网友的这两个句子，没有根本区别：

Herein, all chemicals used for this study were analytical reagent grade or better.

Herein, all chemicals used for this study were of analytical reagent grade or better.

这是省略 of 的用法。of 与 age, colour, length, width, depth, height, shape, size, thickness, material, quality,grade, level 等表示大小、长短、深浅、重量、年龄、颜色、材料、高度、形状、质量、等级、水平等的词连用时，常可省略。

    When I was (of) your age,I supported myself.我是你那么大时，自食其力了。

    （Of） What colour is your shirt？你的衬衫是什么颜色的？

    The two pairs of shoes are （of） the same size.这两双鞋号码一样大。

    The twins are (of) the same height.这对双胞胎一样高。

    The door is (of) a dark green.这扇门是深绿色的。

    These goods are (of) good quality.这些商品质量很好。

此外，网友对第二条的理解基本正确。又如：

be of importance =

1. have importance

2. be important