Rapid flow injection spectrophotometric determination of monofluorophosphates in toothpastes after on-line hydrolysis by alkaline phosphatase immobilized on a cellulose nitrate membrane

A new, rapid flow injection (FI) method is reported for the spectrophotometric determination of monofluorophosphate (MFP) ions in toothpastes. MFP ions are hydrolyzed on-line by alkalinephosphatase (APase) immobilized on a cellulose nitrate membrane, prior to injection in the FI system. The yielded orthophosphate ions are determined spectrophotometrically (lambda(max) = 690 nm) using the molybdenum blue approach. The chemical and FI variables that affected the enzymatic reaction were studied and optimized. A study of interferences was also carried out. The proposed method is very precise (s(r) = 0.7% at 1.0 x 10(-4) mol l(-1) MFP, n = 12), fast (sampling rate of 72 h(-1)) and allows the determination of MFP ions in the range of 4.0 x 10(-5) to 6.0 x 10(-4) mol l(-1) with a satisfactory 3sigma detection limit of 4.0 x 10(-6) mol l(-1). The application of the proposed FI method to toothpaste samples yielded accurate results (e(r) < 2.0%) compared with a potentiometric reference procedure.     

Spectrophotometric determination of paracetamol with microwave assisted alkaline hydrolysis

A novel and rapid spectrophotometric method for the determination of paracetamol is proposed in this paper. The proposed method is based on the microwave assisted alkaline hydrolysis of paracetamol to p-aminophenol that reacts with S2- in the presence of Fe3+ as oxidant to produce a methylene blue-like dye having an absorptivity maximum at 540 nm. The experiment showed that paracetamol could be hydrolysed quantitatively to p-aminophenol in only 1.5 min under radiation power 640 W using a microwave in NaOH medium. The system obeys Beer's law in the range of 0-3.0 x 10(-4) mol l(-1) paracetamol. The molar absorptivity and Sandell's sensitivity were found to be 3.2 x 10(-3) l mol(-1) cm(-1) and 0.047 microg cm(-2), respectively. The relative standard deviation (n=11) was 1.7% for 8.0 x 10(-5) mol l(-1) paracetamol. The method has been applied successfully to analysis of paracetamol in pharmaceutical preparation.     

Chronoamperometric determination of paracetamol using an avocado tissue (Persea americana) biosensor

A biosensor based on vaseline/graphite modified with avocado tissue (Persea americana) as the source of polyphenol oxidase was developed and used for the chronoamperometric determination of paracetamol in pharmaceutical formulations. This enzyme catalyses the oxidation of paracetamol to N-acetyl-p-benzoquinoneimine whose electrochemical reduction back to paracetamol was obtained at a potential of -0.12 V. After addition of paracetamol reference solutions in glass cell and stirring for 60 s for the accumulation of N-acetyl-p-benzoquinoneimine at the electrode surface under open-circuit conditions, the current response was monitored by 120 s without stirring. The currents obtained at 70 s were proportional to the paracetamol concentration from 1.2x10(-4) to 5.8x10(-3) mol l(-1) (r=0.9927) with a detection limit of 8.8x10(-5) mol l(-1). The recovery of paracetamol from two samples ranged from 97.9 to 100.7% and a relative standard deviation lower than 0.5% for a solution containing 5.0x10(-3) mol l(-1) paracetamol in 0.10 mol l(-1) phosphate buffer solution (pH 7.0; n=10) was obtained. The results obtained for paracetamol in pharmaceutical formulations using the proposed biosensor and those obtained using a pharmacopoeial procedure are in agreement at the 95% confidence level.     

On-line dilution flow injection manifold for the selective spectrophotometric determination of ascorbic acid based on the Fe(II)-2,2'-dipyridyl-2-pyridylhydrazone complex formation

A new simple and rapid FI method for the accurate and precise spectrophotometric determination of ascorbic acid (AsA) in pharmaceutical formulations is reported. The method is based on the reduction of Fe(III) to Fe(II) by the analyte, and the subsequent reaction of the produced Fe(II) with 2,2'-dipyridyl-2-pyridylhydrazone (DPPH) in acidic medium (pH ca. 2.5) to form a colored complex (lambda(max)=535 nm). An on-line dilution mode using a binary inlet static mixer (BISM) was incorporated in the FI system, allowing the determination of the analyte in a wide concentration range. The calibration graph was linear in the range of 5.7-600.0 mg l(-1) AsA, at a sampling rate of 120 injections h(-1). The method was found to be very precise [s(r)=0.1% at 300 mg l(-1) AsA (n=12)] and the 3delta detection limit (c(L)=1.7 mg l(-1)) was quite satisfactory. The detailed study of various interferences confirmed the high selectivity of the proposed method. Its application to a variety of pharmaceuticals produced excellent results, with a mean relative error of e(r)<1.0%.     

Renal function study with 111In-DTPA--in comparison with 99mTc-DTPA

Technetium-99m-diethylene-triamine-penta-acetic acid (DTPA) and 111In-DTPA were injected simultaneously into 21 patients with various levels of renal function. Scintiphoto, camera data renograms and clearance values (plasma sampling) were obtained for each patient. The mixed isotope scintiphoto images were of intermediate quality and the images with 111In-DTPA were apparently inferior to those with 99mTc-DTPA. These equations were obtained: (1) y = 0.30 + 0.91 x (coefficient of correlation r = 0.98) where x is the value at T peak (time of maximum count on renogram) obtained with 99mTc-DTPA and where y is the value at T peak with 111In-DTPA. (2) y = -0.09 + 1.006 x (r = 0.99) where x is the value at T3/4 (time interval between the time of maximum count to the time of 3/4 of maximum count on renogram) and where y is the value at T3/4 obtained with 111In-DTPA. (3) y = -0.01 + 1.007 x (r = 0.98) where the x and y values were for the excretion ratios (counts at 20 min/maximum counts on renogram). (4) y = 0.81 + 0.98 x (r = 0.99) where x and y are the clearance values.     

New whole blood methods and instruments: glucose measurement and test menus for critical care.

A glucose oxidase-H 2O 2 substrate-selective electrode (SSE) along with eight other electrodes allows the Stat Profile 5 (SP5) to measure glucose, electrolytes, blood gases, pH, and hematocrit simultaneously in whole blood. For heparinized blood gas syringe samples (n=178), orthogonal (Deming) regression showed y=0.43 + 1.00x (mmol/L), where y is whole blood glucose, and x is plasma glucose measured with the Ektachem 400 glucose oxidase slide method. For heparinized plasma (n=197), y=0.25 + 1.02x. Least squares linear regression showed y=0.25 + 1.00x (s yxx=0.49) for whole blood versus plasma, y = 0.30 + 1.01x (s yxx=0.49) for plasma versus plasma, and r=0.994 for both cases. Whole blood and plasma glucose in the same samples measured by SSE differed by less than 1%. The SP5 combines the largest number of whole blood tests currently available in a rapid response instrument well-suited for care of the critically ill patient.     

Ab initio study of the ClO + NH2 reaction: prediction of the total rate constant and product branching ratios

The mechanism for ClO + NH2 has been investigated by ab initio molecular orbital and transition-state theory calculations. The species involved have been optimized at the B3LYP/6-311+G(3df,2p) level and their energies have been refined by single-point calculations with the modified Gaussian-2 method, G2M(CC2). Ten stable isomers have been located and a detailed potential energy diagram is provided. The rate constants and branching ratios for the low-lying energy channel products including HCl + HNO, Cl + NH2O, and HOCl + 3NH (X(3)Sigma(-)) are calculated. The result shows that formation of HCl + HNO is dominant below 1000 K; over 1000 K, Cl + NH2O products become dominant. However, the formation of HOCl + 3NH (X(3)Sigma(-)) is unimportant below 1500 K. The pressure-independent individual and total rate constants can be expressed as k1(HCl + HNO) = 4.7 x 10(-8)(T(-1.08)) exp(-129/T), k(2)(Cl + NH2O) = 1.7 x 10(-9)(T(-0.62)) exp(-24/T), k3(HOCl + NH) = 4.8 x 10(-29)(T5.11) exp(-1035/T), and k(total) = 5.0 x 10(-9)(T(-0.67)) exp(-1.2/T), respectively, with units of cm(3) molecule(-1) s(-1), in the temperature range of 200-2500 K.     

高效液相法测定胃康片中呋喃唑酮、甘珀酸钠和盐酸小檗碱

 用高效液相 (HPLC)梯度洗脱法同时测定复方胃康片中呋喃唑酮、甘珀酸钠和盐酸小檗含量。使用No va PakC18柱 ,以乙腈和 0 0 2mol/L磷酸盐缓冲溶液 (pH 7 0 )为流动相 ,3,5 二硝基苯甲酸作为内标溶液 ,使用UV检测器 ,在 2 5 4nm处对样品中上述 3种成分进行测定。测定结果表明 ,呋喃唑酮在 14 1 2mg/L～ 12 70 8mg/L、甘珀酸钠在 10 0 6mg/L～ 90 5 4mg/L、盐酸小檗碱在 99 2mg/L～ 892 8mg/L时其相对峰面积 (标准品与内标的峰面积之比 )与进样质量浓度有良好的线性关系 ,其线性相关系数分别为r =0 9997,r =0 9995和r =0 9991。     

Monoclonal-based enzyme-linked immunosorbent assay and immunochromatographic assay for enrofloxacin in biological matrices

Enrofloxacin has been increasingly used in veterinary medicine to treat microbial infections. A simple and reliable analytical method for this drug is required. The current determination by high performance liquid chromatography (HPLC) is sensitive but labor-intensive. This paper reports an enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody (MAb) and the development of a rapid test kit based on immunochromatography. The detection limits using the ELISA were 10 ppb for chicken liver and muscle, and 1 ppb for cattle milk, respectively. The mean recovery values were 77.3-96.0% for chicken liver, 72.4-92.0% for chicken muscle and 84.0-99.0% for cattle milk. The detection limits using the kit were ca. 100 ppb for chicken muscle and ca. 10 ppb for cattle milk, respectively. All ELISA results for assay of chicken liver, chicken muscle and cattle milk were confirmed using HPLC which is used as the routine assay. The HPLC (x) and ELISA (y) results showed close correlation for chicken liver (y = 8.7 + 0.85x, r2 = 0.99, n = 25), chicken muscle (y = -3.9 + 0.94x, r2 = 0.98, n = 25) and cattle milk (y = 18.4 + 0.92x, r2 = 0.99, n = 25).     

高效液相色谱法同时测定诺诺感冒片中扑尔敏、扑热息痛、盐酸伪麻黄碱的含量

 采用反相高效液相色谱法 ,在C18柱上以V(甲醇 )∶V(水 ) =2 5∶75的溶液为流动相 (内含 0 .0 5mol/L磷酸二氢钠 ) ,检测波长为 2 0 5nm ,同时分离测定诺诺感冒片中扑尔敏、扑热息痛、盐酸伪麻黄碱的含量。扑尔敏、扑热息痛和盐酸伪麻黄碱的检出限分别为 1.16mg/L ,0 .15mg/L和 1.82mg/L ,其相应的回收率分别为 98.35 % (n =5 ,RSD =1.6 0 % ) ,10 1.16 % (n =5 ,RSD =1.5 0 % )和 98.5 0 % (n =5 ,RSD =1.5 9% )。方法简便、快速 ,重现性好 ,适用于诺诺感冒片的质量检验分析。     

Reversed flow-injection manifold for the spectrophotometric determination of captopril based on its inhibitory effect on the Co(II)-2,2'-dipyridyl-2-pyridylhydrazone complex formation

The present work reports a new, simple and rapid reversed flow-injection (r-FI) method for the accurate and precise spectrophotometric determination of captopril (CPL) in pharmaceutical formulations. The method is based on the inhibitory effect of CPL on the complex formation of Co(II) with 2,2'-dipyridyl-2-pyridylhydrazone (DPPH). The chemical and FI variables were studied and optimized. The calibration graph was linear in the range 0-250 mg l(-1) CPL, at a sampling rate of 60 injections per hour. The method was found to be very precise [s(r)=0.8% at 100.0 mg l(-1) CPL (n=12)] and the 3sigma detection limit (c(L)=2.5 mg l(-1)) was quite satisfactory. Its application to commercially available pharmaceuticals produced excellent results, with a mean relative error of e(r)<1.0%.     

二硫苏糖醇直接光度法测定钴离子含量

为建立简便、灵敏测定钴离子含量的方法,在表面活性剂存在下,用二硫苏糖醇(DTT)为显色剂测定钴离子.结果表明,该法线性范围0～6.00 mmol/L,平均回收率为99.4%,批内变异系数(CV)和批间变异系数分别为0.022、0.038,与原子吸收法比较具有良好的相关性,线性回归方程和相关系数分别为y =0.997 6...     

A simple flow injection spectrophotometric procedure for the determination of diazepam in pharmaceutical formulation.

A single-channel flow injection (FI) manifold with spectrophotometric detection has been designed and fabricated for diazepam determination. A 100 microl sample and/or standard solution containing diazepam was injected into a flowing stream of 0.1 mol L(-1) hydrochloric acid with the optimum flow rate of 6.8 mL min(-1). As soon as the sample reached the detector, the FI signal as a peak was recorded at 360 nm. The optimum conditions for microg amounts of diazepam were achieved. A linear calibration graph over the range of 2-110 mg L(-1) diazepam was obtained with the regression equation Y = 0.2926X + 0.5896 (r2 = 0.9929). The method was very sensitive, since as little as 0.60 mg L(-1) could be detected; very reproducible with an RSD of 3.3% (n=11); and very rapid with a sampling rate of 100 h(-1). The limit of quantitation (10 sigma) was 2.0 mg L(-1). The proposed FI procedure has been satisfactorily applied to the quantitation of diazepam in commercial pharmaceutical formulations. The obtained results were in excellent agreement with those obtained by the conventional spectrophotometric method, verified by the student t-test at the 95% confidence level.     

毛细管气相色谱法测定速效伤风胶囊中对乙酰氨基酚、咖啡因、马来酸氯苯那敏的含量

 用５％Ｐｈ－Ｍｅ－Ｓｉｌｉｃｏｎｅ毛细管色谱柱，ＦＩＤ，二阶程序升温，以正十六烷作为内标物测定速效伤风胶囊中对乙酰氨基酚、咖啡因、马来酸氯苯那敏的含量。浓度线性范围：对乙酰氨基酚４～２０ｇ／Ｌ，咖啡因０．０８４～０．４２ｇ／Ｌ，马来酸氯苯那敏０．１５～０．７５ｇ／Ｌ。平均回收率（ｎ＝５）：对乙酰氨基酚９９．６２％（ＲＳＤ＝０．４４％）咖啡因９６．４６％（ＲＳＤ＝１．３２％），马来酸氯苯那敏９８．５５％（ＲＳＤ＝０．６５％）。     

A homogeneous system for the photogeneration of hydrogen from water based on a platinum(II) terpyridyl acetylide chromophore and a molecular cobalt catalyst

The complex [Co(dmgH)2pyCl]2+ (1, dmgH = dimethylglyoximate, py = pridine) has been used as a molecular catalyst for visible light driven hydrogen production in the presence of [Pt(tolylterpyridine)(phenylacetylide)]+ (3) as a photosensitizer and triethanolamine (TEOA) as a sacrificial reducing agent. Complex 3 is quenched oxidatively by [Co(dmgH)pyCl]2+ (1) with a rate constant kq of 1.27 x 10(9) M(-1) s(-1). Photogeneration of H2 is only seen when 1 + 3 + TEOA are all present. H2 production is maximized for this system at pH 8.5 and declines to very low levels at pH < 7 and pH > 12. Irradiation of the reaction solution initially containing 1.61 x 10(-2) M TEOA, 1.11 x 10(-5) M of 3, and 1.99 x 10(-4) M of Co catalyst 1 in MeCN/water (3:2 v/v) at pH = 8.5 for 10 h with lambda > 410 nm yields 400 turnovers of H2. When TEOA is 0.27 M, approximately 1000 turnovers are obtained after 10 h of irradiation. Spectroscopic study of the photolyses solutions suggests that H2 formation proceeds via Co(I) and protonation to form Co(III) hydride species.     

S-nitrosocysteine and cystine from reaction of cysteine with nitrous acid. A kinetic investigation

The formation of the S-nitrosocysteine (CySNO) in aqueous solution starting from cysteine (CySH) and sodium nitrite is shown to strongly depend on the pH. Experiments conducted within the pH range 0.5-7.0 show that at pH below 3.5 the NO+ (or H2NO 2 +) is the main nitrosating species, while at higher pH (>3.5) the nitrosating species is most likely the N2O3. A kinetic study provided a general kinetic equation, V(CySNO) = k1[HNO2][CySH]eq [H+] + k2[HNO2]2. The first term of this equation is predominant at pH lower than 3.5, in agreement with the literature for the direct nitrosation of thiols with nitrous acid; the value for the third-order rate constant, k(1) = 7.9 x 10(2) L(2) mol(-2) min(-1), was calculated. For experiments at pH higher than 3.5, the second term becomes prevalent and the second-order rate constant k(2) = (3.3 +/- 0.1) x 10(3) L mol(-1) min(-1) was calculated. A competitive oxidation process leading to the direct formation of cystine (CySSCy) has been also found. Most likely also for this process two different mechanisms are involved, depending on the pH, and a general kinetic equation, V(CySSCy) = k3[CySH](eq)[HNO2][H+] + k3'[CySH]eq[HNO2], is proposed.     

Plasma antioxidant capacity determination: comparative evaluation of chemiluminescent and spectrophotometric assays

All aerobic organisms have developed different mechanisms for neutralising the free radicals, mostly produced by the monoelectronic reduction of O(2), and preventing the severe damages these can provoke. The efficiency of these mechanisms can be assessed, in different matrices, by a simple and direct chemiluminescent assay (CL) based on luminol oxidation catalysed by horseradish peroxidase. Light emission is mediated by the production of free radicals and it is inhibited after a sample addition in a way that is directly proportional to the sample total content of molecules displaying antioxidant activity. The performances of this chemiluminescent assay were compared with those of two spectrophotometric methods already applied in clinical practice. First spectrophotometric method measures, like CL assay, the total antioxidant capacity, whereas the second one determines free thiol groups content. The chemiluminescent assay has a linearity interval between 0.60 and 9.46 mumol l(-1) of Trolox (y=34.91x+3.10; r=0.999; n=5) with an imprecision, expressed as CV, of 3.8% and an inaccuracy, expressed as percentage recovery, of 109%. The first spectrophotometric method, based on the same reference standard, the Trolox molecule, has a linearity interval between 0.2 and 2.5 mmol l(-1) of Trolox (y=-0.01x+4.54; r=0.95; n=5); the thiol groups assay has a linearity interval between 0.1 and 1 mmol l(-1) of l-cysteine (y=1.68x-47.09; r=0.998; n=5). Different clinical samples of plasma from healthy individuals, obese subjects and patients with liver diseases were tested. Interesting correlations were obtained among the three methods, but no significant correlations emerged between antioxidant capacity and clinical parameters. Significant differences were there only between men and women among obese subjects and between drinkers and non-drinkers among liver disease patients.     

单扫描示波极谱法测定阿司咪唑

利用阿司咪唑与亚硝酸钠在 ０．１２ｍｏｌ／Ｌ ＨＡｃ介质中反应,其亚硝化产物于－０．７２Ｖ（ｖｓ．Ａｇ／ＡｇＣｌ）产生极谱还原波。该还原波的一阶导数峰电流与阿司咪唑浓度在 ４．０ × １０－７～ １．６ × １０－５ ｍｏｌ／Ｌ范围内呈线性关系（ ｒ＝ ０．９９９７）;检测限为 ２．０ × １０－７ｍｏｌ／Ｌ。用于片剂中阿司咪唑的测定,结果满意。     

Flow injection spectrophotometric determination of anionic surfactants using methyl orange as chromogenic reagent

A flow injection(FI) spectrophotometric method for the determination of anionic surfactants was developed on the basis of the competition for the cationic surfactant cetyl pyridine (CP+) chloride between the acidic dye methyl orange (MO) and anionic surfactants. In a pH 5.0 medium the cation of cetyl pyridine (CP+) reacts with dissociated methyl orange (MO-) to form an ion-associate complex, causing a blue shift of lambda(max) from 465 nm for MO- to 358 nm for the CP+ x MO- associate. The MO- in the ion-associate complex can be quantitatively substituted by such anionic surfactants as sodium dodecyl benzene sulfonate (DBS) or sodium lauryl sulfate (LS), leading to an increase in the absorbance measured at 465 nm. This increased absorbance value is proportional to the concentration of anionic surfactants. Various chemical and physical parameters for the FI spectrophotometric method were optimized, and interference-free levels were examined. At the optimized conditions, Beer's law was obeyed in the range 1.4 approximately 25 mg/L sodium DBS for an injected sample volume of 180 microL, and a detection limit of 0.22 mg/L for sodium DBS was achieved at a sampling rate of 90 h(-1). Eleven determinations of a 16 mg/L sodium DBS solution gave a RSD of 0.4%. The proposed method has successfully been applied to the determination of anionic surfactant concentration in waste water and in detergents.     

Determination of morphine in process streams by sequential injection analysis with chemiluminescence detection

A procedure for the determination of morphine in process streams by sequential injection analysis based on the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium hexametaphosphate is presented. The chemiluminescence emission has been monitored using an in-house detection system which consisted of a fibre optic flowthrough cell and a sensitive, low dark current, photomultiplier tube. The calibration graph (range 2 x 10(-8) to 1 x 10(-4) mol/l) was not linear over the entire range of concentration, with a polynomial equation of best fit of y = 1.0 x 10(15) x(3) - 2.2 x 10(11) x(2) + 1.3 x 10(7) x - 8.3. The calibration function approximates linearity over the concentration range 2.5 x 10(-6) to 3.0 x 10(-5) mol/l where the slope of the log-log plot is 1.09 +/- 0.16. The detection limit was estimated at about 10(-8) mol/l from the response of the lowest calibration standard (2.5 x 10(-8) mol/l) which gave a signal to noise ratio of 3 : 1. Although the structurally related codeine did not interfere significantly the results suggest that this method may be susceptible to matrix effects, dependent on the location of sampling from the process stream.