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Adsorptive stripping voltammetric study of vitamin B1 at multi-walled carbon nanotube paste electrode
⁎Corresponding author. Tel.: +91 07582265265, 09479354823; fax: +91 7582223236. tiwari25_pradeep@yahoo.com (Pradeep Kumar Brahman)
-
Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Peer review under responsibility of King Saud University.
Abstract
The electrochemical response of vitamin B1 at different types of carbon electrodes viz: glassy carbon electrode (GCE), carbon paste electrode (CPE), single walled carbon nanotube paste electrode (SWCNTPE) and multi walled carbon nanotube paste electrode (MWCNTPE) has been investigated using cyclic voltammetric (CV) and differential pulse adsorptive stripping voltammetric (DPAdSV) methods. A simple and selective differential pulse adsorptive stripping voltammetric method has been developed for the determination of vitamin B1 in pure form and in pharmaceutical preparations. Various parameters that can influence the peak signal (effect of buffer, accumulation time, pH, scan rate, accumulation potential, and pulse amplitude) have been scrutinized. The best results were obtained in acetate buffer (pH 6.3) using multi-walled carbon nanotube paste electrode at a deposition time of 80 s, deposition potential of 0.0 V, scan rate of 50 mV s−1 and pulse amplitude of 50 mV.
The reduction peak current varies linearly with the concentration of vitamin B1 over the range of 1.0 × 10−7–1.0 × 10−6 M. The limits of detection and quantification of the pure drug are 1.1 × 10−10 M and 2.0 × 10−9 M, with the correlation coefficient, r = 0.997 and the relative standard deviation, RSD = 1.2% (n = 5). Experimental results reveal that the MWCNTPE has advantages of small background current, high signal to background current ratio and good reproducibility.
Keywords
CPE
Vitamin B1
DPV
Pharmaceutical preparations
1 Introduction
Vitamins are an essential group of food ingredients which have to be supplied in sufficient amounts with diet. Vitamins are a broad group of organic compounds that are minor, but essential constituents of food required for normal growth, self maintenance and functioning of human and animal bodies (Poongothai et al., 2010). Vitamin B1 (thiamine) contains pyrimidine and a thiazole ring (Scheme 1). It performs important biochemical functions as a coenzyme thiamin pyrophosphate (TPP) which is involved in energy metabolism. Thiamine is also present in tissues, as thiamin monophosphate and thiamin triphosphate. Thiamine is readily soluble in water and alcohols. It is stable in acid but is unstable to heat, oxidation and an alkaline pH. Vitamin B1 is one of the eight vitamins that make up the powerful group called vitamin B complex. It plays a major role in the good health of the body as well as in sound mental health (Akyilmaz et al., 2006; Zhang et al., 2010; Markopoulou et al., 2002).
Structure of vitamin B1.
Electroanalytical methods (Habibia et al., 2010; Gu et al., 2001; Wu and Song, 2008; Desai et al., 2008; Jaiswal et al., 2001; Liu et al., 2002) are widely used in scientific studies and in monitoring of industrial materials, pharmaceutical compounds, biological samples, and the environment. The most widespread electroanalytical methods are voltammetry and polarography. The performance of the voltammetric techniques is strongly affected by the aspects of the working electrode material such as chemical and physical properties of electrode surfaces, applied potential, adsorption and coatings applied to the electrode surface to enhance detection. Solid electrodes are practical electrode materials and are widely used in electroanalytical research for electroanalysis purposes. Their increasing popularity can be attributed to the fact that the oxidation of many organic molecules cannot be studied by the mercury electrode because of its limited anodic potential range. Carbon-based electrodes can play an important role on the analytical performance. The best known carbon-based electrodes are those involving glassy carbon, carbon paste, carbon fiber, screen printed carbon strips, carbon films, diamond, pyrolytic graphite, and carbon nanotube. (Uslu and Ozkan, 2007; Jemelkova et al., 2010; Yosypchuk and Barek, 2009).
Several methods have been used for the determination of thiamine, e.g. liquid chromatography with electrochemical detection (Hart et al., 1984, 1985; Bohrer et al., 2004; Markopoulou et al., 2002), spectrophotometric determination (Liu et al., 2002) and there are also several methods for determining thiamine by polarography/voltammetry (Hart et al., 1995; Oni et al., 2002; Aboul-Kasim, 2000; Siddiqui and Pitre, 2001). A survey of the literature reveals that there is no differential pulse adsorptive stripping voltammetric method for the determination of vitamin B1 at MCNTPE with a lower detection limit.
The aim of the present work is to compare carbon electrodes and develop and validate an electroanalytical method for the determination of vitamin B1. The method was successfully applied to the determination of vitamin B1 in pharmaceutical preparations.
2 Experimental
2.1 Chemicals and reagents
All reagents were of AR grade purchased commercially. Vitamin B1 of Himedia Ltd. Mumbai was used. Solutions were prepared using double distilled water. Stock standard solution of vitamin B1 (0.001 M) was prepared in double distilled water. Vitamin B1 and its pharmaceutical dosage forms Neurobion fort 10 mg, Neurokeme 100 mg, Vitneurin 100 mg and Becadexamin 10 mg were purchased from the local market. Standard solutions were prepared by appropriate dilution of the stock solutions over the range of desired concentrations with acetate buffer.
2.2 Apparatus
All voltammetric experiments were performed with Ω Metrohm model 797 VA Computrace (ion analyzer, Switzerland.) through electrochemical software version 3.1. A three-electrode cell was employed incorporating a working carbon electrode, an Ag/AgCl (saturated KCl) reference electrode and a platinum wire counter electrode. Mass transport was achieved with a Teflon-coated bar at approximately 400 rpm using a magnetic stirrer. A Systronics digital μpH meter model-361 was used for pH measurements. All experiments were performed at room temperature and dissolved oxygen was removed by passing pure nitrogen through the solutions.
2.3 Analytical procedure
Techniques used for the voltammetric determination of vitamin B1 were differential pulse adsorptive stripping voltammetry (DPAdSV) and cyclic voltammetry (CV). The measurements were performed in an acetate buffer (pH 6.3) at a scan rate of 50 mV s−1, current range of 10 μA and pulse amplitude of 50 mV at laboratory temperature. The 0.001 M stock solution was prepared by diluting vitamin B1 in deionized water. Fresh solution of appropriate concentration was prepared for each measurement by diluting the stock solution with an acetate buffer of appropriate pH. The calibration curves were measured in triplicate and their statistical parameters (e.g., slope, intercept, correlation coefficient, and limit of detection) were calculated. The detection limits were calculated as the concentration of an analyte using 3s/m where s is the standard deviation of intercept and m is slope.
2.4 Preparation of pharmaceuticals
The drug content of ten tablets was weighed, finely powdered and mixed. The average mass per tablet was determined. A sample equivalent to one tablet was weighed and transferred into a 100 ml calibrated flask and completed to the volume with double distilled water. The contents of the flask were kept standing for 20 min to achieve complete dissolution. The non-dissolved excipients were allowed to settle down. The sample from the clear supernatant liquor was withdrawn and quantitatively diluted with acetate buffer. This solution was then transferred to a voltammetric cell and the analysis was done at pH 6.3.
2.5 Preparation of carbon paste electrode
Carbon paste was prepared in the usual way by hand-mixing graphite powder (Sigma Aldrich) and mineral oil (Sigma Aldrich). The ratio of graphite powder to mineral oil was 70:30. The prepared paste was filled into the Teflon well. A copper wire fixed to a graphite rod and inserted into the Teflon well serves to establish electrical contact with the external circuit. A good reproducibility of electrode response was achieved by simply renewing the surface of carbon paste electrode. A new electrode surface was formed by mechanically pressing the carbon paste from the top of the Teflon well smoothening of the electrode surface was done by rolling a smooth glass rod on the electrode surface and finally it was cleaned carefully by distilled water.
2.6 Preparation of carbon nanotube paste electrode
The CNTPE was prepared by mixing CNT, graphite powder and high viscosity paraffin (density = 0.88 g cm−3) from Sigma Aldrich in a ratio of 10:60:30% (w/w) in a mortar. A portion of the resulting paste was then inserted into the bottom of a Teflon well. The electrical connection was implemented by a copper wire fitted into the Teflon well. The surface of the resulting paste electrode was smoothened on a weighing paper and rinsed carefully with distilled water. The polished electrode was pretreated at optimized potential of +1.80 V vs. Ag/AgCl for 5 min for the electrochemical activation of electrode surface. Pretreatment was carried out in 0.2 M acetate buffer solution (pH 4.80) containing 20 mM of NaCl without stirring.
2.7 Recovery experiments
Recovery of vitamin B1 from the matrix effects was used as a measure of the accuracy or the bias of the method. Concentrations in the same range as utilized in the linearity studies are used. To investigate the accuracy and reproducibility of the proposed methods, recovery experiments were carried out using the standard addition method. In order to know whether the excipients show any interference with the analysis, a known amount of pure vitamin B1 was added to the pharmaceutical solutions and these solutions were analyzed by the proposed method. The recovery results were determined based on four parallel analyses.
3 Results and discussion
3.1 Electrochemical behavior of vitamin B1
To illustrate the electro catalytic effect of the carbon electrodes toward vitamin B1, the electrochemical behavior of vitamin B1 at four different kinds of working electrodes were examined using differential pulse voltammetry (Fig. 1). At glassy carbon electrode, 5.0 × 10−7 M vitamin B1 yields a very low reduction peak at −1.36 V in 0.2 M acetate buffer at pH 6.30 ± 0.01 (curve 1). Under identical conditions, the reduction peak height of vitamin B1 at CPE increases slightly compared with that at GCE (curve 2). The reduction peak of vitamin B1 at SWCNTPE was observed to be higher than that at CPE and is obtained at 1.4 V (curve 3). However, the reduction peak current of vitamin B1 at MWCNTPE increases significantly, in comparison with that at all the electrodes at 1.42 V (curve 4). A remarkable peak current enhancement and the fall of reduction over potential undoubtedly testify the usefulness of MWCNTPE for the electroanalysis of vitamin B1. The highest signal of vitamin B1 was obtained at MWCNTPE in acetate buffer pH 6.3. The concentration dependence was measured in the range 1.0 × 10−7–1.0 × 10−6 M at all carbon electrodes (Fig. 2). Parameters of the calibration straight lines obtained using linear regression method is summarized in Table 1. It can be seen from the comparison of slopes for the determination of vitamin B1 on GCE, CPE, SWCNTPE and MWCNTPE that higher sensitivity is obtained using MWCNTPE. The remarkable peak current enhancement can undoubtedly be attributed to the unique structure and properties of MWCNT (such as very large specific area, strong adsorptive ability, and subtle electronic properties).
Differential pulse adsorptive stripping voltammograms of 5.0 × 10−7 M vitamin B1 at (1) GCE, (2) CPE, (3) SWCNTPE and (4) MWCNTPE in 6.3 ± 0.01 pH acetate buffer, scan rate 50 mV s−1, Current range 10 μA and pulse amplitude 50 mV.
Calibration plot of vitamin B1 (concentration range 1.0 × 10−7–1.0 × 10−6 M) at (1) GCE, (2) CPE, (3) SWCNTPE and (4) MWCNTPE.
Electrodes
Concentration range (M)
Slope
Intercept
Correlation coefficient
Detection limit (M)
GCE
1.0 × 10−7–1.0 × 10−6
−0.240
−0.353
0.973
8.4 × 10−9
CPE
1.0 × 10−7–1.0 × 10−6
−0.277
−0.525
0.987
3.1 × 10−9
SWCNTPE
1.0 × 10−7–1.0 × 10−6
−0.371
−0.570
0.995
9.1 × 10−10
MWCNTPE
1.0 × 10−7–1.0 × 10−6
−0.489
−0.631
0.997
1.1 × 10−10
The repetitive cyclic voltammograms of 5.0 × 10−7 M vitamin B1 at MWCNTPE in acetate buffer of pH 6.3 are illustrated in Fig. 3. A well defined and sensitive reduction peak appears at −1.4 V. On the reverse potential scan from −1.6 to −0.6 V, there is no corresponding oxidation peak observed for vitamin B1 which shows that the electrode process is irreversible. Moreover, the reduction peak current of vitamin B1 decreases remarkably during the successive cyclic potential sweeps. After the second cyclic voltammetric sweep, the peak current decreases slightly and finally almost becomes constant. This phenomenon may be caused due to the fact that the adsorption of vitamin B1 or its oxidative product occurs at the electrode.
Repetitive cyclic voltammograms of 5.0 × 10−7 M vitamin B1 at MWCNTPE at pH 6.3 ± 0.01 in acetate buffer scan rate 50 mV s−1. Current range 10 μA.
3.2 Optimization conditions for the determination of vitamin B1
3.2.1 Supporting electrolyte selection
The supporting electrolyte plays an important role in the electrochemical response. The thermodynamics and kinetics of electrochemical processes, as well as mass transfer within the cell, are dependent on its nature, concentration and pH. Ten supporting electrolytes were tested for vitamin B1 determination: pH 3.5–8.0 phosphate buffer, pH 6.0–8.0 KCl, pH 2.0–10 Borate buffer, pH 3.0–7.0 acetate buffer, pH 8.0–12 NH3/NH4Cl, pH 2.0–9.0 Brittin–Robinson, pH 6.0–9.0 TMAH, pH 6.0–10.0 TMAB, and pH 5.0–8.0 Tris buffer. The influence of pH on electrochemical behavior of vitamin B1 at a MWCNTPE was monitored using differential pulse voltammetry. Vitamin B1 gives one reduction peak in the range of pH 2–10 in all the buffer systems used except acetate buffer of pH 5.0. However, vitamin B1 gives two reduction peaks in acetate buffer at pH 5.0. The highest signal of vitamin B1 was obtained in acetate buffer of pH 6.3. This was used for the calibration measurement at MWCNTPE.
3.2.2 Influence of the potential scan rate
The effect of the potential scan rate on the vitamin B1 reduction was studied over 50–250 mV s−1 for 5.0 × 10−7 M vitamin B1 in 0.2 M acetate buffer (pH 6.3) at all carbon electrodes. Dependence of the cyclic voltammetric peak currents upon the scan rate is displayed in Fig. 4. A linear relation between peak currents and scan rate which indicates that electrode process is adsorption controlled (Turan et al., 2009; Shamsipu and Farhadi, 2000; Al-ghamdi et al., 2004; Ramadan and Mandil, 2010; Jain et al., 2009; Sanghavi and Srivastava, 2010; Dar et al., 2011, 2012) (Fig. 5). The same behavior was found for all types of electrodes. One well-resolved irreversible reduction peak was observed at −1.46 V at MWCNTPE for a scan rate of 50 mV s−1 which was used as the analytical signal for vitamin B1 quantitation. The peak potential shifts to more negative values as the scan rate increases (r = 0.947), which shows the irreversible electrochemical behavior for vitamin B1 reduction at electrode surface (Fig. 6).
The CVs of 5.0 × 10−7 M vitamin B1 in the acetate buffer of pH 6.3 ± 0.01 at MWCNTPE, current range 10 μA. Scan rates (1) 50 mV s−1, (2) 70 mV s−1, (3) 90 mV s−1,(4) 110 mV s−1, (5) 130 mV s−1, (6) 150 mV s−1, 170 mV s−1 (7) 190 mV s−1(8) 210 mV s−1 (9) 230 mV s−1 and (10) 250 mV s−1.
The relationship between peak current and scan rate mV s−1.
The relationship between peak potential and scan rate mV s−1.
3.2.3 Effect of accumulation time and accumulation potential
Fig. 7 shows the dependence of the adsorptive peak current on the preconcentration time for 5.0 × 10−7 M vitamin B1 at MWCNTPE. At first, ipa increased linearly with t, indicating that before adsorptive equilibrium is reached, the longer the accumulation time, more the vitamin B1 adsorbed and the larger was the peak current. However, after a specific period of accumulation time, the peak current tended to level off, illustrating that adsorptive equilibrium of vitamin B1 on the electrode surface was achieved. The peak current increased with the increase in preconcentration time up to 80 s. Therefore, 80 s accumulation time was chosen for voltammetric study.
Differential pulse voltammograms of 5.0 × 10−7 M vitamin B1 at (1) 0.0 s, (2) 40 s, (3) 80 s, (4) 120 s and (5) 140 s accumulation time.
In addition, when the influence of preconcentration potential on the observed voltammetric signal was examined over the range of −0.6 to +0.2 V, the peak current increased steadily over the positive direction till it reached its maximum value at Ep = 0.0 V where it decreased sharply thereafter. Hence, for optimal analytical sensitivity this experimental parameter was maintained at 0.0 V.
3.2.4 Effect of pH
The pH of the supporting electrolyte exerted a significant influence on the electro-reduction of vitamin B1 at MWCNTPE. The influence of pH on the reduction of vitamin B1 was studied by differential pulse voltammetry at pH 4.5–7.0 of acetate buffer.(Fig. 8). It was found that peak potential shifts to a more negative value of the applied potential when pH changes from 4.5 to 7.0. At pH 4.5 a single broad and at pH 5.0–6.0 two peaks were obtained. However, a well defined single peak was obtained at pH 6.3 and 7.0 and peak current is more at pH 6.3 which was used in all experiments.
Differential pulse voltammograms of 5.0 × 10−7 M vitamin B1 at pH (1) 7.0, (2) 6.3, (3) 6.0, (4) 5.5, (5) 5.0 and (6) 4.5 of acetate buffer.
3.3 Differential pulse adsorptive stripping voltammetric determination of vitamin B1
Since differential pulse adsorptive stripping voltammetry (DPAdSV) has a higher current sensitivity and low background current via charging current than cyclic voltammetry, it was used in the determination of vitamin B1 at the MWCNTPE and estimating a lower limit of detection. The cathodic peak was used for the determination of vitamin B1 by DPAdSV within the potential range scanned (−0.6 to −1.6 V). The effect of pulse amplitude, at 25, 50 and 100 mV was also studied. As expected, an increase in peak current was observed at 100 mV; however, the better signal response was obtained at a pulse amplitude of 50 mV. The reduction peak current was measured in acetate buffer at pH 6.3 (Fig. 9), and plotted against the concentration of vitamin B1 (Fig. 10). The dependence of peak current on the concentration of vitamin B1 is a linear relationship in the range of 1.0 × 10−7–1.0 × 10−6 M (coefficient of variation = 0.997). The detection limit (3s/m) is 6.1 × 10−10 M. The relative standard deviation of five successive scans is 1.2% for 5.0 × 10−7 M vitamin B1 indicating that the MWCNTPE had an excellent reproducibility. The regression data are shown in Table 2. The long-term stability of the MWCNTPE was evaluated by measuring the current responses at a fixed vitamin B1 concentration of 5.0 × 10−7 M over a period of a week. The MWCNTPE was used daily and stored in the air. The experimental results indicated that the current responses deviated only 1.2%, revealing that the MWCNTPE possesses moderate stability.
Differential pulse adsorptive stripping voltammogram of different concentrations of vitamin B1 in acetate buffer (pH 6.3 ± 0.01) at bare MWCNTPE, pulse amplitude 50 mV. (1) 1.0 × 10−7 M, (2) 2.0 × 10−7 M, (3) 3.0 × 10−7 M, (4) 4.0 × 10−7 M, (5) 5.0 × 10−7 M, (6) 6.0 × 10−7 M, (7) 7.0 × 10−7 M, (8) 8.0 × 10−7 M, (9) 9.0 × 10−7 M and (10) 1.0 × 10−6 M).
Calibration plot of different concentration of vitamin B1.
Parameters
Differential pulse adsorptive stripping voltammetry
Measured peak potential (V)
−1.4 V
Linearity range (M)
1.0 × 10−7–1.0 × 10−6
Slope (μA/M)
−0.489
Intercept (μA)
−0.631
Correlation coefficient (r2)
0.997
Limit of detection (LOD) (M)
1.1 × 10−10
Limit of quantification (LOQ) (M)
2.0 × 10−9
Repeatability of peak current (RSD%)
1.2
Repeatability of peak potential (RSD%)
1.0
Reproducibility of peak current (RSD%)
1.0
Reproducibility of peak potential (RSD%)
1.3
3.4 Analysis of vitamin B1 in pharmaceutical samples
Due to the high sensitivity of MWCNTPE, it was applied for the voltammetric determination of vitamin B1 in the commercial pharmaceutical samples with different compositions using calibration plot. The results obtained by the MWCNTPE are in good agreement with the declared vitamin B1 content (Table 3). Further, in order to establish the suitability of the proposed method, known amounts of the standard vitamin B1 were added into the analytical solution of the vitamin B1 tablets and the same procedure was applied. The recoveries indicate that the accuracy and repeatability of the proposed voltammetric method are very good. From the above experimental results, it is obvious that this novel MWCNTPE has great potential for a practical sample analysis.
Sample no.
Differential pulse adsorptive stripping voltammetry
Amount found/mg
Brand A
Brand B
Brand C
Brand D
1
10.4
98.23
98.4
10.2
2
9.83
99.5
99.8
9.8
3
9.91
98.01
100.4
9.93
4
10.3
100.3
99.9
10.01
Labeled amount
10
100
100
10
X
10.11
99.01
99.62
9.98
S
0.35
0.31
0.22
0.07
RSD%
3.5
0.31
0.22
0.7
95% confidence limit
9.36–10.86
98.34–99.67
99.14–100.1
9.83–10.13
Mean recoveries %
101.1
99.01
99.65
99.85
3.5 Validation of the proposed method
Once the most ideal and suitable chemical conditions and instrumental parameters for the differential pulse voltammetric determination were established, a calibration plot for the analyzed drug was recorded to estimate the analytical characteristics of the developed method.
3.5.1 Linearity
In order to determine the effect of concentration of vitamin B1 on DPV peak current, voltammograms of vitamin B1 were recorded at MWCNTPE. Under the optimum conditions a very good linear correlation was obtained between the monitored voltammetric peak current and vitamin B1 concentration in the range 1.0 × 10−7–1.0 × 10−6 M (Fig. 10). Least-square treatment of the calibration graph yielded the following regression equation. where ip is the peak current, x is the analyzed drug concentration and r is the correlation coefficient.
3.5.2 Detection and quantification limit
Detection limit was calculated by equation LOD = 3s/m, where s is the standard deviation of intercept and m is the slope of the regression line. The calculated LOD value of vitamin B1 is 1.1 × 10−10 M. The quantification limit (LOQ) is examined by the equation LOQ = 10s/m. The calculated LOQ value is 2.0 × 10−9 M. Both LOD and LOQ values confirmed the sensitivity of the proposed methods.
3.5.3 Accuracy, reproducibility and stability
The accuracy of the proposed method was checked by calculating the recovery of the known amount of vitamin B1 (5.0 × 10−7 M) added to acetate buffer solution and analyzed via the optimized voltammetric procedure. The value of the recovery obtained by the standard addition method was 99.01–101.1%.
The high sensitivity of differential pulse voltammetry is accompanied by very good reproducibility. This analytical performance was evaluated from eight repeated measurements of electrochemical signal of 5.0 × 10−7 M vitamin B1. The precision of the electrochemical developed method in terms of the relative standard deviation was 1%.
Under optimum conditions, the stability of 5.0 × 10−7 M vitamin B1 solution was evaluated by monitoring the changes in the height of DPV peak over a period of 80 min. The electroanalytical signal was gradually constant with time. The acidic media (pH 6.3) of the acetate buffer electrolyte solution probably initiated a slow degradation process for the drug.
3.5.4 Interference studies
In order to evaluate the selectivity of the developed DPV procedure, the influence of various interferences was examined. Considerable interference can be caused by co-existing surface-active compounds capable of competing with the analyte of interest for the adsorption site on the electrode surface, resulting in a decreased peak height (Dar et al., 2011). The competitive co-adsorption interference was evaluated in the presence of various substances usually occurring in pharmaceutical tablets and formulations. For these investigations, the interfering species were added at different concentrations (5-, 25- and 50-fold) higher than the concentration of vitamin B1 (5.0 × 10−7 M). The additions of filling materials (sucrose, lactose and cellulose), disintegrate agent (starch) and lubricants such as magnesium stearate caused no significant effects on the DPV response of vitamin B1. Hence, these compounds need not be extracted from these tablet ingredients or additives prior to their determination in tablets.
3.5.5 Analytical applications
Following the electroanalytical procedure described above, the developed method was used for the determination of vitamin B1 in a pharmaceutical formulation of commercially available tablets (Neurobion fort 10 mg, Neurokeme 100 mg, Vitneurin 100 mg and Becadexamin 10 mg). The analytical results achieved by the proposed DPV procedure are shown in Table 3 and are in good agreement with those reported in the literature for the analysis of the same pharmaceutical tablets.
3.6 Conclusion
The electrochemical reduction of vitamin B1 under the conditions described in this work is an irreversible process. The proposed differential pulse adsorptive stripping voltammetry (DPAdSV) method has distinct advantage over other existing methods. The proposed methods are sensitive, precise, accurate and rapid enough to be used in the routine analysis of vitamin B1 in pharmaceutical formulation. The limit of detection of the proposed method was found very low with respect to previous ones.
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