Yong-Sheng Li

Simultaneous determination of silicate and phosphate in boiler water at power plants based on series flow cells by using flow injection spectrophotometry

A new flow injection spectrophotometric method is described for the simultaneous determination of silicate and phosphate. Effects on the sensitivity of the method of the wavelength, temperature, length of reaction coils, pump rates, acidity, sampling volume, concentration of the chromogenic reagent, etc. were also investigated. The optimum conditions were ascertained. The principle of the method is that total concentration of silicate plus phosphate is determined when a injected sample plug is passing through the first flow cell and then the concentration of silicate is serially) determined at a second flow cell of the same detector after continuously masking the yellow molybdophosphate in the sample zone. Finally, the concentration of phosphate is obtained by difference. Silicate and phosphate are determined in boiler water at power plants; 60–120 samples h −1 be analyzed. Determination ranges are 0.05–22 mg l −1 for silicate and 0.1–24 mg l −1 for phosphate. Relative standard deviations for metasilicate and orthophosphate were ≤1.2 and 1.3%, respectively. Recovery ranges of silicate and phosphate in the samples are 98–103%.

Immobilized enzymatic fluorescence capillary biosensor for determination of sulfated bile acid in urine

The authors have proposed an immobilized enzymatic fluorescence capillary biosensor (SBAs-IE-FCBS) for the determination of sulfated bile acids (SBAs). The reaction principle of the biosensor is that under the catalysis of the bile acid sulfate sulfatase (BSS) and beta-hydroxysteroid dehydrogenase (beta-HSD) immobilized on inner surface of a medical capillary, SBAs desulfates to 3beta-hydroxyl bile acids, then the latter reacts with nicotinamide adenine dinucleotide (NAD(+)), and is converted into 3-ketosteroid; meanwhile, NAD(+) is converted to reduced nicotinamide adenine dinucleotide (NADH). NADH continuously reacts with 1-methoxy-5-methylphenazinium methyl sulfate (1-MPMS) and is converted into NAD(+) circularly and 1-MPMSH(2). Finally resazurin is reduced into resorufin by 1-MPMSH(2), the formed resorufin (lambda(ex)/lambda(em): 540 nm/580 nm) is used for quantifying the concentration of SBAs. Optimized conditions being suitable with the biosensor are as follows: the concentrations of BSS and beta-HSD used for the immobilization all are 5 kUL(-1); the concentrations of 1-MPMS and resazurin all are 25 micromolL(-1); the concentrations of Tris-HCl buffer and NAD(+) are 100 and 400 micromolL(-1), respectively; total volume of the enzyme, reagent and sample is only 18 microL per time for determining; the reaction temperature is 37 degrees C; the reaction time is 15min. The concentration of SBAs is directly proportional to the fluorescence intensity of the biosensor measured from 0.5 to 5.0 micromolL(-1). The relative standard deviation is less than 3.4%, and the detection limit was 0.16 micromolL(-1). The recoveries are in the range 95.5-106%. This SBA-IE-FCBS can be used for quantifying SBAs in urine to diagnose and judge hepatobiliary diseases, etc.

Determination of pyruvic acid by using enzymic fluorescence capillary analysis

A new method (P-LE-FCA) for the determination of pyruvic acid was proposed based on liquid enzyme method (LE) and fluorescence capillary analysis (FCA). The optimum experimental conditions were as follows: the excitation and emission wavelengths were 350 and 460 nm, respectively; the reaction time and temperature were 20 min and 38 degrees C, respectively; the pH of phosphate buffer solution was 7.5; the concentrations of nicotinamide adenine dinucleotide and lactate dehydrogenase were 1.0 mmol L(-1) and 5.0 k UL(-1), respectively. The linear range of this method was 0.2-1.2 mmol L(-1) (Delta F=327.13C-10.018, r=0.9942). Its detection limit was 0.012 mmol L(-1). And its relative standard deviation was 0.86%. Only 18 microL of total reaction solution is enough for the detection. P-LE-FCA has some merits such as lower cost, simple operation procedure and micro determination. It has been used for the determination of pyruvic acid content in human urine samples.

Flow injection spectrophotometric determination of sulfated bile acids in urine with immobilized enzyme reactors using water soluble tetrazolium blue-5

Abstract A simple assay of sulfated bile acid (SBA) in urine using flow injection (FI)-spectrophotometry with immobilized enzyme reactors is proposed. The system consists of an injection valve, a switch valve, two immobilized enzyme reactors and a UV–VIS detector with a flow cell. The multi-step enzymatic reactions will occur when an injected sample containing SBA passes through the immobilized enzyme reactors. First, SBA will desulfate under catalysis of immobilized bile acid sulphate sulfatase (BSS), to form 3β-hydroxyl bile acids; the produced 3β-hydroxyl bile acid reacts with nicotinamide adenine dinucleotide (NAD+) under catalysis of co-immobilized 3β-hydroxylsteroid dehydrogenase (3β-HSD), and is converted to the 3-ketosteroid. Meanwhile, β-NAD+ is converted to reduced nicotinamide adenine dinucleotide (NADH). Then by catalysis of immobilized diaphorase, NADH reacts with a novel reagent called “water soluble tetrazolium blue-5” (WST-5) to generate a blue diformazan dye, which is detected at 550xa0nm. By using FI-spectrophotometry manifold and optimized conditions, we have obtained a linear response for 1–75xa0μM glycolithocholate sulfate (GLCA-S) with a correlation coefficient of 0.999 and an analytical rate of 15xa0samples per hour. The R.S.D. was less than 1%. The recoveries (91–108%) of GLCA-S added into urine were satisfactory and the assay correlated well with the manual UBASTEC method. Therefore, it will be applicable for urine tests on patients suffering from hepatobiliary disease.

A novel immobilization multienzyme glucose fluorescence capillary biosensor

Based on the immobilization enzyme technology and the fluorescence capillary analysis method, the authors have developed a highly sensitive fluorescence reaction system and a novel immobilization multienzyme glucose fluorescence capillary biosensor for determining glucose contents. Reaction principle of the system is that under the catalysis of glucose oxidase (GOD) and horseradish peroxidase (HRP) immobilized on inner surface of a medical capillary, beta-D-glucose reacts with dissolved oxygen to form gluconic acid-delta-lactone and hydrogen peroxide, and then the latter reacts with l-tyrosine to produce a tyrosine dimer, which has maximal excitation and emission wavelengths at 320 nm and 410 nm, respectively. Fluorescence of the dimer is proportional to the concentration of the beta-D-glucose. Optimization conditions suitable for the reaction system and the biosensor were as follows. Concentration of the L-tyrosine used as fluorescence reagent was 0.15 mol L(-1), the active concentrations of the GOD and the HRP for the immobilization were 15 kU L(-1) and 8 kU L(-1), respectively. Consumptions of the sample and reagents in one determination were 5.0 microL and 15 microL, respectively. Quantitative range of the biosensor for the glucose was in the range 1-10 micromol L(-1), its relative standard deviation was less than 4.9%, and its detection limit was 0.62 micromol L(-1). The biosensors recovery was in the range 96-105%. Results of some serum determined with the biosensor and with a commercial glucose-kit were well coincident to each other. Accordingly, the biosensor can be applied to the determination of serum glucose contents in the diagnosis of diabetes.

Immobilization enzyme fluorescence capillary analysis for determination of lactic acid.

A new method for the determination of lactic acid based on the immobilization enzyme fluorescence capillary analysis (IE-FCA) was proposed. Lactic dehydrogenase (LDH) was immobilized on inner surface of a capillary with glutaraldehyde, and an immobilized enzyme lactate capillary bioreactor (IE-LCBR) was formed for the determination of lactic acid. After nicotinamide adenine dinucleotide (NAD(+)) is mixed with lactic acid solution, it was sucked into the IE-LCBR and was detected at lambda(ex) 353 nm/lambda(em) 466 nm. Optimized conditions are as follows: the temperature is 38 degrees C; the reaction time is 15 min; the concentrations of Tris buffer (pH 8.8) and NAD(+) are 0.1 mol L(-1) and 4 mmol L(-1), respectively; the concentration of LDH used for immobilization is 15 kU L(-1). The concentration of lactic acid is directly proportional to the fluorescence intensity measured from 0.50 to 2.0 mmol L(-1); and the analytical recovery of added lactic acid was 99-105%. The minimum detection limit of the method is 0.40 mmol L(-1) and sensitivity of the IE-CBR is 4.6 F mmol(-1) L(-1) lactate. Its relative standard deviation (R.S.D.) is < or =2.0%. This IE-FCA method was employed for determination of lactate in milk drink.

Zone circulating flow-injection analysis: theory

Abstract Zone circulating flow-injection analysis (ZCFIA) is a method for multi-detection of a sample zone injected into a closed-flow system formed by connecting the two ports of a single FIA manifold. Using an FIA instrument assembled with a multi-step pump, detection was carried out at various flow-rates. Subsequent analysis of the damped curves yielded a great deal of information concerning the theory of FIA. The data thus obtained were arranged to clarify correlations among general residence time, flow-rate, length and inner diameter of the reactor, sample volume injected and dispersion coefficient. As a result, several shortcomings and errors in FIA theory were discovered. Several qualitative formulations, containing variables suitable for the various conditions involved, were established and six qualitative conclusions were drawn.

A rapid and accurate method for determining protein content in dairy products based on asynchronous-injection alternating merging zone flow-injection spectrophotometry.

An accurate and rapid method and a system to determine protein content using asynchronous-injection alternating merging zone flow-injection spectrophotometry based on reaction between coomassie brilliant blue G250 (CBBG) and protein was established. Main merit of our approach is that it can avoid interferences of other nitric-compounds in samples, such as melamine and urea. Optimized conditions are as follows: Concentrations of CBBG, polyvinyl alcohol (PVA), NaCl and HCl are 150 mg/l, 30 mg/l, 0.1 mol/l and 1.0% (v/v), respectively; volumes of the sample and reagent are 150 μl and 30 μl, respectively; length of a reaction coil is 200 cm; total flow rate is 2.65 ml/min. The linear range of the method is 0.5-15 mg/l (BSA), its detection limit is 0.05 mg/l, relative standard deviation is less than 1.87% (n=11), and analytical speed is 60 samples per hour.

A novel assay for determination of sulfated bile acids in urine by use of flow-injection chemiluminescence principle with immobilized enzymes

Multistep enzymatic reactions take place when sulfated bile acids (SBAs) pass through an immobilized enzyme reactor. First, SBAs take place in the reaction of desulfation under catalytical action of a bile salt sulfatase immobilized in the reactor and formed 3β-hydroxyl bile acids. Formed 3β-hydroxyl bile acids react with nicotinamide adenine dinucleotide (β-NAD+) under catalysis of another enzyme of 3β-hydroxysteroid dehydrogenase coimmobilized in the column and are converted to 3-ketosteroid. At the same time, β-NAD+ is changed into reduced nicotinamide adenine dinucleotide (NADH). Looking as if chain reaction, 1-MPMS taken as an electron mediator reacts immediately with NADH coexisting in the carrier solution and is turned into 1-MPMSH2. Formed 1-MPMSH2 again reacts with dissolved oxygen existing in the carrier solution and produces hydrogen peroxide. Last, the hydrogen peroxide reacts with the luminol reagent and gives out light in the presence of POD. Consequently, SBA can be determined by the luminous intensity. n n n nBased on the above-mentioned principle, applying the technology of flow-injection analysis, we established an accurate, simple, less time-consuming and sensitive approach for the determination of SBAs. According to the FIA manifold and experimental results optimized in the work, a new type of analytical instrument for the clinical assay of SBAs in urine or blood can be developed. We also think this method is very useful for routine analysis in clinical laboratory and long-period monitoring to patients with acute hepatitis, liver cirrhosis, and intra- and extrahepatic biliary obstruction of the urinary tract. Sampling frequency of the method is 30 samples/h, and its relative standard deviation is smaller than 2.2%. It can be used to determine SBAs in the ranges of 0.1–2.5 or 2–25 μM.

An automatic method of on-line FIA cation-exchange pretreating and anion-exchange separating for simultaneous determination of silica and phosphate in biological materials

A flow-injection analysis (FIA) new method of a continuous ion-exchange pretreatment and separation is given for the simultaneous determination of silicate and phosphate in biological samples. To remove interfering cations, the sample solution passes through the mini cation-exchange column connected at the inlet and outlet of one of the loading loops of a two-channel valve, and it again passes through another loading loop of the valve for sampling. After the valve is switched to the inject position, the defined sample is injected and passed through the seperation column, and silicate and phosphate ions in the sample zone are separated. At the same time, the mini cation-exchange column is switched to the regeneration position and regenerated by a regenerant. By this manner, the sample pretreatment and determination can be made continuously. The approach is extendable to other anion analyses in various biological samples without matrix matching. n n n nThis article gives a description of simultaneously determining silicate and phosphate in human hair, mussel, tea leaves, sargasso, and rice flour with the flow-injection system. Regression equations of the calibration curves were Y1 = 0.7183C− − 0.0621 (r = 0.9998); Y2 = 0.4324CPO43− − 0.0963 (r = 0.9998). About 30 samples can be analyzed per hour. Determination ranges are within 0.1–10 mg/L for SiO32− and 2.0–30 mg/L for PO43−. Relative standard deviations for metasilicate and orthophosphate were less than 1.8 and 1.3%, respectively. Recovery ranges of SiO32− and PO43− in the samples are 100–107% and 97–104%, respectively. The results are in agreement with those obtained by classical procedure. Matrix effects were also investigated, and it was found that metallic cations in matrix effect positively on the simultaneous determination, and the slop of the calibration curve is increased with the increase of the kind and concentration of metallic cations. Silicate contents in mussel, tea leaves, and sargasso are reported in the present work for the first time.