Post Column Derivatization Using Reaction Flow High Performance Liquid Chromatography Columns
April 26th, 2016
A protocol for the use of reaction flow high performance liquid chromatography columns for methods employing post column derivatization (PCD) is presented.
The overall goal of this method is to improve the efficiency and sensitivity of high performance liquid chromatography post column derivatization, or PCD method, through the use of a reaction flow column. This method can help answer key questions in fields such as pharmaceutical, biomedical, and environmental sciences, where compounds that have low response to HPLC detectors are analyzed. The main advantage of this technique is that no reaction coils are needed.
As mixing of the column effluent and derivatizing reagent occurs more efficiently than conventional methods. This method has been used to provide insight into antioxidants, amino acids, and phenols. It can also be applied to other class compounds, such as thiols, metals, antibiotics, and toxins.
Although the entire sample is not derivatized, due to lower band broadening, the concentration of analyte within the effluent flow stream is higher than in conventional post column derivatization analysis. To begin this procedure, prepare the HPLC instrument with 100%water on Line A and 100%methanol on Line B as the mobile phase, purging the pumps as per the manufacturer's requirements. Set up the HPLC instrumental components and the additional derivatization pump.
Following this, set the UV/VIS detector to analyze at a wavelength of 520 nanometers. Connect the inlet of the reaction flow, or RF, column to the HPLC instrument. Connect an outlet peripheral port to the UV/VIS detector using a 15 centimeter length of 0.13 millimeter inner diameter tubing.
Next, connect the DPPH pump line to a peripheral port on the outlet of the RF column. Block the unused peripheral port on the outlet of the RF column using a column stopper. Connect a 15 centimeter length of 0.13 millimeter inner diameter tubing to the outlet central port of the RF column.
Bring the flow rate of the HPLC pump to one millimeter per minute at 100%methanol. Then equilibrate the column with 100%methanol for 10 minutes. At this point, prepare a 0.1 milligram per milliliter solution of DPPH and methanol.
Sonicate the flask containing the DPPH reagent for 10 minutes. Purge the DPPH pump with the prepared DPPH reagent as per the manufacturer's requirements. Following this, take two dry and clean vessels and label one as central"and the other as peripheral"Accurately weigh the two vessels.
Collect the effluent exiting the central port into the vessel labeled central"for one minute. After reweighing the central port vessel, calculate the weight of the flow from the central port. Repeat the previous steps for the effluent exiting the UV/VIS that is attached to the peripheral port of the RF column.
Calculate the weight for the peripheral port vessel. Next, calculate the percentage of the flow coming from the central and peripheral ports. Repeat the previous steps until the flow ratio is correct, then set the flow rate of the DPPH pump to 0.5 milliliters per minute.
Once the run has finished, stop the derivatization reagent pump flow. Remove the DPPH reagent pump line from the peripheral port and stopper the port. Equilibrate the column with the mobile phase in which it is to be stored, allowing the mobile phase to pass through the column at one millimeter per minute for 10 minutes.
Then, stop the flow of the bubble phase pump on the HPLC instrument. Finally, replace the DPPH reagent with methanol and purge the additional pump. Two chromatograms of a ristretto coffee sample, derivatized with a DPPH radical using both conventional PCD and RF-PCD instrumentation, are shown here.
The calculated limits of quantitation and detection for each of the amino acids analyzed in both RF-PCD and conventional PCD modes are listed here. A chromatogram of the four amino acids analyzed using the conventional PCD method, the RF-PCD method, and the un-derivatized stream from the RF-PCD method is shown here. A comparison of the signals obtained for the peaks due to glycine and leucine using both the conventional PCD and RF-PCD methods is displayed here.
A comparison of the peak width of the tryptophan peak when analyzing using the conventional PCD method, the RF-PCD method, and the un-derivatized stream from the RF-PCD method is shown here. A 21-component test sample that contained some components that show a response to the derivatization scheme and some that do not were separated, derivatized, and detected. The same mixture was also separated and detected un-derivatized for comparison.
A comparison of the peak shape of para-Cresol, both derivatized using the RF-PCD column and un-derivatized, is shown here. Once mastered, this technique can be set up in the same time as conventional post column derivatization analysis. When performing this procedure, it is important to remember to be as close to the prescribed flow ratios as possible.
Following this procedure, other post column derivatization reagents, such as OPA, ninhydrin, or halogens can be used in order to analyze other compounds. After watching this video, you should have a good idea of how to set up and tune a reaction flow column.
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Overview
This article presents a protocol for enhancing the efficiency and sensitivity of high performance liquid chromatography (HPLC) post column derivatization (PCD) using reaction flow columns. This method is particularly useful in analyzing compounds with low responses to HPLC detectors across various scientific fields.
Key Study Components
Area of Science
- Pharmaceutical Sciences
- Biomedical Sciences
- Environmental Sciences
Background
- High performance liquid chromatography is widely used for compound analysis.
- Post column derivatization improves detection sensitivity.
- Conventional methods often require reaction coils, which this method eliminates.
- Efficient mixing of column effluent and reagents is achieved.
Purpose of Study
- To improve the efficiency of HPLC PCD methods.
- To analyze compounds with low detector responses.
- To provide insights into various classes of compounds.
Methods Used
- Use of reaction flow high performance liquid chromatography columns.
- Post column derivatization techniques.
- Analysis of antioxidants, amino acids, and phenols.
- Application to thiols, metals, antibiotics, and toxins.
Main Results
- Enhanced efficiency and sensitivity in compound detection.
- Elimination of reaction coils improves method performance.
- Successful application across multiple compound classes.
- Insights gained into complex biochemical interactions.
Conclusions
- The reaction flow column method significantly improves HPLC PCD.
- This technique is versatile for various scientific applications.
- Future studies can expand its use in other analytical fields.
Frequently Asked Questions
Executive Industry Relevance
Post column derivatization (PCD) enhances detection sensitivity for low-response analytes in pharmaceutical and biomedical research, but conventional methods suffer from band broadening due to large reaction coils. Reaction flow PCD (RF-PCD) eliminates this limitation by enabling efficient mixing within the column, improving separation efficiency and signal-to-noise ratio. This advancement supports reliable quantification of compounds such as amino acids, antioxidants, and phenols, directly impacting assay sensitivity in early discovery workflows.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables detection of underivatized analytes from the central port, allowing parallel monitoring of native and modified species for mechanistic insight.
- Operational Value: Eliminates reaction coils, reducing system dead volume and minimizing band broadening to preserve chromatographic resolution.
Screening & Assay Development
- Scientific Value: Improves signal-to-noise ratio for low-abundance compounds, enhancing detection limits in antioxidant, amino acid, and phenol assays.
- Operational Value: Uses standard HPLC components with a derivatization pump, enabling straightforward integration into existing analytical platforms.
Translational & Preclinical Research
- Scientific Value: Supports analysis of diverse compound classes including thiols, metals, antibiotics, and toxins, broadening applicability across safety and metabolite profiling studies.
- Operational Value: Maintains compatibility with UV/VIS detection at 520 nm, allowing seamless adoption without requiring new instrumentation.
Pipeline & Workflow Integration
RF-PCD fits within the discovery continuum by improving detection reliability in early-stage screening, where sensitive quantification of bioactive compounds informs lead identification and prioritization.
- Discovery Biology: Enhances confidence in detecting low-response metabolites and biomarkers by improving analytical sensitivity without derivatization inefficiencies.
- Screening: Delivers quantitative, reproducible outputs through minimized reaction volume and efficient mixing, supporting high-throughput compound evaluation.
- Analytics: Enables direct comparison of derivatized and underivatized streams, providing internal controls for assay validation and data normalization.
- Translational Research: Facilitates continuous monitoring of analytes from discovery through preclinical studies by preserving analyte integrity and detection fidelity.
- Enterprise Reuse: Leverages existing HPLC infrastructure with minimal added complexity, promoting cross-departmental standardization and method portability.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in analyte detection by reducing false negatives from insensitivity and improving signal clarity.
- Operational Value: Improves reproducibility and scalability by removing variability associated with reaction coil preparation and mixing efficiency.
- Strategic Value: Supports better go/no-go decisions in lead optimization by delivering more accurate structure-activity relationship data from sensitive detection.
- Portfolio Impact: Enables risk-adjusted advancement of candidates by improving data quality in early ADME and toxicity screening assays.
Implementation Considerations
- Requires expertise in HPLC method development and flow rate optimization to balance derivatization reagent and mobile phase flows.
- Needs a dedicated derivatization pump and compatible tubing (0.13 mm ID) for precise reagent delivery to peripheral ports.
- Demands standardization of flow ratios between central and peripheral ports to ensure consistent derivatization efficiency across runs.
- Involves routine maintenance such as purging and equilibration steps to prevent reagent carryover and ensure column stability.
- Limited to one- or two-component derivatization reactions where both reagents can be introduced simultaneously via peripheral ports.
