Huang Xiao-Lan, Zhang Jia-Zhong
Ocean Chemistry Division, Atlantic Oceanographic and Meteorological Laboratory, National Oceanic and Atmospheric Administration, Miami, FL 33149, USA.
Talanta. 2008 Oct 19;77(1):340-5. doi: 10.1016/j.talanta.2008.06.041. Epub 2008 Jul 5.
Acidic persulfate oxidation is one of the most common procedures used to digest dissolved organic phosphorus compounds in water samples for total dissolved phosphorus determination. It has been reported that the rates of phosphoantimonylmolybdenum blue complex formation were significantly reduced in the digested sample matrix. This study revealed that the intermediate products of persulfate oxidation, not the slight change in pH, cause the slowdown of color formation. This effect can be remedied by adjusting digested samples pH to a near neural to decompose the intermediate products. No disturbing effects of chlorine on the phosphoantimonylmolybdenum blue formation in seawater were observed. It is noted that the modification of mixed reagent recipe cannot provide near neutral pH for the decomposition of the intermediate products of persulfate oxidation. This study provides experimental evidence not only to support the recommendation made in APHA standard methods that the pH of the digested sample must be adjusted to within a narrow range of sample, but also to improve the understanding of role of residue from persulfate decomposition on the subsequent phosphoantimonylmolybdenum blue formation.
酸性过硫酸盐氧化是用于消解水样中溶解有机磷化合物以测定总溶解磷的最常用方法之一。据报道，在消解后的样品基质中，磷锑钼蓝络合物的形成速率显著降低。本研究表明，过硫酸盐氧化的中间产物而非pH值的微小变化导致显色速度减慢。通过将消解后的样品pH值调节至接近中性以分解中间产物，可纠正这种影响。未观察到氯对海水中磷锑钼蓝形成的干扰作用。需要注意的是，混合试剂配方的修改无法为过硫酸盐氧化中间产物的分解提供接近中性的pH值。本研究不仅提供了实验证据来支持美国公共卫生协会标准方法中的建议，即必须将消解后样品的pH值调节至样品的窄范围内，还增进了对过硫酸盐分解残留物在后续磷锑钼蓝形成中的作用的理解。
