Do you have application notes about siloxane analysis in GCMS? octamethylcyclo-tetrasiloxane (D4), decamethylcyclo-pentasiloxane (D5), dodecamethylcyclo-hexasiloxane (D6), dodecamethylcyclo-hexasilane (D6_silane)

specifically what are ms ions? because I get different results in my analysis.

  • Hi

    what are the ions you get

    try to. scan for higher concentration to avoid interaction with column siloxanes ( thermal. desorpation.)

    also use new HP 5MS column (15 m 0.25 mm I.D. 0.25 mm film
    thickness; Agilent Technologies).

    install a new deactivated liner

    do a blank run( no injection) to watch any contamination in the inlet system

    then try this oven program
    consisted of 50C (3 min hold)

    10C/min to 160C 
    40C/min to 250

    flow 1.5 ml/min. He constant flow

  • Hi Mohammed,

    Firstly,  scanned the analysis and found sim ions. However, the ions I found were not those in the literature. My client didn't believe it either. but later today I realized that my customer received the wrong standard. I am still there right now.
    He bought the product with the C13 isotope.
    So thanks for your response.

  • 1.5 ml/min into the MS is higher than optimum. The optimum range for helium is 0.8 to 1.4 ml/min and for hydrogen is 0.4 to 0.8 ml/min.

    Lower flows are difficult to get on a 15 meter 0.25mm id column as the inlet pressure gets below 5 psi.  I would suggest a 30m x 0.25mm id column or a 20m 0.18mm id column.  >= 5 psi inlet pressure and >=20ml/min total flow is necessary for decent gas control in the inlet and column.

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