Foreign body identification

Illustrates how we investigate foreign body problems and explains how this can be used to prevent recurrences of problems.

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This video clip shows how glass and many other foreign bodies can be analysed using an x-ray micro analyser attached to a scanning electron microscope. When an electron beam is fired at a sample in the microscope x rays are emitted, these are detected by the blue detector on the side of the microscope column and can be analysed to show the characteristic elemental compositions of different types of glass and other materials.

Our laboratory has an enormous collection of reference samples of different foreign bodies for comparison with samples submitted for analysis, these include over 700 glass samples from known sources. When results have been confirmed they can be compared with the reference samples to help in the identification of the problem. Knowing the type of glass involved can help the client prevent recurrences or resolve the problem with the complainant.

Samples are first loaded into the sample chamber, the chamber door is closed and the chamber pumped down to a vacuum, necessary for the electron beam. With each batch of samples, a calibration spectrum is taken from a standard reference sample of pure cobalt. The cobalt sample is first moved into position under the electron beam using a joystick to move the sample stage around in the chamber. Now the glass sample is moved under the electron beam and a spectrum is acquired from it the glass spectrum appears on the third monitor screen, and here we have a typical spectrum for a soda lime glass used to window glass with peaks for oxygen, sodium, magnesium, aluminium, silicon and calcium. The computer assigns labels to the peaks automatically so first we have to double check that the labels are correct. We can check the peaks are what we think they are by overlaying them with authentic peaks. From this we can be pretty sure that both potassium and tin are present in the glass sample, the presence of tin is particularly important because it is used in the manufacture of window glass where the molten glass is floated onto a bath molten tin to give a truly flat surface and the small amount of tin is left on the glass surface. Now we can export the spectrum for inclusion in a report to the client. Campden BRI offers an identification service for all types of foreign bodies reporting for food using a wide range of forensic techniques.

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