Optimization of a headspace solid-phase microextraction method for the gas chromatography-mass spectrometry analysis aroma compounds of Litsea mollis Hemsl. immature fruit

HS-BAμE: A New Alternative Approach for VOCs Analysis-Application for Monitoring Biogenic Emissions from Tree Species

In this work, a new analytical approach is proposed for monitoring biogenic volatile organic compounds (BVOCs) by combining headspace bar adsorptive microextraction (HS-BAμE) with gas chromatography-mass spectrometry (GC-MS). The HS-BAμE methodology was developed, optimized, validated and applied for the analysis of BVOCs emitted from two tree species (Eucalyptus globulus Labill. and Pinus pinaster Aiton) and compared with headspace solid phase microextraction (HS-SPME), commonly accepted as a reference technique. To achieve optimum experimental conditions, numerous assays were carried out by both methodologies, studying the release of the five major monoterpenoids (α-pinene, β-pinene, myrcene, limonene and 1,8-cineole) from the leaves of the tree species, whereas the maximum selectivity and efficiency were obtained using an activated carbon and PDMS/DVB fiber as sorbent phases for HS-BAμE and HS-SPME, respectively. Under optimized experimental conditions, both methodologies showed similar profiling and proportional responses, although the latter present a higher sensitivity in the analytical configuration used. For the five monoterpenoids studied, acceptable detection limits (LODs = 5.0 μg L^-1) and suitable linear dynamic ranges (20.0-100.0 mg L^-1; r² ≥ 0.9959) were achieved, and intra- and inter-day studies proved that both methodologies exhibited good results (RSD and %RE ≤ 19.9%), which indicates a good fit for the assessment of BVOCs by the HS-BAμE/GC-MS methodology. Assays performed on sampled leaves by both optimized and validated methodologies showed high levels of the five major BVOCs released from E. globulus Labill. (10.2 ± 1.3 to 7828.0 ± 40.0 μg g^-1) and P. pinaster Aiton (9.2 ± 1.4 to 3503.8 ± 396.3 μg g^-1), which might act as potential fuel during forest fire's propagation, particularly under extreme atmospheric conditions. This is the first time that BAμE technology was applied in the HS sampling mode, and, in addition to other advantages, it has proven to be an effective and promising analytical alternative for monitoring VOCs, given its great simplicity, easy handling and low cost.

A Validated Liquid–Liquid Extraction Method for the Quantitative Analysis of Ethanol in the Different Types of Home-Brewed Alcoholic Beverages of Botswana Using Gas Chromatography Flame Ionization Detector

Purpose

Home-made alcohol-related deaths are a significant public health issue which is often overlooked. To date, approximately 30 people have died following the consumption of home brewed alcoholic beverages in Botswana. The process of brewing such alcoholic beverages remains unmonitored and makes it difficult to pinpoint the cause of these deaths. Ethanol content in these beverages is thought to be high and therefore contributing towards the deaths. The aim of this research was to develop and validate a method for the quantification of ethanol in the different types of home-brewed alcoholic drinks of Botswana.

Methods

Twenty-six different samples of home-brewed alcoholic drinks were collected from local brewers in different districts of Botswana. A Liquid–Liquid Extraction-Gas Chromatography-Flame Ionization Detector method was optimized for extraction of ethanol using ethyl acetate and validated for accuracy, precision, repeatability, selectivity, linearity, limit of detection, limit of quantification, stability. Following this, the method used to measure the concentration of ethanol in the different home brewed beverages.

Results

The method demonstrated linearity in the concentration range of 2.5–60% v/v with correlation coefficient (R²) of 0.996 and, was found to be precise with %RSD values ≤ 5%. Repeatability was acceptable with %RSD values ≤ 5%. Percentage recoveries were within 100%. No interference was observed from likely excipients commonly found in home brewed alcoholic beverages, demonstrating good selectivity. Limits of detection and quantification were found to be 0.37% v/v and 1.12% v/v respectively. The analysed samples were discovered to contain ethanol with concentrations ranging from 2.56 to 36% v/v.

Conclusion

A method for the quantification of ethanol in home-made alcoholic beverages of Botswana was developed and validated. It is simple, cheap, rapid and does not require sophisticated instruments.

Optimization of Ultrasonic Extraction of Triterpenes from Loquat Peel and Pulp and Determination of Antioxidant Activity and Triterpenoid Components

The aim of this paper was to study the optimal extraction process of total triterpenes from loquat peel and pulp assisted by ultrasound. The effects of solid–liquid ratio, ethanol concentration, ultrasonic time, ultrasonic power, and ultrasonic temperature on the yield of triterpenoid acid in loquat were investigated by single-factor and response surface methodology. FRAP (Ferric ion reducing antioxidant power) method, ABTS (2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) method, and DPPH (1,1-Diphenyl-2-picrylhydrazyl) method were used to determine the antioxidant capacity of peel and pulp at different stages. LC-MS (Liquid Chromatograph Mass Spectrometer) was used to qualitatively analyze different tissues of loquat. The optimal extraction conditions were as follows: ethanol concentration 71%, ultrasonic time 45 min, ultrasonic power 160 W, solid–liquid ratio 1:10, and ultrasonic temperature 30 °C. The total triterpenoid content of loquat peel was 13.92 ± 0.20 mg/g. The optimal extraction conditions were ethanol concentration 85%, ultrasonic time 51 min, ultrasonic power 160 W, solid–liquid ratio 1:8, and ultrasonic temperature 43 °C. The total triterpenoid content of loquat pulp was 11.69 ± 0.25 mg/g. The contents of triterpenes and antioxidant capacity in the peel and pulp of loquat at the three stages were the highest in the fruit ripening stage (S3). LC-MS analysis showed that most of the triterpenes belonged to ursolic acid derivatives and oleanolic acid derivatives, which laid the foundation for further utilization and development of loquat peel and pulp.

Optimization of Adsorption and Desorption Time in the Extraction of Volatile Compounds in Brewed Java Arabica Coffee Using the HS-SPME/GC-MS Technique

The headspace solid phase microextraction (HS-SPME) technique has been recognized as a reliable technique for characterizing the aroma profile of Arabica coffee beans. The amount and content of the detected volatile compounds depend on the volatile analyte extraction process with HS-SPME, namely the adsorption and desorption processes. However, the optimal extraction time in applying coffee volatile compounds is still limited. This research aimed to obtain the optimum adsorption and desorption time in analyzing volatile compounds in brewed Java Arabica coffee. The adsorption time was optimized for 20 to 60 minutes with 5 minutes desorption time. The desorption time was optimized from 5 to 45 minutes with a 20 minutes of adsorption time. There are 14 volatile compounds with a peak area percentage of more than 2% from adsorption and desorption optimization. The optimal adsorption time was 50 minutes, where there were 5 of 7 compounds with the most significant area, such as 2-furfural (29%), 2-acetyl furan (3%), 2-furfuryl acetate (6%), 5-methyl furfural (12%), and 2-furfuryl alcohol (14%). Meanwhile, the most optimal desorption time was 5 minutes which detected 12 compounds, while the other desorption time only detected eight compounds. Furfuryl formate (2%), pyridine (12%), and 2-furfuryl alcohol (14%) had a higher peak area than the other compounds at a desorption time of 5 minutes. The results showed the same number of volatile compounds at each adsorption time. In conclusion, the adsorption time did not affect the number of compounds detected as in the optimization of desorption time. Adsorption and desorption time is crucial in analyzing volatile compounds from coffee using the HS-SPME/GC-MS technique.

Characterization of the Key Aroma Compounds in the Fruit of Litsea pungens Hemsl. (LPH) by GC-MS/O, OAV, and Sensory Techniques

The key aroma compounds in the fruit of Litsea pungens Hemsl. (LPH) were concentrated through solvent-assisted flavor evaporation (SAFE) and characterized by gas chromatography-mass spectrometry-olfactometry (GC-MS/O), quantitative descriptive analysis (QDA), odor activity values (OAVs), and addition test. The results showed that LPH contained 31 aroma-active compounds (flavor dilution, FD = 9). Among them, 30 odorants were quantified by the standard curve method. The OAV analysis results showed that 25 odorants had OAVs ≥ 1, which could be considered as the potent odorants. D-Limonene and 3,7-dimethyl-2,6-octadienal had the highest OAVs (OAV = 9803 and 8399), followed by (Z)-3,7-dimethylocta-2,6-dienal (OAV = 1893), β-myrcene (OAV = 1798), (E)-3-phenyl-2-propenoic acid ethyl (OAV = 1603), and β-caryophyllene (OAV = 1129). Addition experiments further confirmed that 3,7-dimethyl-2,6-octadienal, (Z)-3,7-dimethylocta-2,6-dienal, and D-limonene contributed to lemon attribute, β-myrcene contributed to green attribute, citronellal contributed to mint and fresh note, and eucalyptol contributed to eucalyptus-like note were the key odorants.