Microwave irradiation for a fast gas chromatography–mass spectrometric analysis of polysaccharide-based plasma volume expanders in human urine

In this contribution we tested the possibility to use microwave irradiation for the screening and confirmation pre-treatment steps of hydroxyethylstarch, with the aim to speed up gas chromatography–mass spectrometric procedures. Acid hydrolysis and derivatization processes were conducted in a temperature-controlled single beam microwave oven for organic synthesis. The kinetics of hydroxyethylstarch chemical hydrolysis and derivatization were investigated at different microwave power, incubation temperature and incubation time. The best hydrolysis conditions were found at a microwave power value of 1200 W (T 100 °C) with an incubation time of 2 min; whereas the best derivatization conditions were found at a microwave power value of 1020 W (T 100 °C) with an incubation time of 5 min. The effectiveness of this approach was evaluated by gas chromatography–mass spectrometry analyzing more than 20 different pools of blank urine samples spiked with hydroxyethylstarch at a concentration of 1 mg/mL. The results showed that the effect of microwave irradiation on the chemical hydrolysis process was very remarkable: the total sample preparation time can be shortened by 58 min compared to the reference method (2 min instead of 60 min). In addition to this, the time necessary for the derivatization process can also be drastically shortened with respect to the reference procedure (5 min instead of 30 min). The repeatability of the hydrolysis and derivatization recoveries, the limit of detection and the matrix interferences were comparable to the reference method accredited under the ISO 17025 guidelines and presently followed by the accredited sports anti-doping laboratory of Rome.