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Technical Questions Forum

Whether you need detailed assistance or quick troubleshooting, Inorganic Ventures, the standardology experts, is here to help. We're eager to assist chemists with hundreds of topics ranging from problem elements to calculations. The links below showcase real-world technical problems along with solutions provided by our in-house experts.

 
Forum Total Topics Total Posts Latest Reply
144 173
Chromium Oxidation State
Hello, I am analyzing a powder for % Cr. The sample is a very dark purple powder, I add HNO3 and HCl and let it sit for an hour to dissolve. I then bring it up to a final weight (final matrix is 2.5% HNO3, 5% HCl). When I am diluting to the final weight the sample is green, indicating Cr is in the 3+ oxidation state. My working and stock standard samples are orange (Cr 6+). Is this ok? I have heard Cr has slow kinetics, how do I know all the Cr is in solution and I will get accurate % Cr for my samples? Thank you,
Posted: 11/16/21 08:01:48
158 166
Odd aluminum results
I'm attempting to determine aluminum in a vitamin/mineral premix matrix using ICP-OES. I've been analyzing replicates in an attempt to determine the precision of my method in this matrix. I've found some odd behavior in the results. It seems like if I analyze the sample digest a short time after digestion, it gives results that are 20 percent higher for aluminum. I looked at 3 wavelengths (308, 394, 396), and they all give similar results. Analyzing the digest right after the digestion gives about 600 ppm. If I wait a few days, the results go down to around 500 ppm. I've tried two different instruments and sets of standards. I'm digesting the samples on a hot plate with about 1:6 ratio of concentrated nitric acid to concentrated hydrochloric acid. The resulting digest is clear with a light yellow color. I tried another mineral premix, and it does not have the same issue. The method I'm using is a multi-element method. It gives the same results for other elements like Co and Cu between the fresh and older digests. It's just aluminum that drops in concentration over time. I know Se and As have issues with carbon enhancement in ICP analysis, but I haven't heard anything about aluminum having issues. Does anyone know what could be causing freshly digested vitamin/mineral premix samples to give high results for aluminum?
Posted: 10/20/21 11:57:07
88 105
Photometry and spectroscopy using IRAF and Pyraf
I have some large amount of fits files which I have to reduce(bias, flat, dark, and removal of cosmics) and then do photometry(both aperture and psf) and spectroscopy (https://docsbay.net/introduction-to-spectroscopy-and-applications). I know all the stuff of how to use iraf and do photometry and spectroscopy. I want to write some script in python which can automate the stuff to a reasonable extent. Can anyone suggest me some website or way how to write some script (in python) using iraf tasks like daophot , apall, apphot, imexam etc. so that I can do my work relatively faster.
Posted: 12/04/21 04:27:18
160 161
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: 12/13/21 13:25:57
13 16
7800 ICP-MS Carrier Gas Readings
While I'm running a batch and doing the initial tune batch there isn't any counts being read for any of my mass's. However under the Tune tab after adjusting the He Flow to 0 I start to read counts for the elements , but once I adjust it back up it reads 0 again. I have checked if sample introduction is the source of the problem, I have cleaned and checked the nebulizer, lines, tuning solutions and that seems to be running fine. I believe my problem lies somewhere else. I have an Agilent 7800 ICP-MS.
Posted: 10/18/21 10:09:08