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Solutions to enhance the competitiveness of organic electroluminescent material products

Strict quality standards and high purification are critical in fabrication of organic electroluminescent (EL) materials. To develop and manufacture highly competitive organic EL products, companies need to focus on three determining factors: basic performance (novelty), stabilization of component materials quality and supply, and cost. Waters’ approach to these issues is a purification method using Supercritical Fluid Chromatography (SFC), which enables the ability to provide highly purified products, as well as the Ultra Performance Convergence Chromatography (UPC2), which enables strict quality control as the key differentiating technology to improve EL materials’ product competitiveness.

Quality factor analysis
Organic EL materials, comprising organic electric materials, is a high value-added product and only a handful  of advanced companies are able to produce it. The value of EL products and the investment in technology and expertise needed for their fabrication makes it important for manufacturers to improve the yield per production line, as well as product quality for product differentiation. The value of analysis is increased by the identification of impurities and feeding back the results to improve the process control and purification process. At Waters, we recommend a combination of the UPLC/Xevo G2 QTof system and a multivariate analysis software, Progenesis QI, to enable manufacturers to isolate factors related to lot-to-lot variability, and to predict the structure of differentiation factors.

Impurity Profiling
Quantitative analysis with high peak capacity is essential for monitoring and quality control in the manufacturing process of organic EL materials. Similarly, analysis of separation/determination is important when profiling impurities in the developmental phase, as well as when selecting and planning the purification method. Normal- or reversed-phase liquid chromatography (LC) is traditionally used in separation analysis. However, when it comes to separating organic EL materials, there are concerns such as the potential for overlooking unseparated isomers and analogs, as well as compounds that remain in the column due to polarity or complex molecular structure. Waters recommends the complementary use of the UPLC H-Class and the UPC2 for the impurity profiling of organic EL materials.

UPLC H-Class/PDA system

  • Optimize the development of efficient reversed-phase separation conditions
  • Apply a condition using solvents with high-elution performance in a mixed solution-sending system with four types of solutions
  • CSH column optimized for the analysis of aromatic tertiary amines

Peak-purity test using a PDA detector

Example of the analysis of BDABVi using the UPLC H-Class/CSH C18
The peaks of the isomers that can be overlooked in traditional HPLC are detected by using UPLC technology as demonstrated in Fig 1.

Fig. 1 Peak shape without tailing can be obtained by using the CSH C18 column.

Example of analysis of Ir(Fppy)3 using the UPC2/BEH 2-EP
There are two types of isomers, the facial (fac) type and the meridional (mer) type, that exist in octahedral complexes, MLa3Lb3. UPC2 is a technology that can increase the feasibility of isomer separation such as in octahedral complexes.

An example of the separation of facial/meridional type isomers of Ir(Fppy)3 using an UPC2 BEH 2-EP columns is shown in Fig 2 below.

Structural elucidation of impurities

Novel purification method
Distilling and manufacturing extremely pure organic EL materials remains a daunting task for the industry. For materials that are difficult to purify by distillation, several purification methods and synthetic methods have been studied to solve the problem of removing analogs. To resolve this challenge, Waters introduced a novel purification technique: Prep SFC systems. Using Prep SFC, the purification method is selectable from a lab-scale system for the structural analysis of impurities to a bench-scale system for preparation purification, and even to the industrial production, depending on the customers’ need.

Example of the SFCq 100 system                      Example of the SFC 350 system

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