On-line Clean-up System Research Articles

Simultaneous determination of eight β-adrenergic agonists in human urine by an isotope dilution-online clean-up system coupled with liquid chromatography-tandem mass spectrometry

β-Adrenergic agonist compounds are medicines that open up the lung's medium and large airways. β-Adrenergic agonist compounds have been illegally or legally used to increase lean muscle mass in meat animals, bodybuilding, weight-loss programs, and athletes. Developing a rapid analytical approach for determining β-adrenergic agonist compounds in biological samples is crucial for individual exposure assessment. This study established an analytical method for simultaneously measuring eight β-adrenergic agonist compounds in human urine, including clenbuterol, terbutaline, salbutamol, ractopamine, zilpaterol, cimaterol, tulobuterol, and fenoterol. Two hundred microliters of a urine sample were added to eight deuterium-labeled internal standard mixtures and glucuronidase/arylsulfatase for enzymatic hydrolysis, and were then analyzed using an online clean-up system coupled with a liquid chromatography-tandem mass spectrometry system (LC–MS/MS). The limit of quantification ranged from 0.03 to 0.12 ng/mL urine for the eight β-adrenergic agonist compounds. The relative standard deviations (RSD) of the within-run and between-run precisions were less than 10%, and the relative accuracy errors were less than 17% in the three-level spiked artificial urine samples. Two hundred eighty human urine samples collected from the general population in Taiwan were assessed to demonstrate the capability and feasibility of this method. The detection frequencies were 33% for clenbuterol, 5% for ractopamine, and less than 5% for the others. We concluded that the isotope dilution-online clean-up system coupled with LC–MS/MS method is a valuable analytical method for investigating urinary β-adrenergic agonist compounds in humans and is valuable for human biomonitoring studies.

Turbulent flow and ternary column-switching on-line clean-up system for high-throughput quantification of risperidone and its main metabolite in plasma by LC–MS/MS: Application to a bioequivalence study

A high-throughput LC–MS/MS method was developed for the simultaneous determination of Risperidone and 9-OH-risperidone in human plasma. A semi-automated sample preparation procedure was applied, including protein precipitation after addition of ACN, via a robotic system, and subsequent sub-zero temperature extraction of the latter. Injections of the ACN extractants were performed on a turbulent flow ternary column-switching system, consisted of dual extraction columns in parallel for on-line purification of samples and an analytical column. Toggling with the assistance of two valves provided a run cycle time of 3 min and the whole procedure minimized carry-over effect. On-line clean-up procedure along with sub-zero temperature extraction increased sample purification and extended column life. The analytical range of the method was 0.1–200 ng mL −1 for both analytes with excellent linearity and very good accuracy and precision. The proposed method was employed in a bioequivalence study after per os administration of a 2 mg tablet of risperidone and allowed the completion of the study (>1400 samples) in only 4 days time.

Quantification of urinary N‐acetyl‐S‐ (propionamide)cysteine using an on‐line clean‐up system coupled with liquid chromatography/tandem mass spectrometry

Acrylamide has been reported to be present in high-temperature processed foods and normal processed food intake could lead to significant acrylamide exposure. Acrylamide in vivo can be conjugated with glutathione in the presence of glutathione transferase. This conjugation product is further metabolized and excreted as N-acetyl-S-(propionamide)cysteine (NASPC) in the urine. NASPC could be considered a biomarker for acrylamide exposure. The objective of this study was to develop a highly specific, rapid and sensitive method to quantify urinary NASPC, serving as a biomarker for acrylamide exposure assessment. Isotope-labeled [13C3]NASPC was successfully synthesized and used as an internal standard. This urine mixture was directly analyzed using a newly developed liquid chromatographic/tandem mass spectrometric method coupled with an on-line clean-up system. The detection limit for this method was estimated as < 5 microg l(-1)(0.4 pmol) on-column. The method was applied to measure the urinary level of NASPC in 70 apparently health subjects. The results showed that the NASPC urinary level was highly associated with smoking. Smokers had a significantly higher urinary NASPC level (135 +/- 88 microg g(-1) creatinine) than non-smokers (76 +/- 30 microg g(-1) creatinine). A highly sensitive and selective LC/MS/MS isotope dilution method was successfully established. With an on-line clean-up system, this system is capable of routine high-throughput analysis and accurate quantitation of NASPC in urine. This could be a useful tool for health surveillance for acrylamide exposure in a population for future study.

Graphite furnace atomic absorption spectrometric determination of some noble metals using flow injection on-line clean-up

In this paper, a flow injection on-line clean-up system was developed for determination of trace Pt, Pd and Au in the presence of Na+, K+, Ca2+, Mg2+, Fe3+ and Al3+ by electrothermal atomic absorption spectrometry (ETAAS). A column packed with strongly acidic cation-exchange resin (Type 732) was used as a clean-up column. As Pt2+, Pd2+ and Au3+ can form strong complex anions with Cl− in HCl medium, they can be separated from coexisting cations by passing through the clean-up column. The experimental results obtained for trace amounts of gold in reference materials were in good agreement with the certified values.

A simple flow-injection on-line clean-up system for microwave plasma-torch atomic emission spectrometry.

A simple flow injection (FI) on-line clean-up system has been developed for microwave plasma-torch atomic emission spectrometry (MPT-AES). A non-selective strongly acidic cation-exchange resin was used to achieve the goal of "on-line clean-up". Ag and Zr, which form halogen-complex anions in halide acid media, and Cr, Mo, and P, which exist as acid group anions or acids (neutral) in acidic solution, were determined and the interfering matrix cations were removed on-line. Satisfactory analytical results were obtained from some practical samples by use of this procedure.

Rapid Determination of Tetracycline Antibiotics in Milk by HPLC Using an On-line Clean-up System

A rapid and simple method for the analysis of four kinds of tetracycline antibiotics (TCs), oxytetracycline, tetracycline, chlortetracycline and doxycycline, was established by HPLC using an on-line clean-up system. Co-existing substances in milk were removed by a precolumn head-cut-loading method. TCs retained in the precolumn were rapidly loaded on an analytical column after changing the eluent. The co-existing substances retained in the precolumn was removed by back-flash washing. Sodium octanesulfonate was effective as a counter ion in the mobile phase for separation of TCs on the analytical column. Determination of TCs in milk by this method could be carried out only after deproteinization with 20% trifluoroacetic acid. Recoveries of TCs from milk fortified at 0.03, 0.05, 0.1, 0.5 and 1.0mg/L ranged from 80.2 to 104.3%. Detection limits were 0.01mg/L for all four TCs.

On-line Clean-up System of Plasma Sample for Simultaneous Determination of Morphine and Its Metabolites in Cancer Patients by High-Performance Liquid Chromatography

A convenient and sensitive analytical method for determination of plasma morphine and its metabolites in cancer patients was established using HPLC with a column-switching technique. Sample plasma which has been deproteinized with trichloroacetic acid is injected onto a precolumn, then the compounds of interest are preferentially introduced into the analytical column for separation and detection after washing out the unnecessary plasma components from the precolumn. Detection was simultaneously performed with coulometry for unchanged morphine and morphine-6-glucuronide and with UV analysis for morphine-3-glucuronide. Analytical recoveries were >99% for these compounds, and the averaged coefficients of within-day or between-day variation did not exceed 5.5%. Detection limits were 0.2 ng/mL for morphine, 0.5 ng/mL for morphine-6-glucuronide, and 10 ng/mL for morphine-3-glucuronide. Correlation between the previously reported solid extraction method and this method was satisfactory in plasma samples after administration of morphine.

Determination of Orotic Acid by Liquid Chromatography as a Criterion for Calculating Nonfat Milk Solids in Milk Bread

Abstract A sensitive and reproducible isocratic liquid chromatographic method is described for the determination of orotic acid levels in skim milk powder and milk bread. The results are used to calculate the nonfat milk solids content in milk bread. Sample preparation is simple and rapid and produces an extract which, after passing through an on-line cleanup system, has a minimum adverse effect on the performance and life of the analytical column. Mean recoveries of 96-105% were obtained with coefficients of variation in the range 1.0-8.5% and a detection limit of 5 mg/kg. The liquid chromatographic method was more sensitive than the standard colorimetric method, while results obtained by both methods agreed closely.

A New Steam-Cooled Reactor

A new ultrasafe type of nuclear power plant is described that has a complete ''walk-awayfrom'' characteristic. That is, the reactor can safely dissipate its shutdown heat even if its powe and water supplies are cut off. The reactor is steam cooled and is designed to operate at one fixed steam density. Its reactivity characteristics are such that if the power level increases, the steam becomes less dense than the optimum and tends to shut the reactor off. Similarly, if the reactor is flooded wit water, the reactivity greatly decreases and also shuts the reactor down. The reactor can be operated as a burner, a high-efficiency converter, or a breeder, depending on the isotopic content of the fuel. The plant operates at low pressure and relatively high efficiency with an example given at 1000 psia and 35% efficiency. The reactor is enclosed in a conventional steel vessel resembling a boiling water reactor. The vessel is connected to a large atmospheric pressure pool of water, and shutdown consists of passively cou pling the pool to the reactor through the loss of steam flow. Shutdown cooling is provided by forced air and natural draft convection cooling of the pressure vessel. Sufficient water andmore » passive cooling are provided by the pool for many months of shutdown water cooling. The plant piping is double walled, and all paths of radiation escape, including pressure-vessel cracking, are channeled through an on-line cleanup system.« less