Simultaneous Determination of Procaine Penicillin G and Benzathine Penicillin G by Second Derivative Spectrophotometry

Abstract

A new method for determining the binary mixtures of procaine penicillin G and benzathine penicillin G using “zero-crossing” second derivative spectrophotometry is described. Calibration graphs were linear up to 8.80 10^?5 M for procaine penicillin G and 4.40 10^?5 M for benzathine penicillin G. The method was realized in ethanol/water medium (30 % v/v). A complete and exhaustive statistical analysis of the experimental data was realized to demonstrate the validity of method. The method was applied for determining procaine penicillin G and benzathine penicillin G synthetic mixtures with good results. The procedure does not require any separation step.     

Determination of acetaldehyde by flow injection analysis with soluble or immobilized aldehyde dehydrogenase

Acetaldehyde (0.18–7.7 × 10^?4 M) in water is determined by using a double injection technique with the soluble enzyme or with a mini-column of aldehyde dehydrogenase immobilized on cyanogen-activated Sepharose 4B. The NADH produced is monitored spectrophotometrically. The sample throughput is ca. 40 h^?1, and the immobilized enzyme is stable for at least a month. Ethanol up to 5% (v/v) does not interfere.     

Determination of Trace Manganese by Adsorption Voltammetry

Abstract

In a solution containing 0.005M borax medium (PH= 8? 10). 0.03% ascorbic acid and 0.001% gelatin, a fine sensitive adsorptive reduction peak of manganese appeared at ?1.53v (vs.SCE) on a hanging mercury electrode by fast speed scanning voltammetry. The derivative peak current is directly proportional to the concentration of manganese in the range from 1.0×10^?8M to 2.0×10^?6M. The detection limit is 3.0×10^?9M. Using this method, we have successfuly determined tracesof Mn in water and strawberry samples.     

Chemical constituents of Fumaria densiflora and the effects of some isolated spirobenzylisoquinoline alkaloids on murine isolated ileum and perfused heart

Abstract

Twenty-two alkaloids, were isolated from Fumaria densiflora. Two of these alkaloids, N-methyl-5-hydroxystylopine chloride and fumaricine N-oxide, were isolated for the first time from natural sources. Parfumine and fumaritine, in concentrations ranging from 3?×?10^?7 to 9?×?10^?4?M, caused concentration–dependent relaxation of ileum longitudinal segment. Also, parfumine and fumaritine in concentrations ranging from 3?×?10^?4 to 9?×?10^?2?M, caused concentration – dependent decrease in heart rate of the isolated perfused heart. A concentration of parfumine of 3?×?10^?2?M increased but a higher concentration (9?×?10^?2?M) decreased the amplitude of contraction of the isolated perfused heart. On the other hand, fumaritine, in concentrations ranging from 3?×?10^?4 to 3?×?10^?2?M, caused concentration – dependent increase, but a higher concentration (9?×?10^?2?M) caused a decrease in the amplitude of contraction of the isolated perfused heart.

     

Copper (II) Sensor Based on a Cephaloridine Antibiotic PVC Matrix

ABSTRACT

A poly (vinyl chloride) (PVC) based membrane of cephaloridine as a novel ionophore exhibits good potentiometric response for Cu²⁺ over a wide concentration range (10^?5-10^? M) with a slope of 28.5 mV per decade. The detection limit is 3.5 × 10^?6 M. The response time of the sensor is < 60 s. The electrode has been used for a period of one month and exhibits good selectivity towards Cu²⁺ in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb²⁺ Cd²⁺ and Fe²⁺ which are known to interfere with many other copper electrodes. The electrode can be used in the pH range from 4.0 to 6.5 and it can also be used in partially non-aqueous medium having up to 10 (v/v) non aqueous content and in the presence of cationic surfactants at concentrations less than 10^?3 M.     

Determination of some quinoxaline-N-dioxide derivatives by adsorptive stripping voltammetry

Some derivatives of quinoxaline-N-dioxides, which are used as growth promoters in animals (Carbadox, Cyadox, Olaquindox), can be determined at nanomolar concentrations by stripping volatammetry from a static mercury drop electrode after adsorptive accumulation on the electrode surface. With differential pulse voltammetry, in 0.1 M sodium perchlorate with 5% (v/v) dimethylformamide, the detection limit for Cyadox is 3 × 10^?10 mol 1^?1 after accumulation for 300 s in stirred solution; detection limits are 2 × 10^?9 mol 1^?1 (180 s accumulation) for Carbadox and 7 × 10 mol 1^?1 (60 s accumulation) for Olaquindox. The relative standard deviations are 0.85% for Cyadox (4 × 10^?9 mol 1^?1), 0.54% for Carbadox (2 × 10^?8 mol 1^?1) and 0.95% for Olaquindox (2 × 10^?8 mol 1^?1). Surfactants interfere.     

Addition of Sulfinic Acids to Methacrylic Derivatives

Abstract

The kinetics of the addition of arenesulfinic acids to methacrylic derivatives were studied. The reactions were found to be second order over a range of concentrations from 0.01 to 0.10 M. For pH values ranging from 4 to 8, the following rate constants were obtained pH the methylacrylate, chloromethylacrylate, and bromomethylacrylate with benzenesulfinic acids (278 K) were investigated: 2.37 (± 0.2).10^?4 M^?1s^?1, 2.60 (± 0.1).10^?4 M^?1s^?1, 3.15 (± 0.3).10^?4 M^?1s^?1.

GRAPHICAL ABSTRACT     

Some critical aspects in the determination of binding constants by electrospray ionisation mass spectrometry at the example of arsenic bindings to sulphur‐containing biomolecules

The influences of reactant concentrations, solvent type, acid strength, pH conditions and ionic strength on the determination of apparent gas‐phase equilibrium constants K using electrospray ionisation mass spectrometry (ESI‐MS) were elucidated. As example serves the interaction of the tripeptide glutathione (GSH) with phenylarsine oxide (PAO). It was shown that rising initial concentrations of both reactants were not adequately compensated by increasing signal intensities of the reaction products in the mass spectra. The equilibrium constant for the formation of the phenylarsenic‐substituted peptide species decreased from 1.42 × 10⁵ ± 1.81 × 10⁴ l µmol^?1 to 1.54 × 10⁴ ± 1.5 × 10³ l µmol^?1 with rising initial GSH concentrations from 1 to 10 µM at fixed PAO molarity of 50 µM . K values resulting from a series with a fixed GSH molarity of 5 µM and a PAO molarity varied from 10 to 100 µM remained in a narrower range between 4.59 × 10⁴ ± 2.15 × 10⁴ l µmol^?1 and 1.07 × 10⁴ ± 4.0 × 10³ l µmol^?1. In contrast, consumption numbers calculated from the ion intensity ratios of reaction products to the unreacted peptide were not influenced by the initial reactant concentrations. In a water–acetonitrile–acetic acid mixture (48:50:2, v:v), the consumption of 5 µ M GSH increased from 8.3 ± 1.4% to 39.6 ± 1.6% with increased molar excess of PAO from 2 to 20, respectively. The GSH consumption was considerably enhanced in a changed solvent system consisting of 25% acetonitrile and 75% 10 mM ammonium formate, pH 5.0 (v:v) up to 80% of the original peptide amount at an only threefold molar arsenic excess. Copyright © 2010 John Wiley & Sons, Ltd.     

An improved method for the spectrophotometric determination of fluoride by addition of sodium dodecyl sulphate to the fluoride/lanthanum (III)/Alizarin fluorine blue system

The conventional spectrophotometric method for the determination of fluoride, based on the fluoride/lanthanum(III)/alizarin fluorine blue ternary complex, is improved by addition of sodium dodecyl sulphate. In 15% (v/v) acetone medium, the absorbance of the binary reagent complex is decreased and the reaction time is only 3 min under sonication. Beer's Law is obeyed at 574 nm for fluoride concentrations in the ranges 0.075–0.30 and 0.20–1.2 mg 1^?1; the apparent molar absorptivities are (1.6 ± 0.1) × 10⁴ and (1.5 ± 0.1) × 10⁴ mol^?1 cm^?1 fluoride levels, respectively. This method is applied to the determination of fluoride in bottled mineral waters.     

Screening of chemiluminescent systems for the determination of some biologically important organic compounds

Screening tests are described for the development of chemiluminescence systems (oxidizing systems) capable of detecting biological organic compounds. The light emission depends strongly on the oxidizing systems employed. Acidic permanganate system gives rise to light emission for many compounds, including catechols, catecholamines, triphenols and indoles. The following oxidizing systems led specifically to chemiluminescence for hydroquinone, adrenaline or phenylpyruvic acid: 10^?1 M thiosulphate with 10^?1 M sodium hydroxide and 10^?4 M Ag (I), 0.3 % hydrogen peroxide with 10^?3 M sodium hydroxide/50% acetonitrile and 10^?4 M Fe (II), and 0.3% hydrogen peroxide with 10^?2 M sodium hydroxide/10^?2 M didodecyldimethylammonium bromide and 10^?4 M Co(II), respectively.     

Determination Of Amino Acid Based On A Series Piezoelectric Quartz Crystal Sensor

ABSTRACT

A series piezoelectric quartz crystal (SPQC) sensor has been applied to detect L-glutamic acid and L-lysine acid. The effect of formaldehyde solution on the frequency shift was studied. Two methods were discussed. For the calibration curve method, in a neutralized formaldehyde medium, the linear ranges for determining L-glutamic acid and L-lysine acid were from 7.1×10^?6M to 6.5×10^?4M and from 6.9×10^?6 M to 7.4×10^?4 M, respectively, with the detection limit being 7.1×10^?6 M and 6.9×10^?6 M, the recoveries were 99.2% and 100.1%, the R.S.D were 1.63% (n=6) and 1.83%(n=6), respectively. Frequencimetric tiration method was also described and the lowest titratable concentrations were 8.3×10^?5M and 5.5×10^?5 M, respectively.     

Effect of the ionic strength on the redox reaction of dicyanobis(bipyridine)iron(III)‐iodide in binary and ternary solvent systems

The redox reaction between dicyanobis(bipyridine)iron(III) and iodide ion follows first‐order kinetics in 10% (v/v) tertiary butyl alcohol‐water. The reaction was found first and zero order in iodide and dicyanobis(bipyridine)iron(III), respectively, at 0.06 M ionic strength and 293 ± 1 K. The thermodynamic parameters of activation such as E_A (16.07 kJ mol^?1), A (1 × 10^?4 M s^?1), ΔH^# (13.6 kJ mol^?1), ΔS^# (?329.81 J K^?1 mol^?1), and ΔG^# (90.1 kJ mol^?1) were determined. The effect of the ionic strength on the rate constant leads to recognizing the stabilization or destabilization of the transition state complex that forms during the rate‐determining step of the reaction. The value of the zero‐order rate constant was decreased with increasing ionic strength that yielded a negative value of the slope in each binary and ternary solvent systems. This negative sign refers to the electron transfer between opposite charge carriers such as [Fe^III(bpy)₂(CN)₂]⁺ and I^? during the rate‐determining step. The destabilization of the transition state complex is surfaced by the increasing slope, that is, 5 < 10 < 15% (v/v) tertiary butyl alcohol‐water with a gradual decrease in the rate constant. However, its stability emerges by relatively small values of the slope in 17.5 < 25 ≤ 30% (v/v) tertiary butyl alcohol‐water and 8:2:90 < 6:4:90% (v/v) dioxane: tertiary butyl alcohol: water with reasonably fast rate of reaction.     

Differential pulse polarographic determination of cephalexin based on the catalytic pre-wave of nickel(II)

A nickel-catalytic pre-peak at ?0.72 V vs. Ag/AgCl, is caused by cephalexin in sodium acetate (pH 8.3) medium. It is used to determine 2.4 × 10^?7–6 × 10^?6 M cephalexin; the relative standard deviation is 4% for 0.88 μg ml^?1 cephalexin. Other cephalosporins behave similarity; some amino acids can be tolerated in moderate amounts.     

A novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au³⁺ and selective colorimetric response to Cu²⁺ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10^?5?M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2?×?10^?6?M and 5?×?10^?7?M for gold and copper, respectively.     

Kinetic study of the 1,3,5-triphenyl-Δ2-pyrazoline/technetium(VII) system: Determination of Technetium

The interaction of technetium with 1,3,5-triphenyl-Δ²-pyrazoline (TPP) is examined and kinetic methods for the determination of technetium (0.01–1.2 mg l^?1) are developed; absorbances are measured at 678 nm. The optimal hydrochloric acid concentration for the reaction is 8.3 M, with a TPP concentration of 6.6 × 10^?5 M in 15 % (v/v) ethanol. Interferences by Cu(II), V(V) and Fe(III) are discussed. The method is applied to two synthetic nuclear fuels and to vegetation spiked with technetium.     

Avidin and Glucose Oxidase‐non‐covalently Functionalized Multi‐walled Carbon Nanotubes: A New Analytical Tool for Building a Bienzymatic Glucose Biosensor

We report an innovative supramolecular architecture for bienzymatic glucose biosensing based on the non‐covalently functionalization of multi‐walled carbon nanotubes (MWCNTs) with two proteins, glucose oxidase (GOx) (to recognize glucose) and avidin (to allow the specific anchoring of biotinylated horseradish peroxidase (b‐HRP)). The optimum functionalization was obtained by sonicating for 10 min 0.50 mg mL^?1 MWCNTs in a solution of 2.00 mg mL^?1 GOx+1.00 mg mL^?1avidin prepared in 50 : 50 v/v ethanol/water. The sensitivity to glucose for glassy carbon electrodes (GCE) modified with MWCNTs‐GOx‐avidin dispersion and b‐HRP (GCE/MWCNTs‐GOx‐avidin/b‐HRP), obtained from amperometric experiments performed at ?0.100 V in the presence of 5.0×10^?4 M hydroquinone, was (4.8±0.3) μA mM^?1 (r²=0.9986) and the detection limit was 1.2 μM. The reproducibility for 5 electrodes using the same MWCNTs/GOx‐avidin dispersion was 4.0 %, while the reproducibility for 3 different dispersions and 9 electrodes was 6.0 %. The GCE/MWCNT‐GOx‐avidin/b‐HRP was successfully used for the quantification of glucose in a pharmaceutical product and milk.     

Differential Pulse Voltammetric Determination of Montelukast in Tablets and Human Plasma by Using Chitosan Modified Carbon Paste Electrode

Electrochemical reduction and determination of montelukast (MKS) was studied in methanol – 0.1 M HCl solution (1 : 1, v/v) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at chitosan modified carbon paste electrode. The linear range was 1.70×10^?7–1.83×10^?5 M for DPV analysis. Limit of detection (LOD) and limit of quantification (LOQ) were 5.32×10^?8 M and 1.61×10^?7 M, respectively. The developed method was successfully applied to the determination of MKS in tablets and spiked human plasma. The results obtained were in good agreement with those obtained using a reported spectrofluorimetric technique.     

Study of iron and titanium complexes with propylenediaminetetraacetic acid by differential pulse polarography : Determination of iron and titanium in Portland cements

Differential pulse polarography is used to study the iron(III) and titanium(IV) complexes with propylenediaminetetraacetic acid (PDTA). The complexes produce reduction peaks at –0.09 V and –0.32 V (vs. Ag/AgCl/3 M KCl), respectively, at pH 4.5. This is used for a simultaneous, precise determination of iron and titanium. The detection limits in aqueous solutions were 5.0 × 10^?7 M for iron and 3.0 × 10^?7 M for titanium and linear calibrations were obtained in the range 4.0 × 10^?4–6.0 × 10^?4 M in both cases. Correct results were obtained for iron trioxide (ca. 2%) and titanium dioxide (ca. 0.3%) in Portland cements, with relative standard deviations of about 3% and 6%, respectively.     

Determination of uranium(VI) in sea water by cathodic stripping voltammetry of complexes with catechol

Polarographic (d.c.) measurements showed that complex ions of uranium(VI) with catechol adsorb on the dropping mercury electrode. This effect is used to determine uranium(VI) directly in sea water. Optimal conditions include pH 6.8, 2 × 10^?3 M catechol, and a collection potential between ?0.1 and ?0.4 V (vs. Ag/AgCl) at a hanging mercury drop electrode. The cathodic scan is made with the linear-scan or differential-pulse mode (d.p.c.s.v.). The detection limit with the d.p.c.s.v, mode is 3 × 10^?10 M after a collection period of 2.5 min. Between pH 6 and 8, the peak height increases with pH and with catechol concentration up to 5 × 10^?3 M. There is linear relationship between the collection time and the measured peak height until the drop surface becomes saturated. With a collection period of 3 min, the reduction current increases linearly with the metal concentration up to about 5 × 10^?3 M U(VI). The maximum adsorption capacity of the mercury drop is 4.4 × 10^?10 mol cm²; each complex ion then occupies 0.38 nm², equivalent to the size of about one catechol molecule. Interference by high concentrations of Fe(III) is overcome by selectively adsorbing U(VI) at a collection potential near the reduction potential of Fe(III). Organic surfactants reduce the peak height for uranium by up to 75% at unnaturally high concentrations only (4 mg l^?1 Triton X-100). Competition by high concentrations of Cu(II) for space on the surface of the drop is eliminated by addition of EDTA.     

Chemiluminescence determination of bufrenorphine hydrochloride by flow injection analysis

A direct, simple and rapid flow-injection method is described for determining buprenorphine hydrochloride (10^?8–10^?4 M) based on its chemiluminescent oxidation with potassium permanganate in polyphosphoric acid. The limit of detection is 1 × 10^?8 M (0.5 pmol per injection) and the log-log calibration is linear up to 1 × 10^?4 M; the r.s.d. is 0.7% for a 10 μg ml^?1 solution (n = 10). The method is directly applicable to aqueous solutions of tablets containing the drug (0.2 mg/tablet).