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. 2021 Feb 12;14(2):147. doi: 10.3390/ph14020147

Table 2.

Selected relationships between skin permeability and liquid chromatographic descriptors.

Equation n R Reference
NP TLC log Kp = −1.318 (RM0)2 − 7.529 RM0 − 9.142 (dioxane-cyclohexane) 7
7		 0.98 [30]
log Kp = −0.762 (RM0)2 − 5.146 RM0 − 6.955 (THF-cyclohexane) 0.97
IAM HPLC log Kp= −10.19 + 1.77 log kIAM 10 0.94 [31]
log Ksc= 0.40 + 0.64 log kIAM 10 0.97
log Kp= −6.16 − 0.46 (log kIAM)2 + 1.54 log kIAM 14 0.80
log Kp = −6.09 + 1.05 log kIAM 14 0.88
log Kp= −5.154 + 1.443 log kIAM 32 0.51 [33]
log Ksc= 1.555 + 1.522 log kIAM 15 0.92
log Kp= −5.09 + 1.94 log kIAM 32 0.55 [34]
log Kp= −3.58 + 2.56 log kIAM − 1.12 V 32 0.86
log Kp= −2.419 Δlog kwIAM − 2.206 10 0.95 [32]
log Kp= −2.136 Δlog kwIAM + 0.037 log Pow − 2.373 10 0.94
log Kp= −2.182 Δlog kwIAM + 0.046 log kwIAM − 2.323 10 0.94
RP-18 log Kp = −4.76 + 1.44 log k − 1.16 V 27 0.91 [34]
log Kp = −5.728 + 1.636 log k (MSC18 column) 32 0.75 [33]
log Kp = −5.865 + 1.849 log k(RP-18 column) 32 0.73
log Ksc = 1.131 + 0.855 log k (MSC18 column) 15 0.87
log Ksc = 1.099 + 0.95 log k (RP-18 column) 15 0.85
BMC log Kp = −3.3 + 1.3 log kBMC − 0.008 MPt 42 0.91 [37]
log Kp = −2.24 + 1.83 log Pmw − 0.0123 Mw 22 0.91 [39]
Keratin log Kp = −6.558 + 1.920 log kIAM − 1.039 log kKERATIN 17 0.93 [36]

Where: Kp—skin permeability coefficient; Rf—retention factor in thin layer chromatography; RM = log (1/Rf − 1) and RM0 are obtained by extrapolation of RM values from a series of TLC experiments conducted for different concentrations φ of a modifier in mobile phases to zero concentration of the modifier, according to the equation: RM = RM0 + Sφ; Pmw—micelle-water partitioning coefficient; k—retention factor in column liquid chromatography; kIAM, kBMC, kKERATIN—retention factors in IAM, BMC and immobilized keratin chromatography, respectively; kwIAM—kIAM measured at or extrapolated to purely aqueous conditions; Δlog kwIAM—the difference between log kwIAM measured and predicted on the basis of log Pow; V—McGowan’s characteristic volume; Mw—molecular weight; MPt—melting point; Ksc—human skin-water partition coefficient.