Percorrer por autor "Berg, Thomas"
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- An accurate and precise liquid chromatography–tandem mass spectrometry method for the determination of six phosphatidylethanol homologues in whole blood with phospholipid interferences minimizedPublication . Maria, Marisa; Neng, Nuno R.; Berg, ThomasAlcohol consumption is associated with a wide risk of different diseases, injury and death, and has significant social and economic consequences worldwide. Phosphatidylethanol (PEth) is a group of promising direct alcohol biomarkers, with a significantly longer half-life in blood than ethanol, which can be measured to predict different drinking patterns, such as heavy- and social drinking. This study aimed to develop and validate an accurate and precise LC-MS/MS method for the determination of six PEth homologues in whole blood with minimal interference from unwanted phospholipids. Different organic solvent mixtures for liquid-liquid extraction were investigated to obtain satisfactory recovery of PEth homologues and removal of the lyso-phospholipids and other early eluting phospholipids. The mixture of heptane/2-propanol (80:20, v:v) gave lower phospholipid background and better signal/noise values for the PEth peaks. An LC-MS/MS TQ-S system from Waters was used for the instrumental analysis. The main part of unwanted phospholipids were separated from the PEth homologues on an Acquity BEH C18 column (50 × 2.1 mm ID, 1.7 µm particles) using a buffer-free mobile phase of 0.025 % ammonia in Type 1 water, pH 10.7, as solvent A and methanol as solvent B. Validation and quantification of 22 authentic blood samples showed that the developed LC-MS/MS method is sensitive, precise and accurate for the determination of the six PEth homologues in whole blood. Lower limit of quantification was 10 nM for all compounds. No matrix effects were observed, possibly due to the successful strategies incorporated to avoid the influence of unwanted phospholipids.
- Simultaneous determination of three phosphatidylethanol homologues, 12 drugs and metabolites in whole blood by LC–MS/MSPublication . Maria, Marisa H.; Neng, Nuno R.; Berg, ThomasThe use of alcohol, legal and illicit substances poses great negative consequences on health and economy worldwide. LC-MS/MS allow simultaneous determination of multiple compounds in biological matrices. The aim of this study was to develop a LC-MS/MS method for the determination of the alcohol biomarker phosphatidylethanol (PEth) – including three homologues (PEth 16:0/18:1, PEth 16:0/18:2, PEth 18:0/18:1) - cocaine and three metabolites, and 8 other drugs in whole blood. Whole blood in K2EDTA tubes was prepared by liquid-liquid extraction using heptane/ethyl acetate/2-propanol (16:64:20, v:v:v). Chromatographic separation was achieved on an Acquity BEH C18 column (50 × 2.1 mm I.D., 1.7 µm particles). Mobile phase was 0.025 % ammonia, pH 10.7 (Solvent A) and methanol (Solvent B). The method was fully validated with isotope-labelled internal standards for 10 compounds. Inter-assay precision and accuracy were within ± 16 % for all analytes at five to seven tested concentrations. Recovery was within 42–79 % for 14 compounds and 11 % for benzoylecgonine. Matrix effects were within ± 25 % for most analytes. Internal standards compensated for matrix effects for compounds that had their own internal standards. A robust, precise, and accurate LC-MS/MS method for the determinations of three PEth homologues and 12 drugs and metabolites was, developed and validated. The method is valuable, especially for detecting polydrug use and alcohol consumption. To the best of our knowledge, this is the first LC-MS/MS method for the simultaneous determination of three PEth homologues and different drugs and metabolites.
- Sorbent strip microextraction as a practical tool for drug screening : application to opioids and local anesthetics in human urinePublication . Maria, Marisa H.; Berg, Thomas; Neng, Nuno R.The present contribution proposes a new design for adsorptive microextraction devices that promote a user-friendly and greener analytical approach. Novel Sorbent Strip Microextraction (SSμE) devices were made using a flexible adhesive film coated with convenient sorbents. Comparing the previous adsorptive microextraction devices, i.e., bar adsorptive microextraction and multi-sphere adsorptive microextraction, the main advantage of the sorbent strip device is its simple design and reduced device preparation time and waste. To demonstrate its applicability, three opioids (buprenorphine, tapentadol, and tramadol) and two local anesthetics (articaine and bupivacaine) were used as model compounds in urine matrices, followed by high-performance liquid chromatography with diode array detector (HPLC-DAD) analysis. Key parameters such as sorbent type, desorption conditions, and microextraction variables were systematically optimized by experimental designs. Under the final conditions, the method achieved recoveries ranging from 78% to 108%, trueness within ±7% and precision expressed by relative standard deviation below 13%. The technique demonstrated good linearity (r2 ≥ 0.9922) across dynamic ranges of 5–500 ng/mL for local anesthetics and 50–5000 ng/mL for opioids. The validated SSμE/HPLC-DAD methodology was successfully applied to real urine samples, confirming its high precision and accuracy. The proposed microextraction technique offers a practical, eco-friendly, and effective alternative for routine drug screening in complex biological matrices and presents significant advantages over traditional and other microextraction-based methods.