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Effect of sample pH on solid phase extraction. Percentage spike recovery of urine samples spiked at various pHs (n=4)
| Analytes | Percentage Spike Recovery | ||
|---|---|---|---|
| pH=1 | pH=2 | pH=3 | |
| PPDA | 90.7 ± 5.7% | 61.3 ± 2.7% | 49.1 ± 1.2% |
| 6TDA | 100.4 ± 7.0% | 79.3 ± 2.9% | 85.6 ± 2.5% |
| 4TDA | 100.2 ± 8.4% | 77.3 ± 8.2% | 79.3 ± 3.9% |
| NDA | 100.4 ± 4.3% | 78.1 ± 6.0% | 81.6 ± 4.7% |
| MDA | 100.4 ± 5.0% | 96.4 ± 7.1% | 94.0 ± 4.7% |
