Hydraulic presses – also known as Bramah presses – are used to produce solid samples for analysis by infra-red spectroscopy.
FTIR (Fourier-transform infrared) spectroscopy is an analytical technique which determines a sample’s molecular structure.
One way to prepare a sample for this analysis is to dilute it in a material such as potassium bromide (KBr) and then use a hydraulic press to condense it into a solid pellet.
FTIR will compare light passing through the system, with and without the sample in place. Using too large a sample will block the path of the light, reducing the total throughput to zero – making the comparison unreliable. Since KBr is transparent to infrared light, making a KBr pellet (usually containing just 1% sample by weight) can be a practical method of getting the right amount of sample in the system.
To make a pellet, the sample is mixed with the potassium bromide and ground to a fine powder using a pestle and mortar. It is then put inside a durable container called a ‘pellet die’, which uses an internal plunger to compress the sample. When a load of several tonnes is applied to the plunger using the hydraulic press, it solidifies the powder into a disc, which can then be placed inside the spectrometer for examination.
The hydraulic press makes producing these discs quick, easy and repeatable, for reliable and efficient test conditions.
What is a hydraulic mini press?
A hydraulic mini press is a smaller, lightweight version of a full-sized hydraulic press.
They often weigh around 4 kilos, but can still accurately apply 2 tons of pressure, just by turning a handle. They typically produce smaller pellets – 7 mm diameter rather than the more usual 13 mm diameter – which enables an equivalent pressure to be applied despite the lower tonnage.
They’re often found in pharmaceutical labs, polymer testing labs, undergraduate chemistry labs and many other places where FTIR is commonplace.
Why use a hydraulic mini press rather than a full-sized press?
Standard-sized hydraulic presses are manually hand-pumped. Mini presses reduce the physical effort required, as well as needing less space to use and store. A mini press can easily be placed on a lab countertop, for example, making it convenient and comfortable for the technician.
An alternative to the hydraulic mini press would be a hand press. It works a bit like a nutcracker, with two arms being brought together to apply pressure to a die placed near the hinge. However, these machines offer no way of standardising the pressure load – so it’s likely that you’ll apply a different amount of pressure every time, producing inconsistent samples.
By contrast, a hydraulic mini press features a pressure gauge, so you can make sure you always apply the same load. This makes sample production far more reliable and repeatable.
Why use Specac for your FTIR and sample preparation equipment?
Specac offer a comprehensive range of sample preparation accessories for FTIR, including presses, pellet dies, high temperature film makers, and consumables such as KBr powder.
Besides these, a variety of other sampling techniques – including single and multiple reflection ATR, DRIFTS, and Specular Reflectance – are available.
Our accessories are customized and calibrated for the user’s needs, so why not contact our experts for a quote?
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