocarbons (N-PAHs) (i.e. 2-nitrofluorene, 9-nitroanthracene, 1-nitropyrene and 3-nitrofluoranthene) prior to their determination by gas chromatography-mass spectrometry. The prepared nanomaterial was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform-infrared spectroscopy. The main experimental parameters affecting the extraction and desorption steps of the MSPE procedure were investigated and optimized. Under optimum conditions, coefficients of determination (r²) ranged between 0.9970 and 0.9995, limits of detection (LODs, S/N = 3) ranged between 0.04-0.05 ng mL^-1 for PAHs and 0.01-0.11 ng mL^-1 for N-PAHs, while the relative standard deviation for intra-day and inter-day repeatability were lower than 10.0% for PAHs and N-PAHs. The method was successfully applied to the analysis of tap, mineral and river water samples. Relative recoveries in spiked water samples ranged between from 91.6 to 114% and from 92.3 to 110% for PAHs and N-PAHs, respectively. The proposed method is simple, rapid, sensitive and the Fe₃O₄@GO-PANI sorbent can be reused for at least 15 times without significant decrease in extraction recovery.

Direct determination of toxic trace metals in honey and sugars using inductively coupled plasma atomic emission spectrometry

A rapid method for the determination of Pb, Cd, Cu, Cr, Co, Ni, Mn and Zn in honey and sugars without prior digestion or ashing of the sample was developed, using inductively coupled plasma atomic emission spectrometry (ICP-AES). The critical instrumental parameters such as sample flow rate and radio frequency incident power were thoroughly optimized. The effect of matrix type and its concentration was also examined for glucose/fructose, sucrose and honey matrices. The sensitivity was investigated using calibration curves obtained in presence of the above matrices. The obtained recoveries for Cd, Cu, Cr, Co, Ni and Mn at the mugl(-1) level were satisfactory and practically independent of the matrix used for the calibration standards. The recoveries of Pb and Zn were less sufficient. Various commercial samples of honey, sugar, glucose and fructose were analyzed with respect to their toxic metal content. The method can be applied for routine analysis, quality and environmental pollution control purposes at the mugl(-1) level of concentration, after suitable dilution of the samples.

Storage stability studies for tributyltin determination in human urine samples using headspace solid-phase microextraction and gas chromatography mass spectrometry

A headspace solid-phase micro-extraction (HS-SPME) method was employed in order to study the effect of storage conditions of human urine samples spiked with tributyltin (TBT) using gas chromatography and mass spectrometry. To render the analyte more volatile, the derivatization (ethylation) was made in situ by sodium tetraethylborate (NaBEt(4) ), which was added directly to dilute unpreserved urine samples and in buffers of similar acidity. The stability of TBT in human urine matrix was compared with the stability of TBT in buffer solutions of similar pH value. Critical parameters of storage conditions such as temperature and time, which affect the stability of TBT in this kind of matrix, were examined extensively. The tests showed that the stability of TBT remains practically satisfactory for a maximum of 2 days of storage either at +4 or 20°C. Greater variations were observed in the concentration of TBT in human urine samples at +4°C and lower ones at -20°C over a month's storage. The freeze-thaw cycles have negative effect on the stability and should be kept to a minimum. The results from spiked urine samples are also discussed in comparison to those acquired from buffer solutions of equal TBT concentration.

Comparison of tetraethylborate and tetraphenylborate for selenite determination in human urine by gas chromatography mass spectrometry, after headspace solid phase microextraction

Two different derivatizing reagents were tested for the development of a fast and sensitive method for the determination of selenites (Se(IV)) in human urine. The reagents were sodium tetraethylborate (NaBEt(4)) and tetraphenylborate (NaBPh(4)), respectively, and the procedure is based on in situ derivatization of selenites in aqueous medium. Selenite ions are converted to diethylselenide (DESe) or diphenylselenide (DPhSe) and subsequently collected from the headspace by solid phase microextraction using a silica fiber coated with polydimethylsiloxane (HS-SPME). Finally, they are quantitated by GC/MS in SIM mode. Ethylation over phenylation was proved preferable for the headspace extraction because of the higher volatility of the diethyl-derivative of selenites. The optimization of the HS-SPME conditions was performed both in aqueous and urinary solutions. Under the optimum conditions for HS-SPME, the gas chromatographic conditions were also optimized. Between the two alkylation reagents tetraethylborate was proved more efficient and the quantitation was satisfactory. Aqueous certified reference materials were analyzed to evaluate the accuracy of the method. The precision of the method was 4.2% and the calculated detection limit was 0.05microgL(-1) for human urine.

Development of a slurry introduction method for multi-element analysis of antibiotics by inductively coupled plasma atomic emission spectrometry using various types of spray chamber and nebulizer configurations

A direct sample introduction inductively coupled plasma atomic emission spectrometric (ICP-AES) method, for multi-element analysis of powdered antibiotic drugs was developed using the slurry formation technique. The slurry of powdered sample is formed in dilute nitric acid solution in presence of Triton X-100 surfactant. Two different configurations of spray chamber and nebulizer were tested for direct aspiration of slurry into the plasma: (i) cyclonic spray chamber combined with babington-type nebulizer and (ii) scott-type double-pass spray chamber combined with cross-flow nebulizer. The latter configuration proved to be less tolerable to slurry aspiration. RF power generator, nebulizer argon gas flow rate, nebulizer sample uptake flow rate and slurry sample concentration were optimized. The sensitivity of the proposed method was compared to the corresponding sensitivity obtained from aqueous solutions for each analyte. The performance characteristics of the slurry aspiration method were evaluated against the complete acid-digestion method followed ICP-AES. Finally, the proposed method was applied to the analysis of commercial antibiotics.

Development of a rapid multi-element method of analysis of antitussive syrups by inductively coupled plasma atomic emission spectrometry and direct sample introduction

A new rapid method was developed and optimized for routine multi-element determination of traces of metals in antitussive syrups using direct introduction of diluted syrup into the nebulization system of inductively coupled plasma atomic emission spectrometer (ICP-AES). Using a Scott-type double-pass spray chamber combined with a cross-flow nebulizer, the optimum ICP conditions, like RF incident power, argon gas flow rate and nebulizer sample uptake flow rate were found. A critical objective of the study was to evaluate the matrix effect on the intensity and consequently on the sensitivity of the developed method. Thus, the maximum syrup concentration which could be introduced into the argon plasma, was estimated. The sensitivity variation was calculated as compared to the corresponding sensitivity obtained from aqueous solutions for each analyte. The performance characteristics of the proposed method were evaluated for quantitative and semi-quantitative determination and finally, the method was applied to the analysis of various commercial antitussives.

Heavy metals in aquatic plants and sediments from water systems in Macedonia, Greece

Heavy metal concentrations were surveyed in several species of aquatic macrophytes and in sediments of a lake and four rivers from Macedonia, northern Greece. Acid digestion of sediments and plant material and the subsequent use of atomic absorption spectrometry were the analytical methodologies followed for the analysis. Values were variable within each species while differences in metal contamination among the studied water ecosystem were also found. The lake was less contaminated than the rivers, the contamination of which is dependent on the metal species. Sediment had greater Cu, Pb, and Ni contamination than the aquatic plants, whereas the reverse was the case for Zn, Cd, and Mn. The mean heavy metal contents of the sediments and aquatic plants were in the descending order of Mn > Zn > Ni > Cu > Pb > Cd, whereas in the accumulation of metals by plant tissues, the corresponding order was root > rhizomes > leaf > flower > stem > seed.