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| Method | S1 | S2 | S3 | S4 |
|---|---|---|---|---|
| Colorimetric | 9.9 ± 0.24 | 9.8 ± 0.16 | 10.2 ± 0.34 | 10.1 ± 0.12 |
| Ratiometric | 9.8 | 10.1 | 9.9 | 9.8 |
| Commercial pH meter | 9.8 | 9.8 | 9.8 | 9.8 |
