Enrichment of Trace Selenium in Water Based on Metal−Organic Framework Materials and Reversed−Phase Ultra−High−Performance Liquid Chromatography−Diode Array Determination

A method for the determination of trace selenium in water enriched by metal–organic−framework material (MIL−125−NH2) and reversed−phase ultra−high−performance liquid chromatography−diode array detection (UPLC−DAD) was established. The MIL−125−NH2 material, synthesized by the microwave method, was characterized by SEM, XRD, and FT−IR. The MIL−125−NH2 material was added to the water sample to enrich the selenium, the enriched selenium was desorbed with dilute HCl, and then the derivative reaction with 0.1 mol·L−1 4−nitro−o−phenylenediamine was performed to produce piaselenole. After extraction with cyclohexane, the retention time and the spectrogram were qualitatively detected by a liquid chromatography−diode array detector, and the peak area was quantitatively detected. The pH, time, amount of material, extractant, and other conditions of derivation and enrichment were optimized in the experiment, and the methodology was verified under optimized conditions. The results showed that the linear correlation coefficient R2 was 0.9998, the detection limit of 0.13 μg·L−1 without enrichment was close to that of the ICP−MS method, the detection limit after 10−fold enrichment was 0.013 μg·L−1, the RSD was 0.7~2.7%, and the recovery was 87.8~102.1%, in the range of 2~1000 μg·L−1. Therefore, the method can be applied for the determination of trace selenium in tap water, river water, mountain spring water, packaged drinking water, and industrial sewage.