美国环境保护署（US Environmental Protection Agency）要求在收集用于铅分析的饮用水样本时对其进行酸化，这带来了两个问题:（1）邮寄硝酸的限制；（2）与非技术人员可能处理硝酸相关的安全问题。进行的一项研究表明，酸化可延迟14天，然后在等待28小时后进行分析，而不会损失铅。包括5个参考文献、表格。

The US Environmental Protection Agency's requirement that drinking water samples collected for lead analysis be acidified at the time of collection poses two problems: (1) restrictions on mailing nitric acid and (2) safety concerns associated with the possible handling of nitric acid by nontechnical persons. A study was undertaken that showed that acidification could be delayed up to 14 days and that analysis could then be carried out after waiting 28 h, without loss of lead. Includes 5 references, tables.