Strategies for SERS Detection of Organochlorine Pesticides

Abstract

Organochlorine pesticides (OCPs) embody highly lipophilic hazardous chemicals that are being phased out globally. Due to their persistent nature, they are still contaminating the environment, being classified as persistent organic pollutants (POPs). They bioaccumulate through bioconcentration and biomagnification, leading to elevated concentrations at higher trophic levels. Studies show that human long-term exposure to OCPs is correlated with a large panel of common chronic diseases. Due to toxicity concerns, most OCPs are listed as persistent organic pollutants (POPs). Conventionally, separation techniques such as gas chromatography are used to analyze OCPs (e.g., gas chromatography coupled with mass spectrometry (GC/MS)) or electron capture detection (GC/ECD). These are accurate, but expensive and time-consuming methods, which can only be performed in centralized lab environments after extensive pretreatment of the collected samples. Thus, researchers are continuously fueling the need to pursue new faster and less expensive alternatives for their detection and quantification that can be used in the field, possibly in miniaturized lab-on-a-chip systems. In this context, surface enhanced Raman spectroscopy (SERS) represents an exceptional analytical tool for the trace detection of pollutants, offering molecular fingerprint-type data and high sensitivity. For maximum signal amplification, two conditions are imposed: an efficient substrate and a high affinity toward the analyte. Unfortunately, due to the highly hydrophobic nature of these pollutants (OCPs,) they usually have a low affinity toward SERS substrates, increasing the challenge in their SERS detection. In order to overcome this limitation and take advantage of on-site Raman analysis of pollutants, researchers are devising ingenious strategies that are synthetically discussed in this review paper. Aiming to maximize the weak Raman signal of organochlorine pesticides, current practices of increasing the substrate’s performance, along with efforts in improving the selectivity by SERS substrate functionalization meant to adsorb the OCPs in close proximity (via covalent, electrostatic or hydrophobic bonds), are both discussed. Moreover, the prospects of multiplex analysis are also approached. Finally, other perspectives for capturing such hydrophobic molecules (MIPs—molecularly imprinted polymers, immunoassays) and SERS coupled techniques (microfluidics—SERS, electrochemistry—SERS) to overcome some of the restraints are presented.

Advances in Optical Sensors for Persistent Organic Pollutant Environmental Monitoring

“…A brief overview on applications of spectroscopy technology to trace the analysis of persistent organic pollutants was previously published by Wang, Pang, and Zhou [ 9 ]; the techniques for the detection of dioxins, furans and related compounds based on optical and spectroscopic methods were reported by Patrizi et al [ 10 ]. In [ 11 ], the recent updates on the strategies for organochlorine pesticides SERS detection were provided. In [ 12 ], the detection methods of POPs in food, along with their contamination sources and effects on health, are discussed.…”

Stationary, Continuous, and Sequential Surface‐Enhanced Raman Scattering Sensing Based on the Nanoscale and Microscale Polymer‐Metal Composite Sensor Particles through Microfluidics: A Review

“…SERS is an advanced analytical technique that works on the principle of enhancement of the Raman scattering signals when molecules are located on the roughened metallic surface. [11,13,[46][47][48] Various analytes such as, soil contaminants, [49] fluid contaminants, [50] trace amounts of pesticides on foods, [51] trace concentrations of air contaminants, [52][53][54][55] explosives, [56] etc., are dispersed in the diverse environment of liquid, solid, or gaseous phases. It is an important objective to detect such types of targeting analytes with high specificity and sensitivity for healthcare and other purposes.…”

Rapid field trace detection of pesticide residue in food based on surface-enhanced Raman spectroscopy

“…The bald structure and excess chlorine atoms present the weak affinity of organochlorine pesticides to substrate and dramatically reduce the sensitivity of SERS detection [94]. Hence, a great deal of effort has been made to break this limitation.…”

“…However, this method has a strict requirement with control of the thickness of the inert shell of the substrate. Employing electrochemical methods could help improve substrate's reproducibility and stability [94]. Zhu et al fabricated highly ordered array of Agnanorod bundles by developing a binary-template-assisted electrodeposition method.…”