Analysis of the flame retardant metabolites bis(1,3-dichloro-2-propyl) phosphate (BDCPP) and diphenyl phosphate (DPP) in urine using liquid chromatography–tandem mass spectrometry

Organophosphate triesters tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and triphenyl phosphate are widely used flame retardants (FRs) present in many products common to human environments, yet understanding of human exposure and health effects of these compounds is limited. Monitoring urinary metabolites as biomarkers of exposure can be a valuable aid for improving this understanding; however, no previously published method exists for the analysis of the primary TDCPP metabolite, bis(1,3-dichloro-2-propyl) phosphate (BDCPP), in human urine. Here, we present a method to extract the metabolites BDCPP and diphenyl phosphate (DPP) in human urine using mixed-mode anion exchange solid phase extraction and mass-labeled internal standards with analysis by atmospheric pressure chemical ionization liquid chromatography tandem mass spectrometry. The method detection limit was 8 pg mL⁻¹ urine for BDCPP and 204 pg mL⁻¹ for DPP. Recoveries of analytes spiked into urine ranged from 82 ± 10% to 91 ± 4% for BDCPP and from 72 ± 12% to 76 ± 8% for DPP. Analysis of a small number of urine samples (n = 9) randomly collected from non-occupationally exposed adults revealed the presence of both BDCPP and DPP in all samples. Non-normalized urinary concentrations ranged from 46–1,662 pg BDCPP mL⁻¹ to 287–7,443 pg DPP mL⁻¹, with geometric means of 147 pg BDCPP mL⁻¹ and 1,074 pg DPP mL⁻¹. Levels of DPP were higher than those of BDCPP in 89% of samples. The presented method is simple and sufficiently sensitive to detect these FR metabolites in humans and may be applied to future studies to increase our understanding of exposure to and potential health effects from FRs.     

Molecularly imprinted on-line solid-phase extraction combined with chemiluminescence for the determination of pazufloxacin mesilate

A novel molecularly imprinted polymer solid-phase extraction (MISPE) with flow-injection chemiluminescence (CL) was developed for the determination of pazufloxacin mesilate (PZFX). The molecularly imprinted polymer (MIP) was synthesized by using PZFX as the imprinting molecule. A glass tube packed the particles of the MIP was employed as MISPE micro-column, which was connected into the sampling loop of the eight-way injection valve for on-line selective preconcentration and extraction of PZFX. The eluent of acetonitrile:acetic acid (9:1, v:v) was used as carrier for eluting the adsorbed PZFX to react with the mixture of cerium(IV) and sodium sulfite in the flow cell to produce strong CL. The relative intensity of CL was linear to PZFX concentration in the range from 2.5 × 10⁻⁹ to 2.5 × 10⁻⁷ g mL⁻¹. The limit of detection was 7 × 10⁻¹⁰ g mL⁻¹ (3 σ) and the relative standard deviation for 5 × 10⁻⁸ g mL⁻¹of PZFX solution was 3.7% (n = 7). This method has been applied to the determination of PZFX in human urine.     

Determination and Pharmacokinetic Study of 10-O-Dimethylaminoethylginkgolide B in Rat Plasma by LC–MS

To evaluate the pharmacokinetics of a novel analogue of ginkgolide B, 10-O-dimethylaminoethylginkgolide B (XQ-1) in rat plasma in pre-clinical studies, a sensitive and specific liquid chromatographic method with electrospray ionization mass spectrometry detection (LC–ESI–MS) was developed and validated. After a simple extraction with ethyl acetate, XQ-1 was analyzed on a Shim-pack C18 column with a mobile phase of a mixture of 1 μmol L⁻¹ ammonium acetate containing 0.02% formic acid and methanol (55:45, v/v) at a flowrate of 0.3 mL min⁻¹. Detection was performed in selected ion monitoring (SIM) mode using target ions at [M + H]⁺ m/z 496.05 for XQ-1 and m/z 432.10 for the internal standard (lafutidine). Linearity was established for the concentration range from 2 to 1,000 ng mL⁻¹ . The extraction recoveries ranged from 86.0 to 89.9% in plasma at concentrations of 5, 50, and 500 ng mL⁻¹. The lower limit of quantification was 2 ng mL⁻¹ with 100 μL plasma. The validated method was successfully applied to a pharmacokinetic study after intragastic administration of XQ-1 mesylate in rats at a dose of 20 mg kg⁻¹.     

Enantioselective piezoelectric quartz crystal sensor for d-methamphetamine based on a molecularly imprinted polymer

A piezoelectric quartz crystal (PQC) sensor based on a molecularly imprinted polymer (MIP) has been developed for enantioselective and quantitative analysis of d-(+)-methamphetamine (d(+)-MA). The sensor was produced by bulk polymerization and the resulting MIP was then coated on the gold electrode of an AT-cut quartz crystal. Conditions such as volume of polymer coating, curing time, type of PQC, baseline solvent, pH, and buffer type were found to affect the sensor response and were therefore optimized. The PQC-MIP gave a stable response to different concentrations of d(+)-MA standard solutions (response time = 10 to 100 s) with good repeatability (RSD = 0.03 to 3.09%; n = 3), good reproducibility (RSD = 3.55%; n = 5), and good reversibility (RSD = 0.36%; n = 3). The linear range of the sensor covered five orders of magnitude of analyte concentration, ranging from 10⁻⁵ to 10⁻¹ μg mL⁻¹, and the limit of detection was calculated as 11.9 pg d(+)-MA mL⁻¹ . The sensor had a highly enantioselective response to d(+)-MA compared with its response to l(−)-MA, racemic MA, and phentermine. The developed sensor was validated by applying it to human urine samples from drug-free individuals spiked with standard d(+)-MA and from a confirmed MA user. Use of the standard addition method (SAM) and samples spiked with d(+)-MA at levels ranging from 1 × 10⁻³ to 1 × 10⁻² μg mL⁻¹ showed recovery was good (95.3 to 110.9%).     

Development of a liquid chromatography-mass spectrometry method for the determination of ursolic acid in rat plasma and tissue: application to the pharmacokinetic and tissue distribution study

A fast and sensitive liquid chromatography–mass spectrometry method was developed for the determination of ursolic acid (UA) in rat plasma and tissues. Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was performed on a 3.5 μm Zorbax SB-C18 column (30 mm × 2.1 mm) with a mobile phase consisting of methanol and aqueous 10 mM ammonium acetate using gradient elution. Quantification was performed by selected ion monitoring with (m/z)⁻ 455 for UA and (m/z)⁻ 469 for the IS. The method was validated in the concentration range of 2.5 − 1470 ng mL⁻¹ for plasma samples and 20 − 11760 ng g⁻¹ for tissue homogenates. The intra- and inter-day assay of precision in plasma and tissues ranged from 1.6% to 7.1% and 3.7% to 9.0%, respectively, and the intra- and inter-day assay accuracy was 84.2 − 106.9% and 82.1 − 108.1%, respectively. Recoveries in plasma and tissues ranged from 83.2% to 106.2%. The limits of detections were 0.5 ng mL⁻¹ or 4.0 ng g⁻¹. The recoveries for all samples were >90%, except for liver, which indicated that ursolic acid may metabolize in liver. The main pharmacokinetic parameters obtained were T _max = 0.42 ± 0.11 h, C _max = 1.10 ± 0.31 μg mL⁻¹, AUC = 1.45 ± 0.21 μg h mL⁻¹ and K _a = 5.64 ± 1.89 h⁻¹. The concentrations of UA in rat lung, spleen, liver, heart, and cerebellum were studied for the first time. This method is validated and could be applicable to the investigation of the pharmacokinetics and tissue distribution of UA in rats.     

Study of the metabolism on tobacco-specific N-nitrosamines in the rabbit by solid-phase extraction and liquid chromatography–tandem mass spectrometry

Metabolism of four tobacco-specific N-nitrosamines (TSNAs), N′-nitrosonornicotine (NNN), N′-nitrosoanatabine (NAT), N′-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) has been studied by solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS–MS). 4-(Methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was used as internal standard. SPE and LC–MS–MS was found to be a rapid, simple, sensitive, and selective method for analysis of TSNAs in rabbit serum. The relative standard deviation (R.S.D., n = 6) for analysis of 5 ng mL⁻¹ and 0.5 ng mL⁻¹ standards and of serum sample spiked with 5 ng mL⁻¹ standards of five TSNAs was 2.1–11% and recovery of 5 ng mL⁻¹ standards from serum was 100.2–112.9%. A good linear relationship was obtained between peak area ratio and concentration in the range of 0.2–100 ng mL⁻¹ for NNAL and 0.5–100 ng mL⁻¹ for other four TSNAs, with correlation coefficients (R ²) >0.99 (both linear and log–log regression). Detection limits for standards in solvent were between 0.04 and 0.10 ng mL⁻¹. Doses of TSNAs administered to rabbits via the auricular vein were 4.67 μg kg⁻¹ and 11.67 μg kg⁻¹, in accordance with the different levels in cigarettes. Metabolic curves were obtained for the four TSNAs and for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of NNK; on the basis of these curves we modeled metabolic kinetic equations for these TSNAs by nonlinear curve fitting.     

Simultaneous determination of harpagoside and cinnamic acid in rat plasma by high-performance liquid chromatography: application to a pharmacokinetic study

Radix Scrophulariae (Xuanshen) is one of the famous Chinese herbal medicines widely used to treat rheumatism, tussis, pharyngalgia, arthritis, constipation, and conjunctival congestion. Harpagoside and cinnamic acid are the main bioactive components of Xuanshen. The purpose of this study was to develop an HPLC–UV method for simultaneous determination of harpagoside and cinnamic acid in rat plasma and investigate pharmacokinetic parameters of harpagoside and cinnamic acid after oral administration of Xuanshen extract (760 mg kg⁻¹). After addition of syringin as internal standard, the analytes were isolated from plasma by liquid–liquid extraction. Separation was achieved on a Kromasil C₁₈ column, and detection was by UV absorption at 272 nm. The described assay was validated in terms of linearity, accuracy, precision, recovery, and limit of quantification according to the FDA validation guidelines. Calibration curves for both analytes were linear with the coefficient of variation (r) for both was greater than 0.999. Accuracy for harpagoside and cinnamic acid ranged from 100.7–103.5% and 96.9–102.9%, respectively, and precision for both analytes were less than 8.5%. The main pharmacokinetic parameters found for harpagoside and cinnamic acid after oral infusion of Xuanshen extract were as follows: C _max 1488.7 ± 205.9 and 556.8 ± 94.2 ng mL⁻¹, T _max 2.09 ± 0.31 and (1.48 ± 0.14 h, AUC_0–24 10336.4 ± 1426.8 and 3653.1 ± 456.4 ng h mL⁻¹, 11276.8 ± 1321.4 and 3704.5 ± 398.8 ng h mL⁻¹, and t _1/2 4.9 ± 1.3 and 2.5 ± 0.9 h, respectively. These results indicated that the proposed method is simple, selective, and feasible for pharmacokinetic study of Radix Scrophulariae extract in rats. Figure Radix Scrophulariae     

Chemiluminescence determination of atenolol in biological fluids by a europium-sensitized permanganate-sulfite system

A simple flow injection chemiluminescence (CL) method was developed for the determination of atenolol using Eu³⁺ as the probe. It was found that the weak CL generated by the KMnO₄-Na₂SO₃ reaction can be significantly enhanced by the atenolol-Eu³⁺ complex. The experimental conditions were optimized. The CL intensity was linearly related to atenolol concentration in the range from 8.0 × 10⁻⁹ to 1.0 × 10⁻⁵ g mL⁻¹. The detection limit (3s _b) was 3 × 10⁻⁹ g mL⁻¹ and the relative standard deviation for 1.0 × 10⁻⁷ g mL⁻¹ atenolol solution was 2.4% (n = 11). The method has high sensitivity, wide linear range, inexpensive instrumentation, and has been applied to the determination of atenolol in spiked human urine and plasma samples with recoveries within the range 95.5–104.0%. Supplementary material to this paper is available in electronic form at Electronic supplementary material: Discussion of the reaction mechanism and additional figures are available online as electronic supplementary material (ESM) at . Correspondence: Jianxiu Du, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi’an 710062, P.R. China     

Automated Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry Determination of N-methyl-2-pyrrolidone and its Metabolites in Urine and Plasma

A method for the simultaneous determination of N-methyl-2-pyrrolidone (NMP) and its metabolites 5-hydroxyl-N-pyrrolidone (5HNMP), N-methylsuccinimide (MSI) and 2-hydroxy-N-methylsuccinimide (2HMSI) in plasma and urine has been developed. Samples were purified by SPE using an ASPEC XL4. Analysis was performed using LC–MS equipped with an APCI interface. The analysis provided linear responses in the range of 0.125–12 μg mL⁻¹ for all of the analytes and up to 150 μg mL⁻¹ for 5HNMP and 2HMSI. The within day precision was in the range of 0.9–19.1% for plasma samples and 1.9–10.4% for urine samples whereas the between day precisions were 4.5–11.9% and 1.2–17.5%, respectively. The method was deemed to be suitable for monitoring the levels of NMP and its metabolites in the plasma and urine of occupationally exposed persons.     

High-performance liquid chromatographic assay for simultaneous determination of tramadol and its active metabolite in human plasma. Application to pharmacokinetic studies

Summary A sensitive liquid chromatographic assay for the quantitative determination of the opioid analgesic tramadol and its active metabolite is described. Fluconazole was used as internal standard. The assay involved a singletert-butyl methyl ether extraction and LC analysis with fluorescence detection. Chromatography was at 30°C pumping an isocratic mobile phase of acetonitrile-water (19∶81, v/v) containing 0.06M NaH₂PO₄ and 0.05M triethylamine, adjusted to pH 7.90, at 1 mL min⁻¹ through a reversed-phase, 250×4 mm base-stable column. The limit of quantitation of tramadol and its active metabolite was 1 ng mL⁻¹, only 0.5 mL plasma sample was required for the determination. The calibration curve was linear from 1–1000 ng mL⁻¹. Intra and inter-day precision (C.V.) did not exceed 10%. Mean recoveries of 96.38% for tramadol and 96.62% forO-demethyltramadol with CVs of 0.43% and 1.46% were obtained. Applicability of the method was demonstrated by a pharmacokinetic study on normal volunteers who received 100 mg tramadol intravenously.     

Dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the rapid and sensitive determination of UV filters in environmental water samples

The performance of the dispersive liquid–liquid microextraction (DLLME) technique for the determination of eight UV filters and a structurally related personal care species, benzyl salicylate (BzS), in environmental water samples is evaluated. After extraction, analytes were determined by gas chromatography combined with mass spectrometry detection (GC-MS). Parameters potentially affecting the performance of the sample preparation method (sample pH, ionic strength, type and volume of dispersant and extractant solvents) were systematically investigated using both multi- and univariant optimization strategies. Under final working conditions, analytes were extracted from 10 mL water samples by addition of 1 mL of acetone (dispersant) containing 60 μL of chlorobenzene (extractant), without modifying either the pH or the ionic strength of the sample. Limits of quantification (LOQs) between 2 and 14 ng L⁻¹, inter-day variability (evaluated with relative standard deviations, RSDs) from 9% to 14% and good linearity up to concentrations of 10,000 ng L⁻¹ were obtained. Moreover, the efficiency of the extraction was scarcely affected by the type of water sample. With the only exception of 2-ethylhexyl-p-dimethylaminobenzoate (EHPABA), compounds were found in environmental water samples at concentrations between 6 ± 1 ng L⁻¹ and 26 ± 2 ng mL⁻¹.     

Development of a cloud point extraction and preconcentration method for silver prior to flame atomic absorption spectrometry

The possibility was investigated of using 2-mercaptobenzothiazole (MBT) for Ag(I) concentration by micellar extraction at cloud point (CP) temperature and subsequent determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Ag(I) with 2-mercaptobenzothiazole (MBT) in the presence of non-ionic micelles of Triton X-114. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. Under the optimum conditions, the preconcentration of 10 mL of water sample in the presence of 0.1% Triton X-114 and 2 × 10⁻⁴ mol L⁻¹ 2-mercaptobenzothiazole permitted the detection of 2.2 ng mL⁻¹ silver. The calibration graph was linear in the range of 10–200 ng mL⁻¹, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Ag(I) in water samples.     

HPLC Determination of DCJW in Rat Plasma and Its Application to Pharmacokinetics Studies

A high-performance liquid chromatography–UV method for determining DCJW concentration in rat plasma was developed. The method described was applied to a pharmacokinetics study of intramuscular injection in rats. The plasma samples were deproteinized with acetonitrile in a one-step extraction. The HPLC assay was carried out using a VP-ODS column and the mobile phase consisting of acetonitrile–water (80:20, v/v) was used at a flow rate of 1.0 mL min⁻¹ for the effective eluting DCJW. The detection of the analyte peak area was achieved by setting a UV detector at 314 nm with no interfering plasma peak. The method was fully validated with the following validation parameters: linearity range 0.06–10 μg mL⁻¹ (r > 0.999); absolute recoveries of DCJW were 97.44–103.46% from rat plasma; limit of quantification, 0.06 μg mL⁻¹ and limit of detection, 0.02 μg mL⁻¹. The method was further used to determine the concentration–time profiles of DCJW in the rat plasma following intramuscular injection of DCJW solution at a dose of 1.2 mg kg⁻¹. Maximum plasma concentration (C _max) and area under the plasma concentration–time curve (AUC) for DCJW were 140.20 ng mL⁻¹ and 2405.28 ng h mL⁻¹.     

Determination of risperidone at picogram level in human urine by luminol—H2O2 chemiluminescence

A simple flow-injection chemiluminescence method with synergistic enhancement has been investigated for the rapid and sensitive determination of antipsychotic risperidone. The synergistic action was significant in the chemiluminescence system of luminol—hydrogen peroxide with risperidone as an enhancer. The increased chemiluminescence intensity was correlated with risperidone concentration within the range from 10 pg mL⁻¹ to 1.0 ng mL⁻¹ with relative standard deviations lower than 5.0 % and the detection limit of 4 pg mL⁻¹. At a flow rate of 2.0 mL min⁻¹, the flow-injection chemiluminescence method exhibited both a high sensitivity and excellent selectivity giving a throughput of 120 times per hour. The proposed method was successfully applied to determine the risperidone content in human urine without any pretreatment. It was found that the excretive amounts of risperidone reached their maximum after taking 2.0 mg of risperidone for 1 h, with a total excretive ratio of 17.37 % in 8.5 h.     

Enantioselectivity of 6-O-alkyldimethylsilyl-2,3-di-O-methyl-β-cyclodextrins as chiral stationary phases in capillary GC

Summary Clenbuterol has been determined in urine by solidphase extraction on a C₁₈ cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and separation of the azo dye formed by HPLC with a C₁₈ column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M NaOH before extraction. Limits of detection of 51 and 6.7 ng L⁻¹ were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities were 3.1% (5 μg mL⁻¹) and 5.6% (0.16 μg mL⁻¹).     

A sensitive liquid chromatographic-mass spectrometric method for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma

A liquid chromatographic–mass spectrometric (LC–MS) method has been developed and validated for simultaneous determination of dehydroevodiamine and limonin from Evodia rutaecarpa in rat plasma. After addition of the internal standard, domperidone, plasma samples were extracted by liquid–liquid extraction with ethyl acetate and separated on an Apollo C₁₈ column (250 mm × 4.6 mm, 5 μm), with methanol–0.01% formic acid water (60:40, v/v) as mobile phase, within a runtime of 12.0 min. The analytes were detected without interference in the selected ion monitoring (SIM) mode with positive electrospray ionization. The linear range was 1.0–500 ng mL⁻¹ for dehydroevodiamine and 2.0–1,000 ng mL⁻¹ for limonin, with lower limits of quantitation of 1.0 and 2.0 ng mL⁻¹, respectively. Intra-day and inter-day precision were within 6.0% and 10.9%, respectively, for both analytes, and the accuracy (relative error, RE, %) was less than 4.8% and 6.5%, respectively. The validated method was successfully applied to a comparative pharmacokinetic study of dehydroevodiamine and limonin in rat plasma after oral administration of dehydroevodiamine, limonin, and an aqueous extract of Evodiae fructus. The results indicated there were obvious differences between the pharmacokinetic behavior after oral administration of an aqueous extract of Evodiae fructus compared with single substances.     

Fast and selective extraction of nicotine from human plasma based on magnetic strong cation exchange resin followed by liquid chromatography-tandem mass spectrometry

In the study, a fast and selective method based on magnetic separation has been developed for the extraction of nicotine from human plasma using magnetic strong cation exchange (MSCX) resins as adsorbent. MSCX resins were prepared using hydrophobic Fe₃O₄ magnetite as magnetically susceptible component, styrene and acrylic acid as polymeric matrix components, and acetyl sulfonate as the sulfonation agent. The extraction procedure was carried out in a single step by stirring the mixture of diluted plasma sample and MSCX resins in the vortex for 5 min. Then, the resins with adsorbed nicotine were separated from the sample matrix by applying an appropriate magnetic field. Main factors affecting the extraction of nicotine such as the amount of MSCX resins, pH value of the extraction solvent, extraction time, and washing and eluting conditions were optimized. The nicotine eluted from the resins was determined by liquid chromatography–tandem mass spectrometry. The calibration curve obtained by analyzing matrix-matched standards shows excellent linear relationship (r ² = 0.9998) in the concentration range of 10–2,500 ng mL⁻¹. The limit of detection and quantification obtained are 2.9 and 9.7 ng mL⁻¹, respectively. The relative standard deviations of intra- and inter-day obtained are in the range of 1.9–6.9% and 2.5–7.8% with the recoveries ranging from 78.7% to 99.1%. The proposed method was successfully applied to determine nicotine in human plasma phlebotomized from ten male smokers. Nicotine was detectable with the contents ranging from 44.4 to 221.9 ng mL⁻¹ in five samples.     

Application of molecularly imprinted polymer solid-phase extraction for salivary cotinine

A method constituted by molecularly imprinted solid-phase extraction (MISPE) with high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) was developed for cotinine analysis in saliva samples. For this purpose, the separation was carried out with a C18 reversed-phase column at 20 °C. The mobile phase which was composed of a mixture of 09:91 (v/v) acetonitrile/phosphate buffer, pH 6.3, was delivered with isocratic flow rate at 1.4 mL min⁻¹. Employing MISPE, the best conditions were achieved with 1.5 mL of saliva plus 1.5 mL of 0.1 mol L⁻¹ of acetate buffer, pH 5.5, which were then passed through a cartridge previously conditioned with 2 mL acetonitrile, 2 mL methanol, and 2 mL of 0.1 mol L⁻¹ sodium acetate buffer, pH 5.5. The washing was carried out with 1 mL deionized water, 1 mL of 0.1 mol L⁻¹ sodium hydroxide, and 1 mL hexane; finally; the cotinine elution was carried out with 3 mL methanol/water (97.5: 2.5, v/v). Linearity ranged from 30 to 500 ng mL⁻¹ with r > 0.99. Intra-assay, interassay precision, and accuracy ranged from 3.1% to 10.1%, 5.2% to 15.9%, and 99.22% to 111.17%, respectively. The detection and quantification limits were 10 and 30 ng mL⁻¹, respectively. This investigation has provided a reliable method for routine cotinine determination in saliva, and it is an important tool for monitoring cigarette smoke exposure in smokers. The method was applied in five smokers’ samples who consumed around five to 20 cigarettes per day and the values of cotinine in saliva were from 66.7 to 316.16 ng mL⁻¹.     

LC Determination of 4-Bromoaniline in Green Algae Chlamydomonas reinhardtii After Continuous-Flow Microextraction

In this study, the determination of 4-Bromoaniline (4-BA) in green algae Chlamydomonas reinhardtii (C. reinhardtii) was investigated by applying continuous-flow microextraction (CFME) combined with high-performance liquid chromatography (HPLC). Continuous-flow microextraction was conducted in a homemade glass chamber, i.e. the sample solution flowed through a constant volume drop of solvent in the chamber at a constant flow rate. The effects of different factors on extraction efficiencies were also investigated and these factors included the kind of extraction solvent, solvent drop volume, sample flow rate, extraction time and addition amount of salt. Under the optimum extraction conditions (extraction solvent, carbon tetrachloride; solvent drop volume, 3.5 μL; sample flow rate, 1.0 mL min⁻¹; extraction time, 10 min; no addition of salt), the calibration plot was set up by plotting peak area against a series of 4-Bromoaniline concentrations (0.01–10 μg mL⁻¹) in aqueous solution. The correlation coefficient (r) was 0.9990. The limit of detection (LOD) was 0.6 ng mL⁻¹. The precision of this method was obtained by successive five time analyses of 100-ng mL⁻¹ standard solution of 4-Bromoaniline, and the relative standard deviation (RSD) was 3.5%. The concentration factor was calculated by the ratio of peak area of the analyte obtained after and before extraction and found to be 10.6. 4-Bromoaniline residues in Chlamydomonas. reinhardtii cells and tap water samples were satisfactorily analyzed according to the method described above.     

Combined use of carbon nanotubes and ionic liquid to improve the determination of antidepressants in urine samples by liquid chromatography

Antidepressants are widely used for the treatment of psychiatric disorders and therefore their monitoring in biological fluids is quite important taking into account that they can produce dangerous biochemical imbalances in toxic doses. A method for the determination of antidepressants in urine samples is presented using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Home-made cartridges containing 30 mg multiwall carbon nanotubes are employed for isolation of the analytes from the sample, allowing also the preconcentration of the analytes prior to the HPLC analysis. Chromatographic separation was achieved in a reversed-phase C₈ column using the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate as silanol activity suppressor, which enhances peak symmetry and chromatographic resolution. Limits of detection were 12.3 ng mL⁻¹ for trazodone and 90.1 ng mL⁻¹ for fluoxetine. The repeatability of the proposed method expressed as RSD (n = 11) varied between 3.4% (fluoxetine) and 5.0% (desipramine and mianserine). Thus, the method is suitable for the therapeutic monitoring of antidepressants in urine samples.