1. Non-Invasive Method for Quantitative Evaluation of Exogenous Compound Deposition on Skin 
Georgios N. Stamatas, Jeff Wu, Nikiforos Kollias 
Journal of Investigative Dermatology 
Volume 118, Issue 2, Pages (February 2002)
DOI: /j x x
Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

2. Figure 1 Schematic diagram of the experimental setup.
Journal of Investigative Dermatology  , DOI: ( /j x x)
Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

3. Figure 2
A series of 31 excitation scans on volar forearm skin before and after treatment with 10 µg per cm2 salicylic acid. (A) Before treatment; (B) after treatment. The emission wavelength was increased for every successive scan by 10 nm starting at 260 nm and finishing at 560 nm. The two plots are shown in the same scale to demonstrate the increase of the fluorescence signal at 290 nm excitation. Using this excitation and measuring at 420 nm emission the interference from skin native fluorescence is minimal.
Journal of Investigative Dermatology  , DOI: ( /j x x)
Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

4. Figure 3
Schematic model of the optical phenomena occurring when excitation radiation is delivered to skin with a superficially deposited fluorescent compound.
Journal of Investigative Dermatology  , DOI: ( /j x x)
Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

5. Figure 4
The relation between corrected fluorescence measurements and surface concentration of salicylic acid for moderate and low concentrations. (A) Moderate concentration; (B) low concentration. Data show average values of measurements acquired from 10 volunteers with skin types ranging from I to IV. Error bars indicate standard deviations. The solid lines represent the fitted power (C = 0.21 × (F )1.68) and linear (C = 0.53 × (F )) curves for moderate and for low concentrations, respectively. Note that the corrected fluorescence value at zero concentration is not zero (0.09 a.u.). This value corresponds to native skin fluorescence.
Journal of Investigative Dermatology  , DOI: ( /j x x)
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6. Figure 5
Excitation spectra using a quartz spacer. (A) The emission collection angle is being enhanced using a quartz spacer between the probe and the skin, resulting in a larger emission collection area. (B) A series of 31 excitation scans on volar forearm skin treated with 10 µg per cm2 salicylic acid with a quartz spacer placed between the probe and the skin. The emission wavelength was increased for every successive scan by 10 nm starting at 260 nm and finishing at 560 nm.
Journal of Investigative Dermatology  , DOI: ( /j x x)
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7. Figure 6
Fluorescence measurements of salicylic acid on skin following tape stripping. The data show average values of measurements from four sites on two volunteers. Error bars indicate the standard error of the mean. The fitted line is given by F = 3.57 × exp(-0.14n).
Journal of Investigative Dermatology  , DOI: ( /j x x)
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8. Figure 7
Salicylic acid concentration on skin decreases exponentially over time as evidenced by the decrease in fluorescence. The squares represent average corrected fluorescence intensity values for an initial surface concentration of 10 µg per cm2 and the diamonds the corresponding values for an initial surface concentration of 3 µg per cm2. Error bars indicate the standard error of the mean. The solid lines represent the fitted exponential curves given by F = 9.9 × exp(-1.4t) and F = 5.1 × exp(-1.4t), respectively.
Journal of Investigative Dermatology  , DOI: ( /j x x)
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9. Figure 8
Comparison of the fluorescence method of quantifying salicylic acid on skin with the traditional method of tape stripping followed by HPLC. The data show average values from samples from nine volunteers. Error bars indicate the standard error of the mean. The fitted line is given by CHPLC = × CFluorescence with R2 =
Journal of Investigative Dermatology  , DOI: ( /j x x)
Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions