An overview of the recent developments of microfluidic paper-based analytical devices for the detection of chromium species

Chromium pollution in the environment is a serious problem as it is harmful to humans and the environment. The current methods for the detection of chromium species require expensive instrumentation and need to be operated in centralized laboratories. Recently, microfluidic paper-based analytical devices (mu PADs) have been developed as simple, cost-effective, and portable tools for on-site detection. In this review, we highlight the recent developments of mu PADs for the screening and detection of chromium species in environmental samples. We first summarize the chemistry and toxicity of chromium, the selection of paper substrates, and the device fabrication methods. We then categorize the recent reports on the basis of chromium species into trivalent chromium, hexavalent chromium, speciation, and total chromium detection groups. The evaluation of the performance of mu PADs with regard to their accuracy and detection limits is critically assessed. Finally, we discuss the future development and trends in the field of mu PADs.