Direct Solid-phase Microextraction Method Research Articles

Optimization of a sensitive method for the determination of nitro musk fragrances in waters by solid-phase microextraction and gas chromatography with micro electron capture detection using factorial experimental design

A solid-phase microextraction method (SPME) followed by gas chromatography with micro electron capture detection for determining trace levels of nitro musk fragrances in residual waters was optimized. Four nitro musks, musk xylene, musk moskene, musk tibetene and musk ketone, were selected for the optimization of the method. Factors affecting the extraction process were studied using a multivariate approach. Two extraction modes (direct SPME and headspace SPME) were tried at different extraction temperatures using two fiber coatings [Carboxen-polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane-divinylbenzene (PDMS/DVB)] selected among five commercial tested fibers. Sample agitation and the salting-out effect were also factors studied. The main effects and interactions between the factors were studied for all the target compounds. An extraction temperature of 100 degrees C and sampling the headspace over the sample, using either CAR/PDMS or PDMS/DVB as fiber coatings, were found to be the experimental conditions that led to a more effective extraction. High sensitivity, with detection limits in the low nanogram per liter range, and good linearity and repeatability were achieved for all nitro musks. Since the method proposed performed well for real samples, it was applied to different water samples, including wastewater and sewage, in which some of the target compounds (musk xylene and musk ketone) were detected and quantified.

Development of a closed loop stripping analysis using solid-phase microextraction to analyze geosmin and MIB in drinking water

A novel analytical method, solid phase microextraction (SPME) coupled with closed loop stripping analysis (CLSA), was introduced for the analysis of MIB and geosmin at nanogram per liter concentration levels. The optimum CLSA/SPME analysis conditions of 65 °C, 60-minute extraction time, and 0.5 M sodium sulfate were determined from a statistical design. The individual Kfw of MIB and geosmin from CLSA/SPME method was 4.21 and 4.85, and resulted an order of magnitude greater than the Kfw obtained from direct SPME method. A detection limit of 10 ng/L of MIB and geosmin was achieved by GC-MS with CLSA/SPME with a polyacrylate phase. Overall, CLSA/SPME provides a fast, solvent-free, and less labor intensive method compared to the standard CLSA. The CLSA/SPME method is a valuable alternative method for the analysis of taste-and-odor causing compounds in drinking water.

Optimisation of a solid-phase microextraction method for synthetic musk compounds in water

A solid-phase microextraction method (SPME) for determining trace levels of synthetic musk fragrances in residual waters has been developed. Six polycyclic musks (cashmeran, phantolide, celestolide, traseolide, galaxolide and tonalide), and a macrocyclic musk (ambrettolide) have been analysed. A detailed study of the different parameters affecting the extraction process is presented. The main important factors affecting the microextraction process have been studied and optimised by means of a categorical factorial design. Two extraction modes (direct SPME and headspace SPME) were tried at different extraction temperatures using four different fiber coatings [polydimethylsiloxane (PDMS), Carboxen (CAR)–PDMS, PDMS–divinylbenzene (DVB) and Carbowax (CW)–DVB]. An extraction temperature of 100 °C sampling the headspace over the sample using CAR–PDMS or PDMS–DVB as fiber coatings were found to be the experimental conditions that lead to a more effective extraction. The method proposed is very simple and yields high sensitivity, with detection limits in the low pg/ml, good linearity and repeatability for all the target compounds. The total analysis time, including extraction and GC analysis, was only 45 min. The optimised method performed well when it was applied to waste water from an urban treatment plant.

Strategies for the analysis of chlorobenzenes in soils using solid-phase microextraction coupled with gas chromatography–ion trap mass spectrometry.

Solid-phase microextraction (SPME) was examined as a possible alternative to Soxhlet extraction in the analysis of chlorobenzenes at high concentrations (up to 65 μg g −1) in soils. Gas chromatography–ion trap mass spectrometry (GC–IT-MS) was used and different strategies were tested in order to obtain suitable responses for chlorobenzenes. Two headspace SPME methods, using fibres coated with polydimethylsiloxane (PDMS) as stationary phase, in splitless and split injection modes, respectively, and a direct SPME method using 100-μm PDMS fibre were studied. For headspace SPME, 7-μm and 100-μm PDMS fibres were used and good sensitivity was obtained by adding 200 μl of water to the soil, at a sampling temperature of 30°C and absorption times of 40 and 60 min, respectively. For direct SPME, which involves extraction of chlorobenzenes from stirred soil solutions using a 100-μm PDMS fibre, the effect of the addition of different organic solvents, such as methanol or acetone, on the sensitivity and the extraction time was evaluated. The shortest time to reach equilibrium (50 min) was achieved when a mixture acetone–water (30:70) was added to the sample. Repeatabilities lower than 8% were obtained for headspace and direct SPME with 100-μm PDMS fibre, whereas for 7-μm PDMS fibre, repeatabilities were slightly higher (between 7 and 11%). The SPME methods were applied to the analysis of chlorobenzenes in an industrially contaminated clay soil, CRM-530, which is a candidate reference material. Chlorobenzenes in this soil were quantified by standard addition, which led to good reproducibility (R.S.D. between 2 and 10%) for headspace and direct SPME with the 100-μm PDMS fibre and acceptable detection limits (30 to 100 pg g −1 of soil). The results were consistent with those obtained in a European intercomparison exercise.