Determination of Silver in Ice Cream - Food Monitoring with Direct Solid Sampling HR-CS AAS

The bactericidal effect of silver has been known for a long time. As early as the 19th century, physicians used silver to treat wounds and for disinfection purposes. Its use for disinfecting drinking water can even be traced back to pre-Christian times - the custom to throw coins into the well did not simply promise good fortune but also improved water quality. Moreover, people added a silver coin to their milk cans for a long time to keep the milk fresh over longer periods. With the development of fridges, disinfectants and antibiotics the antimicrobial effect of silver was all but forgotten. It has only been recently that its advantages are being rediscovered and are
valued in many areas of application. Today, silver is used as a bactericide mostly in colloidal or ionic form, but also in form of coatings or nanoparticles, that are, for example, incorporated in clothing, utility items, medical tubes, instruments and wound dressings, but also in filter cartridges for water purification. The NASA Spaceshuttle uses silver for water purification purposes as well.

The bactericidal effect is based on several mechanisms. Silver inhibits the cell division and the transportation of nutrients in the cell and destabilises cell walls and membranes. This is a safe way to kill even bacterial strains that are resistant to antibiotics.

In dairy production, sterile processing is particularly important, because dairy products are an ideal breeding ground for bacteria. This is why milk processing companies are regularly inspected by the responsible surveillance authorities. The main focus is on the microbiological control of the products, an indicator that the production equipment has been cleaned and disinfected carefully. But even if the devices are disinfected thoroughly and themanufactured products are impeccable, any disinfectant residue must be removed completely after cleaning to avoid that they end up in the final product. To ensure this, the silver contained in the cleaning agents serves as a marker. If silver is detected in the product, this suggests that the disinfectant was not washed out completely and the equipment has not been cleaned carefully enough

Since dairy products such as ice cream cannot be analysed directly with the usual analytical methods, an acid digestion of the samples must be carried out before they can be analysed with atom spectrometric methods. This type of digestion, however, which is usually achieved with microwave-supported digestion systems, restricts the sample throughput of a laboratory because only few samples can be processed at a time. In addition, the personnel and time requirements are relatively high, which means that only a few samples can be analysed over the course of a day.