Determination of linear aliphatic aldehydes in heavy metal containing waters by high-performance liquid chromatography using 2,4-dinitrophenylhydrazine derivatization

A simple and sensitive method is described for the determination of picomolar amounts of C₁–C₉ linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7–28 nM. The detection limit can be further lowered by using off-line C₁₈ adsorption cartridge enrichment. The recoveries of C₁–C₉ aldehydes were 93–115% with a relative standard deviation of 3.6–8.1% at the 0.1 μM level for aldehydes. The HPLC–DNPH method has been applied for determining aldehyde photoproducts from Cu(II)–amino acid complex systems.     

Rapid optimization of dual-mode gradient high performance liquid chromatographic separation of Radix et Rhizoma Salviae Miltiorrhizae by response surface methodology

An approach for rapid optimization of dual-mode gradient high performance liquid chromatography (HPLC) by response surface methodology (RSM) was developed for fast simultaneous separation of hydrophilic and hydrophobic components in Radix et Rhizoma Salviae Miltiorrhizae (Danshen) and its preparations. The aim of this study was to achieve a high throughput RSM optimization using a short ultra-high performance liquid chromatographic (UHPLC) column to simultaneously optimize flow rate and solvent gradient, and then transfer the optimized method to conventional HPLC for routine analytical purposes. The optimization was designed with Box Behnken design (BBD) and the global Derringer's desirability was used for describing the multicriteria response variables. Sixty-two designed experiments were performed by UHPLC with a short sub-2 μm column (2.1 mm × 50 mm, 1.7 μm) and a total running time of only 5 h. The predicted gradient profile was further transferred to a long UHPLC column (2.1 mm × 100 mm, 1.7 μm) and a conventional HPLC columns (2.1 mm × 100 mm, 3.5 μm and 4 mm × 100 mm, 5 μm, respectively). Compared to the published methods, the newly developed dual-mode gradient is faster and more efficient at simultaneously separating hydrophilic and hydrophobic components in Danshen and its preparations.     

Surface characterization of immunosensor conjugated with gold nanoparticles based on cyclic voltammetry and X-ray photoelectron spectroscopy

This investigation describes the surface characterization of rabbit immunoglobulin G (IgG) conjugated with gold nanoparticles. Goat anti-rabbit immunoglobulin G tagged with 5 nm gold nanoparticles was applied to detect the IgG. Then, the autocatalyzed deposition of Au³⁺ onto the surface of anti-IgGAu increased the surface area per gold nanoparticle. The immobilization chemistries and the atomic concentrations of Au_4f, P_2p, S_2p, C_1s, N_1s and O_1s of the resulting antibody-modified Au electrodes were determined by X-ray photoelectron spectroscopy (XPS). The sulfur that is involved in the cysteamine binding and the enlargement of the gold nanoparticles are identified using cyclic voltammetry. The results reveal that the surface area per gold particle, following the autocatalyzed deposition Au³⁺ on the surface of anti-IgGAu, was approximately seven times higher than that before deposition.     

Secondary metabolites isolated from the fungus <Emphasis Type="Italic">Biscogniauxia cylindrospora</Emphasis> BCRC 33717

One new dihydroisocoumarin, (3S)-5-hydroxy-8-O-methylmellein (1), as well as nine known compounds, 5-formylmellein (2), mellein-5-carboxylic acid (3), 5-hydroxymethylmellein (4), 3β-hydroxystigmast-5- en-7-one (5), N-trans-feruloyltyramine (6), N-cis-feruloyltyramine (7), vanillic acid (8), methyl paraben (9), and syringaldehyde (10), were isolated from the n-BuOH-soluble fraction of the 70% EtOH extract of rice fermented with the endophytic fungus Biscogniauxia cylindrospora (BCRC 33717). Their structures were elucidated by 1D and 2D NMR spectroscopy together with HR-ESI-MS analysis and comparison of the spectroscopic data with those reported for structurally related compounds.     

Synthesis and properties of new tetrachlorocobaltate (II) and tetrachloromanganate (II) anion salts with dicationic counterions

New tetrachlorocobaltate (II) and tetrachloromanganate (II) ionic compounds containing various counterdications were synthesized and characterized. These salts are soluble in polar solvents such as methanol and water. Physical properties such as thermal stability, melting point, and magnetic susceptibility of these salts depend on the cation or anion structure. The thermal stability of the phosphinium or imidazolium based salts is higher than that of the pyridinium or triethylaminonium analogues. The melting point of these compounds is following the order of triphenylphosphinium > pyridinium > imidazolium dications, and symmetrical dicationic salts > unsymmetrical ones. The magnetic susceptibility (χ_MT values) of tetrachloromanganate (II) anions-based salts is higher than that of tetrachlorocobaltate (II) anions-based salts. These dicationic salts exhibit weak antiferromagnetic interactions and have higher magnetic susceptibility than that of the previously reported tetrachloromanganate (II) and tetrachlorocobaltate(II) salts with monocationic counterion.     

1-Million droplet array with wide-field fluorescence imaging for digital PCR

Digital droplet reactors are useful as chemical and biological containers to discretize reagents into picolitre or nanolitre volumes for analysis of single cells, organisms, or molecules. However, most DNA based assays require processing of samples on the order of tens of microlitres and contain as few as one to as many as millions of fragments to be detected. Presented in this work is a droplet microfluidic platform and fluorescence imaging setup designed to better meet the needs of the high-throughput and high-dynamic-range by integrating multiple high-throughput droplet processing schemes on the chip. The design is capable of generating over 1-million, monodisperse, 50 picolitre droplets in 2-7 minutes that then self-assemble into high density 3-dimensional sphere packing configurations in a large viewing chamber for visualization and analysis. This device then undergoes on-chip polymerase chain reaction (PCR) amplification and fluorescence detection to digitally quantify the sample's nucleic acid contents. Wide-field fluorescence images are captured using a low cost 21-megapixel digital camera and macro-lens with an 8-12 cm(2) field-of-view at 1× to 0.85× magnification, respectively. We demonstrate both end-point and real-time imaging ability to perform on-chip quantitative digital PCR analysis of the entire droplet array. Compared to previous work, this highly integrated design yields a 100-fold increase in the number of on-chip digitized reactors with simultaneous fluorescence imaging for digital PCR based assays.     

cis-Dithiolatonickel as metalloligand to dinitrosyl iron units: the di-metallic structure of Ni(μ-SR)[Fe(NO)2] and an unexpected, abbreviated metalloadamantyl cluster, Ni2(μ-SR)4[Fe(NO)2]3

The reaction of Fe(CO)(2)(NO)(2) and Ni(N(2)S(2)) (N(2)S(2) = N,N'-Bis(2-mercaptoethyl)-1,4-diazacycloheptane) by a single CO replacement yields [Ni(N(2)S(2))]Fe(NO)(2)(CO), while an excess of Fe(CO)(2)(NO)(2) leads to triply bridging thiolate sulphurs in a cluster of core composition Ni(2)S(4)Fe(3), lacking one Fe(NO)(2) unit to complete the adamantane-like structure. This structural type was earlier identified in a Cu(I)Cl aggregate of M(II)(N(2)S(2)) (M(II) = Ni, Cu), in which complete M(II)(2)S(4)Cu(I)(4) core structures were obtained as the major, and, in the case of Cu(II)(N(2)S(2)), the incomplete Cu(II)(2)S(4)Cu(I)(3) as a minor, product. The full Ni(2)S(4)Fe(4) cluster has not yet been realized for Fe = Fe(NO)(2). Computational analysis of the NiFe-heterobimetallic complex addresses structural issues including a ∠Ni-S-Fe of 90° in the bimetallic complex.     

Determination of bile acids in pig liver, pig kidney and bovine liver by gas chromatography-chemical ionization tandem mass spectrometry with total ion chromatograms and extraction ion chromatograms

An effective method has been developed for quantitative determination of six bile acids including lithocholic acid (LCA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), hydodeoxycholic acid (HDCA), cholic acid (CA) and ursodeoxycholic acid (UDCA) in biological tissues including pig liver, pig kidney and bovine liver by gas chromatography-chemical ionization/tandem mass spectrometry (GC-CI/MS/MS). Camphor-10-sulphonic acid (CSA) was proposed as effective catalyst for bile acid derivatization. Reactions were accelerated ultrasonically. The effects of different catalysts and reaction times on derivatization efficiency were evaluated and optimized. Bile acids were determined as methyl ester-trimethylsilyl ether and methyl ester-acetate derivatives. The efficiency of trimethylsilylation and acetylation was evaluated. Trimethylsilylation was done with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as the trimethylsilyl donating reagent in a ultrasonic bath for 20 min. Acetylation was done in pyridine with acetic anhydride at 40-45°C for 4 h. The former reaction was faster than the latter. Thus, trimethylsilylation was employed for the quantitative analysis. Negligible interferences from sterols in biological matrices were observed when the biological samples were treated with solid phase extraction before GC-CI/MS/MS. The linearity, reproducibility, detection limit and recovery were evaluated under the optimized conditions. Satisfactory results were obtained when bile acid derivatives of LCA, CDCA, HDCA, and UDCA were determined with total ion chromatograms (TIC) while DCA and CA were determined with extracted ion chromatograms (EIC), respectively. The detection limits (S/N=3) for six bile acids in biological tissues were ranging from 0.40 to 1.6 ng/mL and the recoveries indicated that the proposed method was feasible for the determination of trace bile acids in the biological samples studied. The experimental results for the animal tissues purchased from five different markets were compared. Interestingly, all of the six bile acids were present in pig liver while only the dihydroxy bile acids, DCA, CDCA and HDCA were found in pig kidney. In addition to DCA and CDCA, trihydroxy bile acid, CA, are the major bile acids in bovine liver.     

The isolation and purification of pre-S2 containing hepatitis B virus surface antigen by chemical affinity chromatography

A simple, rapid, and efficient method was developed to isolate and purify pre-S2 containing HBsAgs from the plasma of a single chronic carrier of HBsAg (adw) by ammonium sulfate fractionation, hydroxyapatite column chromatography, and polymerized human serum albumin-affinity column chromatography. About 500 μg of pre-S2 containing HBsAg was obtained from 140 mL of plasma containing 4,200 μg of HBsAg. Two purified pre-S2 containing HBsAgs were analyzed by SDS-polyacrylamide gel electrophoresis and their molecular weights were determined to be 31,000 and 68,000 respectively. No significant amount of HBsAg or its derivative was detected in the final product.     

Determination of a cyclic heptapeptide, a novel fibrinogen receptor antagonist, in human plasma by high-performance liquid chromatography with automated pre-column derivatization, column switching and fluorescence detection.

A sensitive high-performance liquid chromatographic (HPLC) assay for the determination of the cyclic heptapeptide Ac-Cs-Asn-Dtc-Amf-Gly-Asp-Cys-OH (Dtc = beta,beta-dimethylthioproline, Amf = p-aminomethylphenylalanine) in human plasma has been developed. The key steps in the assay include: solid-phase extraction of the drug from plasma, chemical derivatization of the primary amino group with naphthalene-2,3-dicarboxyaldehyde in the presence of N-acetyl-D-penicillamine as a nucleophile to form a fluorescent benzo[f]isoindole derivative, and HPLC with column switching to provide the necessary chromatographic separation of the derivative from endogenous plasma components. The assay has been validated in the concentration range 1-10 ng/ml of plasma.