Quantification of trovafloxacin in serum by high-performance liquid chromatography with on-line solid-phase extraction

Summary A rapid, simple, accurate and sensitive liquid chromatographic assay with on-line solid-phase extraction is described for determination of trovafloxacin in human serum. Samples were deproteinized with acetonitrile and injected on to an NH₂ extraction column for sample clean-up. Thereafter, an on-line column-switching system was used for quantitative transfer of the drug to a C₁₈ analytical column. Separation was performed by ion-pair chromatography and detection was by ultraviolet absorbance at 275 nm. Recovery was 98.5%. The linear range was from 0.25 to 20μg mL⁻¹, with a correlation coefficient of 0.999. Detection limit was 0.1 μg mL⁻¹ from extraction of 25 μL serum.     

On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography

A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer-acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of phenols, except for the more polar ones. The R.S.D. for a river water sample spiked with phenol and chlorophenols at sub-ppb level was lower than 7% (n=5) and detection limits of 15-100 and 35-150 ng l⁻¹ for tap and river water were obtained, respectively.     

On-line solid-phase extraction and high performance liquid chromatography determination of polycyclic aromatic hydrocarbons in water using polytetrafluoroethylene capillary

Naphthalene, biphenyl, acenaphtene, anthracene and pyrene were extracted from water samples using inner walls of polytetrafluoroethylene capillary. Optimum conditions for sorption, desorption and heart-cutting of the analyte zone were found. Combined on-line solid-phase extraction and HPLC method for determination of these compounds was proposed. Limits of detection were: (μg L⁻¹): 0.4 (naphthalene), 0.3 (biphenyl), 0.6 (acenaphtene), 0.2 (anthracene) and 0.1 (pyrene).     

Determination of carbamate pesticides using micro-solid-phase extraction combined with high-performance liquid chromatography

We describe a simple and sensitive porous polypropylene membrane-protected micro-solid-phase extraction (μ-SPE) approach for the sample preparation and determination of carbamate pesticides in soil samples by high-performance liquid chromatography. The μ-SPE device consisted of C₁₈ sorbent held within a porous polypropylene envelope. In order to achieve optimum performance, several extraction parameters were optimized. Under the most favorable conditions, the extraction efficiency of the μ-SPE was very high, with detection limits in the range of 0.01–0.40 ng g⁻¹. This is more than two orders of magnitude lower than the limits obtained by the United States Environmental Protection Agency Methods 8321A and 8318. A linear relationship was obtained for each analyte in the range of 2 and 200 ng g⁻¹. The relative standard deviation for the analysis of aged soil samples spiked at 5 ng g⁻¹ was ≤11%. The reproducibility of separate μ-SPE device used for experiments was satisfactory (relative standard deviations ranged from 4 to 11%), indicating that the method is reliable for routine environmental analysis.     

Commercial polymeric fiber as sorbent for solid-phase microextraction combined with high-performance liquid chromatography for the determination of polycyclic aromatic hydrocarbons in water

A novel microextraction method making use of commercial polymer fiber as sorbent, coupled with high-performance liquid chromatography-fluorescence detection for the determination of polycyclic aromatic hydrocarbons (PAHs) in water has been developed. In this technique, the extraction device was simply a length (8 cm) of a strand of commercial polymer fiber, Kevlar (each strand consisted of 1000 filaments, each of diameter ca. 9.23 μm), that was allowed to tumble freely in the aqueous sample solution during extraction. The extracted analytes were desorbed ultrasonically before the extract was injected into HPLC system for analysis. Extraction parameters such as extraction time, desorption time, type of desorption solvent and sample volume were optimized. Each fiber could be used for up to 50 extractions and the method showed good precision, reproducibility and linear response within a concentration range 0.05–5.00 μg L⁻¹ with correlation coefficients of up to 0.9998. Limits of detection between 0.4 and 4.4 ng L⁻¹ for seven PAHs could be achieved. The relative standard deviations (n = 3) of this technique were between 2.9% and 12.1%.     

Determination of momordicoside A in bitter melon by high-performance liquid chromatography after solid-phase extraction

Summary Momordicoside A has been determined by solid-phase extraction (SPE) on a Envi Carb cartridge (3 mL, 250mg) then high-performance liquid chromatography (HPLC) on a C₁₈ column (4.6 mm×250 mm, 5 μm particle) with acetonitrile-methanol-50mm potassium dihydrogen phosphate buffer, 25:20:60 (v/v), as mobile phase, at a flow rate of 0.8 mL min⁻¹, and UV detection at 208 nm. The analytical method was shown to be highly reproducible, with precision (asRSD) and accuracy (asRME)<10%, both intra-day and inter-day. Absolute recoveries were >90%. The method was applied to the determination of momordicoside A in various tissues from different varieties of bitter melon from different producing areas.     

Analysis of triazine in water samples by solid-phase microextraction coupled with high-performance liquid chromatography

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the determination of triazine is described. Carbowax/templated resin (CW/TPR, 50 μm), polydimethylsiloxane/divinylbenzene (PDMS/DVB, 60 μm), polydimethylsiloxane (PDMS, 100 μm), and polyacrylate (PA, 85 μm) fibers were evaluated for extraction of the triazines. CW/TPR and PDMS/DVB fibers were selected for further study. Several parameters of the extraction and desorption procedure were studied and optimized (such as types of fibers, desorption mode, desorption time, compositions of solvent for desorption, soaking periods and the flow rate during desorption period, extraction time, temperature, pH, and ionic strength of samples). Both CW/TPR and PDMS/DVB fibers are acceptable; a simple calibration-curve method based on simple aqueous standards can be used. The linearity of this method for analyzing standard solution has been investigated over the range 5-1000 ng mL⁻¹ for both PDMS/DVB and CW/TPR fibers. All the correlation coefficients in the range 5-1000 ng mL⁻¹ were better than 0.995 except Simazine and Atratone by CW/TPR fiber. The R.S.D.s range from 4.4% to 8.8 % (PDMS/DVB fiber) and from 2.4% to 7.2% (CW/TPR fiber). Method-detection limits (MDL) are in the range 1.2-2.6 and 2.8-3.4 ng mL⁻¹ for the two fibers. These methods were applied to the determination of trazines in environmental water samples (lake water).     

Flocculation-ultrasonic assisted extraction and solid phase clean-up for determination of polycyclic aromatic hydrocarbons in water rich in colloidal particulate with high performance liquid chromatography and ultraviolet-fluorescence detection

In the present work, a simple method of sample preparation for the determination of polycyclic aromatic hydrocarbons (PAHs) in water rich in colloidal particulate was developed. The technique was mainly based on the effect of the flocculation of aluminum sulfate and the adsorption of the flocculation aid florisil. The method contained three steps: flocculation, ultrasonic extraction, and solid-phase extraction cleanup. Major parameters of the procedure were optimized with high performance liquid chromatography (HPLC) separation and ultraviolet-fluorescence detection. When 250 mL model sample containing 16 EPA PAHs was processed, the developed method provided detection limits in the range of 0.02–5 ng/L. Both spiked and non-spiked polluted river water samples rich in suspended particles and organic matters were analyzed. Recoveries and relative standard deviations for the 16 PAHs were in ranges of 86–94% and 3–13% (n = 5), respectively.     

Comparison of different sorbents for multiresidue solid-phase extraction of 16 pesticides from groundwater coupled with high-performance liquid chromatography

A procedure based on solid-phase extraction (SPE) followed by high-performance liquid chromatography (HPLC) with diode array detection has been developed for the simultaneous analysis of 16 widely used pesticides in groundwater samples. The compounds analysed were: aldicarb, atrazine, desethylatrazine, desysopropylatrazine, carbofuran, 2,4-D, dicloran, fenitrothion, iprodione, linuron, metalaxyl, metazachlor, phenmedipham, procymidone, simazine and vinclozolin. Five different SPE sorbents, C₁₈ bonded silica (Isolute SPE C18 (EC)), graphitised carbon black (Superclean Envi-Carb), highly cross-linked polystyrene-divinylbenzene (Lichrolut EN), divinylbenzene-N-vinylpyrrolidone (Oasis HLB) and surface modified styrene-divinylbenzene (Strata X), were compared. HPLC separation and quantification of the selected pesticides was carried out under isocratic conditions by means of a new reversed-phase column (Gemini from Phenomenex) based on C₁₈ bonded to organic-silica particles. Oasis HLB and Strata X provided the best results in the preconcentration of 1-l samples, yielding average recoveries higher than 70%, except for phenmedipham that rapidly degrades in groundwater. Detection limits of the target pesticides provided by the proposed SPE-HPLC procedure were between 0.003 and 0.04 μg l⁻¹.     

Analysis of heavy organic pollutants of confined atmospheres

Summary An improved procedure for the determination of the less volatile air pollutants of recycled closed atmospheres by activated carbon-Soxhlet extraction is proposed. After total treatment of desorbate, PAH determination is then accomplished by RP-HPLC using both adsorptiometric and fluorimetric UV detection; phenolic compounds are determined by GC-MS.This technique is suitable for very low levels of PAH and phenolic compounds.     

Application of a polysiloxane-based extraction method combined with column liquid chromatography to determine polycyclic aromatic hydrocarbons in environmental samples

Silicone rods with a diameter of 1 mm and 10 mm long were used to extract polycyclic aromatic hydrocarbons (PAHs) from water samples and for the rapid screening of highly contaminated waste material. The rods were placed in a 15 ml glass vial for the extraction of the analytes, which involved shaking (300 min⁻¹) the sample for 3 h. After extraction the rods were placed into 250 μl inserts of 2 ml vials filled with 100 μl of an acetonitrile-water mixture (4:1) and desorption was performed with sonication for 10 min. Then the PAHs were determined using LC and fluorescence detection. Recoveries of the rod extraction ranged between 62 and 97% and the detection limits were between 0.1 and 1.2 ng l⁻¹. These results are comparable with those of stir bar sorptive extraction (SBSE). Although the rods are reusable, their low price means they can be discarded if contaminated, eliminating the need for expensive cleaning. One disadvantage compared to SBSE is the longer extraction time needed to reach equilibrium.     

Application of copolymer coated frits for solid-phase extraction of poly cyclic aromatic hydrocarbons in water samples

A conducting copolymer of pyrrole and phenol was electrochemically synthesized on steel frits as a sorbent. The applicability of the frit was assessed for the solid-phase extraction of trace amounts of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples followed by HPLC–UV. The coating produced was very adherent and the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and FTIR spectrum for the coated frit were studied. The effects of various parameters on the efficiency of the solid-phase extraction process, such as the sample loading rate, elution solvent type, salt effect, volume and flow rate of sample and elution solvent were investigated. Under the optimal conditions, the calibration curves were obtained in the range of 0.1–500 ng mL⁻¹ (r² > 0.98) and the LODs (S/N = 3) were obtained in the range of 0.01–0.08 ng mL⁻¹. Relative standard deviations (RSDs) for intra- and inter-day precision were 2.7–10.2% and 3.6–11.4%, respectively. The recoveries (8 and 40 ng mL⁻¹) ranged from 79% to 115%. The simplicity of experimental procedure, short sample analysis, high extraction efficiency, and the use of low-cost adsorbent show the potential of this method for routine analysis of PAHs in real samples.     

Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction techniques for sample clean-up

Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 g/ml concentration range; the limit of detection was 5 ng/mL.     

Determination of polycyclic aromatic hydrocarbons in water samples using high-performance liquid chromatography with amperometric detection

The determination of polycyclic aromatic hydrocarbons (PAHs) using high-performance liquid chromatography (HPLC) with UV and fluorescence detection has been well established. Although most of the PAHs can be detected by these methods, some environmentally important polyaromatic compounds, such as acenaphthylene, do not show fluorescence and can only be determined by UV detection at higher concentrations. A sensitive and selective determination of acenaphthylene, acenaphthene and the six PAHs listed in the TVO, the German drinking water standard, is also possible by amperometric detection following HPLC separation. The method was applied to the determination of PAHs in different water samples after solid-phase extraction (SPE). The efficiency of the amperometric determination was found to be superior to UV detection (λ = 300 nm).     

Analysis of sulfamerazine in pond water and several fishes by high-performance liquid chromatography using molecularly imprinted solid-phase extraction

The synthesis and evaluation of a molecularly imprinted polymer (MIP) used as a selective solid-phase extraction sorbent and coupled to high-performance liquid chromatography (HPLC) for the efficient determination of sulfamerazine (SMR) in pond water and three fishes are reported. The polymer was prepared using SMR as the template molecule, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the crosslinking monomer in the presence of tetrahydrofuran as the solvent. The SMR-imprinted polymers and nonimprinted polymers were characterized by FT-IR and static adsorption experiments. The prepared SMR-imprinted material showed a high adsorption capacity, significant selectivity and good site accessibility. The maximum static adsorption capacities of the SMR-imprinted and nonimprinted materials for SMR were 108.8 and 79.6 mg g⁻¹, respectively. The relative selectivity factor of this SMR-imprinted material was 1.6. Several parameters influencing the solid-phase extraction process were optimized. Finally, the SMR-imprinted polymers were used as the sorbent in solid-phase extraction to determine SMR in pond water and three fishes with satisfactory recovery. The average recoveries of the MIP-SPE method were 94.0% in ultrapure water and 95.8% in pond water. Relative standard deviations ranging from 0.3% to 5.2% in MIP were acquired. The results for the SMR concentrations in crucian, carp and wuchang fish were 66.0, 127.1 and 51.5 ng g⁻¹, respectively. The RSDs (n = 5) were 3.51%, 0.53% and 5.08%, respectively. The limit of detection (LOD) for SMR was 1 ng g⁻¹ and the limit of quantitation (LOQ) was 3.5 ng g⁻¹.     

Study of solid-phase extraction for the determination of sequestering agents in river water by high-performance liquid chromatography

Anion-exchange solid-phase extraction accompanied with high-performance liquid chromatography has been developed for the determination of six kinds of aminopolycarboxylic acids (APCAs) in river water [N-(2-hydroxyethyl)ethylenediaminetriacetate (HEDTA), ethylenediaminetetraacetate (EDTA), 1,3-propanediaminetetraacetate (PDTA), diethylenetriaminepentaacetate (DTPA), 1,2-propanediaminetetraacetate (MeEDTA), and O,O′-bis(2-aminoethyl)ethyleneglycoltetraacetate (GEDTA)]. The enrichment of APCAs using an anion-exchange cartridge was successfully done by the removal of anions, which competed with APCAs in anion-exchange processes. Barium chloride solution was added to river water and the mixture was passed through On Guard II Ag and H cartridges and then a Bond Elut Jr.SAX cartridge to enrich APCAs. After elution, APCAs were analyzed on two reversed phase C30 columns connected in series and detected with ultraviolet detection. The enrichment using solid-phase extraction permitted the determination of APCAs in river water at concentrations as low as 1 nM. Good recoveries (83–111%) were obtained for each APCA by the standard addition method on three river water samples with high accuracy (RSD 1.8–9.5%). Applying this method, two kinds of APCAs, EDTA and DTPA, were determined in samples from the Oyabe and Senbo Rivers in Japan.     

Evaluation of eggshell membrane-based bio-adsorbent for solid-phase extraction of linear alkylbenzene sulfonates coupled with high-performance liquid chromatography

The potential of eggshell membrane (ESM) as a novel solid-phase extraction bio-adsorbent was investigated in the present study. The ESM with a unique structure of intricate lattice network showed a predominant ability to capture linear alkylbenzene sulfonates (LAS) as a model of organic pollutants by the hydrophobic interactions between ESM and LAS molecular at pH very close to the isoelectric point of ESM, which was similar to the most widely used trapping mechanism for SPE. Under the optimal conditions, the breakthrough capacities of the ESM packed cartridge for C10–C13 LAS homologues were found to be 30, 53, 50, and 43 μg g⁻¹, respectively. On the basis of high-performance liquid chromatography separation and UV detection of LAS homologues, the proposed system could respond down to 0.027 ng mL⁻¹ of LAS with a linear calibration range from 0.2 to 100 ng mL⁻¹, showing a good LAS enrichment ability of eggshell membrane biomaterial with high sensitivity, and could be successfully used for the detection of residual LAS in environmental water samples. The reproducibility among columns was satisfactory (RSD among columns is less than 10%). A comparison study with ESM, C8 and C18 as adsorbents for LAS demonstrated that ESM-based bio-adsorbent was advantageous over C8 and C18, the widely used traditional adsorbents.     

The determination of organochlorine pesticides based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography

A rapid technique based on dynamic microwave-assisted extraction coupled with on-line solid-phase extraction of high-performance liquid chromatography (DMAE-SPE-HPLC) has been developed. A TM₀₁₀ microwave resonance cavity built in the laboratory was applied to concentrate the microwave energy. The sample placed in the zone of microwave irradiation was extracted with 95% acetonitrile (ACN) aqueous solution which was driven by a peristaltic pump at a flow rate of 1.0 mL min⁻¹. The extraction can be completed in a recirculating system in 10 min. When a number of extraction cycles were completed, the extract (1 mL) was diluted on-line with water. Then the extract was loaded into an SPE column where the analytes were retained while the unretained matrix components were washed away. Subsequently, the analytes were automatically transferred from the SPE column to the analytical column and determined by UV detector at 238 nm. The technique was used for determination of organochlorine pesticides (OCPs) in grains, including wheat, rice, corn and bean. The limits of detection of OCPs are in the range of 19-37 ng g⁻¹. The recoveries obtained by analyzing the four spiked grain samples are in the range of 86-105%, whereas the relative standard deviation (R.S.D.) values are <8.7% ranging from 1.2 to 8.7%. Our method was demonstrated to be fast, accurate, and precise. In addition, only small quantities of solvent and sample were required.     

Determination of clozapine in human plasma by solid-phase extraction and liquid chromatography with amperometric detection

Summary A sensitive and selective high-performance liquid chromatographic method has been developed for monitoring clozapine levels in human plasma. Chromatography was performed on a reversed-phase column (C₈, 150 mm×4.6 mm i.d., 5 μm) with acetonitrile-aqueous sodium acetate solution, 88∶12 (v/v), as mobile phase; the flow rate was 1 mL min⁻¹. Clozapine oxidation at +800 mV was detected amperometrically. Response was linearly dependent on concentration over the range 50–1500 ng mL⁻¹ clozapine in plasma. Sample preparation by solid-phase extraction before HPLC analysis gave high extraction yield (94%). The accuracy and precision of the method were both very good (recovery: 97%;RSD<3.3%).     

Homogeneous liquid–liquid extraction combined with high performance liquid chromatography–fluorescence detection for determination of polycyclic aromatic hydrocarbons in vegetables

In this article, homogeneous liquid–liquid extraction (HOLLE), combined with HPLC-fluorescence detector (HPLC-FLD), has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in vegetables. ACN was used as extraction solvent for the extraction of target analytes from vegetables. When the previous extraction process was over, the ACN extract was transferred to the water-immiscible organic phase, tetrachloroethane, used as extraction solvent in HOLLE procedures. Under the optimum conditions, repeatability was carried out by spiking PAHs at concentration level of 12.5 μg/kg, the RSDs varied between 1.1 and 8.5% (n = 3). The LODs, based on S/N of 3, ranged from 0.025 to 0.25 μg/kg. Relative recoveries of PAHs from cucumber and long crooked squash samples were in the range of 72.4–104.9% and 65.5–119.3%, respectively. Compared with the conventional extraction method, the proposed method has the advantage of being quick, easy to operate, and having low consumption of organic solvent.