HPLC and GC Articles

Diuretics are prescribed to treat various conditions such as heart, liver, kidney or lung diseases. However, their mode of action has been misused in sport and has led to the International Olympic Committee (IOC) and various horse racing authorities banning their use in competition.

Figure 1
This application note describes the use of EVOLUTE ABN 50 μm (new larger particle size), a water wettable resin-based non-polar SPE sorbent, for the extraction of diuretics from urine. It describes a generic approach to the extraction of diuretics to which additional compounds can be included with minimal method development time. The analyte suite includes thiazides, carbonic anhydrase inhibitors, loop and potassium sparring diuretics with wide ranging pKa and logP values.

Most authorities currently agree that saturated fatty acids are undesirable in one's diet and that hydrogenated fats can also be unhealthy. Whereas, some unsaturated fatty acids and particularly polyunsaturated fatty acids fall into the "healthy" category. Certain unsaturated fatty acids, notably the omega-3 and omega-6 fatty acids, have been said to have beneficial effects. It has therefore become increasingly important to develop analytical procedures that can unambiguously differentiate the various geometric and positional forms of dietary fatty acids. However, trans-unsaturated isomers, like saturated acids, need to be limited in our diet as they are linked to cardiovascular disease. Figure 1 and Tables 1 and 2 describe an analysis for the identification of fatty acids (as their methyl ester derivatives, FAMEs) in a commercially available fish oil/omega-3 and omega-6 dietary supplement using a 60 m HP-88 column.

The flavours of malt whisky result from a complex blend of long chain esters and alcohols, derived from the distillation products and the composition of the wooden barrels in which the finished product is aged. As shown below, the new VF-WAXms column from Varian, Inc. is ideal for analysing whisky, especially when trace analysis is needed. The column's ultra-low bleed increases sensitivity, extends column life and improves accuracy, even at higher temperatures. In addition, VF-WAXms columns are suitable for use with MS detectors, as the ultra low bleed eliminates interferences and permits more sensitive detection.

Calvados is an apple-brandy of Normandy (France). Mashed apples are fermented to obtain cider and then distilled to give the young spirit.

Spirit aromas are a subtle balance of various volatile compounds belonging to different chemical classes, having different chemical functionalities and consequently various polarities. They may be acetals, aldehydes, alcohols, carboxylic acids, ketones and phenolic derivatives. In Calvados, esters with fruity descriptors are believed to improve the quality, while carboxylic acids with "rancid, sweat" notes are supposed to decrease the quality.

The aromatic composition can be determined using two techniques, gas chromatography coupled to mass spectrometry (GC–MS) to determine the volatile composition and gas chromatography coupled to olfactometry (GC–O) to determine the corresponding odours.

Traditional HPLC methods use the so-called "analytical" columns, commonly 4.6 × 150 mm packed with 5 μm stationary phase, and run at 1.0–2.0 mL/min. New rapid separation LC (RSLC) columns yield equivalent performance in a shorter run time and consume less solvent, with existing instrumentation. Adapting a method to use 3 μm, 3.0 × 75 mm or shorter columns requires only the use of well-known geometric scaling rules, but the calculations are tedious and error-prone. We present a demonstration of the simplified process for adaptation of methods to RSLC.

Turmeric Analysis

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In the following example, the pigments in turmeric were separated on Acclaim PolarAdvantage II columns using conditions as described below. The samples were prepared by extracting turmeric with 40:60:1 ethanol:water:phosphoric acid at 50 °C, filtering and diluting in 1:1 methanol:water.

The continual increase in sample numbers in busy labs means that it is often difficult for quality control or contract analysis labs to maintain short turnaround times, particularly when instruments are already running at full capacity. To address the need for faster analysis while retaining the quality of separation offered by dedicated amino acid analysers, an improved formulation of sodium citrate based buffers has been developed by Biochrom.

Instrumentation

The Biochrom 30 amino acid analyser is a compact bench top, PC-controlled liquid chromatography system for the specific analysis of amino acids for the pharmaceutical, proteomics, food and feedstuffs industries.

Interest in biodiesel as a clean-burning alternative fuel produced from renewable sources such as vegetable oils has increased tremendously over the last few years, mainly because of its reduced environmental impact in comparison with conventional petro-diesel. Biodiesel can be used as a pure fuel or blended at any level with petroleum diesel. For biodiesel to be commercialized as pure biofuel or blending stock for heating and diesel fuels, it must meet a set of requirements as defined in ASTM D6751 and EN 14214 standards. These standards indicate maximum allowable concentrations of contaminants in B100 finished product, along with other chemical-physical properties necessary for safe and satisfactory engine operation.1

Pesticides are used throughout the world to control pests that are harmful to crops, animals, or people. Because of the danger of pesticides to human health and the environment, regulatory agencies control their use and set pesticide residue tolerance levels. The limits of detection (LODs) for many of these substances are at the parts-per-trillion (ppt) level. To achieve this level of detection, off-line sample pre-concentration is often performed. However, these sample preparation procedures can be time consuming, adding as much as one to two days to the total analysis time. Therefore, a method for on-line sample pre-concentration that bypasses the off-line sample pre-concentration provides a significant time savings over conventional methods.

Contamination of public buildings with PCBs used as softeners in the 1970's in sealants and wall and ceiling paints can still be detected. If certain threshold values in indoor air are exceeded the source has to be decontaminated. This requires an effective and fast determination of the PCB concentration in indoor air. Thermodesorption GC–MS is a method especially suitable for this purpose. Polychlorinated Biphenyls (PCBs) are highly toxic and carcinogenic chemical substances. Although first prepared in 1864, they have been industrially manufactured since 1929. The highest production amounts worldwide were recorded in the 1960s and the beginning of the 1970s. In the 1970s their use as additives for building materials was widespread because of their flame inhibiting and noise reduction properties.

Pesticides are widely used by farmers to control pests, weeds and molds that would otherwise decrease crop production. While this has significantly increased worldwide food productions, these same pesticides pose health risks to humans. The restrictions for specific pesticides differ from one country to the next and as world trade increases, the potential threat to other countries' populations increases. For this reason, pesticides and other food related allergens are currently the subjects of increasing scrutiny and regulation.

There are more than 500 different pesticides used throughout the world, so it is very difficult to tell what pesticide a food product might have been treated with. To ensure consumer safety, multi-residue screening approaches are being developed to analyse as many pesticides as possible.