Solid-phase Extraction Capillary Electrophoresis Research Articles

Determination of Iodine Species in Seafood by Ionic Liquid–Based In-line Solid-Phase Extraction-Capillary Electrophoresis

Ionic liquid (IL)–based in-line solid-phase extraction (SPE)-capillary electrophoresis (CE) method was developed for determination of three iodine species (3,5-diiodo-l-thyronine, l-tyrosine, 3,5-diiodo-l-tyrosine) in seafood. The background electrolyte (BGE) used was 5 mM sodium tetraborate. The small SPE extractor filled with Oasis HLB sorbent was constructed and embedded 7.5 cm away from the entrance to the capillary, then the ILs were used as eluting solvents to elute analytes and separate the target compounds to improve the detection sensitivity in CE. Several parameters including the elution solvent, the elution time, pH of sample solution, and sample loading time were investigated. The LODs were 0.48 ng/mL for 3,5-diiodo-l-thyronine, 4.7 ng/mL for l-tyrosine, and 5.2 ng/mL for 3,5-diiodo-l-tyrosine under optimal experimental conditions. Compared with normal hydrodynamic injection, sensitivity enrichment factors for this enrichment strategy ranged from 11 to 9635. The in-line SPE-CE method was then applied to analyze kelp and seaweed samples, and the recoveries ranged from 87 to 117%.

Simultaneous determination of three sulfanilamide artificial sweeteners in foodstuffs by capillary electrophoresis coupled with contactless conductivity detection based on porous aromatic frameworks enhanced solid phase extraction

In this paper, a simple and easy method of solid phase extraction (SPE) followed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is evaluated as a novel approach for the simultaneous determination of acesulfame-K (ACE), sodium saccharin (SAC), and sodium cyclamate (CYC) in foodstuffs without derivatization. To reduce the complex matrix interference resulting from the constituents of samples and enriched targets, porous aromatic frameworks (PAFs) enhanced SPE, a suitable sample pretreatment procedure, was introduced. Several factors affecting extraction efficiency and electrophoretic separation were investigated. Additionally, the interaction mechanisms between the host (PAF-6) and guests (ACE, SAC, and CYC) were studied. Under the optimum conditions, three sulfanilamide artificial sweeteners were baseline separated within 8 min, exhibiting a linear calibration over two orders of magnitude (R2 > 0.995). The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with ultraviolet and C4D detection. The proposed SPE–CE–C4D method has been successfully applied to analyse beverage samples and candied fruits with recoveries in the range of 78.89%–92.00%.

Parts-per-trillion detection of harmala alkaloids in Undaria pinnatifida algae by on-line solid phase extraction capillary electrophoresis mass spectrometry

β-carboline alkaloids of the harmala group (HAlks)—a family of compounds with pharmacologic effects—can be found at trace levels (<25 μg kg−1 algae) in the edible invasive algae Undaria pinnatifida, known commonly as wakame. In this study, we present a simple and sensitive method to detect and quantify at low parts-per-trillion levels the six HAlks more frequently found in those plants. The method is based on on-line solid phase extraction capillary electrophoresis mass spectrometry using a C18 sorbent. First, the methodology was optimized and validated with standard solutions through the use of ultraviolet (UV) and mass spectrometry (MS) detection. Second, the optimized method for MS detection was applied to an analysis of the HAlks in U. pinnatifida extracts. The method achieved limits of detection between 2 and 77 pg mL−1 for standards, producing an analyte preconcentration of about 1000-times in comparison to CE-MS. Some matrix effects were observed for the complex wakame extracts, especially for the most polar HAlks (harmol and harmalol), which bear aromatic hydroxyl groups. Harmine, harmaline, and norharmane were not detected in the algal extracts, whereas harmane was found at 70 pg mL−1 (70 ng kg−1 dry algae). The results underscored that C18-SPE-CE-MS may be considered as a powerful method to detect trace levels of alkaloids and other bioactive small molecules in complex plant extracts.

Developments in coupled solid-phase extraction-capillary electrophoresis 2013-2015.

An overview of the design and application of coupled solid-phase extraction-capillary electrophoresis (SPE-CE) systems reported in the literature between July 2013 and June 2015 is provided in this paper. The present article is a continuation of our previous review papers on this topic which covered the time period 2000-2013 (Electrophoresis 2008, 29, 108-128; Electrophoresis 2010, 31, 44-54; Electrophoresis 2012, 33, 243-250; Electrophoresis 2014, 35, 128-137). The use of in-line and on-line SPE-CE approaches is treated and outlined in this review. Recent advancements, such as, for example, the use of aptamers as affinity material for in-line SPE-CE, the use of a bead string design for in-line fritless SPE-CE, and new interfacing techniques for the on-line coupling of SPE to CE, are outlined. Selected examples demonstrate the applicability of the coupled SPE-CE systems for biomedical, pharmaceutical, environmental, and food studies. A complete overview of the recent SPE-CE studies is given in table format, providing information on sample type, SPE sorbent, coupling mode, detection mode, and LOD. Finally, some general conclusions and perspectives are provided.

A high performance system to study the influence of temperature in on-line solid-phase extraction capillary electrophoresis

A novel high performance system to control the temperature of the microcartridge in on-line solid phase extraction capillary electrophoresis (SPE–CE) is introduced. The mini-device consists in a thermostatic bath that fits inside of the cassette of any commercial CE instrument, while its temperature is controlled from an external circuit of liquid connecting three different water baths. The circuits are controlled from a switchboard connected to an array of electrovalves that allow to rapidly alternate the water circulation through the mini-thermostatic-bath between temperatures from 5 to 90°C. The combination of the mini-device and the forced-air thermostatization system of the commercial CE instrument allows to optimize independently the temperature of the sample loading, the clean-up, the analyte elution and the electrophoretic separation steps.The system is used to study the effect of temperature on the C18-SPE–CE analysis of the opioid peptides, Dynorphin A (Dyn A), Endomorphin1 (END) and Met-enkephalin (MET), in both standard solutions and in spiked plasma samples. Extraction recoveries demonstrated to depend, with a non-monotonous trend, on the microcartridge temperature during the sample loading and became maximum at 60°C. Results prove the potential of temperature control to further enhance sensitivity in SPE–CE when analytes are thermally stable.

A sheath flow gating interface for the on-line coupling of solid-phase extraction with capillary electrophoresis

A sheath flow gating interface (SFGI) is presented for the on-line coupling of solid-phase extraction (SPE) with capillary electrophoresis (CE). The design, construction and operation of the SFGI are described in detail. After operating conditions were investigated and selected, the SFGI was evaluated on a SPE–CE–UV setup using hydroxylated poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith as the absorbent and using three phenols as the test analytes. The preconcentration factors obtained with the SPE–CE–UV system and the SPE–UV part are 530 and 550, respectively. The plate numbers obtained using the SPE–CE–UV system are slightly better than or comparable to those with the CE–UV part. The precisions (RSDs) of 100 consecutive injections are 2.43%, 3.86%, and 4.25% for peak height, peak area and migration time, respectively. The measured recoveries for the river water samples spiked at three different levels are in the range of 93.6–102.8% with the interday RSD values ranging from 2.0 to 4.5% (n=3). These data collectively demonstrate that the SFGI has the ability to exactly and reproducibly transfer nanoliters of fractions from SPE onto CE with no degradation of the efficiencies of SPE and CE, suggesting a great potential to be routinely used for the coupling of SPE, microcolumn LC or FIA with CE.

Preparation and evaluation of open tubular C18-silica monolithic microcartridges for preconcentration of peptides by on-line solid phase extraction capillary electrophoresis

In this study, C18-silica monoliths were synthesized as a porous layer in open tubular capillary columns, to be cut later into microcartridges for the analysis of neuropeptides by on-line solid-phase extraction capillary electrophoresis with UV and MS detection (SPE-CE-UV and SPE-CE-MS). First, several types of C18-silica monolithic (MtC18) microcartridges were used to analyse standard solutions of five neuropeptides (i.e. dynorphin A (1–7), substance P (7–11), endomorphin 1, methionine enkephalin and [Ala]-methionine enkephalin). The MtC18 sorbents were especially selective against endomorphin 1 and substance P (7–11)). The best results in terms of sensitivity and inter-microcartridge reproducibility were achieved with the microcartridges obtained from a 10-cm open tubular capillary column with a thin monolithic coating with large through-pores (1–5μm). Run-to-run repeatability, microcartridge durability, linearity ranges and LODs were studied by MtC18-SPE-CE-MS. As expected due to their greater selectivity, the best LOD enhancement was obtained for End1 and SP (7–11) (50 times with regard to CE-MS). Finally, the suitability of the methodology for analysing biological fluids was tested with plasma samples spiked with End1 and SP (7–11). Results obtained were promising because both neuropeptides could be detected at 0.05μgmL−1, which was almost the same concentration level as for the standard solutions (0.01μgmL−1).

In-line solid-phase extraction–capillary electrophoresis coupled with mass spectrometry for determination of drugs of abuse in human urine

In-line solid-phase extraction-capillary electrophoresis coupled with mass spectrometric detection (SPE-CE-MS) has been used for determination of 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), codeine (COD), hydrocodeine (HCOD), and 6-acetylmorphine (6AM) in urine. The preconcentration system consists of a small capillary filled with Oasis HLB sorbent and inserted into the inlet section of the electrophoresis capillary. The SPE-CE-MS experimental conditions were optimized as follows: the sample (adjusted to pH6.0) was loaded at 930mbar for 60min, elution was performed with methanol at 50mbar for 35s, 60mmolL(-1) ammonium acetate at pH3.8 was used as running buffer, the separation voltage was 30kV, and the sheath liquid at a flow rate of 5.0μLmin(-1) was isopropanol-water 50:50 (v/v) containing 0.5% acetic acid. Analysis of urine samples spiked with the four drugs and diluted 1:1 (v/v) was studied in the linear range 0.08-10ngmL(-1). Detection limits (LODs) (S/N = 3) were between 0.013 and 0.210ngmL(-1). Repeatability (expressed as relative standard deviation) was below 7.2%. The method developed enables simple and effective determination of these drugs of abuse in urine samples at the levels encountered in toxicology and doping.

Developments in coupled solid‐phase extraction–capillary electrophoresis 2009–2011

This article presents an overview of the design and application of coupled solid-phase extraction-capillary electrophoresis (SPE-CE) systems that have been reported in the literature between January 2009 and July 2011. The present paper is an update of two previous review papers covering the years 2000-2009 (Electrophoresis 2008, 29, 108-128; Electrophoresis 2010, 31, 44-54). Both in-line and on-line SPE-CE approaches are treated and outlined. Attention is paid to emerging technological developments, such as the use of carbon nanotubes and magnetic particles for on-line extraction of sample components prior to CE analysis. Selected examples illustrate the applicability of SPE-CE in biomedical, pharmaceutical, environmental and food analysis. A full overview of recent SPE-CE studies is given in table format, providing information about sample type, SPE sorbent, coupling mode, detection mode and limit of detection. Finally, some general conclusions and future perspectives are given.

Rapid and sensitive determination of posaconazole in patient plasma by capillary electrophoresis with field-amplified sample stacking

The high morbidity and mortality associated with invasive fungal infections have increased the importance of improving treatment efficacy. Posaconazole is a novel agent with strong antifungal activity and low toxicity. The success of posaconazole pharmacotherapy strongly depends on precise controlling of concentration of the drug in the blood. In the present study, a solid phase extraction-capillary electrophoresis (SPE-CE) method was developed for rapid and accurate determination of posaconazole in the plasma of patients. We used the field-amplified sample stacking (FASS) technique to improve the sensitivity of CE, and applied the SPE procedures to reduce the matrix effect that was frequently encountered by biological samples in FASS system. Effect of filter types on the recovery rate of compounds with high lipophilicity was carefully investigated. Parameters affecting FASS performance were all optimized to obtain the best sensitivity with the highest speed. When using 1.25M formic acid as the background electrolyte and 0.2M formic acid in 95% (v/v) methanol as the sample solution, the limit of detection (LOD) for posaconazole was 10ngmL−1, with an analytical run time of less than 5min. The relative standard deviation (RSD) of the peak area ratios for repeatability (intra-day, n=6) and intermediate precision (inter-day, n=3) were lower than 7.2% and 7.5%, respectively. The accuracy was tested by recovery, and the recovery rates were within 95.1% and 106.4%, respectively. The successful application of the developed method demonstrated its feasibility as an effective method for clinical use.

Transient isotachophoresis in on‐line solid phase extraction capillary electrophoresis time‐of‐flight‐mass spectrometry for peptide analysis in human plasma

In this study, we evaluated the combination of transient isotachophoresis with on-line solid-phase extraction capillary electrophoresis time-of-flight mass spectrometry (SPE-tITP-CE-TOF-MS) to improve sensitivity of peptide analysis, using several opioid peptides as model compounds. First, standard solutions were analyzed in order to establish the tITP-CE methodology using UV and TOF-MS detection. The volume and composition of the leading and terminating electrolytes (i.e. LE and TE) for an efficient tITP were investigated to obtain optimum detection sensitivity and electrophoretic separation. In the best cases, LODs in tITP-CE-TOF-MS were tenfold better than those obtained in CE-TOF-MS (i.e. 5 versus 50 ng/mL). Afterwards, the tITP-CE-TOF-MS methodology was adapted to perform SPE-tITP-CE-TOF-MS. Repeatability, linearity and LODs were investigated and compared to the values obtained by SPE-CE-TOF-MS. Furthermore, human plasma samples fortified with the opioid peptides were analyzed in order to show the potential of SPE-tITP-CE-TOF-MS for peptide analysis in biological fluids. The LODs attained in standard solutions and plasma samples for some of the studied peptides (i.e. 0.01 and 0.1 ng/mL, respectively) were tenfold better than those obtained in SPE-CE-TOF-MS, proving the enhanced sensitivity that could be achieved when both on-line preconcentration approaches were combined together.

Determination of Melamine Residue in Liquid Milk by Capillary Electrophoresis with Solid-Phase Extraction

A novel solid-phase extraction-capillary electrophoresis (SPE-CE) method was developed for the determination of melamine residue in liquid milk. The conditions of SPE and CE were investigated and optimized. A 1% trichloroacetic acid plus 2.2% lead acetate solution were used for the extraction of analyte and the removal of protein. A Cleanert PCX SPE cartridges column was used for clean up. The 50 mM sodium dihydrogenphosphate running buffer (pH adjusted to 3.2 with citric acid) was used as a running buffer. The linearity is satisfactory in the range of 0.8-100 μg/mL with a correlation coefficient of 0.9998. Under the optimal conditions, the method limit of detection (LOD) and method limit of quantification were 0.12 mg/kg and 0.37 mg/kg, respectively. The recovery of melamine from different liquid milk samples was in the range of 89.5-98.5% with a relative standard deviation of 1.8-3.5%. The intra- and inter-day assay precision was 2.8% (n = 6) and 4.1% for five days, respectively. The developed method has been applied successfully for the determination of melamine residue in liquid milk samples. The results obtained by the proposed method agree with those obtained by high-performance liquid chromatographic method. The proposed method enables the quantitative determination of melamine residues at levels as low as 0.37 mg/kg in different liquid milk.

Determination of sulfonamide residues in water samples by in-line solid-phase extraction-capillary electrophoresis

An in-line solid-phase extraction-capillary electrophoresis method with UV–vis detection was developed for the monitoring of residues of five sulfonamides (sulfadoxin, sulfadimethoxine, sulfamerazine, sulfachloropyridazine and sulfamethoxazole) in tap, bottled mineral and river waters. For this purpose an analyte concentrator was constructed, based on the introduction of a small portion of a solid-phase extraction sorbent into the electrophoretic capillary to carry out an in-line concentration step, improving sensitivity. A detailed study was carried out to optimize parameters affecting the in-line solid-phase extraction process, such as the design of the concentrator device, type of sorbent and conditions of elution and injection. The proposed method is simple for the environmental monitoring of these antibiotic residues in waters, allowing the direct injection of the samples without any off-line pretreatment and achieving limits of detection between 0.3 and 0.6 μg/L. Recoveries ranging 52.2–109.2% and relative standard deviations below 13.4% were obtained.

Selective extraction and elution of weak bases by in-line solid-phase extraction capillary electrophoresis using a pH step gradient and a weak cation-exchange monolith

A polymer monolith bearing weak cation-exchange functionality was prepared for the purpose of demonstrating pH-selective extraction and elution in in-line solid-phase extraction-capillary electrophoresis (SPE-CE) utilising a model set of cationic analytes, namely imidazole, lutidine and 3-phenylpropanamine. Optimization of the electrolyte conditions for efficient elution of the adsorbed analytes using a moving pH boundary required that the capillary and monolith be filled with 44 mM sodium acetate at high pH (pH 6) and a low pH electrolyte of 3 mM sodium acetate pH 3 was placed in the electrolyte vials. This combination allowed the adsorbed analytes to be simultaneously eluted and focused into narrow bands, with peak widths of the eluted analytes having a baseline width of 1.2 s immediately after the monolith. Using these optimum elution conditions, the versatility of the SPE-CE approach was demonstrated by removing unwanted adsorbed components after extraction with a wash at a different pH and also by selecting a pH at which only some of the model weak bases were ionised. The analytical performance of the approach was evaluated and the relative standard deviation for peak heights, peak area and migration times were in the ranges of 1.4-5.3, 1.2-3.3 and 0.4-1.2% respectively. Analytes exhibited linear calibrations with r(2) values ranging from 0.996 to 0.999 over two orders of magnitude. Analyte pre-concentration provided excellent sensitivity, and limits of detection for the analyte used in this study were in the range 8.0-30 ng ml(-1), which was an enhancement of 63 when compared to normal hydrodynamic injection occupying 1.3% of the capillary of these bases in water.

Capillary electrophoresis of neurotransmitters using in-line solid-phase extraction and preconcentration using a methacrylate-based weak cation-exchange monolithic stationary phase and a pH step gradient

A novel approach for in-line solid-phase extraction capillary electrophoresis (SPE-CE) for basic analytes was developed. The method is based on the use of a weak cation-exchange monolith synthesised in situ in the front end of the CE capillary via photoinitiated polymerization to form poly(methacrylic acid- co-ethylene glycol dimethacrylate), which was used to create the SPE phase in-line with the CE separation capillary. The monolithic SPE material exhibited a surface area of 23.1 m 2/g and a capacity of 403 nM for dopamine. Adsorption of the analytes as protonated, cationic species onto the SPE phase was achieved using an electrolyte of 6 mM phosphate and 12 mM sodium ion, buffered at pH 7.0, which is above the p K a of the monolith but below the p K a of the analytes. Elution of the analytes from the SPE phase was achieved using an electrolyte with a pH below that of the p K a of the monolith, namely 12 mM phosphate and 12 mM sodium ion, buffered at pH 3.0. Due to the discontinuous electrolyte combination, analytes were simultaneously eluted and focused as the electrophoretically mobilised pH step boundary moved through the SPE monolith, after which the analytes were separated by conventional CZE in the remainder of the capillary. Quantitative extraction from a solution of 0.5 μg/ml dopamine and epinephrine was achieved when flushing up to 15 column volumes of sample through the capillary. The limits of detection ( S/ N = 3) for dopamine and epinephrine were 3.7 and 4.3 ng/ml, and this method provided a sensitivity enhancement for dopamine of 462 times compared to CZE using hydrodynamic injection. The developed method was used to preconcentrate a test mixture of neurotransmitters comprising dopamine, epinephrine, 5-hydroxytryptamine, metanephrine and also histamine. The applicability of this approach to real life samples was demonstrated by using a urine sample from a healthy person to detect dopamine at sub-ppm levels.

Recent advances in coupling solid-phase extraction and capillary electrophoresis (SPE–CE)

Solid-phase extraction (SPE) is a good strategy for overcoming the low sensitivity of capillary electrophoresis (CE). Here, we present a critical review of applications of coupling between SPE and CE reported between 2000 and March 2007. We highlight selected developments and advances and focus on various combinations of these two techniques, which include at-line, in-line and on-line modes of SPE–CE. We discuss the advantages and the drawbacks of the different set-ups and methodologies. We also outline novel trends in SPE–CE coupling.

Poly(dimethylsiloxane)-Based Microchip for Two-Dimensional Solid-Phase Extraction-Capillary Electrophoresis with an Integrated Electrospray Emitter Tip

A microchip in poly(dimethylsiloxane) (PDMS) for in-line solid-phase extraction-capillary electrophoresis-electrospray ionization-time-of-flight mass spectrometry (SPE-CE-ESI-TOF-MS) has been developed and evaluated. The chip was fabricated in a novel one-step procedure where mixed PDMS was cast over steel wires in a mold. The removed wires defined 50-microm cylindrical channels. Fused-silica capillaries were inserted into the structure in a tight fit connection. The inner walls of the inserted fused-silica capillaries and the PDMS microchip channels were modified with a positively charged polymer, PolyE-323. The chip was fabricated in a two-level cross design. The channel at the lower level was packed with 5-microm hyper-cross-linked polystyrene beads acting as a SPE medium used for desalting. The upper level channel acted as a CE channel and ended in an integrated emitter tip coated with conducting graphite powder to facilitate the electrical contact for sheathless ESI. An overpressure continuously provided fresh CE electrolyte independently of the flows in the different levels. Further studies were carried out in order to investigate the electrophoretic and flow rate properties of the chip. Finally, six-peptide mixtures, in different concentrations, dissolved in physiological salt solution was injected, desalted, separated, and sprayed into the mass spectrometer for analysis with a limit of detection in femtomole levels.

P.1.062 Anti-immobility effects of β-carbolines in the mouse forced swim test

β-carboline alkaloids of the harmala group (HAlks)—a family of compounds with pharmacologic effects—can be found at trace levels (<25 μg kg−1 algae) in the edible invasive algae Undaria pinnatifida, known commonly as wakame. In this study, we present a simple and sensitive method to detect and quantify at low parts-per-trillion levels the six HAlks more frequently found in those plants. The method is based on on-line solid phase extraction capillary electrophoresis mass spectrometry using a C18 sorbent. First, the methodology was optimized and validated with standard solutions through the use of ultraviolet (UV) and mass spectrometry (MS) detection. Second, the optimized method for MS detection was applied to an analysis of the HAlks in U. pinnatifida extracts. The method achieved limits of detection between 2 and 77 pg mL−1 for standards, producing an analyte preconcentration of about 1000-times in comparison to CE-MS. Some matrix effects were observed for the complex wakame extracts, especially for the most polar HAlks (harmol and harmalol), which bear aromatic hydroxyl groups. Harmine, harmaline, and norharmane were not detected in the algal extracts, whereas harmane was found at 70 pg mL−1 (70 ng kg−1 dry algae). The results underscored that C18-SPE-CE-MS may be considered as a powerful method to detect trace levels of alkaloids and other bioactive small molecules in complex plant extracts.

Characterization of a solid-phase extraction device for discontinuous on-line preconcentration in capillary electrophoresis-based peptide mapping

Peptide mapping by capillary electrophoresis (CE) with UV detection is problematic for the characterization of proteins that can only be obtained at low micromolar concentrations. Dilution of peptide fragments during digestion of the protein can further reduce the detection sensitivity in peptide mapping to the point where analysis at sub-micromolar concentrations is not possible. A remedy to this problem is preconcentration (sample enrichment) of the proteolytic digest by solid-phase extraction (SPE). To minimize non-specific adsorptive losses during sample handling, on-line SPE–CE is preferred. However, packed-inlet SPE–CE is not always feasible due to either instrument or sample limitations. We describe here a simple method of preconcentration by discontinuous on-line SPE–CE, specifically applied to peptide mapping in low-pH separation buffer after protein digestion in a solid-phase enzyme microreactor. The SPE–CE system does not require application of a low pressure during electrophoretic separation to overcome reversed electroosmotic flow because the preconcentrator device is disconnected from the separation capillary before the electric field is applied. Up to a 500-fold preconcentration factor can be achieved with this device, which can be reused for many samples. Parameters such as the volume of desorption solution, the adsorption/desorption (chromatographic) process, reproducibility of packing the SPE preconcentrator and effects of sample concentration on the peptide map are investigated.

Development of a urinary free cortisol assay using solid-phase extraction–capillary electrophoresis

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE–CE method for the rapid analysis of UFC. UFC was concentrated using SPE C 18 cartridges (3M Empore) under a vacuum and eluted with acetonitrile–SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile–SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10–15 min with a recovery of 89–94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 μg/l with SPE compared to 500 μg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.