Manual syringe injection is the most popular gas chromatography sample injection practice adopted in laboratories across the world. The obvious reason for this choice is convenience and low price of syringes. However, keep in mind that it may take considerable time to perfect the skills required to inject volumes with high accuracy and precision. Bear in mind that it is even more challenging task as you would be required to handle volumes in μl range. Perfection should be a desired objective and in an earlier article some useful tips were forwarded for improving accuracy and precision of gas chromatography injections .
In case you exercise the required care it is possible to achieve precision levels around 1% RSD with manual syringe injections. Fortunately, two more options of sample injection are available which include gas sampling valves and autosampler s for making precise sample introduction. Such devices offer manifold advantages over manual syringe injections. The advantages of automated injection are presented in this article.
Autosampler Injection Benefits
Today several analytical instruments offer automation features but the benefits offered in gas chromatography deserve special mention
Repeatability of Injection Volumes
Autosampler permits highest degree of reproducibility of injected sample volumes. The required volume can be programmed in advance through the system software and offers freedom from human errors and bias.
The number of repeat injections can be decided in advance on the basis of analysis requirements. The software repeats the injections as per set program and there is little scope of loss of count on number of injections.
The autosampler tray has several slots which are numbered. The autosampler selects the vials in a programmed sequence and injections, including number of repeat injections, are made in accordance. The sequence of sample injection is programmed in advance but options are available to accommodate priority samples
It is important to avoid contamination of syringe from earlier samples analysed. The number of wash cycles and their sequence can be programmed to meet the analysis requirements.
Injection of Standards
Standard injections in between sample injections are important in order to ensure the system is performing as per its specifications. The software helps program the standard injection sequence in between sample injection runs
Number of Samples
Autosampler has capacity to accommodate large number of sample vials in each sequence so it is very convenient to run several samples which require identical analysis conditions through a program which can be set at the start of the run.
After loading the samples and standards and setup of analysis sequence you are free to perform other laboratory tasks. Even overnight unattended operation can be set and this leads to several fold increase in laboratory productivities.
The benefits covered in the article will convince you on the advantages that can be derived from automated analysis. It is difficult to imagine analysis of hundreds of samples in refineries, pharmaceutical and food manufacturing industries and commercial product testing laboratories without automated sample introduction. Automated injection in GC analysis is a great time saver which can help you to take fast corrective decisions in manufacturing operations and to increase your laboratory throughputs.