The present invention provides a method for determining a concentration of at
least one analyte in a sample contained in a blood bag or in tubing in fluid communication
with said blood bag, using an instrument comprising at least one calibration algorithm
for the at least one analyte. The method comprises irradiating a sample in the
tubing or the blood bag, using a near infrared and adjacent visible radiation source.
Then measuring absorbance from the sample for the at least one analyte, and calculating
a concentration of the at least one analyte using the absorbance and the at least
one calibration algorithm.