How to clean Isomist

Hello Agilent community,

1. we have measured organic standard and samples diluted by kerosene with isomist (Agilent ICPOES 5800). Now we try to measure some methanol samples. Also with isomist. How can I clean the isomist properly? Kerosene and methanol are incompatible. Thanks a lot.

2. To measure the methanol samples, which standard should I order? Thank you!

Best regards

Sophia

  • Hello , thank for sharing this question.

    One suggestion is to use an intermediary solvent in which kerosene and methanol are miscible. Some options are 1-butanol or maybe tert-butanol. Try the solubility before applying to the Isomist. If it does not work, you could try using an non-ionic detergent to clean out the kerosene, then rinse a lot with Type 1 water and then insert methanol. You should do this with the system disconnected from the torch, to avoid the tertiary aerosol reaching the plasma.

    As for methanol samples, you should definitely go with the volatile solvent sample intro kit (0.8 mm ID torch , Isomist temp around -5°C and peristaltic pumping at 8-10 RPM), otherwise you will likely extinguish the plasma, if introducing it directly. One option is to dilute the samples in HNO3 1% (maybe 10x), and use aqueous standards in your calibration curve. To avoid accuracy problems due to sample transportation, I recommend the use of internal standardization using Y at 5-10 ppm using a "Y" piece (maybe white/white for samples and orange/white tubing for the IS, with a double pass SC). Remember that diluting the samples 10x will increase your LOQ 10x, so evaluate carefully if this is a valid alternative to your routine. Diluting it 10x you may be able to run the methanol samples just as aqueous (without the need of Isomist and with the standard intro kit).

    Hope this helps,

    Rodolfo

  • Thanks a lot for your explanation. We have Isomist but with a 1.4 mm ID torch. If I try to use 1.4 mm ID torch und Isomist  -5°C, could you please suggest, what kind of standard solution should I use? Aquous standards diluted by methnol or ethanol,  injected by Isomist with temperature -5°C? Or maybe I can use aquous standards diluted by 1% v/v HNO3 directly? With aquous standards diluted by 1% v/v, I am worried that with the 1.4 mm ID torch we can not get teh accurate results.

    For the methnol samples, do I need addition of oxygen? I think the methanol sample will not build up much carbon in the torch. I will try.

    Thank you very much!

  • Hello Rodolfo,

    I just checked, we have bought the 0.8 mm ID injector, which should be used with Isomist together for organic samples. I will rebuild it.

    For the standard, mult-elements in hydrocarbon oil and methnol/ethanol are not miscible. Do you have any idea, which solvents can I choose? Or how to use the aquous standards? Thank you very much!

  • Hey ,

    If you are going to directly introduce methanol, you can prepare your calibration curve using an ultrapure methanol as solvent and add the aqueous standards by weight, just like when you prepare standards for other organic samples, since methanol and water have different densities.

    You can check this app note where methanol were analyzed by the 4200 MP-AES: https://www.agilent.com/cs/library/applications/5991-6469EN_4200_MP-AES_methanol.pdf

    They used aqueous standards to prepare the analytical curve.

    Best regards,
    Rodolfo

  • Hi Rodolfo,

    thank you so much for you quick reply. It is very helpful to me!

    I have one more question, except methanol samples. We still have M15 (15% methanol mixed with gasoline) samples. Should I also use the volatile solvent sample intro kit (0.8 mm ID torch , Isomist temp around -5°C and peristaltic pumping at 8-10 RPM), like you suggested for methanol sample?

    How to prepare the standard for M15? Could you please give me a suggestion? It is not easy to find a solvent, for methanol, gasline and hydrocarbon oil (standard)...

    Best regards,

    Sophia

  • Hey , I am happy that the information is being useful!

    As for the M15, since you have gasoline in it, I would try using ultrapure isooctane to dilute the samples. Recently I have performed a demonstration for naptha samples and this was the best approach to reduce the final mixture volatility. I believe you will achieve good results. Depending on the elements you are quantifying, you should take care to choose the proper isooctane to avoid high CPS in the blank solution.

    The same recommendations for the sample intro system and operational conditions are valid, as you mentioned. As you have gasoline, maybe the use of Viton tubing is necessary. I would give it a shot and run with the Solvaflex tubing first (the yellow one).

    Calibration curve in this case should be done with isooctane and organic standards, by mass, and you could dilute the samples 2x by mass. I would use Y as internal standard to correct transportation effects, and you can find it in organic form. Try using it around 5-10 ppm using a "T" piece or add the same amount in every solution (blank / standards / samples).

    Best regards,
    Rodolfo

  • Thank you for your detailed explanation. I will try it as you suggested.

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