Sigma-Aldrich applications

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.

The radiello ammonia sampler impregnated with phosphoric acid represents a low-cost, reliable and simple tool for assessing the atmospheric deposition of ammonia at parts per billion (ppb) concentration levels.

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.

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.

The Adsorbent Tube Injector System (ATIS) was developed at Supelco® by R&D Scientists, as a tool to assist in our comprehensive adsorbent research for thermal desorption tubes. The ATIS provides an efficient means of transferring calibration standards in either the gas or liquid phase onto the adsorbent packed tubes. The ATIS employs the technique of flash vaporization to vaporize the sample in a continuous flow of inert gas; the inert gas carries the sample to the tube. The sample pathway of the ATIS is constructed of glass and stainless steel. The calibration standard is injected by a syringe through a replaceable septum in the center of the injection glassware, which is heated. After enough time has elapsed, typically less than five minutes, the tube is removed from the ATIS and analyzed using the appropriate analytical technique for that adsorbent tube.

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.

Herbicides are used throughout the world to combat the growth of unwanted plant life. These polar compounds are hydrophilic, so they may find their way into drinking water sources. While gas chromatography has historically been the preferred technique for analysis of herbicides in water samples, the use of LC-MS/MS for this application is gaining acceptance. This is due to the power of MS/MS to provide detailed identification of multiple analytes, but also in part due to the variety of HPLC stationary phases that are available. In particular, several HPLC phases are available that provide great retention and peak shapes for polar analytes, such as herbicides, even under mostly aqueous mobile phase conditions. The combination of these factors may possibly eliminate need for time-consuming sample preparation.