A novel sample double dilution calibration method (SDDCM) and an automatic flow system with in-syringe reaction and spectrophotometric detection were developed for determining lithium in biological samples. The method is based on the reaction of lithium with Thorin in an alkaline medium and the signal was measured at 480 nm. The reaction was performed simultaneously for both standards and samples in three syringes of the automatic flow system. The method was validated and successfully applied to the determination of lithium in synthetic and pharmaceutical samples, with results consistent with the ICP OES method. The novel calibration method, developed for the determination of lithium in biological samples, uses a sample with two dilution degrees. Using the method, the concentration of the analyte is determined by relating the signal for a less diluted sample to the calibration plot for a more diluted sample and vice versa. The implementation of the calibration method was facilitated by preparing solutions directly in the flow system. The use of two sample dilutions makes it possible to determine the analyte in the sample without preliminary preparation. Moreover, obtaining two results based on signals for a sample diluted to different degrees allows them to be verified for accuracy. The proposed approach was successfully verified by the determination of lithium in certified reference materials of blood serum and urine. Using the developed method lithium was determined within the concentration range of 0.06–1.5 mg L, with precision (CV, %) less than 6.7, and accuracy (RE, %) better than 6.9. The detection limit was 0.03 mg L.

中文翻译：

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使用注射器内反应自动流动系统测定生物样品中锂的新型样品双稀释校准方法

开发了一种新颖的样品双重稀释校准方法（SDDCM）以及具有注射器内反应和分光光度检测功能的自动流动系统，用于测定生物样品中的锂。该方法基于锂与索林在碱性介质中的反应，并在 480 nm 处测量信号。标准品和样品在自动流动系统的三个注射器中同时进行反应。该方法经过验证并成功应用于合成样品和药物样品中锂的测定，结果与 ICP OES 方法一致。这种新颖的校准方法是为测定生物样品中的锂而开发的，使用具有两种稀释度的样品。使用该方法，通过将稀释程度较低的样品的信号与稀释程度较高的样品的校准图相关联来确定分析物的浓度，反之亦然。通过直接在流动系统中制备溶液，促进了校准方法的实施。使用两种样品稀释液无需预先制备即可测定样品中的分析物。此外，根据稀释到不同程度的样品的信号获得两个结果可以验证它们的准确性。通过血清和尿液标准物质中锂的测定，成功验证了所提出的方法。采用该方法测定锂浓度范围为0.06~1.5 mg·L，精密度（CV，%）小于6.7，准确度（RE，%）优于6.9。检出限为0.03 mg·L。