A New HPLC-ELSD Method for Simultaneous Determination of N-Acetylglucosamine and N-Acetylgalactosamine in Dairy Foods

Table 4

Within-laboratory precision, expressed as relative standard deviation for different working days (RSD), for four different matrices fortified with GlcNAc and GalNAc at the same concentration as was originally detected ( independent replicates, obtained on three different days by different analysts).

Recovery (%)
Operator	Raw milk		UHT milk		Yogurt		Infant formula
	Recovery	RSD	Recovery	RSD	Recovery	RSD	Recovery	RSD
GlcNAc
A	101.7	0.5	101.7	0.7	102.1	0.8	97.7	1.1
B	101.8	1.0	101.6	0.1	98.6	1.2	100.9	0.5
C	102.4	0.6	103.8	0.5	100.0	1.0	102.0	1.0
GalNAc
A	102.5	12	98.5	0.2	101.6	1.2	101.8	2.3
B	101.8	0.1	101.2	0.7	101.0	0.5	100.0	0.5
C	98.4	1.3	99.4	1.3	101.2	0.4	101.3	0.5

The analyses were performed for determination of GlcNAc by three different operators using four different matrix samples in different days.
The analyses were performed for determination of GalNAc by three different operators using four different matrix samples in different days.
Relative standard deviation (%).