Hydrophilic-lipophilic Balance Cartridges Research Articles

Determination of Cocaine and Heroin with Their Respective Metabolites in Human Hair using Gas Chromatography‐Mass Spectrometry

This paper describes a gas chromatography‐mass spectrometry method for the simultaneous detection of opiates, cocaine, and benzoylecgonine from human hair samples. Conditioning samples were extracted with Waters Oasis HLB (hydrophilic‐lipophilic balance) cartridges. The detector response was linear for the drugs studied over the range 0.5–20 ng/mg. The limits of quantitation and detection were found to be acceptable. Intra‐ and interbatch coefficients of variation oscillated between 0.2 and 17.9%, and mean relative errors were in the range of 0.04–18.2%. The recoveries were higher than 66.7% in all cases. Finally, the method was applied to 20 hair samples from drug users, obtaining positive results in all cases.

Determination of levetiracetam in human plasma by liquid chromatography/electrospray tandem mass spectrometry and its application to bioequivalence studies

The first liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the determination of levetiracetam, an antiepileptic drug, in human plasma is described. The plasma filtrate obtained after solid-phase extraction (SPE), using a polymer-based, hydrophilic-lipophilic balanced (HLB) cartridge, was submitted directly to a short column LC/MS/MS assay. There was no significant matrix effect on the analysis. For validation of the method, the recovery of the free analytes was compared to that from an optimized extraction method, and the analyte stability was examined under conditions mimicking sample storage, handling, and analytical procedures. The extraction procedure yielded extremely clean extracts with a recovery of 79.95% and 89.02% for levetiracetam and the internal standard (IS), respectively. The intra-assay and inter-assay precision for the samples at the lower limit of quantitation (LLOQ) were 6.33 and 6.82%, respectively. The calibration curves were linear for the dynamic range of 0.5 to 50 microg/mL with a correlation coefficient r >/= 0.9971. The intra-assay accuracy at LLOQ, LQC, MQC, and HQC levels ranged from 81.60 to 95.40, 93.00 to 103.47, 95.97 to 104.09, and 91.15 to 95.18%, respectively, while the inter-assay accuracy at LLOQ, LQC, MQC and HQC levels varied from 80.20 to 95.40, 88.53 to 107.53, 95.97 to 108.45, and 91.15 to 112.70%, respectively. The method is rugged and fast with a total instrumental run time of 2 min. The method was successfully applied for bioequivalence studies in human subject samples after oral administration of 1000 mg immediate release (IR) formulations.

P.1.c.029 A comparative pharmacokinetic study in healthy volunteers of the effect of carbamazepine and oxcarbazepine on CYP 3A4

A method based on high-performance liquid chromatography with UV detection in combination with solid-phase extraction for sample pretreatment has been developed for the simultaneous analysis of the antiepileptic drug oxcarbazepine and its main metabolites in human plasma. The extraction of the analytes from plasma samples was carried out by means of a selective solid-phase extraction procedure using hydrophilic–lipophilic balance cartridges. The separation was obtained on a reversed-phase column (C18, 150×4.6 mm I.D., 5 μm) using a phosphate buffer–acetonitrile–methanol–triethylamine mixture (final apparent pH* 3.5) as the mobile phase. Under these chromatographic conditions, oxcarbazepine and its metabolites 10,11-dihydro-10-hydroxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine and the internal standard are baseline separated in less than 9 min. The extraction yield values were >94% for all analytes and the precision, expressed by the RSD%, was in the low percentage range. For the entire method, including sample pre-treatment and HPLC determination, the linearity of the calibration lines, expressed by the linear correlation coefficient, was better than 0.995; the limit of quantitation was 15 ng ml−1. The method was applied to plasma samples from patients undergoing chronic treatment with oxcarbazepine, both in monotherapy and in polytherapy. Based on the analytical parameters precision, accuracy, limit of quantitation and analysis time the method is suitable for routine application in therapeutic drug monitoring.

Chemical markers of human waste contamination: Analysis of urobilin and pharmaceuticals in source waters

Giving public water authorities another tool to monitor and measure levels of human waste contamination of waters simply and rapidly would enhance public protection. Most of the methods used today detect such contamination by quantifying microbes occurring in feces in high enough densities that they can be measured easily. However, most of these microbes, for example E. coli, do not serve as specific markers for any one host species and many can have origins other than feces. As an alternative, chemicals shed in feces and urine might be used to detect human waste contamination of environmental waters. One potential chemical marker of human waste is the compound urobilin. Urobilin is one of the final by-products of hemoglobin breakdown. Urobilin is excreted in both the urine and feces from many mammals, particularly humans. Source waters from 21 sites in New England, Nevada, and Michigan were extracted using hydrophilic-lipophilic balance (HLB) cartridges and then analyzed by high performance liquid chromatography-electrospray mass spectrometry (HPLC-ES-MS). As a marker of human waste, urobilin was detected in many of the source waters at concentrations ranging from not detectable to 300 ng L(-1). Besides urobilin, azithromycin, an antibiotic widely prescribed for human use only in the US, was also detected in many of these waters, with concentrations ranging from not detectable to 77 ng L(-1). This methodology, using both urobilin and azithromycin (or any other human-use pharmaceutical) could be used to give public water authorities a definitive method for tracing the sources of human waste contamination. The analysis and detection of urobilin in surface waters by HPLC-ES-MS has not been previously reported in the peer-reviewed literature.

Liquid chromatographic method for the determination of patulin in apple juice using solid-phase extraction

Patulin is a mold metabolite commonly encountered in decaying apples. The most of analytical methods consist of multiple liquid–liquid partition steps for the extraction of patulin in apple juice. In this study, two solid-phase extraction (SPE) techniques using a tandem polyvinylpolypyrrolidone-octadecyl (PVPP-C18) cartridge system and a hydrophilic lipophilic balanced (HLB) macroporous copolymer sorbent cartridge were developed for the analysis of patulin in apple juice. A portion of apple juice was applied to either tandem PVPP-C18 cartridge system or the HLB cartridge. Patulin was eluted with diethyl ether through the cartridge excluding much of the interfering phenolic impurities. The volume of apple juice applied to the cartridges and the volume of diethyl ether to elute patulin from the cartridges were optimized to exclude much of the interfering impurities during reversed-phase (C18) liquid chromatographic separation with UV detection at 276 nm, keeping the recovery higher than 90% for spiking levels of 25–100 μg/1.

A new method for the quantitation of propofol in human plasma: efficient solid-phase extraction and liquid chromatography/APCI-triple quadrupole mass spectrometry detection

Propofol (2,6-diisopropyl phenol) is widely used for the induction and maintenance of anesthesia. Analyses of its pharmacokinetics require simple and sensitive methods for quantitation of propofol in human plasma. Previously reported HPLC and GC methods are limited by cumbersome extraction steps. We describe a novel method that combines sample preparation by solid-phase extraction (SPE) with hydrophilic–lipophilic balance cartridges and analysis with a sensitive LC-APCI-triple quadrupole mass spectrometry (MS/MS) method for better quantitation. The absolute recovery of the analyte was greater than 96%. The limit of quantification for propofol in plasma at a signal-to-noise ratio of 10 was 5 ng/ml. The precision of the assay yielded coefficients of variation ranging from 2.9 to 5.3% and an accuracies of 99–105%. Our method advances the quantitative analysis of propofol in human plasma by combining simple, rapid and efficient SPE with specific and sensitive quantitation by HPLC with APCI-MS/MS detection.

A rapid HPLC-DAD method for the analysis of fluoxetine and norfluoxetine in plasma from overdose patients

There is a need for fast, simple and reliable analytical methods for the analysis of fluoxetine and norfluoxetine in patients who voluntarily or involuntarily have taken an overdose of the drug. A new liquid chromatographic method with diode array detection is presented herein for the determination of fluoxetine and its main active metabolite in human plasma for toxicological purposes. A mobile phase composed of acetonitrile and aqueous tetramethylammonium perchlorate allows to obtain the complete separation of the analytes on a C18 reversed phase column. The fast and accurate sample pre-treatment step is carried out by means of solid-phase extraction using hydrophilic–lipophilic balance cartridges and loading 100 μL of plasma only. This procedure gives satisfactory extraction yield values, as well as good plasma sample purification from matrix interference. Linearity was obtained in the 150–3000 ng/mL range for both analytes. Selectivity with respect to other psychotropic drugs was satisfactory. The method seems to be suitable for the analysis of fluoxetine and its metabolite in human plasma for depressed patients in overdose.

Enantioselective determination of the novel antidepressant mirtazapine and its active demethylated metabolite in human plasma by means of capillary electrophoresis

Mirtazapine is a recent noradrenergic and specific serotonergic antidepressant drug. A capillary electrophoretic method has been developed for the enantioseparation and analysis of mirtazapine and its main active metabolite, N-desmethylmirtazapine, in human plasma. For method optimisation several experimental parameters were investigated, such as type and concentration of the chiral selector, buffer pH and capillary temperature. Baseline enantioseparation of the analytes was achieved in 2.5 min in a fused silica capillary (50 μm i.d.; 48.5 cm total length; 8.5 cm effective length) using carboxymethyl-β-cyclodextrin, dissolved in a background electrolyte consisting of 50 mM phosphate buffer at pH 2.5, as the chiral selector. UV detection was set at 205 nm. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with hydrophilic–lipophilic balance cartridges (60 mg, 3 mL), eluting the sample with methanol, then concentrating it 37.5 times before injection. Extraction yield values are very satisfactory, being the average 89% for mirtazapine and 73% for N-desmethylmirtazapine. Application of the method to some human plasma samples has given satisfactory results.

Simultaneous liquid chromatographic analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol in human plasma: Comparison of amperometric and coulometric detection

The comparison of two HPLC methods, one with electrochemical detection and the other with coulometric detection, for the simultaneous analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol (MHPG) in human plasma is presented. The careful pre-treatment of plasma samples is based on an innovative two-step procedure by means of solid-phase extraction (SPE) which uses one single hydrophilic–lipophilic balance cartridge. The extraction yield values found were higher than 85% for epinephrine, norepinephrine and MHPG, and higher than 70% for dopamine. The assays carried out on real plasma samples with the coulometric system gave good results in terms of sensitivity (limits of quantitation: 0.10–0.15 ng ml −1 for catecholamines, 0.6 ng ml −1 for MHPG) and selectivity, while interference was sometimes found when using the amperometric system. Precision was also satisfactory, with relative standard deviation values for intermediate precision always lower than 6%. The HPLC method with coulometric detection coupled to a novel SPE procedure is thus suitable for the simultaneous determination of catecholamines and MHPG in plasma of volunteers subjected to experimental stress.

Acidic Pharmaceuticals in Sewage-Methodology, Stability Test, Occurrence, and Removal from Ontario Samples

Abstract A gas chromatography/mass spectrometry (GC/MS) method for the determination of 11 selected acidic pharmaceuticals in sewage influent and effluent at trace levels has been developed. The drugs studied were salicylic acid, clofibric acid, ibuprofen, acetaminophen, gemfibrozil, fenoprofen, naproxen, ketoprofen, diclofenac, fenofibrate, and indomethacin, which are commonly used as analgesic/anti-inflammatory agents or lipid regulators. The antibacterial agent triclosan was also included in this study. A solid-phase extraction procedure using the Waters Oasis HLB (hydrophilic-lipophilic balance) cartridge was optimized for the extraction and elution of these compounds. The acids were then converted into their trimethylsilyl (TMS) derivatives. Final analysis was performed with a Mass Selective Detector in the EI/SIM (electron impact/selected ion monitoring) mode. Recoveries of the drugs in spiked distilled water samples at 1 and 0.1 μ/L levels were better than 80%. Similar recoveries of the drugs were obtained from fortified final effluent samples except for acetaminophen, which could not be recovered even if the extraction was performed immediately. The detection limits for the drugs, based on a concentration factor of 1000, were between 10 and 20 ng/L. A stability study indicated that, except for salicylic acid and acetaminophen, the other acidic pharmaceuticals were better than 75% recovered after the samples had been stored at 4°C in the dark for up to seven days. This method has been applied to quantify acidic drugs in wastewater samples collected from several sewage treatment plants in Ontario. While clofibric acid, acetaminophen, fenoprofen, and fenofibrate have never been detected, the other eight compounds were found in nearly all the influent and effluent samples, from low μ/L to low ng/L levels. Eight sewage treatment plants removed from 0 to 98% of these drugs from the influent.

Simple liquid chromatography method for the rapid simultaneous determination of prednisolone and cortisol in plasma and urine using hydrophilic lipophilic balanced solid phase extraction cartridges

This article describes the development and validation of a simple solid phase extraction (SPE) and HPLC method for the extraction and the specific determination of prednisolone and hydrocortisone (cortisol) in both plasma and urine using one washing step with Oasis ® hydrophilic lipophilic balanced (HLB) cartridges (1 ml/30 mg, 30 μm). Recoveries of prednisolone and cortisol from plasma and urine exceeded 82%. The limit of quantification (LOQ) in plasma and urine was 9.9 and 6.7 ng/ml for cortisol, respectively, and 11.6 and 8.0 ng/ml for prednisolone, respectively. The intraday and interday precision (measured by CV%) for both prednisolone and cortisol in both plasma and urine was always less than 7%. The accuracy (measured by relative error %) for both prednisolone and cortisol in both plasma and urine was always less than 8%. The advantages of the developed method are the use of a one step washing SPE utilising HLB cartridges which do not suffer the drying out problems of conventional SPE cartridges and the time saving when compared with solvent extraction (SE), in addition to the simultaneous determination of prednisolone and cortisol in both plasma and urine.

Determination of Seventeen Polar/Thermolabile Pesticides in Apples and Apricots by Liquid Chromatography/Mass Spectrometry

A simple liquid chromatography/mass spectrometry (LC/MS) approach for the determination of widely used representatives of polar/thermolabile pesticides in fruits was developed and validated. The group of pesticides comprised benzimidazoles and azoles (carbendazim, thiabendazole, imazalil, propiconazole, prochloraz, epoxiconazole, flusilazole, tebuconazole, bitertanol); N-methylcarbamates (carbaryl, carbofuran, methiocarb); and phenylureas and benzoylphenylureas (linuron, diflubenzuron, triflumuron, teflubenzuron, flufenoxuron). Matrixes (apple, apricot) were extracted with acetonitrile and crude extracts were cleaned up by solid-phase extraction (SPE) using either mixed cation exchange or hydrophilic lipophilic balance cartridges. LC separation of pesticides was performed on a reversed-phase column, Discovery C18. Electrospray ionization and ion trap MS/MS detection were applied. For most pesticides, overall recoveries ranged from 75 to 122%, and repeatability (as relative standard deviation) from 5 repetitive determinations of recovery ranged from 3 to 21%. Carbofuran was the only compound for which recovery was not satisfactory due to its loss in the SPE cleanup step. Limits of detection were 0.1-3 microg/kg for benzimidazole and azole fungicides and carbamate insecticides. For urea insecticides, detection limits were slightly higher (3-10 microg/kg).

Simultaneous analysis of six antiepileptic drugs and two selected metabolites in human plasma by liquid chromatography after solid-phase extraction

A rapid and simple liquid chromatographic method with photodiode array detection was developed for the simultaneous determination of six antiepileptic drugs (oxcarbazepine, carbamazepine, lamotrigine, phenobarbital, primidone and phenytoin) and two metabolites (10,11-dihydro-10,11-epoxycarbamazepine and 10,11-dihydro-10-hydroxycarbamazepine, the main active metabolites of carbamazepine and oxcarbazepine, respectively) in human plasma. Separation of the analytes was achieved in less than 11.5 min on a C18 column (150×4.0 mm, i.d. 4.5 μm) with a mobile phase composed of methanol, acetonitrile and a pH 3.0, 15 mM phosphate buffer containing 0.63% triethylamine (19.2:16.8:64.0, (v/v/v)), at 1 ml min −1 flow rate. Two procedures were tested for the pretreatment of human plasma samples: protein precipitation with perchloric acid, and solid-phase extraction. The protein precipitation procedure did not allow for the analysis of 10,11-dihydro-10,11-epoxycarbamazepine. On the contrary, solid-phase extraction with hydrophilic–lipophilic balance cartridges gave good results in terms of extraction efficiency and reproducibility and allowed for the determination of all analytes. The HPLC-DAD method developed, coupled to a careful SPE procedure, seems to be suitable for the plasma level determination of simultaneously administered antiepileptic drugs.

Liquid chromatographic determination of oxcarbazepine and its metabolites in plasma of epileptic patients after solid-phase extraction

A method based on high-performance liquid chromatography with UV detection in combination with solid-phase extraction for sample pretreatment has been developed for the simultaneous analysis of the antiepileptic drug oxcarbazepine and its main metabolites in human plasma. The extraction of the analytes from plasma samples was carried out by means of a selective solid-phase extraction procedure using hydrophilic–lipophilic balance cartridges. The separation was obtained on a reversed-phase column (C 18, 150×4.6 mm I.D., 5 μm) using a phosphate buffer–acetonitrile–methanol–triethylamine mixture (final apparent pH* 3.5) as the mobile phase. Under these chromatographic conditions, oxcarbazepine and its metabolites 10,11-dihydro-10-hydroxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine and the internal standard are baseline separated in less than 9 min. The extraction yield values were >94% for all analytes and the precision, expressed by the RSD%, was in the low percentage range. For the entire method, including sample pre-treatment and HPLC determination, the linearity of the calibration lines, expressed by the linear correlation coefficient, was better than 0.995; the limit of quantitation was 15 ng ml −1. The method was applied to plasma samples from patients undergoing chronic treatment with oxcarbazepine, both in monotherapy and in polytherapy. Based on the analytical parameters precision, accuracy, limit of quantitation and analysis time the method is suitable for routine application in therapeutic drug monitoring.

Determination of reboxetine, a recent antidepressant drug, in human plasma by means of two high-performance liquid chromatography methods

Reboxetine is a new norepinephrine reuptake inhibitor (NRI) drug recently introduced in the therapy for depressed patients. It is effective in the treatment of severe depression and safer to use than traditional tricyclic antidepressants. In this paper an original high-performance liquid chromatography (HPLC) method with ultraviolet detection for the determination of reboxetine in human plasma is described. It uses a C 8 reversed-phase column and a mobile phase composed of acetonitrile and aqueous tetramethylammonium perchlorate. For the analysis of plasma samples containing very low levels of reboxetine, another HPLC method with fluorimetric detection was developed (limit of quantitation, LOQ=11 ng ml −1; limit of detection, LOD=4 ng ml −1). The fluorimetric method is based on precolumn derivatisation of reboxetine with 9-fluorenylmethyl chloroformate. An accurate sample pretreatment of human plasma samples has been implemented by means of solid-phase extraction (SPE) on Oasis HLB (hydrophilic–lipophilic balance) cartridges with very high extraction yields (>95%). Both methods were applied to the analysis of plasma samples from depressed patients undergoing therapy with reboxetine and gave satisfactory results in terms of precision (RSD<4.5%) and accuracy (mean recovery>94%).