Pesticides and biocides are widely used in agriculture, building materials, and urban gardening to control pests and protect crops and public health. While much attention has been paid to pesticide residues in food, water, and outdoor environments, far less is known about their presence inside homes, where people spend the majority of their time. A new RECETOX study published in Indoor Environments addresses this gap by examining pesticides detected in house dust and their relevance for human exposure.&nbsp;The study reveals that Czech household dust commonly contains multiple pesticide residues, highlighting the persistence of both historic and current chemical use indoors. Modern pesticides were detected in 93% of homes, with two fungicides (carbendazim and propiconazole) most frequently found, while compounds related to the long‑banned pesticide DDT were present in dust from all homes, and were at higher levels in homes over 40 years old. Homes located closer to agricultural areas showed higher levels of current‑use pesticides in spring, indicating an influence of nearby farming activities. &nbsp;House dust acts as a sink for chemicals transported indoors from outdoor sources as well as from indoor use. Many pesticides can persist in dust for long periods, leading to continuous exposure in indoor spaces. This is particularly important for young children, who have higher exposure to dust from playing on the floor and mouthing toys and objects. The research underscores that indoor environments are not isolated from their surroundings. Understanding what ends up in house dust is a crucial step toward protecting public health and developing more comprehensive approaches to managing chemical risks in everyday life.&nbsp;<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/RECETOX_Vyzkum_pesticidu_v_domacim_prachu_opomijena_cesta_lidske_expozice_a9a089fd2f.jpg" alt="RECETOX: Pesticides in House Dust: An Overlooked Pathway of Human Exposure" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_RECETOX_Vyzkum_pesticidu_v_domacim_prachu_opomijena_cesta_lidske_expozice_a9a089fd2f.jpg 195w," sizes="100vw" width="738" height="591"><blockquote><h4>Original Article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://www.sciencedirect.com/science/article/pii/S2950362026000214?via%3Dihub">Legacy and current-use pesticides in indoor settled dust and association with building age and seasonality</a></h4>Paula Marcinekova, Ondřej Mikeš, Simona Rozárka Jílková, Petr Šenk, Jakub Martiník, Jan Böhm, Petra Borilova Linhartova, Lenka Andrýsková, Jana Klánová, Lisa MelymukIndoor Environ., 2026, 3, 100169<a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1016/j.indenv.2026.100169">https://doi.org/10.1016/j.indenv.2026.100169</a>&nbsp;<h6>licensed under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/">CC-BY 4.0</a></h6></blockquote><h4>Abstract</h4>Indoor pesticide exposure is increasingly recognized as a significant contributor to pollutant exposure in residential spaces. This study investigates concentrations of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) in settled dust from 116 homes in the Czech Republic, in the context of their seasonal variability, relationships with building characteristics, geospatial factors, and indoor dust bacteriome diversity and composition. CUPs were detected in dust in 93% of homes, with carbendazim (84.5%), propiconazole (49.1%), atrazine (24.1%), and tebuconazole (11.2%) detected most frequently. OCPs were found in all homes. Propiconazole concentrations were significantly higher in homes with adjacent gardens, potentially reflecting its use as a biocide in outdoor building materials. CUP concentrations had clear seasonal trends, with peak levels in spring and summer, corresponding to pesticide application periods, particularly in rural environments. OCP concentrations were substantially higher in houses over 40 years old, indicating the persistence of residues from past indoor uses. While pesticide presence was ubiquitous, exposure estimates for children, under both average and high-exposure scenarios, were well below U.S. EPA reference doses (RfDs) for individual compounds; however, most homes had 3–11 pesticides in dust, raising the possibility of mixture effects. No significant associations, using a Spearman rank correlation matrix, were observed between pesticide concentrations and indoor dust bacteriome diversity and composition. These findings highlight the presence of pesticides in homes, including those in urban areas, driven by both current and historical sources, and reinforce the importance of monitoring to better understand potential exposure pathways.<h4>Instrumentation</h4><h5>1. LC–MS/MS analysis of CUPs</h5><ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?instrumentationItems=27&amp;mainauthorItems=10&amp;search=1290+Series+Gradient">Agilent 1290 Series Gradient HPLC</a></li><li>Columns:<ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1701">Phenomenex Luna C18</a></li><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?instrumentationItems=34&amp;mainauthorItems=50&amp;search=SecurityGuard+C18">Phenomenex SecurityGuard C18</a></li></ul></li><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/library?mainauthorItems=55&amp;search=QTrap+5500%2B">SCIEX QTrap 5500+</a> (triple quadrupole MS, ESI+)</li></ul><h5>2. GC–MS/MS analysis of OCPs</h5><ul><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?instrumentationItems=1&amp;mainauthorItems=10&amp;search=8890A">Agilent 8890A GC</a></li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?instrumentationItems=19&amp;mainauthorItems=7&amp;search=Rxi-5Sil-MS">Restek Rxi-5Sil-MS capillary column</a></li><li><a target="_blank" rel="noopener noreferrer" href="https://gcms.labrulez.com/library?mainauthorItems=10&amp;search=7000D">Agilent 7000D triple quadrupole MS</a></li></ul>

Pesticides in House Dust: An Overlooked Pathway of Human Exposure

This technical note presents a practical troubleshooting strategy for one of the most common issues in liquid chromatography (LC): shifting retention times. The approach is based on a systematic distinction between system-related (physical) and chromatographic (chemical) causes.A key diagnostic parameter used throughout the process is the T₀ (dead time), representing an unretained peak that passes through the column without interaction.<h3>Key Concept: T₀ (Dead Time / Unretained Peak)</h3>T₀ is defined as the retention time of a compound that does not interact with the stationary phase and therefore elutes directly with the mobile phase.<h4>How to Determine T₀</h4>T₀ can be determined experimentally by adding a marker compound to the system:<ul><li>Uracil</li><li>Potassium nitrate</li></ul>These compounds are added to a blank or method and produce a measurable unretained peak used for troubleshooting.<h3>Step 1: Evaluate T₀ Behavior</h3>The first and most important step is to determine whether T₀ is constant or variable.<ul><li>Case A: T₀ is Variable (Shifting) → Indicates a system-related (physical) problem &nbsp;</li><li>Case B: T₀ is Constant → Indicates a chromatographic or chemical problem</li></ul><h3>System-Related Issues (T₀ is Variable)</h3>If T₀ is shifting, the problem is likely related to the LC system hardware or physical parameters. This is especially true when all peaks shift together in the chromatogram.<h3>Possible Causes</h3><ul><li>Incorrect Flow Rate</li><li>Pump Malfunction<ul><li>Inconsistent or unstable flow delivery can cause retention time variability.</li></ul></li><li>Incorrect Column Length<ul><li>Using a column with different dimensions than expected.</li></ul></li><li>Solvent Delivery Issues<ul><li>Empty solvent reservoir (system running dry)</li><li>Blockages or restrictions (e.g., frits, solvent lines)</li></ul></li><li>Tubing or System Volume Changes<ul><li>Changes in tubing configuration</li><li>Differences in system dwell (swell) volume</li></ul></li></ul><h3>Chromatographic / Chemical Issues (T₀ is Constant)</h3>If T₀ remains stable but only specific peaks shift, the issue is likely related to chemistry or column conditions.<h4>Possible Causes</h4><ul><li>Incorrect Stationary Phase<ul><li>Column with same dimensions but different chemistry (e.g., different silica or bonded phase)</li></ul></li><li>Ionizable Analytes Ionizable compounds exist in:<ul><li>Neutral form - More hydrophobic, retained longer on a reversed-phase column</li><li>Ionized form</li></ul>Impact of pH Small pH changes in the mobile phase can significantly affect:<ul><li>Ionization state</li><li>Retention time of specific analytes</li></ul></li><li>Mobile Phase Issues<ul><li>Old solvents</li><li>Evaporation of volatile components</li><li>Changes in composition</li></ul></li><li>4. Temperature Variations<ul><li>Temperature affects analyte–stationary phase interactions</li><li>Even small fluctuations can shift retention times</li></ul></li></ul><h3>Step-by-Step Troubleshooting Workflow</h3><ol><li>Add T₀ Marker<ol><li>Use uracil or potassium nitrate</li></ol></li><li>Monitor T₀<ol><li>Determine whether it is constant or shifting</li></ol></li><li>If T₀ is Variable → Check System<ol><li>Flow rate settings</li><li>Pump performance</li><li>Solvent levels and lines</li><li>Column dimensions</li><li>Tubing and system volume</li></ol></li><li>If T₀ is Constant → Check Chemistry<ol><li>Column phase</li><li>Mobile phase composition and pH</li><li>Solvent quality</li><li>Temperature stability</li><li>Nature of analytes (ionizable vs. non-ionizable)</li></ol></li></ol><h3>Discussion and Practical Insight</h3>This troubleshooting approach simplifies a complex problem by dividing it into two main categories:<ul><li>Physical/system-related</li><li>Chemical/chromatographic</li></ul>The use of T₀ as a diagnostic tool allows rapid identification of the problem origin, reducing unnecessary trial-and-error steps.Particular attention should be paid to ionizable compounds, as they are highly sensitive to pH variations, which can lead to significant and selective retention time shifts.<h3>Conclusion</h3>Retention time shifts in LC can be efficiently diagnosed by evaluating the behavior of the T₀ (unretained peak):<ul><li>Variable T₀ → System issue</li><li>Constant T₀ → Chromatographic/chemical issue</li></ul>By following this structured approach, analysts can quickly narrow down the root cause and implement targeted corrective actions.

Troubleshooting Retention Time Shifts in Liquid Chromatography 

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RECETOX (Research Centre for Toxic Compounds in the Environment) is an independent department of the Faculty of Science of Masaryk University in Brno, which has been established in 1983. RECETOX is focused on the research and education in cross-cutting area of Environment and Health. It addresses interactions among chemicals, environment, and biological systems, including consequences at local, regional, and global levels.

RECETOX - Centrum pro výzkum toxických látek v prostředí

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Waters/Wyatt Optilab On-line Differential Refractometer

The Waters Optilab is a unique dRI detector for standard HPLC/GPC with 256 times the detection power and 50 times the dynamic range of every other RI detector for chromatography in existence today, making it a valuable addition to any MALS setup.

<h4>Independent of Chromaphores</h4>Independent of chromaphores or fluorophores, differential Refractive Index (dRI) detectors serve as accurate and versatile concentration detectors in all types of solvents. dRI is part of standard instrumentation for a variety of macromolecular characterization techniques including standard chromatography, SEC-MALS, FFF-MALS and CG-MALS.<h4>Unique dRI Detector</h4>The Optilab is a unique dRI detector for standard HPLC/GPC with 256 times the detection power and 50 times the dynamic range of every other RI detector for chromatography in existence today, making it a valuable addition to any MALS setup.<h4>Product Description</h4>Using a combination of cutting-edge semiconductor photodiode technology and proprietary computer algorithms, the Optilab achieves an unprecedented combination of sensitivity and range. These features mean that it addresses both standard chromatographic applications and some challenges unique to light scattering measurements such as high concentrations, determination of sample refractive increments (dn/dc) and solvent refractive index.<h5>Key Benefits</h5><ul><li>Extraordinary dRI measurement range, -0.0047 to +0.0047 RIU (comparable to 25 mg/mL protein in PBS)</li><li>Highly sensitive, ±7.5 x 10 -10 &nbsp;RIU across the entire measurement range</li><li>Measures solvent absolute refractive index, required for MALS calculations</li><li>Measures at the same wavelength as the MALS detector, for maximum accuracy in MALS calculations</li><li>Band broadening &lt; 20 µL preserves SEC resolution</li><li>Temperature range 4 °C to 65 °C for proteins and polymers that require a range of temperatures</li><li>High-resolution, touch-screen front panel displays data graphs and diagnostics, even with the host computer turned off</li></ul><h5>Unparalleled Features</h5>Even though the Optilab offers a dRI measurement range orders of magnitude beyond that of other dRI detectors, unlike other detectors there are no range or gain settings in the Optilab. The full range of instrument detection is always present, and the full sensitivity exists over the entire range.The Optilab can also do something no other on-line refractive index detector can: it can measure the absolute refractive index of a solution. In addition, it can measure the dn/dc of a solvent at the same wavelength of light as the light scattering instrument. And just to make sure it can't be matched, you can replace the light source in the Optilab for other wavelengths (e.g., 690, 633, 488, etc.) in just minutes!The Optilab can go below ambient temperatures as easily as above ambient. No hassle temperature control can be programmed from 4 °C to 65 °C. Compatible with all HPLC systems.<h4>Specifications</h4><h5>Measurement Capabilities – Differential Refractive Index</h5>Standard Optilab Configuration<ul><li>Measurement Range: –0.0047 to +0.0047 RIU</li><li>Peak-to-Peak Noise: ±7.5 × 10⁻¹⁰ RIU (Measured per ASTM-E1303-95 at 25 °C)</li></ul>High Concentration (HC) Option<ul><li>Measurement Range: –0.0026 to +0.034 RIU</li><li>Peak-to-Peak Noise: ±1.5 × 10⁻⁹ RIU (Optimized for higher concentration samples)</li><li>Response Time: User-selectable from 0.1 to 5 seconds</li><li>Absolute Refractive Index Measurement Range: 1.2 to 1.8 RIU</li><li>Absolute RI Sensitivity: ±0.002 RIU</li></ul>Fluidics and Flow Properties<ul><li>Band Broadening: &lt;12 µL</li><li>Fill Volume (Inlet Tubing + Flow Cell): 51.4 µL</li><li>Outlet Tubing Volume (0.030" ID): 370 µL</li></ul>Pressure Ratings<ul><li>Inlet Back Pressure (0.5 mL/min H₂O @ 20 °C): &lt;22 psi (1.5 bar)</li><li>Max Outlet Back Pressure: 30 psi (2 bar)</li></ul>Temperature Control<ul><li>Sample Temperature Control Range: 4 °C to 65 °C</li><li>Regulation Stability: ±0.005 °C</li></ul>Light Source Options<ul><li>Standard: 660 nm</li><li>HC Model (Optional): 488 nm, 785 nm, or 940 nm</li></ul>Safety Features<ul><li>Built-in vapor and liquid leak sensors for enhanced lab safety</li></ul>Electronics and Connectivity<ul><li>Digital Output: 22+ bit resolution @ 10 Hz</li><li>Analog Output: ±10 V or ±1 V, 18-bit resolution</li><li>Computer Interface: Ethernet</li></ul>Auxiliary I/O Ports<ul><li>Inputs:<ul><li>Analog In (16-bit, ±10 V A/D)</li><li>Zero dRI</li><li>Purge</li><li>Recycle In</li><li>Autoinject In</li><li>Alarm In</li></ul></li><li>Outputs:<ul><li>Autoinject Retransmit</li><li>Alarm Out</li><li>Recycle Out (controls Orbit™ valve switching)</li></ul></li></ul>User Interface<ul><li>Front Panel Display: 7” (178 mm) high-resolution multi-touch screen for viewing signals, diagnostics, and adjusting instrument settings</li></ul>Instrument Dimensions<ul><li>Size: 58 cm (L) × 36 cm (W) × 18 cm (H)</li></ul><h4>Other Refractive Index Detectors</h4><ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1269">microOptilab™</a> - The first RI detector specifically designed for use with all UHPLC systems.</li></ul>

Waters/Wyatt microOptilab On-line Differential Refractometer

The Waters microOptilab brings the universal detection capabilities, unsurpassed concentration range, and superb sensitivity and linearity

<h4>Independent of Chromaphores</h4>Independent of chromaphores or fluorophores, differential Refractive Index (dRI) detectors measure concentrations of all types of samples in almost all solvents. The microOptilab brings the universal detection capabilities, unsurpassed concentration range, and superb sensitivity and linearity – familiar from the Optilab™ – to the domain of UHPLC.<h4>SEC-MALS with UHPLC</h4>Like standard SEC, UHPLC-SEC analysis relying on column calibration with molecular standards is unreliable when the standards do not accurately reflect your samples in terms of conformation, non-ideal (e.g., hydrophobic) column interactions or reversible association. SEC-MALS employs a microDAWN™ MALS detector downstream of the SEC column and UV detector, to determine molar mass / molecular weight distributions of macromolecules independently of column calibration.Refractive index detection is an important component of any SEC-MALS system, and necessary for analyzing conjugated proteins or polymers devoid of chromaphores. The microOptilab connects with the microDAWN MALS detector for a complete UHP-SEC-MALS setup that transfers the many benefits of SEC-MALS analysis to the realm of UHPLC.<h5>Key benefits</h5><ul><li>Very low band broadening, &lt; 4 µL, to maintain the resolution of very narrow UHPLC peaks</li><li>Extraordinary dRI measurement range, -4.7 x 10 -3 &nbsp;to +4.7 x 10 -3 &nbsp;RIU (comparable to 25 mg/mL protein in PBS)</li><li>Highly sensitive, ± 1.5 x 10 -9 &nbsp;RIU across the entire measurement range</li><li>Measures solvent refractive index, require for MALS calculations</li><li>Measures at the same wavelength as the MALS detector, for maximum accuracy in MALS calculations</li><li>Temperature range 4 °C to 65 °C for proteins and polymers that require a range of temperatures</li><li>High-resolution, touch-screen front panel displays data graphs and instrument diagnostics, even with the host computer turned off</li></ul><h5>Unparalleled features</h5><ul><li>Considering the extremely small peak volumes of UHPLC, band broadening in the microOptilab is kept to the absolute minimum, at less than 4 µL, as compared to 20 - 40 µL or more for standard RI detectors. As a result, the superior resolution from UHPLC columns and instruments will not be compromised with the microOptilab RI detector.</li><li>Even though the microOptilab offers a dRI measurement range orders of magnitude beyond that of other UHPLC dRI detectors, unlike other detectors there are no range or gain settings in the microOptilab. The full range of instrument detection is always present, and the full sensitivity exists over the entire range. The small flow cell and proprietary temperature regulation enable stable RI baselines and signals which further enhance the detector's sensitivity.</li><li>Unlike all other dRI detectors, the microOptilab also measures absolute refractive index in order to determine solvent RI, necessary in light scattering calculations and useful in assessing the accuracy of mixing of solvent gradients.</li><li>The microOptilab can be operated below ambient temperatures as easily as above ambient. No hassle temperature control can be programmed down to 4 °C or as high as 65 °C.</li><li>The microOptilab is compatible with all UHPLC systems.</li></ul><h4>Specifications</h4><h5>Measurement Capabilities – Differential Refractive Index</h5><ul><li>Differential RI Measurement Range: –0.0047 to +0.0047 RIU</li><li>Peak-to-Peak Noise: ±1.5 × 10⁻⁹ RIU (Measured per ASTM-E1303-95 at 25 °C with a 0.5 sec collection interval)</li><li>Response Time: User-selectable from 0.04 to 5 seconds</li><li>Absolute Refractive Index Range: 1.2 to 1.8 RIU</li><li>Absolute RI Sensitivity: ±0.002 RIU</li></ul>Fluidics and Flow Properties<ul><li>Band Broadening: &lt;4 µL (at 0.3 mL/min)</li><li>Fill Volume (Inlet Tubing + Flow Cell): 13.7 µL</li><li>Outlet Tubing Volume (0.030” ID): 228 µL</li></ul>Pressure Ratings<ul><li>Inlet Back Pressure (0.5 mL/min H₂O @ 20 °C): &lt;320 psi (22 bar)</li><li>Maximum Permissible Outlet Pressure: 30 psi (2 bar)</li></ul>Temperature Control<ul><li>Control Range: 4 °C to 65 °C</li><li>Stability: ±0.005 °C for precise thermal regulation</li></ul>Optical Source and Safety<ul><li>Light Source: 660 nm wavelength</li><li>Safety Sensors: Integrated vapor and liquid leak detection</li></ul>Electronics and Connectivity<ul><li>Digital Output Rate: 25 Hz</li><li>Analog Output: ±10 V or ±1 V, 18-bit resolution</li><li>Computer Interface: Ethernet for seamless data connectivity</li></ul>Auxiliary I/O Ports<ul><li>Inputs:<ul><li>Analog In (16-bit, ±10 V A/D)</li><li>Zero dRI</li><li>Purge</li><li>Recycle In</li><li>Autoinject In</li><li>Alarm In</li></ul></li><li>Outputs:<ul><li>Autoinject Retransmit</li><li>Alarm Out</li><li>Recycle Out (Orbit™ valve switching)</li></ul></li></ul>User Interface<ul><li>Display: 7” (178 mm) high-resolution multi-touch screen for viewing live signals, diagnostics, and configuring instrument settings</li></ul>Instrument Dimensions<ul><li>Size: 58 cm (L) × 36 cm (W) × 18 cm (H)</li></ul><h4>Other Refractive Index Detectors</h4><ul><li><a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/1268">Optilab™</a> - A unique on-line differential refractometer for measuring concentration of any macromolecule, regardless of chromophores. Temperature controlled from 4 °C to 65 °C. The high-concentration option accommodates protein concentration up to 180 mg/mL.</li></ul>

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Troubleshooting Retention Time Shifts in Liquid Chromatography

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News from LabRulezLCMS Library - Week 18, 2026