Small molecule crystal structure determination by MicroED requires crystalline samples. The crystals can be as small as a few hundred nanometers, but amorphous samples are not suitable. Thankfully, many compounds readily form microcrystalline powders, but knowing which samples are suitable for MicroED and which are not can be challenging. Polarized light microscopy is often used to identify crystals, but it is not always accurate. The best way to determine if a sample is crystalline is by checking for diffraction.
NIS offers Powder X-Ray Diffraction (PXRD) pre-screening to identify crystalline samples suitable for MicroED.
NIS recently partnered with a local provider of powder X-ray diffraction (PXRD), also called X-ray powder diffraction (XRPD), to pre-screen samples for MicroED structure determination. With as little as 1 mg of material, we can first screen the sample using PXRD and then collect MicroED data if suitable diffraction is seen by PXRD. This pre-screening provides a quick Go / No Go answer without needing to wait for microscope time.
Collecting a PXRD pattern has the added benefit of providing a measurement from the bulk solid, to ensure that the MicroED structure corresponds to the bulk solid and to indicate the possible presence of other crystal forms.