O. Hernández

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

A method is proposed for the simultaneous determination of amiloride and hydrochlorothiazide in pharmaceutical preparations using differential pulse polarography in the presence of oxygen and partial least-squares (PLS) for calibration. The experimental variables that influence the system (pulse height, pulse delay and pH) are optimized by using response surface methodology to relate the variables to be optimized to the mean relative square error of prediction (RSEP), which is minimized. The proposed method was used to determine the two drugs in synthetic mixtures and pharmaceutical preparations. The results were validated by comparison with HPLC, with errors less than 10% in all instances.

Application of PLS regression to fluorimetric data for the determination of furosemide and triamterene in pharmaceutical preparations and triamterene in urine

Multivariate calibration methods that use fluorescence data for the simultaneous determination of furosemide and triamterene were developed. One of the most salient advantages of them is that the vast amount of information provided by the whole spectrum of the sample is not required. This makes analyses simple and fast. The methods require selecting chemometric parameters such as the specific spectral region and number of factors to be used. Both spectral region and number of factors are selected, simultaneously, by minimising the prediction residual error sum of squares (PRESS). The proposed methods were used for the simultaneous determination of the two drugs in real samples (pharmaceutical preparations) with no excipient separation pre-treatment, with furosemide and triamterene contents of 1.68E-3 to 4.31E-2 and 1.03E-3 to 3.12E-2mugml(-1), respectively; as well as that of triamterene at concentrations of 5.00E-4 to 5.80E-3mugml(-1) in urine samples. The ability to construct the calibration validation sets directly from the urine samples itself avoids the need to consider matrix interferences or to pre-treat the sample and/or separate some analytes The results were quite good in all cases.

Simultaneous Spectrophotometric Determination of Hydrochlorothiazide and Pharmaceutical Preparations

Abstract We developed three methods for the simultaneous determination of amiloride (AMI) and hydrochlorothiazide (HCT): zero-crossing, derivative quotient spectra with normalized divisor and multiple linear regression (MULTIC) methods. The two first methods use the derivative spectrophotometry, and the last one uses the absorbance measurement. The three methods were used to determine both compounds in synthetic mixtures and pharmaceutical preparations with errors less than 5% and 15%, respectively.

Evaluation of multicomponent flow-injection analysis data by use of a partial least squares calibration method

Abstract This paper reports on the use of a flow-injection analysis technique for the simultaneous spectrophotometric resolution of binary and ternary mixtures with the aid of a multivariate calibration method, and its application to the simultaneous determination of Co(II), Cu(II) and Zn(II) with 2-carboxyl-2-hydroxy-5-sulfoformazylbenzene (Zincon) over the concentration range 0.397–1.590, 0.268–1.879 and 0.240–1.612 μg/ml, respectively. Multicomponent analysis was implemented by using a modified version of the partial least squares program. The influence of various chemical and FIA variables affecting the reaction was evaluated. The proposed method was successfully applied to the determination of cobalt, copper and zinc in synthetic mixtures; copper and zinc in blood serum; and cobalt, copper and zinc in veterinary formulations.

Multicomponent analysis by flow injection using a partial least-squares model. Determination of copper and zinc in serum and metal alloys

A partial least-squares multivariate calibration method for the resolution of mixtures of metal ions from the spectra of the complexes produced in a flow injection (FI) system has been developed. The method has been applied to the simultaneous determination of CuII and ZnII with 4-(4′-methyl-2′-thiazolylazo)-2-methylresorcinol. The reagent exhibits a high absorbance and its spectrum strongly overlaps with the spectra of the complexes that it forms with copper and zinc ions. Chemical and FI variables influencing the system have been optimized and the proposed method validated on the determination of Cu and Zn in blood serum and metal alloys.

Use of partial least-squares regression for multicomponent determinations based on kinetic spectrofluorimetric data. Simultaneous determination of canrenone and spironolactone in urine

A new spectrofluorimetric method for the simultaneous determination of canrenone and spironolactone in urine is proposed. The method is based on the different rates at which the two analytes react with hot sulfuric acid to form a trienone. The kinetic spectrofluorimetric data are processed by partial least-squares regression. The effects of sulfuric acid concentration and temperature on the system under study were also evaluated and the optimum values for carring out the reaction were 50% and 50 degrees C, respectively. The method was checked by analyzing urine samples that they contained both diuretics. The accuracy and the precision of the method were tested. The relative standard errors in the quantification of each analyte in all tested samples were 3.69 and 3.59%. The proposed method was validated by comparison with a high performance liquid chromatographic method for urine samples.

Characterization of toasted cereal flours from the Canary Islands (gofios)

In this work, different types of gofio produced in the Canary Islands were characterized on the basis of physico-chemical parameters as well as spectral features. An overall of 7 physico-chemical parameters (moisture, ash, pH, Cu, Fe, Mn and Zn) were determined in 64 samples from different cereals and legumes, and IR spectra of all samples were registered. The chemometric processing of both, metal ions contents determined by atomic absorption spectrophotometry, and the MIR spectra, with various techniques including cluster analysis, principal component analysis, and discriminant analysis enabled the accurate characterization and classification of the gofio samples according to the grain used in their obtaining process.

Simultaneous kinetic spectrophotometric determination of spironolactone and canrenone in urine using partial least-squares regression

A method is proposed for the simultaneous determination of spironolactone and canrenone in urine based on the different rates at which they react with sulphuric acid to yield a trienone. Kinetic spectrophotometric data are processed by partial least-squares (PLS) regression. The optimum sulphuric acid concentration and temperature are determined from response surfaces, using PLS methodology to relate both variables to the relative square error of prediction (RSEP, the parameter to be minimized). The relative errors made in the quantitation of each diuretic by the proposed method are less than 5% and the overall error, as RSEP, ranges from 1.06 and 1.44%.

Selection of Wavelength Range and Number of Factors to be Used in the PLS Treatment of Spectrophotometric Data

Abstract A procedure for selection of wavelength range and number of factors to be used in partial least square calibration that involves the calculation of prediction residual sum of squares (PRESS) in different conditions is proposed. The best model takes into account the minimum PRESS value that does not show significant differences with respect to the corresponding model with fewer factors. The ability of the proposed method to minimize errors in partial least squares (PLS) prediction is demonstrated by applying it to the resolution of phenytoine (DPH) and phenobarbital (PB) binary mixtures with errors less than 2.8%; the results are compared with those obtained using another wavelength selection procedure. The ensuing method, which was validated by high performance liquid chromatography (HPLC), also gives good results with real samples (pharmaceutical preparations).