灿烂甲酚蓝体系分光光度法测定肌苷

在pH=6.9的BR缓冲体系中,灿烂甲酚蓝与肌苷反应,形成离子缔合物,溶液颜色发生改变。其最大褪色波长位于630 nm处,在褪色波长处,肌苷的浓度与溶液的褪色呈良好的线性关系,可用于肌苷的测定。 肌苷的浓度在0.18×10-6~6.0×10-6 g/mL范围内符合比尔定律,相关系数r=0.999 3,摩尔吸光系数为1.13×104 L/(mol·cm),检出限为53.5×10-9 g/mL。 方法简便、准确、灵敏,可用于片剂中肌苷的测定。     

A highly sensitive spectrophotometric determination of platinum(IV) using leuco xylene cyanol FF

A new, simple, highly sensitive and rapid spectrophotometric method has been described for the determination of platinum(IV). The method is based on the oxidation of leuco xylene cyanol FF (LXCFF) to its blue form of xylene cyanol FF by platinum(IV) in sulfuric acid medium (pH 1.0-2.5), the formed dye shows an absorption maximum at 620 nm in acetate buffer medium (pH 3.0-4.5). The method obeys Beer's law over a concentration range of 0.3 to 2.6 micro g mL(-1) platinum, having molar absorptivity and Sandell's sensitivity of 5.1x10(4) L mol(-)(1) cm(-1) and 0.0038 micro g cm(-2), respectively. The optimum reaction conditions and other analytical parameters have been evaluated. The developed method has been successfully applied to the determination of platinum in pharmaceutical preparations, soil, natural water, plant material, platinum-containing catalyst, and synthetic alloy samples.     

Direct ATR-FTIR determination of sucrose in beet root

A simple and fast procedure has been developed for the direct determination of sucrose in beet root samples through attenuated total reflectance Fourier transform infrared absorbance measurements (ATR-FTIR) at 1056 cm(-1) with a baseline established between 1187 and 887 cm(-1). The method only requires a previous crushing or liquefaction of samples and it is free from matrix effects and from the interference of minoritary sugars and fermentation molecules. Aqueous solutions of sucrose can be used as standards and recovery values from 101 to 103% were found for spiked concentration levels from 3.5 to 10.5% (w/w). The limit of detection provided by this method corresponds to 0.15% (w/w) of sucrose and the standard deviation of three independent analysis of a sample containing 9.30% (w/w) was 0.03% (w/w).     

Towards minimization of chlorinated solvents consume in Fourier transform infrared spectroscopy determination of Propamocarb in pesticide formulations

A method has been developed for Fourier transform infrared (FTIR) spectroscopy determination of Propamocarb in emulsifiable pesticide concentrate formulations. Five microliter sample was directly injected without any pretreatment in a CHCl3 stream at 2 mL min(-1) into a closed system and the FTIR spectra of sample and standard solutions were obtained using a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) spectral region and accumulating 2 scans per spectrum. Propamocarb determination was based on the measurement of flow injection analysis (FIA) recording height established from FTIR peak area measurements from 1713 to 1703 cm(-1) corrected using a baseline defined at 2000 cm(-1). The concentration of Propamocarb in samples was calculated by interpolation in an external calibration line obtained from several injections of 2 microL of a 47% (w/v) standard solution into the CHCl3 closed system. This procedure provided a limit of detection of 0.8% (w/v) in the original sample, a sensitivity of 0.3190 absorbance units mL mg(-1) for a path length of 0.11 mm and a relative standard deviation of 0.2% for five independent measurements at 0.74 mg mL(-1) concentration level. The maximum sampling frequency of the whole procedure was 34 h(-1) and the waste generation was reduced to only 2 mL of CHCl3 solution per sample and additional 2 mL for the whole calibration line.     

A rapid gel electrophoretic chip for serum cholesterol determination

We present a rapid gel electrophoretic chip, composed of 2.5% (w/v) acrylamide and 1% (w/v) agarose gel, for serum cholesterol determination using a photo lithography technique. After optimizations, we determined the lipoprotein concentration of standard serum using a conventional enzyme method. The serum was diluted, stained and loaded for 15 min onto the chip. After loading, the intensities of low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) bands separated at the chip were estimated using an image analyzer. The intensities of these bands corresponded to concentrations obtained from a standard enzyme-based method. The detected LDL-C and HDL-C concentrations were linear up to 146 mg dL(-1) and 53 mg dL(-1) respectively. Finally, we carried out the cholesterol analysis using real biological samples obtained from nine volunteers using our electrophoretic chip. The LDL-C and HDL-C levels detected using our chip correlated well with the results obtained using the conventional enzyme-based method r(2) = 0.98 and r(2) = 0.86 for LDL-C and HDL-C, respectively. Although our sample size is small and confined only to health volunteers, we have demonstrated that this proof-of-concept gel electrophoretic chip can determine lipoproteins, simultaneously.     

Copper(II)-catalysed oxidative coupling reaction of 3-hydroxyacetanilide with 3-methyl-2-benzothiazolinone hydrazone for the spectrophotometric determination of traces of copper(II)

A spectrophotometric method is developed for the determination of traces of copper(II), based on the catalytic oxidative coupling reaction of 3-hydroxyacetanilide with 3-methyl-2-benzothiazolinone hydrazone in the presence of ammonia and hydrochloric acid. Beer's law is obeyed in the copper(II) concentration range of 0.008-0.16 microg mL(-1), and the molar absorptivity at 530 nm is 2.5x10(5) L mol(-1) cm(-1). The Sandell's sensitivity of the product is 0.000254 microg cm(-2). The optimum reaction conditions and other important analytical parameters have been investigated. The proposed method is applied to the analysis of water and soil samples and the results are compared with the literature method.     

Simultaneous determination of N-butylscopolamine and oxazepam in pharmaceutical formulations by first-order digital derivative spectrophotometry

A simple method has been developed for the simultaneous determination of N-butylscopolamine bromide and oxazepam in pharmaceutical formulations using first-order digital derivative spectrophotometry. Acetonitrile was selected as the solvent in which both compounds showed well-defined bands. Both analytes showed good stability in this solvent when solutions of the analytes were exposed to light and temperatures between 20 degrees and 80 degrees C. The simultaneous determination of both drugs was performed by the zero-crossing method at 226.0 and 257.0 nm for N-butylscopolamine and oxazepam, respectively. The linear range of determination was found to be 2.5 x 10(-7) to 8.0 x 10(-5) mol/L for N-butylscopolamine and 7.1 x 10(-8) to 8.0 x 10(-5) mol/L for oxazepam. A very good level of repeatability (relative standard deviation) of 0.2% was observed for N-butylscopolamine and oxazepam. The ingredients commonly found in pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in pharmaceutical formulations (capsules).     

Enzyme sensors for determination of fish freshness

A simple and rapid procedure for the determination of fish freshness was developed and applied to the determination of the K(1) parameter (freshness indicator): K(1) = ([HXR] + [HX])/([IMP] + [HXR] + [HX]) x 100, where [IMP], [HXR] and [HX] are inosine monophosphate, inosine and hypoxanthine concentrations, respectively. A platinum electrode is used to detect hydrogen peroxide produced by the enzymatic reaction catalysed by xanthine oxidase immobilised on the electrode surface. The determination of inosine and inosine monophosphate was performed by the addition of nucleoside phosphorylase, 5'-nucleotidase or alkaline phosphatase to the buffer solution. Parameters such as type of buffer, amount of enzymes and sample treatment were optimised. With this procedure a linear response was obtained in the concentration range 1 x 10(-6)-2 x 10(-5)mol 1(-1) for hypoxanthine, inosine and inosine monophosphate. The detection limit was 5 x 10(-7) mol 1(-1).     

Bismuth modified carbon-based electrodes for the determination of selected neonicotinoid insecticides

Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE) and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV) mode was applied to determine clothianidin in the concentration range from 2.5 to 23 μg cm?3 with a relative standard deviation (RSD) not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs), bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 μg cm?3 with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.     

Capillary electrophoresis of high-molecular chitosan: the natural carbohydrate biopolymer

Due to its high resolving power and diverse application range, capillary electrophoresis (CE) has been successfully applied to the analysis of carbohydrates. In this paper, a method for the determination of high-molecular chitosan (Mr 200,000) using CE is presented. We studied the optimal condition of buffer pH and type, and column type for determination of chitosan. Optimal CE performance was found when employing 100 mM triethylamine (TEA)-phosphate buffer, pH 2.0 and untreated fused-silica capillary (50 microm x 27 cm) for the chitosan analysis. Under optimum conditions, excellent linear responses were obtained in the concentration range of 1.25-20 microM, with a linear correlation coefficient of 0.9983. The standard deviations of the migration time and peak area were found to be 2.5 and 6.4%, respectively. This method could be readily applied to chitosan determination in real biological samples and commercial products.     

Spectrophotometric and potentiometric determination of piroxicam and tenoxicam in pharmaceutical preparations

Two simple and accurate methods are described for the determination of piroxicam and tenoxicam in their pharmaceutical preparations. The spectrophotometric method involves the oxidation of these drugs with potassium iodate in acid medium with the liberation of iodine and subsequent extraction with cyclohexane followed by measuring the absorbance at lambda=522 nm. Beer's law is obeyed in the concentration range of 0.05-1.1 and 0.05-0.6 mg x ml(-1) for piroxicam and tenoxicam, respectively. The apparent molar absorptivities of the resulting coloured products are found to be 2.7 x 10(3) and 2.5 x 10(3) l mol(-1) x cm(-1), whereas Sandell sensitivities are 0.012 and 0.013 g x cm(-2) for piroxicam and tenoxicam, respectively. The potentiometric method involves the direct titration of both drugs with N-bromosuccinimide in acid medium and the end point is determined potentiometrically using platinum indicator electrode. Piroxicam and tenoxicam can be determined quantitatively in the concentration range of 0.33-3.37 and 0.33-4.08 mg x ml(-1) for tenoxicam and piroxicam, respectively. The standard deviation and relative standard deviation values are found to be ranged from 0.05-0.07 and 0.37-0.98% and 0.025-0.078 and 0.25-1.2% for tenoxicam and piroxicam, respectively. The two methods are accurate within +/-1.0%. Optimum conditions affecting both methods are studied. The proposed methods are applied for the determination of the drugs in pure form and in commercial pharmaceutical preparations.     

Simultaneous determination of adenosine and inosine using single-wall carbon nanotubes modified pyrolytic graphite electrode

Voltammetric determination of adenosine and inosine has been carried out at single-wall carbon nanotubes (SWNTs) modified pyrolytic graphite electrode (PGE) at pH 7.2 using Osteryoung square wave voltammetry (OSWV). The modified electrode exhibits remarkable electrocatalytic properties towards adenosine and inosine oxidation with a peak potential of approximately 1229 mV and 1348 mV, respectively. Linear calibration curves are obtained over the concentration range 0.5 microM to 1.0 mM in adenosine and 10 microM to 1.0 mM in inosine with sensitivity of 1.0 microA microM(-1) and 1.9 microA microM(-1) for adenosine and inosine respectively. The limit of detection for adenosine and inosine was found to be 0.51x10(-7) M and 2.04x10(-7) M, respectively. The proposed method was also used to estimate these compounds in human blood plasma and urine samples and the method was validated using HPLC.     

Solvent extraction-spectrophotometric determination of phosphate with molybdate and malachite green in river water and sea-water

Molybdophosphate, formed between orthophosphate and molybdate in sulphuric acid solution, is extracted into a mixture of toluene and 4-methylpentan-2-one (1:3 v v ) with Malachite Green as counter-ion. A single extraction with equal phase volumes gives an apparent molar absorptivity for phosphate of 2.3 x 10(5) l.mole(-1).cm(-1) at 630 nm; the absorbance of the reagent blank is 0.03. With an organic to aqueous phase-volume ratio of 1:10, the molar absorptivity is 2.5 x 10(5) l.mole(-1).cm(-1) and the absorbance of the reagent blank 0.08. By the proposed method, ng ml levels of phosphorus can be determined, and the detection limit is about 0.1 ng ml . The standard deviation and relative standard deviation for the determination of phosphorus in tap water (4.3 ng ml ) are 0.05 ng ml and 1.1%, respectively. The method can also be applied to the determination of phosphorus in river water and sea-water.     

Photometric assay of 1-naphthylamine by azo dye formation with diazotized sulfisomidine - application to waters

A simple and sensitive photometric method for the trace determination of 1-naphthylamine has been worked out. The method is based on the coupling reaction of the determinand in acidic medium with diazotized sulfisomidine, to form a purplish violet water-soluble mono azo dye that shows maximum absorption at 540 nm with a molar absorptivity of 4.47 x 10(4) l mol(-1) cm(-1). Beer's law is obeyed over the concentration range 5-70 mug of 1-naphthylamine in a final volume of 25 ml, i.e. 0.2-2.8 p.p.m. with a relative error of -0.7 to +1.7% and a relative standard deviation of 0.35-4.2%, depending on the concentration level. Moreover, the method does not require either temperature control or solvent extraction. Interferences due to foreign species have been examined. The developed method has been applied to the determination of 1-naphthylamine in river water and sea water.     

A simple and rapid spectrophotometric determination of thallium(III) with trifluoperazine hydrochloride.

A simple, sensitive and rapid spectrophotometric method was developed for the determination of thallium(III) using trifluoperazine hydrochloride (TFPH). The method is based on the oxidation of TFPH by thallium(III) in a phosphoric acid medium to form a red-colored radical cation with an absorption maximum at 505 nm. Beer's law is valid over the concentration range of 0.5 - 6.5 microg ml(-1) of thallium(III). The molar absorptivity and Sandell's sensitivity of the color system are 2.14 x 10(4) l mol(-1) cm(-1) and 0.0095 microg cm(-2), respectively. The optimum reaction conditions and other analytical parameters were evaluated. The tolerance limit of the method towards various ions usually associated with thallium has been studied. The proposed method has been successfully applied to the analysis of thallium in alloys, minerals, standard reference material, water, and urine samples.     

Separation and analysis of glycyrrhizin, 18beta-glycyrrhetic acid and 18alpha-glycyrrhetic acid in liquorice roots by means of capillary zone electrophoresis

Glycyrrhizin is the main active compound of Glycyrrhiza glabra root extracts; according to recent studies, glycyrrhizin and its aglycon, glycyrrhetic acid, have interesting therapeutic properties. A new capillary electrophoretic method has been developed for the separation and quantification of glycyrrhizin, beta-glycyrrhetic acid and its isomer a-glycyrrhetic acid. Separation of the analytes was achieved in less than 3 min on a fused silica capillary, by injecting the samples at the short end of the capillary (effective length: 8.5 cm). The background electrolyte was composed of pH 10.0 carbonate buffer, methanol and ethylene glycol (80/10/10) and contained 0.4% beta-cyclodextrin; indomethacin was used as the internal standard. Diode array detection was used, with quantitative assays carried out at 254 nm. Linearity was found over the 5-200 and 2.5-100 microg mL(-1) concentration ranges for glycyrrhizin and glycyrrhetic acid, respectively. This method has been applied to the determination of the analytes in different matrices (liquorice roots and commercial confectionery products), and to the purity control of beta-glycyrrhetic acid obtained from the hydrolysis of glycyrrhizin. When analysing beta-glycyrrhetic acid and its epimer in roots, the samples were purified by means of a suitable solid-phase extraction (SPE) procedure with Oasis HLB cartridges, which granted good selectivity, eliminating matrix interference.     

Impurity profiling of dexamphetamine sulfate by cyclodextrin‐modified microemulsion electrokinetic chromatography

A CD‐modified microemulsion electrokinetic chromatography method has been developed and validated for dexamphetamine sulfate which allows the simultaneous determination of charged and uncharged impurities of the drug including the levorotary (R)‐enantiomer. The optimized background electrolyte consisted of 1.5% w/w SDS, 0.5% w/w ethyl acetate, 3.5% w/w 1‐butanol, 2.5% w/w 2‐propanol and 92% w/w 50 mM sodium phosphate buffer, pH 3.0, containing 5.5% w/w sulfated β‐CD. Separations were performed in a 50.2/40 cm, 50 μm id fused silica capillary at a temperature of 20°C and an applied voltage of ?14 kV. Carbamazepine was used as internal standard. The assay was validated in the range of 0.1–1.0% for the related substances and 0.1–5.0% for levoamphetamine based on a concentration of 3 mg/mL of dexamphetamine sulfate. The LOD of all analytes ranged between 0.05 and 0.2%. In commercial samples of dexamphetamine sulfate, levoamphetamine was found at concentrations between 3.2 and 3.8%, whereas none of the other impurities could be detected.     

Selective determination of orthophosphate and total inorganic phosphates in detergents by flow injection photometric method

A flow injection photometric system was developed for the determination of orthophosphate and total inorganic phosphates in detergents. While orthophosphate was directly determined in the presence of other phosphates by utilizing the kinetic discrimination of flow injection analysis, total inorganic phosphates was analyzed after on-line hydrolysis of polyphosphates in 2.5 mol l(-1) sulfuric acid for 50 s under 145 degrees C. Sodium dodecyl sulfate (SDS) was added to mask the interference of non-ionic surfactants. The detection limits and the sampling rates were 2.5 mg l(-1) P(2)O(5) and 40 h(-1) for total inorganic phosphates, and 1.0 mg l(-1) P(2)O(5) and 80 h(-1) for orthophosphate determination. The proposed method was applied to analyze orthophosphate and total inorganic phosphates in washing powders. The experimental results are in good agreement with those obtained by the Chinese national standard methods.     

A novel chemiluminescent method for the determination of salicylic acid in bactericidal solutions

A new flow-injection procedure has been developed for the determination of salicylic acid based on the enhancement of the chemiluminescence from the cerium(IV)-Tween 20 reaction by salicylic acid in acidic medium. The method is simple, selective and sensitive with a detection limit of 2.5x10(-9) g mL(-1). It is applicable to the determination of salicylic acid in the concentration range of 4.0x10(-9)-1.1x10(-6) g mL(-1). The relative standard deviation (RSD) is 0.85% for 4.0x10(-7) g mL(-1) salicylic acid (n=11). The method has been successfully applied to the determination of salicylic acid in bactericidal solutions. Furthermore, it is suggested that light emission from cerium(IV)-Tween 20 reaction is probably because of the formation of singlet oxygen 1O2* and the emitter is excited oxygen molecular pairs O2(1delta(g))O2(1sigma(g)-).     

Development of an reliable analytical method for synergistic extractive spectrophotometric determination of cobalt(II) from alloys and nano composite samples by using chromogenic chelating ligand

A synergistic simple and selective spectrophotometric method was developed for the determination of cobalt(II) with 1-(2',4'-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2',4'-dinitro APTPT] as a chromogenic reagent. The proposed method has been described on the basis of synergistic effective extraction of cobalt(II) in presence of pyridine at pH range 9.5-10.2, showed orange-red coloured ternary complex having molar ratio 1:2:2 (M:L:Py). The equilibrium time is 10 min for extraction of cobalt(III) from organic phase. The absorbance of coloured organic layer in chloroform is measured spectrophotometrically at 490 nm against reagent blank. The Beer's law was obeyed in the concentration range 2.5-15 μg mL(-1) of cobalt(II) and optimum concentration range was 5-12.5 μg mL(-1) of cobalt(II) and it was evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT-pyridine complex in chloroform are 1.109×10(3) L mol(-1) cm(-1) and 0.053 μg cm(-2), respectively while molar absorptivity and Sandell's sensitivity of cobalt(II)-2',4'-dinitro APTPT complex in chloroform are 6.22×10(2) L mol(-1) cm(-1) and 0.096 μg cm(-2), respectively. The composition of cobalt(II)-2',4'-dinitro APTPT-pyridine complex (1:2:2) was established by slope ratio method, mole ratio method and Job's method of continuous variation. The ternary complex was stable for more than 48 h. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The method is successfully applied for the determination of cobalt(II) in binary, synthetic mixtures and real samples. A repetition of the method was checked by finding relative standard deviation (R.S.D.) for n=5 which was 0.15%. The reliability of the method is confirmed by comparison of experimental results with atomic absorption spectrophotometer.