Factors influencing the cleaning of plant samples with ultrasonic technology

Effective cleaning of biological samples is a critical step in environmental studies. However, the literature lacks standardized cleaning procedures and protocols and there is little information about how even the most basic conditions may affect cleaning efficiency. Here, leaves of different species were first exposed to the soil naturally containing mercury particles and then washed in an ultrasound water bath under the following conditions: newly cleaned/reused beakers, water temperature, sample immersion/free-floating, sample quantity, and the number of washing cycles. Additionally, the effects of sample pubescence on cleaning efficacy were also assessed. Results indicated that the best cleaning efficacy was recorded when samples were placed in cold water under forced immersion and beakers were cleaned between washing cycles. At least two of these three conditions were needed for adequate washing. The results also indicated that, for the glabrous leaves, a cumulative leaf surface area of ≤10,000 mm2 was efficiently cleaned after 3–5 washing cycles, while as pubescence increased, 9–11 cycles were needed and often the sample quantity had to be reduced (<5,000 mm2). Our experiments reveal that cleaning can be optimized by applying easy procedures and according to individual sample typology, resulting in faster and more effective cleaning.
Novelty statement
The cleaning of samples is a frequent stage in the analytical processes of phytoremediation studies. This work provides new and valuable information to optimize the cleaning of plant samples by simply applying ultrasonic technology and distilled water. In fact, we have tested the influence of some factors never taken into account previously.

生物样品的有效清洗是环境研究中的关键环节。然而，现有文献中缺乏标准化的样品清洗流程与规范，且即便对于最基础的实验条件如何影响清洗效率这一问题，相关研究信息也极为匮乏。本研究将不同物种的叶片先暴露于自然含有汞颗粒的土壤中，随后在超声水浴中按照以下变量条件进行清洗：经初次清洁的烧杯/复用烧杯、水温、样品浸没/自由漂浮状态、样品投放量以及清洗循环次数。此外，本研究还评估了样品表皮毛（pubescence）对清洗效果的影响。
实验结果显示，当样品置于冷水中并强制浸没，且在每次清洗循环之间清洁烧杯时，可获得最优的清洗效果。若要实现充分有效的清洗，至少需满足上述三项条件中的两项。结果同时表明，对于光滑无毛叶片（glabrous leaves）而言，当累计叶表面积≤10000 mm²时，经过3~5次清洗循环即可实现高效清洗；而随着表皮毛密度增加，则需要9~11次清洗循环，且通常需要减少样品投放量（<5000 mm²）。本研究实验结果表明，通过采用简便的操作流程，并结合不同样品的类型特征进行调整，可实现样品清洗流程的优化，从而获得更快、更高效的清洗效果。

创新性说明
样品清洗是植物修复（phytoremediation）研究分析流程中的常见环节。本研究仅通过超声技术与蒸馏水即可实现植物样品清洗流程的优化，为相关研究提供了全新且极具价值的参考信息。事实上，本研究首次针对此前未被纳入考量的多项因素的影响进行了实验验证。