Calcium and magnesium ions are highly abundant and important cations in human body. At the same time, both dyscalcemia and dysmagnesemia are frequently encountered in the clinical practice. As deficiency or excess of Ca(II) or Mg(II) can cause severe symptoms, determining these ions in serum is of great importance. Concentration of these ions in biological samples is typically assayed in clinical laboratories with the use of expensive and specialized equipment. Since those methods cannot be easily adapted for self-diagnosis purposes, there is a great need to develop a convenient tool for reliable determination of calcium and magnesium in serum at the point-of-care. The colorimetric methods employed for calcium and magnesium analysis were -cresophtalein complexone assay and xylidyl blue assay, respectively. Analytical signal acquisition was accomplished using an ordinary flatbed scanner or smartphone and free software. For increased user-friendliness the device was optimized to perform simultaneous determination of calcium and magnesium ions in only 10 min. In the optimized conditions, the limit of detection for calcium ions was 0.09 mmol L, while for magnesium it was 0.04 mmol L. Determination of both ions requires only 4 μL of serum sample. The developed paper-based sensors were validated with control human serum samples and the obtained relative errors for majority of samples were below 20 %. In this paper, a microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum is reported for the first time. Additionally, this is also the first report on colorimetric determination in serum of any of these ions in paper-based format. Simultaneous detection of both ions allows for fast and user-friendly screening of disturbance in calcium and magnesium homeostasis.

中文翻译：

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一种同时测定人血清中钙、镁离子的微流控纸基分析装置


钙和镁离子是人体内含量丰富且重要的阳离子。同时，临床实践中也经常遇到钙血症和镁血症。由于 Ca(II) 或 Mg(II) 缺乏或过量都会导致严重症状，因此测定血清中的这些离子非常重要。生物样品中这些离子的浓度通常在临床实验室中使用昂贵的专用设备进行测定。由于这些方法不能轻易地用于自我诊断目的，因此非常需要开发一种方便的工具来在护理点可靠地测定血清中的钙和镁。用于钙和镁分析的比色方法分别是β-甲酰维生素E络合酮测定法和二甲苯氨蓝测定法。使用普通平板扫描仪或智能手机和免费软件完成分析信号采集。为了提高用户友好性，该设备经过优化，只需 10 分钟即可同时测定钙和镁离子。在优化条件下，钙离子的检测限为 0.09 mmol L，镁离子的检测限为 0.04 mmol L。这两种离子的测定仅需要 4 μL 血清样品。开发的纸基传感器通过对照人血清样本进行了验证，大多数样本获得的相对误差低于 20%。本文首次报道了一种用于同时测定人血清中钙、镁离子的微流控纸基分析装置。此外，这也是第一份以纸质形式对血清中任何这些离子进行比色测定的报告。 同时检测两种离子可以快速且用户友好地筛查钙和镁稳态紊乱。