The Application Notebook-07-01-2015

Generally speaking, chromate - Cr(VI) - is classified as allergenic, carcinogenic, and extremely toxic and is subject to strict monitoring. Cr(VI) can occur in various concentrations in different areas, for example, drinking water, toys, or textile and leather products. Metrohm has developed ion chromatographic determination methods for determining Cr(VI) in various concentration ranges (ng/L to mg/L) with inline sample preparation techniques for various matrices. The method can be almost entirely automated. In the following application note, we present the analysis of hexavalent chromium in toys, leather, and drinking water.

Rigorous conditioning of sorbent tubes is an essential part of any sampling and analysis protocol. This application note will explore the cost savings and productivity enhancements that can be made by off-line conditioning, rather than on‑line with the thermal desorber itself. In particular, we will focus on the revenue resulting from running more analytical samples, the cost-effectiveness of increasing sample capacity by this approach, and the benefits that stem from using nitrogen rather than helium.

Used extensively from the 1940s through the 1960s, organochlorine pesticides are chlorinated hydrocarbons used in agriculture and mosquito control. The organochlorine pesticides accumulate in the environment, presenting an ongoing issue with adsorption and accumulation in the population as a result of ingestion.

This application note demonstrates the comprehensive 2D-LC analysis of different types of beer. Nontargeted, multisample analysis (fingerprinting analysis) enabled a classification of the different types of beer analyzed.

This application note presents a gradient method using a core–shell column for the determination of various substances in Bourbon vanilla extracts as well as in natural and artificial vanilla flavours. The aim is to compare the ingredients to achieve proof of the authenticity of Bourbon vanilla. By applying the Knauer AZURA Analytical system, a very short analysis time and low eluent consumption could be achieved. The high speed and reliability of the method makes it well-suited for routine analyses in food control.

Aflatoxins (B1, B2, G1, and G2) are naturally occurring mycotoxins produced by fungi on agricultural crops. They are classified as carcinogenic and can pose a significant risk to human health if consumed. Although aflatoxin B1 is the most potent carcinogen, the main concern in milk is its hydroxylated metabolite, aflatoxin M1. To ensure the safety of milk, the US FDA established a tolerance of 0.5 µg/kg for aflatoxin M1 in milk, while the EU set a limit of 0.05 µg/kg in raw milk and 0.025 µg/kg in infant formula. A simple and effective method using polymeric solid-phase extaction (SPE) and liquid chromatography coupled to tandem mass spectrometry (LC–MS–MS) is presented for the analysis of aflatoxins in milk at the low concentrations required.

Amino acids are of vital importance for human life. They serve as transport or storage media for metabolic pathways. Amino acids are components of protein-containing foods such as milk and milk products. Eight amino acids are thought to be essential for humans, meaning that they must be absorbed from foods containing animal proteins or a suitable combination of plant proteins, because the human body can’t synthesize them. Determination of the composition and content of amino acids in milk products is therefore an important measure in ensuring quality and nutritional value.

Membrane proteins - together with lipids - make up biological membranes that are essential for life. In order to understand the role of membrane proteins in assisting membranes to carry out many different functions, it is of great importance to understand the structure of those proteins.

Glycosylation is one of the most common forms of post-translational modification of proteins. The polysaccharide side chains (glycans) play critical roles in physiological and pathological reactions. Besides the interest in characterizing glycosylation pattern of proteins for structure/function analysis, the thorough characterization of glycosylation is also a major quality parameter in the production of biotherapeutics. Hydrophilic interaction liquid chromatography (HILIC) is a well-recognized technique that effectively separates and quantifies isolated glycans.

Heparin is a polydisperse, heterogeneous polysaccharide derived from animal tissue. Heparin has been used as an anticoagulant for over 60 years and one of the fundamental parameters for characterizing unfractionated heparin (UFH) is its molecular weight (MW) and MW distribution. The molecular weight of heparin ranges from 3 to 50 kDa, but, typically falls within the 10 to 20 kDa range for unfractionated heparins used in medical applications. In light of heparin contamination issues in 2008, USP has proposed to include heparin molecular weight determination for the stage 3 heparin monograph revisions.