Herb pesticides analysis with GC-ECD/NPD-FPD

[Tomislav]

Hi everyone,

I’m owner of a small company in Croatia that will produce different kinds of herbal essential oils and cream-like products. Duo to necessity to control quality of my raw material and final product, i decided to invest in GC. According to the European Pharmacopoeia, max. allowed level of organochlorine, organophosphorus and other pesticides residuals are low as 100 ppb. I don’t have the money to buy GC-MS, but rather want to employ GC with ECD and maybe NPD/FPD detector. I have only theoretical and for now, little practical knowledge about GC. My goal is to be able to be able have LOQ at least 10 ppb or lower for all individual pesticides from organochlorine, organophosphorus, organosulfur and other group. My questions are:

1) Does ECD will be sufficient even for organophosphorus and other compounds besides organochlorine, or NPD or FPD need to be coupled with ECD to achieve very low LOQ and good response?

2) For pesticide conformation purpose, does it possible to run system with 2 columns (2D) in analysis with ECD and NPD/FPD detectors?
Kind regards,
Tomislav

[James_Ball]

Hi everyone,

I’m owner of a small company in Croatia that will produce different kinds of herbal essential oils and cream-like products. Duo to necessity to control quality of my raw material and final product, i decided to invest in GC. According to the European Pharmacopoeia, max. allowed level of organochlorine, organophosphorus and other pesticides residuals are low as 100 ppb. I don’t have the money to buy GC-MS, but rather want to employ GC with ECD and maybe NPD/FPD detector. I have only theoretical and for now, little practical knowledge about GC. My goal is to be able to be able have LOQ at least 10 ppb or lower for all individual pesticides from organochlorine, organophosphorus, organosulfur and other group. My questions are:

1) Does ECD will be sufficient even for organophosphorus and other compounds besides organochlorine, or NPD or FPD need to be coupled with ECD to achieve very low LOQ and good response?

2) For pesticide conformation purpose, does it possible to run system with 2 columns (2D) in analysis with ECD and NPD/FPD detectors?
Kind regards,
Tomislav

It is definitely possible to run two detectors and two columns, and you don't have to do any special 2D type work. You can either inject into one injection port and split the flow into two columns each connected to a different detector, which is the least complicated way, or inject into one column and split into two detectors. The second option has problems in that you have to use restrictors to maintain the proper flow between the two detectors. The first option works quite well and is easier to balance the flows, just use the same diameter and length for both columns and the flow will be evenly split between the two.

Another option that is more sensitive is to use two columns and two injectors and inject both at the same time, this way all of the sample goes to each column with no splitting so the response will be nearly double as either of the above options, it just requires two injector setups which is a little more expensive.

This is the kit we use when doing the first example, one injection and two columns/detectors

https://www.restek.com/catalog/view/7655

[uzman]

Hi Tomislav ,

I have an Agilent 6890N for sale ; if interested.
It has dual S/SL injector , µ-ECD and NPD detectors , and in good condition.
Computer with chemstation A10.02 software included.

[Tomislav]

Hi everyone,

I’m owner of a small company in Croatia that will produce different kinds of herbal essential oils and cream-like products. Duo to necessity to control quality of my raw material and final product, i decided to invest in GC. According to the European Pharmacopoeia, max. allowed level of organochlorine, organophosphorus and other pesticides residuals are low as 100 ppb. I don’t have the money to buy GC-MS, but rather want to employ GC with ECD and maybe NPD/FPD detector. I have only theoretical and for now, little practical knowledge about GC. My goal is to be able to be able have LOQ at least 10 ppb or lower for all individual pesticides from organochlorine, organophosphorus, organosulfur and other group. My questions are:

1) Does ECD will be sufficient even for organophosphorus and other compounds besides organochlorine, or NPD or FPD need to be coupled with ECD to achieve very low LOQ and good response?

2) For pesticide conformation purpose, does it possible to run system with 2 columns (2D) in analysis with ECD and NPD/FPD detectors?
Kind regards,
Tomislav

It is definitely possible to run two detectors and two columns, and you don't have to do any special 2D type work. You can either inject into one injection port and split the flow into two columns each connected to a different detector, which is the least complicated way, or inject into one column and split into two detectors. The second option has problems in that you have to use restrictors to maintain the proper flow between the two detectors. The first option works quite well and is easier to balance the flows, just use the same diameter and length for both columns and the flow will be evenly split between the two.

Another option that is more sensitive is to use two columns and two injectors and inject both at the same time, this way all of the sample goes to each column with no splitting so the response will be nearly double as either of the above options, it just requires two injector setups which is a little more expensive.

This is the kit we use when doing the first example, one injection and two columns/detectors

https://www.restek.com/catalog/view/7655

Dear James,

Thank you for your answer. Can you tell me if ECD will be sufficient to establish LOQ of 0,1 ppm and lower for organophosphorus and other non-organochlorine pesticides?

Best Regards,
Tomislav

[James_Ball]

Our lowest standard is 0.02ppm injected on the instrument, with analytes of Endrin, DDT, Heptachlor, Propachlor, Trifluralin and others. We see these when using a 10:1 split injection so can go even lower with splitless injection. The final LOD for your sample would depend on the extraction initial and final volume.

On the ECD the organophosphorus type analytes will respond with less sensitivity. Atrazine and Simizine, ect are much better with the NPD.