Measurement Reproducibility Concentration of the Genova Nano

By AZoM.com Staff Writers

Topics Covered

Introduction
Methods
Results
About Bibby Scientific

Introduction

An essential requirement of micro volume sample measurement is the reproducibility or precision of measurement. While measuring micro volume samples, very small changes in absorbance can result in much greater differences in calculated concentration values because of the inherent "dilution" factor of the small path length. For instance, while measuring dsDNA, an absorbance change of just 0.001 is equal to a derived concentration change of 1ng/µl at 0.5mm path length (based on 1 A260 unit of dsDNA = 50µg/ml).

Figure 1. Applying a sample to the Genova Nano read head.

Methods

8 different sample concentrations between approximately 1000 and 15ng/l were obtained by diluting a solution of calf thymus DNA (Sigma D3664) in nuclease-free water. The instrument setup was done in dsDNA mode, in which the sample concentration is determined by multiplying the absorbance at 260nm by a factor of 50 followed by a factor of 20 to allow for the 0.5mm path length. 2µl of nuclease-free water was used to zero the instrument and then 2 µl aliquots of the DNA solutions were measured. Each sample concentration was determined 10 times wiping the sample off the read head each time with a lint-free cloth.

Table 1. The specification of the Genova Nano is +/-2.0ng/µl for dsDNA samples <100ng/µl.

Measurement ng/µl ng/µl ng/µl ng/µl ng/µl ng/µl ng/µl ng/µl
1 1057 538.2 282.4 157.0 100.10 50.65 26.85 12.51
2 1054 544.2 284.0 153.8 99.00 50.85 28.10 12.66
3 1053 544.3 278.1 156.9 101.40 51.68 28.86 15.72
4 1052 545.1 277.4 156.1 99.62 53.38 28.43 15.68
5 1057 544.6 281.3 154.6 99.39 52.35 28.62 13.28
6 1063 546.0 283.7 155.0 99.27 52.50 30.32 13.85
7 1054 544.6 278.5 154.3 99.76 51.13 26.92 14.69
8 1054 546.5 281.5 154.1 98.38 52.44 28.61 12.62
9 1057 546.0 282.5 155.9 100.40 50.90 27.64 13.85
10 1056 545.4 279.5 156.5 101.90 53.81 29.96 16.03
Average 1055.7 544.5 280.9 155.4 99.92 51.97 28.43 14.09
SD 3.13 2.35 2.37 1.20 1.08 1.10 1.14 1.37
Max 1063 546.5 284.0 157.0 101.90 53.81 30.32 16.03
Min 1052 538.2 277.4 153.8 98.38 50.65 26.85 12.51
Range 11 8.3 6.6 3.2 3.52 3.16 3.47 3.52

Results

The results show the specified reproducibility of +/-2ng/µl for DNA samples <100ng/µl, which equates to an absorbance variation of +/-0.002A. To reduce any factors that may interfere with a reading such as contaminants or sample turbidity carried over from sample preparation, the reading can also be made at a second reference wavelength (where the absorbance of the sample is very low and unchanging) in order to perform a background correction. For this method, multi wavelength mode can be used.

About Bibby Scientific

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This information has been sourced, reviewed and adapted from materials provided by Bibby Scientific Ltd.

For more information on this source, please visit Bibby Scientific Ltd.

Date Added: Feb 7, 2014 | Updated: Feb 7, 2014
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