Ratio Difference Spectrophotometric Method Research Articles

Area under the curve and ratio difference spectrophotometric methods with evaluation of the greenness for simultaneous determination of olmesartan medoxomil and metoprolol succinate

The aim of this study is to develop and validate two simple spectrophotometric methods for simultaneous determination of metoprolol succinate (MET) and olmesartan medoxomil (OLM) in tablet form. Method (I) was area under the curve (AUC) method. This approach involved the measuring of the area over a variety of wavelengths. Two wavelength ranges; 213–230 nm and 244–266 nm were chosen for determination of MET and OLM, respectively. Method (II) was ratio difference spectrophotometricmethod. For determination of MET, the ratio spectra were generated using 15 μg/mL OLM as a divisor then the peak to trough amplitudes between 221 nm and 245 nm were displayed versus the corresponding concentrations of MET. For determination of OLM, the peak-to-peak amplitudes between 247 and 293 nm were chosen and found to be directly proportional to OLM concentrations using 15 μg/mL MET as a divisor. The linearity ranges were 2–30 μg/mL and 2–25 μg/mL for MET and OLM, respectively. The assay results showed good mean %recovery ± SD as well as good agreement with that of the reported method. The developed methods were validated according to ICH guidelines. The developed methods are accurate, precise, eco-friendly and could be applied successfully to estimate OLM and MET in their combined dosage form.

Effective spectrophotometric methods for resolving the superimposed spectra of Diclofenac Potassium and Methocarbamol

The UV spectra of Diclofenac Potassium DIC and Methocarbamol MET are superimposed making their analysis using direct or derivative spectrophotometric methods quite complicated. This study presents four effective spectrophotometric methods that enable simultaneous determination of both drugs without interference. The first method is based on application of simultaneous equation method on their zero order spectra where DIC has shown absorbance maxima at 276 nm and MET displays two absorbances maxima at 273 nm and 222 nm in distilled water. The second method relies on dual wavelength method, the two wavelengths (232 and 285 nm) were chosen for determination of DIC where the absorbance differences at these wavelengths are proportional to DIC concentration while the absorbance differences of MET are equal to zero. For the determination of MET, the two wavelengths (212 and 228 nm) were selected. The third method of first-derivative ratio has been applied where the derivative ratio absorbances of DIC and MET were measured at 286.1 and 282.4 nm, respectively. The fourth method utilizing ratio difference spectrophotometric (RD) method was eventually performed on the binary mixture. The amplitude difference between the two wavelengths (291and 305 nm) was calculated for DIC estimation while the amplitude difference between the two wavelengths (227and 273 nm) for MET determination. All methods show linearity range from 2.0–25 μg. mL−1 and 6.0–40 μg. mL−1 for DIC and MET respectively. The developed methods have been statistically compared with a reported method based on first derivative method and the results of statistical comparison confirm the accuracy and precision of the proposed methods therefore they can be effectively applied for determination of MET and DIC in pharmaceutical dosage form.

Green-assisted spectrophotometric techniques utilizing mathematical and ratio spectra manipulations to resolve severely overlapped spectra of a cardiovascular pharmaceutical mixture

Cardiovascular diseases, in particular hypertension and hypercholesterolemia, are two of the main causes of death worldwide. These conditions are silent killer syndromes that need a variety of pharmacological treatments to be effectively controlled. This study introduces novel, environmentally friendly spectrophotometric techniques for the simultaneous determination of telmisartan (TMS) and rosuvastatin calcium (RVS) in their pharmaceutical dosage forms. For the simultaneous determination of the binary mixture, the suggested methods included the dual wavelength method (DWM) which utilizes mainly the absorbance difference at 233 nm and 253 for TMS determination and, the absorbance difference at 274 nm and 310 for RVS determination as the selected wavelengths for each drug is directly proportional to the drug of interest independent on the other interfering component. The Fourier-self deconvolutions method (FSDM) depends on compressing their bandwidth to resolve the overlap. Ratio difference spectrophotometric method (RDSM) that utilizes TMS 35 μg.mL−1 and RVS 20 μg.mL−1, respectively as divisors to produce the ratio spectra for each drug. Further manipulation of the produced ratio spectra was applied for the determination of the two drugs. Mean centering method (MCM) where a suitable wavelength range was chosen to exclusively use the informative portions and prevent experimental spectrum noises. The investigated methods showed good levels of detection and quantification together with excellent linearity. The suggested methods' greenness was evaluated using two different greenness evaluation tools, which showed that the methods were green in terms of several factors, including the safety of the chemicals, instruments, and waste. The validity of the methodologieswas investigated by resolving prepared laboratory mixtureswith varying TMS and RVS ratios. The standard addition method also assured the newly added methods. Finally, statistical analysis using the reported method did not reveal any appreciable differences in terms of accuracy and precision. The developed methods can be employed in quality control laboratories to ascertain the binary mixture due to their high precision and affordability.

Quantitative Analysis of Two Pharmaceutical Combinations Containing Amlodipine with Either Bisoprolol or Candesartan Using Different UV Spectrophotometric Methods.

Two fixed-dose combination tablets of amlodipine (AML) with bisoprolol (BIS) and amlodipine with candesartan (CAN) were recently approved for the treatment of hypertension. Three UV spectrophotometric analytical methods were developed for the estimation of the above drugs in their combination mixtures. For the AML and BIS mixture, AML was quantified directly by a zero-order spectrophotometric method at 360 nm without interference from BIS, whereas BIS was quantified by the ratio difference (RD) spectrophotometric method by calculating the difference between the amplitude values of the ratio spectra at 226 and 215 nm. For the AML and CAN mixture, AML was quantified directly by a zero-order spectrophotometric method at 360 nm without interference from CAN, whereas CAN was quantified by the first derivative of ratio spectra method by measuring the amplitude values of the derived spectra at 259 nm.BIS). The proposed methods were successfully applied for quantitative analysis of AML with BIS and AML with CAN in their synthetic laboratory-prepared mixtures and pharmaceutical tablets with acceptable results in terms of accuracy and precision. Simple, accurate, and environmentally friendly spectrophotometric methods were described for selective determination of the investigated drugs in their fixed-dose combinations.

Determination of Sulphasalazine and Its Related Compounds by Simple, Smart, Validated, Green Spectrophotometric Methods.

Sulphasalazine (SZ) is a prodrug. Its active metabolite (mesalazine, MZ), which is also available in pharmaceutical formulations, and the major active metabolite of MZ (N-acetyl-5-aminosalicylic acid, AS) are commonly used for the treatment of inflammatory bowel diseases. Two accurate, precise, sensitive, and specific spectrophotometric methods were developed and validated for determination of the studied components. The first method is a modified ratio difference spectrophotometric method. In this method, SZ was determined by measuring the peak area from 410-500 nm, while MZ and AS were determined by measuring the difference of the selected amplitude values. The second method is a mean centering of ratio spectra spectrophotometric method. The developed methods were linear over the concentration ranges of 2-35, 2-30 and 1-25 µg/mL for SZ, MZ and AS, respectively. The developed methods were validated according to International Conference on Harmonization guidelines. They were successfully applied for determination of studied analytes. A greenness assessment was undertaken using three different tools. Spectrophotometric methods were developed for determination of SZ and its related compounds for the first time. They were designated to be green and eco-friendly and their greenness profiles were evaluated using green solvents to keep the environment clean.

Simultaneous determination of Xipamide and Triamterene by zero order, first derivative, derivative ratio and ratio difference spectrophotometric methods.

Validated, rapid and sensitive spectrophotometric techniques were established for simultaneous determination of Xipamide and Triamterene. The first technique based on determination of Triamterene with zero-crossing of Xipamide using zero order method at 367.0 nm. The second technique based on determination of both Xipamide and Triamterene by first derivative method with zero-crossing of Triamterene and Xipamide respectively, at 265.6 and 388.6 nm. Third technique is ratio difference spectrophotometric method depending on obtaining peak amplitude difference at 256.0 and 273.0 nm for Xipamide and 288.0, 302.0 nm for Triamterene. Fourth method is derivative ratio spectrophotometric method depending on obtaining the first derivative of the ratio spectrum with zero-crossing of Xipamide and Triamterene at 365.2 and 308.6 nm; respectively. Linear relationship was obtained upon using concentration range (1.0-10.0 µg/mL) for Xipamide and (1.0-16.0 µg/mL) for Triamterene with LOD less than 0.3 µg/mL for both drugs. The suggested spectrophotometric techniques showed Lower LOD and more sensitivity other than any reported spectrophotometric methods and were applied in pure and dosage form (Epitens®).

Simple and efficient spectroscopic-based univariate sequential methods for simultaneous quantitative analysis of vandetanib, dasatinib, and sorafenib in pharmaceutical preparations and biological fluids

Six sequential spectrophotometric-based univariate methods were developed and validated for the simultaneous estimation of three novel anticancer drugs vandetanib (VAN), dasatinib (DAS), and sorafenib (SOR) in a mixture, without the requirement for separation. These methods are novel, simple, precise, and accurate. Different steps including zero crossing, ratio-based, and/or derivative spectra were utilized to develop these analytical methods, namely, ratio difference spectrophotometric method, constant center method, successive derivative ratio method, isoabsorptive method, mean centering of the ratio spectra method, and derivative ratio spectrum–zero crossing method. The calibration curve linearity was ranged from 2 to 9, 2–9, and 3–9 μgmL−1 for VAN, DAS, and SOR, respectively. These established methods were applied for the quantification of the three selected drugs in different biological fluids (spiked human plasma and urine) and pharmaceutical preparations. The aforementioned methods were established for the concurrent estimation of ternary and binary mixtures to enhance the signal-to-noise ratio. The results did not statistically differ from the other reported methods, indicating no significant difference in accuracy and precision at p = 0.05.

Simultaneous determination of enalapril maleate and nitrendipine in tablets using spectrophotometric methods manipulating ratio spectra.

A fixed dose combination of enalapril maleate (EN) and nitrendipine (NT) achieved satisfactory blood pressure control rather than monotherapy. Four accurate spectrophotometric methods utilizing ratio spectra were developed and validated for the simultaneous determination of EN and NT in combined pharmaceutical dosage form (Eneas® tablets). The first method was first derivative ratio spectrophotometric method (1DD) where the amplitudes maxima were measured at 219.2nm and 233.4nm for the determination of EN and NT, respectively. The second method was ratio difference spectrophotometric method where EN and NT were estimated by measuring the amplitudes difference between 213nm and 225nm on the ratio spectrum of EN and between 241nm and 227nm on the ratio spectrum of NT. The third method was ratio subtraction followed by extended ratio subtraction, EN was determined at 210nm by subtraction of the constant values from the ratio spectrum then multiplication with the divisor (NT spectrum). An extended ratio subtraction method was then applied in order to determine NT at 235nm by using the zero-order spectrum of EN (10μg/ml) as a divisor. The fourth method was ratio subtraction coupled with constant multiplication methods. The zero- order absorption spectrum of the laboratory prepared mixture was divided by NT (12μg/ml) spectrum, subsequently, the value of the constant was multiplied by the divisor to obtain the original spectrum of NT, followed by its subtraction from the laboratory prepared mixture to get the spectrum of EN. EN and NT were determined at 210nm and 235nm, respectively. Linearity was ascertained over the concentration ranges of (1-11μg/ml) for EN and (2-14μg/ml) for NT, for the first and second methods and (2-13μg/ml) for EN and (3-20μg/ml) of NT, for the third and fourth methods. Application of the methods to the determination of the cited drugs in Eneas® tablets gave satisfactory results. Methods validation confirmed their accuracy and selectivity. Statistical comparison of the results with the reported one showed no significant difference, regarding precision and accuracy. Routine analysis of the cited drugs in quality control laboratories could be performed using the developed methods.

Resolving a Binary Mixture of Hepatoprotective Drugs Using Different Validated Spectrophotometric Methods

This work is concerned with development and validation of two simple, specific, accurate and precise spectrophotometric methods for determination of two hepatoprotective drugs, silymarin (SR) and vitamin E acetate (VE), in their binary mixtures and a pharmaceutical formulation. Method A is a ratio difference spectrophotometric method (RDSM), while method B is a mean centering of ratio spectra spectrophotometric one (MCR). In both methods, the absorption spectra of each drug were recorded, divided by a suitable divisor, then the obtained ratio spectra were subtracted at two specific wavelengths in the ratio difference spectrophotometric method, while the obtained ratio spectra were mean centered in the mean centering of ratio spectra spectrophotometric method. The specificity of the developed methods was assessed by analyzing different laboratory prepared mixtures containing SR and VE. The two methods were validated as per the International Conference on Harmonization guidelines. Accuracy, precision and repeatability were found to be within the acceptable limits.

The Development of a Manipulative Spectrophotometric Technique for the Determination of Aminexil in a New Hair Tonic Preparation

A simple and economic ratio difference spectrophotometric method was developed and validated for the determination of Aminexil (AX), which is a new compound patented by L'Oreal, in the presence of niacinamide (NA) and pyridoxine (PD) in a newly introduced cosmetic preparation. The proposed method was found to be suitable for the determination of Aminexil in its laboratory prepared mixture in presence of the two other components; and in the commercial cosmetic preparation where the three components were co-formulated. The calibration curve was constructed with a concentration range from 2-10 μgmL-1 showing 100.22± 0.53 accuracy. The LOD and LOQ were found to be 0.53 and 1.6 μgmL-1 respectively. The method was validated according to ICH guidelines. The standard addition methods showed satisfactory mean recovery of 99.68±0.56.The obtained results were satisfactory enough for further statistical analysis, in comparison to the reported method. The proposed method had the advantage of being simple since no manipulation or complicated handling of the samples were needed, as well as economic, since there was no use of sophisticated instruments or expensive chemicals.

Development and Validation of Different Spectrophotometric and High-Performance Thin-Layer Chromatographic Methods for the Determination of Fosinopril Sodium, Hydrochlorothiazide, and Chlorothiazide as Hydrochlorothiazide Impurity

Three simple, sensitive, and validated methods were developed for the quantitative determination of fosinopril sodium (FOS) and hydrochlorothiazide (HCZ) in the presence of an HCZ impurity, chlorothiazide (CZ). The first method (I) was the ratio difference spectrophotometric method (RD), in which a standard spectrum of 8 μg mL-1 HCZ was used as a divisor, and the difference in amplitude values at 204.6 and 231.2 nm and 290 and 302.6 nm was used for the determination of FOS and CZ, respectively. Meanwhile, for the determination of HCZ, a standard spectrum of 6 μg mL-1 CZ was the chosen divisor, and the amplitude difference at 275 nm and 293.6 nm was selected for the calculation of its concentrations. The second method (II) was mean centering of ratio spectra spectrophotometric method (MCR), which depended on the implementation of the mean-centered ratio spectra in two successive steps and the measurement of the amplitudes of the mean-centered second ratio spectra at 243.4 nm for CZ and peak-to-peak amplitudes at 215.6 and 215.8 nm for FOS and at 223.8 and 224 nm for HCZ. On the other hand, the third method (III) was thin-layer chromatography (TLC)—densitometry at which the chromatographic separation of this ternary mixture was performed using pre-activated silica gel 60 F254 TLC plates and a developing system mixture consisting of ethyl acetate—chloroform—methanol—formic acid (60:40:5:0.5, by volume) with ultraviolet (UV) scanning at 215 nm. The developed methods were validated according to the International Conference of Harmonization (ICH) guidelines and were successfully used for the determination of FOS and HCZ in their pharmaceutical formulations. Also, a statistical comparison between the developed methods and the reported HPLC method was attained. Using Student’ s t-test and F-test, the results confirmed that there was not any significant difference between them regarding accuracy and precision.

Novel spectrophotometric methods for the determination of Leflunomide and Diacerein in binary mixtures.

Two novel spectrophotometric methods were presented in this work using ethanol as a solvent. The first method was the ratio difference spectrophotometric method [RDSM], in which the amplitude difference between two selected wavelengths on the ratio spectra were recorded and used for estimation of each of Leflunomide LEF in mixture with its alkaline induced degradate DEG and also for Diacerein DIA determination in mixture with Aceclofenac ACEC without interference from the other component in the mixture. The second method is the ratio subtraction coupled with constant multiplication [RS-CM], where LEF was determined in its mixture with its alkaline degradate DEG at 261 nm which is considered as a stability indicating assay. In addition to simultaneous determination of Diacerein DIA and Aceclofenac ACEC in their mixtures at 257 and 277 nm, respectively, by the second method without previous separation. Linearity was shown over the concentration range of [1.5-15 μg/ml] for LEF, [1-11 μg/ml] for DIA and [2.5-25 μg/ml] for ACEC, by both proposed methods. Leflunomide was found to be completely degraded when subjected to alkaline degradation producing one alkaline product. Validation of the suggested methods was conducted according to ICH guidelines, concerning precision, accuracy, repeatability. The suggested spectrophotometric methods were statistically compared to reference methods showing no significant difference. The suggested spectrophotometric methods are considered to be simple, sensitive and could be easily applied in quality control laboratories instead of LC methods.

Determination of antihypertensive drugs by using ratio difference spectrophotometric method

An accurate, sensitive and time saving spectrophotometric method has been developed and validated for the determination of two antihypertensive drug mixtures. Mixture 1 contains spironolactone (SPIR), furosemide (FUR) and anthranilic acid (ANTH) (impurity of furosemide) and mixture 2 contains triamterene (TRI), hydrochlorothiazide (HCZ) and chlorothiazide (CZ) (impurity of hydrochlorothiazide). In mixture 1, the determination of drugs depends on dividing the spectrum of ternary mixture by the spectrum of 10 µg/mL of standard furosemide and then spironolactone and anthranilic acid were determined using the difference in amplitude between 242.3 and 254.6 nm, and between 250.8 and 242.4 nm in the ratio spectrum, respectively. On the other hand, furosemide could be determined by dividing the spectrum of ternary mixture by the spectrum of 10 µg/mL of standard spironolactone and then it was determined using the difference in amplitude between 244.8 and 229.7 nm in the ratio spectrum. In mixture 2, the determination of drugs depends on dividing the spectrum of ternary mixture by spectrum of 10 µg/mL of standard triamterene and then hydrochlorothiazide and chlorothiazide were determined using the difference in amplitude between 268.9 and 232.8 nm, and between 292.9 and 250.7 nm in the ratio spectrum, respectively. On the other hand, triamterene could be determined by dividing spectrum of ternary mixture by spectrum of 10 µg/mL of standard hydrochlorothiazide and then triamterene was determined using the difference in amplitude between 230.1 and 244 nm in the ratio spectrum. The developed analytical methods were validated regarding good accuracy and precision according to The International Conference on Harmonisation guidelines, and they were applied to pharmaceutical preparations in addition to laboratory prepared mixtures successfully. Statistically the results were compared with those obtained by reported method and no significant difference was found.

Development and validation of spectrophotometric and high-performance thin-layer chromatographic methods for the determination of folic acid in the presence of its impurities (degradation products)

Three accurate, sensitive, simple, and precise spectrophotometric methods along with thin-layer chromatography (TLC)–densitometric method were developed, optimized, and validated for the determination of folic acid in the presence of its two impurities (photodegradation products), namely, pteroic acid and para-aminobenzoic acid. Method A is the ratio difference spectrophotometric method (RDSM) which depends on measuring the difference value in the ratio spectrum, where the difference between 291 and 313 nm was used for the determination of folic acid, while the difference between 305 and 319 nm was selected for the estimation of para-aminobenzoic acid; on the other hand, pteroic acid can be determined using the first derivative of ratio spectra spectrophotometric method at 262 nm. Method B is the double-divisor spectrophotometric method (DDSM); this method is based on using the ratio spectrum obtained by the division of the spectrum of ternary mixture by the spectrum of binary mixture containing two of the three mentioned components, and in this method, folic acid, para-aminobenzoic acid, and pteroic acid were measured at 242, 313, and 258 nm, respectively. Method C is the mean-centering of ratio spectra spectrophotometric method (MCR); in this method, folic acid, para-aminobenzoic acid, and pteroic acid can be measured using the mean-centered second ratio spectra amplitudes at 317–318 (peak to peak), 264–265 (peak to peak), and 232 nm, respectively. Lastly, method D is a TLC—densitometric one that depends on the separation and quantification of the mentioned components on TLC silica gel 60 F254 plates, using methanol—iso-propanol—water—acetic acid (9:0.5:0.5:0.2, by volume) as the developing system, followed by densitometric measurement of the separated bands at 280 nm. Method validation was carried out according to the International Conference on Harmonisation (ICH) guidelines, and the proposed methods were successfully applied to the analysis of folic acid in pharmaceutical formulations, where no interference from additives has been found. The results obtained by the proposed methods were statistically compared with those obtained by the official reversed-phase high-performance liquid chromatography (RP-HPLC) method, in which no significant difference was observed.

VALIDATED SPECTROPHOTOMETRIC METHODS FOR SIMULTANEOUS DETERMINATION OF BRINZOLAMIDE AND TIMOLOL MALEATE IN THEIR PURE FORM AND OPHTHALMIC PREPARATION

Four sensitive, simple and precise spectrophotometric methods for the simultaneous determination of brinzolamide (BRZ) and timolol maleate (TML) in their pharmaceutical formulation are developed and validated. Method A is the ratio difference spectrophotometric method (RDSM) which can measure the difference in amplitudes between 251 and 265 nm of ratio spectrum for brinzolamide and between 285 and 306 nm of ratio spectrum for timolol. Method B is the mean centering of ratio spectra method (MCR) by measuring the peak amplitude at 252 nm for brinzolamide and 304 nm for timolol. Method C is area under the curve (AUC) in which the area under the curves for brinzolamide and timolol were selected over the ranges of (260-265) and (282-288) nm. Method D is the bivariate method (BVM) which depended on the quantitative evaluation of the absorbances at 265 and 285 nm, respectively. Beer’s Lambert’s law for the adopted methods were obeyed over the concentration range of 6-36 µg/mL for Brinzolamide and 6-42 µg/mL for Timolol. The obtained results were statistically compared with those obtained by the reported methods, showing no significant difference. The suggested methods were validated according to the ICH guidelines and were successfully applied for simultaneous determination of brinzolamide and timolol maleate in bulk drug and in their ophthalmic preparation.

Comparative study of six sequential spectrophotometric methods for quantification and separation of ribavirin, sofosbuvir and daclatasvir: An application on Laboratory prepared mixture, pharmaceutical preparations, spiked human urine, spiked human plasma, and dissolution test

In accordance with International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines, six novel, simple and precise sequential spectrophotometric methods were developed and validated for the simultaneous analysis of Ribavirin (RIB), Sofosbuvir (SOF), and Daclatasvir (DAC) in their mixture without prior separation steps. These drugs are described as co-administered for treatment of Hepatitis C virus (HCV). HCV is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma) and lymphomas in humans. These techniques consisted of several sequential steps using zero, ratio and/or derivative spectra. DAC was first determined through direct spectrophotometry at 313.7 nm without any interference of the other two drugs while RIB and SOF can be determined after ratio subtraction through five methods; Ratio difference spectrophotometric method, successive derivative ratio method, constant center, isoabsorptive method at 238.8 nm, and mean centering of the ratio spectra (MCR) at 224 nm and 258 nm for RIB and SOF, respectively. The calibration curve is linear over the concentration ranges of (6–42), (10–70) and (4–16) μg/mL for RIB, SOF, and DAC, respectively. This method was successfully applied to commercial pharmaceutical preparation of the drugs, spiked human urine, and spiked human plasma. The above methods are very simple methods that were developed for the simultaneous determination of binary and ternary mixtures and so enhance signal-to-noise ratio. The method has been successfully applied to the simultaneous analysis of RIB, SOF, and DAC in laboratory prepared mixtures. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Novel univariate and multivariate regression methods for the simultaneous analysis of ternary mixture of 1, 4-benzodiazepines in dosage forms and human urine

In this paper, novel univariate and multivariate regression model updating methods were developed and validated for the simultaneous determination of ternary mixture of bromazepam, diazepam and clonazepam. The univariate methods used are the mean centering of ratio spectrophotometric method and iso-absorptive point coupled with ratio-subtraction and ratio difference spectrophotometric method. Linearity, ranges, precision and accuracy of these methods were determined. The multivariate methods adopted are the principal component regression and partial least-squares. These models were estimated using nineteen mixtures as calibration set and six mixtures as validation set. The minimum root square error of predication were 0.1215 and 0.0568 for BMZ, 0.0598 and 0.0712 for DIZ and 0.0867 and 0.0753 for CNP by PLS and PCR respectively. PCR and PLS methods were successfully applied for the analysis of BMZ, DIZ and CNP in their dosage forms. Content uniformity testing of the studied pharmaceutical tablets by PLS and PCR was also determined. MCR, IPRSRD and PLS model updating enabled the determination of BMZ, DIZ and CNP in spiked human urine. Moreover, PLS model updating was applied to drug-dissolution rate testing of BMZ and DIZ in their commercial tablets. The obtained results were statistically compared with those obtained by reported methods giving a conclusion that there is no significant difference regarding accuracy and precision.

Analytical investigation of different mathematical approaches utilizing manipulation of ratio spectra

This work represents a comparative study of different approaches of manipulating ratio spectra, applied on a binary mixture of ciprofloxacin HCl and dexamethasone sodium phosphate co-formulated as ear drops. The proposed new spectrophotometric methods are: ratio difference spectrophotometric method (RDSM), amplitude center method (ACM), first derivative of the ratio spectra (1DD) and mean centering of ratio spectra (MCR). The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitations and sensitivity. The obtained results were statistically compared with those obtained from the reported HPLC method, showing no significant difference with respect to accuracy and precision.

Complete Evaluation of Recent Smart Spectrophotometric Methods for Determination of Highly Overlapped Combinations Through Their Zero Order Profiles

In recent years, several smart spectrophotometric methods were developed for determination of highly overlapped binary mixtures by obtaining the zero order spectrum for each analyte. The validity of selected three spectrophotometric methods were tested for determination of anti-hypertensive combinations containing Hydrochlorothiazide (HCTZ). The first combination was Benazepril (BENZ) and Hydrochlorothiazide (I), the second combination was Olmesartan (OLM) and Hydrochlorothiazide (II), while the third combination was Irbesartan (IRB) and Hydrochlorothiazide (III). The first method tested was the ratio difference spectrophotometric method for determination of (I) and (II). The second method was the constant center method for determination of (I) and (II). The third method was the absorption factor (AF) for zero order and amplitude factor (P-F) for first order spectrum for determination of (III). Also, a fourth stability indicating spectrophotometric method was developed for determination of BENZ and HCTZ in presence of Benazeprilate (BENZT) which is the main degradation product of BENZ. ICH guidelines were followed for validation of the methods. The methods were compared to reported methods where no significant differences were found.

Different Spectrophotometric Methods for Quantitative Determination of Benztropine Mesylate in Presence of Its Carcinogenic Degradation Product

Three simple, accurate, sensitive and selective spectrophotometric stability-indicating methods for determination of Benztropine Mesylate (BNZ) in the presence of its hepatotoxic and carcinogenic degradation product; Benzophenone (BPH); were developed and validated without preliminary separation. The developed spectrophotometric methods are; first derivative, first derivative of ratio spectra and ratio difference were developed for the determination of BNZ in the presence of BPH in pure form and in pharmaceutical formulation. The most important advantage of this work is that it is the first time to develop spectrophotometric methods for determination of BNZ and its carcinogenic degradation product. BNZ was subjected to stress degradation conditions (acid, alkaline and oxidation), and the obtained degradate was confirmed to be BPH. Calibration curves of these methods are linear over the concentration ranges of 5-20 and 3-20 μg mL−1 for BNZ and BPH, respectively. Method (I); first derivative spectrophotometric method where BNZ was measured at 228.2 nm. Method (II); first derivative of ratio spectra spectrophotometric one where the overlapping spectra of BNZ and BPH were well resolved and BNZ was measured at peak amplitude 228.8 nm. Method (III); ratio difference spectrophotometric method which depends on measuring difference in peak amplitude values between two different wavelengths of the ratio spectrum at 224 and 234 nm for determination of BNZ. While BPH was determined by the first derivative at 245 NM without interference from BNZ. The proposed methods were successfully applied for determination of the studied drug in its pharmaceutical formulation. These methods were validated according to ICH guidelines. Results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by reported one using F and student’s t-tests showed no significant difference was obtained regarding both accuracy and precision.