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Chemical Stability and Compatibility

 
 

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Yittrium count not stable
In an analytical sequence on ICP OES we observed that the internal standard ratio is not stable and it gradually increases with progress in analytical sequence. So for example if I start sequence with Y count ratio as 1 gradually it increases to 1.04. Suprisingly when a new sequence is created with fresh calibration again the Y count ratio comes back to its original value of 1.0.
Created: 11/12/19 06:01:27
Created By: "Chandan Upadhyay"
2 39
Yittrium count not stable
In an analytical sequence on ICP OES we observed that the internal standard ratio is not stable and it gradually increases with progress in analytical sequence. So for example if I start sequence with Y count ratio as 1 gradually it increases to 1.04. Suprisingly when a new sequence is created with fresh calibration again the Y count ratio comes back to its original value of 1.0.
Posted: 11/12/19 10:05:13
Digesting an organic with Os Spike
I am developing a method for a 24 ICH metal analysis of Hydroxypropyl Methylcellulose.  I cannot get Os spikes to recover and I understand it is because we are microwave digesting the sample in HNO3.  From everything I've read on your site and others, the problem is osmium tetroxide formation.  However, the only thing that's going to digest the sample is an oxidizing acid (as far as I know).  I'm sure HClO4 or H2SO4 will be just as detrimental.  I can't get it into solution with just HCl.  Everyone says use an HCl matrix with Os but how do you reconcile that with a need to spike and then digest?  I can't digest in nitric and then dilute in HCl because the sample must be spiked before any preparation steps.  Thanks for any assitance!   Dan
Created: 09/13/19 08:59:10
Created By: "admin"
1 153
Digesting an organic with Os Spike
I am developing a method for a 24 ICH metal analysis of Hydroxypropyl Methylcellulose.  I cannot get Os spikes to recover and I understand it is because we are microwave digesting the sample in HNO3.  From everything I've read on your site and others, the problem is osmium tetroxide formation.  However, the only thing that's going to digest the sample is an oxidizing acid (as far as I know).  I'm sure HClO4 or H2SO4 will be just as detrimental.  I can't get it into solution with just HCl.  Everyone says use an HCl matrix with Os but how do you reconcile that with a need to spike and then digest?  I can't digest in nitric and then dilute in HCl because the sample must be spiked before any preparation steps.  Thanks for any assitance!   Dan
Posted: 11/12/19 13:13:37
Stability of diluted standards
In our preparation for ICP-MS analysis of USP <232> elements, we perform an intermediate dilution of a 14 element blend. This is a 1:20 dilution to give concentrations (ug/mL, ppm) as follows: Cu = 65, Ni = 30, Mo = 9, V = 6, Cd = 0.25, Hg = 0.75, Pb = 0.25, As = 0.75, Ir = 5, Pd = 5, Pt = 5, Rh = 5, Ru = 5, Co = 2.5. I have viewed information at http://inorganicventures.com/stability-elements-ppb-concentration-levels, which has pointed me in the right direction and is the kind of information I’m looking for, except that our intermediate is at much greater concentrations. I am wondering if you can provide any information regarding the stability of this solution in a 5% nitric acid (HNO3), 1% hydrochloric acid (HCl) solution? If possible, I'm also interested in stability information for a 10 ug/L (ppb) mixture of In, Bi, 6-Li, Y, Sc, and Tb in 3% HNO3.
Created: 09/03/18 22:44:13
Created By: "admin"
1 317
Stability of diluted standards
In our preparation for ICP-MS analysis of USP <232> elements, we perform an intermediate dilution of a 14 element blend. This is a 1:20 dilution to give concentrations (ug/mL, ppm) as follows: Cu = 65, Ni = 30, Mo = 9, V = 6, Cd = 0.25, Hg = 0.75, Pb = 0.25, As = 0.75, Ir = 5, Pd = 5, Pt = 5, Rh = 5, Ru = 5, Co = 2.5. I have viewed information at http://inorganicventures.com/stability-elements-ppb-concentration-levels, which has pointed me in the right direction and is the kind of information I’m looking for, except that our intermediate is at much greater concentrations. I am wondering if you can provide any information regarding the stability of this solution in a 5% nitric acid (HNO3), 1% hydrochloric acid (HCl) solution? If possible, I'm also interested in stability information for a 10 ug/L (ppb) mixture of In, Bi, 6-Li, Y, Sc, and Tb in 3% HNO3.
Posted: 09/03/18 22:45:15
Amount of HF in stock standards
I need to know the exact concentration of HF in the CGHF1, CGNB1, and CGTA1 standards and if I can mix the three solutions.
Created: 09/03/18 22:40:00
Created By: "admin"
1 235
Amount of HF in stock standards
I need to know the exact concentration of HF in the CGHF1, CGNB1, and CGTA1 standards and if I can mix the three solutions.
Posted: 09/03/18 22:41:32
Molybdenum and titanium stability; mercury volatility
Are Mo and Ti are stable for any length of time without using HF? Also, what is meant by the term "trace HF"? I also have a question about mercury (Hg).I've noticed that hot block digestions of a clean acid-water matrix with an inorganic mercury standard added to a final concentration of 0.5ug/L, result in mercury recoveries ranging from 75-80%. Is inorganic mercury is volatile enough to explain such a loss?
Created: 09/03/18 22:35:52
Created By: "admin"
1 218
Molybdenum and titanium stability; mercury volatility
Are Mo and Ti are stable for any length of time without using HF? Also, what is meant by the term "trace HF"? I also have a question about mercury (Hg).I've noticed that hot block digestions of a clean acid-water matrix with an inorganic mercury standard added to a final concentration of 0.5ug/L, result in mercury recoveries ranging from 75-80%. Is inorganic mercury is volatile enough to explain such a loss?
Posted: 09/03/18 22:38:16
Contaminants of ethanol in HDPE
We're working on a health problem that we assume was caused by an unidentified contaminant in ethanol. The ethanol was 96%, shipped in 50 gallon HDPE barrels, and then diluted with water to 36% for drinking. We wonder if a possible source for a toxic contaminant might be a substance in the polyethylene matrix. What substances present in HDPE could be leached out by 96% ethanol?
Created: 09/03/18 22:31:06
Created By: "admin"
1 204
Contaminants of ethanol in HDPE
We're working on a health problem that we assume was caused by an unidentified contaminant in ethanol. The ethanol was 96%, shipped in 50 gallon HDPE barrels, and then diluted with water to 36% for drinking. We wonder if a possible source for a toxic contaminant might be a substance in the polyethylene matrix. What substances present in HDPE could be leached out by 96% ethanol?
Posted: 09/03/18 22:33:42
Lead (Pb) instability in HNO3
I am using CGPB1, a 1000 microgram/ml Pb standard, and I made up a set of standards to test for Pb in some water samples. My standards were 1, 0.5, 0.1, and 0.01 ppm. I acidified them with 2% v/v HNO3, the remainder being DI water. The standards seem to be extremely unstable, I can't get even a single sample run through my ICP with them. Any thoughts?
Created: 09/03/18 22:28:18
Created By: "admin"
1 105
Lead (Pb) instability in HNO3
I am using CGPB1, a 1000 microgram/ml Pb standard, and I made up a set of standards to test for Pb in some water samples. My standards were 1, 0.5, 0.1, and 0.01 ppm. I acidified them with 2% v/v HNO3, the remainder being DI water. The standards seem to be extremely unstable, I can't get even a single sample run through my ICP with them. Any thoughts?
Posted: 11/12/19 11:48:22
Starting materials for Kjeldahl nitrogen, COD, and suspended solids
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?
Created: 09/03/18 22:25:25
Created By: "admin"
2 199
Starting materials for Kjeldahl nitrogen, COD, and suspended solids
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?
Posted: 09/03/18 22:29:54
Stability and changes in certified values with time
I would like to know about the stability and the possible change in concentration with time expected for your certified standards?
Created: 09/03/18 22:22:34
Created By: "admin"
1 203
Stability and changes in certified values with time
I would like to know about the stability and the possible change in concentration with time expected for your certified standards?
Posted: 09/03/18 22:24:03
Element ratios between standards and samples for soils and seeds
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).
Created: 09/03/18 22:19:58
Created By: "admin"
1 176
Element ratios between standards and samples for soils and seeds
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).
Posted: 09/03/18 22:21:09