磷酸酶水解技术是研究沉积物有机磷形态和生物有效性的有力工具.沉积物样品处理过程对酶水解有机磷的影响尚不清楚.为此,以天鹅湖表层沉积物为研究对象,研究了干燥方式、提取剂、提取比例、提取时间条件对沉积物酶水解有机磷的影响特征,以寻求最佳的酶水解技术的实验条件.研究结果表明,自然风干处理引发了有机磷水解,降低了磷酸二酯磷(Diester-P)含量.而冻干处理更真实地保存了沉积物有机磷形态特征,比较合适有机磷分析.尽管HCl预提取显著增大了有机磷的提取比例,但是存在Diester-P水解风险,因此NaOH/EDTA一步提取更适合有机磷的测定.较长的提取时间和较大国液比同样也显著增大了有机磷的提取效率,但是同样存在Diester-P水解风险.研究显示Diester-P极不稳定,易受实验条件的影响,在实际操作中需要特别注意.总之沉积物样品采用冷冻干燥处理,固液比1:30,采用0.25 mol·L-1NaOH+50 mmol· L-1EDTA提8h更适合沉积物酶水解有机磷的分析.
Enzymatic hydrolysis is a powerful tool to study the speciation and bioavailability of sediment organic phosphorus (P).However,the effects of the sample treatment on the enzymatic hydrolysis need to be fully understood.In order to investigate the optimal condition for enzymatic hydrolysis,the surface sediments of Swan Lake were collected to study the effects of sample preparation procedures,including sample pretreatment,extraction solution,extraction time,and ratio of sample to extraction efficiency on enzymatic hydrolysis.The results showed that air-drying caused the hydrolysis of diester-P in sediments.Freeze drying preserved the characteristics of organic phosphorus,and is recommended for the study of organic phosphorus in sediments.Although the recovery of P was significantly increased by HCl pre-extraction,there is also a risk of diester-P hydrolysis at the same time.As a result,one step extraction of NaOH/EDTA is recommended for enzymatic hydrolysis of organic phosphorus in sediment.In addition,longer extraction time and higher extraction ratio (S (sediment)/V (volume)) tend to increased the risk of diester-P hydrolysis although they increased the recovery of P from sediment.Our results suggest that diester-P in sediment is extremely unstable and vulnerable to extraction conditions.Thus it deserves special caution with sample analysis and data interpretation.In conclusion,the freeze dried sediments were extracted with 0.25 mol· L-1 NaOH+50 mmol· L-1 EDTA at 8 h and sediment/solution ratio of 1∶30 which were recommended for enzymatic hydrolysis of organic phosphorus in sediments.
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