Coupling of a Modified In-Tube Solid Phase Microextraction Technique with High Perfor- mance Liquid Chromatography-Fluorescence Detection for the Ultra-Trace Determination of Polycyclic Aromatic Hydrocarbons in Water Samples

A modified in-tube solid phase microextraction (SPME) technique in conjunction with a high performance liquid chromatography (HPLC) was developed for the trace determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction device contained a regular HPLC syringe, replacing the metallic needle by two concentric fused silica capillary tubes. The capillary tubes were coated with polydimethylsiloxane (PDMS) as the sorbent and were attached to the syringe by a homemade interface made from polyether ether ketone (PEEK). The sorption of analytes was achieved by frequent withdrawing and ejecting the water sample from/into a vial via the capillary tubes. For the desorption step, an aliquot of organic solvent was withdrawn and subsequently injected directly into the HPLC system. Limits of detection for the elected PAHs were between 0.001 and 0.006 g L^–1 with a RSD of 2.6–6.3%.     

Multi-residue-analysis of pesticides by HPLC after solid phase extraction

Summary HPLC is a good method for analyzing a broad variety of different pesticides in drinking and surface water. Due to a high enrichment factor in solid phase extraction and the sensitive detection in the UV-range many pesticides can be determined even at a concentration lower than 0.05 g/l. By the use of a diode-array-detector a good security is reached for the identification of substances.     

Design and application of a post-column extraction system compatible with miniaturized liquid chromatography

An on-line, post-column, extraction system suitable for use with miniaturized HPLC (0.7–1 mm i.d. columns) is described. The system consists of a 30° angle segmenting tee, a PTFE extraction coil of variable length and a membrane phase separator. The internal volume of the phase separator is less than 1 l. The total variance contribution of the system is between 1 and 6 sec².The determination of the anti-cancer drugs VP 16 and VM 26 in urine by means of reversed-phase HPLC and fluorescence detection, using both on-column preconcentration and the present miniaturized post-column extraction system is presented as an application.     

Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples

Summary A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25g L^–1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations.     

Analysis of ethoxylated alcohol surfactants in water by HPLC

Summary An HPLC procedure for the determination of linear alcohol polyethoxylates in surface water, waste water, and detergents is described. After extraction of the alcohol ethoxylates into an organic phase the alcohol ethoxylates are derivatized with phenyl isocyanate to apply an UV detection. A reversed-phase HPLC procedure is used to separate different ethoxylate species by their different alkyl chain length. A normal phase procedure is employed to separate alcohol polyethoxylates by their different number of ethoxylate groups in the molecule.     

Determination of hydroxy-s-triazines in water using HPLC or GC-MS

Two methods are described for the routine determination of triazine degradation products in water. After solid phase extraction by means of RP-C₁₈ cartridges, the separation and detection were carried out using either HPLC (for hydroxy-atrazine [OHA], hydroxy-simazine [OHS], hydroxy-propazine [OHP], hydroxy-terbutylazine [OHT] and hydroxy-desethylatrazine [OHDEA]) or GC-MS (only for OHA, OHS, OHP and OHT after methylation with diazomethane). The HPLC set-up is described for detecting the hydroxy-triazines, including hydroxy-desisopropylatrazine (OHDIA), hydroxy-desethyldesisopropylatrazine (OHDEDIA) and cyanuric acid (CA). The average recoveries at concentration levels between 50 ng/L and 1 g/L ranged from 35% to 43% for GC-MS (n=5) and from 53% to 75% for HPLC (n=5) with the exception of hydroxy-desethylatrazine which has been recovered with only 21%. Hydroxy-desisopropylatrazine, hydroxy-desethyldesisopropylatrazine and cyanuric acid could not be enriched on RPC₁₈. The determination limit of the investigated compounds has to be set between 90 and 100 ng/L for both methods for OHS, OHA, OHP and OHT.     

Chromatographic Applications on Monolithic Columns: Determination of Triamcinolone, Prednisolone and Dexamethasone in Pharmaceutical Tablet Formulations Using a Solid Phase Extraction and a Monolithic Column

A method is described for extraction, separation and quantification of 3 corticosteroids in tablets (triamcinolone, prednisolone and dexamethasone). The extraction was achieved using a solid phase extraction (SPE) on RP-18 cartridges. The steroids eluates were examined by HPLC. The chromatographic separation was carried out on Chromolith^® Performance RP-18e column, a new packing material consisting of monolithic rods of highly porous silica, using isocratic binary mobile phase of MeOH and H₂O in the ratio 1: 1. A diode array detector was used at 254 nm for detection. The method was validated for system suitability, linearity, precision, limits of detection, specificity, stability and robustness. The limits of detection were 6.25, 6.25 and 12.50 ng per 25 L injected volumes for them respectively. The recovery values of this method were between 89 and 101% and the reproducibility was within 6.86.     

Quantitative and pharmacokinetic analysis of naloxone in plasma using high-performance liquid chromatography with electrochemical detection and solid-phase extraction

In this study we present a method for measuring naloxone in plasma after intravenous and oral administration of naloxone to humans, in order to study its pharmacokinetic profile. The method consists of a solid-phase extraction step followed by detection on a high-performance liquid chromatographic (HPLC) system equipped with an electrochemical dual-electrode detector. The extraction step employs cyanopropyl columns optimized for naloxone extraction to allow for elution of naloxone by the HPLC mobile phase; this eluate is then directly injected in the HPLC instrument. The HPLC system employs a radial compression phenyl column with a mobile phase containing 18% (v/v) acetonitrile and pentanesulfonic acid as ion-pairing agent; this system shows extraordinary high plate counts for naloxone. The detection limit is 3 ng (signal-to-noise ratio = 3) free naloxone per ml plasma. Following intravenous injection of 30 mg naloxone hydrochloride in two subjects, it was possible to determine the free naloxone concentration in the plasma for 8 h, more than four times the half-life of naloxone in plasma in humans.     

Analysis of reduced glutathione using a reaction with 2,4′-dichloro-1-(naphthyl-4-ethoxy)-s-triazine (EDTN)

A fluorescent adduct was formed between 2,4-dichloro-l-(naphthyl-4-ethoxy)-s-triazine (EDTN) and reduced glutathione in a reaction at 37 °C and pH 9.2. This reaction was used as the basis of an assay for reduced glutathione. The fluorescence was examined at an excitation wavelength of 319 nm and an emission wavelength of 425 nm after extraction of residual unreacted EDTN with methylene dichloride and subsequent dilution of the aqueous phase with ethanol containing 0.01 percent Triton X-100. The reaction rate was low at pH 7 but was accelerated by addition of preparations containing the enzyme glutathione-S-transferase. The adduct gave a discrete peak using isocratic elution with HPLC on a Nova-pak C₁₈ 3 m reverse phase column and a solvent system of methanol: 0.1 M phosphate buffer pH 6.3 (4060). An analytical concentration range of 24 to 240 M reduced glutathione was obtained with an ultraviolet detection system but the concentration range was 7.5 to 75 M when a fluorescence detection system was used. Adducts of other mercapturic acid pathway thiol compounds were not formed at 37 °C under the conditions used and hence did not interfere in the assay. They were formed by heating EDTN and the respective thiol compound at 60 °C for 30 min and they clearly separated from the reduced glutathione compound on HPLC analysis. A strong reaction was observed with digitonin while solutions of tyrosine, at 10 mM concentration, also reacted but these reactants are unlikely to interfere with reduced glutathione analysis in biological systems. When adduct formation was used to estimate reduced glutathione concentrations in some mammalian and plant tissues the reaction using 2,4-dichloro-l-(naphthyl-4-ethoxy)-s-triazine and HPLC separation gave the same results as ano-phthaldialdehyde assay for liver and muscle but the HPLC method gave slightly lower values for other mammalian and plant tissues. The differences were attributed to other material in the tissue extracts which was fluorescing at the same wavelengths as the reduced glutathione adduct.     

In-tube solid phase microextraction using a beta-cyclodextrin coated capillary coupled to high performance liquid chromatography for determination of non-steroidal anti-inflammatory drugs in urine samples

A configuration of in-tube solid-phase microextraction (SPME) coupled to HPLC was constructed by using a pump and a six-port valve combined with a PEEK tube as the pre-extraction segment. The extraction capillary was fixed directly on the HPLC six-port valve to substitute for the sample loop. The whole system could be handled easily to perform accurate on-line extraction, and the possible inaccurate quantification caused by sample/mobile phase mixing when using an autosampler could be eliminated.A β-cyclodextrin coated capillary, prepared by sol-gel method, was used as the extraction capillary for in-tube SPME. Three non-steroidal anti-inflammatory drugs, ketoprofen, fenbufen and ibuprofen, were employed to evaluate the extraction performance of the capillary. After optimizing the extraction conditions, satisfactory extraction efficiency was obtained and detection limits for ketoprofen, fenbufen and ibuprofen in diluted urine samples were 38, 18 and 28 ng/mL, respectively. The extraction reproducibility was evaluated with intra-day and inter-day precision, and the R.S.D.s obtained were lower than 4.9 and 6.9%, respectively. The capillary was proved to be reusable and the extraction efficiency did not decrease after 250 extractions.     

Sol-gel methyl coating in capillary microextraction hyphenated on-line with high-performance liquid chromatography Counterintuitive extraction behavior for polar analytes

A sol-gel coating with anchored methyl groups was developed for capillary microextraction hyphenated on-line with high-performance liquid chromatography (HPLC). This was accomplished by using methyltrimethoxysilane as the sol-gel precursor. The methyl group on the sol-gel precursor ultimately turned into a pendant group on the created sol-gel coating and was primarily responsible for the extraction of nonpolar analytes. A 40-cm segment of 0.25mm I.D. fused silica capillary containing the sol-gel methyl coating on the inner surface was installed as a sampling loop in an HPLC injection port. The analytes were extracted by the coating when an aqueous sample containing the analytes was passed through this capillary. The extracted analytes were then transferred to the HPLC column using isocratic elution with an acetonitrile/water mobile phase. This capillary demonstrated excellent extraction capability for polycyclic aromatic hydrocarbons and ketones. Unexpectedly, this coating also provided good extraction for polar analytes, including aromatic phenols, alcohols, and amines. Considering the fact that the methyl group is nonpolar in nature, such an extraction behavior of sol-gel methyl coating toward polar analytes is counterintuitive. Thus, sol-gel sorbents with short alkyl side chains have the potential to offer a polymer-free alternative to traditional sol-gel capillary microextraction (CME) media commonly prepared with the use of polymers in the sol solution. Elimination of polymers from the sol-gel coating solution is conducive to improving thermal stability and solvent tolerance of the created sol-gel extracting phase. This also makes the preparation of sol-gel coatings facile and cost-effective. Possessing excellent solvent stability, such sol-gel coatings offer the opportunity for effective on-line hyphenation of capillary microextraction with HPLC and other liquid-phase separation techniques that employ organo-aqueous mobile phases.     

Direct determination of the enantiomeric purity of oxyphenonium using chiral HPLC with post-column extraction detection

Summary A method is described for the determination of the enantiomeric purity (enantiomeric excess) of the anticholinergic drug oxyphenonium. The method for this quaternary ammonium compound is based on the direct HPLC analysis with a chiral stationary phase. Two kinds of 1-acid glycoprotein-bonded phases were used.For the detection a post-column extraction with fluorescence detection of the ion-pair counter ion dimethoxyantracene sulphonate was used.     

新型毛细管内固相萃取-气相色谱法检测纺织品中烷基酚类物质

建立了毛细管内固相萃取(SPE)-气相色谱(GC)检测纺织品中壬基酚和辛基酚含量的分析方法。通过比较4种性质不同固相萃取剂的萃取效果,筛选出对烷基酚(APs)类物质萃取效果最佳的固相萃取剂,将其作为填充物质制作毛细管内固相萃取柱,将毛细管内固相萃取法与气相色谱联用进行分析检测。最佳固相萃取剂为Abselut NEXUS,毛细管内固相萃取最佳条件为:1.2 μL甲醇和1.2 μL超纯水活化,1.2 μL甲醇洗脱,上样速率是0.4 μL/min。该法在较低浓度范围内呈现良好的线性相关性,对烷基酚的富集倍数约为100倍,对辛基酚和壬基酚的检出限分别为3.7 μg/L和4.5 μg/L,加标回收率分别为85.6%~98.2%和83.8%~95.7%,结果表明,此法能够简捷、迅速、有效地检测出纺织品中残留的烷基酚类物质。     

Capillary Electrokinetic Chromatography (CEC): An Introduction to a High-Efficiency Microanalytical Technique

Capillary electrokinetic chromatography (CEC, also called capillary electrochromatography) is a relatively new separation technique based on a combination of liquid chromatographic and electrophoretic separation methods. CEC offers both the efficiency of capillary electrophoresis (CE) and the selectivity and sample capacity of packed capillary high performance liquid chromatography (HPLC). These advantages are provided in part because of the favorable flow characteristics of electroosmosis, a method of pumping a liquid by applying a high potential axially to a thin, fluid-filled tube. The speed at which analytes move through the separation conduit under the influence of electroosmosis is quite uniform, regardless of the position of the analyte with respect to adjacent surfaces (within certain limits). This results in very little spreading of zones of analyte; narrow, compact bands of analytes are therefore maintained, which results in high efficiency. Because the capillaries used in CEC are packed with HPLC packing materials, the wealth of selectivities available in HPLC are also available in CEC. The high surface area of these packing materials enables CEC capillaries to accommodate relatively large amounts of sample, making detection a simpler task than it is in capillary electrophoresis (CE). This paper will briefly visit the theory and practice of CEC, and will provide examples of how CEC can be applied in sample analysis.     

Determination of polycyclic aromatic hydrocarbons in atmospheric particulate matter of Valencia city

Summary Polycyclic aromatic hydrocarbons (PAHs) were determined in atmospheric particulate matter in 11 sites of the Valencia area and at several times during the year. Sample analysis was carried out by ultrasonic acetonitrile extraction followed by reverse phase HPLC separation and fluorescence detection. The maximum concentration of total PAH developed in winter and spring. Mean values per sampling site varied from 0.193 to 1.668 g/m³ of filtered air. Environmental noise and temperature were determined at those same 11 sites and correlated with PAH levels.     

Determination of fluoroquinolone antibiotics by microchip capillary electrophoresis along with time-resolved sensitized luminescence of their terbium(III) complexes

We report on the time-resolved detection of the three fluoroquinolone (FQs) antibiotics ciprofloxacin (CIP), enrofloxacin (ENR) and flumequine (FLU). On addition of terbium(III) ions, the terbium(III)-FQs chelates are formed in-situ in an on-capillary derivatization reaction of a microfluidic system. The laser-induced terbium(III)-sensitized luminescence of the chelates is measured at excitation/emission wavelengths of 337/545 nm. The analytes can be separated and quantified within less than 4 min. A solid phase extraction step for analyte preconcentration can be included prior to chelation and microchip capillary electrophoresis. The analytical ranges of the calibration graphs for CIP, ENR and FLU are from 10.6 to 60.0, 10.3 to 51.0, and 11.5 to 58.8 ng mL^?1, respectively, and the detection limits are 3.2, 3.1 and 3.6 ng mL^?1, respectively. The precision was established at two concentration levels of each analyte and revealed relative standard deviations in the range from 3.0 to 10.2 %. The method was applied to the analysis of FQ-spiked water samples. Figure

We report on the time-resolved detection of the three fluoroquinolone antibiotics. The analytes can be separated and quantified within less than 4 min. A solid phase extraction step for analyte preconcentration can be included prior to chelation and microchip capillary electrophoresis.     

Comparison of standard capillary and chip separations of sodium dodecylsulfate-protein complexes

Conditions for converting a set of five standard proteins to electrochemically active sodium dodecylsulfate (SDS) complexes were worked out with the aim of using such complexes for conductivity detection with a a chip electrophoresis system. The results obtained were compared with standard capillary electrophoresis (37 cm (effective length 30 cm)×75 μm I.D. capillary, 10 kV, negative polarity at the inlet). The chip separations were run at 500 V per chip (100 V/cm) as compared to the standard capillary arrangement, which was run at 266.6 V/cm. For the capillary set-up the protein complexes were prepared in aqueous solution (Milli-Q water) made 10 mM with respect to SDS. If the SDS concentration was increased to 50 mM, the separation in the capillary was incomplete. On the other hand with the chip system both approaches yielded acceptable results. The chip separations were slightly (but not distinctly) shorter and offered better separations than the standard set-up. The concentration of the surfactant used for the preparation the complexes results in alternations of the elution sequence, which is preserved if the chip separation is used instead of the capillary set-up. Apparently the full capacity of protein–SDS binding is not exploited for the preparation of the adducts.     

Detection of 1-hydroxypyrene in urine by direct fluorometric analysis on a solid sorbing phase. Validation and application of the method to biological monitoring of PAH-exposed persons

A new method for the detection and quantification of 1-hydroxypyrene (1-OHPy) in the urines of persons exposed to polycyclic aromatic hydrocarbons (PAH) has been evaluated. The method is based on extraction/concentration of the analyte onto a small element cut into tabs from an extraction disk (ENVI-Disk C18 from Supelco) combined with front-face synchronous fluorescence detection and direct quantification on the solid sorbent element. The limit of detection for 1-OHPy was estimated to be about 0.03–0.04 µg/L, a value which is significantly lower than the pyrene metabolite concentration commonly found in unexposed to weakly PAH-exposed persons (0.1–0.3 µg/L). A quantification based on only one standard addition has been adopted and the method was validated both by testing analyte recovery using a known amount of a commercially available pyrene metabolite and by comparing the results with those obtained by high-performance liquid chromatography (HPLC). The results were very close to the HPLC results, the largest deviations being attributed to variations or defects in the stirring system, the rate stability of which was found to be of major importance for the reproducibility and reliability of the measurements. The applicability of the method was further tested by analyzing 1-OHPy in the urine of a volunteer exposed to various automobile traffic zones. The results confirm previous findings which lead to the conclusion that urinary concentrations of PAH metabolites are influenced more by smoking habit than by exposure to urban atmospheric pollution. Thus, the method appears to be an alternative to the usual method based on HPLC. Moreover it presents some advantages, being simple to operate and requiring relatively low-cost instruments.     

Application of microemulsions to the recovery,preconcentration, and determination of ten surfactants from various soils

The application of a microemulsion (ME), consisting of 3% of sodium dodecyl sulfate, 0.8% of benzene, 0.6% of n-butanol, and 90.2% of water, to the extraction of ten polycyclic aromatic hydrocarbons (PAHs) from soil and simultaneous preconcentration of the analytes in the organic phase after separation of the microemulsion is demonstrated. PAHs were determined by HPLC with fluorimetric detection. The recovery rates of PAHs from different types of soil (sand, peat, and clay) are 90–105%. The preconcentration ratios of PAHs in the organic phase formed after the separation of the microemulsion were 5–6.5; the limits of detection were 0.1–0.7 μg/kg. The duration of sample preparation was 20 min.