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Analytical and Bioanalytical Chemistry (v.364, #7)
3rd Symposium on Extraction for Sample Preparation SFE – (X)SE – SPME
by Bernd Wenclawiak (pp. 609-609).
Optimization of the SPME device design for field applications by L. Müller; T. Górecki; J. Pawliszyn (pp. 610-616).
Solid Phase Microextraction (SPME) is a powerful tool for field investigations. With the help of a portable gas chromatograph it can be used for fast analysis directly on-site, or it can be utilized for field sampling and then transported to the laboratory for instrumental analysis. In the latter case, it is important for the reliability of the results that losses of volatiles and contamination of the fiber during storage and transport are minimized. A number of dedicated devices, designed and built for SPME field sampling and storage, have been developed and tested. Sealing capacity of the prototypes was investigated by storing compounds ranging in volatility from methylene chloride to 1,3-dichlorobenzene on selected SPME fibers (100 μm PDMS, 65 μm PDMS/DVB and 75 μm Carboxen/PDMS) at different temperatures. Significant differences were noticed in storage capacity from coating to coating. A comparison between the field samplers optimized in this study and the field sampler commercially available from Supelco revealed advantages and limitations of each of the designs. A gas-tight valve syringe (50 μL SampleLock by Hamilton), modified in order to accommodate the SPME fiber, had the best storage capacity for very volatile compounds. With this device, over 80% of the initial amount of methylene chloride was retained by the 100 μm PDMS fiber after 24 h of refrigerated storage, which is a very good result considering that the PDMS coating is characterized by very low storage capacity for volatiles. Field sampling investigations with the SPME prototypes confirmed the usefulness of these devices for field analysis.
The potential of micromixers for contacting of disperse liquid phases by V. Haverkamp; Wolfgang Ehrfeld; Klaus Gebauer; Volker Hessel; Holger Löwe; Thomas Richter; Christian Wille (pp. 617-624).
The dispersion of two immiscible fluids in a static micromixer comprising interdigital channels with corrugated walls was investigated using silicon oil dispersed in dyed as well as pure water as test systems. Silicon oil and water flow rates between 20 mL/h to 500 mL/h and 150 mL/h to 700 mL/h were used, respectively. The experiments revealed the dependence of the average droplet size and size distribution on geometrical parameters of the micromixer and operating conditions. Dispersions with average droplet sizes as small as 5.6 μm and monomodal size distributions having small standard deviations of the droplet size down to 3.6 μm could be generated using the micromixer. The droplet size decreased with increasing total flow and ratio of the flow rates of the two liquids. In addition, a decrease of the droplet size was found when decreasing the channel width of the mixing device. Generally, the silicon oil – dyed water dispersion showed smaller average droplet sizes and were more stable compared to the dispersions based on silicon oil and pure water.
Heterogenic catalytic hydrolysis and analysis of natural pyrethrins in subcritical water coupled with solid phase microextraction (SPME) and GC-MS by Martin Krappe; Steven B. Hawthorne; B. W. Wenclawiak (pp. 625-630).
The natural pyrethrins, cinerin I, jasmolin I and pyrethrin I, have been hydrolyzed to chrysanthemic acid (CA) in subcritical water in the presence of basic alumina. The hydrolysis and extraction was performed in situ with subcritical water. The conversion to acid is reproducible at 200 °C and 30 min with an RSD of 19% (n = 16) at a concentration level of 1.2 × 10–8 mol/L CA and 12% (n = 12) at concentration level of 1.2 × 10–7 mol/L CA. An analytical method using Solid Phase Micro Extraction (SPME) combined with GC-FID or -MSD was developed and optimized. For SPME an equilibration time of 20 min at pH of 2 was required. Three fibers, 100 μm polydimethylsiloxane (PDMS), 85 μm polyacrylate (PA) and 65 μm carbowax/divinylbenzene (CW) were evaluated. The Carbowax/divinylbenzene fiber has the highest affinity for CA, but the capacity decreases significantly from experiment to experiment. The most reproducible and most stable one was the PDMS fiber. Two internal standards, octanoic acid and cis-chrysanthemic acid, were used because CA degrades slowly at 200 °C in water.This method was applied to analyze some products which contain pyrethrum as an active ingredient, such as insect spray, shampoo against lice, and dried chrysanthemum flowers. The results are comparable to SFC-FID data and correspond to the values given by the manufacturer.
Extraction of oilseeds by SFE – a comparison with other methods for the determination of the oil content by L. Brühl; Bertrand Matthäus (pp. 631-634).
Rapeseed, soybean and sunflower seeds are used for a comparison of solvent extractions by SFE, ASE, fexIKA and Soxtherm apparatus with the official standard method B-I 5 (87) by the DGF. The optimal extraction parameters for each method are evaluated. The extracts are analysed regarding the composition of tocopherols, as a parameter for mild extraction conditions and the content of free fatty acids and diglycerides, as a parameter for the recovery of more polar lipids. The obtained results for oil content using the optimised methods agree well with the standard method. Differences occur in the results of tocopherol composition and free fatty acid and diglyceride contents. The SFE method shows the highest recovery regarding the tocopherol content. The extraction period by SFE is reduced to about 40 min in contrast to 4 h of the DGF standard method. The other methods also provide considerable time reductions, but showed lower tocopherols and free fatty acid contents.
A comparison of the extraction of clove buds with supercritical carbon dioxide and superheated water by A. A. Clifford; Annamaria Basile; Salim H. R. Al-Saidi (pp. 635-637).
Supercritical carbon dioxide and superheated water (subcritical water above 100 °C under pressure) have both been used to extract the buds of cloves (Syzygium aromaticum). The yields of eugenol and eugenyl acetate obtained by these methods and also by steam distillation and liquid solvent (Soxhlet) extraction are similar, but the yields of caryophyllene were lower for the methods using water.
Application of fluid opacity for determining the phase behavior of binary mixtures near their critical loci – CO2 plus ethane and CO2 plus propane by A. Martin; Sigmar Mothes; Gerhard Mannsfeld (pp. 638-640).
The rapid determination of critical data of binary mixtures of carbon dioxide plus propane and carbon dioxide plus ethane has been carried out using the opalescence effect of pure substances or mixtures near their critical loci. The experiments have been performed applying a heatable stainless-steel vessel equipped with two sapphire windows for optical observation of changes of state. The initial two-phase mixture is continuously heated and pressurized. The vessel content increasingly becomes opalescent and the critical point is characterized by a total opacity. Beyond this point the fluid instantly becomes clear; the one-phase supercritical state is reached.
Analysis of volatile varnishes of coated wires by SPME by D. C. Hinz; W. Kwarteng-Acheampong; B. W. Wenclawiak (pp. 641-642).
Metal wires coated with varnishes emit organic compounds with increasing of temperature. The use of headspace-GC/MS in the full scan modus is required to identify these compounds. Solid phase microextraction (SPME) allows to analyze the emissions by GC/MS. The response for headspace/SPME-GC/MS is larger than for headspace-GC/FID although the FID detector is very sensitive.
Extraction of polar and hydrophobic pollutants using accelerated solvent extraction (ASE) by J. Pörschmann; J. Plugge (pp. 643-644).
Accelerated solvent extraction (ASE) shows higher recoveries for PAHs in comparison with traditional Soxhlet extraction, but in a fraction of time and with less solvent consumption. Better recoveries are especially achieved with PAHs of high reactivity, the latter being expressed by the structure-to-count ratio (SCR). To estimate polar pollutants including phenols/benzenediols, the sample was subjected to a combined in-situ derivatization/extraction approach using 2% v/v acetic anhydride in toluene. The main reason for the better recovery obtained in this way, in comparison with the classical ASE approach, is to overcome strong matrix-analyte interactions. Analogously, fatty acids were analyzed as methyl esters obtained by in-situ derivatization/extraction using boron trifluoride.
Determination of VOC contamination in borehole sediments by headspace-SPME-GC analysis by J. Dermietzel; Gabriele Strenge (pp. 645-647).
VOC contaminants in sediments can be transferred to water by simply shaking water/sediment mixtures until an equilibrium distribution has been reached. The VOC components can then be analysed by solid phase microextraction (SPME) from the headspace of the water phase. Equilibration between equal amounts of sediments and increasing volumes of water allows to use the measured concentrations in the aqueous phase for the calculation of the concentrations in the sediment, without applying standards.
Routine analysis of vinicultural relevant fungicides, insecticides and herbicides in soil samples using enhanced solvent extraction (ESE) by A. Rübel; Reinhard Bierl (pp. 648-650).
Parameters affecting the extraction efficiency of various pesticides from a native contaminated soil sample (Corg = 4.4%) using an enhanced solvent extraction (ESE) technique were investigated. The defined settings of temperature (50/150 °C), pressure (180/240 MPa), static and dynamic extraction time (5/15 min and 0/5 min, respectively) yielded results which did not differ significantly (RSD = 5.9–11.8%). In comparison to a classical shake-out extraction method the yielded quantities were on average 14% higher using ESE. The established method achieved a high precision (RSD = 2.8–9.1%) for the pesticides extracted from native contaminated soil samples. A significant influence of the sample matrix on accuracy was not observed. The RSDs of thirteen pesticides extracted from spiked sea sand varied in a similar range from 1.7 to 9.8% and the recoveries were between 83 and 112%. The method has been applied to soil samples from vineyards routinely.
Superheated water extraction, steam distillation and SFE of peppermint oil by Andreas Ammann; Dirk C. Hinz; R. Shane Addleman; Chien M. Wai; B. W. Wenclawiak (pp. 650-653).
Superheated water extraction, steam distillation and supercritical fluid extraction (SFE) are compared for extraction of l-menthol, menthone, eucalyptol and other components of peppermint (mentha piperita) leaves. Different temperatures and pressures were investigated. SFE results at 25/40 °C and 6.5/8/10 MPa were comparable with those reported in the literature. Although SFE is a gentle way of extracting thermally unstable compounds, this method is too slow for commercial use in comparison with steam distillation at 100 °C. Superheated water extraction at 125/150 °C and 1–2 MPa exhibits higher extraction efficiency than the SFE method. Comparison of all experiments under the chosen conditions shows steam distillation to be the most effective extraction method.
Solid-phase microextraction for the assay of clozapine in human plasma by S. Kruggel; S. Ulrich (pp. 654-655).
Solid-phase microextraction (SPME) was investigated as sample preparation for the assay of the neuroleptic drug clozapine in human plasma. A mixture of human plasma, water, loxapine as internal standard and aqueous NaOH was extracted with a 100 μm-polydimethylsiloxane-(PDMS)-fiber for 30 min. The analyte and internal standard were well separated in the gas chromatogram. The calibration was linear and passed the origin. Accuracy and precision as well as the influence of changes of the matrix were investigated. No interfering drug was found. It is concluded that the method can be used in the therapeutic drug monitoring of clozapine.
Design and construction of a reactor-chromatographic system for on-line monitoring of gaseous reaction products by J. C. Medina; D. B. Andrus; C. H. Bartholomew; M. L. Lee (pp. 656-659).
Despite the great interest in coalbed gas formation mechanisms, detailed descriptions of instrumentation used for experimentation in such studies, especially laboratory reactors for measuring reaction rates under well-defined conditions, are scarcely found in the scientific literature. This communication describes the design, construction, and demonstration of a state-of-the-art batch reactor system with on-line analysis and data processing for measurement of gas formation rates. This system features complete on-line GC analysis of the gaseous compounds produced in the reactor as a function of reaction time. It is computer controlled and automated using software written in Visual Basic 5.0. The use of this reaction system is reported here for (1) quantitative analysis of gas-phase products from catalytic hydrogenolysis of hydrocarbons as well as CO2 hydrogenation, (2) real-time measurement of reaction parameters, including temperature and pressure, and (3) qualitative and quantitative analysis of gases desorbed from coal samples.
Interlaboratory comparison study for the determination of halogenated hydrocarbons in water by S. Apfalter; R. Krska; T. Linsinger; A. Oberhauser; W. Kandler; M. Grasserbauer (pp. 660-665).
Sixty laboratories of five different countries participated in a large-scale interlaboratory comparison test for the determination of halogenated hydrocarbons in water. Participants used their in-house method with 44 laboratories applying head space GC ECD analysis and 5 using liquid/liquid extraction. A set of two artificially produced samples was prepared; the halogenated hydrocarbons investigated were trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, trichloromethane, tetrachloromethane, 1,1-dichloroethylene, dichloromethane, dibromochloromethane, bromodichloromethane, 1,2-dichloroethane and tribromomethane. The procedure of sample preparation, storage and distribution was monitored by an extensive quality assurance system including homogeneity tests, stability tests, and trend analysis of the submitted data. The analytical results submitted by the participants exhibited RSD values of up to 35% and outlier rates of up to 19%. The percentage of false positive and false negative results was at the highest 12% for selected substances. Recovery rates varying from 86% to 106% proved the correctness of the analytical results submitted by the participants and showed that the procedure developed in this study for sample preparation and distribution is well suited for the performance of large-scale interlaboratory comparison tests of halogenated hydrocarbons in water.
Fast survey analysis of biomass by-product samples based on ICP optical emission spectra by Rosa Ana Conte; Eric H. van Veen; M. T. C. de Loos-Vollebregt (pp. 666-672).
Prehydrolysate samples from the acidic prehydrolysis of Eucalyptus wood residues were submitted to survey analysis by inductively coupled plasma (ICP) optical emission spectrometry (OES) based on the multicomponent and multiline techniques. The survey analysis software is designed to determine 64 elements. The semiquantitative data obtained for the unknown prehydrolysate samples provided fast and valuable information for the determination of important inorganic constituents (Al, B, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Si, Sr, Zn, Co, Pb, Sn) for further utilisation of the prehydrolysate in the production of fertilisers, animal feed and furfural. To validate the survey analysis approach, the prehydrolysate samples were quantitatively analysed by the standard additions method. For the prehydrolysate samples the relative difference between the results obtained by both techniques was generally ± 25% for the majority of the elements, a typical value for the survey approach. Analyte recoveries in the spiked prehydrolysate samples analysed by the survey approach ranged from 95 to 125%. Independent replicates of prehydrolysate samples were measured over a 15-day period showing relative standard deviations of ≤ 4% for all elements, except for Zn (10%) and S (16%).