Standard Addition Technique Research Articles

Determination of bromide in aqueous solutions via the TlBr molecule using high-resolution continuum source graphite furnace molecular absorption spectrometry

The paper describes the determination of bromide by evaluating the molecular absorption of thallium mono-bromide (TlBr) at the rotational line at 342.9815nm by making use a high-resolution continuum source graphite furnace atomic absorption spectrometer. The effects of variables such as the wavelength, graphite furnace program, amount of Tl and the use of a modifier were investigated and optimized. Various chemical modifiers have been studied, such as Pd, Mg, Ag and a mixture of Pd/Mg. It was found that best results were obtained by using Ag which prevents losses of bromide during pyrolysis step through precipitation of bromide as AgBr. In this way, a maximum pyrolysis temperature of 400°C could be used. The optimum molecule forming temperature was found to be 900°C. Bromide concentrations in various water samples (CRM, bottled drinking water and tap water) were determined. The quantification was made by both linear calibration and standard addition techniques. The results were matched well those of the reference method. The calibration curve was linear in the range between 1 and 1000ng Br with a correlation coefficient R=0.999. The limit of detection and characteristic mass of the method were 0.3ng and 4.4ng of Br.

Hypoglycemic Agents: Micro-Determination by Highly Sensitive and Validated Spectrophotometric Techniques

The objectives of our present study is to analyse the hypoglycemic agents, Linagliptin (LNG) and Alogliptin (ALG) in pure and bulk forms by simple, reproducible and highly sensitive spectrophotometric assays with detection at 530 (method A) and 520 nm (method B). The methods developed are based on the bleaching of above drugs with known excess of bromine. The unreacted bromine is determined based on its ability to bleach the dye Eriochrome blue black R (method A) and methyl red (method B) quantitatively at 530 (method A) and 520 nm (method B) for both the drugs obeying Beer’s law in the range, 0.0-10.0 and 0.0-8.0 μg ml-1 in both the methods A and B for LNG and ALG, respectively. The values of molar absorptivity were found to be 1.53 × 104 and 2.51 × 104 l mol-1 cm-1 in method A and 1.64 × 104 and 2.82 × 104 l mol-1 cm-1 in method B, respectively with the corresponding Sandell’s sensitivity values 0.0217 and 0.0188 μg cm-2 in method A and 0.0207 and 0.0167 μg cm-2 in method B. According to the current ICH guidelines, various validation parameters of proposed techniques were confirmed by applying the standard addition technique and the results were evaluated in terms of Student’s t-test and variance ratio F-test to find out the significance of proposed methods over the earlier reported methods.

Development and application of molecularly imprinted polymer – Mn-doped ZnS quantum dot fluorescent optosensing for cocaine screening in oral fluid and serum

A molecularly imprinted polymer – Mn-doped ZnS quantum dot-based fluorescence probe for cocaine abuse screening has been prepared and applied to complex samples such as serum and oral fluid. The fluorescent sensing material was prepared by anchoring a selective MIP for COC on the surface of polyethylene glycol (PEG) modified Mn-doped ZnS quantum dots (QDs). Simple and low cost methods have thus been optimized for assessing cocaine abuse in serum and oral fluid by monitoring fluorescence quenching when cocaine (COC) is present (optimized operating conditions with 1.5mL of 200mgL-1 MIP-coated QDs solution, pH 5.5, and 15min before fluorescence scanning). The matrix effect was found to be important when analyzing oral fluid and serum, and several strategies based on centrifugation for oral fluid and solid phase extraction (SPE) for serum were explored. Two analytical methods were developed for oral fluid. The first one (direct method) requires a centrifugation step (6°C, 4000rpm, 20min) to avoid the matrix effect, and allows for cocaine determination by using an aqueous calibration (1:20 dilution). The second method was developed for oral fluid sampled by Salivette devices, and also requires a further centrifugation (6°C, 4000rpm, 20min) of the recovered oral fluid. This method, however, requires the standard addition technique (1:20 dilution) because of the existence of the matrix effect. Regarding serum samples, a direct method (serum dilution) was not possible, and an SPE procedure was needed to avoid the matrix effect (use of aqueous calibration). The limits of detection and quantification when using the Salivette method were 0.035mgL-1and 0.117mgL-1, respectively; whereas, 0.015mgL-1 (LOD) and 0.050mgL-1 (LOQ) were obtained for serum.

Optimization of Headspace Solid-Phase Microextraction and Gas Chromatography Coupled with Mass Spectrometry Technique for the Quantification of Volatile Compounds in a Fresh Cheese (Oaxaca)

The Head Space Solid Phase Microextraction Method (HS-SPME), coupled with Gas Chromatography and Mass Spectrometry (GC-MS) was optimized to quantify Volatile Organic Compounds (VOC’s) in a fresh Oaxaca cheese during its shelf life of 22 days. Optimal extraction conditions were ascertained by means of a multiple linear regression analysis and the generation of a response surface. Conditions to reach the equilibrium of VOC’s at the headspace were established to be 30 minutes of ultrasonic agitation at 50°C. The conditions for extraction were exposure of the fiber at room temperature for 30 minutes. Optimal extraction of volatile compounds released by the Oaxaca cheese allowed identification of 21 volatile compounds: 8 acids, 1 alcohol, 4 aldehydes, 4 ketones, 1 ester, and 3 lactones. Quantification of VOC’s was carried out using the technique of standard addition. The limits of quantification ranged from 0.0033 to 0.0311 ng/μg. Ten compounds were identified with the heaviest concentration and are listed as follows, from heaviest to lightest: propionic acid, acetoin, acetic acid, diacetyl, capric acid, caprylic acid, δ-decalactone, δ-dodecalactone, γ-dodecalactone, butyraldehyde. During storage of the cheese, the most significant changes in the concentration of VOC’s took place between day 1 and day 15. Based on the results obtained, it can be concluded that the optimization of the SPME makes it possible to isolate and quantify VOC’s of fresh cheeses in an efficient and reproducible manner.

Different spectrophotometric methods applied for the analysis of simeprevir in the presence of its oxidative degradation product: Acomparative study

Five simple spectrophotometric methods were developed for the determination of simeprevir in the presence of its oxidative degradation product namely, ratio difference, mean centering, derivative ratio using the Savitsky-Golay filters, second derivative and continuous wavelet transform. These methods are linear in the range of 2.5–40μg/mL and validated according to the ICH guidelines. The obtained results of accuracy, repeatability and precision were found to be within the acceptable limits. The specificity of the proposed methods was tested using laboratory prepared mixtures and assessed by applying the standard addition technique. Furthermore, these methods were statistically comparable to RP-HPLC method and good results were obtained. So, they can be used for the routine analysis of simeprevir in quality-control laboratories.

A Validated Spectrophotometric Method and Thermodynamic Studies for the Determination of Cilostazol and Rivaroxaban in Pharmaceutical Preparations Using Fe-Phenanthroline System

A spectrophotometric method has been adopted for the determination of cilostazol and rivaroxaban. The method was based on the oxidation of the selected drugs by iron (III) in the presence of 1, 10-phenanthroline and formation of tris (1, 10-phenanthroline) iron (II) complex (ferroin) with λmax at 510 ± 1 nm. All experimental conditions were carefully studied and optimized. The method was obeyed beer’s law in concentration range (0.5-10 μg/ mL) for cilostazol at pH 3.5 and (30-400 μg/ mL) for rivaroxaban. The spectrophotometric measurements enabled the detection of cilostazol and rivaroxaban at 0.046 μg/ mL for cilostazol and 4.719 μg/ mL for rivaroxaban. Apparent molar absorptivity was 53.02 × 103 and 1.28 × 103 L/mol/ cm, whereas the corresponding sandell sensitivity was 0.0069 and 0.28 μg/cm-2 for cilostazol and rivaroxaban, respectively. Method validation was performed as per ICH Q2 (R1) guidelines. Furthermore, thermodynamic parameters; free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) of complexation were evaluated. The reliability of the procedure has been successfully ascertained by assay of pharmaceutical formulations and recovery tests by standard addition technique. The results obtained were statistically compared with those of the reference methods using student t-test and F ratio.

Optimization of a method for the determination of a mustard gas biomarker in human blood plasma by liquid chromatography–mass spectrometry

A method for the determination of a mustard gas biomarker (an S-hydroxyethylthioethyl adduct with albumin) in blood plasma was optimized with the use of HPLC with tandem mass-spectrometric detection. This method is based on the hydrolysis of this adduct by the proteinase K enzyme with the formation of the following stable tripeptide with cysteine, proline, and phenylalanine: S-HETE-Cys-Pro-Phe. The detection limit of mustard gas in human blood plasma was 2 ng/ml. The approach proposed was tested in the analysis of human blood plasma samples by the standard addition technique and also within the framework of the first official biomedical test carried out by the Organization for the Prohibition of Chemical Weapons (OPCW) in 2016, and it exhibited a good accuracy, reproducibility, and specificity of determination.

Establishing Laboratory Analysis Procedure for EPA FIFRA Enforcement Samples to Meet the ISO/IEC 17025:2005 Requirements using Flexible Scope Approach

An ISO/IEC 17025:2005 accredited laboratory procedure that quantifies analytes and validates an analytical method used simultaneously was established for analyzing pesticide misuse samples. Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the U.S. Environmental Protection Agency (EPA) grants the authority over regulating pesticide use to each state. Samples for pesticide misuse cases such as drift complaints are analyzed by state laboratories (state FIFRA labs). State FIFRA labs receive samples that require quick turnaround with a variety of unique matrix/analyte combinations. The majority of the samples are analyzed by non-standard methods that are developed by the laboratory. It is impractical to pre-validate such non-standard methods. Yet, the forensic nature of pesticide misuse investigation samples demands legally defensible analytical data. The author's laboratory developed an expedited validation procedure that is conducted simultaneously with analyte quantitation by using the standard addition technique. The procedure received ISO/IEC 17025:2005 accreditation from the American Association for Laboratory Accreditation under their Flexible Scope Policy. The developed validation protocol and associated procedural changes made to the daily operations are supported by several laboratory documents that are unique to the Flexible Scope option.https://doi.org/10.21423/jrs-v05n02p010 (DOI assigned 3/11/2019)

Kinetic study on carbothermic reduction of ilmenite with activated carbon

Abstract The carbothermic reduction of Panzhihua ilmenite with various additions of activated carbon was investigated by isothermal experiments over the temperature range of 1373 to 1773 K in the argon atmosphere. According to the reaction kinetics recorded by the infrared gas analyzer, it was found that the amount of carbon addition had little influence on the reaction rates at various temperatures except 1473 K. When the reaction temperature was above the eutectic temperature of 1427 K of Fe–C binary system, part of carbon would dissolve into Fe to form a liquid phase, which made the liquid Fe as a diffusion channel of carbon to diffuse to the reaction interface. The carbothermic reduction above 1573 K obeyed the shrinking-core model. The mass fraction of TiC could be determined by the standard addition technique.

Assessment of anthropogenic influence on the level of selected heavy metals (Cu, Zn, Cd and Pb) in soil

The study aimed at assessing potential influence of anthropogenic activities on the level of selected toxic heavy metals in soil in Tsumeb Township, Namibia. This was with a view of evaluating possible implications on human health and across the food chain. Soil samples were randomly collected from stratified areas and taken to the laboratory for pre-treatment and analysis. Soil metallic contents were extracted using acid digestion technique and were quantified using ICP-OES. Experimental protocol was validated using the standard metal addition techniques and was found to be applicable with quantitative metallic recoveries (n= 3) in the range of 85-90%. The overall mean concentration of analysed metals in soil samples ranged from 39.0 - 2532.8 mg/kg (Cu); 59.5- 1994.8 mg/kg (Zn); 1.7-21.3 mg/kg (Cd) and 1.2-141 mg/kg (Pb) across SCP1-SCP4. The analysed metals increased variedly at the SCPs in the order Cu: SCP1>SCP2>SCP4>SCP3; Zn: SCP1>SCP2>SCP4> SCP3; Cd: SCP1>SCP2>SCP3>SCP4; Pb: SCP1>SCP2>SCP3>SCP4. Hence, highest or most profound anthropogenic influence was observed at SCP1 for all metals while the lowest was as SCP4. Strong metallic correlation (r > 0.99) was obtained between all analysed metals and some significant above threshold metallic levels in soil were obtained for Cu and Zn but most worrisome was the high level of Cd obtained in soil. Possible uptake of these metals by plants and transfer across the food chain is highly probable. Key words: Heavy metals, soil, human health, anthropogenic, ICP-OES, Namibia.

Exact Matrix‐matching Calibration by Standard Addition‐Isotope Dilution‐Liquid Chromatography/Mass Spectrometry for the Accurate Determination of Chloramphenicol in Infant Formula

We consistently observed a bias in the results for determination of chloramphenicol (CAP) in infant formula by isotope dilution‐liquid chromatography/mass spectrometry (ID‐LC/MS). Various matrix interferences from infant formula eventually can result in bias during the ID‐LC/MS analysis. We tried to optimize LC conditions to minimize matrix effects by separating significant matrix interferences from the analyte and the internal standard, but some level of bias remained. To eliminate the bias due to the matrix effects, we used a standard addition‐isotope dilution‐liquid chromatography/mass spectrometry (SA‐ID‐LC/MS) method for CAP analysis. In the SA‐ID‐LC/MS method, standard addition techniques were combined with IDMS for exact matrix matching while keeping the isotope dilution techniques as a tool for accurate correction of recovery in sample preparation processes. The method provided accurate analytical results for target analyte in the range of 1 µg/kg with a relative expanded uncertainty of 3%.

RAPID ISOLATION OF THE BIOACTIVE METABOLITE OF CYMBOPOGON PROXIMUS AND DEVELOPMENT OF LC METHOD

Objective: Development of a rapid isolation method to afford the bioactive metabolite (proximadiol: prox) from its herb (Cymbopogan proximus Stapf.) in the purest form and validate an LC method for its determination was our goal in this work. Methods: Prox was isolated by chromatographic techniques from the dichloromethane extract of the herb on alumina column, using petroleum ether-ethyl acetate solvent mixtures with increasing polarity.The determination of prox was achieved by LC method. The chromatographic separation was carried out on Thermo Hypersil ODS (4.5 x 250 mm, 10 µm) column, in the presence of 8-chlorotheophylline as an internal standard. The mobile phase was composed of 0.1 M phosphate buffer (pH: 3.5): methanol (60:40 v/v) and was pumped at a flow rate of 1 ml/min. The detection and quantification were done at 210 nm.Results: The structure elucidation of the isolated compound was identified on the basis of its spectral data.A simple and reproducible LC method was developed for the determination of the isolated purified Prox. Adequate separation and good resolution were obtained between prox and 8-chlorotheophylline. Quantification was achieved at 210 nm over concentration range 12.00-33.60 µg/ml with mean percentage recovery of 99.29±0.340. The method was validated in accordance with USP specifications. All analytical criterions were within acceptable range. The validity of the results was assessed by applying standard addition technique. The results obtained were compared with the reported method.Conclusion: The proposed method could be applied for routine quality control analysis of pharmaceutical formulations containing prox.

Trace determination of Hg together with As, Sb, Se by miniaturized optical emission spectrometry integrated with chemical vapor generation and capacitively coupled argon microwave miniplasma discharge

A miniaturized optical emission spectrometer (OES) with capacitively coupled argon microwave microplasma (μCMP) as and excitation source and chemical vapor generation (CVG) for sample introduction was constructed for the determination of trace Hg, As, Sb and Se. The applied method enabled simultaneous determination of hydride-forming elements (As, Sb, Se) and volatile Hg. Mercury cold vapor and the hydride volatile species of As, Sb and Se were generated when standard or sample solutions were separated from the liquid phase for transport to the capacitively coupled microwave microplasma and detection of their atomic emission. A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. The experimental concentration detection limits (LODs) for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 3.0, 1.4, 1.5 and 3.8ngmL−1 for Hg, As, Sb and Se, respectively. The method was validated by the analysis of three Certified Reference Materials (NIST 2711, NRCC DOLT-2, NIST 1643e) of different matrix composition and by the standard addition technique. The method offers relatively good precision (RSD ranged from 5% to 8%) for microsampling (200μL) analysis. The measured of contents of elements in certified reference materials were in good agreement with the certified values (Hg 1.99–6.25μgg−1, As 16.6–105μgg−1, Sb 19.4–56.88μgg−1, Se 1.52–11.68μgg−1), according to the Student t-test, for a confidence level of 95%.

Simple and Fast Sample Preparation Followed by Gas Chromatography-Tandem Mass Spectrometry (GC-MS/MS) for the Analysis of 2- and 4-Methylimidazole in Cola and Dark Beer.

We have developed a simple and fast sample preparation technique in combination with a gas chromatography-tandem mass spectrometry (GC-MS/MS) for the quantification of 2-methylimidazole (2-MeI) and 4-methylimidazole (4-MeI) in colas and dark beers. Conventional sample preparation technique for GC-MS requires laborious and time-consuming steps consisting of sample concentration, pH adjustment, ion pair extraction, centrifugation, back-extraction, centrifugation, derivatization, and extraction. Our sample preparation technique consists of only 2 steps (in situ derivation and extraction) which requires less than 3 min. This method provided high linearity, low limit of detection and limit of quantification, high recovery, and high intra- and interday repeatability. It was found that internal standard method with diluted stable isotope (4-MeI-d6 ) and 2-ethylimidazole (2-EI) could not correctly compensate the matrix effects. Thus, standard addition technique was used for the quantification of 2- and 4-MeI. The established method was successfully applied to colas and dark beers for the determination of 2-MeI and 4-MeI. The 4-MeI contents in colas and dark beers ranged from 8 to 319 μg/L and from trace to 417 μg/L, respectively. Small quantity (0 to 8 μg/L) of 2-MeI was found only in dark beers. The contents of 4-MeI (22 μg/L) in colas obtained from fast food restaurants were significantly lower than those (177 μg/L) in canned or bottled colas.

Optimization of a method for the determination of a mustard gas biomarker in human blood plasma by liquid chromatography–high-resolution mass spectrometry

A method for the determination of a mustard gas biomarker (an S-hydroxyethylthioethyl adduct with albumin) in blood plasma was optimized with the use of HPLC with high-resolution tandem mass-spectrometric detection. This method is based on the hydrolysis of this adduct by the proteinase K enzyme with the formation of the following stable tripeptide with cysteine, proline, and phenylalanine: S-[HETE]-Cys- Pro-Phe. The conditions of the sample preparation of human plasma artificially contaminated by mustard gas (the selection of an aliquot portion volume and an enzyme for the hydrolysis), the mass-spectrometric detection (the selection of optimum pairs of ion reactions and high-resolution detection modes), and the gradient elution program in the HPLC separation of an analyzed mixture were optimized. The detection limit of mustard gas in human blood plasma was 1 ng/mL. The approach proposed was tested in the analysis of human blood plasma samples by the standard addition technique and also within the framework of the first official biomedical test carried out by the Organization for the Prohibition of Chemical Weapons (OPCW) in 2016, and it exhibited a good accuracy, reproducibility, and specificity of determination.

Spectrophotometric determination of meclizine hydrochloride and pyridoxine hydrochloride in laboratory prepared mixtures and in their pharmaceutical preparation

In this paper, three rapid, simple, accurate and precise spectrophotometric methods were developed for the determination of meclizine hydrochloride in the presence of pyridoxine hydrochloride without previous separation. The methods under study are dual wavelength (DWL), ratio difference (RD) and continuous wavelet transform (CWT). On the other hand, pyridoxine hydrochloride (PYH) was determined directly at 291nm. The methods obey Beer's law in the range of (5–50μg/mL) for both compounds. All the methods were validated according to the ICH guidelines where the accuracy was found to be 98.29, 99.59, 100.42 and 100.62% for DWL, RD, CWT and PYH; respectively. Moreover the precision of the methods were calculated in terms of %RSD and it was found to be 0.545, 0.372, 1.287 and 0.759 for DWL, RD,CWT and PYH; respectively. The selectivity of the proposed methods was tested using laboratory prepared mixtures and assessed by applying the standard addition technique. So, they can be used for the routine analysis of pyridoxine hydrochloride and meclizine hydrochloride in quality-control laboratories.

An Enzymatic Method for Methanol Quantification in Methanol/Ethanol Mixtures with a Microtiter Plate Fluorometer

In response to the need for a rapid, high-throughput screening of methanol contamination in spirits, a new microplate-based assay was developed. In this assay, alcohol oxidase first oxidizes methanol to formaldehyde, which is further oxidized to formate by formaldehyde dehydrogenase while reducing NAD+ to NADH. The latter product then reacts with resazurin under catalysis by FerB, a diaphorase-type enzyme, to give the highly fluorescent resorufin. These reactions are run simultaneously in 200 μL final volume in a 96-well plate and quantified using a plate reader and fluorescence detector. It is shown that the rate of fluorescence change is related to methanol and ethanol concentrations according to the rate law for two competing substrates. Quantification of methanol in real samples is carried out by applying the standard additions technique with four different spiking concentrations of the methanol standard; methanol content in the sample is calculated from the x-intercept of the fitted line. The high activity of FerB with resazurin and low rate of further conversion of resorufin to non-fluorescent dihydroresorufin indicate that FerB may be advantageous over commercially available diaphorases for use in fluorescence enzyme assays.

Fat-Soluble Vitamin and Carotenoid Analysis in Cooking Oils by Ultra-Performance Convergence Chromatography

In the current study, a rapid ultra-performance convergence chromatography (UPC2) method for the determination of seven fat-soluble vitamins (vitamin A: retinol, retinyl acetate; vitamin D: ergocalciferol, cholecalciferol; vitamin E: α-tocopherol; vitamin K: phylloquinone, menaquinone) and three carotenoids (lutein, lycopene, β-carotene) in various cooking oils was developed. Fat-soluble vitamins could be separated within 8 min on a UPC2 system with a BEH column (3.0 × 100 mm, 1.7 μm) at 50 °C, using a gradient elution with a mobile phase of carbon dioxide and 2-propanol (99.9:0.1/99.2:0.8/99.9:0.1), at a flow rate of 2 mL/min and the automatic back pressure regulator (ABPR) set to 1800 psi. Carotenoids were separated within 3 min on a similar UPC2 system with an HSS C18 SB column (3.0 × 100 mm, 1.8 μm) at 40 °C, under isocratic conditions with a mobile phase of carbon dioxide and ethanol (75:25; v/v). The flow rate was set to 1.5 mL/min and the ABPR to 1800 psi. The limits of detection (LODs) and quantification (LOQs) were ranging between 0.01 and 1.17 μg/mL and from 0.05 and 3.59 μg/mL for fat-soluble vitamins while carotenoid detection limits fell in the range of 0.03–0.11 μg/mL and of 0.10–0.38 μg/mL, respectively. The results showed excellent linearity for both methods (R2 0.9993–0.9999). A recovery study with standard addition technique into a selected coconut oil sample resulted in more than 90 % recovery for retinyl acetate, retinol, and vitamin K1 and K2, whereas the recovery for vitamin D2 and D3 ranged between 70 and 80 %. The lowest recovery of 68–70 % was found for α-tocopherol while almost comparable recovery rates above 80 % were observed for all three carotenoids.

Slurry micro-sampling technique for use in argon-helium microwave induced plasma optical emission spectrometry

The Flow Focusing Pneumatic Nebulizer (FFPN) working at low liquid flow rates was evaluated for the elemental analysis in slurried samples by argon-helium microwave induced plasma optical emission spectrometry (MIP-OES). The obtained results achieved were compared with commercially available V-groove Babington type nebulizer (VBPN). A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit.Analytical performance of the micro nebulization system was characterized by a determination of the limits of detection (LODs), the precision (RSDs) and the wash-out times for Ba, Ca, Cd, Cu, Fe, Mg, Mn, Pb and Sr. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 0.9, 0.2, 0.3, 0.2, 0.3, 0.1, 0.2, 0.4, 0.4 and 0.3ngmL−1 for Ba, Ca, Cd, Cu, Fe, Mg, Mn, Pb and Sr, respectively. The method offers relatively good precision (RSD ranged from 5% to 8%) for micro-slurry sampling analysis. Analyses of the certified reference materials (NRCC DOLT-2, GBW 07302 and SRM 2710) were performed in order to determine the accuracy available with the presented nebulization systems. The measured contents of elements in the reference materials were in satisfactory agreement with the certified values. In addition, these elements were determined in two real samples.Slurry concentration up to 3% m/v (particles <20μm), prepared in 10% m/v HCl through the application of ultrasonic agitation, was used with calibration by the standard addition technique. An ultrasonic probe was used to homogenize the slurry in the polypropylene bottle just before its introduction into the nebulizer. The nebulizers exhibited no clogging problems.

Comparative Study Among Area Under the Curve, Graphical Absorbance Ratio and Isosbestic Point as Analytical Tools Applied for the Simultaneous Determination of Chlorpheniramine maleate and Naphazoline hydrochloride

Three smart spectrophotometric methods were developed for the simultaneous estimation of chlorpheniramine maleate and naphazoline hydrochloride, a binary mixture with overlapping spectra, without preliminary separation. These methods include area under the curve (AUC), graphical absorbance ratio (Q-analysis) and isosbestic point spectrophotometry. A comparative study among the methods was done showing the advantages and the disadvantages of each method. Beer’s law is obeyed over the concentration range of 5- 35 and 5-40 μg/ml for chlorpheniramine maleate and naphazoline hydrochloride,respectively (for area under the curve), and 5-40 μg/ml for each drug (for Q-analysis and isosbestic point). All the proposed methods were extensively validated according to the ICH guidelines and the obtained accuracy, precision and repeatability were found to be within the acceptable limits. The selectivity of the proposed methods was tested using laboratory prepared mixtures and assessed by applying the standard addition technique. The proposed methods were found to be rapid, simple and required no preliminary separation steps.