Abstract：
Reliable high-resolution data is essential for understanding the aquatic sulfur biogeochemical processes. However, the accurate quantification of total dissolved sulfide (TDS) remains challenging due to its low concentration and vulnerability to oxidation. Furthermore, the frequency and the spatial coverage of TDS measurements are constrained by the cost of the laboratory analysis. In this study, an automated portable system was developed for on-site real-time measurement of trace TDS in natural waters. This system was based on the classic methylene blue (MB) spectrophotometric assay combined with on-line solid phase extraction (SPE) and flow injection analysis (FIA). A commercially available weak-cation-exchange cartridge was used as the SPE sorbent. Experimental parameters affecting the performance of the proposed system were optimized. Under the optimized conditions, linear calibration range of 0.02-2.50 μmol L-1 was obtained with a sample loading volume of 5.0 mL and a sample throughput of 12 h-1. The limit of detection could be lowered to 0.003 μmol L-1 by pre-concentrating 10.0 mL sample. The precision, determined as the relative standard deviation (RSD), was <2.75 % (n = 11) and the recoveries from spiked samples ranged from 54.4 % to 97.5 % with RSDs of 1.1-2.3 % (n = 3). Furthermore, the FIA-SPE-MB system was successfully deployed in the Taihu Lake for continuous 48 h monitoring of variations in TDS, demonstrating the applicability of this system for on-site TDS measurement in natural waters.
摘要：
可靠的高分辨率数据对于理解水生硫生物地球化学过程至关重要。然而,由于总溶解硫化物（TDS）的浓度低和易于氧化，因此准确定量仍然具有挑战性。此外，TDS测量的频率和空间覆盖范围受到实验室分析成本的限制。在这项研究中,开发了一种自动便携式系统，用于自然水域中痕量TDS的现场实时测量。该系统基于经典的亚甲基蓝（MB）分光光度法，结合在线固相萃取（SPE）和流动注射分析（FIA）。市售的弱阳离子交换柱用作SPE吸附剂。优化了影响所提出系统性能的实验参数。在优化条件下,线性校准范围为0.02-2.50μmolL-1，样品加载量为5.0mL，样品通量为12h-1。通过预浓缩10.0mL样品，检测限可以降低到0.003μmolL-1。精度，确定为相对标准偏差(RSD)，<2.75％（n=11），加标样品的回收率为54.4％至97.5％，RSD为1.1-2.3％（n=3）。此外，FIA-SPE-MB系统成功部署在太湖，连续48小时监测TDS的变化，证明该系统适用于自然水域的现场TDS测量。
