Simultaneous determination of uric acid and creatinine in urine by an eco-friendly solvent-free high performance liquid chromatographic method

A simple, rapid, and eco-friendly analytical method for simultaneous determination of uric acid and creatinine in urine applying high performance liquid chromatography (HPLC) is described. After dilution, de-protein, and filtration, the sample solution was injected to separate the species with C-18 column by an eluent containing 0.05 M ammonium phosphate buffer at pH 7.4. An UV detector was used to monitor the separation of species at 235 nm. Optimum conditions for separation and detection were investigated. Results indicated that under optimized condition measurements were achieved within 13 min. The detection limits were 0.127 and 0.156 mug ml(-1) for uric acid and creatinine respectively. The recovery was 95% (0.57% RSD) for uric acid and 99.2% (0.98% RSD) for creatinine, from five measurements. Real urine specimens were tested.     

Chemical Constituents from the Root of Antidesma Pentandrum var. Barbatum

Investigation of the root extract of Antidesma pentandrum var. barbatum led to the isolation of seven new compounds, antidesmol ( 1 ), antidesmanins E ( 2 ) and F ( 3 ), antidesnone ( 4 ), antidesnol ( 5 ), barbatumols A ( 6 ) and B ( 7 ), together with 14 known compounds including sodium aristolochate‐I ( 10 ) and aristolochic acid‐I methyl ester ( 11 ).     

Determination of dichlorvos by on-line microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-electron-capture detection

The pretreatment technique of microwave-assisted extraction on-line headspace solid-phase microextraction (MAE-HS-SPME) was designed and studied for one-step in-situ sample preparation prior to the chromatographic analysis of a pesticide on vegetables. The pesticide on chopped vegetables was extracted into an aqueous solution with the aid of microwave irradiation and then directly onto the SPME fiber in headspace. After being collected on to the SPME fiber and desorbed in the GC injection port, the pesticide (dichlorvos) was analyzed with a GC-electron-capture detection system. The optimum conditions for obtaining extraction efficiency, such as the pH, the polarity modifier, and the salt added in sample solution, the microwave irradiation, as well as the desorption parameters were investigated. Experimental results indicated that the proposed MAE-HS-SPME technique attained the best extraction efficiency of 106% recovery under the optimized conditions, i.e. irradiation of extraction solution (10% aqueous ethylene glycol) at pH 5.0 with medium microwave power for 10 min. Desorption at 220 degrees C for 3 min offered the best detection result. The detection was linear at 5-75 microg/l with correlation coefficient of 0.9985. Detection limit was obtained at approximately 1.0 microg/l level based on S/N=3. The proposed method provided a very simple, fast, and solvent-less procedure to collect pesticides directly from vegetables for GC determination. Its application was illustrated by the analysis of trace dichlorvos in vegetables.     

Determination of aniline in silica gel sorbent by one-step in situ microwave-assisted desorption coupled to headspace solid-phase microextraction and GC-FID

Microwave-assisted desorption (MAD) coupled to in situ headspace solid-phase microextraction (HS-SPME) was first proposed as a possible alternative pretreatment of samples in absorbent collected from workplace monitoring. Aniline collected on silica gel was investigated. Under microwave irradiation, the aniline was desorbed from silica gel and directly absorbed onto the SPME fiber in the headspace. Having been sampled on the SPME fiber, and desorbed in the GC injection port, aniline was analyzed using a GC-FID system. Parameters that affect the proposed extraction efficiency, including the extraction media and its pH, the microwave irradiation power and the irradiation time as well as desorption parameters of the GC injector, were investigated. Experimental results revealed that the extraction of a 150-mg silica gel sample using a 0.8-ml aqueous solution (pH 12) and a PDMS/DVB fiber under medium-high-powered irradiation (345 W) for 3 min maximized the efficiency of extraction. Desorption of aniline from the SPME fiber was optimal at 230 °C held for 3 min. The detection limit was 0.09 ng. The proposed method provided a simple, fast, and organic solvent-free procedure to analyze aniline from a silica gel matrix.     

Constituents from Rubia Ustulata Diels and R. Yunnanensis Diels and Their Antiplatelet Aggregation Activity

A new anthraquinone glycoside, rubiayannone‐A ( 1 ), and a new coumarin, rubilatin‐A ( 2 ), together with twenty‐two known compounds were isolated and characterized from the roots of Rubia ustulata. A new anthraquinone, 2‐carbomethoxyanthraquinone ( 3 ), and rubiayannone‐A, 2‐formylanthraquinone were obtained from the roots of R. yunnanensis. The structures of those compounds were elucidated by spectroscopic methods. The antiplatelet aggregation activity of the isolated compounds 1, 4～6 were also discussed.     

Fast Multi‐residue Screening for 84 Pesticides in Tea by Gas Chromatography with Dual‐tower Auto‐sampler,Dual‐column and Dual Detectors

A fast multi‐residue screening method for determining pesticides in tea is described. Pesticides are extracted from tea with acetone and methylene chloride, then enriched and cleaned up with solid phase extraction (SPE) prior to gas chromatographic determination. The fast screening is achieved by a gas chromatograph system equipped with dual‐column, dual‐tower auto‐sampler and both electron capture detector (ECD) and flame photometric detector (FPD). Optimal conditions are investigated for the prospective pesticides including column selection, detection mode, the retention behaviors, quantitative calibration, as well as the recoveries and repeatability of pesticides from tea samples. Under the optimal conditions, with the FPD‐P detector accompanied CP‐SIL 13CB column, 48 pesticides can be separated well and detected within 38 min; and with a DB‐5 column, 35 ECD‐detectable pesticides can be separated and detected within 46 min. The recoveries of 84 pesticides in tea samples are 65–120% with 0.34–16% RSD for spiking 0.02–3.0 mg/kg standard species. Because of the thermal instability of most pesticides, direct cold extraction of pesticides from a tea sample is recommended. The proposed method provided a very fast and efficient procedure to screen 84 pesticides from a complicated tea sample matrix.     

The conceptual analysis (CA) method in theories of microchannels: Application to quantum theory. Part I. Fundamental concepts

A method is proposed that should facilitate the construction of theories of submicroscopic particles (denoted as theories of microchannels) in a way similar to the use of group-theoretical methods. The conceptual analysis (CA) method is based on the analysis of the basic concepts of a theory; it permits a determination of necessary conditions imposed on the mathematical apparatus (of the theory) which then appear as a mathematical representation of the structures obtained in a formal scheme of a theory. A pertinent conceptual analysis leads to a new definition (relativization) of the concept empirical implication. The approach may be characterized as realistic and operational. The application of the CA method is illustrated on the example of quantum theory. In Part I the algebraic structure of a partially ordered, up-ward directed, bounded set is deduced from the rudimentary concepts. In Parts II and III, we shall deduce the Hilbert-space structure (well established in quantum mechanics) from postulates on some essential idealizations accepted in the theory. Whereas Part II is concerned with the idealizations of existing quantum theories based on the Hilbert-space formalism, Part I may be considered as a general basis for a wider class of theories.Dedicated to Prof. G. Ludwig on the occasion of his 60th birthday.     

Urinary d‐lactate levels reflect renal function in aristolochic acid‐induced nephropathy in mice

Urinary d ‐lactate is highly correlated to diabetic nephropathy – a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d ‐lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N‐acetyl‐β‐d ‐glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d ‐lactate was analyzed using column‐switching high‐performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N‐acetyl‐β‐d ‐glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d ‐lactate to creatinine in the urine of aristolochic acid‐treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d ‐lactate reflects renal injury conditions in aristolochic acid‐treated mice and may be a marker for the assessment of nephropathy. Copyright © 2013 John Wiley & Sons, Ltd.