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Students using NMR Single Crystal Sample Information

All samples submitted to the X-ray Facility for characterization must be accompanied by a SAMPLE SUBMISSION FORM. Samples must be clearly labeled and stored under mother liquor if they are sensitive to solvent loss. Air-sensitive samples should be tagged as such. Any special handling instructions should be clearly noted on the submission form. Since crystal quality is probably the single most important factor in determining the final precision for a given structural investigation, keep in mind that high-precision structural results will generally require high-quality crystals.


In general, crystals should meet the following criteria:

1. The crystal should be a single entity which has no smaller crystals or powder attached to it.
2. Crystals should be of the proper size and shape. The crystal should be 0.1 to 0.6 mm. on an edge and as equidimensional as possible. For substances which do not contain highly absorbing elements (e.g. most organic molecules), the optimum sample would be a ~0.5mm. diameter sphere. Needle- or plate-shaped crystals can usually be used if they are at least 0.1mm. thick.
3.Good single crystals usually have well-defined and lustrous faces; they are of uniform color and contain no cracks or fracture lines.
4.Crystals should diffract to reasonably high scattering angles.
5.Crystals should have reasonably uniform and small "mosaic spreads".


Chemistry Department, Wake Forest University, Salem Hall, Box 7486
Winston-Salem, NC 27109. Phone: (336) 758-5773 FAX: (336) 758-4656
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