Advertisement

Internal Standard calculations with Agilent OpenLab CDS

Discussions about GC and other "gas phase" separation techniques.

3 posts Page 1 of 1
I am in the process of resurrecting a GC method from a former co-worker. The method uses 3-Pentanol as an IS. In the software, for the processing method, there is a data field for entering a value for the internal standard.
I have a 30,000 mg/L 3-Pentanol standard. The sample prep calls for 10uL of the IS to be added to 1.0 mL of each standard and each sample (total volume of every standard & sample = 1010 uL). The value I was told to enter in the software is 300. The units for the method are mg/L. It would seem to me that I should be entering the net mg/L of the IS in the samples & standards. The dilution factor for the samples is 1.01.
By my math, I am adding 0.3mg of sample in 10uL to 1.0 mL of sample, which gives a net of ~300 mg/L (corrected by the dilution factor). We are using OpenLab CDS, but I'm sure all chrom software computes the same way.
"I have a 30,000 mg/mL 3-Pentanol standard."

Then you are either an alchemist or a magician.

You need to study up on the SI units, their multipliers, and not using excessive trailing zeroes to express quantities.
Peter Apps
"I have a 30,000 mg/mL 3-Pentanol standard."

Then you are either an alchemist or a magician.

You need to study up on the SI units, their multipliers, and not using excessive trailing zeroes to express quantities.
Ahh, thanks for the catch. I meant 30,000mg/L. We generally write it this way for the method. The rest of the analytes are prepared anywhere from 50mg/L to 2000 mg/L, and including the zeros is preferred.
3 posts Page 1 of 1

Who is online

In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 4374 on Fri Oct 03, 2025 12:41 am

Users browsing this forum: No registered users and 1 guest

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry