Discussion Category:  UV/VIS Spectrophotometers

Total N test

i dissolved 1g of uria in 1L and i tried to find total N in that 1. but spectro show "Absorbance > 3.5 !". what is this?

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Hello janaka,

You are seeing this error because you are trying to test at a concentration which is well above the range of any of the Hach total nitrogen methods.  1g/L urea is about 466mg/L nitrogen.  I'm not sure which method you are using, but the highest range Hach TN method is only good to 100mg/L N.  So your standard is at least 4.7 times too concentrated to be analyzed with any of the Hach TN methods.  

The maximum absorbance that the spectrophotometer can read is 3.5 AU.  The error message you are getting indicates that the color of your standard is too intense, that your standard is out of range.  All of the light is being absorbed by the standard, and none of it is getting to the detector.  

You should get meaningful results if you dilute your standard into the range of the method you are using.  

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