DPD-based colorimetric quantification of free available chlorine (FAC) in floatation tank conditions
Bibliographic record
Abstract

 Background: Floatation tanks are quickly gaining traction as a form of relaxation, with numerous spas emerging in the Lower Mainland and beyond. The tanks are filled with a solution of magnesium sulphate, recycled between client uses. Thus, there exists a potential for microbiological contamination and subsequently, disease transmission. Health inspectors in BC may be involved the approval and inspection process for floatation tank spas; therefore, it is important to ensure that floatation tank environments are not a vehicle for disease. As a preventative measure, guidelines are in place for the halogenation of tank water at a level of 3-5 ppm free available chlorine (FAC). However, there is no standard method for the accurate and reliable quantification of FAC in high salinity environments. This study characterized the effect of high salinity on FAC readings from the HACH Pocket Colorimeter™, and derived a conversion factor to obtain an accurate reading for inspectors in the field. Methods: Floatation tank environments were simulated using USP-grade Epsom salts, Clorox™ bleach, and a hot water bath set at approximately 34°C (93°F). Assuming an initial concentration of 5.25% sodium hypochlorite, the bleach was serially diluted to obtain concentrations from 1-8 ppm. The final dilution step involved the addition of either 34°C water or an Epsom salt solution (MgSO4) at a specific density of 1.220 to create two solutions with identical amounts of bleach - one with and one without salt. The solutions were tested for chlorine two minutes later through the addition of DPD - a colorimetric dye that results with FAC - and measuring the colour intensity using the Pocket Colorimeter II. A percentage recovery was derived using the ratio between measured FAC with and without salt, Results: There was a statistically significant difference (p=0.05) between measured chlorine levels with and without salt as determined by a paired t-test. Further analysis via ANOVA and a post-hoc multiple comparison test (Scheffe's) indicated a dose-response relationship - increasing the amount of hypochlorite in an Epsom solution results in a statistically significant increase in measured FAC between the following groups: 1-2 ppm, 3-5 ppm, and 6-8 ppm of added hypochlorite. Linear regression revealed a strong correlation (0.97) between measured chlorine with and without salt. Conclusions: The HACH Pocket Colorimeter II™ can be used to estimate the amount of FAC in a floatation tank solution using a conversion factor of 0.79; to obtain an accurate measurement, divide the FAC reading in salt by 0.79
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.009 | 0.001 |
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 teacher head, 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".