Specifically I want to know about a standard solution (1,2,3,4,5 ppb) preparation of Mercury from Mercury stock solution (1000ppm).
Use the standard dilution formula in general chemistry, i.e., Volume(1) x Concentration(1) = Volume(2) x Concentration(2). Make sure all your units are the same. Thus, you can either change 1000 ppm to ppb (1000 ppm x 1000 ppb/1ppm) = 1000000 ppb or you can change the ppb needed to ppm. So, you have a stock solution of 1000000 ppb (concentration 1), and you want to know what volume(1) to dilute to make a stock solution of whatever volume you want (for example 100 mL). Thus, if you want 5 ppb, the formula is ? mL(1) x 1000000 ppb(1) = 100 mL(2) x 5 ppb(2). Solve for ? and you have the volume you should add to a 100 mL volumetric flask. Bring it up to volume and you're good to go. Note that this formula is universal but from a practical aspect you would only be pipetting 0.0005 mL of your stock to get your 5 ppb. Thus, using a 1000 ppm stock to start is not practical. I suggest that you make a 1 ppm stock and start from there. Take 0.1 mL of your 1000 ppm stock and dilute it to 100 mL (use a volumetric flask for accuracy and convenience). Then, re-run the calculation using the dilution formula. To avoid waste, and depending on the volumes you need, you can proportionally cut the volume of all your stocks.
Remark: Besides the straightforward dilutions and calculations don’t forget the storage stability of those very dilute standard solutions. Adsorption and/or ion-exchange at the walls of your volumetric containers may diminish the actual concentration with time. Thus, use only fresh diluted standards in quartz or Teflon-based containers which have to be cleaned before by special procedures known in the field of ultra-trace analysis. Especially mercury is known to be difficult to determine without a clean bench (one broken thermometer in years before in the lab can increase your reagent blind signal).
just following up on the 2 previous comments:
to my knowledge, the most detailed description for Hg analysis in aqueous solutions is given in the US EPA method 1631 (http://water.epa.gov/scitech/methods/cwa/metals/mercury/index.cfm). There is a specific section on standard solution preparation, including materials to be used, handling, stabilization and storage capacity. From my experience, if you do not acidify enough (~pH 1; e.g. 0.4% HCl, v:v) most Hg present in the solution will indeed adsorb to the bottle wall, but any acidic solution will pick up Hg over time. Even Teflon is permeable for Hg, best is probably PFA-Teflon rather than FEP-Teflon. Glass/Quartz is best, but every time you will open your bottle, the solution will also slightly pick up Hg present in the air. in case you break such a glass/quartz bottle containing a concentrated Hg standard solution, you will need to look for a new lab room...
just following up the previous comments,
and always use this formula for all dilution ;
Use the standard dilution formula in general chemistry, i.e., Volume(1) x Concentration(1) = Volume(2) x Concentration(2).
Make sure all your units are the same.
kind regards
(Stock concentration) X (Stock volume required) = (Concentration needed) X (The volume of final dilution)
Here,
1000 ppm x ? = 1ppm x 1000 ml
? = 1 ml from the stock in a 1000 ml distilled water
Use dilution law, just make sure the stock solution is well prepared. Add a desired mass of NaF in a distilled water to make 1000ppm. From this stock solution then you can prepare a range concentration using dilution law.
Dilute the std solution to 100 pm or 10 pm using formula N1V1=N2V2 and again follow the serial dilution of that solution to 1,2,3,4,5 pm using same formula
