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Abstract

In order to improve the thermal performance of heat exchangers and air collectors, we insert various forms of artificial roughness, known as ribs, into the useful duct. These ribs promote the creation of turbulent flows and enhance heat transfer by conduction, convection and radiation.

However, the introduction of these ribs leads to an increase in pressure drop, requiring higher mechanical power to pump the heat transfer fluid. This experimental study focuses on estimating, using empirical approaches, the pressure losses induced by rectangular ribs with an inclined top. The ribs are made from 0.4 mm galvanized sheet steel.

An experimental set-up was designed to measure the head losses generated by the ribs, from the point of entry to the point of exit from the useful duct. Using the dimensional analysis method, correlations were established to evaluate head losses as a function of flow regime and rib geometry and configuration (including different geometries for rib arrangement over the configuration area).

Open access
Acta Chromatographica
Authors:
Fan Chen
,
Ziyue Wang
,
Xiaoyun Xia
,
Wanhang Wang
,
Yizhe Ma
,
Xiuwei Shen
,
Xuzhao Zhou
, and
Congcong Wen

Abstract

An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of monocrotaline and usaramine in rat plasma, to study the plasma drug concentration and pharmacokinetics, and to calculate the absolute bioavailability. The plasma was treated with acetonitrile and methanol (9:1, v/v) protein precipitation method. The chromatographic column was UPLC HSS T3 (50 mm × 2.1 mm, 1.7 μm), the mobile phase was methanol-water (containing 0.1% formic acid with 10 mM ammonium acetate in water), and the elution time was 4 min at a flow rate of 0.4 mL min−1. Electrospray ionization (ESI) positive ion mode was used for detection and multiple reaction monitoring (MRM) mode was used for quantitative analysis. Monocrotaline and usaramine were administered sublingual intravenously (iv) 1 mg kg−1 and orally (po) 5 mg kg−1, respectively, with 6 rats in each group, for a total of 24 rats. Then the pharmacokinetic differences in rats were evaluated. For the UPLC-MS/MS method, the calibration curve showed good linearity in the range of 2–2,000 ng mL−1, where r was greater than 0.99. The precision, accuracy, recovery, matrix effect and stability results were all consistent with the requirements of biological sample detection methods. to provide scientific experimental basis for the basic research The bioavailability of monocrotaline and usaramine in rat plasma was calculated, which was 43.5 and 19.5%, respectively.

Open access

Abstract

Silica, as a stationary phase, has low separation efficiency accompanied by overlapping, broadened, and tailed peaks, so it needs to be modified to improve its efficiency. This study aims to develop a silica-based stationary phase modified by tetraethylene glycol (TEG) to separate phenolic compounds. Silica was modified by a chemical bond between silanol groups on the silica surface and TEG through a 3-glycidyloxypropylmethoxysilane reaction. The modified silica was packed into a capillary column and used to separate simple phenolic compounds consisting of phenol, pyrocatechol, and pyrogallol. A sample of 0.2 µL was injected into the capillary liquid chromatography and the mobile phase employed was acetonitrile 98% with a flow rate of 3 μL min−1. Elution was also done isocratically in this process and detection was carried out at a wavelength of 254 nm. The mixture of simple phenolic compounds was successfully separated in less than 7 min. The asymmetry factor and resolution were 1.43–2.12 and 1.72–5.43 respectively. The number of the theoretical plates ranged from 213 to 7,857. Columns containing Si-TEG stationary phase also separate phenolic compounds, which consist of gallic acid, syringic acid, ferulic acid, and caffeic acid. A sample of 0.2 µL was injected into the capillary liquid chromatography and successfully separated the mixture in less than 12 min. The samples were eluted isocratically using a mixture of methanol and 50 mM phosphate buffer pH 2.5 (8:92) with a flow rate of 3 μL min−1. The phenolic acids compounds were detected at a wavelength of 280 nm. The chromatogram showed four separate peaks. The asymmetry factor and resolution were 1.53–1.63 and 1.14–1.74, respectively, but the number of the theoretical plates was low, ranging from 190 to 796.

Open access

Abstract

Pinus merkusii Jungh & De Vries. has become increasingly gathered more attention from researchers because the plant has a range of folk medicinal uses. Heartwood plant is the major source of dehydroabietic acid (DHAA) and abietic acid (AA), which possesses several medicinal properties, such as antiviral, antimicrobial, antiobesity and anti-inflammatory. The research proposed herein a low-cost, fast, specific, uncomplicated, sensitive, precise reverse-phase high-performance liquid chromatography (RP-HPLC). This method was conducted and validated for evaluating an amount of DHAA and AA in ethanol extract and oral spray containing P. merkusii heartwood extract. Additionally, stability and antimicrobial activities against clinically isolated Streptococcus mutans of the oral spray were determined. The separation was achieved on Pursuit 200Å PFP column, 150 × 4.6 mm, particles of 3 µm with a flow rate of 1.0 mL min−1. Methanol and water (70:30 v/v) were used as eluent with an isocratic mode and sample analysis volume was set at 10 µL, at a detection wavelength of 210 and 245 nm. The developed HPLC method for analysis of DHAA and AA showed good linearity with correlation coefficients equal to 1. Moreover, other validation parameters, comprised of accuracy, precision, specificity and detection and quantitation limits of this method displayed excellent reliability, validity and sensitivity. This method could be an interesting alternative for quantitative measurement of P. merkusii heartwood extract, oral spray formulation and other P. merkusii heartwood extract preparations. The result from antibacterial tests suggested that the oral spray containing P. merkusii heartwood extract is able to inhibit the oral pathogens causing dental caries. The oral spray decreased S. mutans population size by about 0.5–2 Log CFU mL−1 at 1–4 h and complete elimination of all bacteria strains within 24 h. This study provides validity for using P. merkusii heartwood extract as an alternative for preventing and treating oral infectious diseases.

Open access

Abstract

In this study, we compile the findings to date on using several cellulose-based materials as adsorbents of potentially toxic elements (PTEs) from wastewater. Furthermore, this review discussed the destiny of PTEs-loaded cellulose-based adsorbents and some sustainable methods for their management, hoping to close the pollution loop.

Open access

Abstract

Mirtazapine is an antidepressant medication used to treat the major depressive disorder in adults. In this study, two different chromatographic methods were developed for the determination of mirtazapine in pharmaceutical products. In the first method, An Extend C18 column (250 × 4.6 mm, 5 μm) was used and the temperature was kept constant at 25 °C. The mobile phase was determined as 0.1% formic acid solution and acetonitrile (80/20, v/v), and isocratic elution was applied. The flow rate of the mobile phase was determined as 1.0 mL min−1 and the injection volume was 20 µL. Detection was performed at 291 nm. using a UV detector. In the second method, ethanol was used as the organic modifier. The only difference between these methods was the organic modifier. All other conditions of the methods were the same. Both chromatographic methods were validated by ICH guidelines for various parameters such as selectivity, linearity, accuracy, precision, detection and quantification limit, and robustness. The determination coefficients of chromatographic methods were greater than 0.999 in the concentration range of 5–30 µg mL−1. of mirtazapine. Later, these chromatographic methods were applied to pharmaceutical formulations. Comparison of the obtained results in terms of means was made using Student's (t) test, and comparisons in terms of standard deviations were made using the Fischer (F) test. It was observed that there was no significant difference between these methods. These two methods were then evaluated using the AGREE-Analytical GREEnness metric software. The chromatographic method using ethanol as an organic modifier has been proposed as an excellent eco-friendly and analyst-friendly alternative for the determination of mirtazapine in pharmaceutical formulations.

Open access

Abstract

It still remains a great challenge to selectively enrich and sensitively quantify the trace volatile organic compounds (VOCs) in real samples with complex matrix. In this study, an integration method combining a selective enrichment medium of reduced graphene oxide (rGO) with a specially designed micro thermal-assisted purge-and-trap sampling device was developed for efficient enrichment and sensitive quantification of trace tobacco VOCs coupling with thermal desorption (TD)-gas chromatography/mass spectrometry (GC/MS). The prepared rGO has been proved to possess excellent enrichment selectivity and capacity for tobacco polar VOCs with the multi-layer structure, good thermal stability and large specific surface area. The specially designed sampling device was efficient and suitable for enriching and sampling trace polar tobacco VOCs coupling with rGO medium. Under the optimized sampling and analytical conditions, the established analytical method could be actually applied for quantification of typical tobacco polar VOCs with the good recoveries of 72.9–128% and the satisfied RSDs of 1.8–19.9% (n = 3). The results suggested that the developed method was selective, sensitive and reliable for enrichment and quantification of trace tobacco polar VOCs.

Open access

Abstract

A highly accurate and precise method for the simultaneous detection of 18 neonicotinoids and their metabolites in meat was developed using liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). To improve the pretreatment step of the method, five different commercially available clean-up materials (including C18+PSA (primary secondary amine), Z-Sep (with Discover DSC-C18), EMR-Lipid, SHIMSEN QuEChERS, and Clean-up LPAS) were studied in the treatment of three meat matrices: pork, duck and yellow croaker. Based on the recovery data, we found that among the five purification materials, SHIMSEN QuEChERS was slightly more effective than the others for 18 neonicotinoids. Therefore, SHIMSEN QuEChERS was used as the purification sorbent, and the extraction solvents, extraction methods and chromatographic and mass spectrometric conditions were optimized. A matrix-matched calibration method was applied for quantification. In three different meat matrixes (pork, duck, and yellow croaker), all the target compounds showed good linearity, both with values of r 2 > 0.995. The average recovery of all neonicotinoids ranges from 63.4 to 114.2% (pork), 63.0–113.2% (duck), and 63.9–110.5% (yellow croaker). Relative standard deviations were all <15% for intraday and interday precision. The values of limit of detection (LOD) and limit of quantification (LOQ) were, respectively, ranging from 0.04 to 1.0 μg kg−1 and 0.10 to 2.0 μg kg−1. Compared with previous reports, this method has advantage in LOQs, indicating that it it may be a preferred choice for the detection of neonicotinoid pesticides in meat samples.

Open access

Abstract

In our study, using a combination of eye-tracking parameter analysis and the van Westendorp method, we investigate whether participants pay more attention to products that they perceive as more expensive or to those that they prefer in the ranking process. The experiment involved 50 participants, a questionnaire with ranking and pricing tasks, and an eye-tracking measurement. Three wine varieties (Irsai Olivér, Rosé and Merlot-Shiraz) and three different label alternatives were tested. When comparing the results of the ranking and the pricing tasks, the product that is considered more expensive is not always the one that is most appealing to the participants. If we compare the results from the analysis of the eye-tracking parameters and the pricing, we can say that in all cases the labels that received the most visual attention were those that were priced more expensively by the participants.

Open access

Abstract

An ultra-rapid analytical method for determination of andrographolide and dehydroandrographolide in Andrographis Herba (AH) was developed by liquid chromatography with mass spectrometry (LC-MS). The sample was ultrasonically extracted with 10 mL 40% (v/v) methanol, and then purified with a C18 solid phase extraction column. The LC separation was performed on a Poroshell 120 EC-C18 column (30 × 2.1 mm, 2.7 μm) and eluted with 0.5 mmol L−1 ammonium acetate aqueous solution and acetonitrile (65:35) at a flow rate of 0.7 mL min−1, and detected by mass spectrometry (MS). The LC-MS analytical time was less than 1 min. The new developed method presented a good linearity (r > 0.9900), precision and repeatability (RSD < 2.0%). The recoveries for andrographolide and dehydroandrographolide were 93.5% (RSD = 2.2%) and 97.7% (RSD = 2.4%), respectively. The developed method was successfully applied in determination of andrographolide and dehydroandrographolide in seven batches of AH samples, and the contents of analytes in all samples were complied with the relative acceptance criteria in Chinese Pharmacopeia (>0.8%). This new developed LC-MS method is an ultra-rapid assay method for AH, which will help to improve the efficiency and reduce the cost of AH sample test.

Open access