Sub-ppt Mass Spectrometric Detection of ... - ACS Publications

Subscriber access provided by University of South Florida

Article

Sub-ppt Mass Spectrometric Detection of Therapeutic Drugs in Complex Biological Matrices Using Polystyrene-Microsphere-Coated Paper Spray Teng Wang, Yajun Zheng, Xiaoting Wang, Daniel E Austin, and Zhiping Zhang Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.7b01296 • Publication Date (Web): 07 Jul 2017 Downloaded from http://pubs.acs.org on July 8, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

Sub-ppt Mass Spectrometric Detection of Therapeutic Drugs in Complex Biological Matrices Using Polystyrene-Microsphere-Coated Paper Spray Teng Wang,a,‡ Yajun Zheng,a,‡ Xiaoting Wang,a Daniel E. Austin,b,* and Zhiping Zhanga,* a

School of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an 710065, China

b

Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, United States

* To whom correspondence should be addressed. E-mail: [email protected] or [email protected] ‡

These authors contributed equally to this work.

ABSTRACT: Polystyrene (PS) is a class of polymer materials that offers great potential for various applications. However, the applications of PS microspheres in paper spray mass spectrometry are largely underexplored. Herein we prepared a series of PS microspheres via a simple dispersion polymerization and then used them as coating materials for paper spray mass spectrometry (MS) in high-sensitivity analysis of various therapeutic drugs in complex biological matrices. In the preparation of PS-coated papers, the coating method was found playing a key role in determining the performance of the resulting paper substrate in addition to other parameters (e.g., starch type and amount, PS coating amount and spray solvent). We also found that as a solvent was applied on PS-coated paper for paper spray, the analytes of interest would be first extracted out and then moved to the tip of paper triangle for spray along with the applied solvent. In the process, the surface energy of PS particles had a strong impact on the desorption performance of analytes from PS-coated paper substrate, and the PS with a high surface energy favored the elution of analytes to allow a high MS sensitivity. When the prepared PS coated paper was used as a substrate for paper spray, it gave high sensitivity in analysis of therapeutic drugs in various biological matrices such as whole blood, serum, and urine with excellent repeatability and reproducibility. In contrast to uncoated filter paper, an improvement of 10 – 546-fold in sensitivity was achieved using PS-coated paper for paper spray, and an estimated lower limit of quantitation (LLOQs) in the range of 0.004 – 0.084 ng mL-1 was obtained. The present study is significant in exploring the potential of PS for high-sensitivity MS analysis, and it provides a promising platform in the translation of MS technique to clinical applications.

1. INTRODUCTION Polystyrene (PS) is an amorphous and glassy polymer with highly ordered structures solely constructed by the polymerization of styrene. Owing to its strong covalent linkages between light elements (H and C), PS possesses many unique features such as low density, ease of handling, negligible solubility in water, non-biodegradability and non-toxicity, which make it applicable to diverse fields including wastewater treatment,1-7 chromatographic separation,8-14 solid-phase extraction,15-25 and adsorption of proteins/peptides.26-34 Accurate measurement of therapeutic drugs and their derivatives in complex biological matrices is of great significance both in pharmacology and in biology. Paper spray mass spectrometry (MS)35-37 based on paper substrate has been proven to be one of the most attractive strategies for therapeutic drugs, providing not only strong quantitative capabilities but also highly simplified procedures that consume ultra-small volumes of sample. For the purpose of improving the analytical performance of paper spray, considerable attention has been focused on exploring various paper substrates such as commercially available papers,35,37,38 silica coated paper,35,39 zirconia coated paper,40 carbon nanotube coated paper,41,42 metal-

organic framework coated paper,43 trichloro(3,3,3-trifluoropropyl) silane modified paper,44 wax-printed paper,45 and paper with a paraffin barrier.46 Taking into account the unique properties of PS particles, the application of PS for paper spray in measurement of therapeutic drugs in complex biological matrices is promising. Although PS microspheres are commercially available, the high cost (around $100/g) prevents their practical application in paper spray analysis. The general strategies for synthesis of PS microspheres include swelling technique47 and dispersion polymerization.48 In contrast to the former method, the latter has the characteristics of simplicity and ease, and it produces particles with a very narrow size distribution.49 Based on this fact, herein a series of PS microspheres were first prepared according to the reported dispersion polymerization of styrene4953 in ethanol using benzoyl peroxide (BPO) as initiator and poly(N-vinylpyrrolidone) (PVP) as a steric stabilizer. The resulting PS microspheres were then coated onto the surface of filter paper through a vacuum filtration approach developed in our lab.39,40,54 Different from the previous reports, a hot coating method was developed to coat as-synthesized PS microspheres onto filter paper, and the obtained paper substrate demonstrated a much better performance in MS analysis than

ACS Paragon Plus Environment

Analytical Chemistry uncoated filter paper. To gain insight into the desorption behavior of analytes from PS-coated paper substrate in paper spray, much effort has been made to probe the surface properties of PS particles. The results demonstrate that the surface energy of PS particles has a large impact on the desorption of analytes from their surfaces. In addition, the PS-coated paper obtained was successfully used as a substrate for paper spray mass spectrometry in high-sensitivity analysis of various therapeutic drugs in complex biological samples such as whole blood, serum and urine samples.

2. EXPERIMENTAL SECTION

directly transferred to a Buchner funnel covered by a piece of blank filter paper (11 cm in diameter) for coating. The other steps were same as in previous reports.39,40,43,54-56 (b) Cooling-coating method: Different from the above method, 0.015 g of crosslinked starch and 0.7 g of PS particles were dispersed into 100 mL of deionized water followed by sonicating for 5 min, and then the resulting solution was heated to its boiling point. After that, the solution was immediately removed from heat and cooled to room temperature, and this solution was then used directly for coating a filter paper. (c) Hot coating method: This method was very similar to the cooling-coating method described above. The difference between them was that using the hot coating mode, the mixture solution containing 0.015 g of crosslinked starch and 0.7 g of PS particles was directly used for coating after heating to its boiling point. Characterization of PS particles and PS coated paper substrate. FT-IR spectra of the synthesized PS particles were recorded with a Thermo Nicolet 5700 Series infrared spectrometer with transmission mode in the range of 4000 - 400 cm-1. The resolution was 4 cm-1 and 32 scans were signal-averaged in each interferogram. The IR measurement was carried out for PS particles embedded in a KBr pellet. The surface structures of as-synthesized PS particles and PS coated paper substrates were examined by a JEOL JSM-6390A scanning electron microscope (SEM). The contact angles of water and diiodomethane on the PS particles and their corresponding surface energies were measured by a JC2000DS contact angle meter equipped with a CCD camera. Each data point for contact angles is an average of eight replicates, and error bars indicate standard deviation. MS analysis. All experiments on paper spray MS were carried out with a TSQ Quantum Access Max mass spectrometer (Thermo Fisher Scientific, San Jose, CA, USA). For paper spray, the coated paper substrate was cut into a triangle (around 11 mm height and 7 mm base width). The distance between the tip of paper triangle and the MS inlet capillary was about 8 mm. Mass spectra were recorded in the positive ion mode with a capillary temperature of 270 °C. The identification of analyte ions was confirmed by tandem mass spectrometry (MS/MS) using collision-induced dissociation (CID). Argon gas (99.995% purity) was used as the collision gas. Selected reaction monitoring (SRM) mode was used for the analysis of therapeutic drugs. Each data point is an average of four replicates, and error bars indicate standard deviation. Ethical conduct of research. The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declarations of

Chemicals and materials. Styrene, BPO and PVP were ordered from Tianjin Tianli Chemical Reagents Ltd. (Tianjin, China), Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China) and Chengdu Kelong Chemical Co., Ltd. (Chengdu, China), respectively. The filter paper to be coated with PS particles was purchased from Hangzhou Special Paper Co. (Fuyang, China). The therapeutic drug standards used, including amitriptyline, clozapine, quetiapine, verapamil and risperidone and their isotopes, were purchased from Sigma-Aldrich (St. Louis, USA) and Toronto Research Chemicals Inc. (Toronto, Canada). Other chemicals and solvents were analytical grade or better and therefore used without further purification. Bovine whole blood, serum, and synthetic urine were purchased from Lanzhou Institute of Biological Products Co., Ltd. (Lanzhou, China), Shaanxi Lebo Biochemical Technology Co., Ltd. (Xi’an, China) and Dongguan Xinheng Science & Technology Co. Ltd. (Dongguan, China), respectively. Preparation of PS particles. PS microspheres were prepared according to previous reports.49-53 In a typical procedure, 1.0 g PVP and 1.0 g BPO were dissolved into 80 mL of ethanol. When the mixture was heated to 70 oC, a certain volume of styrene monomer, ranging from 10 to 40 mL, was poured into the reaction solution followed by a reaction period of 9 h under gentle stirring (ca. 120 rpm). The resulting particles were collected and washed with absolute ethanol three times, each with around 35 mL. The PS samples were subsequently separated using a TDZ5B-WS centrifuge (Shanghai LuXiangyi Centrifuge Instrument Co. Ltd., Shanghai, China) with a speed of 3000 rpm. Finally, the prepared white powder was dried in a vacuum oven at 50 oC for 24 h. The samples were stored at room temperature in a sealed bag until use. Preparation of PS coated paper substrates. Three different methods were used to create the substrates: (a) General method: This method is similar to the one reported previously.39,40,43,54-56 Specifically, 0.015 g of crosslinked starch was dissolved into 100 mL of deionized water followed by heat10 ing to its boiling (c) (d) (a) (b) solvent point. After cool10 sample ing to room tem10 R = 0.9987 perature, 0.7 g of 10 HV PS particles were 10 10 10 10 10 10 dispersed into -1 X2,000 X2,000 10μm 10μm Concentration of Quetiapine (ng mL ) the above soluFigure 1. SEM images of (a) PS microspheres obtained by reaction of 25 mL styrene and 1.0 g BPO in the presence of tion and soni1.0 g PVP using 80 mL ethanol as solvent and (b) the surface structure of the generated PS coated paper substrate; cated for 5 min. (c) Paper spray using the resulting PS coated paper as substrate; (d) Quantitative analysis of dried blood spots spiked Then the resulting solution was with quetiapine and its isotopologue, D8-quetiapine. Bars represent the standard deviation of analyses for four repli1

0

IA/IIS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 9

-1

2

-2

-3

-2

cates with independent paper substrates.


-1

0

1

2

Xi'an Shiyou University and Brigham Young University for all biological sample experimental investigations.

3. RESULTS AND DISCUSSION 3.1 Synthesis and characterization of PS microspheres. To demonstrate the potential application of PS for paper spray in measurement of therapeutic drugs in biological matrices, a series of PS microspheres were first synthesized via dispersion polymerization of styrene49-53 in ethanol media using benzoyl peroxide (BPO) as initiator and poly(N-vinylpyrrolidone) (PVP) as a steric stabilizer. Figure 1a illustrates the typical SEM images of PS microspheres (Figure S1) obtained by a reaction of 25 mL styrene and 1.0 g BPO in the presence of 1.0 g PVP using 80 mL ethanol as solvent; uniform microspheres with diameters of around 4.2 μm were obtained. After coating as-synthesized PS particles on the surface of filter paper through a vacuum filtration approach39,40,54 with the hot coating method (as discussed in the Experimental section), the nearly monodisperse PS particles formed a dense layer on the filter paper (Figure 1b), with the PS microspheres connected to each other by starch gel added as part of the coating solution.54 The capability of the resulting PS-coated paper substrate was demonstrated by the analysis of therapeutic drugs in whole blood using paper spray (Figure 1c). Whole bovine blood spiked with quetiapine at concentrations spanning from 0.001 to 100 ng mL-1, was deposited on small paper triangles (each around 11 mm height and 9.5 mm base width). The quantity of quetiapine in the whole blood samples was measured using the ratio of the fragment ion (m/z 270) abundance of quetiapine to that of the corresponding fragment ion (m/z 275) generated from D8quetiapine, which was also added to the blood sample as an internal standard. As shown in Figure 1d, the relative response was linear across a wide range of concentrations (0.005 - 100 ng mL-1) with a limit of quantitation of 0.005 ng mL-1 using the PS coated paper substrate. To the best of our knowledge, this is the most effective paper sub- 100 (a) strate for high-sensitivity analysis 80 60 of therapeutic drugs in whole 40 blood samples comparable to the 20 coated blade spray57 but without 0 the need for preconditioning, ethod ethod ethod sample extraction and rinsing. ral M oating M oating M C Gene C Relative Intensity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.2 Influences of experimental parameters. As in the previous reports,39,40,43,54-56 the surface properties of the generated PS coated paper substrates depended strongly on the experimental parameters. In the current investigation, we found that the coating method had a strong effect on the performance of the resulting paper substrate in addition to the parameters such as starch type, starch amount, PS coating amount and spray solvent (Figure S2). Figure 2a shows the comparison of the perfor-

ng Cooli

mance of the resulting paper substrates from different coating methods including the general method, the cooling-coating method and the hot coating method as described above. The obtained paper substrates were evaluated by the product ion (m/z 84) abundance of amitriptyline (100 ng mL-1) in dried blood spot using paper spray. It was apparent that by varying the coating method, the performance of the paper substrate changed significantly. Among them, the paper from the hot coating method showed the best performance compared with those made using the general method and the cooling-coating method. These results suggest that in coating a filter paper through vacuum filtration approach, using a hot mixture solution containing starch and PS particles was the most effective way to improve the performance of the resulting paper substrate. This in turn might be related to their different surface properties. To gain insight into the properties of the paper substrates, their surface structures were examined by SEM. Figure 2b-d shows the typical SEM images of the paper substrates from different methods. As the general coating method was employed, it was clear that the paper substrate was covered by a dense layer of PS particles, and there were some tiny fissures in the structure (Figure 2b). When the cooling-coating method was used for coating with PS particles, the surface structures of the resulting paper was noticeably different (Figure 2c). Its surface was less smooth than the one from the general method (Figure 2b), and there were lots of holes in the structure, likely attributable to the simultaneous heating of the mixture of starch and PS particles. The surface structure of the paper generated from the hot coating method (Figure 2d) was very similar to that from the cooling coating method (Figure 2c). The difference between them was only that the surface from the hot coating method became much coarser and there were more holes at the surface of the resulting paper, which could be due to the aggregation of starch and PS particles during the hot

(b)

Hot

(c)

X100 General Method

(d)

X100

100μm

X100

100μm Cooling Coating Method

(e)

2.0

Hot Coating Method

Intensity (a.u.)

Page 3 of 9

1.5

100μm general method cooling coating method hot coating method

1.0 0.5 0.0

(f)

200 220 240 260 280 300

Wavelength (nm)

Figure 2. (a) Comparison of the performance of the resulting paper substrates from different coating methods [Note: The evaluation was based on the analysis of 100 ng mL -1 amitriptyline ((M + H)+, m/z 278, product ion, m/z 84) in dried blood spot by using paper spray (spray solvent: 25 μL of acetonitrile; applied voltage: 3.5 kV); (b)-(d) SEM images of the prepared paper substrates using (b) general method, (c) cooling-coating method and (d) hot coating method; (e) Photographic image of the collected filtrates from different coating methods, in which 100 μL of 0.02% iodine solution was added for the chromogenic reaction; (f) UV-vis spectra of the collected filtrates from different coating methods as indicated in this figure.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 9

coating process. The above discussion shows that with varying the coating 455 method, the surface structure of the generated paper substrate changed 411 significantly. With the simultaneous mixture and heating of the adhesive 384 370 agent (crosslinked starch) and PS particles, the surface structure of the resulting paper substrate became much coarser and there were more holes inside the structure, making it favorable 40 mL for the subsequent paper spray analy30 mL sis (Figure 2a). 25 mL When PS particles are coated onto 20 mL the surface of filter paper through ei10 mL ther the general coating method or 360 370 380 390 400 410 420 430 440 450 460 470 the hot coating method as described m/z above, the chemical composition of PS Figure 3. Comparison of the mass spectra of several drug compounds containing 10 μg mL-1 particles should be essentially the amisulpride (m/z 370), quetiapine (m/z 384), risperidone (m/z 411) and verapamil (m/z 455) same. The difference between them is using PS coated paper substrates for paper spray, in which PS were prepared in the presence that the starch undergoes gelatiniza- of various volumes of styrene (10, 20, 25, 30 and 40 mL) by fixing the amounts of BPO (1.0 g) tion which breaks down the intermo- and PVP (1.0 g) in 80 mL ethanol (Note: sample volume: 2 μL; spray solvent: 25 μL methanol; lecular bonds of starch molecules in applied voltage: 3.5 kV). the presence of water and heat, allow3.3 Mechanism of analyte desorption from PS-coated paper. ing the hydrogen bonding sites (the hydroxyl hydrogen and oxIn a recent study,58 we found that when PS was used as a maygen) to engage more water. During the preparation of PS terial for coating paper substrates, the stronger the adsorption coated paper, the gelatinized starch would participate in the interaction between PS particles and therapeutic drugs, the coating. The more the involvement of the starch, the stronger larger possible signal and better sensitivity of those drugs from the hydrogen-bond and/or van de Waals interactions between PS particle coated paper spray. Specifically, a higher sensitivity starch and analyte in the later paper spray analysis. Based on in paper spray analysis would be achieved when PS particles this, the difference in performance of the resulting papers with a stronger adsorption interaction were used as coating from the above three methods might also be related to the exmaterial, which is evident in Figures 3, S3 and S4. Extensive tent of involvement of the starch. To probe this assumption, study revealed that neither the high voltage and the paper subthe filtrates from those methods were collected and 100 μL of strate, nor the adhesive agent had significant impact on the 0.02% iodine solution was added into 1.4 mL of the collected desorption behavior.58 Our hypothesis is that this phenomesolution to observe the resulting chromogenic reaction. As non might originate from the unique desorption behavior of shown in Figure 2e, for all the filtrates, they became blue owtherapeutic drugs from the surface of PS-coated paper subing to the adsorption of iodine into the structure of the remainstrates. ing starch in the collected solution, indicating that a certain To get a visible observation on the desorption behavior in percentage of starch did not participate in the coating of PS paper spray, we studied the changes of methylene blue rangparticles. However, it was hard to distinguish the color differing from spotting to applying solvent, and then to paper spray ence visually. To resolve this issue, UV-vis spectra of the col(Figure S5a and b) on PS-coated paper substrate, in which PS lected filtrates were collected. As shown in Figure 2f, the peak was synthesized by the reaction between 25 mL styrene and intensity of the UV-vis spectra varies significantly with the 1.0 g BPO in the presence of 1.0 g PVP, and uncoated filter pacoating method. For example, the intensity of the peak around per. As shown in Figure S5a, after methylene blue solution is 192 nm from the hot coating method is around 4.3 and 1.2-fold spotted on the PS-coated paper, its color on the front side is higher than those from the general method and the cooling much lighter than that on the back side, suggesting that methcoating method, respectively. These results indicate that when ylene blue is prone to penetrate through the front coated PS the hot coating method was used for coating PS particles, a to the back side of the paper substrate, or that the methylene greater amount of starch leached into the filtrate, and a lesser blue loses visibility as it is absorbed among the PS particles. amount of the starch reagent remained at the surface of the Further investigation on the distributions of other sample maPS coated paper. In contrast to the hot coating method, the trices (e.g., blood sample) and analytes (e.g., therapeutic drugs) leached amounts of starch from the general method and the at the one-side PS coated paper confirms that after spotting a cooling method were relatively lower, and a larger amount of sample, a large percentage of both sample matrix and analytes starch was retained at the paper surface. This observation may of interest tend to be enriched at the PS coated side rather explain why the hot coating method produces PS-coated paper than penetrating through the paper substrate to another side with superior performance to those from the general method (Figure S6) presumably owing to the strong interactions beand the cooling method (Figure 2a). tween the tested sample and PS particles. After applying 25 μL


Page 5 of 9

105

A A A

A

A A

A

A

A

A A

A A

A

90 85 30

Diiodomethane

25 20

Polystyrene 10

15

20

25

30

35

Volume of Styrene (mL)

40

)

Water

95

Solvent

48

(c)

100

-1

Distribution Process

(b)

Surface Energy (mN m

(a)

Contact Angle (Degree)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(d)

44 40 36 32 28 10

15

20

25

30

35

40

Volume of Styrene (mL)

Figure 4. (a) Proposed schematic for the distribution process of analytes between PS particles and applied solvent; (b) Photograph of the water contact angle for a PS-coated glass slide at room temperature; (c) Correlation between the contact angles of water and diiodomethane at the PS-coated glass slides and the involved amount (10, 20, 25, 30 and 40 mL) of styrene in PS preparation by fixing the amounts of BPO (1.0 g) and PVP (1.0 g); (d) Correlation between the calculated surface energy of PS and the involved amount (10, 20, 25, 30 and 40 mL) of styrene in PS preparation using the Owens method.

methanol on the PS-coated paper, a higher percentage of solvent is floating on the front surface of PS coated paper relative to that at the back side. After paper spray, however, the color of methylene blue in the front side becomes much darker than that in the back side besides it travels in both sides of the paper, which is just contrary to its behavior after spotting. Compared to PS-coated paper (Figure S5a), the color of methylene blue on both sides of uncoated filter paper are comparable either after spotting or after paper spray (Figure S5b). These results indicate that after applying a spray solvent on PS-coated paper, the analytes of interest would be extracted in a facile manner out by solvent from the PS-coated paper substrate and then move to the tip of paper for spray along with the applied solvent. As discussed above, the desorption behaviors of tested drugs from the surfaces of PS-coated paper could be attributed to the unique partition coefficients of analytes between solvent and PS particles, and the latter is closely related to the surface energy of PS when the used solvent is fixed. In the current study, the used solvents (acetonitrile and methanol) have a surface tension in the range of 19.1 – 22.7 mN/m, which is lower than the surface energy of PS particles (above than 30 mN/m).59-64 The starch used for coating should increase this range due to its high surface energy (around 39 - 40 mN/m).65 As the solvent is applied to the PS-coated paper, it should be able to wet the PS surface. But compared with untreated filter paper substrate (with a very high surface energy), the extent of wetting is reduced, which reduces analyte redistribution and thus more efficient transfer from PS-coated paper as shown in Figure 4a. To get a better understanding on the correlation between the surface energy of PS particles and their performances in drug analysis (Figure 3), effort was made to achieve specific surface energy of various PS particles from the reaction between various volumes of styrene (10, 20, 25, 30 and 40 mL) and 1.0 g BPO in the presence of 1.0 g PVP. For these experiments, 0.2 g PS particles was first dispersed into 0.5 mL methanol followed by coating onto the surfaces of 25.4 mm x 76.2 mm slides similar to the conventional preparation of silicacoated glass slide used for thin layer chromatography. After drying in air, the prepared PS-coated slides were used for measurement of contact angles. According to the previous reports,60,61,63 water and diiodomethane are generally used as

test liquids to calculate the surface energy of PS via contact angles. However, in the present study it was hard to measure the contact angles of the above two test liquids at the surfaces of PS-coated glass slides using our experimental conditions due to the short retained time (less than 5 s). To address this issue, the PS coated slides were first baked at 180 oC for 30 min in an oven, and then the baked slides were used for later measurement (Figure 4b). Figure 4c shows the correlation between the contact angles of water and diiodomethane on various PS coated glass slides and the amount (10, 20, 25, 30 and 40 mL) of styrene in PS preparation by fixing the amounts of BPO (1.0 g) and PVP (1.0 g). For both liquids, with increase in the amount of styrene in PS preparation, the contact angle demonstrates first a decreasing trend followed by an increasing pattern, in which the PS involved with 25 mL styrene presents the smallest contact angle. These results have a contrary trend as to the desorption behaviors of different drugs at the PS-coated papers (Figure 3), suggesting that the surface properties of PS particles play a crucial role in determining the desorption performance of analytes on PS particles. To calculate the surface energy of those PS particles, the Owens method66 was employed. As shown in Figure 4d, with increase in the amount of styrene in PS preparation, the calculated surface energy demonstrates first a fast increasing trend followed by a gradual decreasing one, in which the PS from 25 mL of styrene illustrates the highest value (47.89 mN m-1). These results are in consistent with the above discussion on the desorption of studied drugs (Figure 3), revealing that the surface energy of PS particles is indeed related to the desorption behavior of analytes from the PS surfaces. They also suggest that when PS particles would be used as a coating material for preparation of paper substrate for paper spray, the one with a higher surface energy allows a more favorable MS sensitivity. 3.4 Quantitative analysis of therapeutic drugs in various biological matrices. Given the unique desorption behaviors, the PS microspheres obtained from 25 mL styrene and 1.0 g BPO in the presence of 1.0 g PVP were used as a coating material for preparation of PS-coated paper and quantitative analyses of a series of therapeutic drugs (e.g., amitriptyline, clozapine, quetiapine and risperidone) in various biological matrices such as whole blood, serum, and urine samples. In contrast to the performance of uncoated filter paper (Figure 5a), the MS/MS analysis of the protonated analyte (e.g., clozapine, m/z 327) from the PS-coated paper produced spectra which improved


Analytical Chemistry significantly in terms of signal-to-noise ratios (S/N, Figure 5b). To quantify the amount of compounds of interest in biological matrices, whole blood samples were chosen as an example and spiked with clozapine at different levels (0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 20, 50 and 100 ng mL-1) with 20 ng mL-1 D8-clozapine as internal standard. Selected reaction monitoring (SRM) mode (Table S1) was used for the quantitative analysis (transitions m/z 327 to 270 and m/z 335 to 275 for the analyte and internal standard). Figure 5c shows the dependence of the measured analyte-to-internal standard ratios (A/IS) as a function of the original analyte concentration in the whole blood samples. In contrast to uncoated filter paper, the data using PS coated paper demonstrated a good linear relationship with a linear regression coefficient R2 of 0.9973 covering four orders of magnitude (0.01 – 100 ng mL-1), and the analysis sensitivity improved 50-fold with a limit of quantitation of around 0.01 ng mL-1. A comparison has also been made on the analysis of a series of other compounds in whole blood, serum and urine samples (Tables 1 and S2 and Figure S7). An estimated

Relative Intensity

100

Uncoated Filter Paper

(a)

327

m/z 327

80 60 40 20 270 0

240 250 260 270 280 290 300 310 320 330 340

m/z

Relative Intensity

100

PS Coated Paper

(b)

327

m/z 327

80 270

60 40

lower limit of quantitation (LLOQs) in the range of 0.004 – 0.084 ng mL-1 was obtained for the PS coated paper, which is 10 – 546-fold better than those from uncoated filter paper. The repeatability and reproducibility of the PS-coated paper substrates for paper spray mass spectrometry were investigated in detail with 10 ng mL-1 of five drugs in dried blood spots (Table 2). The relative standard deviation (RSD) for each analysis in the run-to-run (n = 5), day-to-day (n = 5) and paper-to-paper (n = 5) were 0.79 – 2.53%, 1.31 – 2.90% and 1.50 – 3.78%, respectively, which illustrated the excellent repeatability and reproducibility of the PS coated paper substrates in paper spray analysis. Table 1. Estimated lower limit of quantitation (LLOQs) of analytes in whole blood, serum and urine samples using PS-coated paper substrates for paper spray mass spectrometry. LLOQs (ng mL-1) Uncoated paper PS coated paper Amitriptyline blood 9.439 0.055 serum 3.729 0.084 urine 1.122 0.064 Clozapine blood 3.330 0.033 serum 2.226 0.065 urine 0.136 0.013 Amisulpride blood 17.286 0.040 serum 20.449 0.048 urine 1.389 0.054 Quetiapine blood 2.728 0.005 serum 2.224 0.008 urine 0.122 0.004 Risperidone blood 3.193 0.077 serum 5.474 0.079 urine 0.471 0.047 Note: Estimated LLOQ was calculated through the equation LLOQ = 10 x sb/m, in which sb is the standard deviation of the response from the blank, and m is the slope of the calibration curve. Four replicates for each sample. Analyte

Matrix

20 0 240 250 260 270 280 290 300 310 320 330 340

m/z 1

10

Uncoated Filter Paper PS Coated Paper

(c)

Table 2. Analysis precision of 10 ng mL-1 different analytes in dried blood spots using PS-coated paper substrates for paper spray mass spectrometry.

0

10

A/IS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 9

Analytes

-1

10

-2

10

-3

10

-2

10

-1

10

0

10

1

2

10

10

Amitriptyline Clozapine Amisulpride Quetiapine Risperidone

run-to-run (n = 5) 1.11 0.79 1.59 1.82 0.87

RSD for each analysis (%) day-to-day paper-to-paper (n = 5) (n = 5) 2.90 3.78 2.64 3.21 2.51 1.50 2.88 3.66 1.31 2.47

-1

Concentration of Clozapine (ng mL )

Figure 5. (a)-(b) Paper spray tandem mass spectra of 2.0 μL of whole blood containing 0.5 ng mL -1 clozapine identified and quantified by the MS/MS transition m/z 327 → m/z 270 using (a) uncoated filter paper and (b) PS-coated paper as substrates; (c) Comparison of the quantitative analysis of whole blood spiked with clozapine (0.001 – 100 ng mL-1) and its isotopomer D8-clozapine (20 ng mL-1) between uncoated filter paper and PS coated paper (spray solvent: 25 μL of acetonitrile; applied voltage: 3.5 kV). Bars represent the standard deviation of analysis for four replicates. The linear regression coefficients R2 for uncoated filter paper and PS-coated paper were 0.9935 and 0.9973, respectively.

4. CONCLUSIONS In this study, uniform PS microspheres have been synthesized by a simple dispersion polymerization and employed as coating materials for paper spray in high-sensitivity analysis of therapeutic drugs in various biological matrices. As the PS particles were coated onto the surface of filter paper, the coating method was found to play a crucial role in determining the performance of the resulting paper substrate. After comparing the paper substrates from the general coating method, the cooling-coating method and the hot coating method, the results demonstrated that in contrast to the other two methods, the


Page 7 of 9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


paper from the hot coating method exhibited a superior capability in analysis of therapeutic drugs due to its porous structures at the surface and less involvement of adhesive agent (crosslinked starch). To gain insight into the desorption mechanism of target analytes on PS-coated paper substrates, methylene blue was used as a probe. After systematically investigating the desorption behaviors of methylene blue on a series of PS-coated papers and uncoated filter paper, the results revealed that after applying the spray solvent on PS-coated paper for paper spray, the analytes of interest would be readily extracted out by spray solvent and move to the tip of paper for spray along with the applied solvent. Although the interaction between methylene blue and PS particles is very strong, which does not facilitate its travel at the surface of PS particles, the desorption and diffusion of target analytes from the surface of PS particles to the applied solvent are favorable owing to the lower surface energy of PS than that of paper substrate. To our knowledge, this information has a profound implication on better understanding the desorption mechanism of the analytes of interest from PS particles during paper spray analysis. Meanwhile, the PS-coated paper substrates have been successfully used for analysis of different therapeutic drugs in whole blood, serum, and urine. In contrast to uncoated filter paper, the analysis sensitivity of paper spray has been improved 10 – 546-fold using PS-coated paper, and an estimated lower limit of quantitation (LLOQs) in the range of 0.004 – 0.084 ng mL-1 was obtained. Due to its excellent repeatability and reproducibility, we believe this work will promote the translation of MS technologies to clinical applications.

ASSOCIATED CONTENT Supporting Information Supporting Information Available: FT-IR spectrum of the obtained PS microspheres, effects of experimental conditions on the performances of the resulting paper substrates, comparison of the performance of PS particles from different conditions, and selected reaction monitoring (SRM) conditions. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (Z.Z.) or [email protected]. edu (D.A.).

Author Contributions ‡ These

authors contributed equally.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT We are grateful for funding from the National Natural Science Foundation of China (No. 21575112) and Shaanxi S&T Research Development Project of China (No. 2016GY-231).

REFERENCES (1) Ye, Z.; Meng, Q.; Lu, S. Appl. Surf. Sci. 2012, 258, 3624-3628. (2) Eckenrode, H. M.; Jen, S.-H.; Han, J.; Yeh, A.-G.; Dai, H.-L. J. Phys.

Chem. B 2005, 109, 4646-4653. (3) Romero-Cano, M. S.; Martín-Rodríguez, A.; de las Nieves, F. J. J. Colloid Interface Sci. 2000, 227, 322-328. (4) Romero-Cano, M. S.; Martín-Rodríguez, A.; de las Nieves, F. J. J. Colloid Interface Sci. 2000, 227, 329-333. (5) Geffroy, C.; Cohen Stuart, M. A.; Wong, K.; Cabane, B.; Bergeron, V. Langmuir 2000, 16, 6422-6430. (6) Turner, S. F.; Clarke, S. M.; Rennie, A. R.; Thirtle, P. N.; Cooke, D. J.; Li, Z. X.; Thomas, R. K. Langmuir 1999, 15, 1017-1023. (7) Colombié, D.; Landfester, K.; Sudol, E. D.; El-Aasser, M. S. J. Colloid Interface Sci. 1998, 202, 554-557. (8) Masini, J. C. J. Sep. Sci. 2016, 39, 1648-1655. (9) Qu, J.-B.; Huan, G.-S.; Chen, Y.-L.; Zhou, W.-Q.; Liu, J.-G.; Huang, F. ACS Appl. Mater. Inter. 2014, 6, 12752-12760. (10) Cao, X.; Kong, Q.; Cai, R.; Zhu, K.; Ye, X.; Chen, J.; Mo, W.; Wang, J. J. Sep. Sci. 2014, 37, 3677-3683. (11) Huang, X.; Zhang, S.; Schultz, G. A.; Henion, J. Anal. Chem. 2002, 74, 2336-2344. (12) Sacco, D.; Dellacherie, E. Anal. Chem. 1984, 56, 1521-1524. (13) Iskandarani, Z.; Pietrzyk, D. J. Anal. Chem. 1982, 54, 2427-2431. (14) Mori, S. Anal. Chem. 1978, 50, 745-748. (15) Mahfouz, M. G.; Killa, H. M.; Sheta, M. E.; Moustafa, A. H.; Tolba, A. A. J. Radioanal. Nucl. Chem. 2014, 301, 739-749. (16) León-González, M. E.; Pérez-Arribas, L. V. J. Chromatogr. A 2000, 902, 3-16. (17) Kauczor, H. W.; Meyer, A. Hydrometallurgy 1978, 3, 65-73. (18) Cortina, J. L.; Miralles, N.; Aguilar, M.; Sastre, A. M. Hydrometallurgy 1994, 36, 131-142. (19) Tolmacheva, V. V.; Apyari, V. V.; Furletov, A. A.; Dmitrienko, S. G.; Zolotov, Y. A. Talanta 2016, 152, 203-210. (20) Huang, J.; Deng, H.; Song, D.; Xu, H. Anal. Chim. Acta 2015, 878, 102-108. (21) Trautmann, M.; Lubahn, S.; Holdt, H.-J. React. Funct. Polym. 2014, 83, 84-97. (22) Yang, W. W.; Luo, G. S.; Gong, X. C. Sep. Purif. Technol. 2005, 43, 175-182. (23) Saitoh, T.; Suzuki, S.; Hiraide, M. J. Chromatogr. A 2005, 1097, 179-182. (24) Jonsson, S.; Borén, H. J. Chromatogr. A 2002, 963, 393-400. (25) Jara, S.; Lysebo, C.; Greibrokk, T.; Lundanes, E. Anal. Chim. Acta 2000, 407, 165-171. (26) Norde, W.; Gonzalez, F. G.; Haynes, C. A. Polym. Adv. Technol. 1995, 6, 518-525. (27) Tilton, R. D.; Robertson, C. R.; Gast, A. P. Langmuir 1991, 7, 2710-2718. (28) Boisson-Vidal, C.; Jozefonvicz, J.; Brash, J. L. J. Biomed. Mater. Res. 1991, 25, 67-84. (29) Fair, B. D.; Jamieson, A. M. J. Colloid Interface Sci. 1980, 77, 525-534. (30) Sofińska, K.; Adamczyk, Z.; Barbasz, J. Colloids Surf., B 2016, 137, 183-190. (31) Vesel, A.; Elersic, K. Appl. Surf. Sci. 2012, 258, 5558-5560. (32) Jain, R.; Forciniti, D. Langmuir 2012, 28, 15323-15335. (33) Browne, M. M.; Lubarsky, G. V.; Davidson, M. R.; Bradley, R. H. Surf. Sci. 2004, 553, 155-167. (34) Wang, J.; Buck, S. M.; Even, M. A.; Chen, Z. J. Am. Chem. Soc. 2002, 124, 13302-13305. (35) Zhang, Z.; Xu, W.; Manicke, N. E.; Cooks, R. G.; Ouyang, Z. Anal. Chem. 2012, 84, 931-938. (36) Wang, H.; Liu, J.; Cooks, R. G.; Ouyang, Z. Angew. Chem. Int. Ed. 2010, 49, 877-880. (37) Liu, J.; Wang, H.; Manicke, N. E.; Lin, J.-M.; Cooks, R. G.; Ouyang, Z. Anal. Chem. 2010, 82, 2463-2471.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(38) Lai, P.-H.; Chen, P.-C.; Liao, Y.-W.; Liu, J.-T.; Chen, C.-C.; Lin, C.H. Int. J. Mass spectrom. 2015, 375, 14-17. (39) Wang, Q.; Zheng, Y.; Zhang, X.; Han, X.; Wang, T.; Zhang, Z. Analyst 2015, 140, 8048 - 8056. (40) Zheng, Y.; Wang, Q.; Wang, X.; Chen, Y.; Wang, X.; Zhang, X.; Bai, Z.; Han, X.; Zhang, Z. Anal. Chem. 2016, 88, 7005-7013. (41) Han, F.; Yang, Y.; Ouyang, J.; Na, N. Analyst 2015, 140, 710-715. (42) Narayanan, R.; Sarkar, D.; Cooks, R. G.; Pradeep, T. Angew. Chem. Int. Ed. 2014, 53, 5936-5940. (43) Wang, X.; Zheng, Y.; Wang, T.; Xiong, X.; Fang, X.; Zhang, Z. Anal. Methods 2016, 8, 8004-8014. (44) Damon, D. E.; Davis, K. M.; Moreira, C. R.; Capone, P.; Cruttenden, R.; Badu-Tawiah, A. K. Anal. Chem. 2016, 88, 18781884. (45) Chen, S.; Wan, Q.; Badu-Tawiah, A. K. J. Am. Chem. Soc. 2016, 138, 6356-6359. (46) Colletes, T. C.; Garcia, P. T.; Campanha, R. B.; Abdelnur, P. V.; Romao, W.; Coltro, W. K. T.; Vaz, B. G. Analyst 2016, 141, 1707-1713. (47) Ugelstad, J.; Mórk, P. C.; Kaggerud, K. H.; Ellingsen, T.; Berge, A. Adv. Colloid Interface Sci. 1980, 13, 101-140. (48) Barrett, K. E. J. Brit. Polym. J. 1973, 5, 259-271. (49) Lok, K. P.; Ober, C. K. Can. J. Chem. 1985, 63, 209-216. (50) Zhang, X.; Shen, S.; Fan, L. Polym. Bull. 2008, 61, 19-26. (51) Paine, A. J.; Luymes, W.; McNulty, J. Macromolecules 1990, 23, 3104-3109. (52) Bamnolker, H.; Margel, S. J. Polym. Sci., Part A 1996, 34, 18571871. (53) Ha, S. T.; Park, O. O.; Im, S. H. Macromol. Res. 2010, 18, 935943. (54) Zheng, Y.; Zhang, X.; Yang, H.; Liu, X.; Zhang, X.; Wang, Q.;

Page 8 of 9

Zhang, Z. Anal. Methods 2015, 7, 5381-5386. (55) Wang, X.; Zheng, Y.; Wang, T.; Yang, H.; Bai, Z.; Zhang, Z. ChemistrySelect 2016, 1, 3297-3305. (56) Zheng, Y.; Zhang, X.; Bai, Z.; Zhang, Z. Rapid Commun. Mass Spectrom. 2016, 30, 217-225. (57) Gómez-Ríos, G. A.; Pawliszyn, J. Angew. Chem. Int. Ed. 2014, 53, 14503–14507. (58) Wang, T.; Zheng, Y.; Wang, X.; Wang, Q.; Ke, C.; Austin, D. E.; Han, X.; Zhang, Z. RSC Adv. 2017, 7, 19639-19644. (59) Liu, J.; Chen, L.; Cui, H.; Zhang, J.; Zhang, L.; Su, C.-Y. Chem. Soc. Rev. 2014, 43, 6011-6061. (60) Cho, J. S.; Han, S.; Kim, K. H.; Han, Y. G.; Lee, J. H.; lEE, C. S.; Sung, J. W.; Beag, Y. W.; Koh, S. K. In Adhesion Aspects of Thin Films, Mittal, K. L., Ed.; CRS Press: Boston, 2005, pp 105-121. (61) Fukuzawa, K. In International Adhesion Symposium, Mizumachi, H., Ed.; Gordon and Breach Science Publishers: Yokohama, Japan, 1994, pp 723-746. (62) Lee, L. H. J. Appl. Polym. Sci. 1968, 12, 719-730. (63) Wu, S. J. Polym. Sci. 1971, C34, 19-30. (64) "Solid surface energy data (SFE) for common polymers" available at: http://www.surface-tension.de/solid-surface-energy. htm (Accessed: 25 Feb 2017). (65) Lawton, J. W. Starch 1995, 47, 62-67. (66) Owens, D. K.; Wendt, R. C. J. Appl. Polym. Sci. 1969, 13, 17411747.


Page 9 of 9

For TOC Only 1

10

solvent

0

10

sample

IA/IIS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


-1

10

2

R = 0.9987

-2

10 HV

-3

10

-2

10

X2,000

-1

10

0

10

1

10

2

10

-1

10μm

Concentration of Clozapine (ng mL )


Sub-ppt Mass Spectrometric Detection of ... - ACS Publications

Recommend Documents