The present invention includes an apparatus for preparing samples for measurement by x-ray fluorescence spectrometry. The apparatus comprises a plate having one or more holes passing through the plate. The holes are covered by a film on one side of the plate. The holes are less than 500 micrometers across in one dimension where the film covers the holes. The film is translucent to x-rays. The present invention also includes an apparatus for preparing samples for measurement by x-ray fluorescence spectrometry. The apparatus comprises a plate having one or more holes passing through the plate. The holes are covered on one side of the plate by a detachable cover forming a water-tight seal against the plate. The cover is substantially free of the elements osmium, yttrium, iridium, phosphorus, zirconium, platinum, gold, niobium, mercury, thallium, molybdenum, sulfur, lead, bismuth, technetium, ruthenium, chlorine, rhodium, palladium, argon, silver, and thorium. The holes are less than about 500 micrometers across in one dimension where the cover covers the holes. The present invention also includes a method for preparing samples for measurement by x-ray fluorescence spectrometry. The method comprises providing a solution of with less than 10 micromolar solute and a volume of between about 2 microliters and about 2 milliliters. The solution is concentrated and analyzed using x-ray fluorescence spectrometry.
1. A method for preparing a sample for measurement by x-ray fluorescence spectrometry, comprising providing a solution having a concentration of solute less than 10 micromolar and a volume of between 2 microliters and 2 milliliters, concentrating the solution into a sample having less than one-fifth of the original volume of the solution, and analyzing the sample using x-ray fluorescence spectrometry.
2. The method of claim 1 , wherein the solution comprises a biological molecule having a concentration of less than about 10 micromolar.
3. The method of claim 2 , wherein the biological molecule in the solution has a total mass of between 50 femtograms and 1 microgram of an element selected from the list of phosphorus, sulfur, and combinations thereof.
4. The method of claim 1 , wherein the sample is dried in a well plate having a well which is less than about 500 micrometers in at least one dimension at the bottom of the well.
5. The method of claim 4 , wherein the well has an included angle of less than about 45 degrees.
6. The method of claim 5 , wherein the area of the bottom of the well is less than about 0.005 square centimeters.
7. The method of claim 6 , wherein the walls of the hole have an RMS roughness of less than about 20 micrometers.
8. The method of claim 7 , wherein the well plate has a detachable bottom piece, and at least a portion of the sample remains on the detachable bottom piece when the detachable bottom piece is detached.
9. A method for preparing a sample for measurement by x-ray fluorescence spectrometry, comprising providing a solution having a concentration of solute less than 10 micromolar and a volume of between 2 microliters and 2 milliliters, and concentrating the solution into a sample having less than one-fifth of the original volume of the solution, wherein the solution comprises a biological molecule having a concentration of less than about 10 micromolar.
10. The method of claim 9 , wherein the biological molecule in the solution has a total mass of between 50 femtograms and 1 microgram of an element selected from the list of phosphorus, sulfur, and combinations thereof.
11. The method of claim 9 , wherein the sample is dried in a well plate having a well which is less than about 500 micrometers in at least one dimension at the bottom of the well.
12. The method of claim 11 , wherein the well has an included angle of less than about 45 degrees.
13. The method of claim 12 , wherein the area of the bottom of the well is less than about 0.005 square centimeters.
14. The method of claim 13 , wherein the walls of the hole have an RMS roughness of less than about 20 micrometers.
15. The method of claim 14 , wherein the well plate has a detachable bottom piece, and at least a portion of the sample remains on the detachable bottom piece when the detachable bottom piece is detached.