The method uses NIR spectroscopy and a test element comprising a support, and {HEAD ~ a substantially constant light path} defining {TAIL ~ layer} comprising a diffusely reflecting material that is a) sufficiently porous in all directions as to allow a liquid to spread uniformly in all directions, and b) homogeneously reflects at least 95% of NIR radiation 
defining
The method uses NIR spectroscopy and a test element comprising a support , and { HEAD ~ a substantially constant light path } defining { TAIL ~ layer } comprising a diffusely reflecting material that is a ) sufficiently porous in all directions as to allow a liquid to spread uniformly in all directions , and b ) homogeneously reflects at least 95 % of NIR radiation
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