Pressurized liquid extraction of lipids for the determination of oxysterols in egg-containing food

Pressurized liquid extraction (PLE, ASE) was compared with the Folch procedure (a solid-liquid extraction with chloroform/methanol 2:1, v/v) for the lipid extraction of egg-containing food; the accuracy of PLE for the quantitative determination of oxysterols in whole egg powder was evaluated. Samples of spray-dried whole egg, an Italian vanilla cake (Pandoro) and egg noodles were used. Two different extraction solvents (chloroform/methanol 2:1, v/v, and hexane/isopropanol 3:2, v/v) were tested at different extraction temperatures and pressures (60 degrees C at 15 MPa, 100 degrees C at 15 MPa, 120 degrees C at 20 MPa). No significant differences in the lipid recovery of the egg powder sample using PLE were found. However, PLE of the vanilla cake and egg noodles with the chloroform/methanol mixture was not selective enough and led to the extraction of a non-lipid fraction, including nitrogen-containing compounds. In the same samples, the pressurized hexane/isopropanol mixture gave a better recovery result, comparable to that obtained using the Folch method. Cholesterol oxidation products of the Folch extract and the pressurized liquid extract of spray dried egg powder (obtained with hexane/isopropanol 3:2, v/v, at 60 degrees C and 15 MPa) were determined by gas chromatography. PLE performed under these conditions is suitable to replace the Folch extraction, because the differences between the two methods tested were not statistically significant. Moreover, PLE shows important advantages, since the analysis time was shortened by a factor of 10, the solvent costs were reduced by 80% and the use of chlorinated solvents was avoided.     

Pressurized liquid extraction in determination of polychlorinated biphenyls and organochlorine pesticides in fish samples

Pressurized liquid extraction (PLE) is a relatively new technique applicable for the extraction of persistent organic pollutants from various matrices. The main advantages of this method are short time and low consumption of extraction solvent. The effects of various operational parameters (i.e. temperature of extraction, number of static cycles and extraction solvent mixtures) on the PLE efficiency were investigated in this study. Fish muscle tissue containing 3.2% (w/w) lipids and native polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and other related compounds was used for testing. Purification of crude extracts was carried out by gel permeation chromatography employing Bio-Beads S-X3. Identification and quantitation of target indicator PCBs and OCPs was performed by high-resolution gas chromatography (HRGC) with two parallel electron-capture detectors (ECDs). Results obtained by the optimized PLE procedure were compared with conventional Soxhlet extraction (the same extraction solvent mixtures hexane–dichloromethane (1:1 v/v) and hexane–acetone (4:1 v/v) were used). The recoveries obtained by PLE operated at 90–120 °C were either comparable to “classic” Soxhlet extraction (for higher-chlorinated PCB congeners and DDT group) or even better (for lower chlorinated analytes). The highest recoveries were obtained for three static 5 min extraction cycles.     

Simultaneous extraction of tocotrienols and tocopherols from cereals using pressurized liquid extraction prior to LC determination

Tocopherols and tocotrienols have been simultaneously determined in food samples using a rapid and simple analytical method including pressurized liquid extraction (PLE) and LC with electrochemical detection. Separation was carried out on a Phenomenex Synergi 4 μm Hydro‐RP 80A column, using a solution of 2.5 mM acetic acid/sodium acetate in methanol/water (99:1, v/v) as mobile phase at a flow rate of 1.0 mL/min. Column temperature was maintained at 30°C. Detection was performed by coulometric detection at 500 mV except for (β+γ)‐tocotrienol, in wheat and rye samples, which was at +350 mV. A palm oil containing a relatively large amount of γ‐tocotrienol and lower concentrations of α‐ and δ‐tocotrienols and α‐ and γ‐tocopherols was used to provide reference retention times for the tocotrienols. Analyte quantification was performed using the external standard method. The calibration equations of tocopherols were used to quantify both tocopherols and their corresponding tocotrienols. The extraction recoveries obtained using the optimized PLE conditions were in the 80–114% range, with RSDs lower than 15%. The method was successfully applied to the determination of tocotrienols and tocopherols in cereal (wheat, rye, barley, maize and oat) and palm oil samples.     

Pressurized liquid extraction versus other extraction techniques in micropreparative isolation of pharmacologically active isoflavones from Trifolium L. species

As a new sample preparation technique, pressurized liquid extraction (PLE), in combination with reversed-phase liquid chromatography (RP-LC) and photodiode-array (PDA) detection were used for the isolation and determination of phytoestrogenic isoflavones in hydrolyzed extracts obtained from aerial parts of five Trifolium L. (clover) species. To optimize the effectiveness of PLE procedure, variable extraction parameters: methanol and acetone (or their 75% aqueous solutions), as extraction solvents, temperatures (75, 100 and 125 °C) and the changeable number of static extraction cycles were tested. Additionally, two other micropreparative techniques: ultrasound-assisted extraction (UAE), and conventional solvent extraction (CSE), under optimized conditions, were also used and compared. Optimum extraction efficiency, expressed in the highest yield of biochanin A, formononetin, daidzein and genistein from plant material, with PLE, using methanol-water (75:25, v/v) as an extraction solvent, an oven temperature of 125 °C and three 5-min static extraction cycles, was obtained.     

Determination of chlormequat and mepiquat in pear,tomato, and wheat flour using on-line solid-phase extraction (Prospekt) coupled with liquid chromatography-electrospray ionization tandem mass spectrometry

A new methodology based on pressurized liquid extraction (PLE) followed by LC-MS is presented for the simultaneous and unequivocal determination of alkylphenol ethoxylates (APEOs) and their degradation products, alkylphenols (APs) and alkylphenoxy carboxylates (APECs), in sediment samples. The protocol, applicable to a full range of APEO oligomers and degradation products, permits the sensitive and selective determination of APEOs (nEO = 1-15), APECs (nEO = 0-1) and APs at low ppb levels (LODs = 1-5 microg/kg) in sediment samples. Optimization of the operational parameters of PLE clearly demonstrates that significant thermal losses of APs occur during extraction at elevated temperatures. The loss of octylphenol (OP) at 100 degrees C was 61.2% and of nonylphenol (NP) 40.0%, whereas other compounds were completely recovered. Thus, to avoid losses due to the volatility of alkylphenols, a low extraction temperature should be applied. The conditions that gave the best results for all target compounds were as follows: extraction solvent mixture, methanol-acetone (1:1, v/v); temperature, 50 degrees C; pressure, 1500 p.s.i.; two static cycles. Using PLE and a subsequent clean-up with solid-phase extraction (SPE), the simultaneous extraction of APEOs, APs and APECs from sediment samples was achieved yielding recoveries >70% and producing low MS background noise. The developed methodology was applied on a routine basis to the analysis of alkylphenolic compounds in sediment samples. APEOs and their persistent degradation products were detected in significant concentrations in sediments from Portuguese rivers, especially at sites situated in the proximity of industrial plants (mainly the textile industry). The total concentration of alkylphenolic compounds (APEOs+APs+APECs) ranged from 155 to 2400 microg/kg. Of all the alkylphenolic compounds, NP comprised 40 to 50% with concentrations up to 1172 microg/kg.     

Pressurized liquid extraction and microwave-assisted extraction in the determination of organochlorine pesticides in fish muscle samples

This paper describes a comparative study of 2 extraction methods, pressurized liquid extraction (PLE) and microwave-assisted extraction (MAE), for the determination of organochlorine pesticides (OCPs) in fish muscle samples. In both cases, samples were extracted with hexane-acetone (50 + 50), and the extracts were purified by solid-phase extraction using a carbon cartridge as the adsorbent. Pesticides were eluted with hexane-ethyl acetate (80 + 20) and determined by gas chromatography with electron-capture detection. Both methods demonstrated good linearity over the range studied (0.005-0.100 microg/mL). Detection limits ranged from 0.029 to 0.295 mg/kg for PLE and from 0.003 to 0.054 mg/kg for MAE. For most of the pesticides, analytical recoveries with both methods were between 80 and 120%, and the relative standard deviations were < 10%. The proposed methods were shown to be powerful techniques for the extraction of OCPs from fish muscle samples. Although good recovery rates were obtained with both extraction methods, MAE provided advantages with regard to sample handling, cost, analysis time, and solvent consumption. Acceptable validation parameters were obtained although MAE was shown to be more sensitive than PLE.     

Selective pressurized liquid extraction of polybrominated diphenyl ethers in fish

A fast and simple method for the analysis of polybrominated diphenyl ethers (PBDEs) in fish samples was developed using a one-step extraction and clean-up by means of pressurized liquid extraction (PLE) combined with gas chromatography-ion trap tandem mass spectrometry (GC-ITMS-MS). The selective PLE method provided to obtain ready-to-analyse extracts without any additional clean-up step, using a sorbent as fat retainer inside the PLE cell. Several PLE operating conditions, such as solvent type, extraction temperature and time, number of cycles and type of fat retainer, were studied. Using Florisil as fat retainer, maximum recoveries of PBDEs (83-108%) with minimum presence of matrix-interfering compounds were obtained using a mixture of n-hexane:dichloromethane 90:10 (v/v) as solvent, an extraction temperature of 100 °C and a static extraction time of 5 min in combination with three static cycles. Quality parameters of the method were established using standards and fish samples. Limits of detection and quantification ranged from 10 to 34 pg g⁻¹ wet weight and between 34 and 68 pg g⁻¹ wet weight, respectively. In addition, good linearity (between 1 and 500 ng ml⁻¹) and high precision (RSD % < 15%) were achieved. The method was validated using the standard reference material SRM-1945 (whale blubber) and was then applied to the analysis of PBDEs in fish samples.     

Off-line coupling of pressurized liquid extraction and LC/ED for the determination of retinyl acetate and tocopherols in infant formulas

An analytical methodology including pressurized liquid extraction (PLE) as sample treatment to isolate retinyl acetate and tocopherols from infant formulas has been developed. The milk extracts were kept at −18 °C for 30 min and after filtration could be injected directly into the chromatographic system. Thus, a rapid and simple routine control method of these products is possible.

The parameters affecting both the extraction process and the liquid chromatography (LC) system were optimized. PLE was performed using one cycle of extraction during a static time of 5 min. Methanol was chosen as the extraction solvent for a temperature of 50 °C. Chromatographic separation was accomplished using a RP-18 column; the mobile phase used was methanol–water (94:6, v/v) containing 2.5 mM acetic acid/sodium acetate buffer. Electrochemical detection in amperometric mode with a glassy carbon electrode at +1100 mV was applied. The proposed methodology was successfully used for the determination of retinyl acetate, δ-tocopherol, (β + γ)-tocopherol and -tocopherol in different infant formulas. The analytes were evaluated in the same chemical form present in the samples. Recoveries were between 92 and 106%. A certified reference material of milk powder was also analyzed.     

Sequential pressurized liquid extraction to determine brain-originating fatty acids in meat products as markers in bovine spongiform encephalopathy risk assessment studies

A new approach using sequential pressurized liquid extraction described recently [J. Poerschmann, R. Carlson, J. Chromatogr. A, 1127 (2006) 18-25] was applied to determine lipid markers originating from central nervous system (CNS) tissue of cows in heat-processed sausages. These studies are very important in quality control as well as risk assessment studies in the face of the bovine spongiform encephalopathy (BSE) crisis. Diagnostic CNS lipid markers, which should not be present in meat products without CNS addition, were recognized on complete transesterification as polar 2-hydroxy-fatty acids (2OH-24:0, 2OH-24:1, 2OH-22:0, 2OH-18:0, shorthand designation) as well as odd-numbered non-branched fatty acids beyond C(22). An array of other fatty acids including lignoceric acid (24:0), nervonic acid (24:1), arachidonic acid (20:4), and polyunsaturated nC(22)-surrogates are strongly related to CNS lipids, but occur as traces in meat products without CNS addition as well, thus reducing their value as diagnostic markers. Samples including meat products without CNS addition, meat with 3% CNS addition, as well as pure CNS homogenates, were subjected to sequential PLE (pressurized liquid extraction) consisting of two steps: n-hexane/acetone 9:1 (v/v) extraction at 50 degrees C to remove neutral lipids, followed by chloroform/methanol 1:4 (v/v) extraction at 110 degrees C to isolate polar CNS lipids (two 10 min PLE cycles each). To enhance the fractionation efficiency, cyanopropyl modified silica as well as chemically not modified silica sorbent was used at the outlet of the PLE cartridge to retard polar lipids in the first extraction step. This method proved superior to widely distributed exhaustive lipid extraction followed by solid-phase extraction (SPE) using silica regarding lipid recoveries and clear-cut boundaries between lipid classes. Methodological studies showed that the alcoholysis using trimethylchlorosilane/methanol (1:9, v/v) is an excellent method for the complete transesterification of lipids and quantitative formation of methyl esters.     

Selective pressurized liquid extraction for multi-residue analysis of organochlorine pesticides in soil

A selective pressurized liquid extraction (SPLE) procedure capable of performing simultaneous extraction and clean-up has been demonstrated for multi-residue analysis of organochlorine pesticides (OCPs) in soil. The final method was performed at 100 degrees C for 3 x 10 min using acetone/n-heptane (1:1, v/v). Florisil was placed inside the extraction cell downstream the sample to remove interfering compounds. Extraction of two soil samples by SPLE gave a recovery which was over 80% for beta-endosulfan, endosulfan sulfate, p,p'-DDT and p,p'-DDE compared to PLE with off-line clean-up. The same trend was observed when applying the SPLE method to a certified reference soil sample (CRM 811-050) containing 13 OCPs, where the SPLE method gave 80-90% recovery vis-à-vis the PLE method with off-line clean-up. Feasibility of the SPLE method was further demonstrated by applying it to five real soil samples collected in Ethiopia.     

Optimizing pressurized liquid extraction of microbial lipids using the response surface method

Response surface methodology (RSM) was used for the determination of optimum extraction parameters to reach maximum lipid extraction yield with yeast. Total lipids were extracted from oleaginous yeast (Rhodotorula glutinis) using pressurized liquid extraction (PLE). The effects of extraction parameters on lipid extraction yield were studied by employing a second-order central composite design. The optimal condition was obtained as three cycles of 15 min at 100°C with a ratio of 144 g of hydromatrix per 100 g of dry cell weight. Different analysis methods were used to compare the optimized PLE method with two conventional methods (Soxhlet and modification of Bligh and Dyer methods) under efficiency, selectivity and reproducibility criteria thanks to gravimetric analysis, GC with flame ionization detector, High Performance Liquid Chromatography linked to Evaporative Light Scattering Detector (HPLC-ELSD) and thin-layer chromatographic analysis. For each sample, the lipid extraction yield with optimized PLE was higher than those obtained with referenced methods (Soxhlet and Bligh and Dyer methods with, respectively, a recovery of 78% and 85% compared to PLE method). Moreover, the use of PLE led to major advantages such as an analysis time reduction by a factor of 10 and solvent quantity reduction by 70%, compared with traditional extraction methods.     

Simultaneous determination of four tanshinones in Salvia miltiorrhiza by pressurized liquid extraction and capillary electrochromatography

A pressurized liquid extraction (PLE) and CEC were developed for the simultaneous determination of four tanshinones (dihydrotanshinone I, cryptotanshinone, tanshinone I, and tanshinone IIA) in Salvia miltiorrhiza. High extraction efficiency (>98.5%) was achieved under the optimum PLE conditions. A good separation was obtained by using a Hypersil C18 capillary (3 microm, 100 microm/25 cm) with a mixture of 30 mM Tris-HCl (pH 8.5)-ACN (1:3, v/v) as BGE solution running at 20 kV and 20 degrees C within 12 min. All the calibration curves showed good linearity (r2 >0.9958) within test ranges. The developed method showed good repeatability for the quantification of four investigated components in S. miltiorrhiza with intra- and interday variations of less than 4.4 and 6.8%, respectively. The validated method was successfully applied to quantify four tanshinones in S. miltiorrhiza, which is helpful to control the quality of S. miltiorrhiza.     

Determination of N-nitroso derivatives of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in soils by pressurized liquid extraction and liquid chromatography-electrospray ionization mass spectrometry

To aid in the evaluation of the potential toxicity of N-nitroso derivatives of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), we describe a pressurized liquid extraction (PLE) followed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for determination of RDX and its N-nitroso derivatives: hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) in soils. Sandy loam soil was spiked with RDX and its N-nitroso derivatives (MNX, DNX, and TNX). Acetonitrile was used as the PLE extraction solvent at 100 degrees C and 1500 psi for 15 min. Florisil was used to cleanup extracts following PLE. Instrumental analysis employed LC-ESI-MS, in which 1mM acetic acid was added to the mobile phase to facilitate formation of acetate adduct ions [M+CH(3)COO](-). The method detection limits (MDLs) for RDX, MNX, DNX, and TNX were 1.46, 1.46, 1.69, and 1.93 ng/g, respectively. High recovery (91.1-108.3%), good precision (RSD: 3.2-12.4%), and reproducibility were achieved. This method proved effective and was applied to monitor the reductive biotransformation of MNX in soils with the presence of earthworms (Eisenia fetida).     

Pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls from contaminated soil

Extraction solvents for pressurized liquid extraction (PLE) used to extract polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) from contaminated soil were investigated. The PCDD/PCDFs and Co-PCBs in Certified Reference Material: CRM 0422 (Forest soil) were extracted using toluene, n-hexane, acetone, acetone/toluene and acetone/n-hexane (1:1, v/v). Soxhlet extraction was the reference method. Results demonstrated that PLE using mixed solvents produced better analyte recoveries than the single solvents. However, these results were lower than those for Soxhlet extraction. Additional extraction cycles using mixed solvents achieved better recovery results. Mixed solvents and several extraction cycles were necessary for satisfactory extraction of more tightly bound PCDD/PCDFs and Co-PCBs from soil.     

Suitability of selective pressurized liquid extraction combined with gas chromatography-ion-trap tandem mass spectrometry for the analysis of polybrominated diphenyl ethers

A one-step extraction and clean-up method using pressurized liquid extraction (PLE) (selective PLE) combined with gas chromatography-ion-trap tandem mass spectrometry (GC-ITMS-MS) was evaluated for the analysis of polybrominated diphenyl ethers (from tri- to hepta-PBDEs) at low concentrations in fish and shellfish samples. To this end, the performance of an on-line PLE extraction/clean-up method and of a classical Soxhlet extraction and clean-up method using a multi-layer modified silica column were compared. The two sample treatment methods provided similar results, although an important reduction in the sample treatment time (40 min per sample) was achieved using the selective PLE method. In addition, the suitability of the PLE combined with GC-ITMS-MS method was evaluated by comparing the results obtained in the analysis of fish samples with those obtained by gas chromatography-high resolution mass spectrometry (GC-HRMS). Good agreement between both techniques was obtained with differences between the mean values of less than 16%. The selective PLE method coupled to GC-ITMS-MS produced accurate results for PBDE determination with low limits of detection (1.0-16.8 pg g⁻¹ wet weight) and quantification (3.1-51 pg g⁻¹ wet weight) as well as good precision (RSD < 16%). This method has been applied to the analysis of PBDEs in fish and shellfish samples collected at fish markets in Catalonia (NE Spain).     

Determination of berberine and strychnine in medicinal plants and herbal preparations by pressurized liquid extraction with capillary zone electrophoresis.

A simple and rapid method for the determination of berberine and strychnine in medicinal plants and herbal preparations for regulatory purposes using a home-made pressurized liquid extraction (PLE) system with capillary zone electrophoresis (CZE) using ultraviolet detection at 254 nm was developed. The effects of pH, concentration of buffer, and organic modifiers in the electrophoretic separation were investigated. The buffer used for CZE contained 50 mM ammonium acetate, pH 3.1. The effect of temperature on the extraction efficiency of strychnine in medicinal plants by PLE was demonstrated. Comparable or higher extraction efficiency was achieved with PLE for strychnine in medicinal plants and berberine in herbal preparations compared to soxhlet extraction. The effect of matrix interference in medicinal plants and herbal preparations containing a number of medicinal plants samples using CZE was investigated by standard additional experiments. The reproducibility of the method using PLE with CZE was found to vary between 2.4 and 10.7% (n = 5/6) for different types of samples on different days.     

Selective pressurized liquid extraction of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls from food and feed samples

Selective pressurized liquid extraction (PLE) of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) from various food and feed samples was performed with a selective PLE method previously developed for bulk PCBs. The method utilizes sulfuric acid impregnated silica inside the extraction cell to oxidize coextracted fat. Extractions were performed at 100 degrees C with n-heptane for 5 min in two cycles. Data obtained by selective PLE combined with gas chromatography/high-resolution mass spectrometry (GC-HRMS) were compared to concentrations derived from reference laboratories applying conventional sample preparation and GC-HRMS. Experiments performed on spiked vegetable oil, naturally contaminated crude fish oil and oil containing compound feed samples showed good results for these relatively simple matrices. The accuracy was generally +/-20% as compared to spiked levels or to values obtained by the reference laboratories. The precision, measured as the relative standard deviation (RSD) for 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalency values (TEQs), was below 10% in all cases. The method was also tested on naturally contaminated herring tissue, chicken tissue, pork tissue and sepiolitic clay, which all caused some trouble. It was observed that sufficient amounts of sodium sulfate should be used for dehydration of tissue samples and additionally, the cells should not be packed too dense in order to avoid suppressed extraction efficiency. Once this was attended to, satisfactory data could be obtained, except for sepiolithic clay. This study demonstrates that selective PLE can be applied with success to a number of food and feed matrices in analysis of PCDD/Fs and dl-PCBs. Since the fat removal step is on-line, the selective PLE method will reduce time and solvent consumption for sample preparation as compared to traditional clean-up.     

Optimization of a pressurized liquid extraction method by experimental design methodologies for the determination of fluoroquinolone residues in infant foods by liquid chromatography

In the present study, we have developed a method based on pressurized liquid extraction (PLE) and liquid chromatography with fluorescence detection (LC-FLD) for the determination of residues of fluoroquinolones (FQs) in infant food products. PLE extraction has been optimized by the application of experimental design methodologies. Initially, a fractional factorial design (FFD) was used to screen the significance of four extraction parameters: solvent composition, temperature, pressure and number of cycles. The most significant factors, identified by ANOVA analysis, were the solvent composition, temperature and pressure, which were further optimized with the aid of a face centred design (FCD) and the desirability function. The optimized operating PLE conditions were as follows: ACN/o-phosphoric acid 50 mM pH 3.0 (80:20, v/v), 80 °C, 2000 psi and three extraction cycles of 5 min. Under these conditions, recoveries of the target FQs varied between 69% and 107% with RSDs below 9%. The whole method was validated according to the Commission Decision 2002/657/EC guidelines. The proposed method has been successfully applied to the analysis of different infant food products bought in local supermarkets and pharmacies. The results showed the presence of residues of enrofloxacin in a non-compliant baby food sample corresponding to a chicken-based formulation, which were also confirmed and quantified by LC–MS/MS analysis.     

Pressurized liquid extraction of pharmaceuticals from sewage-sludge

A method for the quantitative determination of ten pharmaceuticals in sewage sludge was developed by using pressurized liquid extraction (PLE) and HPLC-MS with ESI (HPLC-(ESI)MS). The PLE was optimized with regard to solvents and operational parameters, such as temperature, pressure, extraction time, and purge time. The optimum conditions were: 50 mM phosphoric acid/methanol (1:1 v/v) as the extraction solvent, temperature of 100 degrees C, pressure of 100 bar, extraction time 15 min, 2 cycles, flush volume 150% and purge time 300 s. All recoveries for pharmaceuticals were over 68% except for salicylic acid. The repetitivity and reproducibility between days expressed as RSD was lower than 8% for repetitivity and 10% for reproducibility. The LOD of all compounds was lower than 10 microg/kg of dry weight of sewage sludge. The method was applied to determine the pharmaceuticals in sewage sludge from two domestic sewage treatment plants (STPs). The samples were collected every three months between February 2004 and June 2005. Some pharmaceuticals were determined in the samples and naproxen showed the highest value (242 microg/kg of dry weight).     

Appraisal of “classic” and “novel” extraction procedure efficiencies for the isolation of polycyclic aromatic hydrocarbons and their derivatives from biotic matrices

In this study the extraction efficiency of pressurized liquid extraction (PLE), employing different extraction solvent mixtures under different extraction conditions, was compared with extraction efficiencies of commonly used procedures, Soxhlet extraction and extraction enhanced by sonication. Spruce needles and fish tissue were selected as test samples. Purification of obtained extracts was carried out by gel permeation chromatography (GPC) employing gel Bio-Beads S-X3. Identification and quantitation of target PAHs was performed by high-performance liquid chromatography with fluorescence detection (HPLC–FLD).

Within optimisation of PLE conditions, temperature of extraction, type of solvent, duration and number of static cycles as well as the influence of sample pre-treatment (drying, homogenisation, etc.) were tested. Comparison of the extraction efficiency of PLE with the efficiencies of the other techniques was done under the optimised conditions, i.e. sample slurry obtained by desiccation with anhydrous sodium sulphate, extracted at 100 °C in 1 cycle lasting 5 min. Hexane:acetone (1:1, v/v) was chosen as the most suitable extraction solvent for isolation of analytes from test samples.

Comparison of mentioned isolation techniques with respect to the amount of co-extracts, procedure blank levels and time and solvent volume demands was also done.