A channel-homogenized micro gas chromatography column for light alkane separation with uniform HKUST-1 stationary phase.

BACKGROUND: The micro gas chromatography column (µGCC) is one of the key components of the miniaturized gas chromatography system. However, light alkanes are difficult to be separated by a micro gas chromatography column, especially for methane and ethane, because the length of µGCC is limited by the area of a silicon substrate. More importantly, the heterogeneous microchannel surface formed by silicon glass bonding causes uneven stationary phase coating and the forces between the untreated microchannel surfaces and the stationary phase materials are weak, which will prevent the improvement of separation performance. RESULTS: In this paper, a micro gas chromatography column (µGCC) with uniform HKUST-1 stationary phase is reported. Significantly, an alumina film prepared by the atomic layer deposition (ALD) technique is used to homogenize the heterogeneous microchannels. The alumina is a hydrophilic material and the alumina made by the ALD technique is uniform. The forces between hydrophilic alumina film and HKUST-1 are strong, which can greatly improve the coating uniformity of the hydrophilic stationary phase HKUST-1. The test results show that the µGCC could baseline separate the light alkane mixtures (CH4, C2H6, C3H8, and C4H10) at the high testing temperature of 120 °C. The maximum resolution of the difficult-separated methane and ethane reached 19.2, which is 108 % higher than the µGCC using the same stationary phase without homogenizing the microchannel inner surface. SIGNIFICANCE: The µGCC uses ALD alumina film to homogenize the microchannel inner surface; meanwhile, hydrophilic ALD alumina has a strong electrostatic attraction with the hydrophilic stationary phase HKUST-1. Homogeneous microchannel surface and strong electrostatic attraction are favorable to obtain uniform stationary phase which greatly improves the separation performance, resulting in a large resolution for methane and ethane. The µGCC has broad application prospects in light alkane separation.

An all-glass based micro gas chromatographic column for light hydrocarbon separation with HKUST-1 as stationary phase.

BACKGROUND: The gas chromatography column is one of the key components of the gas chromatograph and typically be miniaturized using micro-electro-mechanical system (MEMS) technology. Due to the limited area of the Si wafer, the column length of micro gas chromatographic column (µGCC) is usually much smaller than that of commercial chromatographic columns. Therefore, it is always difficult to use µGCCs to separate small molecule gas components such as light hydrocarbons. More importantly, the heterogeneous microchannel surface formed by silicon glass bonding causes uneven stationary phase coating, further preventing the improvement of separation performance. RESULTS: In this paper, a novel all-glass based µGCC with 2 m length for the separation of light hydrocarbons is proposed. The microchannels of the µGCC were directly prepared in the glass substrate by ultrafast laser assisted chemical etching (ULAE). The all-glass microchannels make the coating of the hydrophilic metal-organic frameworks (MOFs) stationary phase continuously because of the homogeneous material composition. Therefore, a widely used copper based hydrophilic MOFs HKUST-1 was used as stationary phase for coating and testing. The test results show that the µGCC which is an open tubular column can realize the baseline separation of light hydrocarbons at 100 °C. And the resolution of difficult separated compounds, methane and ethane, can reach 12.98, which is 201.86 % higher than the silica-based monolithic capillary column in the relevant research. The resolution of ethane and ethylene reaches 6.81 at 120 °C. SIGNIFICANCE: The µGCC fabricated by ULAE method is composed of all-glass and has the uniform stationary phase coating because of the homogeneous microchannel surface which greatly improve the separation performance, resulting in a large resolution for methane and ethane. The all-glass µGCC has broad application prospects in light hydrocarbon separation.

A semi-packed gas chromatographic column with staggered elliptic cylindrical post arrays.

A semi-packed gas chromatographic column has the advantages of high specific surface area and low column pressure. We report that the stagnation regions formed in the adjacent posts along the channel of the semi-packed columns can decrease the area and height of chromatographic peaks, which makes it difficult to detect low-concentration mixed gases. A semi-packed column with staggered elliptic cylindrical post arrays (SC-S) made using a micro-electro-mechanical system technique is presented, and the separation performance of SC-S is compared with that of a semi-packed column with aligned elliptic cylindrical post arrays (SC-A). The simulation results show that the width of stagnation regions in SC-S is 86.89% smaller than that in SC-A. The experimental results indicate that the area and height of chromatographic peaks increased as stagnation regions reduced. In the separation of the alkane mixture from C8 through C10 with 10 ppm concentration, the chromatographic peak of decane was hardly identified in SC-A while the chromatographic peak in SC-S was still clearly visible. The chromatographic peak heights of octane and nonane were increased by 65.06% and 130.00%, respectively, in SC-S. The peak areas of octane and nonane were increased by 120.45% and 168.18%, respectively.

Micro gas chromatographic column with copper benzene-1,3,5-tricarboxylate modified by multilayer fluorinated graphene as a stationary phase.

A composite material was synthesized at room temperature by performing modification of the copper benzene-1,3,5-tricarboxylate (HKUST-1) metal-organic framework material by multilayer fluorinated graphene (FG). The FG-HKUST-1 composite was used as a stationary phase for a micro gas chromatography column (µGCC) fabricated using micro-electro-mechanical system (MEMS) technology. The separation results showed that the µGCC with the FG-HKUST-1 composite stationary phase achieved a baseline separation of C1-C4 in 8 min. The retention factors for C2-C4 were 2.13, 7.14, and 12.04, respectively. The maximum relative standard deviation (RSD) of the retention times was 0.14 %. The difference in the retention time between methane and ethane was 1.11 min, with a resolution of 9.2 for methane and ethane. The retention factor of ethane and the resolution of methane and ethane were increased by 166 % and 114 %. Therefore, this µGCC is promising for separating light hydrocarbons with widely differing concentrations.

[Effects of moxibustion on acupoints at "opening" time on testicular tissue apoptosis in aging rats].

OBJECTIVE: To observe the effect of "lingguibafa" moxibustion at "opening" time on the level of superoxide dismutase(SOD), malondialdehyde(MDA), the protein expressions of B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in aging model rats. METHODS: SD rats were randomly divided into blank control, model and lingguibafa groups, with 8 rats in each group. The aging model was established by daily intraperitoneal injection of D-galactose (500 mg/kg) for 42 consecutive days. After successful modeling, moxibustion intervention was applied at"lingguibafa" acupoints, 3 moxa-cone for each acupoint, once a day for 28 consecutive days. The contents of SOD and MDA in serum were detected by ELISA. Morphological changes of testicular tissue and the number of Leydig cells were observed after HE staining. Apoptosis rate of testicular cells was detected by TUNEL staining. The protein expression levels of Bcl-2 and Bax in testis were detected by Western blot. RESULTS: Compared with the blank control group, the SOD content in the serum, the number of testicular Leydig cells, the expression level of Bcl-2 protein in testis were significantly decreased (P<0.01) in the model group, while the MDA content in the serum, the apoptosis rate of testicular cells and the expression level of Bax protein in testis were significantly increased (P<0.01). Compared with the model group, the SOD content in serum, the number of testicular Leydig cells, the Bcl-2 protein expression in testis were significantly increased (P<0.01), while the MDA content in serum, the apoptosis rate of testicular cells, the expression level of Bax protein in testis were significantly decreased(P<0.01) in the lingguibafa group. CONCLUSION: Moxibustion on acupoints at "opening" time can delay testicular aging, and the mechanism may be related to balancing the metabolism of free radicals, reducing oxidative damage, and inhibiting the apoptosis of testicular cells.

A semi-packed gas chromatography column with high-density elliptic cylindrical posts.

Semi-packed columns are microfabricated gas chromatography columns which have a large surface area and high aspect ratio. In this paper, a new semi-packed column with high-density elliptic cylindrical posts (SCHECP) made by a micro-electro-mechanical system (MEMS) technique was reported. Compared to a semi-packed column with cylindrical posts (SCCP) under the same effective width, the surface area and aspect ratio of SCHECP were improved by 71.19% and 76.47%, respectively. To compare the performance of these two semi-packed columns, SCHECP and SCCP were fabricated. A 10-nm thick alumina film was deposited as the stationary phase by atomic layer deposition technique to ensure the uniformity and repeatability of the stationary-phase film. A contrast experiment was conducted, and the results showed that compared with SCCP, better separation performance was realized in SCHECP due to the increase in surface area and aspect ratio. The number of theoretical plates of nonane was increased by 541.84%, and the tailing factor was decreased by 54.31%.

Cytoglobin ameliorates the stemness of hepatocellular carcinoma via coupling oxidative-nitrosative stress signals.

Cancer stem cells (CSCs) account for tumor self-renewal and heterogeneity. Oxidative-nitrosative stress (ONS) is an independent etiologic factor throughout tumorigenesis. Emerging evidences indicated that the interaction of ONS with CSCs contributes to tumor progression and resistance to chemoradiotherapy. Cytoglobin (Cygb) is a member of human hexacoordinate hemoglobin family and acts as a dynamic mediator of redox homeostasis. We observed that Cygb is significantly deregulated in human hepatocellular carcinoma (HCC) tissue and its decrease aggravates the growth of liver cancer stem cells (LCSCs) and increases the subpopulation of CD133(+) LCSCs. Cygb restoration inhibits HCC proliferation and LCSC growth, and decreases the subpopulation of CD133 (+) LCSCs in vitro. We found that Cygb absence promotes LCSC phenotypes and PI3 K/AKT activation, whereas Cygb restoration inhibits LCSC phenotypes and PI3 K/AKT activation. Furthermore, exogenous antioxidants can eliminate the inhibitory effect of Cygb to LCSC growth and phenotypes, as well as PI3 K/AKT activation. Collectively, this study demonstrated that cytoglobin functions as a tumor suppressor and targets CSCs at an ONS-dependent manner. Thus, Cygb restoration could be a novel and promising therapeutic strategy against HCC with aberrant ROS/RNS accumulation.