Porous membrane-protected molecularly imprinted polymer micro-solid-phase extraction for analysis of urinary cocaine and its metabolites using liquid chromatography – Tandem mass spectrometry

Porous membrane-protected micro-solid phase extraction (μ-SPE) using a molecularly imprinted polymer (MIP) as an adsorbent has been proposed as an integrated extraction-cleanup procedure for isolating cocaine (COC) and its metabolites [benzoylecgonine (BZE), ecgonine methyl ester (EME), and cocaethylene (CE)] from human urine. MIP beads have been synthesized using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2′-azobisisobutyronitrile (AIBN) as an initiator. High performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) has been used for quantifying the analytes after MIP-μ-SPE. Variables such as urine pH, adsorption temperature and time, mechanical (orbital-horizontal) stirring; and composition of the eluting solution and eluting time, were evaluated. The proposed method was shown to be precise and accurate [relative standard deviations (RSDs) of intra- and inter-day tests ranging from 3 to 8% and from 2 to 10%, respectively]; and analytical recoveries in the range of 89–100%). In addition, excellent accuracy was also verified after analyzing a FDT +25% control material for BZE. The detection limits were in the range of 0.16–1.7 ng L⁻¹, low enough for confirmative conclusions regarding cocaine abuse. The method was finally applied for screening/quantifying cocaine and metabolites in urine samples from poly-drug abusers.     

Comparison of molecularly imprinted,mixed-mode and hydrophilic balance sorbents performance in the solid-phase extraction of amphetamine drugs from wastewater samples for liquid chromatography–tandem mass spectrometry determination

Recent studies have shown that amphetamines and other drugs of abuse residues occur in wastewater. Consequently, several methods have been developed for their determination by solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS). However, a major drawback of these methods is the lack of selectivity during SPE that results in reduced sensitivity, due to matrix effects, and in some cases in low precision and poor accuracy. In order to tackle this problem, three different SPE alternatives have been evaluated in this work for the determination of five amphetamines: common hydrophilic balance (Oasis HLB), mixed-mode (Oasis MCX) and molecularly imprinted polymers (MIPs) sorbents. Among them, Oasis HLB showed the worst performance, as three amphetamines (MDA, MDMA and MDEA) could not be determined because of interfering signals in the LC–MS/MS chromatogram, and amphetamine recoveries could not be corrected by the use of the deuterated analogue internal standard. Oasis MCX permitted the determination of all target analytes, but with still strong signal suppression: ca. 70% signal drop with wastewater samples, which could in this case be corrected by the internal standards providing acceptable trueness (overall recoveries: 101–137%), precision (RSD: 2.0–12%) and limits of detection (LOD: 1.5–4.4 ng/L). Alternatively, MIPs rendered cleaner extracts with less matrix effects (ca. 30% signal drop), and thus lower LODs (0.5–2.7 ng/L) and even better trueness (91–114% overall recovery) and precision (1.5–4.4%RSD). The final application of the method with MIP cartridges showed the presence of MDA and MDMA in the seven analysed wastewaters at the 4–20 ng/L level.     

Determination of methotrexate in environmental samples by solid phase extraction and high performance liquid chromatography: ultraviolet or tandem mass spectrometry detection?

In order to assess exposure levels of hospital personnel involved in the preparation and administration of antineoplastic drugs, environmental monitoring should be carried out. Wipe samples, pads, gloves and air samples should be collected at the end of each work shift, properly treated and then analysed using instrumental techniques which are sufficiently sensitive and specific to detect even trace amounts of drug. In this study, a method using high performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS), incorporating solid phase extraction (SPE), was validated for determination of methotrexate (MTX) in wipe and air samples. Each step of the method was first developed and optimised using ultraviolet detection (UV), and afterwards tandem mass spectrometry was used to obtain a lower limit of quantitation when the expected drug level was less than the analytical UV detection limit. SPE enabled a 20-fold preconcentration of the analyte when using HPLC/UV and a further 30-fold preconcentration was obtained when analysing samples by HPLC/MS/MS. For example, the limit of quantitation (LLQ) was lowered from 3000 ng on wipe (direct injection onto an HPLC/UV system) to 5 ng on wipe (SPE plus HPLC/MS/MS). 7-hydroxymethotrexate was used as internal standard to assess precision and accuracy.     

High performance liquid chromatography–tandem mass spectrometry for the analysis of 10 pesticides in water: A comparison between membrane-assisted solvent extraction and solid phase extraction

This work describes the application of two sample preparation methods: membrane-assisted solvent extraction (MASE) and solid phase extraction (SPE) in combination with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) for the determination of 10 pesticides in surface and ground water. Optimal extraction conditions for MASE were 60 min extraction time at 30 °C with a solvent volume of 100 μL toluene. 5 μL of the toluene extract were directly injected in the HPLC–MS–MS system. Concerning SPE, two materials were tested and C18 was superior to Oasis HLB. Complete desorption was ensured by desorbing the SPE (C18) cartridge with 3 mL of an acetonitrile/methanol mixture (1:1). After evaporation, the extract was injected in the analytical system. Analyte breakthrough was not found for the investigated compounds. For both methods, high extraction yields were achieved, in detail 71% (metalaxyl) till 105% (linuron) for MASE and 52% (ethiofencarb) till 77% (prometryne) for SPE (C18). Detection limits were in the low ng/L range for both methods and precision, expressed as the relative standard deviation (RSD) of the peak areas was below 13%. Five real water samples were analyzed applying both extraction methods. The results were in good agreement and standard addition proved that no matrix effects (such as ion suppression) occurred. In this comparison SPE has the potential of larger sensitivity whereas faster analysis and slightly better recoveries were achieved with MASE. MASE shows potential to be a promising alternative to the conventional off-line SPE concerning low to medium polar compounds.     

Quantification of urinary conjugates of bisphenol A, 2,5-dichlorophenol,and 2-hydroxy-4-methoxybenzophenone in humans by online solid phase extraction–high performance liquid chromatography–tandem mass spectrometry

Urinary concentrations of phenols or their metabolites have been used as biomarkers to assess the prevalence of exposure to these compounds in the general population. Total urinary concentrations, which include both free and conjugated (glucuronide and sulfated) forms of the compounds, are usually reported. From a toxicologic standpoint, the relative concentrations of the free species compared with their conjugated analogs can be important because conjugation may reduce the potential biologic activity of the phenols. In this study, we determined the percentage of glucuronide and sulfate conjugates of three phenolic compounds, bisphenol A (BPA), 2,5-dichlorophenol (2,5-DCP), and 2-hydroxy-4-methoxybenzophenone (benzophenone-3, BP-3) in 30 urine samples collected between 2000 and 2004 from a demographically diverse group of anonymous adult volunteers. We used a sensitive on-line solid phase extraction–isotope dilution–high performance liquid chromatography–tandem mass spectrometry method. These three phenols were detected frequently in the urine samples tested. Only small percentages of the compounds (9.5% for BPA, and 3% for 2,5-DCP and BP-3) were excreted in their free form. The percentage of the sulfate conjugate was about twice that of the free compound. The glucuronide conjugate was the major metabolite, representing 69.5% (BPA), 89% (2,5-DCP), and 84.6% (BP-3) of the total amount excreted in urine. These results are in agreement with those reported before which suggested that BPA-glucuronide was an important BPA urinary metabolite in humans. To our knowledge, this is the first study describing the distribution of urinary conjugates of BP-3 and 2,5-DCP in humans.