Biomedical subjects

Shifen Mou

Publications and source records attributed to Shifen Mou.

At least 19 recordsLinked to original sources

PubMed2006

Determination of trace levels of bromate in flour and related foods by ion chromatography.

In this paper, a method of determining trace levels of bromate in flour and related foods by ion chromatography with large volume injection has been proposed. The detection of bromate was performed with a suppressed conductivity detector after separation on an IonPac AS19 column with KOH as the gradient eluent. Parameters affecting the extraction efficiency of bromate, such as the flour-to-water ratio, extraction time, and temperature, were studied in detail. The optimized pretreatment process was then selected. By using the large volume injection technique, the solution detection limit was decreased to 0.5 microg/L. The linear range of this method was from 5 to 1000 microg/L, and the linear correlation coefficient was 0.9998. The method has been applied to the detection of bromate in flour and related foods, and different concentration levels of bromate were detected in various samples. The spiked recoveries ranged from 86 to 110%. The relative standard deviation (RSD) of the bromate peak height for the seven successive injections of the flour sample was 6.4%.

Bromates↗

PubMed2006

Selenium speciation by high-performance anion-exchange chromatography-post-column UV irradiation coupled with atomic fluorescence spectrometry.

A technique for the speciation of selenomethylcysteine (SeMeCys), selenocystine (SeCys), selenite [Se(IV)] and selenomethionine (SeMet) was established in this paper using high-performance anion-exchange chromatography coupled with atomic fluorescence spectrometry (HPAEC-AFS). Analytes were separated on an AminoPac PA10 column and then digested by on-line ultraviolet (UV) irradiation, which destroyed organic compound structure. Hydride generation was used as an available sample introduction technique for atomic fluorescence detection. The detection limits of four compounds were 1-5 microg/L (250 microL injection, 10 times of the baseline noise). The relative standard deviations (RSDs), calculated from seven consecutive injections of 100 microg/L standard mixtures, were from 2 to 4%. Selenious yeast tablet, which had been proposed as selenium supplement, and human urine collected from a volunteer were analyzed. Good spiked recoveries from 86 to 103% were obtained.

Chromatography, High Pressure Liquid↗

PubMed2006

Direct amino acid analysis method for speciation of selenoamino acids using high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection.

Speciation analysis of selenomethylcysteine (SeMeCys), selenomethionine (SeMet) and selenocystine (SeCys) has been performed using a direct amino acid analysis method with high-performance anion-exchange chromatography (HPAEC) coupled with integrated pulsed amperometric detection (IPAD). Three selenoamino acids could be baseline-separated from 19 amino acids using gradient elution conditions for amino acids and determined under new six-potential waveform. Detection limits for SeMeCys, SeMet and SeCys were 0.25, 1 and 20 microg/L (25 microL injection, 10 times of the baseline noise), respectively. The relative standard deviations (RSDs) of 200 microg/L SeMeCys, SeMet and SeCys were 3.1, 4.1 and 2.8%, respectively (n=9, 25 microL injection). The proposed method has been applied for determination of selenoamino acids in extracts of garlic and selenious yeast granule samples. No selenoamino acids were found in garlic. Both SeMet and SeCys were detected in selenious yeast tablet with the content of 45 and 129 microg Se/g, respectively. Selenoamino acids standards were spiked in garlic and yeast granule samples and the recovery ranged from 90 to 106%.

Amino Acids↗

PubMed2005

Optimizing the integrated pulsed amperometric multicycle step waveform for the determination of tetracyclines.

A method of modified integrated pulsed amperometric detection with multicycle step waveform (Multi-IPAD) following high-performance liquid chromatography (HPLC) was applied for the determination of tetracyclines (TCs) including dimethyltetracycline (DMTC), oxytetracycline (OTC) and tetracycline (TC). The key advantages of the Multi-IPAD are the abilities to enhance sensitivity and reproducibility and the ability to keep working electrode clean through the use of a high-frequent waveform alteration in integration step and the use of a cleaning potential, which is quite different from conventional three-step potential waveform. The analyses were carried out using the mobile phase of acetonitrile-water mixture solution (10:90, v/v) containing 1% perchloric acid on a C(18) column at a flow rate of 0.21 mL/min. The IPAD waveform parameters were optimized to maximize the signal-to-noise ratio (S/N) and successfully applied for the sensitive detection of TCs. The detection limits (S/N=3, 20 microL injected) were 0.07 mg/L for DMTC, 0.08 mg/L for OTC and 0.05 mg/L for TC. The peak height relative standard deviations (RSDs) of every compound for replicate injection (n=15) determined were below 4.6%.

Chromatography, High Pressure Liquid↗

PubMed2005

Determination of several sugars in serum by high-performance anion-exchange chromatography with pulsed amperometric detection.

In this paper, a sensitive, simple and direct method for simultaneous determination of glucose, ribose, isomaltose and maltose in serum sample by high-performance anion-exchange chromatography coupled with integrated pulsed amperometric detection was developed. The four target analytes were easily and completely separated on an anion-exchange column at a flow-rate of 0.25 mL/min by binary step gradient elution in about 16 min and the two eluents were deionized water and 500 mM sodium hydroxide, respectively. The separated four analytes were detected directly by using a gold electrode and quadruple-potential waveform integrated pulsed amperometry without derivatization. Under the optimized conditions, when the injection volume was 25 microL, the detection limits (signal-to-noise ratio equal to 3) for glucose, ribose, isomaltose and maltose were 0.92, 7.50, 12.9 and 10.3 ng/mL, respectively. The calibration graphs of peak area for the four analytes were linear over two to three orders of magnitude with correlation coefficients greater than 0.998. R.S.D. of peak areas of the four analytes for five determinations were no more than 5.6%. The analytical method had been applied to the determination of glucose, ribose, isomaltose and maltose in real serum samples and good results with low relative standard deviation not more than 5.3% were obtained. The accuracy of the proposed method was tested by recovery measurements on spiked samples and good recovery results (98.1-107.9%) were obtained.

Carbohydrates↗

PubMed2005

Comparisons of disposable and conventional silver working electrode for the determination of iodide using high-performance anion-exchange chromatography with pulsed amperometric detection.

The paper compared the performance of two kinds of silver working electrode in electrochemical detector-the disposable and conventional electrode for the determination of iodide using high-performance anion-exchange chromatography (HPAEC) hyphenated with pulsed amperometric detection (PAD). The comparisons were carried out on the time of equilibration, long and short-term reproducibility, limits of detection and linearity of calibration. Results showed that disposable working electrode manifested equal or better results than conventional working electrode and could be used for iodide analysis. Besides, the disposable electrode could work for consecutive 2660 min (about 44 h, 10 min needed for each run) with no degradation. Due to its "disposable" property, disposable working electrode could be discarded if the detection sensitivity decreased to 80% so the time for polishing and reconditioning was spared and good reproducible results could be obtained. At last, the disposable electrode was applied for the determination of iodide in soil and sea water samples with the spiked recovery ranging from 96-104% and the detection limit of 0.5 microg/L (10 microL injection, three times of the baseline noise).

Anion Exchange Resins↗

PubMed2005

Comparative study on the analytical performance of three waveforms for the determination of several aminoglycoside antibiotics with high performance liquid chromatography using amperometric detection.

A preliminary comparative study was carried out on the analytical performances of a new six-potential waveform and other two detection waveforms, triple-potential waveform and quadruple-potential waveform. The analytical performances compared included signal response, background noise, signal/noise ratio and signal stability. Compared with triple-potential waveform and quadruple-potential waveform, the new six-potential waveform had higher signal response, signal/noise ratio, and sensitivity. As for determination reproducibility, the six-potential waveform also exhibited a slightly better performance than the other two waveforms. Under the selected experimental conditions based on the six-potential waveform, there is a linear correlation between peak area and concentration over two to three orders of magnitude for nine aminoglycoside antibiotics with a correlation coefficients better than 0.998 and the detection limits measured as three times the peak height signal-to-noise ratio for the nine aminoglycoside antibiotics were in the range of 0.0198-0.889 microg/mL. The proposed method had been used to analyze real gentamicin sulphate drug sample.

Aminoglycosides↗

PubMed2005

[Application of high performance anion exchange chromatography for trace analysis of polarizable anions].

Polarizable anions such as Br-, S2O3(2-), I- and SCN- were separated using 45 mmol/L sodium hydroxide solution as the mobile phase on a high hydrophilic IonPac AS16 column. With a pulsed amperometric detector, the detection limits were 0.5, 0.2, 0.05 and 2 microg/L (25.0 microL injected, signal-to-noise ratio of 3) for Br-, S2O3(2-), I- and SCN. The relative standard deviation (RSD) range of trace anions was from 0.8% to 3.7% (n = 9). Under the same chromatographic conditions, these anions were also determined using a suppressed conductivity detector and the detection limits were 1, 1, 2 and 10 microg/L (25 microL injected, signal-to-noise ratio of 3), respectively. The RSD range was from 0.9% to 4.7% (n = 9). Comparing a pulsed amperometric detector with a conductivity detector, the former is 2 to 40 times more sensitive than the latter. For the determination of polarizable anions, a pulsed amperometric detector has higher selectivity, precision and sensitivity.

Anion Exchange Resins↗

PubMed2004

Optimizing the quadruple-potential waveform for the pulsed amperometric detection of neomycin.

Determination of neomycin is important for quality control of the pharmaceutical preparation. A quadruple-potential waveform used for pulsed amperometric detection of neomycin was investigated. The waveform cleans the electrode by application of a potential more negative than the potential limit to avoid the formation of gold oxide during applying positive potential to clean gold electrode, thus decreasing the dissolution resulting recession of the gold working electrode within gold oxide formation/reduction cycles in the triple-potential waveform. Waveform parameters were optimized to maximize the signal-to-noise ratio (S/N). The detection limit of neomycin B is lower than 0.01 microg/ml. The linearity of framycetin (plotted as peak area of neomycin B) ranges from 0.05 to 100 microg/ml with correlation coefficient 0.9998. R.S.D. (n = 60) of the peak area of neomycin B is lower than 2%. The quadruple-potential waveform shows low detection limits and long-term reproducibility.

Chromatography, Liquid↗

PubMed2004

Determination of trace-level haloacetic acids in drinking water by ion chromatography-inductively coupled plasma mass spectrometry.

A new method for the determination of nine haloacetic acids (HAAs) with ion chromatography (IC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was developed. With the very hydrophilic anion-exchange column and steep gradient of sodium hydroxide, the nine HAAs could be well separated in 15 min. After suppression with an ASRS suppressor that was introduced in between IC and ICP-MS, the background was much decreased, the interference caused by sodium ion present in eluent was removed, and the sensitivities of HAAs were greatly improved. The chlorinated and brominated HAAs could be detected as 35ClO and 79Br without interference of the matrix due to the elemental selective ICP-MS. The detection limits for mono-, di-, trichloroacetic acids were between 15.6 and 23.6 microg/l. For the other six bromine-containing HAAs, the detection limits were between 0.34 and 0.99 microg/l. With the pretreatment of OnGuard Ag cartridge to remove high concentration of chloride in sample, the developed method could be applied to the determination of HAAs in many drinking water matrices.

Acetates↗

PubMed2004

Analysis of benzyldimethyldodecylammonium bromide in chemical disinfectants by liquid chromatography and capillary electrophoresis.

Two novel analytical methodologies using capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were developed and compared for the determination of benzyldimethyldodecylammonium bromide (BAB) in commercial compound chemical disinfectants. The LC analysis was performed with a Kromasil C18 (200 mm x 4.6 mm, 5 microm) column and a mobile phase of A:B = 80:20 (A: acetonitrile, B: 4 mmol/L octanesulfonic sodium--0.02 mol/L acetic sodium, adjusted with acetic acid to pH 5.2) at a flow rate of 1.0 mL/min. Detection was by ultraviolet absorption at 262 nm. The CE analysis was performed in a bare fused-silica capillary with 75 microm i.d. and total length of 46.4 cm with a buffer solution of 50% acetonitrile -50 mmol/L NaH2PO4, pH 2.24. The applied voltage was 20 kV. Detection was by ultraviolet absorption at 214 nm. Under optimized conditions, the HPLC retention time and CE migration time for BAB was 9.18 and 5.08 min, respectively. Calibration curves of peak area versus concentration gave correlation coefficients of 0.9996 for HPLC and 0.9994 for CE. The detection limits for HPLC and CE were 1.6 mg/L and 0.2 mg/L, respectively. Average recoveries at three concentration levels (50, 100, 200 mg/L for HPLC: 20, 40, 100 mg/L for CE) were 99.94 +/- 1.5, 99.64 +/- 1.3 and 99.61 +/- 0.4% for HPLC and 120.47 +/- 2.6, 102.06 +/- 8.7 and 103.05 +/- 3.0% for CE, respectively. Although both methods were shown to be suitable for the determination of BAB in commercial disinfectant compounds, CE provided analysis with less solvent purchase/disposal and better column efficiency, whereas HPLC provided superior precision.

Benzalkonium Compounds↗

PubMed2004

Determination of bromate and chlorinated haloacetic acids in bottled drinking water with chromatographic methods.

Disinfection by-products of interest such as bromate, chlorate and chlorinated haloacetic acids in 10 representative brands of bottled drinking water were investigated with ion chromatography. With the developed method, the detection limits of the disinfection by-products were in sub-microgl(-1) level. It was observed that bromate, chlorate and dichloroacetic acid could be detected in some water samples. In the bottled natural water, the concentrations for the three compounds were 0.1, 0.9 and 0.6 microgl(-1), respectively. The total concentration of disinfection by-products in the natural water sample was the highest among all the bottled drinking waters. The concentrations for the sum of disinfection by-products in the four types of bottled drinking water investigated were natural water > mineral water > spring water > purified water. The generation of disinfection by-products was much influenced by the original components and process procedure of the source water. The concentrations of bromate and chlorate in the bottled water samples hardly degraded with the increasing storage time. For dichloroacetic acid, with the prolonging of storage time, the concentration was much decreased.

Acetates↗

PubMed2004

[Determination of choline chloride and trimethylamine in feedstuff by ion chromatography].

A method was developed for the determination of choline chloride (CC) and trimethylamine (TMA) in feedstuff by ion chromatography. The separation of eight ions including Li+, Na+, NH4+, K+, TMA, choline, Mg2+ and Ca2+ was achieved by using an IonPac CS12 column (250 mm x 4 mm i.d.) and 8.5 mmol/L H2SO4 as eluent. Cations were detected by suppressed conductivity detection. The limits of detection of CC and TMA were 0.1 mg/L and 0.05 mg/L, respectively. The method recoveries were between 99.25% and 102.5%. The method was sensitive, selective, and simple. The results of sample analysis showed that the method was very useful for the authenticating of choline chloride in feedstuffs.

Animal Feed↗

PubMed2004

[Development of analytical methods for amino acids and their applications].

Different analytical methods for amino acids, including ion exchange chromatography (IEC), high performance liquid chromatography (HPLC), gas chromatography (GC) and capillary electrophoresis (CE) are introduced in light of derivatization. High performance anionic exchange chromatography with integrated pulsed amperometric detection (HPAEC-IPAD) method for direct amino acid analysis was also presented. The applications of the methods for amino acid analysis in proteins, foods, physiological fluids and chiral separation as well are also reviewed.

Amino Acids↗

PubMed2004

[Determination of anions, cations and organic acids in the oil field water by ion chromatography].

A method for the determination of anions, cations and organic acids in the oil field water with high chloride and sodium ions was developed by ion chromatography (IC) with a conductivity detector. The separation of the cations was achieved on an IonPac CS12A column with H2SO4 as the eluent. The separation of the anions and organic acids was achieved on an IonPac AS11-HC column with KOH as the eluent, and the detection was performed by a conductivity detection mode. The calibration graphs of peak area for all the analytes were linear over a wide range. The recoveries of the added standards were 90% - 110% . The relative standard derivations (RSDs) of the peak area of analytes were less than 8.0%. The detection limits for analytes ranged from 1.55 microg/L to 31.8 microg/L.

Chromatography, Ion Exchange↗

PubMed2003

Off-line elimination of carbohydrates for amino acid analysis of samples with high carbohydrate content by ion-exchange chromatography.

This paper introduces a new off-line sample preparation that eliminates carbohydrates from amino acid samples containing a high carbohydrate content before analysis by anion-exchange chromatography and integrated pulsed amperometric detection. First, the sample is introduced into a cation-exchange column in the hydrogen form. Carbohydrates are removed completely using 0.02% formic acid as a transfer fluid, while only amino acids are retained. Amino acids are then extracted from the cation-exchange resin by 10 ml of 1 M ammonia. The ammonia collected is evaporated to dryness and the residue redissolved in water containing 20 mg/l NaN3 for injection. All amino acids are recovered following the carbohydrate removal step. The average recovery is 97.2%. The relative standard deviation for seven replicates is less than 5.2%. The usefulness of the method is illustrated with chromatograms of ratafia samples obtained before and after the off-line removal of carbohydrates.

Amino Acids↗

PubMed2003

Determination of trace levels of haloacetic acids and perchlorate in drinking water by ion chromatography with direct injection.

Disinfection by products of haloacetic acids and perchlorate pose significant health risks, even at low microg/l levels in drinking water. A new method for the simultaneous determination of nine haloacetic acids (HAAs) and perchlorate as well as some common anions in one run with ion chromatography was developed. The HAAs tested included mono-, di-, trichloroacetic acids, mono, di-, tribromoacetic acids, bromochloroacetic acid, dibromochloroacetic acid, and bromodichloroacetic acid. Two high-capacity anion-exchange columns, a carbonate-selective column and a hydroxide-selective hydrophilic one, were used for the investigation. With the carbonate-selective column, the nine HAAs as well as fluoride, chloride, nitrite, nitrate, phosphate and sulfate could be well separated and determined in one run. With the very hydrophilic column and a gradient elution of sodium hydroxide, methanol and deionized water, the nine HAAs, fluoride, chloride, nitrite, nitrate as well as perchlorate could be simultaneously determined in one run within 34 min. The detection limits for HAAs were between 1.11 and 9.32 microg/l. For perchlorate, it was 0.60 microg/l.

Acetates↗

PubMed2002

Direct determination of free amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection.

Determination of amino acids and sugars in green tea by anion-exchange chromatography with integrated pulsed amperometric detection was developed. Amino acids and sugars were separated on an anion-exchange column at a flow-rate of 0.25 ml/min by using ternary gradient elution consisting of deionized water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. Under optimized conditions, theanine was separated from glutamine and three sugars (glucose, fructose, and sucrose) were eluted earlier than the neutral amino acids to avoid their interference with each other. RSDs of the peak area of analytes were lower than 4.6%. Detection limits for the analytes ranged from 0.12 to 4.9 pmol. The linearities for all analytes were two or three orders of magnitude with the correlation coefficients greater than 0.99. This method was applied to determination of amino acids and sugars in green tea with satisfactory results.

Amino Acids↗