| CPC G01N 23/223 (2013.01) [G01N 33/582 (2013.01); G01N 2223/612 (2013.01)] | 20 Claims |

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1. An apparatus, comprising:
an X-ray source;
an X-ray detector;
wherein the X-ray source is configured to direct an X-ray beam toward a surface at a glancing angle at which the X-ray beam undergoes total external reflection by the surface;
wherein a first biological analyte is immobilized to the surface and a first element is attached to the first biological analyte;
wherein the X-ray beam is capable of causing emission of characteristic X-rays of the first element;
wherein the X-ray detector is configured to receive the characteristic X-rays of the first element but not the X-ray beam reflected by the surface;
wherein the X-ray beam directed to the surface is a fan beam.
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