Home About Us Our Services Publications Testing Submissions Contact Us Links

SESL's new gizmo

Many of our clients have been feeling frustrated for the last few months as delays in returning results have increased. We would like to thank you for your patience, which can now be rewarded. We have finally commissioned our brand-new, state-of-the-art ICP-OES.

"What is an ICP-OES?" you ask.

It stands for inductively coupled plasma optical emission spectrometer. We'll explain what it does shortly.

The old way

The ICP-OES replaces two old workhorses, the atomic absorption spectrometers (AAS). When you previously sent samples to us, they were chemically extracted, and the extracts were injected into an AAS. This machine, about a metre long by half that wide and high, analyses one element at a time (say, calcium). The sample is injected and vaporised, and the light from a specific lamp is shone through the vapour. Some of the wavelengths of that light are absorbed (hence atomic absorption), and from the missing wavelengths, the quantity of element can be calculated. The AAS is fitted with four lamps, so up to four elements can be analysed. Each batch of samples takes 8 hours. A laboratory technician has to be present when the machine is working and to shut it down when it is finished. So runs are restricted to business hours and the number of samples that can be analysed. We were able to analyse up to 200 samples in a week.

The new way

That was the old way. The Perkin-Elmer 7000 DV ICP-OES is light years ahead. The sample is injected and is heated to 10 000 °C. That's hot enough to strip every last electron from every atom, turning the sample into a plasma. As the atoms cool again, the electrons recombine. As they drop back down into their orbits, they emit photons (hence atomic emission). These photons are measured to give an extremely accurate and precise measure of the quantity injected. Atomic emission spectra (those given out) are much more precise than absorption spectra (those that go missing), and very complex mathematics is used to separate overlapping spectra. In addition, the 7000 DV reads emissions both along the flame jet (to pick up tiny quantities) and across the jet (to pick up large quantities), allowing us to measure quantities down to nanograms per litre and up to grams per litre, all at the same time.

Instead of one element, the ICP-OES will measure any number of elements we choose, all at the same time, in less than 3 hours, and it will clean up and switch itself off without supervision.

The net result is that you can expect much faster turnaround times, and more accurate results than ever before.

Faster extraction too

In addition, we have recently changed over our chemical extraction methods to improve our times even further. Previously we used up to five extraction methods to take into account the different reactivities of elements and availabilities of nutrients to plants. Some of these extractions can take days. We have now adopted the Mehlich III method, which extracts everything in one step in a few minutes. Combined with the new ICP-OES, this now means a rapid turnaround of your samples, and the capacity to analyse many more samples than before – between 500 and 1000 samples a week!

We spent January installing, calibrating, validating, testing and learning to use the new gizmo. And now we're full steam ahead.

So we'd like to say a big thank you to all our clients for being tolerant and forgiving during the breaking-in period.

Download this article as a PDF