Showing 1 - 10 of 103 results

Volatile Profiling in Red Wine using ChromSync [AN0032]

With a wide variety of wines available and the consumer market so large, it is vital that wineries test and monitor the volatile compounds, that contribute to the flavour profile, during the production process to ensure that the same flavours are consistently achieved. The volatile compounds that make up the flavour composition must therefore be profiled batch to batch. Strict controls are operated during the production of wine as varying levels of volatiles can vastly affect the flavour of the final product.
Gas chromatography (GC) is often the instrumentation of choice for the analysis of flavour active volatiles in wine. Compass Chromatography Data System (CDS) is a state of the art chromatography software platform that controls GC instruments whilst offering automated processing and reporting of results. ChromSync is an application add on specifically for the flavour and fragrance industry. Chromsync has the ability to determine the ‘fingerprint’ of volatile compounds in wine. The individual ‘fingerprints’ are then compared with a reference standard. ChromSync rapidly compares peak retention time as well as area% profiles of complex chromatograms, making processing volatile flavour profiles effortless. Additionally, ChromSync instantly confirms product batch to batch reproducibility whilst reporting any missing compounds and calculating the degrees of similarity. This application note demonstrated the ease of using ChromSync with CompassCDS for the comparison of six Shiraz red wine samples analysed via headspace (HS) gas chromatography (GC) with flame ionisation detection (FID) and mass spectrometry (MS) for identification of volatile compounds. All samples were made from the same shiraz grape in order to identify both similar and varied volatilesin the wine.

US EPA Method TO-15 Volatile Organic Compounds in Ambient Air_2019.1 [AN023]

INTRODUCTION: Many volatile organic compounds (VOCs) that occur in ambient air are the result of emissions from mobile, industrial sources, landfills and hazardous waste sites. The levels of these compounds in air frequently regulated by national or local government agencies. Additionally, it is vital to monitor the VOCs to determine the effect they have on human health, the environment and the global climate. Detection of toxic organic compounds in ambient air
is undoubtedly one of the most difficult analyses in gas chromatography, due to the trace levels needed to be quantified and due to the large number of
target compounds. Samples must be concentrated into a small volume in order to enhance detection limits.

Transformer Oil Gas Analysis via Headspace Sampling (ASTM D3612) [AN0030]

Insulating fluids, generally mineral oils, are used in transformers. Under normal, mild conditions, there is very little decomposition. However, occasionally localised or general heating of the oil occurs and decomposition products are formed. If the concentration of these gases reach a critical point, the chances of catastrophic transformer failure are high. ASTM D3612 describes in detail three different routes for transformer gas analysis. During Vacuum Extraction gases are extracted from the oil via a vacuum extraction device and analysed using gas chromatography (GC). Stripper Column Extraction details the extraction of dissolved gases from a sample of oil by sparging the oil with the carrier gas, onto a stripper column containing a high surface area bead. The gases are then flushed from the stripper column into a GC for analysis. The final method is Headspace Sampling in which an oil sample is brought into contact with the headspace in a closed vessel sparged with argon. As a result, a portion of gas dissolved in the oil is transferred to the headspace. This application note describes the final method; Headspace Sampling.

Transformer Oil Gas Analysis using a Stripper Column (ASTM D3612) [AN0031]

Insulating fluids, generally mineral oils, are used in transformers. Under normal, mild conditions, there is very little decomposition. However, occasionally localised or general heating of the oil occurs and decomposition products are formed. If the concentration of these gases reach a critical point, the chances of catastrophic transformer failure are high. ASTM D3612 describes in detail three different routes for transformer gas analysis. During Vacuum Extraction gases are extracted from the oil via a vacuum extraction device and analysed using gas chromatography (GC). Stripper Column Extraction details the extraction of dissolved gases from a sample of oil by sparging the oil with the carrier gas, onto a stripper column containing a high surface area bead. The gases are then flushed from the stripper column into a GC for analysis. The final method is Headspace Sampling in which an oil sample is brought into contact with the headspace in a closed vessel sparged with argon. As a result, a portion of gas dissolved in the oil is transferred to the headspace. This application note describes the second method; Stripper Column analysis.

Trace Impurities in Mixed Xylenes by GC UOP Method 931-10

This method is for determining trace impurities in high-purity mixed xylenes by gas chromatography (GC). Specific trace impurities determined include non-aromatic hydrocarbons, benzene, toluene and individual C9 and C10 aromatic compounds. C10 or higher non-aromatics, if present, may interfere with the determination of benzene. These can be determined by UOP Method 543. The lower limit of quantitation for any single component is 1 mg/kg (mass-ppm). Impurities at concentrations above 500 mg/kg should be determined by UOP Method 744.

The sample is injected into a gas chromatograph that is equipped with an autoinjector, SSL injector, fused silica capillary column internally coated with poly(ethylene glycol), and a flame ionization detector.

The concentrations of individual or group impurities are determined by the external standard (ESTD) method of quantitation, wherein peak areas of the sample components are compared to the peak areas of a calibration blend analyzed under identical conditions and injection volumes.

Trace Carbonyl Sulphide and Phosphine in Ethylene or Propylene, May 2019.1 [AN011]

INTRODUCTION: Organic Sulphur and phosphorus occur naturally in crude oil. Ethylene and propylene are formed from the crude oil during the refining process. As these products are purified trace amounts of sulphur or phosphorus may be carried through the process. During polymerization of these compounds to form polyethylene or propylene, trace sulphur or phosphorus components must be accounted for and kept to a minimum. Any contamination from these components can poison polymer catalysts and adversely affect the quality of the product polymer. Contaminants routinely monitors by the plastics industry include Carbonyl Sulphide (COS) and Phosphine (PH3).

The Use of Alternative Carrier Gases in Gas Chromatography [AN0029]

Helium is one of the most common and lightest elements in the universe. The boiling point of helium is closer to absolute zero than any other element. When using helium consideration is rarely given to the fact that it is a non reusable element, meaning the world’s resources of helium are being depleted. Due to the limited availability and the increased sales prices of helium, alternative for helium must be implemented. The importance of carrier gas selection has been a discussion point amongst users of gas chromatography for many years. To serve as a carrier gas in gas chromatography, the gases must be available in sufficient purity and inertness. There are three gases that are commonly used as a carrier gas: nitrogen, helium and hydrogen. The efficiency comparison between these gases is given by the Van Deemter curve which relates the efficiency with carrier gas velocity through the column (speed). Figure 1 shows the Van Deemter curve for nitrogen, helium and hydrogen.
The most efficient gas is hydrogen, followed by helium and nitrogen. Even though the optimum plate height for the three gases are almost identical, helium and nitrogen are behind with respect to analysis time. When viewing the Van Deemter curve, nitrogen has a narrow optimum, with both helium and hydrogen having wider optimums, meaning they may be used at higher velocities with only little sacrifice in separation efficiency. Hydrogen is considered the optimal choice, combining high efficiency separations with short analysis times. However, hydrogen has a safety risk with a 4% concentration in air will lead to explosions.
To date, the worldwide carrier gas of choice has been the second most efficient gas; helium. However, with the rising cost and apparent shortage, the use of alternative carrier gases has increased over time.

Showing 1 - 10 of 103 results