On-Surface Alcohol Oxidation Monitored by Paper Spray Mass Spectrometry: The Role of Ruthenium as Catalyst

Article abstract of DOI:10.1021/jasms.1c00125

Paper spray ionization mass spectrometry (PS-MS) is employed herein as a convenient platform to investigate an on-surface catalytic process, that is, the oxidation of alcohols induced by ruthenium salts. The tag-charged benzyl alcohol 1 (m/z 166), used as a suitable prototype starting substrate, is quickly oxidized by tert-butyl hydroperoxide (TBHP) in an on-surface process catalyzed by ruthenium trichloride (RuCl3). The PS(+)-MS revealed the formation of products from the oxidation of alcohol 1. RuCl3 and TBHP played a crucial role in this process since when salts of other metals (platinum, palladium, and iron) and another oxidizing agent (hydrogen peroxide) are employed, no reaction is observed. Moreover, UV radiation and heating accelerate the on-surface alcohol 1 oxidation. Finally, an exciting possibility is to employ PS-MS to investigate similar organic catalytic reactions to accelerate them and detect unstable intermediates, indiscernible in the condensed phase.

Full text of DOI:10.1021/jasms.1c00125

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Research Article
On-Surface Alcohol Oxidation Monitored by Paper Spray Mass
Spectrometry: The Role of Ruthenium as Catalyst
̃
̃
Joao Victor Coelho Pimenta, Rodinei Augusti, and Adao Aparecido Sabino*
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ABSTRACT: Paper spray ionization mass spectrometry (PS-MS)
is employed herein as a convenient platform to investigate an on-
surface catalytic process, that is, the oxidation of alcohols induced
by ruthenium salts. The tag-charged benzyl alcohol 1 (m/z 166),
used as a suitable prototype starting substrate, is quickly oxidized
by tert-butyl hydroperoxide (TBHP) in an on-surface process
catalyzed by ruthenium trichloride (RuCl3). The PS(+)-MS
revealed the formation of products from the oxidation of alcohol
1. RuCl3 and TBHP played a crucial role in this process since when
salts of other metals (platinum, palladium, and iron) and another
oxidizing agent (hydrogen peroxide) are employed, no reaction is observed. Moreover, UV radiation and heating accelerate the on-
surface alcohol 1 oxidation. Finally, an exciting possibility is to employ PS-MS to investigate similar organic catalytic reactions to
accelerate them and detect unstable intermediates, indiscernible in the condensed phase.
KEYWORDS: alcohol oxidation, mass spectrometry, on-surface reactions, paper spray ionization, ruthenium catalyst
investigated via PS-MS are following pointed out: the
photodegradation of Methylene Blue induced by titanium
oxide,13 the accelerated on-surface haloform reaction,14 the
Claisen−Schmidt condensation,15 heterogeneous catalysis by
metallic nanoparticles,16 and the oxidation of alcohols to
aldehydes and carboxylic acids triggered by sodium hypo-
chlorite and ultraviolet radiation.17
Alcohol oxidation is a classical and relevant reaction in
organic chemistry since substances of high synthetic value,
namely aldehydes, ketones, and carboxylic acids, are the main
products. Classical methodologies employ pyridinium chlor-
ochromate (PCC)18 or CrO3/H2SO4 (Jones Reagent)19 to
trigger alcohol oxidation. However, novel and alternative
strategies promote milder and more selective reactions.20−24
The most successful approach involves using ruthenium
complexes as catalysts in the presence of an auxiliary oxidant,
usually oxygen or hydroperoxides.25
INTRODUCTION
■
Paper spray mass spectrometry (PS-MS) is one of the most
novel and innovative ambient ionization methods developed
by Cooks and co-workers in 2010.1 Paper spray ionization
relies on applying a high voltage at the base of a triangular
paper moistened with a polar solvent. A spray is then generated
at the opposite vertex releasing charged analytes to the gas
phase, which are attracted to the mass spectrometer entrance.
This ionization technique has several advantages, such as
smooth handling and minimal steps (if any) for sample
pretreatment, leading to a simple, fast, and inexpensive
analysis.1
Chemical reactions taking place in the condensed phase
have been increasingly investigated by mass spectrometry,
mainly by direct infusion atmospheric pressure techniques.
This type of study allows a better understanding of the
formation of intermediates and products, for which structures
can be proposed based on the data provided by mass
spectrometry (MS). For instance, appealing reports have
described the use of MS to investigated prototype organic
reactions, such as Heck,2 Suzuki,3 Stille,4 Baylis−Hillman,5
olefin metathesis.6
Two pathways have been proposed for alcohol oxidation
catalyzed by ruthenium complexes,26 the so-called oxometal or
peroxometal mechanisms. These two mechanisms consist of an
initial attack of alcohol or hydroperoxide, respectively, on an
active ruthenium species. The intermediate species produce an
The development of PS ionization has contributed to the
progress of different scientific areas. Several reports have
described the use of PS-MS to analyze drugs7,8 and
metabolites9,10 as well as to access the quality of foods11 and
materials.12 Some research groups have employed PS-MS to
investigate on-surface reactions, a recent and exciting mass
spectrometry application. Examples of on-surface processes
Received: April 7, 2021
Revised: June 29, 2021
Accepted: July 6, 2021
Published: July 19, 2021
© 2021 American Society for Mass
Spectrometry. Published by American
Chemical Society. All rights reserved.
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aldehyde, whereas the metal has its oxidation state regenerated.
According to a previous report, early transition metal ions with
d0 electronic configuration, such as Mo(VI) or W(VI), usually
favor the peroxometal pathway. Conversely, the oxometal
pathway usually prevails with late and first-row transition metal
ions, such as Cr(VI), Ru(VI) or Ru(VIII), and Os(VIII).26
This work aims at using PS-MS to evaluate on-surface
alcohol oxidation reactions catalyzed by Ru(III) salts. We
selected the tag-charged benzyl alcohol 1 as the prototype
reactant, tert-butyl hydroperoxide (TBHP) as the oxidant, and
RuCl3 as the catalyst. The use of the tag-charged benzyl
alcohol allows for easy monitoring of the reactant consumption
and the formation and distribution of intermediates and
products. We also evaluate the influence of some parameters
(time and the application of heat and UV radiation) on the
reaction course.
after 10 and 60 min. Heating tests were performed on two
papers, which were glued with small pieces of adhesive tape on
Petri dishes. The temperature was kept at approximately 80 °C
by exposing the dishes to a hot-air jet from a hairdryer. The
temperature was monitored using a thermometer placed close
to the papers. Hot air was removed after 10 and 60 min of
exposure. For these experiments (influence of UV radiation
and heating), the same amount and order of addition of
reagents were used, as indicated above.
For the experiments employing other metals as catalysts, 5
μL of a 0.15 mol·L−1 solution (prepared in acetonitrile) of each
metal salt (PdCl2, PtCl4K2, and FeCl3) and 5 μL of the TBHP
and alcohol 1 solution were added to triangle papers, as
previously described. Tests using H2O2 (hydrogen peroxide)
were conducted by adding to the papers 5 μL of a 0.15 mol·L−1
RuCl3 solution (prepared in acetonitrile), 5 μL of a 2.25 mol·
L−1 H2O2 solution (prepared in acetonitrile), and 5 μL of a
0.15 mol·L−1 alcohol 1 solution (prepared in acetonitrile/water
1:1 v/v), applied in this order. In both experiments, the PS-MS
essays were performed after reaction times of 0 and 120 min.
Condensed-phase reactions were performed in a 10 mL flask
by dissolving 15.6 mg (0.075 mmol) of RuCl3, 500 μL (0.75
mmol) of a 1.50 mol·L−1 TBHP solution (prepared in
acetonitrile), and 22.0 mg (0.075 mmol) of compound 1 in
a mixture of 300 μL of acetonitrile and 200 μL of water. The
reaction was kept under constant stirring at room temperature
and collected aliquots in 0, 10, 30, and 60 min for the PS-MS
analysis. These aliquots were then submitted to the PS-MS
analysis after different reaction times, as previously described.
EXPERIMENTAL SECTION
■
Instruments, Materials and Methods. NMR (nuclear
magnetic resonance) analyses were performed on a Bruker
instrument Advance DPX/200 (Billerica, MA). Solutions of all
compounds were prepared in CDCl3 or DMSO-d6 as the
solvent. Infrared (IR) spectra were obtained in KBr tablets on
a Spectrum RX I PerkinElmer spectrometer (Waltham, MA) in
a spectral window of 400−4000 cm−1. Melting points (mp)
were measured on a Gehaka PF 1500 instrument (Sao Paulo,
̃
Brazil). TLC (thin layer chromatography) was carried out with
Macherey-Nagelsilica gel 60 F254 on aluminum sheets. After
chromatographic runs, the silica plates were developed using
ultraviolet light or exposure to chemical reagents, i.e., iodine
vapors or spray of a potassium permanganate solution. PS-MS
(paper spray mass spectrometry) experiments were conducted
on a Thermo LCQ-Fleet mass spectrometer (ThermoScien-
tific, San Jose, USA) in positive-ion mode. The instrumental
conditions were as follows: voltage applied to the paper, 5 kV;
capillary temperature, 275 ◦C; capillary voltage, 8 V; tube lens
voltage, 70 V. Full scan mass spectra were acquired over a 50−
1000 m/z range. The triangular paper’s tip was placed in front
of the mass spectrometer inlet at a distance of approximately 5
mm. Then 20 μL of acetonitrile was added, and, through a
metal clip, a high voltage (5 kV) was applied to the paper base.
HPLC grade acetonitrile was purchased from JT Baker
Chemicals. Ruthenium(III) chloride hydrate (RuCl3·xH2O),
tert-butyl hydroperoxide (TBHP) (solution in decane at ∼5.5
mol·L−1), hydrogen peroxide (solution at 35% v/v), and
chloride salts of palladium, platinum, and iron were purchased
from Sigma-Aldrich (Milwaukee, WI). Chromatographic paper
grade 3 MM CHR, purchased from Whatman International
Ltd. (Maidstone, Kent, England), was cut with a scissor to
manufacture triangular papers in the dimensions of 1.0 × 1.5 ×
1.5 cm.
RESULTS AND DISCUSSION
■
On-Surface Alcohol Oxidation Catalyzed by RuCl3.
According to previous (unpublished) studies by our research
group, in the presence of ruthenium complexes, benzyl
alcohols are oxidized to aldehydes in solution in good yields.
To verify whether such reaction could occur directly on a
paper surface, the tag-charged benzyl alcohol 1 was chosen as a
prototype and convenient (for MS detection) starting reactant.
Ruthenium trichloride (RuCl3) and TBHP were selected as the
oxidizing agent and catalyst, respectively (Scheme 1). These
experiments were conducted using an identical molar
proportion for alcohol 1, RuCl3, and TBHP.
Scheme 1. On-Surface Oxidation of the Tag-Charged
Alcohol 1 Yielding Aldehyde 2 in the Presence of TBHP and
RuCl3
General Procedure. Oxidation tests were conducted by
dropping 5 μL of a 0.15 mol·L−1 RuCl3 solution (prepared in
acetonitrile), 5 μL of a 1.50 mol·L−1TBHP solution (prepared
in acetonitrile), and 5 μL of a 0.15 mol·L−1 alcohol 1 solution
(prepared in acetonitrile/water 1:1 v/v), applied in this order,
at the same spot of triangular papers (1 × 1.5 × 1.5 cm). The
PS-MS analysis were performed after reaction times of 0, 10,
30, and 60 min.
Tests with UV radiation were conducted by placing two
papers inside a chamber equipped with a UV Lamp (Techlux,
6 W, Belo Horizonte, Brazil). The papers were kept 20 cm
away from the UV lamp and removed from inside the chamber
A picture of the triangle papers with the reagents (RuCl3,
TBHP, and alcohol 1) of the beginning and after a contact
time of 60 min clearly shows a color change (Figure 1),
indicating the occurrence of a reaction.
Figure 2 shows the PS(+)-MS collected at different times (0,
10, 30, and 60 min) of these on-surface reactions. Note that
there are clear changes in the mass spectra profiles, indicating
that the reaction is proceeding on the paper surface rather than
occurring inside the spray microdroplets. If that were the case,
one would expect to obtain identical mass spectra, regardless of
the acquisition time. Under these conditions, the tag-charged
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Research Article
postulated to suggest the formation of carboxylic acid 3. In the
first one, water (used as a solvent in preparing the solutions)
reacts with aldehyde 2 to form a hydrate (of m/z 182, not
detected in mass spectra displayed in Figure 2) which is later
oxidized to yield carboxylic acid 3. When water was replaced
by dimethyl sulfoxide (DMSO) to prepare the starting
solutions, the final result was identical, indicating that water
does not influence the conversion of aldehyde 2 to carboxylic
acid 3. The second hypothesis stands on the direct conversion
of aldehyde 2 to carboxylic acid 3 under the paper surface’s
oxidative conditions. We verified this last possibility by
reacting aldehyde 2 with TBHP and RuCl3. The PS(+)-MS
(not shown) demonstrated this hypothesis since the carboxylic
acid 3 was formed under these conditions indeed.
Figure 1. Pictures of the triangle papers containing the reagents
(RuCl3, TBHP, and alcohol 1 taken at different times: 0 min (A) and
60 min (B).
The dissociation spectrum (Figure S7) of the ion of m/z 236
showed the dominating presence of a product-ion of m/z 180
arising from a loss of 56 Da. A possible structure for this
product (ester 4) is proposed, as shown in Figure 3. Finally,
the mechanism for the fragmentation of ester 4, displayed in
Figure 3, is consistent with its suggested structure.
A previous study reports tert-butyl esters’ synthesis by
reacting aldehydes and tert-butyl peroxide catalyzed by copper
salts via a radical mechanism.27 This information suggests that
RuCl3 decomposes TBHP to generate two distinct radicals, i.e.,
tert-butyl hydroxyl and hydroxyl. These radicals abstract the
hydrogen of the carbonyl group of aldehyde 2 to produce both
ester 4 and carboxylic acid 3. Figure 4 schematically represents
these pathways.
benzyl alcohol 1, of m/z 166, is continuously oxidized to the
aldehyde 2 of m/z 164. Note also that for longer reaction times
(30 and 60 min, Figure 2C,D, respectively), alcohol 1 has
almost completely disappeared. In contrast, other five ions of
m/z 164 (aldehyde 2), m/z 180 (carboxylic acid 3), m/z 236
(ester 4), m/z 252 (perester 5), and m/z 254 (hemiperacetal
6) became prevalent. Control experiments with all possible
reagents combinations (alcohol 1, TBHP, and RuCl3) were
also conducted, but none of such products were detected.
Additional experiments with a different proportion of RuCl3 (5
mol %) were conducted, but similar results to those arising
from the reactions conducted under equimolar proportions
were obtained (Figures S50 and S51).
The main channel for the dissociation of the ion of m/z 254
(Figure S9) consists of the loss of tert-butyl alcohol (74 Da) to
yield the product ion of m/z 180 (carboxylic acid 3). These
data led us to suggest the structure of hemiperacetal 6 (Scheme
2) for this product. Its formation probably occurs via a simple
addition of the oxygen atom of TBHP to the carbon of the
carbonyl group of aldehyde 2. The literature has reported
analogous hemiperacetals synthesis by the reaction of several
aldehydes with TBHP.28 Moreover, note that the fragmenta-
tion profile for the ion of m/z 254 is entirely consistent with
The structures proposed for them are displayed in Scheme 2,
whereas plausible routes for their formation are exposed later
in this paper.
The fragmentation profile (Figure S5) of the ion of m/z 164
(aldehyde 2) showed the loss of 15 Da (methyl group),
consistent with the proposed structure. The ion of m/z 180
probably refers to carboxylic acid 3, presumably formed from
later oxidation of aldehyde 2. Its fragmentation spectrum
(Figure S6) is consistent with the proposed structure as it also
displays a methyl group loss (15 Da). Two hypotheses were
Figure 2. PS(+)-MS of the on-surface reaction between tag-charged benzyl alcohol 1 with tert-butyl hydroperoxide (TBHP) catalyzed by RuCl3 at
different times: 0 (A), 10 (B), 30 (C), and 60 (D) min.
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Scheme 2. Schematic Representation Showing Product Formation from the On-Surface Oxidation of the Tag-Charged Benzyl
Alcohol by the Oxidant tert-Butyl Hydroperoxide (TBHP) and RuCl3
Figure 5. Proposed mechanism for the fragmentation of hemi-
Figure 3. Proposed fragmentation pathway of ester 4 (m/z 236)
peracetal 6 (m/z 254) yielding carboxylic acid 3 of m/z 180.
showing the loss of 2-methylpropene.
the structure proposed for hemiperacetal 6, as demonstrated in
Figure 5.
from the dissociation of carboxylic acid 3 via the loss of CO
and CO2 + H•, respectively. However, these two ions were not
detected as product ions of carboxylic acid 3, as previously
discussed.
The ion of m/z 252 has 2 Da less (one H2 molecule) than
the hemiperacetal 6. This result strongly indicates that
hemiperacetal 6 undergoes oxidation to yield perester 5
(Scheme 2). Its mass-selection and dissociation (Figure S8)
yielded three primary product-ions of m/z 180 (carboxylic acid
3), m/z 152, and m/z 135. Figure 6 displays a mechanism that
explains these three product ions’ formation from the
fragmentation of 5 (m/z 252). Therefore, the product ion of
m/z 180 (carboxylic acid 3) probably arises from 5 via a
hydrogen rearrangement followed by the loss of 2,2-
dimethyloxirane (72 Da). Additionally, 5 releases 2,2-
dimethyloxirane (72 Da) and CO to yield the product ion of
m/z 152, whereas 5 loses CO (28 Da), 2,2-dimethyloxirane
(72 Da), and hydroxyl radical (17 Da) to produce the product
ion of m/z 135 (an open shell species). Note that these two
former product ions (m/z 152 and m/z 135) could also result
Recent reports have described the synthesis of peresters,
starting from acyl chlorides and TBHP,29 or aldehyde and
TBHP, via iodide catalysis.30 The presence of iodide as the
counterion in alcohol 1 could, therefore, be the primary cause
of the formation of perester 5. To test this hypothesis, we
added a small amount of silver nitrate to an aliquot of aldehyde
2 solution and submitted the mixture to centrifugation. We
then collected the supernatant and added it to the paper
surface along with RuCl3 and TBHP solutions. However, we
observed the attainment of quite similar mass spectra (not
shown) as those displayed in Figure 2. These results indicate,
therefore, that iodide has no role in the oxidation of alcohol 1.
Rather than that, the oxidation of hemiperacetal 6 catalyzed by
RuCl3 is the probable origin of perester 5. We further tested
Figure 4. Proposed mechanism for the formation of carboxylic acid 3 and ester 4 by the interaction of hydroxyl and tert-butyl hydroxyl radicals with
aldehyde 2.27
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Figure 6. Proposed mechanism for the fragmentation of perester 5 (m/z 252).
this hypothesis by reacting aldehyde 2 with TBHP in the
absence of RuCl3. The results showed the exclusive formation
of hemiperacetal 6, with no detection of perester 5.
conducted. Nevertheless, alcohol 1 remained unreactive, even
after 120 min. A possible explanation for such a finding is that
ruthenium species catalyze the hydrogen peroxide decom-
position26 (H2O2 → H2O + 1/2 O2) very quickly, hampering
its function as an oxidizer (displayed as Figures S42−S45).
Comparison with Reactions in the Condensed Phase.
The results between the on-surface and condensed-phase
reactions were compared. Aliquots of condensed-phase
reactions, conducted under ambient temperature and reflux,
were collected after 24 h and submitted to PS-MS analysis.
Compared with the initial solution, the ion of m/z 166
(alcohol 1) remained almost unaltered, and none of the ions
previously described were noticed, except for the ion of m/z
164 that was detected at low intensity in the condensed-phase
reaction conducted under reflux (displayed as Figures S46−
S49). Therefore, these findings indicate that the on-surface
process is much more effective compared to the condensed-
phase reaction. This is a promising result as noticeable
improvements in rates and yields of catalytic reactions can be
promptly achieved and quickly evaluated by PS-MS.
Structure Elucidation: Comparison with the Frag-
mentation Profiles of Authentic Ions. Compounds 2−4
were synthesized and characterized by melting point, NMR,
and IR spectroscopy (see Figures S10−S33 for further details).
No success was achieved in synthesizing compounds 5 and 6,
probably due to their high instability. Solutions of the
authentic 2−4 were then prepared and deposited on the
paper triangle. These ions were then mass-selected and
dissociated. The results indicated an identical profile to the
products generated during the on-surface processes, confirming
their proposed structures.
Thus, these results reveal that RuCl3 acts effectively as a
catalyst in the three oxidations described, namely alcohol 1 to
aldehyde 2, aldehyde 2 to carboxylic acid 3, and hemiperacetal
6 to perester 5. RuCl3 also play a crucial role in the formation
of ester 4 from aldehyde 3 as it induces the decomposition of
TBHP to yield tert-butyl hydroxyl and hydroxyl radicals. An
on-surface reaction with 3 as the starting reactant was
evaluated to check whether such a compound could directly
yield products 4 and 5. However, none of them was detected
(mass spectrum not shown), indicating that aldehyde 2 is
indeed the primary source of all other products (3 − 6). Since
aldehyde 2 (m/z 164) is the product that gives rise to the
others, it is not surprising that the ion of m/z 164 is not the
most intense in the PS-(+)-MS (Figure 2), especially in those
mass spectra acquired after longer reactions times. Moreover,
compounds as peresters and hemiperacetals are unstable in the
condensed phase, undergoing quick decomposition. However,
by applying the PS-MS platform, these products were readily
detectable.
Influence of UV Irradiation and Heating on the On-
Surface Reactions. To check whether UV radiation and
heating could affect products’ formation and distribution, we
irradiated (with a UV radiation source) or applied a hot air jet
(from a hairdryer) on the paper surface. The resulting PS(+)-
MS (displayed as Figures S34−S41) shows that whereas
identical ions (2−6) were formed under these conditions, the
UV radiation and heating seem to accelerate the on-surface
alcohol 1 oxidation. For instance, the PS(+)-MS shows that
alcohol 1 (m/z 166) is more intense in the reaction conducted
under ordinary conditions when compared with the PS(+)-MS
of the on-surface reactions submitted to UV irradiation or
heating.
Influence of Other Metals and Oxidants on the On-
Surface Oxidation of Alcohol 1. Other transition metals
were also tested as catalysts for the on-surface oxidation of
alcohol 1. The following metals were evaluated: platinum,20
palladium,21 and iron.22 Solutions of these metals were
prepared using conditions identical to those employed for
RuCl3 reaction. The solutions were applied on the paper
surface along with alcohol 1 and TBHP using in all cases the
same molar ratio (for more details, see the Experimental
Section). However, none of these metals presented detectable
catalytic activity for alcohol 1 oxidation, even after a reaction
time as long as 120 min. A similar study replacing TBHP with
hydrogen peroxide (at the same molar concentration) was
CONCLUSION
■
We employed paper spray ionization mass spectrometry to
monitor the on-surface oxidation of the tag-charged benzyl
alcohol 1 by the oxidant tert-butyl hydroperoxide (TBHP) and
catalyzed by RuCl3. The PS-MS application allowed for
detecting several oxidation products formed under these
conditions, including some unstable species. Moreover,
ruthenium showed to be an excellent catalyst to induce
alcohol oxidation, even under the unusual conditions
employed herein. Besides those impressive results, PS-MS
allows for the economy of reagents and supplies via fast,
simple, and reproducible experiments. The present study is
also a helpful example demonstrating that PS-MS can be easily
employed to investigate catalytic processes. The same
approach can be employed to investigate other similar organic
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Research Article
(8) Shi, R. Z.; El Gierari, E. T. M.; Manicke, N. E.; Faix, J. D. Rapid
Measurement of Tacrolimus in Whole Blood by Paper Spray-Tandem
Mass Spectrometry (PS-MS/MS). Clin. Chim. Acta 2015, 441, 99−
104.
reactions, with evident advantages over the traditional
condensed-phase processes. This appealing possibility is
underway in our laboratory.
(9) Wang, H.; Ren, Y.; McLuckey, M. N.; Manicke, N. E.; Park, J.;
Zheng, L.; Shi, R.; Graham Cooks, R.; Ouyang, Z. Direct Quantitative
Analysis of Nicotine Alkaloids from Biofluid Samples Using Paper
Spray Mass Spectrometry. Anal. Chem. 2013, 85 (23), 11540−11544.
(10) Huang, Y. C.; Chung, H. H.; Dutkiewicz, E. P.; Chen, C. L.;
Hsieh, H. Y.; Chen, B. R.; Wang, M. Y.; Hsu, C. C. Predicting Breast
Cancer by Paper Spray Ion Mobility Spectrometry Mass Spectrometry
and Machine Learning. Anal. Chem. 2020, 92 (2), 1653−1657.
(11) Moura, A. C. M.; Lago, I. N.; Cardoso, C. F.; dos Reis
Nascimento, A.; Pereira, I.; Vaz, B. G. Rapid Monitoring of Pesticides
in Tomatoes (Solanum Lycopersicum L.) during Pre-Harvest
Intervals by Paper Spray Ionization Mass Spectrometry. Food Chem.
2020, 310, 125938.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/jasms.1c00125.
■
sı
Synthesis and characterization data, PS(+)-MS spectra
(PDF)
AUTHOR INFORMATION
Corresponding Author
̃
Adao Aparecido Sabino − Department of Chemistry, Federal
University of Minas Gerais, Belo Horizonte 31270-901 MG,
Brazil; orcid.org/0000-0003-1265-7694;
Email: aasabino@gmail.com
■
(12) Guo, T.; Zhang, Z.; Yannell, K. E.; Dong, Y.; Cooks, R. G.
Paper Spray Ionization Mass Spectrometry for Rapid Quantification
of Illegal Beverage Dyes. Anal. Methods 2017, 9 (44), 6273−6279.
(13) Resende, S. F.; Teodoro, J. A. R.; Binatti, I.; Gouveia, R. L.;
Oliveira, B. S.; Augusti, R. On-Surface Photocatalytic Degradation of
Methylene Blue: In Situ Monitoring by Paper Spray Ionization Mass
Spectrometry. Int. J. Mass Spectrom. 2017, 418, 107−111.
(14) Bain, R. M.; Pulliam, C. J.; Raab, S. A.; Cooks, R. G. Chemical
Synthesis Accelerated by Paper Spray: The Haloform Reaction. J.
Chem. Educ. 2016, 93 (2), 340−344.
Authors
Joa
̃
o Victor Coelho Pimenta − Department of Chemistry,
Federal University of Minas Gerais, Belo Horizonte 31270-
901 MG, Brazil
Rodinei Augusti − Department of Chemistry, Federal
University of Minas Gerais, Belo Horizonte 31270-901 MG,
Brazil; orcid.org/0000-0002-9448-9518
(15) Bain, R. M.; Pulliam, C. J.; Yan, X.; Moore, K. F.; Muller, T.;
̈
Cooks, R. G. Mass Spectrometry in Organic Synthesis: Claisen-
Schmidt Base-Catalyzed Condensation and Hammett Correlation of
Substituent Effects. J. Chem. Educ. 2014, 91 (11), 1985−1989.
(16) Banerjee, S.; Basheer, C.; Zare, R. N. A Study of Heterogeneous
Catalysis by Nanoparticle-Embedded Paper-Spray Ionization Mass
Spectrometry. Angew. Chem., Int. Ed. 2016, 55 (41), 12807−12811.
(17) Zhu, X.; Zhang, W.; Lin, Q.; Ye, M.; Xue, L.; Liu, J.; Wang, Y.;
Cheng, H. Direct Microdroplet Synthesis of Carboxylic Acids from
Alcohols by Preparative Paper Spray Ionization without Phase
Transfer Catalysts. ACS Sustainable Chem. Eng. 2019, 7 (7), 6486−
6491.
Complete contact information is available at:
https://pubs.acs.org/10.1021/jasms.1c00125
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
The authors acknowledge financial support by the Coordena-
■
c
̧
a
̃
o de Aperfeic
(CAPES, Brazil), Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq, Brazil), and Fundaca de
̧
oamento de Pessoal de Nível Superior
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