Mitigating Matrix Effects: Examination of Dilution, QuEChERS, and Calibration Strategies for LC-MS/MS Analysis of Pesticide Residues in Diverse Food Types
25 Apr 2017Liquid chromatography tandem mass spectrometry is popular for monitoring pesticide residues in food. The increased selectivity and sensitivity of LC-MS/MS have impacted how multi-residue methods are performed, sometimes decreasing the need for rigorous sample preparation. However, this approach suffers from matrix effects causing poor data quality and difficult quantification. Matrix effects can be mitigated by sample preparation that reduces the concentration of co-extracted matrix material or by experimental strategies like matrix-matched calibration that compensate for matrix effects. This white paper considered these two aspects of multi-residue methods, sample preparation and calibration strategies, in order to determine recommendations that balanced data quality as well as time and financial investments.
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Ultra Aqueous C18 Columns
Restek Corp.The Ultra line represents Restek’s broadest selection of stationary phases on a single silica support. Made of high-purity, type-B silica that minimizes activity and creates high-density bonding, these columns are designed for selective and reliable HPLC applications.The Ultra Aqueous C18 HPLC column provides reproducible retention times and can be used with highly aqueous mobile phases, which may eliminate the need for sample derivitization or ion pairing reagents. This column features a true C18 alkyl bonded phase, meeting the requirements of a US Pharmacopoeia (USP) L1 stationary phase.The Ultra Aqueous C18 column uses a novel bonding chemistry that results in polar groups at the silica surface. These surface polar groups keep the alkyl stationary phase extended, and thus wetted by the mobile phase—even when using up to 100% aqueous mobile phases.Additionally, although the Ultra Aqueous C18 column behaves similarly to a traditional base-deactivated C18 column when analyzing neutral hydrophobic compounds, it has enhanced retention and unique selectivity for polar and basic compounds.Ultra Aqueous C18 Columns Features: Analyzes polar compounds by reversed phase. Retains compounds such as amino acids and water soluble vitamins using simple mobile phases and without derivitization. Analyzes polar, hydrophillic materials without retention time loss. Stable retention in 100% aqueous mobile phases. Can analyze compounds that are sparingly soluble in organic solvents. True C18 alkyl bonded phase. High-density C18 ligand coverage. Similar selectivity as traditional C18 phases for neutral hydrophobic compounds. Unique secondary polar characteristics. End-capping diminishes peak tailing observed from exposed silanol sites on the silica surface. Column Characteristics: Phase: C18 particle Size: 3, 5 μm Pore Size: 100 Å Length: 30, 50, 100, 150, 200, 250 mm ID: 0.3, 1.0, 2.1, 3.0, 3.2, 4.6 mm
Q-sep™ QuEChERS Tubes
Restek Corp.Q-sep™ QuEChERS Tubes for Pesticide Residue Analysis • Fast, simple sample extraction and cleanup using dSPE. • Fourfold increases in sample throughput. • Fourfold decreases in material cost. • Convenient, ready to use centrifuge tubes with ultra pure, preweighed adsorbent mixes. Quick, Easy, Cheap, Effective, Rugged, and Safe, the QuEChERS ("catchers") method, developed by the USDA Eastern Regional Research Center, has become very popular for extraction and clean-up of pesticide residue samples. Our products are available in three centrifuge tube sizes to meet the needs of both extraction and cleanup of a wide variety of sample matrices following various methods. The researchers developed a simple two-step procedure. First, the homogenized samples are extracted and partitioned, using an organic solvent and salt solution. Then, the supernatant is further extracted and cleaned, using a dispersive SPE technique. Multiple adsorbents are placed in a centrifuge tube, along with the 1mL of organic solvent and the extracted residues partitioned from step 1. The contents are thoroughly mixed, then centrifuged, producing a clean extract ready for a variety of GC or HPLC analytical techniques. Validation and proficiency data for the QuEChERS method are available for a wide variety of pesticides in several common food matrices on their website.
QuEChERS Performance Standards Kit
Restek Corp.Designed for use in all QuEChERS methods for pesticides in fruits and vegetables, including the original unbuffered method, AOAC 2007.1, and EN15662. Kit contains organochlorine, organonitrogen, organophosphorus, and carbamate fungicides and insecticides commonly used on fruits and vegetables. Volatile, polar, active, base-sensitive, and nonvolatile compounds are included to allow comprehensive evaluation of QuEChERS extraction and cleanup efficiencies, and optimization of GC and LC instrumental conditions.QuEChERS Performance Standards Kit Features: Ideal for initial method evaluations and ongoing method performance validations. Analytes are divided into three ampuls based on compatibility for maximum stability and shelf life. Precise formulations improve data quality and operational efficiency; spend more time running samples and less time sourcing and preparing standards. Quantitatively analyzed to confirm the composition and stability of each mixture. Produced and tested in accordance with ISO Guide 34 and 17025 accreditation.