一种可靠的化学需氧量（）免费方法。你提供的原文中括号里内容缺失，可能会影响准确理解。

Geerdink RenÃ Bernard, Brouwer Joyce, Epema Onno Jacob

Rijkswaterstaat, Centre for Water Management, PO Box 17, 8200 AA, Lelystad, The Netherlands.

Anal Methods. 2009 Nov 1;1(2):108-114. doi: 10.1039/b9ay00146h.

A simple, but reliable mercury free method to analyse chemical oxygen demand is introduced. The method is based on international standard procedures but avoids the highly toxic mercury. In the procedure the oxidation temperature is brought down from 148 °C to 120 °C. At this temperature the chloride interference is reduced to a large extent, whereas the oxidation of most compounds is still complete. Chloride interference is further reduced by addition of silver ions and practically absent at a molar ratio Ag+/Cl- over 1.7. Compounds that are difficult to oxidise even at 148 °C or only in the presence of silver ions are investigated at 120 °C. A slight reduction in recovery of 20-35% is observed for compounds like acetic acid, ethanol or lauryl sulfate in the absence of chloride. In the presence of 3000 mg L-1 chloride only the reduction for acetic acid is more pronounced due to the low availability of silver ions. The other compounds studied showed no further decrease in recovery. The interference of bromide is about 50% less at 120 °C than at 148 °C. The interference of ammonium in the presence of chloride is not confirmed in this method. The recovery of the method at high chloride and low COD concentration, i.e., at 3000 mg Cl- L-1 and 25 mg COD L-1, is acceptable (122%) whereas at 2000 mg Cl- L-1 and 25 mg COD L-1 it is better (110%). Precision is good; Relative standard deviations are 5.6% respectively 2.6%. The results of 99 wastewater samples over a wide range of chloride concentrations are similar compared to analyses based on ISO 15705 (cuvette) or ISO 6060. With the addition of 20 mL silver sulfate-sulfuric acid solution, the chloride in samples up to 3000 mg L-1 chloride is largely precipitated. More volume silver sulfate-sulfuric acid solution or a higher concentration of silver sulfate increases the range of samples that can effectively be analysed. The believed favourable effect of addition of Cr3+ to samples has not been confirmed. In the Netherlands 95% of about 100 000 wastewater samples that are analysed for COD each year have chloride concentrations below 3000 mg L-1 and could be analysed without the use of mercury. This may save as much as 10 kg mercury per annum. It will however require the additional use of about 0.5 kg of silver.

介绍了一种简单但可靠的无汞化学需氧量分析方法。该方法基于国际标准程序，但避免了使用剧毒的汞。在该程序中，氧化温度从148℃降至120℃。在此温度下，氯离子干扰在很大程度上得以降低，而大多数化合物的氧化仍能完全进行。通过添加银离子可进一步降低氯离子干扰，当银离子与氯离子的摩尔比超过1.7时，氯离子干扰几乎不存在。即使在148℃或仅在银离子存在下难以氧化的化合物，也在120℃下进行研究。在无氯离子的情况下，对于乙酸、乙醇或十二烷基硫酸盐等化合物，回收率略有下降，为20 - 35%。在存在3000 mg/L氯离子的情况下，由于银离子的可用性较低，仅乙酸的回收率下降更为明显。所研究的其他化合物回收率未进一步降低。在120℃时，溴离子的干扰比在148℃时约低50%。该方法未证实铵离子在存在氯离子时的干扰。在高氯离子和低化学需氧量浓度下，即3000 mg Cl⁻/L和25 mg COD/L时，该方法的回收率是可接受的（122%），而在2000 mg Cl⁻/L和25 mg COD/L时更好（110%）。精密度良好；相对标准偏差分别为5.6%和2.6%。与基于ISO 15705（比色皿）或ISO 6060的分析相比，99个不同氯离子浓度的废水样品的分析结果相似。加入20 mL硫酸银 - 硫酸溶液后，样品中高达3000 mg/L的氯离子大部分会沉淀。更多体积的硫酸银 - 硫酸溶液或更高浓度的硫酸银会增加可有效分析的样品范围。向样品中添加Cr³⁺的所谓有利效果未得到证实。在荷兰，每年分析化学需氧量的约100,000个废水样品中，95%的样品氯离子浓度低于3000 mg/L，无需使用汞即可进行分析。这每年可节省多达10千克汞。然而，这将额外需要约0.5千克银。