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首页> 外文期刊>Marine Chemistry >Purification of meta-cresol purple and cresol red by flash chromatography: Procedures for ensuring accurate spectrophotometric seawater pH measurements
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Purification of meta-cresol purple and cresol red by flash chromatography: Procedures for ensuring accurate spectrophotometric seawater pH measurements

机译：通过快速色谱法纯化间甲酚紫和甲酚红：确保准确的分光光度法测量海水pH值的步骤

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Impurities in sulphonephthalein indicator salts can result in significant errors in seawater pH determinations. To ensure suitable measurement accuracy and intercomparability on a global basis, impurities must be removed from all indicators used for oceanographic CO_2 system analyses. Previous work has described an effective HPLC (high-performance liquid chromatography) procedure for purification of meta-cresol purple, but the technique is labor-intensive, with each HPLC run producing only a small batch of purified indicator. This work describes the use of flash chromatography to more efficiently produce large batches of purified meta-cresol purple (mCP) and cresol red (CR), the preferred indicators for direct water column determinations of seawater pH. Several batches of unrefined mCP and CR of independent origin were prepared by flash chromatography. Indicator purity was then assessed in two ways: by (a) HPLC verification and (b) pH measurements of highly buffered solutions. HPLC chromatograms of the various flash-prepared mCPs indicated that the process did not always result in a completely pure product. In terms of performance, however - i.e., pH measurements of highly buffered solutions - no differences were observed between an HPLC-purified reference mCP and the flash-purified mCPs. HPLC examination of the flash-purified CRs indicated that every product was free of detectable impurities. No differences were seen in comparative pH measurements made with the purified CRs. The flash chromatography procedures outlined in this work are suitable for producing bulk quantities of mCP and CR for use in high-precision spectrophotometric pH measurements in seawater.
机译：磺酞指示剂盐中的杂质会导致海水pH值测定中的重大错误。为了在全球范围内确保合适的测量精度和可比性，必须从用于海洋CO_2系统分析的所有指标中去除杂质。先前的工作描述了一种有效的HPLC（高效液相色谱）程序，用于纯化间甲酚紫，但该技术劳动强度大，每次HPLC运行仅产生一小批纯化的指示剂。这项工作描述了使用快速色谱法更有效地生产大批纯化的间甲酚紫（mCP）和甲酚红（CR），这是直接水柱测定海水pH值的首选指标。通过快速色谱法制备了几批独立来源的未精制的mCP和CR。然后以两种方式评估指示剂的纯度：通过（a）HPLC验证和（b）高缓冲溶液的pH测量。各种闪蒸制备的mCP的HPLC色谱图表明，该过程并不一定总能得到完全纯的产品。然而，就性能而言，即对高缓冲溶液的pH进行测量，在HPLC纯化的参比mCP和快速纯化的mCP之间没有发现差异。闪蒸纯化的CR的HPLC检查表明，每种产品均不含可检测的杂质。用纯化的CR进行的比较pH测量未见差异。这项工作中概述的快速色谱程序适合于生产大量的mCP和CR，用于海水中的高精度分光光度pH测量。

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