Sub-Nanometer Measurements of Caffeine Solutions with Dynamic Light Scattering

By AZoNano

Topics Covered

Background
Sample Preparation
Measurement
Results
Summary
About Avid Nano

Background

Caffeine is a bitter tasting substance with well known physiological properties which stimulate the mind and body in numerous ways. Having a molecular weight of 194.2 g/mol, it is a very small molecule which readily dissolves in water. The characteristics of caffeine make it suitable to demonstrate the power of the W130i dynamic light scattering system from Avid Nano, to detect molecules or particles of less than 1nm in size.

Sample Preparation

A solution of 1.4% w/v caffeine (Sigma Aldrich C0750) in water was prepared and filtered through a 0.02µm filter into a square quartz glass cuvette.

Measurement

The prepared cuvette was placed into the temperature controlled sample holder of the W130i, and allowed to stabilize at 20°C for 10 min. Two acquisitions, each averaged over 300s were taken.

Results

Figure 1. Hydrodynamic diameter distribution of caffeine solutions

Figure 2. Correlation functions for DLS experiments on caffeine solutions

The light scattering signal from the dissolved caffeine is sufficient to produce a good quality correlogram with an intercept >0.25 and highly reproducible data with relatively low polydispersity.

The mean radius was consistently reported at about 0.48nm and molecular weight estimate around 500Da indicating concentration dependent self association into dimers, a known characteristic of caffeine in aqueous solutions.

Table 1. Results obtained by dynamic light scattering on aqueous caffeine solutions

Experiment Mean Radius Std. Dev. Polydisp. Est. MW
Caffeine 14 g/l 0.46 nm 0.15 nm 32.46% 0.449 kDa
Caffeine 14 g/l 0.48 nm 0.18 nm 38.43% 0.539 kDa

Summary

The W130i DLS system is easily capable of discerning molecules or particles of less than 1nm in diameter, even at low concentrations.

About Avid Nano

Avid Nano produce the most exciting and innovative new dynamic light scattering products. Avid Nano pursue the highest levels of performance, know-how, technology, convenience and reliability for all our products, used in laboratory applications requiring fast, accurate DLS measurements in the nano-metre size range.

This information has been sourced, reviewed and adapted from materials provided by Avid Nano.

For more information on this source, please visit Avid Nano.

 

Date Added: Jan 28, 2013 | Updated: Jun 11, 2013
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