Vij H S, Howell S
Jacobs Engineering Group of Ohio, Inc., Cincinnati 45240, USA.
Am Ind Hyg Assoc J. 1998 Jun;59(6):375-80. doi: 10.1080/15428119891010622.
Changes in urinary flow induce changes in urinary concentrations of toxic substances. The authors modified the conventional specific gravity adjustment method for measuring urinary concentration of toxic substances to compensate for the dilution effects from varying degrees of hydration. The conventional specific gravity adjustment method is a special case to the more general method proposed in this article. The conventional method generally does not correct the urinary concentration to the mean specific gravity of urine. It requires the assumption that a change in urine flow preserves the relative ratio between the mass of the xenobiotic and the mass of total dissolved solids. The derivation of the modified specific gravity adjustment method shows that a change in urine flow does not necessarily preserve this ratio. An experimental slope between urinary flow and urinary specific gravity was linear on a log scale. A ratio was formed between the experimental slope and Araki's "b" slopes for various substances to predict changes in urine concentrations due to changes in the specific gravity of a spot sample. Since excretion rates typically vary for different substances with changes in urinary flow, an appropriately weighted exponential adjustment factor is required for each substance to normalize its concentration to the standard specific gravity of urine.
尿流变化会引起尿液中有毒物质浓度的变化。作者改进了用于测量尿液中有毒物质浓度的传统比重调整方法，以补偿不同程度水合作用产生的稀释效应。传统比重调整方法是本文提出的更通用方法的一个特例。传统方法通常不会将尿液浓度校正到尿液的平均比重。它需要假设尿流变化会保持外源性物质质量与总溶解固体质量之间的相对比例。改进后的比重调整方法的推导表明，尿流变化不一定会保持这一比例。尿流与尿比重之间的实验斜率在对数尺度上呈线性。在实验斜率与不同物质的荒木“b”斜率之间形成一个比率，以预测由于即时样本比重变化导致的尿液浓度变化。由于不同物质的排泄率通常会随着尿流变化而变化，因此需要为每种物质使用适当加权的指数调整因子，将其浓度归一化到尿液的标准比重。
