Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to ...

National Chiao Tung University

ent-16beta-Hydroxybeyeran-19-oic acid ( 1) has potential antihypertensive activity. To obtain novel and more-effective compounds, 1 was incubated with Bacillus megaterium ATCC 14 581 and Aspergillus niger CCRC 32 720. The structures of the metabolites were determined by HR-FAB-MS, 1D- and 2D-NMR spectral data, and enzymatic hydrolysis. Bacillus megaterium hydroxylated and glucosidated 1 to yield ent-7alpha,16beta-dihydroxybeyeran-19-oic acid ( 2), ent-16beta-hydroxybeyeran-19-oic acid alpha- D-glucopyranosyl ester ( 3), and ent-7alpha,16beta-dihydroxybeyeran-19-oic acid alpha- D-glucopyranosyl ester ( 4). Aspergillus niger hydroxylated 1 to yield ent-1beta,7alpha,16beta-trihydroxybeyeran-19-oic acid ( 5) and ent-1beta,7alpha-dihydroxy-16-oxobeyeran-19-oic acid ( 6). Metabolites 3 - 5 were characterized as new compounds. In addition, 2, 3, 5, and 6 were tested for antihypertensive effects, and we found that 5 and 6 were more potent than the parent compound 1.

Hydroxylation and glucosidation of ent-16beta-Hydroxybeyeran-19-oic acid by Bacillus megaterium and Aspergillus niger.

This paper presents a multi-well membrane fabricated using polydimethylsiloxane (PDMS) as a part of a microarray biochip that allows dividable incubation chambers to be provided on a single chip. The conditions of the forming temperature, time, and mixing proportion of the materials were investigated to obtain optimal physical absorption with the surface of the chip substrate. To verify the properties of the multi-well chip, immunoassays were performed by the alpha-1-fetoprotein (AFP) antigen sandwich experiment. The results showed that the detection limit reached to the concentration of 10 ng/ml AFP antigen, and that the dynamic range was 30-3000 ng/ml. Attaining excellent physical absorption helps in avoiding cross-contamination or interference between different samples on the same biochip. The merits of dividable multi-well chips include promoting effective use of surface and multiple-sample experiments.

Dividable membrane with multi-reaction wells for microarray biochips.

Most protein microarrays based on the theory of immobilized metal affinity chromatography (IMAC) were fabricated using the chelator or compound of mono-metallic ion, such as Ni(2+), to capture the histidine-tagged protein. In this study, a novel protein chip with Ni-Co alloy layer fabricated on the substrate of printed circuit board by electrodeposition was developed. It is an innovative microarray surface with bi-metallic elements, i.e. by means of adding cobalt to enhance the specific binding capability to immobilize functional proteins with His-tag attached. Taguchi method was adopted to determine the optimal electrodeposition condition using L18 orthogonal array. Then, the immunoassay was utilized to investigate the properties of the protein chip, and the signal was detected by confocal scanner. The results show that the alloy coating belongs to codeposition of Ni-Co alloy. Due to the affinity adsorption between intermediate metal and protein, this chip provides specific binding. Compared with Ni-coated chip and nitrocellulose (NC) chip, this Ni-Co alloy chip is a high sensitive protein microarray because of high detected fluorescence intensity with low fluorescent background. The proportion of Ni-Co composition will affect the affinity of electroplated layer with proteins and, consequentially, influence the results of immunoassay. Moreover, the test of long-term sensibility of Ni-Co chip showed that it had better binding capability in the first two weeks for coating buffers of pH 7.4 and pH 9 and the immobilization ability began to decay after the third week. The advantages of this novel protein chip include good performance, high repeatability, and inexpensive.

Protein microarray chip with Ni-Co alloy coated surface.

In protein research, protein microarray facilitates high-throughput study of protein abundance and function. An appropriate microarray surface that can be used to immobilize protein samples is a prerequisite for the investigation of molecular interactions. Ni-Co alloy coated protein microarray chip has been found to adsorb histidine-tagged proteins effectively based on the method of immobilized metal affinity chromatography. Due to the ingredient of bi-metallic elements, different electroplating conditions resulted in distinct binding affinities. Therefore, the influence of Ni-Co material properties on the immobilization of histidine-tagged protein was systematically investigated in this study. In the experiments, the contact angle measurement suggested that no strong relationship can be established between the wettability of chip surface and its corresponding protein immobilization. ESCA test demonstrated that the major ingredients of the Ni-Co alloy coated protein microarray chip were Ni and Co. In addition, the XRD test concluded that a Ni-Co protein chip that consists mostly of hcp lattice has better binding capability. SEM micrographs provide direct image evidence. These material tests summarize that the Ni-Co alloy coated protein microarray chip adsorbs His-tagged proteins through its surface morphology. Therefore, it can provide specific binding due to the affinity adsorption between the intermediate metals and the protein.

Influence of material properties upon immobilization of histidine-tagged protein on Ni-Co coated chip.

Based on the principle of immobilized metal affinity chromatography (IMAC), it has been found that a Ni-Co alloy-coated protein chip is able to immobilize functional proteins with a His-tag attached. In this study, an intelligent computational approach was developed to promote the performance and repeatability of a Ni-Co alloy-coated protein chip. This approach was launched out of L18 experiments. Based on the experimental data, the fabrication process model of a Ni-Co protein chip was established by using an artificial neural network, and then an optimal fabrication condition was obtained using the Taguchi genetic algorithm. The result was validated experimentally and compared with a nitrocellulose chip. Consequentially, experimental outcomes revealed that the Ni-Co alloy-coated chip, fabricated using the proposed approach, had the best performance and repeatability compared with the Ni-Co chips of an L18 orthogonal array design and the nitrocellulose chip. Moreover, the low fluorescent background of the chip surface gives a more precise fluorescent detection. Based on a small quantity of experiments, this proposed intelligent computation approach can significantly reduce the experimental cost and improve the product's quality.

Intelligent Computation for Optimal Fabrication Condition of a Protein Chip with Ni-Co Alloy-Coated Surface.

Extraction of volatile and semivolatile compounds from liquid matrixes with high yields, and transferring the extracts to detectors in real time, is challenging. Common extraction procedures involve heating the samples to release the analytes to the gas phase and, in some cases, trapping the gas-phase analytes into sorbents or containers. Here, we propose a new method for fast extraction of volatile and semivolatile compounds from liquid matrixes. This method involves dissolution of a carrier gas in the liquid sample by applying a moderate overpressure (∼150 kPa) and stirring the sample. An abrupt decompression of the extraction chamber leads to effervescence. In this step, many bubbles are instantly formed in the sample matrix. The dissolved carrier gas as well as dissolved volatiles are liberated into the headspace of the extraction chamber within a short period of time (few seconds). The gaseous effluent of the extraction chamber is immediately transferred to the online detector; in this case, an atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The fast release of the gas-phase extract gives rise to a high signal recorded by the detector; several times higher than the signal recorded during direct infusion of headspace vapors without fizzy extraction. This feature provides the means to detect and quantify analytes present in solutions in a short period of time. Here we show that fizzy extraction is suitable for analysis of volatile/semivolatile compounds present in various samples, including those containing complex matrixes.

Cheng-Hao Chang

Department of Applied Chemistry

National Chiao Tung University

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Cheng-Hao Chang

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Applied Chemistry

National Chiao Tung University

Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry

Department of Applied Chemistry