With the development of the liquid waveguide capillary cell (LWCC), the method sensitivity can be easily achieved by increasing of the flow cell length. Now, LWCC has been applied to field studies in the open ocean. For the robust, reliable, autonomous environmental monitoring instrument, we development of an combined with LWCC (iSEA-LWCC). The iSEA-LWCC consists of a syringe pump equipped with a 9-port valve and controlled by software written in LabVIEW. The optical flow cell was 2.5-m LWCC. The iSEA-LWCC has been applied for, the determination of trace elements in water. The main contents and results are summarized as follows:

(1) Phosphorus is an essential nutrient element used by marine phytoplankton. As the major component of inorganic phosphorus, dissolved reactive phosphorus (DRP) plays an important role in the marine biogeochemical cycle of phosphorus. The process of chemical reactions is based on phosphorus molybdenum blue spectroscopic spectrophotometry coupled with a 2.5-m LWCC, a convenient method for determination of trace of SRP was established. The sample throughput was 12 per hour. The relative standard deviation (n=66) was 0.98% for a sample with concentration of 80 nmol/L. The detection limit is ~1 nmol/L.

(2) Chromium (VI) is a recognized hazardous substance in drinking waters. Therefore, effective monitoring and assessment of the risks posed by Cr (VI) are important analytical objectives for both environmental science and human health. Here, we developed a simple and sensitive method for analysis of Cr (VI) at nanomolar levels. The measurement chemistry is based on a reaction with diphenyl carbazide under acidic conditions, with a 2.5-m LWCC and spectrophotometric detection. The instrument is controlled by software written with LabVIEW. The determination of a sample only needed 4 min. The linear calibration range from 0 to 100 nmol/L with detection limit of ~0.3 nmol/L.

The iSEA-LWCC instrument has the potential for long-term online monitoring of trace nutrients and metals in environmental water samples. More evaluation and applications are under development.