TECHNICAL NOTE
2
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10 mM NaCl solution. DLS measurements were carried out with the Size Analysis function
of the Panta Control so ware, using the high sensitivity mode for enhanced measurement
accuracy and precision.
Table 1 shows the measured r
H
values of each particle size standard, along with the
expected mean r
H
values as stated by the supplier information sheet and obtained using
transmission electron microscopy. Particle sizes measured by Prometheus Panta match
the NIST-certified r
H
values of the respective standards, which confirms the accuracy of
the DLS optics.
Table 1: Overview of certified and
measured r
H
values of 9 different
particle size standards.
Nanosphere
TM
Size Standards
Measurements 3020A 3060A 3100A 3500A 3600A 3700A 3800A 3900A 4010A
Certified r
H
and standard
deviation
11.5 ± 1 nm 30.5 ± 2 nm 50 ± 2 nm 255 ± 4 nm 300 ± 5 nm 351 ± 3 nm 452 ± 4 nm 452 ± 6 nm 518 ± 6 nm
Measured r
H
and standard
deviation*
11.7 ± 0.1 nm 31.3 ± 0.4 nm 52.2 ± 0.6 nm 268 ± 8 nm 322 ± 11 nm 373 ± 13 nm 420 ± 15 nm 462 ± 19 nm 543 ± 17 nm
Consistency of the sizing accuracy for sample concentrations at the
limit of detection
When it comes to sizing molecules with accuracy, it's important to ensure that a given
protein concentration is adequate for sufficient scattering intensity and for accurate
size analysis. In general larger proteins such as monoclonal antibodies can be sized
at very low concentrations down to 50 µg/mL, whereas proteins with lower molecular
weights and smaller scattering cross sections require higher concentrations for sufficient
scattering intensity. Prometheus Panta's sizing accuracy was assessed for consistency
using two representative protein standards, Lysozyme and NISTmAb, at a range of
concentrations that included their lower limit of detection.
* standard deviation from 5
independent measurements
