by
vmu » Sat Mar 20, 2021 6:56 am
https://support.waters.com/KB_Inf/Empower_Breeze/WKB85832_Empower_3_PDA_What_is_Purity_1_Angle_Purity_1_Threshold_How_is_the_peak_purity_determined
4. Poor purity of the standard
High purity standard samples can be determined to be of poor purity mainly for the following reasons.
・The concentration is too high
Even if the absorbance exceeds 1 AU only at partial wavelengths, the absorbance linearity will be lost and the spectrum will be distorted, and the purity is measured to be poor. Please reduce the concentration so that the absorbance at the maximum absorption does not exceed 1 AU, and perform the measurement again.
・High background absorption of the mobile phase
https://support.waters.com/KB_Inf/Empower_Breeze/WKB11215_How_do_you_set_up_the_Purity_Thresholds_in_Empower_3
2. Record the maximum spectral absorbance (MSA) of this standard.
Tip: To use AutoThreshold, Waters recommends that the MSA of the standard be less than 1 AU. Since photometric error increases above 1 AU, Peak Purity measurements become significantly less sensitive to the presence of co-elution when the MSA of a compound exceeds 1 AU.