Organic Cation Distributions in the Residues of Levitated Droplets with Net Charge: Validity of the Partition Theory for Droplets Produced by an Electrospray
Bibliographic record
Abstract
In electrospray (ES) mass spectrometry experiments, the suppression of analyte ion signal intensity by a higher concentration of nonvolatile electrolyte is well documented. This phenomenon is, according to the partition theory, the result of competitive partitioning that favors electrolyte over analyte for occupancy in a surface volume that contains the net excess charge carried by droplets produced in an ES ion source. Reported here are the results of a set of experiments that were designed to learn of the final partition of cations in droplets with net charge by measurement of their distributions within the solid residues of those droplets. An electrodynamic balance was used to levitate droplets that contained Rhodamine 6G (R6G + ) plus a large molar excess of Na + Cl - until they dried to a solid residue. The residues, each typically 20 μm in cross section, were then deposited onto a plate and the distributions of R6G + were measured using confocal fluorescence microscopy and characterized using laser desorption/ionization time-of-flight mass spectrometry. Within the residues of droplets that had net negative charge, the R6G + was contained only within the core of the residue, indicating the net excess charge carried by the droplets was contained in the surface volume. Within the residues of droplets that had net positive charge, a small fraction of the R6G + precipitated on the residue's surface, but the majority of the R6G + precipitated in banded regions that were underneath a distinct 0.5−3-μm-thick surface volume that was identifiable because of its lower abundance of R6G + . These measurements of R6G + distributions within the residues of levitated droplets with net charge have provided literally solid evidence in support of the droplets having two phases, and that was a key postulate in the development of the partition theory.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".