Method of Standard Addition with Partial Sample Consumption

Abstract

A certain volume, 2S, of sample solution is withdrawn and used up to obtain the scale reading, R. A volume, S. containing Q ml standard of concentration W is added to the remainder of the sample solution and the process repeated several times. A plot of R versus number of steps is produced and the straight line extrapolated to give the zero intercept at the X-axis. This (negative) value, P, and the data above are used to calculate the concentration, C, of the sought-for substance in the sample from: C = (PQW)/(PS?V+S). The graph yields a straight line only when the volume withdrawn is twice that replaced. A computer program is given for obtaining the best fitting line via least square approximation and performing the calculations to print out the result.     

Simultaneous Determination of CGS 10787B and Its Major Metabolite (CGS 12094) in Plasma by High Performance Liquid Chromatography

Abstract

A method for the simultaneous determination of CGS 10787B and its major, metabolite (CGS 12094) in plasma is described. The two compounds, and the internal standard (dichlorinated analog), are extracted from acidified plasma with ethyl acetate, taken to dryness, and reconstituted in chromatographic mobile phase. The analytes are determined automatically by high performance liquid chromatography in the reversed-phase mode as paired ions, using [N(Bu)₄]⁺ as the counterion. The separation of the compounds is achieved on a 3u C-8 column, with detection at 254 nm.

Recovery and reproducibility assessments indicate good accuracy and precision over the range of 1.0 to 250 ug/ml for CGS 10787B and 1.0 to 100 ug/ml for CGS 12094.

The method has a limit of detection of 0.2 ug/ml for both compounds, and has been shown to be adequate for studying the disposition kinetics of CGS 10787B.     

Multiwavelength Spectrophotometric Determination of Acid Dissociation Constants. Deconvolution of Binary Mixtures of Ionizable Compounds

ABSTRACT

A spectral deconvolution method based on target factor analysis has been developed to determine pK_a values of binary mixtures of monoprotic and/or diprotic ionizable compounds. The technique makes use of the approach of Frans and Harris, which has been implemented previously for mixtures of monoprotic compounds (Anal. Chem. 1985, 57, 1718-1721), to extract the unknown pK_a values. The method has been illustrated by using the multiwavelength spectrophotometrictitation data of binary mixtures of: I. benzoic acid and phenol, 2. benzoic acid and nicotinic acid, 3. p-aminosalicylic acid and phthalic acid. It was demonstrated that the pK_a values as determined in this study are in good agreement with the literature.     

Spectrochemical Determination of Some Elements in Zinc Samples Using Glow Discharge Lamp

Abstract

Results in spectrochemical analysis with optical emission spectroscopy(OES) are affected by matrix. Analysis of zinc samples are difficult with other emission excitation sources as arc and spark, since zinc is a volatile element. For this reason, metallic zinc samples and its low alloys were analysed by using a glow discharge lamp in this work. Interelement effects were also investigated in the determination of Al, Cu and Mg in the samples.     

A Jet Ring Cell with a Renewable Solid Support for Amperometric Detection of Glucose in a Sequential Injection Analysis System

Abstract

A new amperometric method for the detection of glucose has been developed. A jet ring cell with a renewable solid support (JRR) is connected to a sequential injection analysis (SIA) system. The solid support, consisting of small spherical particles of agarose gel, with a mean bead size of 90 μm, is coupled with the enzyme glucose oxidase (GOD). The suspension is injected through a multiport valve in the SIA-system and is trapped in the JRR cell by a gap of 10 μm between the glassy carbon (GC) working electrode and a stainless steel counter electrode. The subsequent injection of glucose results in formation of hydrogen peroxide, which is detected by oxidation at 1.0 V (vs. Ag/AgCl/KCl (3 M)). Thereafter the suspension is removed by reversing the pump flow and subsequently replaced with fresh suspension for the next determination of glucose. The linear working range for the JRR-sensor, at this stage of the work, is 100 μM - 5 mM.     

First-Derivative Spectrophotometric Determination of a Mixture of Pirbuterol Hydrochloride and Butorphanol Tartrate

Abstract

Vierordt's method, its modified version and the first derivative method have been applied for the simultaneous determination of butorphanol tartrate and pirbuterol hydrochloride in laboratory mixtures of authemtic and dosage forms. The first derivative spectrophotometric method yields accurate and reprodeucible results for both drugs. Mean percent recoveries for butorphanol tartrate and pirbuterol hydrochloride in dosage forms were 100.54±0.84 and 100.42±1.27, respectively. Virrordt's method and its modified version have given unreliable results; the reasons behind have been discussed.     

Analysis of Thermal Decomposition Patterns of Aromatic and Heteroaromatic Amino Acids

Abstract

Differential enthalpic analysis of the thermal degradation of aromatic and heteroaromatic amino acids provides thermograms which are characteristic of specific amino acids (e.g. phenylalanine, tyrosine, tryptophan or histidine). Curve resolution of the resulting thermograms suggests that a minimum of three reactions are involved in the degradation (within the temperature limits of 500–620 [ddot]K) and provides T_M values for each of these concurrent reactions.     

Flow Injection Spectrofluorimetric Determination of Terbium (III) Based on Solubilizing its Ternary Complex in Micellar Solution

Abstract

A flow injection spectrofluorimetric method has been developed for the determination of terbium (III) based on solubilizing its ternary complex with pi valoyitrifluoroacetone (PTA) and trioctylphosphine oxide(TOPO) in micellar solution of nona (oxyethylene) dodecyl ether (BL-9EX). Accuracy and reproducibility are good up to 16 ng/ml of terbium (III) and 80 samples per hour can be analyzed. The relative standard deviation was less than 1.0 %. No interferences from 20-fold excesses of 11 rare earth ions were observed.     

High Performance Liquid Chromatographic Assay of Phenacemide in Tablets

Abstract

A rapid, specific and reliable high-performance liquid chromatographic assay of phenacemide in tablets has been developed. Reversed-phase chromatography was conducted using a mobile phase of acetonitrile and acetate buffer, pH 4.2 (50% V/V) and detection at 254 nm. The recovery and coefficient of variation from six placebo samples of 100 mg were 100.2% and 0.57%, respectively. The percent recovery of 10 replicate commercial tablets was 101.1% of the label amount and its coefficient of variation was 0.95%. Regression analyses of three standard plots in the concentration range of 15-150 μ g/ml obtained on three different days gave a correlation coefficient > 0.999 and the coefficient of variation for their slopes <2%. The HPLC method is rapid as it takes - 1 hour to analyze six commercial tablets compared with 6 hours consumed by the USP method. The assay was precise within day and between days as indicated by ANOVA test.     

Gas Liquid Chromatographic Determination of Caffeine in Breast Milk and Blood Plasma

Abstract

An improved procedure for the determination of caffeine in the presence of bupivicaine (internal standard) using gas liquid chromatography with nitrogen phosphorous detection is described. The method is based on the extraction of caffeine from plasma with a mixture of chloroform and isopropanol (95:5). The chloroform and isopropanol mixture is evaporated to dryness and the residue dissolved in 500 μl of ethyl acetate. One to 2 μl samples are injected directly into the gas chromatograph. This extraction process doesn't give rise to troublesome interfering peaks in the chromatogram. The recovery of caffeine from plasma and breast milk is approximately 99.7% and 94.1% respectively. The coefficient variation of the assay from plasma and breast milk is 2.90% and 1.18% respectively. The limit of quantitation is 0.05 mcg/ml of plasma or breast milk. Data are presented to illustrate the practicality of the method for bioavailability and pharmacokinetic evaluation of caffeine plasma and breast milk levels after oral administration of 100 mg of caffeine to lactating mothers.