Chemical Stability and Compatibility

I need information for standards for Total Nitrogen (Kjeldahl), COD, and Total Suspended Solids. For Total Nitrogen we combine two stock standards of 1000 mg/L N solution made from Potassium Nitrate, and 1000 mg/L N made from Ammonium Sulfate in equal parts and use this to make standards. For the QC we use a 1000 mg/L N solution made from Nicotinic acid. What starting materials do you use to prepare your stock products for these analytes? For COD we have 3 solutions that are all made from KHP, and for TSS we have a stock standard of 200 mg/L. What starting materials do you use to prepare your stock products for COD and TSS?

I would like to know about the stability and the possible change in concentration with time expected for your certified standards?

I am a graduate student looking to acquire a custom multielement standard for my project, which is looking at the relationship of the metal content of the soil profile and plant seed material in order to determine the region at which the seed was sampled from. I intend to most of the analysis on an ICP-MS instrument and maybe an ICP-OES for the major elements, so ideally I want a multielement standard which contains: Mg, Al, Ca,Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Rb, Mo, Cd, Sn, Sb, Ba, Hg, and Pb. When designing a multielement standard, is it better to make up all the analytes at the same concentration, or vary their concentrations to trends you expect to see? (eg. I'd expect the Mg, Fe, Al and Ca content of the soils to be much larger than the seeds).

Some ICP standards are specified as preserved in HNO3 and trace HF, such as molybdenum and titanium in multi-element mixed standards. Can you provide more information about the actual concentrations of HF used by Inorganic Ventures?

I am curious about Inorganic Ventures' stability studies, and wondering how stable a 10 µg/mL Hg solution would be after it's been kept in a plastic bottle for 5 weeks. I also would like to know what the correlation between Hg concentration and stability would be.

Why is the calcium ICP standard in 0.1% HNO3 instead of the more typical 2%?

I am writing with regards to some issues I am having with a standard that contains: Ag: 10 ug/ml, Al: 125 ug/ml, As: 10 ug/ml, Ba: 10 ug/ml, Ca: 200 ug/ml, Cd: 10 ug/ml, Co: 10 ug/ml, Cr: 100 ug/ml, Cu: 100 ug/ml, Fe: 200 ug/ml, Hg: 25 ug/ml, K: 200 ug/ml, Mg: 200 ug/ml, Mn: 20 ug/ml, Mo: 40 ug/ml, Na: 200 ug/ml, Ni: 100 ug/ml, Pb: 200 ug/ml, Sb: 20 ug/ml, Se: 10 ug/ml, Sn: 25 ug/ml, Ti: 25 ug/ml, Tl: 10 ug/ml, V: 100 ug/ml, Zn: 100 ug/ml, The standard is in a 5% HNO3 / trace HF / trace tartaric acid matrix and is packaged in a polypropylene bottle. I have tried multiple matrices when preparing my diluted calibration standards: 5% HNO3 did not work as the concentration of mercury was too high at low ppm (2.5 ppm). The only matrix that worked okay for mercury was a 5% solution made of 4 mL HNO3 and 1 mL of HCl in a 100 mL of water. This was the only solution that was stable for mercury, however Na wouldn’t work at low ppm (1 ppm) as recovery was 10% for our checks. I am out of ideas and we are trying to use a calibration that works for all the elements. I was wondering if you would have any ideas of a matrix that would work at high and low concentrations for all the elements and that keeps them stable?

I have a question regarding the stability of a blend made up of 1000 ppm Cd, Pb, and Cu. Will this solution be stable for the same amount of time as the individual standards?

Is it safe to mix hydrochloric acid (36%), phosphoric acid (45%) and oxalic acid (5%) in a water solution?Can you recommend a gel in which the mixture could be suspended to make application possible by brush?

I recently bought some individual standards from IV including Os at 100 ug/mL. I was planning on making an intermediate standard in a 2% HNO3 / 0.5% HCl acid matrix. This will be a multi-element standard at varying concentrations. I'm concerned about the OsO4 formation but I'm wondering if the presence of the other elements along with the 0.5% HCl will minimize this formation.The other elements will be As @ 0.15 ug/mL, Cd @ 0.05 ug/mL, Pb @ 0.10 ug/mL, Hg @ 0.15 ug/mL, Cr @ 2.5 ug/mL, Cu @ 25 ug/mL, Mn @ 25 ug/mL, Mo @ 2.5 ug/mL, Ni @ 2.5 ug/mL, V @ 2.5 ug/mL, Pd @ 1.0 ug/mL, Pt @ 1.0 ug/mL, Os @ 1.0 ug/mL, Rh @ 1.0 ug/mL, Ru @ 1.0 ug/mL, and Ir @ 1.0 ug/mL, This will be used for ICP-MS analysis (specifically the new heavy metals method). The 2% / 0.5% solution is what I hope to introduce to the instrument so I suppose the intermediate standard can be made in HCl only?