Toxin Screening in Phytoplankton: Detection and Quantitation Using MALDI Triple Quadrupole Mass Spectrometry
Bibliographic record
Abstract
The investigation of a MALDI triple quadrupole instrument for the analysis of spirolide toxins in phytoplankton samples is described in this study. A high-frequency (kHz) laser was employed for MALDI, generating a semicontinuous ion beam, thus taking advantage of the high duty cycle obtained in sensitive triple quadrupole MRM experiments. Initially, several experimental parameters such as type of organic matrix and concentration, solvent composition, and matrix-to-analyte ratio were optimized, and their impact on sensitivity and precision of the obtained ion currents for a reference spirolide, 13-desmethyl-C, was studied. In all quantitative experiments, excellent linearities in the concentration range between 0.01 and 1.75 microg/mL were obtained, with R2 values of 0.99 or higher. The average precision of the quantitative MALDI measurements was 7.4+/-2.4% RSD. No systematic errors were apparent with this method as shown by a direct comparison to an electrospray LC/MS/MS method. Most importantly, the MALDI technique was very fast; each sample spot was analyzed in less than 5 s as compared to several minutes with the electrospray assay. To demonstrate the potential of the MALDI triple quadrupole method, its application to quantitative analysis in several different phytoplankton samples was investigated, including crude extracts and samples from mass-triggered fractionation experiments. 13-Desmethyl spirolide C was successfully quantified in these complex samples at concentration levels from 0.05 to 90.4 microg/mL (prior to dilution to have samples fall within the dynamic range of the method) without extensive sample preparation steps. The versatility of the MALDI triple quadrupole method was also exhibited for the identification of unknown spirolide analogues. Through the use of dedicated linked scan functions such as precursor ion and neutral loss scans, several spirolide compounds were tentatively identified directly from the crude extract, without the usual time-consuming chromatographic preseparation steps. Moreover, high-quality CID spectra were obtained for low-abundant spirolides present in the phytoplankton samples.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".