Table 1.

Reference materials used during the method optimisation and validation studies, relevant assigned particle size values and associated expanded (k = 2) uncertainties

Reference material ID	Supplier’s reference	Particle mass fraction [g/kg]	Method used for value assignment	Assigned particle size value (± uncertainty) or range [nm]
ERM-FD304	ERM-FD304	2.5	DLS (cumulants algorithm)a	42.1 ± 0.6
			SEM and TEMc	27.8 ± 1.5
ERM-FD101b	ERM-FD101b	2.5	DLS (cumulants algorithm)a	89.5 ± 2.3
			DLS (distribution calculation algorithms)b	93 ± 4
			SEM and TEMc	83.7 ± 2.2
			SEM and TEMd	83.5 ± 2.2
			PTAe	82 ± 4*
			PTAf	87 ± 4*
			PTAg	82 ± 4*
ERM-FD102	ERM-FD102	Size class A—10.0 (nominal 20 nm) Size class B—2.5 (nominal 80 nm)	DLS (distribution calculation algorithms)b	17.8 ± 1.5 88.5 ± 2.2
			SEM and TEMc	18.2 ± 1.6 84.0 ± 2.1
			SEM and TEMd	18.3 ± 1.7 83.3 ± 2.3
			PTAe	78 ± 5
			PTAf	82 ± 4
			PTAg	79.2 ± 2.2
PSL-21	3020A	10	DLS	21 ± 1.5
PSL-31	3030A	10	DLS	31 ± 3
PSL-41	3040A	10	DLS	41 ± 4
PSL-46	3050A	10	TEM	46 ± 2
			DLS	45–51
PS-59	3060A	10	TEM	59.0 ± 2.5
		10	DLS	58–65
PSL-81	3080A	10	TEM	81 ± 3
			DLS	79–84
PSL-100	3100A	10	TEM	100 ± 3
			DLS	98–103
PSL-125	3125A	10	TEM	125 ± 3
			DLS	120–130
PSL-147	3150A	10	TEM	147 ± 3
			DLS	146–153
PSL-200	3200A	10	TEM	200 ± 6
			DLS	196–206

^*Certified values used for trueness assessment

^aSphere-equivalent intensity-weighted harmonic mean hydrodynamic diameter

^bSphere-equivalent intensity-weighted arithmetic mean hydrodynamic diameter

^cArea-equivalent number-weighted circular modal diameter

^dArea-equivalent number-weighted circular median diameter

^eSphere-equivalent number-weighted modal hydrodynamic diameter

^fSphere-equivalent number-weighted arithmetic mean hydrodynamic diameter

^gSphere-equivalent number-weighted median hydrodynamic diameter