A method and analyzer for identifying or verifying or otherwise characterizing a sample comprising: using or having an electromagnetic radiation source for emitting electromagnetic radiation in at least one beam at a sample, the electromagnetic radiation comprising at least two different wavelengths, using or having a sample detector that detects affected electromagnetic radiation resulting from the emitted electromagnetic radiation affected by the sample and provides output representing the detected affected radiation, and using or having a processor for determining sample coefficients from the output, and identifying or verifying or otherwise characterizing the sample using the sample coefficients and training coefficients determined from training samples, wherein the coefficients reduce sensitivity to a sample retainer variation and/or are independent of concentration.