Identifying an Unknown White Powder

Problem: A client was a manufacturer of beverages, bottled water, and other drinks. They received a customer complaint through one of their distributors, which indicated that a customer had been drinking a bottle of water, and as they neared the bottom of the bottle, found a mysterious white powder floating in the bottom. The customer returned the bottle and complained. The client hoped to identify the powder so they could both satisfy their end customer, as well as identify any potential problems in their manufacturing or bottling process.

Approach: MicroVision Labs’ staff consulted with the client, and determined that, unfortunately, there could be a number of potential sources of a white material.  Even before the bottle with the suspended material arrived, it was determined that there was less than 50 mL of water remaining, and likely less than a gram of material suspended in the water.  The client was aware that this material could represent precipitated minerals from the source water, a polymer residue from the bottles, some form of biological tissue that might have formed despite sterilization procedures, or could very well represent some completely unforeseen foreign material.  The issue facing the client is how to have the material tested, as most tests that they might request for one or the other of these known potential sources would destroy or alter the sample.  Choosing a test was therefore something of a gamble, because if they tested for calcium (mineral precipitate) and it came up negative – that didn’t actually tell them what the powder was, just that it didn’t have any calcium.  Based on this conversation, the non-destructive, specialized testing at MicroVision Laboratories was chosen as the best choice.

Analysis and Results: The submitted bottle was examined for signs of interior distress, and the water from the bottle was removed and maintained.  Some of the suspended particulate was filtered and examined non-destructively by light microscopy first, to characterize the material.  A low magnification stereo microscope image of the filtered white particulate is shown in the image above.  From this image, biological tissues were ruled out, and the material was observed to be crystalline.  Polarized light microscopy (PLM) was used to analyze the sample next.  From this examination, the material showed birefringence as shown in the PLM image on the right.  The PLM Image Stereo Microscope image suspect material showed optical properties and morphology dissimilar to common carbonates and sulfates.  It was determined to be a birefringent crystalline material, but it could not be identified using only PLM methods.  Therefore, analysis using scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS) would have to be performed to obtain further information about the suspect material.

The SEM was used to examine the crystal morphology, and the EDS spectrum showed primarily carbon and oxygen, with small amounts of nitrogen and phosphorous.  This indicated an organic material as the primary component.  Because the SEM-EDS analysis showed the material was primarily a carbon based organic crystalline material, a Fourier transform infrared spectroscopy (FTIR) examination was performed on the suspect material.  This analysis provides necessary information about the functional groups of the organic material in order to identify the unknown organic.  As indicated in the FTIR spectral comparison below, the suspect material showed a near perfect match for acetylsalicylic acid.  Additionally, there was a small amount of dibasic phosphate present.  It was determined that the material was likely acetylsalicylic acid with a phosphate binder – an aspirin.

Therefore, from this analysis the suspect material in the bottle was likely a household aspirin tablet, broken apart and separated by the water.  In order to confirm the identification, a few aspirin tablets from several common manufacturers were obtained, roughly ground, and soaked to allow for comparison.  The optical morphology of the crystals, size range of the particles, association with the phosphate and FTIR spectrum all were consistent with the original suspect material.  A report detailing the methods and findings in full narrative form was rendered to the client.

Conclusion: Based on the analytical report, the client was able to demonstrate that the particles were consistent with a common aspirin tablet.  When the end customer was approached with this report, they remembered that their spouse had taken an aspirin earlier that morning, and had likely used the bottle of water in question to do so.  Based on this, the customer was happy, the manufacturing client was satisfied, and the sample was maintained – undestroyed should someone need to examine the sample again or do any more esoteric testing.  For an affordable price, the client was able to get piece of mind, and gather information from a very wide range of testing methods quickly and accurately.


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