Environment
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Identification of Pharmaceuticals in The Aquatic Environment Using HPLC-ESI-Q-TOF-MS and Elimination of Erythromycin Through Photo-Induced Degradation
Chapters
Summary August 1st, 2018
We present a protocol for non-targeted analysis using time of flight mass spectrometry as a perfect tool to identify pharmaceuticals in waters. We demonstrate the application of UV irradiation for their elimination. Analysis involving irradiation, compound isolation, identification and kinetic modelling of the degradation profiles is illustrated.
Transcript
This method can help answer key questions in environmental protection, such as awareness of antibiotics in the aquatic environment. The main advantage of this technique is that it can detect pharmaceutical pollutants at very low concentrations and identifies them simultaneously. Even though this method can provide insight into pharmaceuticals and wastewater influence and river waters, it can also be applied to other systems, such as pesticides or hormone-like substances in the aquatic environment.
To begin this procedure, collect approximately one liter of water to prepare the samples. Filter the sample over a blue band filter to remove course particles. Next add three milliliters of methanol to the solid phase extraction cartridge to be equilibrating it.
Wait for the methanol to leave the cartridge, and then add three milliliters of ultrapure water. After the water has left the cartridge, apply the filtrate and use a diaphragm pump, or other moderate vacuum, to increase the flow velocity. So pre-concentration is very important.
Make sure to use a solid phase extraction cartridge with the right solid phase. Wash the sample with three milliliters of ultrapure water. Then use three milliliters of ethanol to elute the analytes from the cartridge sorbate.
Using a rotary evaporator, concentrate and dry the eluted analytes. Dissolve the resulting residue in one milliliter of ultrapure water. After this, filter the solution through a syringe filter.
Store them in a vial until ready to perform non-targeted analysis by HPLC-ESI-QTOF-MS. To begin the UV irradiation experiments, dissolve the antibiotic compound of interest in ultrapure water to achieve a final concentration of 20 milligrams per liter. Transfer 750 milliliters of this solution to the one liter photoreactor.
Next, add a magnetic stirrer and introduce a 15 watt UV lamp into the reactor. Begin stirring at 500 RPM. Using the dropwise addition of either hydrochloric acid or ammonia, adjust the pH to the desired value.
Use a syringe to transfer two milliliters of the reaction solution to a two milliliter glass vial. Mark this vial as the sample at time zero. After this, switch on the UV lamp and begin tracking the elapsed time.
Draw a two milliliter sample every 30 seconds during the first five minutes. Then, take a sample every 60 seconds for the remainder of the experiment. Store the vials at four degrees Celsius until ready to analyze.
To begin LC MS, transfer the vial to the auto sampler. Set all of the relevant parameters as outlined in table one of the text protocol, and start the measurement. Using high resolution MS and MS/MS latitude is the most promising technique for non-targeted analysis of pharmaceuticals in waters.
Then perform kinetic analysis and curve fitting as outlined in the text protocol. In this study, both river water and ultrapure water samples are analyzed to detect and identify pharmaceutical pollutants. After solid phase extraction, each river water sample is seen to have a yellowish or dark green color, indicating the presence of chlorophyll containing substances.
Ultrapure water samples remained clear, as expected. A base peak chromatogram for the representative river water samples contained more than 25 peaks, each reflecting a different compound. These substances are then identified by deriving the molecular formulas and comparing them to available reference standards.
This comparison reveals the presence of several pharmaceuticals found in German surface water, including the beta blocker metoprolol, the analgesic carbamazepine, as well as the macrolide antibiotic erythromycin A, and its derivative anhydroerythromycin A.UVC irradiation experiments are then carried out at different pH values to determine effective elimination conditions using erythromycin as an example. Concentration time diagrams show that the fastest degradation occurs at pH 7, while the slowest is seen at pH 3, indicating that photo induced degradation for this antibiotic should be performed at neutral pH. Following this procedure, other methods like SESP-NMR arbitrip MS-OTUC can be performed in order to answer additional questions like oxidation of degradates and tip-off ollization.
After watching this video, you should have a good understanding of how to analyze pharmaceuticals in artificial and environmental water bodies and how to investigate their photo-irradiation induced elimination. Don't forget that working with chemicals, pharmaceutics, and river or waste water can be hazardous and precautions, such as personal protective clothing, outer equipment, and, in case of waste water, vaccinations should always be taken while or prior to performing this procedure.
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