A high performance liquid chromatography – inductively coupled plasma-mass spectrometry interface employing desolvation for speciation studies of platinum in chemotherapy drugs

A novel interface between high performance liquid chromatography (HPLC) and inductively coupled plasma-mass spectrometry (ICP-MS) is described. The eluent from the HPLC is nebulised into a heated cyclone spray-chamber and the solvent removed using a Nafion membrane drier, held at 75 degrees C, and a cryogenic condenser. The condenser consists of 6 Peltier heat pumps connected to liquid cooled aluminium blocks. At a nebuliser gas flow rate of 0.6 l min(-1), the membrane drier removes 58% of the vapour and the Peltier condenser 75% of the remaining vapour, i.e. a total desolvation efficiency of 89%. This enables the use of HPLC solvents which otherwise would destabilise the ICP, e.g. 100% acetonitrile or methanol, and permits the use of solvent gradients with minimal baseline drift. The system has been applied to the determination of platinum species in an organoplatinum drug used for chemotherapy in human plasma ultrafiltrate of patients treated with this new drug (JM-216). The limit of detection for platinum species has been 0.6 ng nl(-1) (i.e. 120 pg of Pt) and several species have been separated with good resolution.     

Pre-column derivatization of rofecoxib for determination in serum by HPLC

An HPLC method for determination of rofecoxib in human serum is presented. The method is based on pre-column derivatization of analyte to a phenanthrene derivative of the drug. Rofecoxib and the internal standard were extracted from serum using liquid–liquid extraction. Upon exposure to UV light, the drug was found to undergo a photocyclization reaction, giving a species with high absorbance. Validation of the method has been studied in the concentration range 10–500 ng ml^–1.     

Synthesis of195mPt radiolabeled cisdiammine (glycolato) platinum (II) of high radionuclidic purity

An experimental method is described for the synthesis of^195mPt-radiolabeled cis-diammine (glycolato) platinum (II) (254-S). Ten mg of 95% enriched¹⁹⁴Pt was irradiated for 75 h in the hydraulic conveyer of KUR at a thermal neutron flux of ca. 8.15×10¹³ n·cm^–2·s^–1, and the^195mPt-radiolabeled 254-S was synthesized and purified using HPLC (column: Dichrosorb Diol, elution: 80% CH₃CN). The chemical yield was approximately 45%, with chemical purity greater than 98.4%. The radionuclidic purity was nearly 100% and the specific activity, 7.2 MBq·mg^–1 254-S.     

An electromembrane extraction–HPLC‐UV analysis for the determination of valproic acid in human plasma

In this study, an electromembrane extraction (EME) method combined with a simple HPLC‐UV analysis was developed and validated for the determination of valproic acid in human plasma samples. The major parameters influencing EME procedure, namely the solvent composition, voltage, pH of acceptor and donor solutions, salt effect, and time of extraction, were evaluated and optimized. The drug was extracted from the donor aqueous sample solution (pH 5) to the acceptor aqueous solution (pH 13). The donor and acceptor phases were separated by a hollow fiber dipped in 1‐octanol as a supported liquid membrane. A voltage of 60 V during 25 min was applied as the driving force. The drug concentration enrichment factor obtained was >125, which enhanced the sensitivity of the method. The limit of detection and the limit of quantitation were 0.2 and 0.5 μg/mL, respectively. The proposed method was successfully applied to a human plasma sample, with a relative recovery of 75%. The method was linear over the range 0.5–10 μg/mL for valproic acid (R² > 0.9996) with a repeatability (%RSD) between 0.9 and 3.3% (n = 3). Valproic acid is an anticonvulsant drug with poor UV absorption, and EME can improve the sensitivity of HPLC‐UV for the determination of valproic acid in plasma samples.     

Separation and determination of xanthates in mixtures as dixanthogens by normal-phase HPLC on a diol-phase

Summary A normal-phase-HPLC method for determining individual xanthates in mixtures is presented. The quantitative analyses have been carried out after separation on a LiChrosorb-Diol column using the non-polar solvent n-hexane as mobile phase and UV-detection at 254 nm. The developed HPLC procedure possesses a high sensitivity and high speed of analysis, especially for xanthates with longer alkyl chains. This method was applied to the determination of xanthates in technical flotation liquors. Relative standard deviations for contents of 0.6×10^–5 mol/l to 1.2×10^–5 mol/l were 2.76 to 5.45%. The absolute limit of determination for potassium octyl xanthate is 0.2 ng.     

Supported liquid membrane work-up in combination with liquid chromatography and electrochemical detection for the determination of chlorinated phenols in natural water samples

Summary A sample preparation method has been developed for the determination of chlorinated phenols in water. The method is based on a supported liquid membrane extraction system connected on-line to liquid chromatography with electrochemical detection. The supported liquid membrane technique utilizes a porous PTFE membrane. The membrane is impregnated with an organic solvent which forms a barrier between two aqueous phases and enables selective extraction. The technique can easily be coupled in a flow system. In this investigation five chlorinated phenols (1–5 chlorine atoms) were extracted from natural water samples. Extraction for 30 minutes resulted in detection limits of approximately 25 ng L^–1.     

Liquid chromatographic determination of cis-platin as platinum(II) in pharmaceutical preparation, serum and urine samples of cancer patients

Spectrophotometric and high performance liquid chromatographic (HPLC) methods have been developed for the determination of cis-platin and carboplatin based on the pre-column derivatization of platinum(II) with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone. The complex was extracted in chloroform with molar absorptivity of 2.2 × 10⁴ L mol⁻¹ cm⁻¹ at 380 nm. The complex eluted from a Phenomenex C-18 (150 mm × 4.6 mm i.d.) column with methanol:water:acetonitrile:tetrabutyl ammonium bromide (1 mM) (44:30:25:1, v/v/v/v) with a flow rate of 1 ml/min and UV detection at 260 nm. Ruthenium(IV) and selenium(IV) also separated completely. The linear calibration curve was with 0.5-12.5 μg/ml and detection limit of 10 ng/ml platinum(II).The analysis of cis-platin and carboplatin injections by spectrophotometric and HPLC methods indicated relative standard deviation (R.S.D.) of 0.66-2.1%. The method was used for the determinations of cis-platin in serum and urine of cancer patients after chemotherapy and platinum contents were found 148-444 and 50-90 ng/ml with R.S.D. of 0.3-3.0 and 0.6-2.4% for the serum and urine, respectively. The recovery of platinum(II) from serum was 97% with R.S.D. 2.2%.     

Sorption–Chromatographic Determination of Aniline, 4-Chloroaniline, and 2,5-Dichloroaniline in Air

Conditions were found for the chemisorption preconcentration of aniline, 4-chloroaniline, and 2,5-dichloroaniline from air using tubes packed with silica gel with immobilized 4-chloro-5,7-dinitrobenzofurazan and for the subsequent HPLC determination with diode-array detection. The maximum analyte recoveries (98, 90, and 75% for aniline, 4-chloroaniline, and 2,5-dichloroaniline, respectively) were achieved at a 2-cm thickness of the adsorbent layer (silica gel with a grain size of 0.1–0.3 mm impregnated with 3 wt % 4-chloro-5,7-dinitrobenzofurazan), an aspiration rate of 0.6–0.8 L/min, and an aspirated air volume of 10 L. Taking into account a tenfold preconcentration of analytes after the desorption, the detection limit for aniline is equal to 0.0007 mg/m³.     

Electrochemical vapor generation of selenium species after online photolysis and reduction by UV-irradiation under nano TiO<Subscript>2</Subscript> photocatalysis and its application to selenium speciation by HPLC coupled with atomic fluorescence spectrometry

An online UV photolysis and UV/TiO₂ photocatalysis reduction device (UV–UV/TiO₂ PCRD) and an electrochemical vapor generation (ECVG) cell have been used for the first time as an interface between high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS) for selenium speciation. The newly designed ECVG cell of approximately 115 L dead volume consists of a carbon fiber cathode and a platinum loop anode; the atomic hydrogen generated on the cathode was used to reduce selenium to vapor species for AFS determination. The noise was greatly reduced compared with that obtained by use of the UV–UV/TiO₂ PCRD–KBH₄–acid interface. The detection limits obtained for seleno-DL-cystine (SeCys), selenite (Se^IV), seleno-DL-methionine (SeMet), and selenate (Se^VI) were 2.1, 2.9, 4.3, and 3.5 ng mL^–1, respectively. The proposed method was successfully applied to the speciation of selenium in water-soluble extracts of garlic shoots cultured with different selenium species. The results obtained suggested that UV–UV/TiO₂ PCRD–ECVG should be an effective interface between HPLC and AFS for the speciation of elements amenable to vapor generation, and is superior to methods involving KBH₄.     

Speciation analysis of bromine-containing drug metabolites in feces samples from a human in vivo study by means of HPLC/ICP-MS combined with on-line isotope dilution

The aim of this work was speciation analysis of metabolites in feces samples collected within a clinical study during which a bromine-containing anti-tuberculosis drug (TMC207) was administered to patients with multi-drug resistant tuberculosis infection. Owing to slow elimination of the drug, no ¹⁴C label was used within this study. Quantification of the bromine species was accomplished using high performance liquid chromatography coupled to inductively coupled plasma–mass spectrometry (HPLC/ICP-MS) in combination with on-line isotope dilution (on-line ID), while structural elucidation of the species was performed using HPLC coupled to electrospray ionization–mass spectrometry. The ICP-MS-based method developed shows a good intra- and inter-day reproducibility (relative standard deviation = 3.5%, N = 9); the limit of detection (1.5 mg TMC207 L⁻¹) is of the same order of magnitude as that for HPLC/radiodetection; the dynamic range of the method covers more than two orders of magnitude. Furthermore, the column recovery was demonstrated to be quantitative (recoveries between 90.6% and 99.5%). Based on the excellent figures of merit, the “cold” HPLC/ICP-MS approach could be deployed for the actual human in vivo metabolism study, such that exposure of the human volunteers to the ¹⁴C radiolabel was avoided.