Rapid On-site TLC-SERS Detection Of Adulterants In Botanical Dietary Supplements

Rapid on-site detection of Chinese patent medicines (CPM) adulteration has been a technological problem, because of the fact that there are too many kinds of CPM with complicated composition and their quality standard is not yet perfect. Our present work aims to establish TLC-SERS methods for CMP illegally added with chemical drugs, and analysis overlapping peaks difficulties which might exist in real sample detection, in order to provide new method and idea for the rapid detection of CMP adulteration.The article consists of two parts, the main research method is as follows:1) Hydrophilic and hydrophobic chemicals easily adulterated in hypoglycemic and antihypertensive CPM are considered as detect objects. By investigating the influence of various experimental parameters including TLC plate material, developing system, aqueous and organic silver sol preparation method, colloidal silver concentration and so on, as well as optimizing TLC and SERS test conditions, the initially established TLC-SERS method was used to detect real CPM samples. To consider the applicability and accuracy of our established method, the results obtained were then verified by liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) method.2) In view of SERS overlapping peaks appeared in real sample testing which caused by matrix interference and structural analogue coexist, we carry on various experimental attempting (e.g. changing developing system, scanning as point by point, adjusting pH value of the system, replacing silver sol) and spectral information mining (e.g. derivative spectrum, two dimensional correlation spectroscopy synchronization, independent component analysis), in order to improve the specificity of TLC-SERS method together from both chromatographic and spectroscopic perspective, and ultimately provide new ideas for establishing analytic method of TLC-SERS overlapping peaks. Results:1) HSGF254silica gel plate was preferred to be used in TLC-SERS method.2) Silver sol prepared by microwave heating method was applied for TLC-SERS detection and the best experimental parameters were obtained according to the enhancing rule of silver sol. Among the method, the best silver sol concentration was10mM (concentrated by five times) with a volume of5μL, and the suitable detection time need to be0～5min with an integration time of10s.3) TLC-SERS detection method was established, which was used to detect hypoglycemic and antihypertensive CPM illegally added with hydrophilic chemical drugs (phenformin hydrochloride, metformin hydrochloride, rosiglitazone maleate, pioglitazone hydrochloride, nicardipine hydrochloride, hydrochlorothiazide, doxazosin mesylate, propranolol hydrochloride), and corresponding LOD values were0.2%,0.18%,0.001%,0.016%,0.01%,0.01%,0.1%,0.1%and the detection of real CPM samples (twelve hypoglycemic samples and ten antihypertensive samples) was accomplished.4) TLC-SERS detection method of hydrophobic chemicals was initially established with obtaining corresponding spectra of gliclazide, glibenclamide, glimepiride, gliquidone, glipizide, repaglinide and nateglinide.5) By means of the following approaches, developing system adjustment, point by point scanning, independent component analysis and so on, the overlapping peaks appeared in the detection of the11th real antidiabetic CPM was successfully resolved, which confirmed the existence of phenformin hydrochloride.6) The parsing of SERS overlapping peaks caused by coexist of structural analogues pioglitazone hydrochloride and rosiglitazone maleate rosiglitazone was accomplished by approaches such as adjusting pH (pH=1.5), changing developing system (n-butyl alcohol-glacial acetic acid-water=11:2:2), derivative spectroscopy (second-order) and two dimensional correlation spectroscopy (synchronous spectrum). In this study, TLC-SERS method is applied in rapid testing of CPM adulteration for the first time, with obtaining some ideal results, such as SERS spectra of fifteen hypoglycemic and antihypertensive chemical drugs, as well as TLC-SERS detection methods for eight frequently adulterated hydrophilic drugs. By means of various experimental attempting (e.g. changing developing system, scanning as point by point, adjusting pH value of the system, replacing silver sol) and spectral information mining (e.g. derivative spectrum, two-dimensional correlation spectroscopy synchronization, independent component analysis), SERS overlapping peaks caused by matrix interference and structural analogue coexist have been resolved successfully. The strategy based on chromatographic and spectroscopic, together with experimental and metrological perspective to improve the resolution of SERS spectrum, provide new idea for TLC-SERS overlapping peaks analysis appearing in complex sample system. The idea of improving specificity from multi-angle and multi-strategy is also suitable for other analysis methods. TLC-SERS method established herein would be propitious to rapid detection of CPM adulteration for its simplicity, rapidity, high sensitivity and strong characteristics, and have good prospects in on-site detection of chemicals doped in Chinese pharmaceuticals. This study provides a new kind of high sensitive and reliable method for food and drugs safety test, pesticide residue detection and environmental pollutants monitoring.