TD/GC-MS detection issue?

[SCornford]

Hi all, this is my first post so please be kind!

I'm running a Markes thermal desorber attached to an Agilent 5879 GC/MS. My target compound is di(ethylhexyl) phthalate. The problem I'm having is that I can't detect it. I've tried various parameters, even the suggested parameters in the Agilent column selector guide. I can see the standard on our liquid injection system, so I'm erring towards suspecting the thermal desorber parameters. I have sought advice from the manufacturers and are using their suggested paramters.

Is it as simple as the technique is unsuitable for the analysis of DEHP in air?

Many Thanks.

[Johnny Rod]

If you can inject it manually and see it then the GC side is working, so I'd turn my attention to the TD side. Have you got info from the TD supplier on a method to use? How are tou trying to get your sample from the bottle into the TD kit?

[SCornford]

I've been given parameters for the TD which I have used with no sucess. I currently have on a mixture of C7-C30 lakanes to give me an indication of the high mass compounds coming off. The chromatography is awful the higher the compound, so I have increased the column flow to 3mlmin-1.

The standards are injected directly onto the tube for purge and trap in the TD system.

[AICMM]

It has been a long time since I was involved in this type of work, but on the particular project I worked on, we found that desorption flow was critical to get the heaviest compounds off. Waddell, et al., Jrnl of Chrom A, 1062 (2005), 125-131) We used 285 mL min-1 to desorb the sample to a cool inlet then ramped the inlet onto the column.

Best regards,

AICMM

[SCornford]

It has been a long time since I was involved in this type of work, but on the particular project I worked on, we found that desorption flow was critical to get the heaviest compounds off. Waddell, et al., Jrnl of Chrom A, 1062 (2005), 125-131) We used 285 mL min-1 to desorb the sample to a cool inlet then ramped the inlet onto the column.

Best regards,

AICMM

That's a great help, thank you very much!!

[JI2002]

The b.p. of the compound is 385C. It's not suitable for TD-GC/MS. What method are you following to analyze di(ethylhexyl) phthalate? I don't understand why you chose this technique for analyzing di(ethylhexyl) phthalate in the first place.