Meeting EU Drinking Water Standards: The Critical Role of Sample Prep in Trace Contaminant Analysis

<h3>Charged for Action: The Hidden Secrets of AEX Oligonucleotide Analysis</h3>Oligonucleotides—short, well-defined fragments of DNA or RNA—have become indispensable tools in modern life sciences. They underpin cutting-edge applications in molecular diagnostics, gene therapy, and pharmaceutical development. Before oligonucleotides can be confidently used in research or clinical settings, however, their quality must be rigorously assessed. Purity, sequence integrity, length distribution, and chemical modifications all play a decisive role in their performance.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_2_45eee54fa0.jpg" alt="KNAUER: Oligos Made Easy - Part 2: AEX" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_2_45eee54fa0.jpg 245w," sizes="100vw" width="1534" height="711">Among the analytical techniques available today, anion exchange chromatography (AEX) stands out as a robust and highly informative method for characterizing oligonucleotides. By exploiting their intrinsic negative charge, AEX provides detailed insight into product composition and impurity profiles that are difficult to obtain by other approaches.<blockquote><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/article/6808">Part 1 of the Oligos series: A Practical Guide to Oligonucleotide Production – From Concept to Final Product</a></blockquote><h4>How Scientists Read Oligonucleotides Using Charge</h4>At the core of AEX lies a simple but powerful principle: oligonucleotides carry a negatively charged phosphate backbone. This charge increases in a predictable way with strand length and, to a lesser extent, sequence composition. Anion exchange chromatography uses this property to separate oligonucleotides based on differences in charge strength and interaction with a positively charged stationary phase.As a result, AEX has become one of the most widely used analytical tools for evaluating oligonucleotide quality. It allows scientists to distinguish full-length products from truncated species, degradation products, or closely related variants—often with single-nucleotide resolution.<h4>Why Ion Exchange Works: Binding, Retention, and Release</h4>Ion exchange chromatography (IEX) relies on electrostatic interactions between analytes and a charged stationary phase. In the case of oligonucleotides, anion exchange is used, where negatively charged molecules interact with positively charged functional groups on the resin—most commonly quaternary amines.The system consists of two main components:<ul><li>Stationary phase: A positively charged resin that binds anionic analytes.</li><li>Mobile phase: An aqueous buffer system, typically combined with a salt gradient, that controls both pH and elution strength.</li></ul>Retention in AEX is governed primarily by charge. Molecules with weaker overall charge interact less strongly with the stationary phase and elute earlier, while more highly charged oligonucleotides bind more tightly and require stronger elution conditions.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_1_IEX_overview_including_elution_order_dependency_on_analyte_charge_3419ad3075.jpg" alt="KNAUER: Oligos Made Easy - Part 2 AEX: Figure 1 IEX overview including elution order dependency on analyte charge." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_1_IEX_overview_including_elution_order_dependency_on_analyte_charge_3419ad3075.jpg 245w," sizes="100vw" width="1583" height="654"><h4>The Five-Step Workflow of Ion Exchange Chromatography</h4>AEX separations generally follow a well-established sequence of steps:<ol><li>Column equilibration The column is conditioned with the starting buffer until the baseline and pH are stable. This ensures that all charged sites on the resin are ready for interaction.</li><li>Sample loading Samples, prepared in the starting buffer, are introduced under conditions that promote binding of the target oligonucleotides while minimizing retention of unwanted impurities.</li><li>Washing The column is washed with the starting buffer to remove uncharged or weakly interacting components. The baseline stabilizes as these species are flushed away.</li><li>Elution Bound oligonucleotides are released using a salt or pH gradient. Increasing ionic strength introduces competing ions that displace the analytes from the resin. Weakly bound species elute first; strongly charged oligonucleotides elute later.</li><li>Regeneration and re-equilibration A high-salt buffer removes any remaining bound material. The column is then returned to starting conditions in preparation for the next analysis.</li></ol><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_2_Five_steps_of_IEX_procedure_in_blue_outlined_using_an_example_chromatogram_in_red_38dd70b1b1.jpg" alt="KNAUER: Oligos Made Easy - Part 2 AEX: Figure 2 Five steps of IEX procedure (in blue), outlined using an example chromatogram (in red)." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_2_Five_steps_of_IEX_procedure_in_blue_outlined_using_an_example_chromatogram_in_red_38dd70b1b1.jpg 245w," sizes="100vw" width="1583" height="674"><h4>Why AEX Is Especially Effective for Oligonucleotides</h4>The repeating phosphate backbone of oligonucleotides gives rise to a strong and uniform anionic character across a wide pH range (typically pH 7–9). This makes oligonucleotides exceptionally well suited for anion exchange separations.Key factors influencing AEX behavior include:<ul><li>Charge density: Longer oligonucleotides carry more negative charges and therefore exhibit stronger retention.</li><li>Resin chemistry: Strong and weak anion exchangers differ in functional groups and pH stability, influencing selectivity and robustness.</li><li>Buffer composition: The choice of buffering ions and salt gradients directly affects elution strength and resolution.</li></ul>Salt gradients—commonly based on chloride ions—compete with the oligonucleotide backbone for binding sites on the resin. By carefully tuning gradient slope and composition, analysts can achieve highly reproducible and finely resolved separations.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_3_Ionic_interactions_and_p_H_influence_on_Anion_Exchange_Chromatography_AEX_612e231ba4.jpg" alt="KNAUER: Oligos Made Easy - Part 2 AEX: Figure 3 Ionic interactions and pH influence on Anion Exchange Chromatography (AEX)." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_3_Ionic_interactions_and_p_H_influence_on_Anion_Exchange_Chromatography_AEX_612e231ba4.jpg 245w," sizes="100vw" width="1547" height="593"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_4_AEX_buffer_selection_and_gradient_strategy_chromatogram_with_red_buffer_gradient_curve_53fd1bb11b.jpg" alt="KNAUER: Oligos Made Easy - Part 2 AEX: Figure 4 AEX buffer selection and gradient strategy (chromatogram with red buffer gradient curve)." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_4_AEX_buffer_selection_and_gradient_strategy_chromatogram_with_red_buffer_gradient_curve_53fd1bb11b.jpg 245w," sizes="100vw" width="1600" height="327"><h4>AEX as the Gold Standard for Oligonucleotide Separation</h4>Anion exchange chromatography has become the method of choice for both analytical and preparative oligonucleotide workflows. Its advantages include:<ul><li>High resolving power: Closely related impurities, including n–1 or n–2 species, can often be separated and quantified.</li><li>Predictable retention behavior: In many cases, retention time correlates linearly with oligonucleotide length, simplifying identification.</li><li>Compatibility with modified oligonucleotides: Even chemically modified sequences retain their anionic nature, allowing AEX to resolve both products and related impurities.</li><li>Excellent control via gradient elution: Salt gradients provide precise tuning of selectivity and resolution.</li></ul>Typically, shorter or degraded oligonucleotides elute at lower ionic strength, while full-length products with higher charge density appear later in the chromatogram.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_5_AEX_Advantages_and_Challenges_7835521e34.jpg" alt="KNAUER: Oligos Made Easy - Part 2 AEX: Figure 5 AEX Advantages and Challenges." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_KNAUER_Oligos_Made_Easy_Part_2_AEX_Figure_5_AEX_Advantages_and_Challenges_7835521e34.jpg 245w," sizes="100vw" width="1535" height="707"><h4>Final Perspective: Mastering AEX with Confidence</h4>Anion exchange chromatography may appear complex at first, but with thoughtful optimization of pH, buffer composition, and gradient conditions, it becomes a highly precise and reliable tool for oligonucleotide analysis. When properly applied, AEX delivers sharp peaks, excellent resolution, and robust performance—even for challenging sequences and modifications.For laboratories developing or refining oligonucleotide workflows, AEX offers both analytical depth and operational confidence.<blockquote>If you would like to discuss AEX method development or optimization for oligonucleotides, feel free to contact us at sales@knauer.net. More insights into practical oligonucleotide analysis will follow in our “Oligos Made Easy” series.For technical questions or in-depth discussion, the author can be reached at kindler@knauer.net</blockquote>

Oligos Made Easy - Part 2: AEX

Although modern agriculture needs to be based on accurate real-time data on soil, plant, and environmental conditions, affordable, sufficiently sensitive, and robust monitoring devices for this purpose are currently missing. According to scientists, low-cost sensors based on new smart materials and printing technologies offer a suitable solution. The results of multidisciplinary research thus far and proposals for the development of these devices have been presented by researchers from Czechia, Great Britain, Spain, and the USA in a review article in the prestigious journal <a target="_blank" rel="noopener noreferrer" href="https://www.nature.com/articles/s41467-026-68778-6#Abs1">Nature Communications</a>.“Sensor technologies for monitoring plant health are still in their infancy. Only simple sensors capable of monitoring basic parameters such as pH, soil moisture, or temperature are commonly available on the market. However, if farmers are to face current challenges, including climate change, and ensure sufficient food for humanity, they need much more effective tools that will enable them to monitor, for example, various pathogens, including bacteria and fungi. In our opinion, a suitable solution is a combination of new smart materials and printing for the production of inexpensive, durable, and scalable materials,” said the article’s first author, David Panáček from CATRIN, who worked on the study during his internship at Imperial College London.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/CATRIN_Soucasne_senzory_nestaci_Vedci_navrhuji_novou_cestu_ke_sledovani_zdravi_rostlin_b4014952a3.jpg" alt="CATRIN: David Panáček" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_CATRIN_Soucasne_senzory_nestaci_Vedci_navrhuji_novou_cestu_ke_sledovani_zdravi_rostlin_b4014952a3.jpg 208w," sizes="100vw" width="1536" height="1152">Sensors for monitoring plant health, for example, lag behind similar devices used in human medicine. According to the authors, advances in materials science, which will enable the development of scalable sensor technologies, play a key role in this potential shift. “Printing techniques, including inkjet printing, screen printing, aerosol printing, 3D printing, and direct laser writing, offer flexible ways to produce flexible sensors, large-area sensors, and sensors integrated directly into plants. The review article summarizes recent advances in printable low-dimensional materials for agricultural sensors, analyzes their physico-chemical properties in relation to sensor performance, and discusses key challenges and future opportunities requiring interdisciplinary integration,” said one of the corresponding authors, Michal Otyepka.The research brought together materials scientists, chemists, biologists, sensing experts, and printing technology specialists. Materials research and the use of graphene-based smart materials were led by scientists from CATRIN at Palacký University and VŠB-Technical University of Ostrava. Plant biologists from CATRIN contributed their knowledge of plant development, their responses to stress conditions, and the monitoring of their properties. Researchers from Imperial College London took care of the electronics, while representatives from<a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/companies/36"> CEITEC – VUT</a> focused on printing technologies. The team also included leading experts in sensing from the Catalan Institute of Nanoscience and Nanotechnology in Barcelona, and Joseph Wang of the University of California San Diego, the “father of sensing and electrochemistry,” also contributed his extensive knowledge.“This is a groundbreaking study on this topic, which has managed to attract some truly big names in their respective fields. Last but not least, the study demonstrates that interdisciplinarity at CATRIN gives rise to completely new and promising research topics, such as plant sensing and its use for studying plant-environment interactions and smart agriculture,” added another corresponding author, Nuria De Diego.

Current sensors are not good enough. Scientists propose a new way to monitor plant health

Article

Environment

Scientific article

Science and research

Video

The Czech Advanced Technology and Research Institute (CATRIN) at Palacký University is a cutting-edge scientific hub dedicated to advancing research in the fields of nanotechnology, biotechnology, and biomedicine. At its core, CATRIN boasts outstanding scientific teams, featuring international researchers. We emphasize interdisciplinarity, foster global collaborations, and work to translate our research findings into practical applications.

CATRIN

Organomation, founded in 1959, designs and manufactures high-quality nitrogen evaporators and extraction systems. Known for innovation and durability, their lab instruments are used globally for efficient sample preparation with strong customer support.

Organomation

Based in Berlin, KNAUER is a medium-sized, owner-managed company that has been serving the sciences since 1962. We develop and manufacture scientific instruments of superior quality for liquid chromatography, including: Analytical HPLC/UHPLC, Preparative HPLC, Fast protein liquid chromatography (FPLC), Multi-column chromatography/Simulated moving bed (SMB) chromatography. High pressure dosing, in-line detection systems, and osmometry are additional business areas.

KNAUER

Watrex Deltasil 100 C18 HPLC columns

Need a high quality column at an affordable price? Deltasil™ columns are filled with standard reversed phase for a wide range of applications.

<a target="_blank" rel="noopener noreferrer" href="https://watrex.com/?s=watrex+deltasil+100+C18&amp;post_type=product&amp;dgwt_wcas=1?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex DeltaSil™ 100 C18</a> column is a standard reversed phase for wide field of applications in analysis of drugs, organic compounds, peptides and others.Stationary phase is based on synthetic 5 μm silica-gel with 100 Å pores and 15% carbon content. The column has a good peak symmetry and efficiency.Theoretical plate count value for non-polar compounds, such as naphthalene, reaches up to 90.000 theoretical plates per meter.A wide range of column sizes is available, with additional dimensions available on request.We are committed to the sustainability of our columns and therefore also offer backfill.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Watrex_Deltasil_HPLC_column_Mobile_phase_85_ACN_Flowrate_0_65_mlmin_Pressure_54_bar_Detection_254_nm_Injection_2_ml_de7068538f.jpg" alt="Watrex: Watrex Deltasil HPLC column (Mobile phase 85% ACN; Flowrate 0.65 mlmin; Pressure 54 bar; Detection 254 nm; Injection 2 μl)"><h3>Ordering information:</h3><h5>PN/Component:</h5><ul><li>WI02DC181254 Watrex Deltasil™ 100 C18, 5 μm, 125x4 mm column (Price 234 € ex VAT)</li><li>WI02DC181504 Watrex Deltasil™ 100 C18, 5 μm, 150x4 mm column (Price 234 € ex VAT)</li><li>WI02DC1815046 Watrex Deltasil™ 100 C18, 5 μm, 150x4,6 mm column</li><li>WI02DC182504 Watrex Deltasil™ 100 C18, 5 μm, 250x4 mm column (Price 296 € ex VAT)</li><li>WI02DC1825046 Watrex Deltasil™ 100 C18, 5 μm, 250x4,6 mm column</li><li>WI02DC182508 Watrex Deltasil™ 100 C18, 5 μm, Semi-prep 250x8 mm column (Price 482 € ex VAT)</li></ul>

Watrex Polymer IEX HPLC columns

Do you need HPLC columns for the determination of organic acids, alcohols and sugars? Columns filled with a monodisperse sorbent based on sulfonated styrenedivinylbenzene.

<a target="_blank" rel="noopener noreferrer" href="https://watrex.com/?s=watrex+polymer+iex&amp;post_type=product&amp;dgwt_wcas=1?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex Polymer IEX™</a> is the Europe’s leading sorbent for ion exclusion analysis of alcohols, carboxylic acids, sugars, and polysacharides<ul><li>H⁺, Ca²⁺, Pb²⁺ and Na⁺ forms</li><li>Unique monodispersed sorbent based on sulfonated polystyrene</li><li>Bulk packing materials available</li></ul><h3>H form</h3>The hydrogen form is suitable for organic acids, alcohols and some sugars in natural materials. The column is particularly suitable for the analysis of fruit drinks, wine, etc. Its great advantage is the high stability of retention times and the wide concentration range of analytes.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Column_250x8mm_IEX_H_4da682fa13.jpg" alt="Watrex: Column 250x8mm IEX H"><h3>Ca form</h3>The calcium form is characterized by good selectivity for the separation of mono- and disaccharides in natural materials. The column must be protected from anions forming insoluble calcium salts (phosphates, sulphates, etc.) and cations with a higher affinity for the sorbent than calcium ions.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Column_250x8mm_IEX_Ca_b840dddcce.jpg" alt="Watrex: Column 250x8mm IEX Ca"><h3>Pb form</h3>The lead form is suitable for the separation of mono- and disaccharides in natural materials. The column must be protected from anions forming insoluble lead salts (phosphates, sulphates, etc.) and cations with a higherUse the appropriate pre-column to extend the life of the analytical column.<h3>Ordering information:</h3><h5>PN/Component:</h5><ul><li>WI020223 Watrex 300x8 mm Polymer IEX H form, 8 um</li><li>WI020213 Watrex 300x8 mm Polymer IEX Ca form, 8 um</li><li>WI020253 Watrex 300x8 mm Polymer IEX Pb form, 8 um</li><li>WI02022 Watrex 250x8 mm Polymer IEX H form, 8 um (Price 926 € ex VAT)</li><li>WI02021 Watrex 250x8 mm Polymer IEX Ca form, 8 um (Price 926 € ex VAT)</li><li>WI02025 Watrex 250x8 mm Polymer IEX Pb form, 8 um (Price 926 € ex VAT)</li><li>WI02122 Guard column insert 10x4.0 mm PEEK Polymer IEX H 8 um, 10 pcs</li><li>WI02121 Guard column insert 10x4.0 mm PEEK Polymer IEX Ca 8 um, 10 pcs</li><li>WI029012 Guard column holder (for 10x4.0 mm PEEK insert)</li></ul>

Watrex IonPlus HPLC columns

Do you perform cation or anion analysis and need the right column at an affordable price? Our Watrex IonPlus™ columns are just what you are looking for!

Watrex IonPlus™ are special columns for ion chromatography. The matrix used is styrene-divinylbenzene based and can withstand higher organic modifier content in the mobile phase.<h3><a target="_blank" rel="noopener noreferrer" href="https://watrex.com/obchod/chromatography/hplc-columns/watrex-columns/ion-exchange/watrex-ionplus-cs19-ic-column-250x46mm/?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex IonPlus™ CS19</a></h3><ul><li>Styrene-divinylbenzene, 55% cross-linking (7 μm particle i.d.)</li></ul>The Watrex IonPlus™ CS19 is an optimized column designed for the separation of common cations, small polar amines and moderately hydrophobic and polyvalent cations using simple aqueous eluents and elevated temperatures. They provide excellent separation of alkali metals, alkaline earth metals, alkylamines, alkanolamines and biogenic amines.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/HPLC_kolona_Watrex_Ion_Plus_CS_19_738c29ff57/HPLC-kolona-Watrex-IonPlus-CS19.png" alt="Watrex: Separation of anions in a Watrex IonPlus CS19 HPLC column"><h3><a target="_blank" rel="noopener noreferrer" href="https://watrex.com/obchod/chromatography/hplc-columns/watrex-columns/ion-exchange/watrex-ionplus-as19-ic-column-250x46mm/?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex IonPlus™ AS19</a></h3><ul><li>Styrene-divinylbenzene, 55% cross-linking (12 μm particle i.d.).</li></ul>Watrex IonPlus™ AS19 is a column analyzing common inorganic anions including fluorides, chlorites, bromates, chlorides, nitrates, phosphates and sulphates in drinking, underground and waste water or other matrices.<h3><a target="_blank" rel="noopener noreferrer" href="https://watrex.com/obchod/chromatography/hplc-columns/watrex-columns/ion-exchange/watrex-150x4mm-ic-anion-i-7um/?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex IC Anion I</a></h3><ul><li>Styrene-divinylbenzene (7 μm particle i.d.)</li></ul><h3>Ordering information:</h3><h5>PN/Component:</h5><ul><li>WCS19250046 Watrex IonPlus™ CS19 IC Column 250x4,6mm, 7 um (Price 1 169 € ex VAT)</li><li>WCS19150030 Watrex IonPlus™ CS19 IC Column 150x3mm, 7 um</li><li>WCS19150040 Watrex IonPlus™ CS19 IC Column 150x4mm, 7 um</li><li>WCS19250030 Watrex IonPlus™ CS19 IC Column 250x3mm, 7 um</li><li>WAS19250046 Watrex IonPlus™ AS19 IC Column 250x4,6mm, 7 um (Price 1 090 € ex VAT)</li><li>WAS19150030 Watrex IonPlus™ AS19 IC Column 150x3mm, 7 um</li><li>WAS19150040 Watrex IonPlus™ AS19 IC Column 150x4mm, 7 um</li><li>WAS19250030 Watrex IonPlus™ AS19 IC Column 250x3mm, 7 um</li><li>WAS1925046 Watrex IonPlus™ AS19 IC Column 250x4.6mm, 12 μm</li><li>WI021540 Watrex IC Anion I 150x4mm, 7 μm (Price 731 € ex VAT)</li><li>CAT12546 WATREX 125×4.6mm Universal Cat II, 7um (Price 584 € ex VAT)</li></ul>

Products from category Analytical HPLC columns focused on LC columns distributed by WATREX Prague - page 1

Related content

Current sensors are not good enough. Scientists propose a new way to monitor plant health

Meeting EU Drinking Water Standards: The Critical Role of Sample Prep in Trace Contaminant Analysis

Oligos Made Easy - Part 2: AEX