Analysis of meloxicam by high-performance liquid chromatography with cloud-point extraction

A simple cloud-point extraction method for the determination of meloxicam in human serum was developed. Meloxicam was extracted from serum sample after adding 1 mL of 3% (v/v) Triton X-114 aqueous solution in the presence of 1M HCl and 60 mg NaCl. The meloxicam, present in the surfactant-rich phase, was enriched again with acetonitrile. Tenoxicam was used as the external standard. The separation was achieved on a C18 analytical column with a mobile phase consisting of aqueous acetic acid (1%, v/v) and acetonitrile (54:46, v/v). UV detection was performed at 360 nm. The response was linear over the range 45–2000 ng mL⁻¹ in human serum, and intra- and interday precisions of less than 15.0% were obtained. The relative error was within ±3.0%. The recoveries of meloxicam were larger than 92.0%. The method was compared with liquid–liquid extraction. The results showed that the new method has a considerable LOQ and higher recoveries but poorer precision than liquid–liquid extraction, which exhibited poor recoveries of less than 86.0%, precisions of less than 5.0% and relative errors of less than 7.0%. The method was used for the determination of meloxicam in healthy human volunteers.     

Ionic liquid as a complexation and extraction medium combined with high-performance liquid chromatography in the evaluation of chromium(VI) and chromium(III) speciation in wastewater samples

A simple method has been proposed for the determination of chromium species by high-performance liquid chromatography (HPLC) after preconcentration by the ionic liquid, 1-butyl-3-methyimidazolium hexafluorophosphate ([C₄MIM][PF₆]). The simultaneous preconcentration of Cr(VI) and Cr(III) in wastewater was achieved with ammonium pyrrolidinedithiocarbamate (APDC) as the chelating agent and the ionic liquid [C₄MIM][PF₆] as the extractant. Baseline separation of the APDC chelates of Cr(III) and Cr(VI) was realised on a RP-C18 column using a mixture of methanol–acetonitrile–water (53:14:33, v/v) as the mobile phase at a flow rate of 1.0 mL min^{− 1}. The influences of several variables on the complexation and extraction were evaluated: pH, reaction time, APDC concentration and metal ion interference. Our results showed that when the linear concentration of Cr(VI) and Cr(III) ranged from 25 to 200 μg L^{− 1}, their linear correlation coefficients were between 0.9977 and 0.9978, their recoveries ranged from 91.8% to 95.8% and their relative standard deviations (n = 3) were between 0.31% and 1.8%. Common metal ions in water did not interfere with the determination. This method is a simple, fast, accurate, highly stable and selective method and has successfully been applied to the speciation of chromium in wastewater.     

Determination of disulfoton in surface water samples by cloud-point extraction and gas chromatography

This article proposes an alternative method, using cloud-point extraction and gas chromatography, for extraction and determination of disulfoton in water samples. For cloud-point extraction, the nonionic surfactant Triton X-114 was used. Before gas chromatography, a cleanup stage for surfactant removal from the extracts was optimized. Cleanup used two columns, in series, containing silica gel and Florisil, with methanol:hexane (1?:?1) as eluent, resulting in the removal of more than 95% of the Triton X-114. Factors such as ionic strength (>0.5?mol?L^?1) and surfactant concentration (1.0% w/v) increased the extraction efficiency of the cloud-point methodology, yielding disulfoton recoveries of almost 100%. Compared with liquid–liquid extraction, the cloud-point methodology was more efficient, with a better detectability, and resulted in a significant reduction in solvent volume.     

Determination of Fe(III), Al(III), Mo(VI) and W(VI) with tetracycline by reversed-phase high-performance liquid chromatography

Tetracycline (TC) was used as a precolumn chelating reagent for reversed-phase high-performance liquid chromatographic (HPLC) separation and determination of Fe(III), Al(III), Mo(VI) and W(VI). The metal-TC chelates were separated on a Nucleosil C(18) (5 mum) column using a mobile phase of acetonitrile-water (21:79, v/v) containing citrate buffer and sodium chloride, nanogram levels of the metals could be determined by HPLC with satisfactory precision. The proposed method was applied to the simultaneous determination of Mo(VI) and W(VI) in mineral samples.     

Determination of osthole in rat plasma by high-performance liquid chromatograph using cloud-point extraction

A new straightforward method based on cloud-point extraction (CPE) was developed to determine osthole in rat plasma by reversed phase high-performance liquid chromatography with ultraviolet detection using a photodiode array detector. The non-ionic surfactant Triton X-114 was chosen as the extract solvent. Variable parameters affecting the CPE efficiency were evaluated and optimized. A Zorbax SB-C₁₈ column was used for elution separation at 25 °C with detection wavelength at 322 nm. Under the optimum conditions, the method was shown to be reproducible and reliable with intra-day precision below 7.62%, inter-day precision below 6.37%, and accuracy within ±5.02% and mean extraction recovery more than 90.4%, which were all calculated using a range of spiked samples at three concentrations of 0.5, 5.0 and 15.0 μg mL⁻¹ for osthole in plasma. The calibration curve for the analyte was linear in the range from 0.1 to 20 μg mL⁻¹ with the correlation coefficients greater than 0.9981. Limit of detection (S/N = 3) was less than 0.03 μg mL⁻¹and limit of quantification (S/N = 10) was less than 0.1 μg mL⁻¹. After strict validation, the method was successfully applied to the pharmacokinetic study of osthole in rats after oral and intravenous administration, respectively.     

Anion-exchange high-performance liquid chromatography of water-soluble chromium (VI) and chromium (III) complexes in biological materials

A high-performance anion-exchange liquid chromatograph coupled to visible-range (370 nm) and UV (280 nm) detectors and an atomic-absorption spectrometer allowed the rapid determination of CrVI and/or complexes of CrIII in rat plasma, erythrocyte lysate and liver supernatant treated with CrVI or CrIII in vitro. CrVI in the eluates was determined using both the visible-range detector and atomic-absorption spectrometer (AAS). The detection limits of CrVI in standard solutions using these methods were 2 and 5 ng (signal-to-noise ratio = 2), respectively. Separations of the biological components and of CrIII complexes were monitored by UV and AAS analyses, respectively. Time-related decreases of CrVI accompanied by increases in CrIII complexes were observed, indicating the reduction of CrVI by some of the biological components. The reduction rates were considerably higher in the liver supernatant and erythrocyte lysate than in the plasma. These results indicate that the anion-exchange high-performance liquid chromatographic system is useful for simultaneous determination of CrVI and CrIII complexes in biological materials.     

Determination of bisbenzylisoquinoline alkaloids by high-performance liquid chromatography (II)

After the earlier analysis of nine bisbenzylisoquinoline alkaloids with ion pair chromatography, seven other bisbenzylisoquinoline alkaloids were analyzed using gradient elution with an acetonitrile-phosphate buffer (pH 8.0) mixture, and UV detection. Four alkaloids were detected in the stem woods of a Lauraceous plant, Dehaasia triandra Merr. and their contents determined. LC-MS suggested that a major unknown compound in the plant was also a bisbenzylisoquinoline alkaloid.     

Determination of sulfophenylcarboxylic acids in marine samples by solid-phase extraction then high-performance liquid chromatography

An analytical method is presented for the determination of sulfophenylcarboxylic acids (SPC) produced by the biodegradation of linear alkylbenzene sulfonates (LAS) in marine samples. Isolation and concentration of the compounds was by solid-phase extraction. The different factors affecting extraction efficiency packing composition, pH, clean-up, ionic strength, and elution solvents--were studied and optimized. With the proposed method C4-C13SPC and C10-C13 LAS recoveries varied between 65% and 105%, with standard deviations between 0.1 and 5, respectively, for 100-mL samples and 100 microg L(-1) concentrations of each homolog. Detection limits within the range 0.5 g L(-1) (for C4SPC) to 1.0 g L(-1) (for C12SPC) were obtained by liquid chromatography with fluorescence detection. This method is the first to be proposed that enables the simultaneous determination of monocarboxylic SPC (C>3) and LAS homologs in marine samples by a simple, sensitive, and specific method giving high recoveries and reproducibility. SPC with from three to twelve carbon atoms in the carboxyl chain have been found in marine water samples.     

Complexes of chromium(III), manganese(II) and nickel(II) with methylhydrazinecarboxylate and 1,1-dimethylhydrazinecarboxylate ligands

Summary New complexes of chromium(III), manganese(II) and nickel(II) with methylhydrazinecarboxylate (MeCz) and of manganese(II) and nickel(II) with 1,1-dimethylhydra-zinecarboxylate (Me₂Cz) were prepared by reacting salts of the metals with CO₂-saturated solutions of the hydrazines in EtOH. The compounds [Cr(MeCz)₃]·2H₂O, Ni(MeCz)₂(H₂O)₃·MMH, Mn(MeCz)₂(H₂O)₂(MMH = monomethylhydrazine) and M(Me₂Cz)₂(H₂O)₂ (M = Mn or Ni) were investigated using d.t.a., t.g.a., electronic and i.r. spectroscopy and by magnetic susceptibility measurements.     

Role of different salts on cloud-point extraction of isoprocarb and promecarb insecticides followed by high-performance liquid chromatography

The influence of salt additive on cloud point extraction (CPE) of isoprocarb and promecarb insecticides is described. Types of salt (Na(2)CO(3), CaCl(2), MgSO(4), Na(2)SO(4), NaHCO(3) and NaCl) and concentrations were studied. The extracted target compounds were analyzed using reversed phase high-performance liquid chromatography. Among the salts studied, Na(2)CO(3) was found to be the most effective salt for salting out of both insecticides, resulting in high extraction efficiency (>95%) and high enrichment factor of up to 18 compared to extraction without preconcentration. The optimum CPE conditions were 1.5% (w/v) Triton X-114, 3.0% (w/v) Na(2)CO(3), and 20-min equilibration at 45°C. Under the selected conditions, the linear range of 0.05 to 3.0 mg/L was found for both analytes. The limits of detection for isoprocarb and promecarb were 10 and 20 μg/L, respectively. High intra-day (n = 9) and inter-day (n = 3 × 4 days) precisions with relative standard deviations <1% and <8% were obtained for retention time and peak area, respectively. The proposed method was successfully applied for the residue analysis of target compounds in beverages (i.e., fruit juice, vegetable juice and wine samples), which provided high recoveries (>80%, on average) for spiked samples at three levels (0.05, 0.10 and 0.50 mg/L).     

Determination of stability constants of U(VI), Np(VI) and Pu(VI) with chloride ions by extraction chromatography

The complex formation of U(VI), Np(VI) and Pu(VI) with chloride ions was studied in HClO₄−HCl solutions at ionic strength of 2.0 and [H⁺]=2.0M by the method of extraction chromatography using dilute HDEHP as the stationary phase.     

Monomeric dioxouranium(VI), chromium(III), cobalt(II), nickel(II) and copper(II) complexes with primary cellulose acetate (PCA)

Monomeric UO ₂ ²⁺ , Cr^III, CO^II, Ni^II and Cu^II complexes with primary cellulose acetate (PCA) have been prepared and characterized. Infrared,¹H NMR, UV/visible spectroscopy, elemental analysis, therniogravimetry, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that PCA exhibits octahedral coordination with Cr^III, Co^II, Ni^II and a square planar form with Cu^II whereas the UO₂ moiety is virtually linear. PCA acts as a neutral bidentate chelating agent via the two oxygen atoms of the vicinal ester groups in the secondary positions forming a five-membered chelate ring. A comparative study between chelates of PCA and those previously prepared with secondary cellulose acetate (SCA) has been undertaken.     

Gas chromatography of ternary complexes of manganese(II), iron(II), cobalt(II) and nickel(II) with hexafluoroacetylacetone and DI-n-butylsulphoxide

The gas Chromatographic behaviour of the ternary complexes of selected bivalent first-row transition metal ions with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione H(HFA), and di-n-butylsulphoxide, DBSO, was studied. Calibration plots of peak area vs. amount of metal injected were linear over a range of 60–900 ng for manganese(II), iron(II), cobalt(II) and nickel(II). The average relative standard deviation was less than 3·0% for all the metals studied. Detection limits of 60, 109, 112 and 115ng for cobalt(II), nickel(II), iron(II) and manganese(II), respectively, were obtained with flame-ionization detection. Various liquid phases, including OV-1, SE-30, and Dexsil 300 were used. The best results were obtained on columns of 5% Dexsil 300. No appreciable thermal decomposition was observed on stainless-steel or glass columns, but the best formed peaks were obtained on all-glass columns. The elution of the metallic species was confirmed by venting the exit gases from the gas chromatograph directly into an atomic-absorption spectrophotometer.     

Determination of trans-resveratrol in grapes by pressurised liquid extraction and fast high-performance liquid chromatography

A study has been made of the extraction of trans-resveratrol from grapes using pressurised liquids (PLE); for this, the first stage was to determine the stability of this compound during extractions at different temperatures (50, 100, 150 degrees C), with quantitative recoveries being obtained up to 150 degrees C. By employing solid-phase extraction (SPE) it was possible to retain this compound and separate it from other interfering substances present in the grape. The method developed comprises a sequential extraction of the sample adsorbed (0.5g) on a polystyrene-divinylbenzene based sorbent in the extraction chamber, first with water at 40 degrees C and 40atm of pressure (three cycles of 5min), and then with methanol at 150 degrees C and 40atm (three cycles of 5min). The trans-resveratrol content of the methanolic extract is determined by means of liquid chromatography. A rapid (5min) chromatographic method employing a monolithic column, with fluorescence detection, has been developed; for this, the conditions for detection of the compound were optimised (excitation at 310nm and emission at 403nm). The analytical parameters of the method of chromatographic analysis developed have been calculated: linear range (0.11-2.75mg/L), detection limit (0.003mg/L), quantification limit (0.004mg/L). Using this method, three varieties of grape have been analysed and the concentration of trans-resveratrol in these has been determined.     

Salting-out extraction technique for pretreatment in the liquid chromatographic determination of copper(II), aluminum(III), iron(III) and manganese(II) in biological samples

A solvent extraction method for the simultaneous determination of Cu, Al, Fe and Mn by reversed phase liquid chromatography is presented. The metal chelates with 5-chloro-8-quinolinol are extracted into an acetonitrile phase with tetrabutylammonium perchlorate and ammonium sulfate as salting-out agents, followed by LC separation and determination using an ODS column. The experimental parameters such as the composition of mobile phase and concentration of the salting-out agent for phase separation have been investigated. The mobile phase is a mixture of 3:1 (v/v) acetonitrile-0.02 mol l(-1) sodium acetate solution containing 5x10(-3) mol l(-1) 5-chloro-8-quinolinol. The proposed method has been applied to the trace analysis of Cu, Al, Fe and Al in bovine liver and citrus leaves.     

Determination of UV-absorbing anions in environmental samples by microcolumn high-performance liquid chromatography

The Chromatographic retention and separation of NO ₂ ^- , Br^-, NO ₃ ^- , and I^- anions on a column packed with Nucleosil 100-5 C18 dynamically modified with trimethyloctadecylammonium bromide (TMODAB) was studied using direct UV detection. A procedure was developed for the determination of the above anions in the concentration range 0.06-2500 Μg/L without preconcentration. Sample preparation involved only the elimination of organic impurities (if present) from the test sample. The procedure was used for the determination of NO ₂ ^- and NO ₃ ^- anions in Baikal Lake water and in an aerosol extract.     

Unusual stabilization of manganese(III) during the cooxidation of dimethylformamide and manganese(II) by chromium(VI)

The kinetics of the formation and decomposition of Mn^III have been investigated spectrophotometrically in acidic media at 25 °C. The complete rate law for Mn^III formation isCr^VI + DMF + Mn^II {H⁺} Mn^III + CO₂ + Me₂NH + Cr^III ... (1)Mn^III + DMF {H⁺} Mn^II + CO₂ + Me₂NH ... (2)expressed by k _obs1 = k ₁ k₁ K _a1[H⁺][DMFH⁺][Mn^II]/{1 + K _a1[H⁺]}. Mn^III reduction by DMF follows the rate law k _obs2 = k ₂ K _h[DMF][H⁺]²/{[H⁺] + K _h}. The above results are accounted for by a mechanism involving the intermediacy of Cr^IV.     

Complexes of 1-isonicotinoyl-4-benzoyl-3-thiosemicarbazide with manganese(II), iron(III), chromium(III), cobalt(II), nickel(II), copper(II) and zinc(II)

1-Isonicotinoyl-4-benzoyl-3-thiosemicarbazide (IBtsc) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II, Cu^II and Zn^II complexes have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis., i.r., n.m.r. and FAB mass spectral data. The room temperature e.s.r. spectra of the Cr^III, Fe^III and Cu^II complexes yield values, characteristic of octahedral, tetrahedral and square-planar complexes, respectively. The Mössbauer spectra of [Fe(IBtsc-H)Cl₂] at room temperature and at 78 K suggest the presence of high-spin Fe^III. The Ni^II, Cr^III and Cu^II complexes show semiconducting behaviour in the solid state, but the Zn^II complex is an insulator at room temperature. IBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.