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 (n = 5 independent replicates, obtained on three different days by different analysts).

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

^aThe analyses were performed for determination of GlcNAc by three different operators using four different matrix samples in different days.

^bThe analyses were performed for determination of GalNAc by three different operators using four different matrix samples in different days.

^cRelative standard deviation (%).