Insights from industry

Solutions for E-Liquid Testing

insights from industryErik GublerProduct ManagerMettler-Toledo GmbH

In this interview, AZoM speaks 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.

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

METTLER-TOLEDO is a manufacturer of scales and laboratory equipment, and we sell our analytical instruments globally to a wide range of industries and segments. I was working for METTLER-TOLEDO as an application specialist in titration, developing applications, providing customer support, and teaching people. I currently work as a titration product manager. My main tasks are the management, maintenance, and promotion of our titration portfolio, with close contact with customers and our R&D teams.

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

Quality control of e-liquids is critical for ensuring that consumers are assured of the e-cigarette or “vaping” experience they expect. E-liquid testing also helps to assure regulators and consumers that e-liquids are presented as advertised in terms of nicotine content, flavor, and freshness. Density, refractive index, color (Gardner Index, "Yellowness"), and pH measurements are all done within seconds and generally do not need any sample preparation. These parameters can be used to confirm if the raw materials or the differently flavored consumer products are in the specification and allows for faulty products to be easily rejected. The water content and the Gardner Index (Yellowness) directly correspond to the freshness of the e-liquid. These parameters are measured by Karl Fischer titration and with UV/VIS spectroscopy.

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

Excellence T7 Titrator with coulometric KF Kit, which creates a compact all-in-one system to determine nicotine and water content. Image Credit: Mettler-Toledo GmbH

Potentiometric determination of nicotine in e-liquids.

Potentiometric determination of nicotine in e-liquids. Image Credit: Mettler-Toledo GmbH

Can you tell us more about the regulations in this market?

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

Since 2017, Germany has forced producers and importers to authorize new products by submitting a complete list of all ingredients with corresponding weight percentages. The nicotine content is restricted to 20 mg/mL, and the exact composition needs to be listed 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 need to register their products with a complete ingredient list that includes harmful and potentially harmful constituents.

What e-liquid testing and characterization solutions do Mettler-Toledo provide?

We provide 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 analyses, we have developed a dedicated application note that involves the whole measurement procedure from sample preparation to methods to the expected precision of results.

Which aspect of the e-liquid manufacturing chain does Mettler-Toledo specialize in?

Our Laboratory division has dedicated solutions for the quality control of both 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 of this?

An e-liquid producer buys the main ingredients: propylene glycol, vegetable glycol, flavoring tinctures, and nicotine. The density or refractive index of the liquids is quickly checked to see if it is within specification. Both techniques can also be used to accurately determine the ratio of propylene glycol/vegetable glycol. Afterward, the components are mixed to give the final e-liquid (e.g. tobacco aroma with 6 mg/mL nicotine). The 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 as it restricted in many countries to less than 20 mg/mL.

What makes Mettler-Toledo’s products stand out from anything else on the market?

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

Furthermore, we can link the Density, refractive index, pH-meter, and UV/VIS spectrophotometer together with an autosampler, giving a multiparameter system. The e liquids are pumped through all the measuring cells giving all parameters in one analysis started with OneClick®.

DERE, UVVIS, pH Multiparameter system.

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

Results from a Multiparameter system. 

Results from a Multiparameter system. Image Credit: Mettler-Toledo GmbH

Where can our readers find out more?

They can go to our new website:

What’s next for Mettler-Toledo in the area of e-liquids?

We are constantly looking for input from the market and will develop further applications for our devices with regards to e-liquids.

About Erik Gubler

Erik GublerAfter finishing his chemistry studies at ETH Zurich in 2017, he started his career at METTLER-TOLEDO ANALYTICAL in 2018 as an applications specialist for titration, recently joining the titration product management team. 

After developing applications in the laboratory, Erik is now bringing in his ideas for the development of leading analytical instrument solutions at METTLER-TOLEDO as a product manager.


This information has been sourced, 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 views expressed here are those of the interviewee and do not necessarily represent the views of Limited (T/A) AZoNetwork, the owner and operator of this website. This disclaimer forms part of the Terms and Conditions of use of this website.


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