# Simple HPLC-PDA Analysis to Determine Illegal Synthetic Dyes in Herbal Medicines
## 1 Introduction  
Synthetic dyes are often used in various products, including food, dietary supplements, cosmetics, and drugs because they not only improve the products' physical appearance and visual attractiveness but are also relatively facile and cheap to produce [1]. Since synthetic dyes are frequently used in food and drug formulations, concerns regarding the safety of synthetic dyes have increased for decades. Although the evaluation for their toxicological potential has been continuously updated based on new findings [2], the following agenda is still an ongoing debate. Fortunately, several research works have demonstrated the risk of synthetic dyes provoking behavior disorders in children, including Attention-Deficit/Hyperactivity Disorder (ADHD), allergies, and hyperactivity [3]. According to the Rapid Alert System for Food and Feed (RASFF) portal, risk information related to the aduleration of synthetic colours in herbal medicines has reported that turmeric powders are adulterated by Orange II (2019. 9, Belgium) or Sudan I and Sudan II (2017.5, Finland). In another case, Orange II was artificially added to Safflowers (2019, 4, Germany and the United Kingdom). According to a survey of adulterated traditional Chinese medicines in China between 2003 and 2017, the adulteration of synthetic dyes in herbal medicines showed a trend toward gradual increase [4]. [PERSON] et al. [5] claimed that synthetic dyes, such as Azorubine, Auramine O, and Acid Orange 7, were found in _Schisandra chinensis_ (Schisandra fruit), _Carthanus tinctorius_ (Safflower), and _Salvia mittorhiza_ Bunge (Salvia Miltiorrhiza root). The following risk information in foreign countriesled us to establish a rapid and straightforward method urgently and essentially. By developing this method, we aimed to examine whether synthetic colorants adulterate herbal medicines because most herbal medicines consumed in Korea are mainly imported from other countries, including China. The Chinese government designated a list of synthetic dyes in herbal medicines that must be assessed to inhibit illegal usage. They also provided HPLC analyses to determine the existence of synthetic dyes in herbal drugs [6]. Since the addition of any synthetic dyes in herbal medicines is not allowed in Korea, there is an urgency to establish an appropriate analysis method to determine synthetic dyes in herbal medicines and distinguish whether these illegal synthetic dyes are adulterated or not in herbal medicines. Most of the herbal medicines used in Korea are imported from various countries, including China. Various analysis methods have been developed and studied for a long time to identify illegal dyes in food products, including techniques based on spectrophotometry [7], thin layer chromatography (TLC) [8], capillary liquid chromatography [9], enzyme-linked immunosorbent assay (ELISA) [10], electrochemical sensing devices [11], HPLC [1,12], and liquid chromatography-tandem mass spectrometry (LC-MS) [13]. Unlike reports related to analysis techniques for detecting illegal dyes in foods, some analytical methods have been reported to contain high-performance thin layer chromatography-mass spectrometry (HPTLC-MS) [14], high-performance liquid chromatography (HPLC) [15; 16; 17], and liquid chromatography-tandem mass spectrometry (LC-MS/MS) [5; 18; 19]. Additionally, several challengeable methods have been declared, including a computer vision system to determine synthetic colorants in dyed Safflower [20], Surface-enhanced Raman spectroscopy (SERS) for detection of Sudan dyes in herbal medicine [21], and Near-infrared spectroscopy (NIR) method to quantify chemical dyes in safflowers [22]. In general, the HPLC technique is considered to be a more economical and easily accessible procedure than LC-MS/MS. Most of the herbal medicine markets in our country are comparatively small, and usually, the herbal medicine companies prefer to use economic analysis procedures with low analysis expense when certain examinations of hazardous materials in their products are required.