Syringe Basics for Chromatography
From sample preparation to sample injection, syringes cover a range of uses in every chromatography lab. But with so many types and options available, how do you know which one to choose?
In this Restek Tip, we guide you through a straightforward decision-making process to help you choose a new syringe.
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From sample preparation to sample injection, syringes cover a range of uses in every chromatography lab. But, with so many types and options available, how do you know which one to choose?
In this Restek Tip, we’re going to guide you through a straightforward decision-making process to help you choose a new syringe.
We recommend you start with considering your application.
Does it require an autosampler or a manual syringe? While they can sometimes be interchangeable, there are often differences in the needle point.
Autosampler syringes tend to have a heavier gauge and a conical point, whereas manual syringes often have a thinner gauge needles and a beveled edge. You may also require a specific gauge and point, such as when using a Merlin Microseal.
Next, consider whether you need a gas-tight or a liquid syringe.
Before we look at each, note that both gas-tight and liquid syringes are compatible with liquid injections.
Gas-tight syringes prevent the passage of gas and liquid past the plunger tip. They also tend to work better at drawing up liquids—viscous ones in particular. Additionally, they have the advantage of the plunger tip—often PTFE—being replaceable.
Liquid syringes on the other hand are generally more affordable than gas-tight syringes. However, because of the tighter tolerances needed, they are more prone to seizing due to particulate matter getting stuck between the sides of the barrel and the plunger.
Unlike the PTFE tips on gas-tight syringes, plungers for liquid syringes are not replaceable. If the plunger seizes or bends, the whole syringe will need to be replaced.
After selecting a syringe type, you need to choose a suitable termination – do you want a fixed or removable needle?
Removable needles can be useful if you are working with samples that could clog the needle. If this happens, instead of replacing the whole syringe—which could be costly—you would only need to replace the syringe needle.
Syringes with cemented needles are generally cheaper to purchase, but they also introduce the possibility of interference from the cement interacting with certain solvents.
Specialty terminations also exist for specific applications. For example, a 5 mL syringe with a Luer tip could be used for injecting samples into a purge and trap system. If you require a specialty termination, we recommend you reference a manufacturer’s selection guide, or contact Restek’s Technical Service.
Finally, you need to select a needle gauge and a point style.
The gauge is largely determined by the syringe size, with the larger the syringe volume dispensed, the thicker the needle. In the case of autosampler syringes, there are usually two gauge options within a given syringe size, as well as a hybrid option on some syringes.
When choosing between gauges, a heavier one is recommended when strength is important, like piercing septa with a fast injection technique. Thinner gauges can also pierce septa and are more effective in reducing coring, however they require a gentle insertion technique to minimize damage to the needle.
Point style is partially determined by the other choices like your application and whether it’s an autosampler or manual syringe.
Some point styles are better for sample pipetting, while others are great at penetrating septa while minimizing coring. Syringe selection guides can help you select the right point style for your analysis.
And that’s what you need to know to choose a new syringe. If you have any questions, please contact us at restek.com.
Thank you for joining us for this Restek Syringe Tip!