# Recent Advances in Spectroscopy Technology for Trace Analysis of Persistent Organic Pollutants
## 1 Introduction  
Persistent organic pollutants (POPs) are of global concern due to their toxicity and bioaccumulation in adipose tissue through the food chain [1; 2; 3; 4]. They mainly contain polychlorinated biphenyls (PCBs), organochlorine pesticides (OPs), polycyclic aromatic hydrocarbons (PAHs), and some other organic chemicals, such as polychlorinated dibenzo-\(p\)-dioxins, which are mainly produced by anthropogenic activities [5; 6]. POPs can persist for a long time in the environment because of their resistance to degradation, potentially leading to food contamination and threat to human health [7]. As a result, significant attention has been paid to the development of low-cost and reliable methods for the determination of ultratrace concentrations of POPs. Though conventional techniques, such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC/MS), have great accuracy and widespread applications, most of them suffer from expensive equipment and time-consuming purification processes [8; 9; 10]. Therefore, an enormous amount of effort has been devoted to exploring novel strategies like surface-enhanced Raman spectroscopy (SERS) [11; 12], enzyme-linked immunosorbent assay (ELISA), and fluorescence [13; 14].  
Among these emerging methods, spectroscopy technologies are favorable for trace detection of POPs due to their inherent advantages, such as high sensitivity and rapid and real-time monitoring. Spectroscopy technologies generally consist of SERS, surface plasmon resonance (SPR), and fluorescence.  
The reasons for utilizing these methods to detect POPs are as follows: (1) SERS is well suited for detecting POPs due to its capability of providing vibrational spectroscopic fingerprints which indicate the inherent molecular structure of analytes, and allows a limit of detection at very low concentrations, even down to the single molecule level [15; 16; 17; 18]; (2) although POPs are small organic molecules, some compounds like PCBs and benzo[a]pyren (i.e., BaP) possess a high refractive index. Taking into consideration such properties, the SPR sensor would be much more suitable for trace detection of POPs than any other sensor, such as gravimetric sensors, because it is a refractive-index-sensitive device with label-free detection capability and high sensitivity [19; 20]; and (3) the molecular structures of most POPs consist of aromatic rings, which lead them to show inherent fluorescence [21; 22; 23]. Thus, fluorescence spectroscopy, as a sensitive analytical method, can be used for the trace detection of POPs.  
The investigation of environmental monitoring with spectroscopy technology has motivated some recent review articles that refer to different aspects of primary theory as regards specific applications. This paper was focused on some critical issues and practical applications of spectroscopy technology for the trace detection of POPs. Finally, this paper covered some current challenges and future applied prospects of spectroscopy technology in the detection of small molecular environmental pollutants.