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目的探讨不同温度、不同保存时间及反复冻融对尿中各形态砷稳定性的影响。方法于2011年3月,采集8名健康志愿者的尿液样品。采用氢化物发生-冷阱捕集-原子吸收(HG-cold trap-AAS)法检测不同保存条件[尿样分别置于室温(25℃)和4、-20、-80℃冰箱中继续避光保存1、3个月]和反复冻融(冻融条件:-20、-80℃冻存至少1 d,室温2 h解冻,再次放入冰箱)3次后尿样中各形态砷[无机砷(iAs)、一甲基砷(MMA)和二甲基砷(DMA)、三甲基砷(TMA)]的浓度。每次检测前解冻,并设立对照。结果仅25℃条件下保存3个月样品中DMA浓度低于对照,差异有统计学意义(P<0.05);其他保存条件下尿样中各形态砷的浓度与对照比较,差异均无统计学意义。在低温(-20、-80℃)条件下反复冻融3次后尿样中各形态砷的浓度与对照比较,差异均无统计学意义。结论低温(4、-20、-80℃)保存3个月内以及冻融3次的尿样中各形态砷浓度仍较为稳定。
Objective To investigate the effects of different temperature, storage time and repeated freezing and thawing on the stability of arsenic in urine. Methods In March 2011, urine samples from 8 healthy volunteers were collected. HG-cold trap-AAS method was used to detect the different storage conditions [urine samples were kept in the refrigerator at room temperature (25 ℃) and 4, -20, -80 ℃, respectively, Stored for 1, 3 months] and repeated freezing and thawing (frozen-thawed condition: -20, frozen at -80 ℃ for at least 1 day, thawed at room temperature for 2 hours, and then placed in the refrigerator again) (iAs), monomethyl arsenic (MMA) and dimethyl arsenic (DMA), trimethyl arsenic (TMA)]. Thaw before each test and set up a control. Results The concentration of DMA in the sample stored at 25 ℃ for 3 months was lower than that in the control, the difference was statistically significant (P <0.05). The concentrations of arsenic in different samples under different storage conditions were not statistically different from the control significance. After frozen and thawed three times at low temperature (-20, -80 ℃), the concentrations of arsenic in each sample were not significantly different from the control. Conclusion The concentrations of various forms of arsenic in urine samples stored within 3 months at low temperature (4, -20, -80 ℃) and 3 times after freeze-thaw cycles are still relatively stable.