He Da, Zheng Maosheng, Ma Tao, Ni Jinren
Shenzhen Key Laboratory for Heavy Metal Pollution Control and Reutilization, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, China; Department of Environmental Engineering, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Peking University, Beijing 100871, China E-mail:
Department of Environmental Engineering, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Peking University, Beijing 100871, China E-mail:
Water Sci Technol. 2015;72(2):223-9. doi: 10.2166/wst.2015.203.
Cr(VI) is highly noted as a carcinogenic, mutagenic, and teratogenic pollutant. However, accurate determination of Cr(VI) in aqueous samples is difficult using the conventional diphenylcarbazide (DPCI) spectrophotometric method upon being interfered by co-existed nitrite. This paper illustrates how to eliminate the nitrite influence in a simple but efficient method based on a detailed analysis of interference mechanism. High-performance liquid chromatography analysis revealed that under acidic condition, DPCI was oxidized by nitrite to other substrates, which could not react with Cr(VI). The final oxidation product of DPCI was further purified by thin-layer chromatography and identified as diaryl carbodiazone by Fourier Transform Ion Cyclotron Resonance-Mass Spectrometry (FTICR-MS) and nuclear magnetic resonance. Consequently, an improved method was proposed by simply adding sulfamic acid for eliminating the nitrite interference in Cr(VI) determination. The proposed method was successfully confirmed by the accurate recovery of Cr(VI) from spiked water samples and further proven with inductively coupled plasma-atomic emission spectroscopy, which demonstrated a great potential for determining Cr(VI) concentration in aqueous samples containing nitrite.
六价铬作为一种致癌、致突变和致畸污染物备受关注。然而，在常规二苯卡巴肼（DPCI）分光光度法测定水样中的六价铬时，若受到共存亚硝酸盐的干扰，准确测定会变得困难。本文基于对干扰机制的详细分析，阐述了如何用一种简单而有效的方法消除亚硝酸盐的影响。高效液相色谱分析表明，在酸性条件下，DPCI被亚硝酸盐氧化为其他底物，这些底物不能与六价铬反应。通过薄层色谱对DPCI的最终氧化产物进一步纯化，并通过傅里叶变换离子回旋共振质谱（FTICR-MS）和核磁共振鉴定为二芳基卡二氮烯。因此，提出了一种改进方法，即简单地加入氨基磺酸来消除六价铬测定中亚硝酸盐的干扰。通过对加标水样中六价铬的准确回收率成功验证了该方法，并通过电感耦合等离子体原子发射光谱进一步证明该方法在测定含亚硝酸盐水样中六价铬浓度方面具有巨大潜力。
