Microfluidic preconditioning of (bio)fluids for reagent-free infrared clinical analysis and diagnostics

A method of analyzing a multi-constituent fluid sample comprising:

• a) providing a multi-constituent fluid sample in which infrared absorption features of low concentration analytes are masked by infrared absorption features of relatively high concentration analytes, or lie below the threshold of detection;
• b) placing a stream of the fluid sample in laminar flow contact with a receiver stream under conditions in which inertial effects are negligible using a microfluidic laminar fluid diffusion interface device such that diffusion occurs between the sample stream and the receiver stream, which form a sample stream output, which undergoes relative concentration enrichment in relatively high molecular weight analytes and a receiver stream output, which undergoes relative concentration enrichment in relatively low molecular weight analytes, said receiver stream including an internal standard having a unique absorption peak within the spectral window of approximately 2000-2600 cm−1;
• c) collecting the sample stream output and the receiver stream output from the device;
• d) depositing individually the sample stream output and/or the receiver stream output onto an infrared compatible substrate and drying to a film, and;
• e) measuring the infrared spectrum for the film dried from the sample stream output and/or the film dried from the receiver stream.