On-chip solid phase extraction and in situ optical detection

A device was designed integrating solid phase extraction (SPE) and in situ optical detection techniques. A chip assembled in the device to carry out SPE was enclosed in a fully reflective aluminum box to avoid loss of radiation flux in the optical measurement. The spectrum was measured on the SPE material directly after SPE. The device offers simple analytical operation without any elution step comparing with the traditional analytical methods with complicated procedures. The device and the developed analytical technique was used for the determination of rhodamine B and benzo[a]pyrene with UV-visible diffuse reflectance and solid phase fluorescence spectroscopies, respectively. Under optimal conditions, standard curves of rhodamine B and benzo[a]pyrene showed a linear relationship in concentration ranges of 10-800 μg L^-1 (R² = 0.99) and 0.07-3.33 μg L^-1 (R² = 0.99), respectively. The limit of detections (LOD) were 7 μg L^-1 and 0.02 μg L^-1. The proposed device was successfully employed to quantify rhodamine B and benzo[a]pyrene in tap water samples. The results showed that the recoveries were 90-105% and the relative standard deviations (RSDs) were 2.53-5.55%, indicating that the device and analytical method is capable of trace analytes for rapid quantitative analysis in various samples.