Solid Phase Extraction of Amphetamine Using Different Commercially Available Molecularly Imprinted Polymer (MIP) Sorbents
Analysis of illicit drugs such as amphetamines are typically done by chromatographic methods like gas chromatography (GC) and liquid chromatography (LC). However, even with the introduction of LC-MS and GC-MS, sampling pretreatment still plays a very important role in drug analysis. Solid phase extraction (SPE) materials were developed to capture illicit drugs and their metabolites in complex samples such as blood and urine. They have become commercially available to improve drug analysis. Molecularly imprinted polymers (MIPs) are are a class of polymer-based recognition elements tailored to target a specific chemical or class of structurally related compounds. In this study, analysis using a sample pretreatment method (SPE) with MIP was compared with analysis without treatment. In addition, the performance of two commercially available MIPs are compared by extracting amphetamine from water and synthetic urine.
Using amphetamine standard, the MS spectra obtained using both negative and positive mode is shown in Figure 1. In negative mode, several peaks were observed but none corresponds to amphetamine. The peaks observed in negative mode scan especially m/z = 141 is also observed in blank samples (water). However, the spectra using the positive mode, a peak at m/z = 91 corresponds to amphetamine transition 136 to 91. In this regards, positive mode was utilized in the analysis of amphetamine water and synthetic urine samples.
The role of sample pretreatment was assessed by analyzing the spiked water and synthetic urine samples without pretreatment method. Figure 2 shows the mass spectra of amphetamine mixed with water and synthetic urine samples where the signal obtained from synthetic urine samples is very low compared to the water samples. This is also lower compared to the one obtained in with sample pretreatment method or MIP (Figures 3 and 4). The recovery of amphetamine is similar to one another regardless of whichever MIP cartridge or sample utilized (Figure 3 and 4).
Upon using commercially MIPs, the percent recovery in either water samples or synthetic urine samples are similar. This means doing a sample pretreatment method is more effective to achieve a higher recovery. The AFFINIMIP is more superior to Supelco in terms of time preparation. This is due to shorter drying time (30 sec) in AFFINIMI-SPE Amphetamines in comparison to Supelco-MIP (5-10 mins).
I would like to thank Maximillian Baria and Eric Nguyen in the preliminary trials of this study and my mentor, Dr. Elmer-Rico E. Mojica for his support in the project. I would like to thank Prof. Nigel Yarlett for the amphetamine standard, Prof. Zhaohua Dai for the amphetamine standards and the use of GC-MS, Prof. Rita K. Upmacis for assistance in MS analysis. I also like to thank Pace University Undergraduate Research Initiative for the research grant.
Since the beginning of the fall semester, I have been working with Dr. Mojica on different experimental methods for performing drug analysis. I have presented my research at number of conferences. The most novel experience in my research were the poster presentations that I have done in different scientific meetings. I presented my research as poster at the American Chemical Society (ACS) National Conference in Dallas, the Eastern Colleges Scientific Conference (ECSC), William Patterson University Undergraduate Research Symposium, and Dyson Society of Fellows Annual Meeting. I will be presenting it orally next week at the ACS URS in St. Johns University. I have learned a lot of things in doing these presentations and attending these conference. I was able to gain professional experience on how to interact with other people or some sort of real world experience. In addition to this, I was lucky to meet people that I never expect to, like Prof. Donna Nelson which is the science supervisor for the AMC series “Breaking Bad” which I met in Dallas and Sir Harold Kroto, a Nobel laureate in Chemistry whom I met in WPU URS. I was also inducted as an associate in the Dyson Society of Fellows because of my participation in the annual meeting.
I may be graduating but I intend on continuing my research with Dr. Mojica, because I will be attending Pace for the Master’s program in Forensic Science. I will use other MIP sorbents as well as possibly using real urine samples along with other illicit drugs like methamphetamine to further our results. I am very fortunate to work personally with a mentor on performing experimental research since not all undergraduate students have this opportunity. When in the labs I have learned professional techniques in utilizing laboratory instruments as well as how to troubleshoot problems that arise during the analysis. I am grateful to be a part of such an extraordinary research team under the mentorship of Dr. Mojica. I have learned various skills and techniques that will be beneficial when entering the professional world; hopefully working with a government agency as a forensic chemist.
Figure 1. Mass spectra of amphetamine standard obtained using negative mode (above) and positive mode (below).
Figure 2. Mass spectra of amphetamine mixed with water and synthetic urine samples analyzed without sample pretreatment.
Figure 3. Mass spectra of amphetamine standard in water samples recovered by Supel-MIP (above) and AFFINIMIP-SPE (below).
Figure 4. Mass spectra of amphetamine standard in synthetic urine samples recovered by Supel-MIP (above) and AFFINIMIP-SPE (below).