HPLC Applications

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  • Category: Monitoring & Testing ×

  • Subcategory: HPLC ×

Rapid Determination of Pesticides in Spinach

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

Highly pigmented foods, such as spinach, require cleanup prior to analysis for pesticide residues. A dual-layer SPE tube containing graphitized carbon and aminopropyl on silica (NH2) is often used because; Carbon removes pigments and sterols and NH2 removes fatty acids, polar pigments, organic acids, and sugars. Removing these matrix materials reduces interferences that can lead to ion suppression in LC-MS, inlet contamination in GC-MS, and column contamination for both techniques. Our Supel Sphere Carbon/NH2 SPE tube uses spherical materials for both the carbon and NH2 layers, providing fast, more consistent flows compared to tubes containing granular material. This allows gravity elution (instead of vacuum elution) to be applied to Supel Sphere tubes, resulting in more contact time between extracts and sorbents.

Increased Pigment Removal with Analysis of Pesticides in Oranges

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

An application was developed to demonstrate increased pigment removal for the analysis of pesticides, using Supel™ QuE Z-Sep/C18 QuEChERS and an Ascentis® Express C18 HPLC Column. The improved cleanup can decrease column and instrument fouling, leading to extended LC column lifetime and reduced instrument downtime.

Reproducible Recoveries of Pesticides from Fruits and Vegetables

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

A group of 30 compounds was selected, representing pesticides, acaricides, insecticides, and fungicides. These samples were analyzed using Supel™ QuE QuEChERS and an Ascentis® Express RP-Amide HPLC Column.

Determination of Additives in Beverages using Ascentis Express Columns

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

Beverages, such as sodas and energy drinks, can include a number of polar ingredients, which are easily soluble in the water matrix of the drinks. These ingredients include sweeteners (sugars and sugar substitutes), caffeine, vitamin supplements, amino acids, organic acids, and plant extracts. Because the analytes are already in solution, there is no need for extensive sample preparation. Dilution followed by direct injection into an HPLC is typically suitable. In this article we present two beverage applications using Ascentis Express HPLC columns. Ascentis Express columns offer faster HPLC on any system. One benefit is their ability to produce the resolution, efficiency, and speed on conventional HPLC systems that is associated with the use of sub-2 micron columns on a UHPLC system, without generating high backpressure. Column chemistries (RP-Amide and HILIC) were selected for this article based on their enhanced performance with polar compounds in comparison to C18.

Improved Reproducibility and Reduced Sample Preparation Time for the HPLC Analysis of Aflatoxins in Raw Peanut Paste

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

The US FDA and international regulatory agencies have set contamination levels for aflatoxins in animal feedstuffs. Since Aspergillus may infect commodities pre-harvest, during storage or during processing, monitoring for aflatoxins in associated agricultural commodities at all stages of production is requisite. Field screening methods exist that are adequate to estimate contamination levels for aflatoxins. When additional confirmation or quantification is desired, chromatographic laboratory analysis is often necessary. Preparation of matrix samples prior to chromatographic analysis typically requires extraction and purification. Commonly, immunoaffinity columns (IAC), which employ a multi-step bind and elute mechanism to concentrate and purify aflatoxins, are used to purify matrix samples for subsequent analysis. Solid phase extraction (SPE), an alternate method which may use interference removal, can also be employed.

Formaldehyde and Acetaldehyde Determination in Air Using Fully Automated On-Line Desorption and Analysis of DNPH Cartridges

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

Airborne aldehydes and ketones are collected by passing air through a cartridge containing 2,4-dinitrophenylhydrazine (DNPH). Carbonyl compounds react with the DNPH to form hydrazones, which are immobilized on the cartridge. These compounds can be easily eluted from the cartridge with acetonitrile and analyzed by HPLC with UV detection. Traditionally, this analysis including the workup contains a series of manual steps, which can become time-consuming and could incur experimental error. Automating the extraction of LpDNPH S10 cartridges and putting it in-line with the HPLC analysis will significantly reduce manual labor using this technique and this will improve reproducibility of the method by reducing potential experimental errors by the operator. The automation and unattended operation of the method leads to high throughput for determining airborne formaldehyde and acetaldehyde.

Analysis of Isocyanates Using the ASSET™ EZ4-NCO Dry Sampler

by Sigma-Aldrich Co., LLC     based in Bellefonte, PENNSYLVANIA (USA)

Isocyanates are used as a raw material to produce a number of products . Personal exposure can occur while the products made with isocyanates are being applied, or when the materials are removed by grinding or thermal degradation. Workers who are exposed to these compounds are at risk for respiratory disorders and asthma. The highly reactive nature of the isocyanate compounds and the low occupational exposure limits put high demands on both sampling and analytical techniques for monitoring of isocyanates in air. We investigated the performance of the LC-MS and LC-MS-MS methods in the analysis of isocyanates using the new ASSET™ EZ4-NCO Dry Sampler. We found that the analytical method can successfully reach the quantitation limit for most isocyanates of 5 ng/mL in the final sample when LC-MS-MS analysis was used and the quantitation limit of 10 ng/mL when LC-MS analysis was used. All 11 compounds were well-resolved chromatographically using a 15 cm Ascentis Express C18 column.

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