Solutions for e-liquid testing

In this interview, AZoM talks to Erik Gubler, Product Manager at Mettler-Toledo GmbH, about e-liquid testing; how to do it, why it is important and how Mettler-Toledo can help you.

Can you give a brief overview of your business, your work and the markets you serve?

METTLER-TOLEDO is a manufacturer of balances and laboratory equipment, and we sell our analytical instruments worldwide to a wide range of industries and segments. I worked for METTLER-TOLEDO as a specialist in titration applications, application development, customer support and education. I am currently working as a Titration Product Manager. My main missions are the management, maintenance and promotion of our titration portfolio, in close contact with clients and our R&D teams.

Why are analytical techniques, such as density and refractive index measurement, titration, color and boiling point important to e-liquid manufacturers?

Quality control of e-liquids is essential to ensure that consumers are assured of the e-cigarette or “vaping†experience they expect. Testing on e-liquids also helps assure regulators and consumers that e-liquids are marketed as advertised in terms of nicotine content, flavor and freshness. Density, refractive index, color (Gardner index, “yellowing”) and pH measurements are all performed in seconds and generally do not require sample preparation. These parameters can be used to confirm whether raw materials or differently flavored consumer products are within specification and allow defective products to be easily rejected. The water content and the Gardner index (yellowing) correspond directly to the freshness of the e-liquid. These parameters are measured by Karl Fischer titration and by UV / VIS spectroscopy.

The quantification of the nicotine content is the most critical parameter since it is regulated for e-liquids in most countries. It can be measured quickly using an acid-base titration. Sample preparation involves only weighing and dissolution in ethanol. Boiling point determinations are used more for R&D purposes. Knowing the evolution of the boiling point when changing the recipe of the e-liquid is quite important.

Excellence T7 Titrator with KF Coulometric Kit, which creates a compact all-in-one system for determining nicotine and water content. Image credit: Mettler-Toledo GmbH

Potentiometric dosage of nicotine in e-liquids.

Potentiometric dosage of nicotine in e-liquids. Image credit: Mettler-Toledo GmbH

Can you tell us more about the regulation of this market?

There is certainly a trend towards more regulation in the e-liquids market. The European Directive 2014/40 / EU, which concerns the manufacture, presentation and sale of tobacco and related products, included for the first time e-cigarettes and e-liquids. The implementation and enforcement of the Directive is the responsibility of the EU country concerned.

Since 2017, Germany obliges producers and importers to authorize new products by submitting a complete list of all ingredients with the corresponding weight percentages. The nicotine content is limited to 20 mg / mL and the exact composition must be indicated on the product label.

E-liquids have been regulated by the United States Food and Drug Administration (FDA) since 2016. Manufacturers and importers of e-liquids must register their products with a complete list of ingredients that include harmful and potentially harmful components. .

What solutions for testing and characterizing e-liquids does Mettler-Toledo offer?

We supply high quality titration, UV / VIS, density, refractive index, pH and boiling point instruments as well as laboratory balances. For each of the required e-liquid analyzes, we have developed a dedicated application note that involves the entire measurement procedure, from sample preparation to methods up to the expected accuracy of the results.

What aspect of the e-liquids manufacturing chain does Mettler-Toledo specialize in?

Our Laboratory division has dedicated solutions for the quality control of raw materials and finished consumer products. Our industrial weighing division has dedicated weighing solutions for larger production batches, where bulk weighing, formulation, product inspection and statistical quality control procedures may be required.

Can you give an example?

An e-liquid producer buys the main ingredients: propylene glycol, vegetable glycol, aromatic tinctures and nicotine. The density or refractive index of liquids is quickly checked to see if it meets specifications. Both techniques can also be used to accurately determine the propylene glycol / vegetable glycol ratio. Then the components are mixed to give the final e-liquid (eg tobacco flavor with 6 mg / mL of nicotine). Density, refractive index, pH value and Gardner index are measured and checked if the values ​​are within the defined limits of the tobacco e-liquid. In the end, an acid-base titration using our automated titrators gives the nicotine content. This is especially important because it is limited in many countries to less than 20 mg / mL.

What sets Mettler-Toledo products apart from other products on the market?

We not only supply good instruments, but also sell our LabX software to which all mentioned lab devices can be connected. Data is centrally managed, only one user management system is required, and results can be automatically checked against specifications. Software reports provide a simple overview to the operator if limits are violated.

In addition, we can connect the density, refractive index, pH meter and UV / VIS spectrophotometer with an autosampler, which gives a multiparameter system. The e liquids are pumped through all the measuring cells giving all the parameters in a single analysis started with OneClick®.

DERE, UVVIS, pH Multiparameter system.

DERE, UVVIS, pH Multiparameter system. Image credit: Mettler-Toledo GmbH

Results of a multiparameter system.

Results of a multiparameter system. Image credit: Mettler-Toledo GmbH

Where can our readers find out more?

They can go to our new website:

What is the next step for Mettler-Toledo in the field of e-liquids?

We are constantly looking for market contributions and will develop other applications for our devices when it comes to e-liquids.

About Erik Gubler

Erik GublerAfter completing his chemistry studies at ETH Zurich in 2017, he started his career at METTLER-TOLEDO ANALYTICAL in 2018 as an Application Specialist for Titration, recently joining the Titration Product Management team.

After developing applications in the laboratory, Erik now brings his ideas for the development of advanced analytical instrument solutions to METTLER-TOLEDO as Product Manager.

This information was obtained, reviewed and adapted from materials provided by METTLER TOLEDO – Density and Refractometry.

For more information on this source, please visit METTLER TOLEDO – Density and refractometry

Disclaimer: The opinions expressed here are those of the respondent and do not necessarily represent the views of Limited (T / A) AZoNetwork, the owner and operator of this website. This disclaimer is part of the terms and conditions of use of this website.

Aron M. Newman

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