Multi-Amine Analysis with QRS™ for CO₂ Scavenging

Quantitative Raman Spectroscopy™ (QRS) converts Raman spectroscopy from an identification technique into a full-blown quantitative method. With OndaVia test kits, users of QRS are able quickly to measure the concentration of components in water. As an all-optical method, QRS is non-destructive while eliminating potential instrument damage due to improper sample preparation or composition. Our methods range from %-level triazine-based H2S scavengers to parts-per-trillion-level analysis of formaldehyde to multi-amine analysis of industrial chemical streams, with data in as little as a few seconds with minimal sample preparation.

Importantly, QRS is not limited to measuring a single analyte. Although many OndaVia test kits initially target a single analyte, QRS-based methods are capable of multi-amine analysis capabilities—quantifying more than one sample constituent at one time. The development and expansion of additional parameters is driven by customer requests and requirements. Just ask!

Recently, a customer asked about expanding our methyldiethanolamine (MDEA) method to measure piperazine (PPZ). MDEA is a powerful scavenger for H2S and CO2, and OndaVia has offered a QRS-based analysis method for nearly a decade. PPZ, however, was a new analyte for the OndaVia. Measuring both MDEA and PPZ is crucial for several reasons. First, when used in CO2 scavenging applications, PPZ is often added to improve performance; adding PPZ to MDEA significantly improves its CO2 absorption capacity, leading to optimized performance. Second, regularly monitoring MDEA concentration through QRS helps identify depletion and schedule replenishment before capture efficiency suffers. Third, QRS-based measurement of PPZ allows tracking its concentration to maintain system integrity by identifying degradation and enabling actions like solvent replacement or degradation control.

Based on the market need and the customer request, the OndaVia team prepared fresh samples and quickly published an updated calibration curve. In the data below, we show the results from multi-amine analysis by measuring MDEA samples in aqueous solution over 50- to 100% by weight, with and without PPZ. With a single pipette step and one minute of analysis time, QRS provides fast and accurate MDEA concentration analysis.

MDEA Calibration Curve
Methyldiethanolamine (MDEA) concentration (%-wt)

Of the ten samples above, seven contain some concentration of PPZ. As can be seen in the curve, which is linear and of unit slope, the addition of PPZ does not affect the MDEA measurement. Yet, as shown below, the PPZ can be simultaneously quantified over the range of 0- to 25%-wt. The PPZ calibration curve is linear and of unit slope.

PPZ Calibration Curve
Piperazine concentration in MDEA solutions (%-wt)

This test expands OndaVia’s capabilities that enable carbon capture and reduction: a single test provides quantification of both amines. Additional benefits of using QRS for MDEA/PPZ analysis include its non-destructive nature, with minimal sample volume required and no damage to the sample allowing for reuse. QRS analyzers are compact and portable, enabling on-site analysis near CO2  capture equipment. Furthermore, QRS can potentially measure additional components in the CO2 capture solution, providing a more comprehensive view of system chemistry. By incorporating QRS into your CO2 capture operations, you gain valuable insights for optimizing performance, minimizing downtime, and ensuring long-term system integrity.

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