Partial least-squares method in analysis by differential pulse polarography. Simultaneous determination of amiloride and hydrochlorothiazide in pharmaceutical preparations

Simultaneous spectrofluorometric analysis of tablets containing hydrochlorothiazide combined with timolol maleate or amiloride hydrochloride

Green and sensitive spectrofluorometric methods have been developed and validated for the determination of timolol maleate (TML)/hydrochlorothiazide (HCT) and amiloride hydrochloride (AMH)/hydrochlorothiazide in tablets. The proposed spectrofluorometric procedures were found to be linear in the range of 4-12, 5-35 and 0.025-0.2 mg L-1 for HCT, TML and AMH, resp. The excitation and emission wavelengths for HCT, TML and AMH at room temperature were 270 and 375, 295 and 435, 330 and 415 nm, resp. The methods were validated with respect to ICH guidelines. The AMH showed higher sensitivity with lower values of LOD and LOQ values compared to HCT and TML. The proposed methods were applied to two pharmaceutical formulations; the method for HCT and AMH has proven as reliable assaying method, whereas the method for TML, when combined with HCT, is applicable to screening semi-quantitative analyses.

Development and Validation of Two Chromatographic Methods for Simultaneous Determination and Quantification of Amiloride Hydrochloride, Hydrochlorothiazide, and Their Related Substances, in Pure and Tablet Forms

Background

Amiloride hydrochloride (AM) is a potassium sparing diuretic, while hydrochlorothiazide (HCZ) is the protype of thiazide diuretics. The combining of the studied drugs exhibits a synergistic effect. Moreover, HCZ prevents the potassium depletion side effect caused by AM.

Objective

Two accurate and precise simultaneous chromatographic separation methods were promoted and investigated to quantify AM, HCZ, official impurities of HCZ (cholorothiazide and salamide), and the official impurities of AM (methyl 3, 5-diamino-6-chloropyrazine-2-carboxylate).

Methods

The components of the quintuple mixture were quantified by two methods. The first method was high-performance thin layer chromatography (HPTLC), where exemplary separation was achieved on silica gel HPTLC F254 plates at the stationary phase using ethyl acetate–ethanol–ammonia solution (8 + 2 + 0.2, v/v) as a developing system. Scanning of bands at 273 nm was done. The second method was a reversed-phase chromatography (RP-HPLC) method using C18 (4.6 × 100 mm) column and mobile phase comprising 0.1% phosphoric acid solution–acetonitrile (90 + 10, v/v) with UV determination at 273 nm. Adjustment of the flow rate at 1 mL/min and pH at 3.6 was performed.

Results

Regarding RP-HPLC, optimum separation of the quintuple mixture was achieved within just five minutes. According to HPTLC, symmetric and sharp peaks were separated on the resulted chromatogram. Validity of the introduced methods was investigated by applying international conference on harmonization (ICH) guidelines.

Conclusions

The methods were successfully applied for assays of the studied drugs in their pure and tablet forms. No significant difference was revealed through application of statistical comparison between results of the suggested methods and those of the reported method regarding both accuracy and precision.

Simultaneous Determination of Hydrochlorothiazide in Combination with Some Antihypertensive Drugs in The Presence of Its Main Impurities in Pure Form and Pharmaceutical Formulations

Background:

Hydrochlorothiazide (HCTZ) is potent diuretic that is used alone or in combination with other drugs such as labetalol (Lab) (mixtures Ι) or nebivolol (Neb) (mixtures ΙΙ) to control moderate to sever hypertension.

Introduction:

This paper demonstrates the establishment of different validated spectrophotometric and chemometric methods for simultaneous estimation of these mixtures in pure form and pharmaceutical formulations in the presence of HCTZ related impurities in quality control laboratories.

Methods:

(A) Derivative method (D3) of Lab and HCTZ and its related impurities at 245.3nm and 278.5nm respectively, (D1) of Neb and HCTZ at 294.2nm and 282.2nm, respectively. (B) First derivative of ratio spectra method (DD 1) of Lab at 244.3nm, HCTZ at 261.2nm and 275.4nm, while at 294nm for Neb and 269.4nm for HCTZ. (C) Ratio difference method which depends on measuring the distinction between the amplitudes of ratio spectra at 240nm and 288.3nm for Lab and at 270.1nm and 277.4nm for HCTZ for mixture Ι while at 290.4nm and 299.2nm for Neb and at 232.2nm and 254nm for HCTZ for mixture ΙΙ. (D) Mean centering of ratio spectra (MC) and (E) partial least squares regression (PLS) and principal component regression (PCR).

Results:

These methods were applied over concentration ranges of 10-100 µg/ml, 10-75 µg/ml and 2.5- 25 µg/ml of Lab, Neb and HCTZ, respectively. Methods were validated according to ICH guidelines and statistical comparison of results of reported and proposed methods revealed no difference.

Conclusion:

The methods were successfully used for the frequent analysis of selected mixtures in quality control laboratories.

Univariate and Multivariate Analysis of Phosphorus Element in Fertilizers Using Laser-Induced Breakdown Spectroscopy

Rapid detection of phosphorus (P) element is beneficial to the control of compound fertilizer production process and is of great significance in the fertilizer industry. The aim of this work was to compare the univariate and multivariate analysis of phosphorus element in compound fertilizers and obtain a reliable and accurate method for rapid detection of phosphorus element. A total of 47 fertilizer samples were collected from the production line; 36 samples were used as a calibration set, and 11 samples were used as a prediction set. The univariate calibration curve was constructed by the intensity of characteristic line and the concentration of P. The linear correlation coefficient was 0.854 as the existence of the matrix effect. In order to eliminate the matrix effect, the internal standardization as the appropriate methodology was used to increase the accuracy. Using silicon (Si) element as an internal element, a linear correlation coefficient of 0.932 was obtained. Furthermore, the chemometrics model of partial least-squares regression (PLSR) was used to analysis the concentration of P in fertilizer. The correlation coefficient was 0.977 and 0.976 for the calibration set and prediction set, respectively. The results indicated that the LIBS technique coupled with PLSR could be a reliable and accurate method in the quantitative determination of P element in complex matrices like compound fertilizers.

Quantitative Determination of Cd in Soil Using Laser-Induced Breakdown Spectroscopy in Air and Ar Conditions

Rapid detection of Cd content in soil is beneficial to the prevention of soil heavy metal pollution. In this study, we aimed at exploring the rapid quantitative detection ability of laser- induced breakdown spectroscopy (LIBS) under the conditions of air and Ar for Cd in soil, and finding a fast and accurate method for quantitative detection of heavy metal elements in soil. Spectral intensity of Cd and system performance under air and Ar conditions were analyzed and compared. The univariate model and multivariate models of partial least-squares regression (PLSR) and least-squares support vector machine (LS-SVM) of Cd under the air and Ar conditions were built, and the LS-SVM model under the Ar condition obtained the best performance. In addition, the principle of influence of Ar on LIBS detection was investigated by analyzing the three-dimensional profile of the ablation crater. The overall results indicated that LIBS combined with LS-SVM under the Ar condition could be a useful tool for the accurate quantitative detection of Cd in soil and could provide reference for environmental monitoring.

Research on the Optimum Water Content of Detecting Soil Nitrogen Using Near Infrared Sensor

Nitrogen is one of the important indexes to evaluate the physiological and biochemical properties of soil. The level of soil nitrogen content influences the nutrient levels of crops directly. The near infrared sensor can be used to detect the soil nitrogen content rapidly, nondestructively, and conveniently. In order to investigate the effect of the different soil water content on soil nitrogen detection by near infrared sensor, the soil samples were dealt with different drying times and the corresponding water content was measured. The drying time was set from 1 h to 8 h, and every 1 h 90 samples (each nitrogen concentration of 10 samples) were detected. The spectral information of samples was obtained by near infrared sensor, meanwhile, the soil water content was calculated every 1 h. The prediction model of soil nitrogen content was established by two linear modeling methods, including partial least squares (PLS) and uninformative variable elimination (UVE). The experiment shows that the soil has the highest detection accuracy when the drying time is 3 h and the corresponding soil water content is 1.03%. The correlation coefficients of the calibration set are 0.9721 and 0.9656, and the correlation coefficients of the prediction set are 0.9712 and 0.9682, respectively. The prediction accuracy of both models is high, while the prediction effect of PLS model is better and more stable. The results indicate that the soil water content at 1.03% has the minimum influence on the detection of soil nitrogen content using a near infrared sensor while the detection accuracy is the highest and the time cost is the lowest, which is of great significance to develop a portable apparatus detecting nitrogen in the field accurately and rapidly.

RP-LC and HPTLC Methods for the Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Tablet Dosage Forms

Two new, rapid, precise, accurate and specific chromatographic methods were described for the simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage forms. The first method was based on reversed phase liquid chromatography using an Eurosphere 100 RP C18 column (250 x 4.6 mm ID, 5 mum). The mobile phase was methanol-0.05% o-phosphoric acid (60:40 v/v) at a flow rate of 1.0 mL min(-1). Commercially available tablets and laboratory mixtures containing both drugs were assayed and detected using a UV detector at 270 nm. The second method involved silica gel 60 F(254) high performance thin layer chromatography and densitometric detection at 254 nm using acetonitrile-ethyl acetate-glacial acid (7:3:0.4 v/v/v) as the mobile phase. Calibration curves ranged between 200-600 and 125-375 ng spot(-1) for olmesartan and hydrochlorothiazide, respectively.

Simultaneous determination of amiloride and hydrochlorothiazide in human plasma by liquid chromatography/tandem mass spectrometry with positive/negative ion-switching electrospray ionisation

A new method for simultaneous determination of amiloride and hydrochlorothiazide by liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) operated in positive and negative ionization switching mode was developed and validated. Protein precipitation with acetonitrile was selected for sample preparation. The analytes were separated on a Phenomenex Curosil-PFP (250x4.6 mm, 5 microm) column by a gradient elution with a mobile phase consisting of 0.15% formic acid solution containing 0.23% ammonium acetate and methanol pumped at a flow rate of 1.0 mL.min(-1). Rizatriptan was used as the internal standard (IS) for quantification. The determination was carried out on a Waters Quattro-micro triple-quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode using the following transitions monitored simultaneously: positive m/z 230-->171 for amiloride, m/z 270-->158 for rizatriptan, and negative m/z 296-->205 for hydrochlorothiazide. The lower limits of quantification (LLOQs) were 0.1 and 1.0 ng.mL(-1) for amiloride and hydrochlorothiazide, respectively, which were lower than other published methods by using ultraviolet (UV), fluorimetric or mass spectrometric detection. The intra- and inter-day precision and accuracy were studied at three different concentration levels and were always better than 15% (n=5). This simple and robust LC/MS/MS method was successfully applied to the pharmacokinetic study of compound amiloride and hydrochlorothiazide tablets in healthy male Chinese volunteers.

Using on-line solid phase extraction for determination of amiloride in human urine by sequential injection technique

This presented paper deals with a new methodology for the direct determination of amiloride in human urine. The methodology described is based on the sequential injection analysis technique (SIA) coupled with solid phase extraction (SPE) microcolumn. SPE microcolumn was used for selective retention of amiloride, while the urine matrix components were eluted with water carrier flow to the waste. Due to the acid-basic and polarity properties of amiloride molecule and principles of ion-exchange chromatography, it was possible to retain amiloride on the ion-exchange sorbent (SPE BAKER WCX-carboxy group). Eluting solution was 0.01 M HNO3+0.1 M KCl, flow rate 20 microl s(-1). The fluorescence detection of amiloride was performed at lambda(em) 385 nm (secondary filter). Recovery was found in the range 96.8-99.4% for 10 times diluted urine, linearity of determination in the range 0.5-100 microg ml(-1) (r=0.998), and 3sigma limit of detection (LOD) was 0.05 microg ml(-1). The whole procedure comprising raw sample pre-treatment, analyte detection and column reconditioning took 8 min. The proposed SIA-SPE method has been applied for direct determination of amiloride in human urine.

HPLC and chemometric assisted spectrophotometric methods for simultaneous determination of diprophylline, phenobarbitone and papaverine hydrochloride

Three methods are developed for the simultaneous determination of diprophylline (DP), phenobarbitone (PH) and papaverine hydrochloride (PP). The chromatographic method depends on a high performance liquid chromatographic (HPLC) separation on a reversed-phase C18 column with a mobile phase consisting of 0.02 M potassium dihydrogen phosphate, pH 3.5--acetonitrile (55:45 v/v). Quantitation was achieved with UV detection at 210 nm based on peak area. The other two chemometric methods applied were principal component regression (PCR) and partial least squares (PLS-1). These approaches were successfully applied to quantify the three drugs in the mixture using the information included in the UV absorption spectra of appropriate solutions in the range 215-245 nm with the intervals Delta lambda = 0.2 nm. The calibration PCR and PLS-1 models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over laboratory-prepared mixtures and pharmaceutical preparations. The PCR and PLS-1 methods require neither any separation step, nor any priori graphical treatment of the overlapping spectra of the three drugs in a mixture. The results of PCR and PLS-1 methods were compared with HPLC method obtained in pharmaceutical formulation and a good agreement was found.

FI-chemiluminometric study of thiazides by on-line photochemical reaction

The present manuscript deals with a simple and sensitive flow-injection method for the chemiluminescent determination of thiazides. The method is based on the on-line photodegradation and chemiluminescent determination of the resulting photo-fragments. The on-line photodegradation is performed in basic medium by using a photoreactor consisting of a 550cm long x 0.8mm ID piece of PTFE tubing helically coiled around an 8W low-pressure mercury lamp. The determination of the photo-irradiated thiazides is performed by a chemiluminescent oxidative reaction with Ce(IV) in sulphuric acid medium. A heterogeneous group of thiazides (indapamide, metolazone, hydroflumethiazide, chlorthalidone and bendroflumethiazide) has been studied. Hydrochlorothiazide was selected as a test substance. The "on-line" photochemical reaction approach allows the sensitive chemiluminescent determination of thiazides which do not present native chemiluminescence in the absence of sensitizers such as Rhodamine 6G. Linear calibration graphs were typically over the range 0.5-12 microgml(-1) (indapamide, metolazone, hydroflumethiazide and chlorthalidone); and over the range 0.5-5 microgml(-1) (hydrochlorothiazide). Limits of detection ranged between 0.005 microgml(-1) (hydrochlorothiazide) and 0.06 microgml(-1) (bendroflumethiazide). The relative standard deviation for the test substance was 2.0% for 2 microgl(-1) of the drug (n = 11) and the throughput was 65 h(-1) in all cases. The assessment of the photodegradation step on the molecular structure of thiazides was established by recording UV and fluorimetric spectra. The viability of the on-line photoinduced fluorescent determination of hydroflumethiazide and bendroflumethiazide was confirmed. The method was also applied to the determination of hydrochlorothiazide in commercially available formulation.

Electrochemical behavior and determination of amiloride drug in bulk form and pharmaceutical formulation at mercury electrodes

The polarographic behavior of amiloride hydrochloride has been studied in Britton-Robinson buffers of pH 1.9-11. In acidic medium at Ph< or =2, the dc-polarograms exhibited a single 4-electron cathodic irreversible wave, while at pH values >2, a second two-electron irreversible cathodic wave appeared at a more negative potential. The single or first wave may be attributed to the cleavage of the double bond of the -CH=NH of the imidino amide group with the release of NH(3). While the second wave may be due to the saturation of the C=O of the carboxamide moiety. A polarographic procedure of suffocate sensitivity for the determination of bulk amiloride drug in Britton-Robinson buffer at pH 2 is described. The calibration graph was obtained over the concentration range 2.5 x 10(-5) to 2.5 x 10(-4) M amiloride. The limits of detection (LOD) and quantitation (LOQ) of the procedure were 1 x 10(-5) and 3.3 x 10(-4) M bulk amiloride, respectively. Moreover, a differential-pulse adsorptive cathodic stripping voltammetric procedure has been described to assay of the drug at lower concentration levels. The optimal conditions were: E(acc) = -0.9V, t(acc)=30 s, scan rate=20mV, pulse-height=90 mV and Britton-Robinson buffer of pH 8. The calibration graph was obtained over the concentration range 2 x 10(-8) to 1 x 10(-6) M for bulk amiloride. Both procedures were successfully applied to the determination of amiloride in tablets without the necessity for sample pretreatment or any time-consuming extraction or evaporation steps prior to the drug analysis.

Behavior and quantification studies of amiloride drug using cyclic and square-wave adsorptive stripping voltammetry at a mercury electrode

The cyclic voltammograms of amiloride at the hanging mercury drop electrode showed a single well-defined four-electron irreversible cathodic peak in Britton-Robinson (B-R) buffer of pH 2. At higher pH values (pH > or =3), two irreversible cathodic peaks corresponding to the transfer of four (first peak) and two (second peak) electrons, were obtained The peak potentials were shifted to more negative values on the increase of pH of the medium, implying the involvement of protons in the electrode reaction and that the proton-transfer reaction precedes the proper electrode process. The 4-electron single peak (pH 2) or the first peak (pH > or = 3) may be attributed to the cleavage of the -CH=NH double bond of the N-imidino amide group with the release of NH(3) molecule. While the second peak may be due to the saturation of the C?O double bond of the carboxamide moiety. Based on the interfacial adsorptive character of the drug onto the mercury electrode surface, a simple, sensitive and low cost square-wave adsorptive cathodic stripping (SWAdCS) voltammetric procedure was optimized for analysis of the drug. The optimal operational conditions of the proposed procedure were: accumulation potential E(acc)= -0.7 V, accumulation time t(acc)= 60-65s, scan increment= 10 mV, pulse-amplitude = 50-60 mV, frequency =120 Hz using a B-R buffer of pH 8 as a supporting electrolyte. The linear concentration range was found to be 2 x 10(-9) to 2 x 10(-7) M amiloride with limits of detection (LOD) and quantitation (LOQ) of 1.9 x 10(-10) and 6.3 x 10(-10) M, respectively. The procedure was successfully applied for determination of amiloride in pharmaceutical formulation and spiked in human serum. The LOD and LOQ of amiloride spiked in human serum were 5.7 x 10(-10) and 1.9 x 10(-9) M amiloride, respectively. The procedure did not require sample pretreatment or any time-consuming extraction or evaporation steps, other than deproteinization and then centrifugal separation of protein from serum sample prior to analysis of the drug.

Simultaneous determination of moexipril hydrochloride and hydrochlorothiazide in tablets by derivative spectrophotometric and high-performance liquid chromatographic methods

Two new simple and selective assay methods have been presented for the binary mixtures of moexipril hydrochloride (MOEX) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations. The first method depends on second-derivative ultraviolet spectrophotometry with zero-crossing measurements at 215 and 234 nm for MOEX and HCTZ, respectively. The assay was linear over the concentration ranges 1.0-11.0 microg ml(-1) for MOEX and 0.5-9.0 microg ml(-1) for HCTZ. The determination limits for MOEX and HCTZ were found to be 1.0 and 0.5 microg ml(-1), respectively; while the detection limits were 0.2 microg ml(-1) for MOEX and 0.1 microg ml(-1) for HCTZ. The second method was based on isocratic reversed-phase liquid chromatography by using a mobile phase acetonitrile-20 mM phosphate buffer (pH 4.0) (50:50, v/v). Lisinopril was used as an internal standard (IS) and the substances were detected at 212 nm. The linearity range for both drugs was 0.5-12.0 microg ml(-1). The determination and detection limits were found to be 0.100 and 0.010 microg ml(-1) for MOEX and 0.025 and 0.005 microg ml(-1) for HCTZ, respectively. The proposed methods were successfully applied to the determination of these drugs in synthetic mixtures and commercially available tablets with a high percentage recovery, good accuracy and precision.

Simultaneous determination of amiloride hydrochloride and hydrochlorothiazide in synthetic samples and pharmaceutical formulations by multivariate analysis of spectrophotometric data

The use of multivariate spectrophotometric calibration for the simultaneous analysis of synthetic samples and commercial tablet preparations containing hydrochlorothiazide (HCT) and amiloride hydrochloride (AMH) is reported. Partial least squares (PLS-1) analysis of electronic absorption spectral data allowed the rapid and accurate resolution of mixtures in which the analyte ratios were approximately 10:1, without the need of a previous separation step and without interference from other sample constituents. The method, validated by the analysis of synthetic mixtures of both drugs, where accuracy over the linear working range as well as inter- and intra-assay precision were determined, was used in the concentration ranges of 21.7-30.4 mg l(-1) for HCT and 1.8-3.0 mg l(-1) for AMH. The proposed method was successfully applied to the evaluation of the stability of the stock solutions of the analytes in MeOH-H(2)O and to the elaboration of drug dissolution profiles of commercial tablets, results being concordant with those furnished by the USP technique. The method was also employed for the determination of drug content in two different pharmaceutical formulations, providing results that were in excellent agreement with those obtained by HPLC.

Determination of triamterene by transitory retention in a continuous flow solid phase system with fluorimetric transduction

A rapid and simple flow-through solid phase espectrofluorimetric system (sensor) is described in this paper for the determination of the diuretic triamterene at ng ml(-1) level in physiological fluids and in pharmaceuticals. This sensor is based on the transitory retention of the analyte on the cationic ion-exchanger gel Sephadex SP C-25 placed into a quartz flow-cell in the detection zone itself of a spectrofluorimeter and the continuous monitorization of its intrinsic fluorescence. The spectrofluorimeter was tuned at 240 (excitation) and 440 nm (emission). A transitory signal was obtained because the carrier solution used also eluted the analyte from the sensing zone and no derivatization reactions were needed. Triamterene could be determined in the concentration ranges of 10-400 and 2.5-80 ng ml(-1) with detection limits of 0.95 and 0.17 ng ml(-1) for 300 and 1000 microl of sample volume, respectively. The relative standard deviations (RSD) for ten independent determinations and at three concentration levels of standards solutions were lower than 0.90 for 300 microl and 0.45 for 1000 microl. The RSDs for the determination of triamterene in serum samples and pharmaceuticals were lower than 3.3 and 2.6%, respectively. The method was satisfactorily applied to the determination of triamterene in human serum and pharmaceuticals.

Simultaneous determination of fosinopril and hydrochlorothiazide in pharmaceutical formulations by spectrophotometric methods

Three new spectrophotometric procedures for the simultaneous determination of fosinopril and hydrochlorothiazide are described. The first method, derivative-differential spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first-order (DeltaD(1)) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 227.6 and 276.4 nm, respectively. The second method, depends on the application ratio spectra derivative spectrophotometric method to resolve the interferance due to spectral overlapping. The analytical signals were measured at 237.9, 243.8 nm for fosinopril and 262.4, 269.3 and 278.6 nm for hydrochlorothiazide in the binary mixture, in the first derivative of the ratio spectra of the mixture solutions in methanol. Calibration graphs were established for 4.0-50.0 microg ml(-1) fosinopril and 2.0-14.0 microg ml(-1) hydrochlorothiazide in binary mixture. The third method, absorbance ratio method, the determination of fosinopril and hydrochlorothiazide was performed by using the absorbances read at 210.0, 219.5 and 271.7 nm in the zero-order spectra of their mixture. The developed methods were compared with absorbance ratio method. Application of the suggested procedures were successfully applied to the determination of this compound in synthetic mixtures and in pharmaceutical preparations, with high percentage of recovery, good accuracy and precision.

A spectrophotometric-partial least squares (PLS-1) method for the simultaneous determination of furosemide and amiloride hydrochloride in pharmaceutical formulations

A numerical method, based on the use of spectrophotometric data coupled to PLS-1 multivariate calibration, is reported for the simultaneous determination of furosemide and amiloride hydrochloride in synthetic samples and commercial tablets. The method was applied in the concentration ranges of 8.0-13.0 mg l(-1) for furosemide and 1.0-1.6 mg l(-1) for amiloride hydrochloride. Its accuracy and precision were determined, and it was validated by the analysis of synthetic mixtures of both drugs. The method was successfully applied to the quantitation of furosemide and amiloride hydrochloride in three different pharmaceutical formulations, providing results in agreement with those obtained by HPLC. It allowed the rapid, accurate and precise simultaneous estimation of the concentration of both analytes of interest in spite of their important spectral overlap, high concentration relationship and the presence of small amounts of different, unmodelled, absorbing excipients.