Victoria Noad | Bournemouth University (original) (raw)

Papers by Victoria Noad

The headspace of common dairy products, including cheese and milk, was analyzed utilizing a new s... more The headspace of common dairy products, including cheese and milk, was analyzed utilizing a new sample preparation technique called Vacuum Assisted Sorbent Extraction (VASE). VASE improves the recovery of heavier and more polar volatile compounds in nearly any matrix by GCMS. After introducing a sample into a 20-40mL vial, a cartridge containing 70mg of Tenax is placed into the headspace of the vial using a vacuum tight interface that allows the vial headspace to be evacuated to less than 0.01atm, or at least until the pressure needed to boil an aqueous mixture at 25°C is reached. This results in faster diffusion from the sample/ headspace boundary layer to the adsorbent, enhancing the rate of sample extraction. In particular, heavy volatile compounds with low vapor pressures that have little to no response by classical SPME are extracted 10-50x more efficiently. Unlike Dynamic Headspace, which uses an inert gas to sweep the volatiles of a sample through the adsorbent bed to concentrate and trap analytes, VASE is performed statically. VASE allows the sample and headspace to come to an equilibrium in a closed system, causing analytes to diffuse onto and collect at the very front of the adsorbent bed. Consequently, VASE achieves a much better recovery of heavier compounds while reducing the common carryover issues affecting other adsorbent techniques that use flow to push compounds far up into a trap. Once placed under vacuum, the analyst determines the length of extraction time, ranging from minutes to hours, until equilibrium between the sample and headspace is reached to produce complete, reproducible extractions. Dairy products generally have low levels of headspace volatiles. In this study, VASE proceeded for 4-24 hours, with many Sorbent Pens extracting samples simultaneously to simulate conditions of a production laboratory. The increase in sample extraction duration combined with a large phase to sample ratio allows more accurate determination of headspace composition, with reduced matrix affects. Data is presented showing milk and cheese analysis, with recovery of compounds well into the semi-volatiles range.

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A new technique for analyzing the overall full range of volatile to semi-volatile organic compoun... more A new technique for analyzing the overall full range of volatile to semi-volatile organic compounds in high alcohol containing beverages using Vacuum Assisted Sorbent Extraction (VASE) in headspace paired with GCMS analysis is presented.

A cartridge containing approximately 70mg of Tenax is placed into a sample vial containing either neat or diluted sample containing a high amount of alcohol. A vacuum tight interface allows the vial headspace to be evacuated to less than 0.01 atmospheres, or at least to the point where an aqueous mixture starts to boil at 25°C. The vacuum is only applied for the time it takes to evacuate the vial, about 15-30 seconds depending on vial size. The vial remains under vacuum after removal of the vacuum source, creating a closed system where faster diffusion from the sample/headspace boundary layer to the adsorbent enhances rates of extraction for both low and higher volatility compounds.

Heavy volatile compounds with low vapor pressures which have little to no response by classical SPME are extracted 10-50x more efficiently. Unlike dynamic headspace, which uses an inert gas to sweep the volatiles of a sample through the adsorbent bed to concentrate and trap analytes, VASE is performed statically. VASE allows the sample and headspace to come to an equilibrium in a closed system, causing analytes to diffuse onto and collect at the very front of the adsorbent bed. Therefore, VASE achieves a much better recovery of heavier compounds while eliminating the common carryover issues.

Once placed under vacuum, the extraction time ranges from minutes to hours until equilibrium between the sample and headspace is reached to produce complete, reproducible extractions. This helps to prevent changes in extraction efficiency when small differences in the sample matrix occur. Additionally, using a packed adsorbent trap for VASE has the advantage of providing 100x more capacity than a GC capillary columns, allowing split injections of 50:1 or more to achieve rapid injection rates while still maximizing the amount that can be loaded onto capillary a GCMS systems for maximum sensitivity and optimum detection limits. In the case of alcoholic beverages, an increased phase ratio is extremely important in dealing with the high affinity of most odor and flavor compounds to the high alcohol containing matrix (up to 40% alcohol by volume).

Data is presented showing rum, whiskey, and wine samples analyzed using VASE, with and without the addition of water or a saturated sodium sulfate solution to determine the optimum approach for recovering volatile to semi-volatile compounds in the sample. Calibration curves of trace level contaminants in wine are also presented showing calibrations from 0.1 to 20 ng/L for Trichloroanisoles, Tribromoanisole, Geosmin, and 2-Methylisoborneol, using Geosmin-d3 as the internal standard. Consistent recovery of these compounds in spiked and non-spiked drinking water and wine demonstrated the ability to perform measurements in matrices with varied complexity and affinity for the target analytes. The results show the extensive range of compounds extracted using VASE. This demonstrates its potential as a sensitive and routine method for examining aroma compounds relating to flavor analysis and regulated contaminants such as trichloroanisoles and phthalates in alcoholic beverages.

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The headspace of common dairy products, including cheese and milk, was analyzed utilizing a new s... more The headspace of common dairy products, including cheese and milk, was analyzed utilizing a new sample preparation technique called Vacuum Assisted Sorbent Extraction (VASE). VASE improves the recovery of heavier and more polar volatile compounds in nearly any matrix by GCMS. After introducing a sample into a 20-40mL vial, a cartridge containing 70mg of Tenax is placed into the headspace of the vial using a vacuum tight interface that allows the vial headspace to be evacuated to less than 0.01atm, or at least until the pressure needed to boil an aqueous mixture at 25°C is reached. This results in faster diffusion from the sample/ headspace boundary layer to the adsorbent, enhancing the rate of sample extraction. In particular, heavy volatile compounds with low vapor pressures that have little to no response by classical SPME are extracted 10-50x more efficiently. Unlike Dynamic Headspace, which uses an inert gas to sweep the volatiles of a sample through the adsorbent bed to concentrate and trap analytes, VASE is performed statically. VASE allows the sample and headspace to come to an equilibrium in a closed system, causing analytes to diffuse onto and collect at the very front of the adsorbent bed. Consequently, VASE achieves a much better recovery of heavier compounds while reducing the common carryover issues affecting other adsorbent techniques that use flow to push compounds far up into a trap. Once placed under vacuum, the analyst determines the length of extraction time, ranging from minutes to hours, until equilibrium between the sample and headspace is reached to produce complete, reproducible extractions. Dairy products generally have low levels of headspace volatiles. In this study, VASE proceeded for 4-24 hours, with many Sorbent Pens extracting samples simultaneously to simulate conditions of a production laboratory. The increase in sample extraction duration combined with a large phase to sample ratio allows more accurate determination of headspace composition, with reduced matrix affects. Data is presented showing milk and cheese analysis, with recovery of compounds well into the semi-volatiles range.

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A new technique for analyzing the overall full range of volatile to semi-volatile organic compoun... more A new technique for analyzing the overall full range of volatile to semi-volatile organic compounds in high alcohol containing beverages using Vacuum Assisted Sorbent Extraction (VASE) in headspace paired with GCMS analysis is presented.

A cartridge containing approximately 70mg of Tenax is placed into a sample vial containing either neat or diluted sample containing a high amount of alcohol. A vacuum tight interface allows the vial headspace to be evacuated to less than 0.01 atmospheres, or at least to the point where an aqueous mixture starts to boil at 25°C. The vacuum is only applied for the time it takes to evacuate the vial, about 15-30 seconds depending on vial size. The vial remains under vacuum after removal of the vacuum source, creating a closed system where faster diffusion from the sample/headspace boundary layer to the adsorbent enhances rates of extraction for both low and higher volatility compounds.

Heavy volatile compounds with low vapor pressures which have little to no response by classical SPME are extracted 10-50x more efficiently. Unlike dynamic headspace, which uses an inert gas to sweep the volatiles of a sample through the adsorbent bed to concentrate and trap analytes, VASE is performed statically. VASE allows the sample and headspace to come to an equilibrium in a closed system, causing analytes to diffuse onto and collect at the very front of the adsorbent bed. Therefore, VASE achieves a much better recovery of heavier compounds while eliminating the common carryover issues.

Once placed under vacuum, the extraction time ranges from minutes to hours until equilibrium between the sample and headspace is reached to produce complete, reproducible extractions. This helps to prevent changes in extraction efficiency when small differences in the sample matrix occur. Additionally, using a packed adsorbent trap for VASE has the advantage of providing 100x more capacity than a GC capillary columns, allowing split injections of 50:1 or more to achieve rapid injection rates while still maximizing the amount that can be loaded onto capillary a GCMS systems for maximum sensitivity and optimum detection limits. In the case of alcoholic beverages, an increased phase ratio is extremely important in dealing with the high affinity of most odor and flavor compounds to the high alcohol containing matrix (up to 40% alcohol by volume).

Data is presented showing rum, whiskey, and wine samples analyzed using VASE, with and without the addition of water or a saturated sodium sulfate solution to determine the optimum approach for recovering volatile to semi-volatile compounds in the sample. Calibration curves of trace level contaminants in wine are also presented showing calibrations from 0.1 to 20 ng/L for Trichloroanisoles, Tribromoanisole, Geosmin, and 2-Methylisoborneol, using Geosmin-d3 as the internal standard. Consistent recovery of these compounds in spiked and non-spiked drinking water and wine demonstrated the ability to perform measurements in matrices with varied complexity and affinity for the target analytes. The results show the extensive range of compounds extracted using VASE. This demonstrates its potential as a sensitive and routine method for examining aroma compounds relating to flavor analysis and regulated contaminants such as trichloroanisoles and phthalates in alcoholic beverages.

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