Table 2. Relative Error and Mean of the Replicates Experimentally Obtained Using Both the Approach Developed and the Regular sp Approach over 8 Months for Five Different AuNPs (n = 7) and One AgNP (n = 5, Last Row)^a.

diameter TEMb	this approach		regular sp
	diameterc	error (%)	diameterc	error (%)
16.4 ± 0.3	16.6 ± 1.2	1.2	16.3 ± 1.2	0.61
24.4 ± 0.3	24.7 ± 1.6	1.1	23.2 ± 1.5	4.9
27.4 ± 0.5	27.1 ± 1.7	1.0	25.5 ± 1.7	6.9
39.6 ± 0.7	39.5 ± 2.8	0.24	41.0 ± 3.1	3.5
73.3 ± 1.3	70.0 ± 7.4	4.5	61.9 ± 7.6	16
			(68.1 ± 8.0)d	(7.1)d
40.1 ± 0.6 (AgNP)	39.5 ± 3.1	1.5	51.7 ± 3.2	29
			(39.3 ± 5.1)d	(2.0)d

^aThe reference standard (AuNP, 18.7 nm) was measured once at the beginning of the time period and every working day for the developed and the regular sp approach, respectively.

^bUncertainty corresponds to the standard error of the mean (k = 2) of the TEM images.

^cCombined standard uncertainty comprising individual uncertainty and reproducibility of the n replicates (95% confidence interval).

^dResults obtained when using AuNPs of 39.6 nm for the AuNPs of 73.3 nm and AgNPs of 51.3 nm for the AgNPs of 40.1 nm as reference standards, respectively.