Thin-layer chromatography
(TLC) is an effective and simple technique
for screening, evaluating, and quantifying low-quality and counterfeit
pharmaceutical products. Smartphones have recently been used as accessible,
cheap, and portable detectors that can replace more complicated analytical
detectors. In this work, we have developed a simple and sensitive
TLC method utilizing a smartphone charged-coupled device (CCD) camera
not only to verify and quantify some gastrointestinal tract drugs,
namely, loperamide hydrochloride (LOP) and bisacodyl (BIS), but also
to detect acetaminophen (ACT) as a counterfeit drug. Both drugs (LOP
and BIS) were chromatographed separately on a silica gel 60 F
254
plate as a stationary phase under previously reported chromatographic
conditions, using ethyl acetate:methanol:ammonium hydroxide (24:3:1,
by volume) and ethyl acetate:methanol:glacial acetic acid (85:10:5,
by volume) as developing systems to determine LOP and BIS, respectively.
Universal stains, namely, iodine vapors and vanillin, were used to
visualize the spots on the TLC plates to get a visual image using
the smartphone camera and a spotlight as an illumination source with
no need for a UV illumination source. The spot intensity was calculated
using a commercially available smartphone application for quantitative
analysis of the studied drugs utilizing ″acetaminophen″
as an example of a counterfeit substance. R
f
values were
calculated using the recorded images and found to be 0.77, 0.79, and
0.74 for LOP, BIS, and ACT, respectively, providing drug identity.
Linear calibration curves using the smartphone–TLC method were
obtained between the luminance and the corresponding concentrations
over the ranges of 2.00–10.00 μg/mL and 1.00–10.00
μg/mL with limits of detection of 0.57 and 0.10 μg/mL
for LOP and BIS, respectively. The suggested method was validated
according to the International Conference of Harmonization (ICH) guidelines.
The method was then successfully applied for the qualitative and quantitative
determination of LOP or BIS as an example for gastrointestinal tract
drugs in pure form and in their pharmaceutical dosage formulations.
The proposed method is considered as a perfect alternative to traditional
reported densitometric methods due to its simplicity, easy application,
and inexpensiveness. No previously reported methods utilizing smartphones
have been published for the determination of the studied drugs. The
developed approach is considered the first TLC method using smartphones
for the determination of some gastrointestinal tract drugs in their
pure form and in pharmaceutical formulations.