Ultra inert inlet liners with wool used in GC/MS analysis of drugs of abuse

Inlet liners are of prime importance to the inlet system where the vaporized sample is mixed with a carrier gas before being introduced to the capillary column.

Why are inlet liners with wool commonly used?

Wool lined inlets are commonly used because:-

  • Wool allows for a more homogenous mixing of the sample that allows for more accurate quantitation.
  • Loss of samples is averted by prevention of their fall to the bottom in droplet form. Wool prevents this by trapping the droplets.
  • Wool provides a larger surface area for vaporizing the samples in their liquid forms. It also helps to protect the GC column from the negative impact of sample matrix.
  • Heavy-matrix samples of plasma and urine may deteriorate and damage the performance of the GC/MS system leading to a shorter column life and frequent maintenance. The inlet liner wool can act as a protector of the system.

Limitations of liners with wool

Despite the aforementioned advantages, if the inlet wool liners are not properly deactivated they can cause decomposition as well as adsorption of the analyte solutions for basic drugs of abuse.

Figure 1 below shows that these drugs usually contain hetero atoms that interact with silanol groups (Si-OH) that are present in glass. This leads to further adsorption and decomposition of the compounds leading to broad and ill shaped peaks, ghost peaks, tailing and lower responses.

Glass wool further aggravates this problem due to their larger surface areas and difficulties with deactivation. The importance of adequate and complete deactivation thus cannot be overemphasized in forensic and toxicology applications.

Agilent’s Ultra Inert liners with wool

The Ultra Inert liners from Agilent with its thorough glass wool deactivation process can improve the efficacy and repeatability of the experiment significantly. This is the first time that liners containing glass wool are capable of analyzing basic drugs of abuse using the GC/MS.

For the experiment the standard 28 drug mix of forensic/toxicology check mix was used. The compounds in the mix contained both early and late retention rates and contained different categories of compounds such as alkaloids, amphetamines and benzodiazepines.

Figure 1 shows the chemical structures of the drug components in the mix. Both SCAN and SIM modes were used for the experiment and a 500 ng/ml standard (10X dilution) was used to check for repeatability in over 50 injections.

Experiments

The Agilent GC/MS Forensic/Toxicology analyzer was used to check out and analyze the standard 28 component analyte in order to assess the functioning of Ultra Inert Liners with glass wool.

Testing was conducted using Agilent 7890A GC system that was equipped with a 7683B autosampler and a 5975C MSD.

Results

The results showed that the use of liners tests with the checkout standard resulted in chromatographic analysis problems including lost or poor peaks, distorted peaks, ghost peaks, tailing peaks etc. that led to low sensitivity of the tests. This was due to inadequate deactivation of the liners.

Early eluting compounds such as Phentermine, Methamphetamine, MDMA and MDA had more peak shape problems; whereas the peaks of late eluting compounds, such as Temazepam, disappeared due to loss of sensitivity.

However, the use of Agilent Ultra Inert deactivated liners with wool showed better peaks and higher responses. Further liner to liner reproducibility of the device was also excellent. This was all attributed to the efficient and robust deactivation of the wool.

Summary

The experiment with Agilent Ultra Inert liners with wool revealed excellent inertness required for analysis of drugs of abuse. The liners were found to be capable of detecting and analyzing popular and difficult to detect basic drugs of abuse from the forensic/toxicology mixture.

There is excellent reproducibility of the device with an average of 5% RSD. Further, efficient deactivation of the wool adds to the inertness of the Agilent Ultra Inert liners that improves analysis significantly.

The benefits of the system include uniform or homogenous mixing of samples, uniform evaporation, trapping of non volatile residues, column and detector protection. These benefits are all seen without compromising on the sensitivity of the analysis of the actual chromatography process.

The Ultra Inert liners are thus one of the best choices for screening, detection and quantitation of drugs of abuse.

Further information

About Agilent Technologies

Agilent Technologies Inc. (NYSE: A) is the world's premier measurement company and a technology leader in chemical analysis, life sciences, diagnostics, electronics and communications. The company's 20,500 employees serve customers in more than 100 countries. Agilent offers the broadest range of innovative measurement solutions in the industry. The company's four businesses - Chemical Analysis, Life Sciences, Diagnostics and Genomics, and Electronic Measurement - provide customers with products and services that make a real difference in the lives of people everywhere. And at Agilent Research Laboratories, we conduct research that anticipates customer needs and produces breakthroughs that power growth.. Information about Agilent is available at www.agilent.com.


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Last updated: Aug 20, 2013 at 4:45 AM

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