H-point Standard Addition Method Research Articles

The determination of bisphenols contained in food-related products with increased accuracy provided by the H-point Standard Addition Method (HPSAM)-based methodology

The basic version of the H-point standard addition method and its variants have been developed with an increased number of measurement conditions (from two to five conditions allowed for differentiation of sensitivity). The methodology adapted to the signal increment and generalized versions was used for the determination of the harmful compounds from the group of bisphenols (bisphenol A, S, and F) using high-performance liquid chromatography with a diode array detector. This approach in theoretical and experimental studies allowed for obtaining high-quality results after eliminating all types of interference effects: multiplicative, additive, and nonlinear. The analysis of food-related samples, such as store receipts and canned food, confirmed the effectiveness of the developed methodology. The analytical results were distinguished by very good accuracy (RE<5 %, RV∼100 %) and precision (CV≤4 %). The approach can be successfully applied to various analytical systems (RGB model) and is characterized by a high greenness value (AGREE approach).

Spectrofluorimetric Method for Simultaneous Determination of Trimethoprim and Sulfamethoxazole with &lt;i&gt;O&lt;/i&gt;-phthaladehyde Reagent by H-point Standard Addition Method

Simultaneous spectrofluorometric method described for the determination of trimethoprim (TMP) and sulfamethoxazole (SMZ) in pure and pharmaceutical preparations using H-point standard addition method (HPSAM) according to the reaction of nanograms of drugs with O-phthaladehyde (OPA) reagent to forms highly fluorescence compounds. The formed fluorophore excitation and emission at 342 and 458 nm, respectively, for OPA-TMP compound, at 424 and 508 nm, respectively, for OPA-SMZ compound under basic condition (pH 9.8) in the presence of 2-mercabtoethanol. A simple and accurate HPSAM is reported to resolve the overlapping in the fluorescence spectrum of these two drugs without prior separation of samples. The linear range was 100–1200 ng/mL for TMP and 100–1100 ng/mL for SMZ. The LOD and LOQ were 16.64 and 36.80 ng/mL, as well as 15.76 and 33.88 ng/mL for TMP and SMZ, respectively. The relative standard deviations and recovery percentages were 0.641% and 101.29% for TMP as well as 0.558% and 100.96% for SMZ, respectively. The procedure has been applied successfully in various pharmaceutical preparations. It was discovered that the experimental F- and t-values at a 95% confidence level were no higher than the theoretical values, showing that the HPSAM method is accurate and valid.

طريقة القياس الطيفي المتزامن لتقدير كل من سيبروفلوكساسين وسيفاليكسين باستخدام طريقة H - point للاضافة المعيارية

طريقة سهلة وبسيطة ودقيقة لتقدير السبروفلوكساسين في وجود السيفاليكسين او العكس بالعكس في خليط منهما. طبقت الطريقة المقترحة بطريقة الاضافة القياسية لنقطة بنجاح في تقدير السبروفلوكساسين بوجود السيفاليكسين كمتداخل عند الاطوال الموجية 240-272.3 نانوميتر وبتراكيز مختلفة من السبروفلوكساسين 4-18 مايكروغرام . مل-1 وكذلك تقدير السيفاليكسين بوجود السبروفلوكساسين الذي يتداخل باطوال موجية 262-285.7 نانوميتر وبتراكيز مختلفة من السيفاليكسين 6-18 مايكروغرام . مل-1 في مزيج لهما. اظهرت النتائج عدم وجود اي تداخلات من قبل المواد المضافة التي تحتويها الادوية على هذه المركبات وضمن حدود كشف السبروفلوكساسين يساوي 0.1732 مايكروغرام . مل-1 وعقارالسيفاليكسين يساوي 0.4620 مايكروغرام . مل-1 . الانحراف القياسي النسبي المئوي اقل من 2% . تم تطبيق الطريقة بنجاح لتقدير العقارين في بعض المستحضرات الصيدلانية. تعتبر الطريقة المقترحة من الطرق القليلة التكلفة وعدم حاجتها الى ادخال الادوية في سلسلة من التفاعلات وتثبيت لظروف التفاعل لغرض تقديرها وانما تتم عن طريق تقدير الدواء بعد اذابته مباشرة في الماء المقطر بوجود العقار الاخر معه في مزيج وتعتبر من الطرق الناجحة في التقدير خاصة للادوية المتقاربة في طيف الامتصاص لها والتي من غير الممكن ايجاد طرق لفصل الدوائين وتقديرهما بصورة ادق من هذه الطريقة المقترحة دون التداخل وتاثير احدهما على الاخر. الطريقة المقترحة في هذا البحث كانت ناجحة في تقدير كل من السبروفلوكساسين والسيفاليكسين في مزيج لهما دون تداخل دواء مع الاخر.

Simultaneous Quantitative Determination of Ciprofloxacin and Hydrocortisone by H-Point Standard Addition Method

Ciprofloxacin (Cip) and hydrocortisone (Hyd) were simultaneously measured as hydrochloride and sodium succinate, respectively, using the H-point standard addition method (HPSAM). The approach can precisely identify Cip in the presence of Hyd with various analyte-to-interference ratios (5:5, 5:10, 10:5, 10:10) µg.mL-1, in mixed samples containing (1-5µg.ml-1) of Cip, at the wavelengths of (236 and 257) nm. In the same way, Hyd was analyzed in the presence of Cip in different analytes with an interference ratio of (5:5, 5:10, 10:5, 10:10) µg.mL-1, in mixed samples containing (1-5 µg.mL-1) of Hyd, at wavelengths of (266 and 278) nm. The satisfactory results show good reproducibility of the developed method (RSD equals 0.9735-1.6825 and 0.9692-1.7671 for Cip and Hyd, respectively). The results also show that the excipients had no influence on the assaying of the above drugs (Recovery, 98.87–101.73). The recommended technique has successfully been used to determine the Cip and Hyd in pharmaceutical composites simultaneously with an RSD range of (0.972 to 1.671) and (0.898 to 1.820) for Cip and Hyd, respectively.

Towards the assessment of exposure to bisphenols in everyday items with increased accuracy by the use of integrated calibration method (ICM)-based methodology

The most crucial purpose of the measurement is to obtain a reliable result that reflects the actual qualitative and/or quantitative features of the tested material. The overriding goal of analytical chemistry is to obtain accurate results after compensating of various interference effects as well as non-linear calibration dependence. A new approach based on an integrated calibration method (ICM) supported by H-point standard addition method (HPSAM) has been used to improve the quality of analytical results. The proposed methodological approach was extended using the step-by-step dilution procedure, and five measurement conditions were used to eliminate multiplicative, additive, and non-linear interferences. On this basis, a set of estimations is obtained to improve the quality of the analytical results. The analytical usefulness of the proposed approach was tested on the example of the determination of three compounds from the group of bisphenols (BPs) using the chromatographic technique - HPLC-DAD (high-performance liquid chromatography with diode array detection). Compared to the reference method - fluorescence spectroscopy - the obtained results were characterized by excellent accuracy (RE=3 % in most cases). The developed methodology allowed to carry out a risk assessment on BPA, BPF, and BPS present in samples of shop receipts and canned food. Store clerks have been shown to be particularly vulnerable to PBF and BPS in receipts due to skin permeation (exposure factors were equal to 308.97 µg/g for BPF and 181.89 µg/g for BPS). Consumers should also pay close attention to the BPA found in canned food samples (the average concentration was equal to 20.61 µg/mL, and the tolerable daily intake was exceeded over 165.000 times). The analytical method and the methodological approach were evaluated using the RGB model and the AGREE approach - it was shown that the method can be successfully used for other analytical purposes (the method is White) and is environmentally friendly (Significance=0.63).

Chemometric Methods for Simultaneous Determination of Candesartan Cilexetil and Hydrochlorothiazide in Binary Combinations.

Simple, accurate, precise, and cost-effective chemometric techniques for the measurement of candesartan cilexetil and hydrochlorothiazide in synthetic mixtures were improved and validated. H-point standard addition, Q-absorption ratio, and correction absorbance spectrophotometric techniques were utilized for the simultaneous determination of both medicines in real pharmaceutical formulations. A new calibration approach was implemented based on chemical H-point standards. This approach was developed to resolve significantly overlapping spectra of two analytes and provide direct correction of both proportional and constant errors caused by the matrix of the sample. The first method of simultaneous determination of candesartan cilexetil and hydrochlorothiazide was carried out using the H-point standard addition method at wavelengths 239 and 283. For the ratio of the absorption at two selected wavelengths, one of which is the isoabsorptive point and the other being the maximum of one of the two components, the second method absorption ratio method was utilized. In distilled water, the isoabsorptive point of candesartan cilexetil and hydrochlorothiazide occurs at 258 nm. λ max of hydrochlorothiazide is 273 nm, which is the second wavelength used. Lastly, the absorbance correction method was implemented. This approach is based on absorbance correction equations and uses distilled water as the solvent for the examination of both medicines. In NaOH/EtOH solvent, the absorbance maxima of candesartan cilexetil and hydrochlorothiazide are 250 nm and 340 nm, respectively. For both wavelengths, candesartan cilexetil and hydrochlorothiazide exhibited linearity over a concentration range of 1-46 μg/ml and 1-44 μg/ml, respectively, for H-point standard addition. The Q-absorption ratio approach provides linearity over the concentration ranges of 1-46 μg/ml at 273 nm for candesartan cilexetil and 1-29 μg/ml for hydrochlorothiazide, 1-46 μg/ml at 258 nm for candesartan cilexetil, and 1-44 μg/ml for hydrochlorothiazide. For hydrochlorothiazide, the linearity for the correction absorbance method was obtained throughout a concentration range of 1-46 μg/ml at wavelengths 250 and 340 nm and 1-44 μg/ml at wavelength 250 nm. The results of the analysis have been statistically and empirically supported by recovery studies. All methods yielded recoveries in the range of 96 -102% for both medications. The LOD ranged from 0.46 -0.94 μg/mL for hydrochlorothiazide and from 1.26 -2.40 μg/mL for candesartan cilexetil. The approaches were then used to quantify candesartan cilexetil and hydrochlorothiazide in pharmaceutical tablets.

Development of ternary H-point standard addition method for simultaneous analysis of curcuminoids by differential pulse voltammetry

Turmeric (Curcuma longa L.) rhizome is one of the most famous plants that has been widely used in food, medicine, and industry. Its quality deeply depends on the presence of curcuminoids and their ratios. As their structures are very similar to each other, this work reported simple, accurate, fast, and sensitive method based on developed ternary H-point standard for differential pulse voltammetry (t-HPSAM-DPV). For electrochemical determination of three analytes in the sample, three standards were added simultaneously. This method was developed for detection of three curcuminoids including curcumin (CU), desmethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) in real samples. The precision of method has RSD% < 5.5 % and the accuracy of proposed method has relative error lower than 7.0 %. Also, intra and inter-day precisions have provided the mean RSD% < 4.50. The LOD values were obtained for CU, DMC and BDMC are 0.6 × 10-6, 0.57 × 10-6 and 0.42 × 10-6, respectively. Compared with other reported HPLC methods, the results revealed a reasonable accurate precision for proposed method. Under optimized experimental conditions, t-HPSMA significantly resolved overlapping of DPV peaks of CU, DMC, and BDMC. This method can be successfully used for ternary analysis of analytes using one standard addition to the real samples.

H-point standard addition method for simultaneous determination of phenylephrine hydrochloride, chlorpheniramine maleate, and paracetamol as a ternary mixture in pharmaceutical formulations

The simultaneous analysis of a ternary mixture containing paracetamol (PAR), phenylephrine hydrochloride (PHE), and chlorpheniramine maleate (CPM) was conducted without prior separation and using an advanced spectrophotometric method. The H-point standard addition and absorbance correction methods were selected to determine the compounds, which are highly overlapped spectra in pharmaceutical formulations. The method is based on the use of three different wavelengths of 296, 272, and 227 nm for the ternary mixture. The concentration of PAR was calculated directly at 296 nm because no interferences existed. Absorbance correction method was used to remove the role of PAR at 272 and 227 nm. The concentrations of the PHE and CPM compounds in the mixture were determined by using the H-point standard addition method. The results showed that simultaneous determination of PAR, PHE, and CPM could be conducted within the range of 1–33 μg/mL, 1–23 μg/mL, and 1–36 μg/mL, respectively. The relative standard deviations for the simultaneous determination of PHE, CPM, and PAR were 0.617, 2.76, and 1.71, respectively. The proposed method was implemented successfully for the simultaneous determination of PAR, PHE, and CPM in pharmaceutical formulations.

Q-ABSORBANCE RATIO, DERIVATIVE SPECTROPHOTOMETRIC AND H-POINT STANDARD ADDITION METHODS FOR SIMULTANEOUS DETERMINATION OF PRIDINOL MESYLATE, AND DICLOFENAC SODIUM IN PHARMACEUTICAL FORMULATION.

&nbsp;&nbsp;&nbsp;&nbsp; Three methods for simultaneous estimation of diclofenac sodium and pridinol mesylate have been developed. First method is the application of the Q–analysis (absorbance ratio) method, the wavelengths selected were 265nm (isosbestic point) and 285nm (λmax of diclofenac sodium) with 258nm (λmax of pridinol mesylate). The linearity ranges for diclofenac sodium and pridinol mesylate were 8-64 μg/ml and 14-56 μg/ml, respectively. The second technique is based on the second derivative spectrophotometric method at zero crossing wavelengths. The linearity ranges for diclofenac sodium and pridinol mesylate were (4.0-40.0) μg/ml and (4.0-30.0) μg/ml, respectively. The third method is the H-Point Standard addition method (HPSAM) depending upon the zero and second-order derivative signals for diclofenac sodium and pridinol mesylate were applied pairs of wavelengths, 250.37and 266.34 nm; with 224.18 and 235.10 nm, respectively.

H-point Standard Addition Method for the Simultaneous Spectrophotometric Determination of Captopril and Hydrochlorothiazide in Pharmaceutical Formulations

Simultaneous spectrophotometric determination of captopril and hydro-chlorothiazide in pharmaceutical formulations by the H-point standard addition method (HPSAM) is described. Absorbance at 211.5 and 230.3 nm was monitored upon the addition of standard solutions of captopril. The results showed that in prepared mixtures, captopril and hydrochlorothiazide can be determined simultaneously at concentration ratios varying from 1.0:0.8 to 2.5:1.5 μg/mL, respectively. Percentage recovery was found to be 95.33–104.37% for captopril and 96.8–105% for hydrochlorothiazide, with a relative standard deviation (RSD) of 2.46%. The method was successfully used to evaluate the antihypertensive captopril drug in a binary combination of hydrochlorothiazide in real samples with high precision and accuracy within the recovery percentage.

In Vitro Culture of Rosmarinus officinalis L. in a Temporary Immersion System: Influence of Two Phytohormones on Plant Growth and Carnosol Production.

Emerging infectious diseases have become a major global problem with public health and economic consequences. It is an urgent need to develop new anti-infective therapies. The natural diterpene carnosol exhibit a wide variety of interesting antibacterial and antiviral properties, and it is considered a theoretical inhibitor of COVID-19 Mpro. However, this compound is present in the family Lamiaceae in low quantities. To obtain carnosol in concentrations high enough to develop pharmacological studies, we evaluated the efficiency of a micropropagation protocol of Rosmarinus officinalis using a solid medium and a temporary immersion system (TIS), as well as the effect of 6-benzylaminopurine (6-BAP) and α-naphthaleneacetic acid (NAA) on the growth of shoots. Moreover, we developed and validated an analytical method to quantify carnosol using the H-point standard additions method in the high-performance liquid chromatography diode array detector (HPLC-DAD). After 30 days of culture, TIS produced the maximum number of shoots per explant (24.33 ± 1.15) on a liquid medium supplemented with 6-BAP at 5.0 mg L−1. Next, we also evaluated the effect of immersion time and frequency for TIS. After 72 days of culture, the best results were obtained with an immersion cycle of 1 min every 12 h, yielding 170.33 ± 29.40 shoots. The quantification of carnosol on the samples was performed at a flow rate of 1.2 mL min−1 using binary isocratic mobile phase system 60:40 (v/v) 10 mM formic acid (pH 3.0) (A) and acetonitrile (B) on a reverse-phase column. The content of carnosol in the in vitro cultures was around 8-fold higher than in the wild plant. The present study represents an efficient alternative method to obtain carnosol for its pre-clinical and clinical development.

Comparison of Capabilities of Four Spectrophotometric Techniques for Determining Concentrations of Compounds with Highly Severe Overlapping Spectra

In this work, four time-saving, economic, and non-sophisticated spectrophotometric methods are used to determine resorcinol (RES) and catechol (CAT) in their binary solutions. The suggested methods, which require no separation steps, are namely the constant center (CC), ratio difference (RD), H-point standard addition method (HPSAM), and ratio H-point standard addition method (RHPSAM). For each method, the parameters affecting the resolution of the spectra are optimized and used for the quantification of RES and CAT in a blind binary mixture. The results obtained show that out of these four original mathematical techniques, the CC and RD methods have the least errors in the simultaneous determination of RES and CAT in their binary solution with a highly severe overlapping spectra. The calibration curves have a linear behavior over the concentration range of 2.5-20 μg/mL for both substances in both methods. The detection limits for RES are 0.89 μg/mL and 0.355 μg/mL for the CC and RD methods, respectively, and for CAT, they are 0.582 μg/mL and 0.292 μg/mL, respectively. The accuracy and precision of the methods are also investigated. The relative standard deviations have been found to be lower than 6.7 %.

A comparative study of novel spectrophotometric methods for simultaneous determination of nitroaniline isomers in their binary mixtures with highly severe overlapping spectra

In the present work, four simple and economic spectrophotometric methods, namely constant center (CC), ratio difference (RD), H-point standard addition method (HPSAM), and ratio H-point standard addition method (RHPSAM) were employed for the simultaneous determination of meta and para-nitroaniline with severely overlapping spectra without unitizing the preliminary physical separation techniques. In each method, the parameters affecting the resolution of the spectra were optimized to determine the cited isomers in a binary mixture with a high accuracy. Under the optimized conditions, the results obtained showed that from cited methods used, the CC and RD methods have the least errors in determination of the concentration of highly spectral overlapping species. The mean percentage recovery values for the binary mixture of meta- and para-nitroaniline were found to be 95.98 and 98.78 using the RD method, and 101.85 and 100.23 using the CC method, respectively. For comparison of the powerful multivariate methods including the principal component regression (PCR) and partial least squares (PLS) were also applied. The mean percentage recovery values for the binary mixtures of the cited isomers were found to be 101.62 and 101.47 using the PCR method, and 101.00 and 101.36 using the PLS method, respectively. A statistical comparison of the methods demonstrated that there was no significant difference between the RD, CC, PCR, and PLS methods and the reported HPLC method regarding both accuracy and precision. The proposed methods have an admissible precision and accuracy for determination of the two isomers in their binary mixtures in tap water as a real sample.

Separation-free spectrophotometric platforms for rapid assessment of combined antiplatelet therapy in complex matrices.

Aim: To develop simple and rapid UV-spectrophotometric platforms for the simultaneous quantification of a binary mixture containing clopidogrel bisulphate (CPS) and aspirin (ASP) in complex matrices without prior separation. Experimental: Five mathematical models namely ratio-difference method, mean centering of the ratio spectra, dual wavelength, induced dual wavelength and H-Point Standard Addition method, were utilized for resolving spectral overlap by mathematical processing of ratio and zero-order absorption spectra. Analytes were extracted from tested matrices (whole blood, pharmaceutical formulations and dissolution media buffer) and quantified using the proposed methods. The methods were validated according to ICH guidelines. Results: The developed methods demonstrated limits of detection ranging from 0.67 to 1.09μg/ml-1 for CPS and 0.49 to 0.71μg.ml-1 for ASP. All proposed methods allowed for reliable determination of CPS and ASP in complex matrices within reported reference ranges, indicating their potential application for therapeutic drug monitoring and quality control testing.

Simultaneous determination of Nebivolol hydrochloride and Valsartan in their binary mixture using different validated spectrophotometric methods.

Five simple, sensitive, accurate and precise spectrophotometric methods were developed for the simultaneous determination of Nebivolol hydrochloride (NEB) and Valsartan (VAL) in their binary mixtures and in pharmaceutical dosage form. The methods included Ratio Difference, First Derivative ratio, Mean Centering of ratio spectra, Bivariate and H-Point Standard additions method. The calibration curves were linear over the concentration range of 10-70μg/ml and 20-60μg/ml for NEB and VAL, respectively for Ratio Difference and First Derivative ratio method and over the concentration range of 10-70μg/ml and 10-60μg/ml for NEB and VAL, respectively for Mean Centering of ratio spectra, Bivariate and H-Point Standard additions method. These methods were examined by analyzing synthetic mixtures of the studied drugs and they were utilized to determine the studied drugs in their commercial pharmaceutical preparation. All methods were validated as per ICH guidelines and accuracy, robustness, repeatability and precision were found to be within the acceptable limits. The results of the proposed methods were compared to the results of reported methods with no significant difference between them.

Advanced approaches for the treatment and amplification of weak spectral signals produced by critical concentrations in white multicomponent systems.

An analytical investigation was carried out to study the treatment and amplification of the spectral signals produced by critical concentrations with high accuracy and precision using two advanced approaches. The factorized-spectrum approach was applied through two novel methods which were: absorptivity centering technique via both: factorized zero order absorption spectrum (ACT-FSD0ΔA) and factorized ratio spectrum (ACT-FSRΔP). The proposed methods were found to be linear in the ranges of (15-100 μg/mL) and (3-40 μg/mL) for ASP and MTO, respectively. Those methods were compared to the methods following the geometrical standard addition approach: ratio H-point standard addition method (RHPSAM) and geometrical induced amplitude modulation (GIAM). The approaches were applied for the determination of the minor component metoclopramide in its mixture with the major component aspirin in the challengeable ratio of (1,90) respectively in a white multicomponent system. The results obtained from the proposed approaches were statistically compared with each other. The methods were validated according to ICH guidelines where the results were found to be within the acceptable limits. The methods were found to be accurate and reliable for the determination of metoclopramide critical concentration besides aspirin concentration. The results of single factor ANOVA analysis indicated that there is no significant difference among the developed methods. These methods provided simple resolution of this binary combination from synthetic mixtures and pharmaceutical preparation and can be conveniently adopted for routine quality control analysis.

Combination of sequential injection analysis with an integrated [BF4]-potentiometric sensor for the kinetic determination of boron

This work deals with the development of a kinetic technique for boron determination based on the monitoring of a tetrafluoroborate-formation reaction carried out in a potentiometric cell integrated with a sequential injection system. A previously elaborated PVC-membrane electrode based on the active substance formed by the ion pair of 2-[3-(5,6-dimethyl-3-nonyl-1,3-benzothiazol-2(3H)-ylidene)propenyl]-5,6-dimethyl-3-nonyl-1,3-benzothiazolium (DMNBT) with tetrafluoroborate ion was used. The metrological characteristics of the proposed sensor were tested in the presence and absence of F- in a concentration range of phosphoric acid from 0.1 to 7.0 M. The sensor is sensitive to tetrafluoroborate, with a slope of −56.5 ± 1.0 mV/pC and a LOD near pCmin = 6.7, and can be applied for the monitoring of the tetrafluoroborate-formation reaction in acidified fluoride solutions containing up to 7.0 M H3PO4 . The optimal reaction media that ensured sufficient difference in the response time of the sensor and the rate of [BF4]- appearance in the reaction media was 4.0 M H3PO4 and 0.2 M NH4F. The H-point standard addition method (HPSAM) was applied for the evaluation of selectivity. Its application was based on the fact that the response time of the sensor to the appearance of tetrafluoroborate and interferents in the reaction media was totally different. The proposed method was successfully applied for the determination of boron in unmineralised honey samples. Reliability of the results was tested using the ICP-MS method.

Simultaneous Kinetic Spectrophotometric Determination Of Ascorbic Acid And Cysteine With An Optical Probe By Mean Centering Of Ratio Kinetic Profiles Method

A procedure for simultaneous kinetic analysis of a binary mixture of ascorbic acid (Asc) and cysteine (Cys) was developed using the method of mean centering of ratio kinetic profiles. The method is based on the difference in the rate of reactions of Asc and Cys with the complex of iron(III) with o-phenanthroline at pH 7.05. The use of an optical probe simplifies the carrying out of kinetic measurements, allows to obtain highly reproducible (Sr=0.01-0.02) results, and significantly reduces the time of analysis. The method of mean centering of ratio kinetic profiles is superior to the H-Point standard addition method, since it does not require such a long measurement time and there is no restriction on the constancy of absorbance of one of the components. Asc and Cys can be determined in the concentration range from 1 to 10 mg/L. The method was successfully used to determine Asc and Cys in dietary supplements.

Simultaneous determination of antinonin and trifluralin by electrochemical method and net analyte signal interferent modeling

Antinonin and trifluralin are selective herbicides to control the insects and usually used with each other. Simultaneous determination of antinonin and trifluralin has been investigated, using modified carbon paste electrode (CPE) prepared from: graphite, multi-walled carbon nanotubes (MWCNT) and nanomagnetic core-shell (Fe3O4/SiO2). Cyclic voltammetry (CV) and square wave voltammetry (SWV) studies indicated two-oxidation peak for antinonin and one oxidation peak for trifluralin from 0 to +0.6 V. For simultaneous determination of antinonin and trifluralin severe overlap of the voltammogram profiles was observed. It was shown that the electrochemical profile of the analytes changes in the presence of each other. Therefore, results of the analysis of antinonin and trifluralin by H-point standard addition method in their mixtures in water samples were not satisfactory. In order to determine antinonin and trifluralin simultaneously, net analyte signal interferent modeling (NAS-IM) was used. The proposed sensor was found that is able to determine antinonin and trifluralin with a detection limit of 0.3 and 3 nM, respectively. The method was successfully applied for the assay of antinonin and trifluralin simultaneously in water samples.

H-point standard addition for simultaneous reagent-free spectrophotometric determination of B1 and B6 vitamins.

Vitamin deficiency is a main cause of many disorders and diseases that cannot be treated without using dietary supplements and multivitamin medications. We present here a UV-spectrophotometric method for simultaneous assay of two of the widely used vitamins, thiamine hydrochloride (vitamin B1) and pyridoxine hydrochloride (vitamin B6). The method is based on H-point standard addition to estimate the vitamins under study in their pure solutions and multivitamin ampoules by measuring the absorption of the mixture at 283 and 298 nm allowing its application in quality control laboratories. The work summarizes the theoretical basis of the H-point standard addition method. Moreover, a guide for the selection of the two wavelengths at which the calibration curves are constructed is given in this investigation. The linear ranges of the calibration graphs are 6.75-67.5 and 2.06-20.56 μg/mL for thiamine and pyridoxine, respectively. Correlation coefficients (r2) were found to be 0.9990 and 0.9899 at 283 nm and 0.9855 and 0.9995 at 298 nm for vitamin B1 and vitamin B6, respectively. Oscillator strength (f), transition dipole moment (μ) and resonance energy (RN) were calculated. The method was successfully applied for dual determination of the vitamins in their pure solutions and multivitamin ampoules with recovery values ranging from 98.41 to 102.6 and from 95.39 to 104.9% for thiamine and pyridoxine, respectively. The accuracy and precision of the proposed method is obvious from the low relative standard deviation values which are not more than 1.19%.