Table 4. Optimizing Solid Phase Extraction to Improve Hormone Recovery.
Matrix Effects Study using 13C6 labeled thyroid hormones as surrogates, pre- and post- spiked samples at 1.00 ng/g in A, B and C. Recovery %, Matrix Effect % and Process Efficiency % are as defined in text.
| A. Evaluation of Evolute Express AX 60 mg cartridges using the manufacturer’s recommended method. Recovery was poor, <50% for all 3 hormone analytes. | |||
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| T3-13C6 | rT3-13C6 | T4-13C6 | |
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| Recovery % | 46 | 41 | 35 |
| Matrix Effects % (ME) | 99 | 110 | 112 |
| Process Efficiency (%) | 45 | 45 | 37 |
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| B. Recovery and process efficiency increases using Evolute Express AX 60 mg cartridges with an optimized wash step (2.0% formic acid in dichloromethane) and nitrogen evaporation in salinized glass tubes. | |||
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| T3-13C6 | rT3-13C6 | T4-13C6 | |
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| Recovery % | 62 | 58 | 63 |
| Matrix Effects % (ME) | 98 | 91 | 100 |
| Process Efficiency (%) | 70 | 62 | 73 |
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| C. Further enhancement of recovery using Evolute Express AX 60 mg cartridges with an optimized wash step (2.0% formic acid in dichloromethane) and nitrogen evaporation in low retention polypropylene tubes versus salinized glass tubes used in B. Recovery improved relative to conditions tallied in B. | |||
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| T3-13C6 | rT3-13C6 | T4-13C6 | |
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| Recovery % | 80 | 78 | 82 |
| Matrix Effects % (ME) | 98 | 91 | 100 |
| Process Efficiency (%) | 88 | 82 | 92 |