主题：【求助】请教大虾：如何从质谱的mzXML格式文件中获取离子价态信息！

我拿到的这套质谱数据格式为mzXML文件，我们可以从文件中获取离子的保留时间，碰撞能量，质谱质荷比强度等信息，但是怎么知道其离子的价态呢？请高人指点。先在此谢过！bow！其主要内容如下所示：
  <scan num="5"
        msLevel="2"
        peaksCount="44"
        polarity="+"
        retentionTime="PT5.99S"
        collisionEnergy="35"
        lowMz="130"
        highMz="1050"
    basePeakMz="298.751"
    basePeakIntensity="776428"
    totIonCurrent="1.61869e+006">
    <precursorMz precursorIntensity="54">518.8</precursorMz>
    <peaks precision="32"
          byteOrder="network"
          pairOrder="m/z-int">Qz5JDkVjkABDXvFCRf6gAENuzCBGt0wAQ31DcETs4ABDhYWqRTggAEOMiDxIDTMAQ41dNEbuMgBDlHhIRne0AEOU0vJGGYAAQ5VgKkk9jsBDlcA2RIoAAEOWb5hESAAAQ6DabEXusABDqnikRdYoAEOyvXhFmjgAQ7NEoEcYHABDvVyARaUoAEPDfMRFsEgAQ8WkfEUCUABDxvXCRY6wAEPPfQpGxxQAQ9iKFkWwuABD3lewRWRQAEPlTVJGCAAAQ+YHXETRwABD5u2+RN1AAEPrvLJFP3AAQ+w7LEX92ABD7KXYRNFAAEPw+/hFoDgAQ/R5BkTSoABD9aqURjUAAEP6dfxEsWAAQ/sexEaFmgBD+3SOSLtvAEP7zMw/gAAAQ/5fdEZc3ABEAaw0RL5AAEQFyYZFKRAARAhCyEURcABEDyEMRfgwAEQWICBFmFAARDQaAEWnGABETlzsRYEQAA==</peaks>
  </scan>