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Cited by 25Various Chemistry Research TopicsMicrowave-Assisted Synthesis and ApplicationsInnovative Microfluidic and Catalytic Techniques Innovation

Magnetic Stirring May Cause Irreproducible Results in Chemical Reactions

Open access
Cherepanova, Vera A., Gordeev, Evgeniy G., Ananikov, Valentine P.·2025·JACS Au
DOI 10.1021/jacsau.5c00412PMC PMC12381720
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Abstract

Magnetic stirrers, the most widely used and ubiquitous devices for performing chemical reactions in laboratory settings, may cause reproducibility problems. Reproducibility in a range of chemical processes can be affected by various factors, ranging from minor to significant effects, including yield, composition, and glassware contamination. In this study, we illustrate the reproducibility issues that may arise from the use of a magnetic stirrer for three fundamental types of chemical reactions. Significant differences were found in the reaction rates and sizes of the nanoparticles obtained via parallel synthesis with the same magnetic stirrer. For catalyst preparation, differences were observed in the morphology of the metal nanoparticles and the process rate depending on the location of the reaction vessel on the magnetic stirrer. In the case of organic synthesis examples, the conversions of parallel catalytic cross-coupling reactions in vessels standing beside each other on the same magnetic stirrer can be significantly different. The results of these experiments revealed the influence of previously unaccounted-for factors, and here, we suggest a control experiment to improve reproducibility. Given the ubiquitous use of magnetic stirrers in chemistry, biology, life sciences, and material sciences, the revealed reproducibility-affecting factor is of broad concern.

AI snapshot

Written from the paper’s full text.

TL;DR

Magnetic stirrers can produce position-dependent stirring that changes reaction rates, nanoparticle sizes/morphology, and catalytic conversions even for vessels on the same stirrer. The authors recommend final results be validated with a single vessel in an optimal stirring position and that stirrer/vessel/bar geometry be documented.

Key findings

  • In parallel Pd/C catalyst preparation, nanoparticle sizes ranged from 1.7 ± 0.8 nm to 4.2 ± 1.8 nm depending on vial position, and the carbon-material pillar height varied from 0.9 to 14 mm.
  • In Pd nanoparticle synthesis without carbon support, particle sizes differed significantly between adjacent vials, with reported sizes of 2.0 ± 0.4 nm vs 1.3 ± 0.3 nm.
  • In Suzuki–Miyaura cross-coupling, the central vial reached 45% conversion; the closest neighboring system was 15% lower, adjacent vials differed by more than 10%, and nonadjacent positions showed nearly 2-fold variations.
  • Stir bars stopped moving periodically at off-center positions; in the farthest system, the bar remained immobile for more than 35% of the observed duration after acceleration was factored out.

Methods

  • Custom 3D-printed vial stands fixed vials at defined horizontal and vertical positions on magnetic stirrers; experiments used 15 vials across three levels for Pd/C preparation and nine reactions for cross-coupling.
  • Three reaction types were studied: Pd/C catalyst preparation from Pd2dba3·CHCl3 with multiwalled carbon nanotubes, Pd nanoparticle formation in solution, and Pd/C-catalyzed Suzuki–Miyaura cross-coupling at 70 °C.
  • Outcomes were monitored by time-lapse photography, 1H NMR, TEM, SEM, and conversion measurements after 1 h; bar motion was captured on video and analyzed by superimposed frames.

Limitations

  • The paper states that different reactions may have different sensitivity to stirring, with homogeneous systems likely less sensitive than heterogeneous systems, but this is difficult to assume a priori.
  • The text makes evident that the study focuses on selected model reactions and specific stirrer/vessel/bar setups rather than a broad quantitative survey across laboratories or equipment.
  • The proposed remedy—a single-vessel control experiment in an optimal position—is a practical recommendation; the text does not report a multi-laboratory validation of that protocol.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1021/jacsau.5c00412

Cites

49 of 49 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

  • Findingown data

    Time-lapse images captured disparate rates of discoloration among the systems in Pd/C catalyst preparation.

    “The time-lapse images captured disparate rates of discoloration among the systems.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The solution color change correlates with the rate of Pd deposition from solution to the surface.
  • Findingown data

    Significant differences were found in the reaction rates and sizes of nanoparticles obtained via parallel synthesis with the same magnetic stirrer.

    “Significant differences were found in the reaction rates and sizes of the nanoparticles obtained via parallel synthesis with the same magnetic stirrer.”
    Quote in the paperSubstantial claim
  • Findingown data

    For catalyst preparation, differences were observed in the morphology of metal nanoparticles and the process rate depending on the location of the reaction vessel on the magnetic stirrer.

    “For catalyst preparation, differences were observed in the morphology of the metal nanoparticles and the process rate depending on the location of the reaction vessel on the magnetic stirrer.”
    Quote in the paperSubstantial claim
  • Findingown data

    The outcomes of the reactions were significantly influenced by unforeseen variables linked to magnetic stirring.

    “Astonishingly, we found that the outcomes of the reactions were significantly influenced by unforeseen variables linked to magnetic stirring.”
    Quote in the paperSubstantial claim
  • Findingown data

    In organic synthesis examples, conversions of parallel catalytic cross-coupling reactions in vessels standing beside each other on the same magnetic stirrer can be significantly different.

    “In the case of organic synthesis examples, the conversions of parallel catalytic cross-coupling reactions in vessels standing beside each other on the same magnetic stirrer can be significantly different.”
    Quote in the paperSubstantial claim
  • May combine two claims. 22
  • Classified as probably not a substantial claim. 14
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    In the authors' extensive research, they consistently observed discrepancies in the reproducibility of both yields and selectivity of catalytic organic synthesis reactions, as well as in the size and distribution of nanoparticles synthesized during catalyst preparation.

    “In our extensive research, we consistently observed discrepancies in the reproducibility of both the yields and selectivity of catalytic organic synthesis reactions, as well as in the size and distribution of nanoparticles synthesized during catalyst preparation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The outermost vials presented conversion rates comparable to those of the intermediate vials, an unexpected outcome given the greater distance between the outer and intermediate vials.

    “The outermost vials presented conversion rates comparable to those of the intermediate vials, an unexpected outcome given the greater distance between the outer and intermediate vials”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The largest particle size was observed in the system with the longest discoloration time; in the first two systems, the particle sizes coincided within the accuracy of the discoloration rate.

    “The largest particle size was observed in the system with the longest discoloration time; in the first two systems, the particle sizes coincided within the accuracy of the discoloration rate.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The stir bar's movement periodically ceases, and this cessation is especially prominent in the system farthest from the stirrer's center.

    “A critical observation from these images is the periodic cessation of bar movement, which is especially prominent in the system farthest from the stirrer’s center.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    A stationary stir bar results in a single static image.

    “whereas a stationary bar results in a single static image.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In time-lapse observations of the system of 15 vials, the solutions at positions 1a and 1b were the first to discolor, with position 1c following shortly after, while positions 3a and 2a were the last to discolor.

    “As a result of time-lapse observations of the system of 15 vials, the solutions at positions 1a and 1b were the first to discolor, with position 1c following shortly after. While the solutions in positions 3a and 2a were the last to discolor.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    If the reaction vessel is shifted from the stirrer center, the magnetic bar moving pattern changes, ceasing completely at a certain distance.

    “If the reaction vessel is shifted from the stirrer center, the magnetic bar moving pattern changes, ceasing completely at a certain distance.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At the end of the reaction, visual differences were observed in all vials; at 1b, 1c, 2b, and 2c, pillars of nanotubes were larger in volume than the initial volume of the loaded carbon material.

    “At the end of the reaction, visual differences were observed in all vials – at 1b, 1c, 2b, and 2c pillars of nanotubes, which were larger in volume than the initial volume of the loaded carbon material.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    At the lower level, the height of the columns is greater than that at the second level.

    “At the lower level, the height of the columns is greater than that at the second level.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Comparable but briefer halts in bar movement were noted in other systems.

    “Comparable but briefer halts were noted in other systems.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In catalytic cross-coupling reactions, conversion differences of more than 10% were observed among adjacent vials, with nearly 2-fold variations between nonadjacent positions.

    “In the case of catalytic cross-coupling reactions, conversion differences of more than 10% were observed among adjacent vials, with nearly 2-fold variations between nonadjacent positions”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    During synthesis of nanosized catalysts, differences were observed for metal nanoparticles (sizes ranging from 1.7 ± 0.8 nm to 4.2 ± 1.8 nm) and their synthesis rates, as well as differences in resulting support morphologies.

    “During the synthesis of nanosized catalysts, differences were observed for metal nanoparticles (with sizes ranging from 1.7 ± 0.8 nm to 4.2 ± 1.8 nm) and their synthesis rates, as well as differences in the resulting support morphologies.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Cracks and other surface deformities were present on the two vials used for Pd nanoparticle synthesis and Pd/C catalyst synthesis, spanning both macro- and microscales.

    “Our findings revealed the presence of cracks and other forms of surface deformities on the other two vials, spanning both macro- and microscales.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The movement patterns of stir bars can change when different bar types are used and when the vessel type is varied.

    “As an additional point to consider, the movement patterns of bars can change when different bar types are used, as well as when the vessel type is varied.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Given the ubiquitous use of magnetic stirrers in chemistry, biology, life sciences, and material sciences, the revealed reproducibility-affecting factor is of broad concern.

    “Given the ubiquitous use of magnetic stirrers in chemistry, biology, life sciences, and material sciences, the revealed reproducibility-affecting factor is of broad concern.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Magnetic stirrers are ubiquitous across chemistry, biology, life sciences, and material sciences.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    The nonreproducibility factors elucidated in the study could potentially influence a broader spectrum of reactions beyond the synthesis, catalysis, and nanoscience examples shown.

    “Such factors could potentially influence a broader spectrum of reactions beyond the synthesis, catalysis, and nanoscience examples shown here.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    In the absence of carbon material, no carbon material surface-related processes are observed, making the comparative reaction rate changes and dependencies clearer and demonstrating differences between positions.

    “Unlike systems with carbon material, in this case, no carbon material surface-related processes are observed, owing to which the comparative reaction rate changes and the dependencies themselves become clearer, demonstrating the differences between the positions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The duration of the experiment greatly increased due to a marked reduction in the complex decomposition rate, especially given the lack of surfaces other than the vial walls.

    “Consequently, the duration of the experiment greatly increased due to a marked reduction in the complex decomposition rate, especially given the lack of surfaces other than the vial walls.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    Grinding of carbon nanotubes may modify their catalytic activity by potentially increasing their specific surface area and possibly inducing metal leaching.

    “Grinding of carbon nanotubes may also modify their catalytic activity by potentially increasing their specific surface area and possibly inducing metal leaching.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    A custom stand was designed to allow nine simultaneous reactions and to ensure that all vial bottoms were in contact with the stirrer surface.

    “To accommodate multiple simultaneous reactions, a custom stand was designed, allowing for nine reactions. This design ensures that all of the vial bottoms are in contact with the stirrer surface”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The observed pillar heights might be related to the varying bar movements during stirring and subsequent grinding of the nanotube coils, resulting in a more dispersed arrangement.

    “The observed pillar heights might be related to the varying bar movements during stirring and subsequent grinding of the nanotube coils, resulting in a more dispersed arrangement.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    When a vessel is positioned away from the central axis of the stirrer, the magnetic bar tends to gravitate toward this axis, aligning in an inclined manner and leading to persistent contact with the base and walls of the vessel.

    “When a vessel is positioned away from the central axis of the stirrer, the magnetic bar tends to gravitate toward this axis. As a result, the bar aligns in an inclined manner, leading to persistent contact with not only the base of the vessel but also its walls.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The reactions were carried out in vials with new bars to avoid traces of catalytic metal.

    “As in the previous experiments, the reactions were carried out in vials with new bars to avoid traces of catalytic metal.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductown data

    NMR monitoring provided an independent, quantitative characterization of the differences revealed visually.

    “NMR monitoring provided an independent, quantitative characterization of the differences revealed visually.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    Different reactions may have different degrees of sensitivity to stirring; some reactions may not be noticeably sensitive, whereas others may be highly sensitive.

    “Of course, different reactions may have different degrees of sensitivity to stirring; some reactions may not be sensitive noticeably, whereas other reactions may be highly sensitive.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Homogeneous systems are likely to be less sensitive to stirring than heterogeneous systems.

    “In particular, homogeneous systems are likely to be less sensitive than heterogeneous systems.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The red zone on the stirrer surface, as well as a distance along the vertical axis, is most susceptible to possible irreproducibility.

    “At the same time, the red zone on the stirrer surface, as well as a distance along the vertical axis, is most susceptible to possible irreproducibility”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Interrupted rotation and chaotic bar motion are likely to compromise effective stirring, disrupting solution homogeneity and overall system consistency.

    “Such interrupted rotation and chaotic bar motion are likely to compromise effective stirring, disrupting solution homogeneity, and overall system consistency.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationreasoning

    In photochemical systems, the light penetration depth may create local reaction zones where mixing is critically important to achieve reproducible reactivity and to reduce the bleaching of dyes.

    “In photochemical systems, the light penetration depth may create local reaction zones where mixing is critically important to achieve reproducible reactivity and to reduce the bleaching of dyes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Erratic stirring mode delays reactions and introduces unpredictable kinetics, rendering several parameters random.

    “Consequently, this erratic stirring mode not only delays reactions but also introduces unpredictable kinetics, rendering several parameters random.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Many initially homogeneous systems may de facto develop into microheterogeneous or colloidal states (i.e., cocktail-type catalysis).

    “Many initially homogeneous systems may de facto develop into microheterogeneous or colloidal states (i.e., “cocktail”-type catalysis).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The spatial positioning of reaction vessels on a magnetic stirrer affects reaction kinetics and causes marked changes in results at both the microscale and nanoscale.

    “This, in turn, affects the reaction kinetics and has a cascading effect, causing marked changes in results at both the microscale and nanoscale.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The optimum position of the reaction vessel is in the center of the stirrer, as this is the only way to avoid damage to glassware and minimize contamination effects.

    “Despite the varying sensitivity of reactions to changes in stirring, the optimum position of the reaction vessel is in the center of the stirrer, as this is the only way to avoid damage to glassware and minimize contamination effects (impurities accumulate quickly in glassware defects and cannot be easily washed out).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Impurities accumulate quickly in glassware defects and cannot be easily washed out.
33 of 33

  • The paper relies on this without support.

    Magnetic stirrers are ubiquitous across chemistry, biology, life sciences, and material sciences.

    “Given the ubiquitous use of magnetic stirrers in chemistry, biology, life sciences, and material sciences”

  • The paper relies on this without support.

    Various locations of reaction vessels on a magnetic stirrer are common in regular chemistry research.

    “Considering regular research in chemistry, various locations of reaction vessels are quite common in laboratories”

  • The paper relies on this without support.

    The solution color change correlates with the rate of Pd deposition from solution to the surface.

    “This catalyst formation is easy to monitor because of the distinct correlation between the solution color change and the rate of Pd deposition from the solution to the surface.”

  • The paper relies on this without support.

    Full discoloration indicates that the reaction progressed to at least 95% completion.

    “Time-lapse photography tracked visual changes in the systems until full discoloration, indicating that the reaction progressed to at least 95% completion.”

  • The paper relies on this without support.

    Typical operational lifespans of glassware are far longer than a few tens of hours.

    “especially given that typical operational lifespans are far longer than a few tens of hours.”

  • The paper relies on this without support.

    Impurities accumulate quickly in glassware defects and cannot be easily washed out.

    “(impurities accumulate quickly in glassware defects and cannot be easily washed out)”

  • The paper relies on this without support.

    The density of metal particles lined up along lines of force is directly proportional to the magnitude of magnetic induction.

    “and their density is directly proportional to the magnitude of magnetic induction (Figure b–f).”

  • The paper relies on this without support.

    Modern experimental studies typically do not document all stirring parameters.

    “Notably, this is typically never done in modern experimental studies.”

  • The paper relies on this without support.

    The increase in carbon nanotube volume might be attributed to bar-induced breakage of the material.

    “considering that the increase in carbon nanotube volume might be attributed to bar-induced breakage of the material”
9 of 9

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Related

Authors
Cherepanova, V. A., Gordeev, E. G., & Ananikov, V. P.
Affiliations
Russian Academy of Sciences (RU)
Corresponding author
Ananikov, Valentine P.
ORCID
Venue
JACS Au
Publisher
American Chemical Society (ACS)
Published
2025-06-11
Volume
5
Issue
8
Pages
3789-3798
ISSN
2691-3704 (ISSN-L)
DOI
10.1021/jacsau.5c00412
PMC
PMC12381720
OpenAlex
W4411203905
Semantic Scholar
641492954ce617db61052260cf9b3729a6630ad4
Cited by
25
References
49
Citations by year
2026: 18 · 2025: 6
FWCI
10.63
Type
journal article
Language
en
Open access
Licence
Locations
  • JACS Au (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Physical Sciences › Chemistry › Physical and Theoretical Chemistry › Various Chemistry Research Topics
  • Physical Sciences › Chemistry › Organic Chemistry › Microwave-Assisted Synthesis and Applications
  • Physical Sciences › Engineering › Biomedical Engineering › Innovative Microfluidic and Catalytic Techniques Innovation
Keywords
magnetic stirrer, reproducibility, parallel synthesis, metal nanoparticles, catalyst preparation, nanoparticle morphology, cross-coupling reactions, organic synthesis, control experiments

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