It has been a busy few months since my last posting. You know how it goes: I kept meaning to post to the blog, but could never find the time. Well, I still don't have the time, but oh well. Some things are more important that school work. Like procrastinating.
My last few blogs have been reviews of various articles related to silica dissolution methods. Not exactly great reading material, but nevertheless important for my research. Since then, I have continued reading plenty of articles in my attempt to perfect (or at least get a little better at) my own particular dissolution procedure. I have decided to pursue an 85 C water bath dissolution method similar to that outlined by Sauer et al. To that end, I purchased a used water bath on ebay. The nice thing about this particular water bath is that it is also an orbital shaker. Thus, my samples will not only be heated, but also will be agitated. This is a big step, and should greatly speed up dissolution. I have found that using a 0.2 M NaOH solution works best, and have thus far had good results.
I have run into several sticking points however. First is the issue of silica contamination from glassware. The use of glass pipettes, volumetric flasks, etc. can greatly influence the amount of silica actually in the sample. This is especially bothersome since I am working with dissolved silica amounts in the neighborhood of 10 micrograms (0.0000010 gram). Any contamination from glass can greatly influence this. To get around this problem, I have been using as little glassware as possilbe. For example, I have purchased a digital pipette which uses plastic pipette tips instead of glass. I am still forced to use glass volumetric flasks when I add reagents to the silica sample (this is a step used to "color" the silica, so its concentration can be determined). To mitigate contamination in this step, I never add the silica sample to a dry flask. Instead, I always make sure that there is water in the flask to dilute the silica before it comes into contact with the glassware. On top of this, the silica sample is not left in the flask any longer than is necessary. Undoubtedly, there is some silica contamination. But as long as I am consistent with my procedures (i.e. each sample spends the same amount of time in the flasks), any variation in the data should be mitigated.