Sample Preparation 

Abstract: This paper describes, a new, sensitive, and low cost solid phase extraction (SPE) method using a poly(N-phenylethanolamine) /multi-walled carbon nanotubes (MWCNTs) nanocomposite for extraction, pre-concentration, and flame atomic absorption spectrometric (FAAS) determination of trace level palladium in distilled water, tap water, Caspian sea water, Persian Gulf water, spring water, lake water and soil samples, as well as real samples. The poly(N-phenylethanolamine)/MWCNTs nanocomposite were characterized using Fourier Transform-infrared (FT-IR) spectroscopy, thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). Factors affecting the pre-concentration of palladium, including sample pH, flow rate, and type and volume of eluent, were investigated. The effect of interfering ions and break through volume on the separation and determination of palladium ions was also determined. The maximum sorbent capacity of the poly (N-phenylethanolamine)/MWCNTs nanocomposite was calculated to be 101.5 mg g −1 . The pre-concentration factor, relative standard deviation, and limit of detection of the method were found to be 150, 2.8% (n=10), and 0.09 ng mL −1 , respectively. The presented method was compared to certified reference materials, and finally, the presented technique was applied to different matrices spiked with 5 ng/mL of analyte.

Abstract: Abstract Volatile compounds determine the organoleptic characteristics of grapes and wines. The main grape aroma compounds are monoterpenols and volatile benzene compounds. Aroma precursors, such as glycoside compounds and C13-norisoprenoids, are also present. These compounds are grape secondary metabolites, which are also studied for chemotaxonomic purposes. In winemaking, they are transferred to the product and the wine aroma profile is enriched by many fermentative compounds. This paper reviews the Solid Phase Extraction (SPE) and Solid Phase Microextraction (SPME) methods used to study the grape and wine aromas. Despite the solvent use, SPE is still the more suitable method for the grape aroma compounds because it allows concentration of the analytes down to the microliter scale after starting from a considerable volume of sample. Moreover, it allows the semi-quantitative profiling of samples. On the other hand, SPME is effective in the analysis of compounds for which standards are available, with high efficiency, short time and no solvents use.

Abstract: Abstract A solid-phase microextraction sorbent composite was developed using the sol-gel technique. The multi-walled carbon nanotubes (MWCNTs) were added to a nanocomposite and the homogeneous, doped composite was injected into a polypropylene hollow fiber. This device has been applied for the determination of three nitro aromatic compounds, including m-nitroaniline (NA), nitrobenzene (NB) and p-nitrotoluene (NT), in environmental waters via direct immersion hollow fiber solid-phase microextraction (HF-SPME) and high performance liquid chromatography-photodiode array detector (HPLC-PDA). The results illustrated that this new technique is a simple and reliable method for SPME device preparation: the prepared sorbent did not swell in organic solvents and possessed high mechanical strength; the SPME device employed was not fragile because of the polypropylene protector fiber; and, the fiber was disposable such that no carry-over effects were present. A homemade, pre-heating electrical device was designed for the back-extraction and pre-concentration of the analytes and was utilized before the HPLC injection step. Using this trap significantly increased the efficiency and analyte pre-concentration factors. In optimal conditions, the detection limits of the analytes varied between 0.1 and 3.0 ng mL-1 (n=8), precision was in the range of 0.41–4.19% (n = 3) and linear ranges were within 1.0 - 1000 ng mL-1 for m-nitroaniline; 0.5 - 1000 ng mL-1 for nitrobenzene and 5.0 - 1000 ng mL-1 for p-nitrotoluene. The method was successfully applied to the analysis of environmental water samples with recoveries from 87.9 to 96.1%.

Abstract: Abstract The present work describes the attempt for the preconcentration of nickel ions by using vortex assisted dispersive liquid-liquid microextraction from aqueous samples. In this method, a small amount of chloroform is rapidly injected by syringe into the water sample containing nickel ions complexed by diethyldithiocarbamate (DDTC).This forms a cloudy solution. The cloudy state is the result of chloroform fine droplets formation, which are dispersed in bulk aqueous sample. Therefore, Ni-DDTC complex is extracted into the fine chloroform droplets and vortex agitation takes place during six minutes. After optimization of experimental variables and determination of analytical characteristics, the method is evaluated for application in real samples. HPLC is used as separation and detection system.