Perform separate triplicate injections of water, 0, 12 and 25 ppm ethylene glycol standard; 7 injections of 50 ppm ethylene glycol standard; triplicate injections of the
positive control bracketed by triplicate injections of
water and triplicate injections of the
sample.
这是某个
气相色谱试验中关于进样的一句说明,请问“阳性对照”、“水”和“样品”的进样之间存在怎样的关系?句子中的“bracketed by”如何理解?由于本人是这方面的外行,问题难免显得很业余,不过还是希望业内高人不吝赐教!