Table 1 Tacrolimus-related compounds: reported and observed relative retention time (RRt) with different HPLC methods and the Pharmacopoeial Forum (PF)-established acceptance criteria
From: Evaluation, synthesis and characterization of tacrolimus impurities
Method A | Method B | ‘In-house’ method | |||||
|---|---|---|---|---|---|---|---|
RR t | RR t | RR t | |||||
Compound | Description | The US PF | Found | Acceptance criteria NMT (%) | The US PF | Found | |
1 | Tacrolimus | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | |
2 | Tautomer I (tacrolimus open ringa) | 1.3 | 1.42 | 0.5 | 0.52 | 0.51 | 0.54 |
3 | Tautomer II (tacrolimus 19-epimera) | 1.1 | 1.14 | 1.0 | 0.63 | 0.65 | 0.75 |
4 | Tacrolimus metacrilatea (aldehyde derivative) | 0.55 | Not found | 0.2 | Not reported | Not found | Not found |
5 | Tacrolimus dienea (23,24- anhydro tacrolimus) | 0.79 | 0.75 | 0.2 | Not reported | 1.68 | 1.73 |
6 | Tacrolimus-related compound Aa (ascomycinb) | 0.96 | 0.95 | —c | 0.87 | 0.88 | 0.87 |
7 | Impurity 1a (unspecified impurity) tacrolimus 8-propyl analogb | 0.96 | 0.87 | 0.2 | 1.33 | 1.32 | 1.20 |
