Non-Aqueous CE Screening Method for 14 Psychotropic Drugs in Whole Blood Samples

Nine tricyclic antidepressants and six phenothiazines were studied together using non-aqueous capillary electrophoresis. The optimum separation conditions were examined by changing such factors as: quantitative composition of the background electrolyte, the salt cation present in the electrolyte and the medium used for dissolution of samples. A number of drugs were also tested as the internal standards for qualitative analysis. The optimum experimental conditions were applied to the identification of the psychotropic drugs spiked to whole blood samples. The repeatability of the identification parameter, ranged from 0.58 to 10.24% RSD calculated in relation to noxiptyline. The evaluated detection limit was 0.15 μg mL⁻¹ for ten drugs and 0.08 μg mL⁻¹ for four drugs.     

Fast CE Determination of d-Amphetamine and Diphenhydramine in Quick-Acting Anti-Motion Capsules

The quick separation and simultaneous determination of d-amphetamine and diphenhydramine in the quick-acting anti-motion capsules was investigated by capillary zone electrophoresis. The influence of different parameters (internal standard, injection modes, pH, concentration of the running buffer and applied voltage) was systematically studied. The two compounds could be well separated within 2.0 min in a 40.2 cm fused-silica capillary at a separation voltage of 20 kV in a 50 mM phosphate–12.5 mM borate buffer adjusted to pH 5.5. Correlation coefficients for calibration curves in the range 0.50–1.50 μg mL⁻¹ for d-amphetamine and 2.75–8.25 μg mL⁻¹ for diphenhydramine were higher than 0.999. The limits of detection of d-amphetamine and diphenhydramine were 10.0 and 5.5 ng mL⁻¹ and the recoveries of the compounds in the QAAMC were 99.80 and 99.85%, respectively. The authors L. Zhang and Y. Chen equally contributed to this work.     

Simple and rapid determination of piperacillin and ceftazidime in human plasma samples by HPLC

Summary A simple and rapid liquid chromatographic method has been developed for the determination of therapeutic levels of piperacillin (I) and ceftazidime (II) in human plasma. Plasma and p-propionamidophenol (internal standard) were precipitated with methanol (I) or 20% trichloroacetic acid (II). The supernatant was analysed on a 5 μm Spherisorb ODS C₁₈ column with acetonitrile-0.05 M phosphate buffer pH 3.8 as mobile phase and ultraviolet detection at 254 nm. The calibration graph was linear from 10 to 250 μg mL⁻¹, for (I), and from 5 to 200 μg mL⁻¹ for (II). Intra and inter-day CV did no exceed 2.29% for (I), and were 10.76–11.13%–2.00–5.62 for (II) at concentrations of 10 μg mL⁻¹ and 250 μg mL⁻¹.     

Simultaneous Determination of Lidocaine, Proline and Lomefloxacin in Human Urine by CE with Electrochemiluminescence Detection

A new method was developed for the simultaneous determination of lidocaine, proline and lomefloxacin in human urine by capillary electrophoresis-electrochemiluminescence detection with Ru(bpy)₃ ²⁺. Conditions of the separation and detection were investigated and optimized. It was proved that 20 mM phosphate buffer at pH 6.7 could achieve the most favorable resolution, and the high sensitivity of detection was obtained by using the detection potential at 1.15 V and 5 mM Ru(bpy)₃ ²⁺–60 mM phosphate buffer at pH 7.6 in the detection reservoir. The detection limits were 0.02 μg mL⁻¹ for lidocaine, 0.03 μg mL⁻¹ for proline and 0.06 μg mL⁻¹ for lomefloxacin. Relative standard deviations of the ECL intensity and the migration time were 3.5 and 1.1% for 6 μg mL⁻¹ lidocaine, 3.2 and 1.0% for 6 μg mL⁻¹ proline and 3.7 and 1.2% for 6 μg mL⁻¹ lomefloxacin, respectively. A baseline separation for lidocaine, proline and lomefloxacin was achieved within 360 s. The developed method was successfully applied to determine the amounts of lidocaine, proline and lomefloxacin in human urine. The recovery and RSD were in the range of 93.3–97.2 and 3.8–4.9%, respectively.     

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).     

Highly Sensitive and Selective Detection of Creatinine by Combined Use of MISPE and a Complementary MIP-Sensor

Guanidinoacetate methyltransferase deficiency is a recently discovered inborn defect of creatine biosynthesis which reduces serum creatinine concentrations to as low as 0.58 μg mL⁻¹ (or 0.00058 μg mL⁻¹ after 1,000-fold dilution). To measure ultra trace levels of creatinine in diluted samples, molecularly imprinted solid-phase extraction (MISPE) and molecularly imprinted polymer (MIP) sensor techniques have been found to be inadequate. A combination of these techniques (i.e. MISPE hyphenated with use of an MIP-sensor), reported in this paper, has been found to be highly suitable for direct assay of creatinine in highly diluted human blood serum without complicated pretreatment of the sample. The proposed technique has the potential to enhance the sensitivity of creatinine measurement from μg mL⁻¹ to ng mL⁻¹ in highly dilute aqueous samples in which the concentrations of interfering constituents are reduced to negligible levels. In this work the sensitivity to creatinine was found to be improved compared with that of the MIP-sensor method alone (limit of detection, LOD, 0.00149 μg mL⁻¹). After preconcentration by MISPE and use of the sensor the detection limit for creatinine was as low as 0.00003 μg mL⁻¹ (RSD = 0.94%, S/N = 3; 50-fold preconcentration factor) in aqueous samples.     

Determination of phenazopyridine in human plasma by high performance liquid chromatography

Summary A simple, low-cost, sensitive and selective HPLC method was developed for the determination of phenazopyridine in human plasma. The method employs UV detection of phenazopyridine and of the internal Standard at 2 different wavelengths. Calibration curves were linear over a large dynamic range, i.e., within 0.05–10.0 μg mL⁻¹ with limit of quantification of 0.05 μg mL⁻¹, and a limit of detection of 0.01 μg mL⁻¹.     

MEKC Determination and Pharmacokinetic Study of Danshensu in Rabbits after Intragastric Administration of the Aqueous Extract from Danshen

A micelle eletrokinetic capillary chromatography (MEKC) method was used to determine Danshensu in rabbit blood plasma and tissues (liver, lung, kidney, brain, heart and spleen). The separation was achieved with a buffer consisting of 30 mmol L⁻¹ borax and 50 mmol L⁻¹ SDS (pH 9.0), and with an applied voltage of 7.0 kV. Validation of the method showed good sensitivity, reproducibility and precision. The calibration curve for Danshensu was linear over the concentration range of 0.4–400 μg mL⁻¹. The limit of detection (LOD) was 0.08 μg mL⁻¹ (S/N = 3). The validated method has been successfully applied for the pharmacokinetic and the tissue distribution studies of Danshensu after intragastric administration of the aqueous extract from traditional Chinese medicine Danshen.     

HPLC Determination of Lovastatin in Rat Tissue

A simple HPLC method has been developed and validated for the determination of lovastatin in rat tissues. Samples were prepared by a simple protein precipitation. Separation was carried out on a C18 column with a mobile phase of acetonitrile:0.05 M ammonium acetate, a flow rate of 1.0 mL min⁻¹ and with detection at 238 nm. There was no interference from endogenous tissue compounds. The calibration curve was linear from 0.0175 to 7.0 μg mL⁻¹ with a limit of detection of 0.006 μg mL⁻¹. The method was used to measure the concentration of lovastatin in rat tissue after a single oral dose. The highest level was observed in the liver, then in kidney, heart and spleen; the lowest level was found in the brain. These results suggest that lovastatin distributes rapidly into all tissues and particularly the liver.     

Separation and simultaneous determination of quinolone antibiotics by capillary zone electrophoresis

Summary The potential of capillary zone electrophoresis has been investigated for the separation and quantitative determination of some quinolone antibiotics. The influence of different conditions, such as the nature and concentration of the electrophoretic electrolyte, on migration time, peak symmetry, efficiency and resolution was studied. A buffer consisting of 100mm HEPES adjusted to pH 8.5 containing 10% (v/v) acetonitrile was found to furnish a very efficient and stable electrophoretic system for the separation of exoxacin, ciprofloxacin, ofloxacin, oxolinic acid, nalidixic acid and pipemedic acid. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.25–40 μg mL⁻¹; detection limits were approximately 0.25 ng mL⁻¹. It was demonstrated that the method can be used for the simultaneous determination of these six antibiotics in serum and urine samples.     

Simultaneous determination of twelve water- and fat-soluble vitamins by high-performance liquid chromatography with diode array detection

Summary A novel method for the simultaneous determination of twelve water- and fat-soluble vitamins has been established by high-performance liquid chromatography with diode array detection. The vitamins were analyzed on a μBondapak C₁₈ column (300 × 3.9 mm, 10 μm) with methanol-KH₂PO₄ buffer (0.1 M, pH 7.0)-water as mobile phase in a gradient. The linearity of calibration graphs was compound-dependent and the detection limits ranged from 0.02 μg mL⁻¹ to 0.5 μg mL⁻¹. The method was successfully applied to determine vitamins in pharmaceutical preparations. The recoveries were from 95.1% to 103% and the relative standard deviations were in the range of 0.9% to 4.5%.     

Simultaneous separation and determination of Cu(II), Fe(III), and Pb(II) by reversed-phase ion-pair chromatography withN,N,N′, N′-ethylene-diaminetetrakis(methylenephosphonic Acid)

Summary A reversed-phase ion-pair chromatographic (RPIPC) method withN,N,N′, N′-ethylenediaminetetrakis(methylenephosphonic acid) (EDTMP) as coordinating agent has been developed for simultaneous separation and detection of Cu(II), Fe(III), and Pb(II) ions. Response is linearly dependent on amount of sample over the range 9.52–50.8 μg mL⁻¹ for Cu(II), 8.31–41.8 μg mL⁻¹ for Fe(III), and 37.3–51.8 μg mL⁻¹ for Pb(II). The method has been applied successfully to an artificial mixed-ore sample.     

Determination of azelaic and sorbic acid in pharmaceduticals by capillary electrophoresis

Summary Capillary electrophoresis with indirect UV detection at 254 nm was applied to simultaneous determination of ∼20% of azelaic acid and ∼0.1% of sorbic acid in AKNOREN cream. The acids were separated in fused silica capillary (45 cm × 50 μm) at 30 kV. Optimised back-ground electrolyte was 30 mM benzoate buffer (pH∼6, adjusted with TRIS) containing 7 mM β-cyclodextrin and 5% of methanol; internal standard was 2-hydroxysobutyric acid (HIBA). Rectilinear calibration ranges were 0.4–4 mg mL⁻¹ for azelaic acid and 2–20 μg mL⁻¹ for sorbic acid and the recoveries were 97.2–100.5%. A single analysis took <15 min.     

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.     

Automated high-performance liquid chromatographic determination of amphetamine in biological fluids using column-switching and on-column derivatization

Summary A rapid and simple liquid-chromatographic method has been developed for on-line quantification of amphetamine in biological fluids. Untreated samples (20 μL) are injected directly into the chromatographic system and purified on a 20 mm×2.1 mm i.d. pre-column packed with 30 μm Hypersil C₁₈ stationary phase. After clean-up the analyte is transferred to the analytical column (125 mm×4 mm i.d., 5 μm LiChrospher 100 RP₁₈) for derivatization and separation using a mixture of acetonitrile and the derivatization reagent (o-phthaldialdehyde andN-acetyl-L-cysteine) as the mobile phase. The experimental conditions for on-line derivatization and resolution of the amphetamine have been optimized, and the results have been compared with those obtained by derivatizing the analyte in pre-column mode. The method described has been applied to the determination of amphetamine in plasma and urine. Good linearity and reproducibility were obtained in the 0.1–10.0 μg mL⁻¹ concentration range, and limits of detection were 25 ng mL⁻¹ and 10 ng mL⁻¹ with UV and fluorescence detection, respectively. The procedure described is very simple and rapid, because no off-line manipulation of the sample is required; the total analysis time is approximately 8 min.     

Fluorescence enhancement of the protein–curcumin–sodium dodecyl benzene sulfonate system and protein determination

Protein can greatly enhance the fluorescence of curcumin (CU) in the presence of sodium dodecyl benzene sulfonate (SDBS). Experiments indicate that under the optimum conditions, the enhanced intensity of fluorescence is proportional to the concentration of proteins in the range of 0.0050–20.0 μg mL⁻¹ for bovine serum albumin (BSA), 0.080–20.0 μg mL⁻¹ for human serum albumin (HSA), and 0.040–28.0 μg mL⁻¹ for egg albumin (EA). Their detection limits (S/N=3) are 1.4 ng mL⁻¹, 20 ng mL⁻¹, and 16 ng mL⁻¹, respectively. The method has been satisfactorily used for the determination of proteins in actual samples. In comparison with most of fluorimetric methods, this method is quick and simple, has high sensitivity and good stability. The interaction mechanism is also studied.     

Differentiation of certified brands of origins of Spanish white wines by HS-SPME-GC and chemometrics

A headspace solid-phase microextraction gas-chromatographic (HS-SPME-GC) procedure was used to determine the composition of the volatile fraction of white wine samples from several Spanish certified brands of origin (CBO). The compounds present were previously identified by gas chromatography−mass spectrometry (GC−MS) and quantitative determinations were carried out by GC-FID. Four CBO, Rueda, Ribeiro, Penedés, and Condado de Huelva, were studied. Rueda wines present the highest concentrations of ethyl acetate (55.86−125.27 μg mL⁻¹), isoamyl acetate (0.91−6.72 μg mL⁻¹), hexyl acetate (0.09−0.81 μg g mL⁻¹), and 2-phenethyl acetate (0.14−0.66 μg mL⁻¹). Compounds such as ethyl hexanoate (0.88−2.15 μg mL⁻¹) and ethyl decanoate (0.29−0.96 μg mL⁻¹) appeared in higher concentration in Ribeiro, Rueda, and Penedés samples. According to the results obtained and by applying pattern-recognition procedures differentiation of the considered CBO was attained. Principal-component analysis (PCA), linear discriminant analysis (LDA), and multilayer perceptrons neural networks (MLP-NN) were used as chemometric tools for pattern-recognition studies. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Ultrasound-assisted derivatization of phenolic compounds in spiked water samples before pervaporation, gas chromatographic separation, and flame lonization detection

Summary A fully automated method, based on continuous ultrasound-assisted derivatization coupled with pervaporation before gas chromatographic separation and flame ionization detection, has been developed for the determination of phenol and cresols in water. Spiked water samples were doped with acetic anhydride and dipotassium hydrogen phosphate, before introduction into the flow system, to achieve catalytic acetylation of the target compounds. A multivariate study was performed to optimize the main factors affecting the derivatization process. The correlation coefficients, r, of the calibration plots obtained were better than 0.999 for cresols and better than 0.99 for phenol. Detection limits were 0.02 μg mL¹ for phenol, o-cresol, andp-cresol, and 0.05 μg mL¹ form-cresol. Reproducibility and repeatability, expressed as relative standard deviation, ranged from 2.0–3.9% and from 1.0–3.5% respectively.     

Simultaneous determination, by capillary zone electrophoresis, of multiple components of different industrial products

Summary Four parabens (esters of 4-hydroxybenzoic acid), effective preservatives against the growth of bacteria, yeast, and mold in numerous industrial products, have been used in this work as model compounds to demonstrate the resolving power of capillary electrophoresis (CE). The simultaneous determination of methyl-(MP), ethyl-(EP), propyl-(PP), and butylparaben (BP) was achieved by capillary zone electrophoresis (CZE) with UV diode-array detection at 294 nm. When run voltage, temperature, and electrolyte concentration and pH were optimized the most effective separation was achieved within 7 min by use of 50 cm (effective length) fused silica capillary tubing and operation at 25kV and 20°C. Background electrolyte comprising 35 mM tetraborate buffer adjusted to pH 10.0 gave the best results. The limits of detection of the optimized method ranged from 0.65 μg mL⁻¹ for BP to 0.81 μg mL⁻¹ for MP; the relative standard deviation was between 0.35 and 0.50%. These results showed that the method enables the determination of the four parabens in commerially available cosmetic and pharmaceutical preparations containing some of the parabens and in an unidentified canned berry fruit juice.     

Separation ofN-carbamoyl aspartate andl-dihydroorotate from serum by high-performance liquid chromatography with fluorimetric detection

Summary A high-performance liquid chromatographic method, with 9-anthryldiazomethane as derivatizing agent, has been developed for the simultaneous determination ofN-carbamoyl aspartate andl-dihydroorotate in serum. Sample preparation for 1 mL serum was by simple liquid-liquid extraction and then derivatization. The compounds were separated on a Luna C18(2) column by use of a gradient prepared from acetonitrile and 10 mM sodium acetate buffer, pH 6.0, and fluorimetric detection was performed at excitation and emission wavelengths of 365 nm and 412 nm, respectively. The response was found to be linearly dependent on concentration between 0.8 and 60 μg mL⁻¹ forl-dihydrooratate and between 0.9 and 90 μg mL⁻¹ forN-carbamoyl aspartate; the mean recovery rates were 50 and 51%, respectively. The limits of detection and quantification were 0.33 μg mL⁻¹ and 0.6 μg mL⁻¹, respectively, forl-dihydroorotate and 0.4 μg mL⁻¹ and 0.7 μg mL⁻¹ forN-carbamoyl aspartate. This method can be used to assess accumulation ofN-carbamoyl aspartate andl-dihydroorotate in body fluids in situations where cellular pyrimidine de novo synthesis is impaired.