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Sensors and Actuators B 185 (2013) 301– 308

Contents lists available at SciVerse ScienceDirect

Sensors and Actuators B: Chemical

journa l h om epage: www.elsev ier .com/ locat e/snb

hemiluminescence microfluidic system on a chip to determine vitamin B1 usinglatinum nanoparticles triggered luminol–AgNO3 reaction

ohammad Kamruzzamana, Al-Mahmnur Alama, Sang Hak Leea,∗, Trung Dung Dangb

Department of Chemistry, Kyungpook National University, Daegu 702-701, South KoreaSchool of Mechanical Engineering, Yeungnam University, Gyeongbuk 712-749, South Korea

a r t i c l e i n f o

rticle history:eceived 3 September 2012eceived in revised form 15 March 2013ccepted 8 April 2013vailable online 2 May 2013

eywords:ab-on-a-chip

a b s t r a c t

A novel and sensitive chemiluminescence (CL) method on a microchip has been presented for thedetermination of vitamin B1 (VB1). The microchip was fabricated by soft lithographic procedure usingpolydimethyl siloxane (PDMS) having four inlets and one outlet with a 200 �m wide, 250 �m height,6 mm diameter and 100 mm long microchannel. The method is based on the enhanced CL intensity ofluminol by its oxidation with AgNO3 in the presence of platinum nanoparticles (PtNPs). It was foundthat the oxidation of luminol with AgNO3 by PtNPs produced strong CL signal at about 425 nm whichmeant that the luminophore was still 3-aminopthalate. The CL intensity of the luminol–AgNO3–PtNPs

hemiluminescenceuminolitamin B1gNO3

latinum nanoparticles

system was further increased with the addition of VB1. Under optimum conditions, the CL intensity wasincreased by increasing the concentration of VB1 in the range of 1.0 × 10−7 to 4.0 × 10−5 mol L−1 with acorrelation coefficient of 0.9992. The limit of detection was found to be 4.8 × 10−9 mol L−1 with the rel-ative standard deviation of 1.06%. The method was successfully applied to determine VB1 in vitamin B1tablets and vitamin B complex tablets. The interaction mechanism of the CL system has been proposedby UV–vis spectra and CL emission spectra.

© 2013 Elsevier B.V. All rights reserved.

. Introduction

Vitamin B1 (VB1), also called thiamine is a water soluble vitaminf B complex present in most plant and animal tissues. It consistsf an aminopyrimidine ring and a thiazole ring with methyl andydroxyethyl side chains linked by a methylene bridge. VB1 is aiologically and pharmaceutically essential compound for the car-ohydrate metabolism and maintenance of neural activity [1]. All

iving organisms need VB1 for their metabolism. It is also neces-ary for the proper functioning of the nervous, muscle, heart andardiovascular systems of the body [2,3]. It can also be used forhe prevention and treatment of beriberi or Wernicke–Korsakoff1]. Due to the functions and stability factors of VB1 in the body,t is necessary to develop a simple, low cost and sensitive analyt-cal method to determine VB1 in clinical analysis, food processingnd pharmaceutical formulations. There have been several reportsn the determination of VB1 including spectrophotometry [4–7],ravimetric analysis [8], electrochemical analysis [9–13], spec-

rofluorimetry [1,14–18], high performance liquid chromatography19–23], capillary electrophoresis [24–26], gas chromatography27,28], and chemiluminescence [29,30].

∗ Corresponding author. Tel.: +82 53 950 5338; fax: +82 53 950 6330.E-mail address: shlee@knu.ac.kr (S.H. Lee).

925-4005/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.snb.2013.04.029

Among the above methods, the chemiluminescence (CL)method represents high sensitivity with simple instrumentation,wide linear range and detection limit, rapidity in signal detectionand has been frequently used for the determination of phar-maceutical and biological samples. Recently metal nanoparticleshave attracted much attention in the field of analytical chemistrybecause of their excellent physical and chemical properties. Inthe CL system, nanoparticles can participate as catalysts, reduc-tants or luminophores. Metal nanoparticles have been extensivelyused as catalysts in the CL reaction to boost up the CL signalarising from the electronically excited states of the CL species.Several CL methods have already been presented describing thecatalytic activity of metal nanoparticles on CL reactions [31–38].The results of these studies demonstrate the potential applicationof metal nanoparticles catalyzed CL systems in analytical chem-istry.

In this study, we have presented a PtNPs catalyzed CL systemusing a luminol–AgNO3 system on a microfluidic chip to determineVB1 for the first time. In recent years, microfluidic devices havebeen used in a variety of applications including molecular biology,small-molecule organic synthesis, immunoassays, pharmaceutical

analysis and cell manipulation. Microfluidic chip-based CL systemhas been shown to have significant advantages over the macroscaleanalogs including improved efficiency with regard to reagent con-sumption, response times, analytical performance, integration,

302 M. Kamruzzaman et al. / Sensors and A

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2.5. Analytical procedure

Fig. 1. TEM image of the prepared colloidal PtNPs.

ystem control, increasing reliability, sensitivity through automa-ion, and the integration of multiple processes in a single device39]. In this work, we presented a microfluidic chip-based CL ofuminol oxidized by AgNO3 in the presence of PtNPs. Luminol canasily be oxidized by Ag+ by the catalytic activity of PtNPs to gen-rate a strong CL signal. The CL intensity of the luminol–Ag+–PtNPsas further enhanced significantly in the presence of VB1. Based on

he above results, we demonstrated a sensitive CL method coupledith a microfluidic system that enables the rapid and automatedetermination of VB1 using minute volumes of CL reagents andB1.

. Experimental

.1. Reagents and solution

All reagents were of analytical reagent grade and deionizedDI) water was used throughout the experiment. VB1, luminol,gNO3, and HPtCl4 were purchased from Sigma–Aldrich (St. Louis,SA). VB1 stock solution of 5.0 × 10−4 mol L−1 was prepared byissolving an appropriate amount of VB1 in DI water and pro-ected from light when kept in refrigerator. A 1.0 × 10−3 mol L−1

tock solution of luminol was prepared using 0.1 mol L−1 NaOH andtored at 4 ◦C. Stock solutions of AgNO3 (1.0 × 10−3 mol L−1) andPtCl4 (3.0 × 10−4 mol L−1) was prepared in DI water and stored

n a refrigerator before use. Working solutions were preparedaily from each of the stock solutions just before the experi-ent.

.2. Preparation of Pt nanoparticles

Platinum nanoparticles (PtNPs) were prepared according to theitrate reduction method described by Henglein et al. [40] withlight modification. Briefly, 5 mL of 1% sodium citrate was added to00 mL of boiling HPtCl4 (3.0 × 10−4 mol L−1) with constant stir-ing. The resulting solution was maintained at boiling for oneour with vigorous stirring. After one hour, brown colloidal PtNPsere obtained and the colloidal solution was cooled to room tem-erature. The PtNPs was then characterized by high resolutionransmission electron microscopic images (TEM) using a transmis-

ion electron microscope (TEM, Hitachi-7100, Japan). TEM showshe morphology of the PtNPs and the average diameter of the par-icles was approximately 2.0 ± 1 nm (Fig. 1).

ctuators B 185 (2013) 301– 308

2.3. Chip fabrication

The microfluidic chip was fabricated by a general soft-lithographic procedure with polydimethyl siloxane (PDMS, Sylgard184, Dow Corning) elastomer and a prepared chip mold. The chipmold was prepared by a general photolithographic process. Aschematic diagram of the microfluidic chip with the CL system isshown in Fig. 2. Briefly, a photoresist (PR, SU8-100) was spin-coatedonto a silicon wafer at 1000 rpm for 30 s to yield a 250-�m-thicklayer. Then the PR was baked and exposed under UV through apatterned mask. PDMS solution was prepared by mixing PDMSbase polymer and a cross-linking agent with a 10:1 wt% mixingratio. Air bubbles in the PDMS solution were removed under vac-uum for 1 h. To facilitate peel off of the PDMS replica from the chipmold, the surface of the chip mold was treated with tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane. The PDMS solution wasthen poured onto the chip mold and cured in an oven at 65 ◦C for2 h. After curing, the PDMS replica was peeled from the chip moldand holes were drilled using a stainless steel tube at the designedpositions of the four inlets and an outlet to connect plastic tubesfrom a syringe. The PDMS replica was then bonded onto anotherPDMS plate placed on a glass slide after plasma treatment of theirsurfaces using a plasma cleaner chamber for 2 min. The bondingbetween the same materials had good adhesion. Finally, polyte-trafluoroethylene (PTFE) tubing (0.4 mm i.d.) was connected to theprepared holes of the four inlets and the outlet and sealed withepoxy glue.

2.4. Apparatus

A schematic diagram of the microchip with the CL detectionsystem is shown in Fig. 2. The chip was fabricated with a microchan-nel having four inlets for the introduction of all reagents includingthe VB1 and one outlet with a 200 �m wide, 250 �m height,6 mm diameter and 100 mm long microchannel (Fig. 2). Two coiledshaped channels were constructed on the chip for better mixingof all CL reagents. The length of each coil is 40 mm and the vol-ume of the coil structure is 2 mm3. Length from meeting point of 3inlets to first coil-shape is 4 mm, between 2 coil structures is 8 mmand from the second spiral to outlet is 8 mm (Fig. 2). The reactiontime in each coil is around 1.5 s. Flow rates of all reagents throughthe microchannel were controlled by two syringe pumps (KDS-100, USA). Luminol, AgNO3 and sample were mixed well in thefirst coil-shaped microchannel and mixed with PtNPs in the secondcoil-shaped microchannel where the CL reaction was completedfollowed by the production of strong CL signal. The CL intensityproduced in the microchamber was detected and recorded using anF-4500 spectrofluorimeter (Hitachi, Japan) equipped with a photo-multiplier tube (PMT) (Model R 928, Hamamatsu, Japan) operatedat 950 V and placed close to the microchamber of the microfluidicchip. The light source of the spectrofluorimeter was switched offfor measurement of the CL intensity and the slit width of the emis-sion monochromator was set to 10 nm. The microfluidic chip wasplaced inside the detection chamber of the spectrofluorimeter andpositioned in front of the PMT. The second coil-shaped channel ofthe microfluidic chip, the main detection area of the generated CLintensity was directly faced to the window of the PMT with a dis-tance of approximately 1 cm between the microfluidic chip and thePMT. The entire setup was carefully shielded from ambient light. ApH meter (Orion 520A USA) was used for the pH adjustment. All theabsorption spectra were measured in UV-1800 (Shimadzu, Japan).

Four syringes loaded with 1.0 mL of the H2O/VB1, AgNO3, lumi-nol and PtNPs solution were fixed on syringe pumps P1 and P2

M. Kamruzzaman et al. / Sensors and Actuators B 185 (2013) 301– 308 303

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in the range of 0.01–0.35 mM. The CL intensity was increased byincreasing the concentration of luminol (Fig. 4b). However, higherconcentrations of luminol increased the background signal andlowered the signal-to-noise (S/N) ratio (Fig. S2, supplementary

400 45 0 50 0 55 0 60 0

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500

1000

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sity (

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Wave length (n m)

1

2

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ig. 2. Schematic diagram of the microfluidic chip with CL detector for the determiube; PC: personal computer.

espectively. The pumps were started to flush the entire systemithout sample until a steady baseline and good reproducibility of

he signal were achieved. The obtained CL signal was used as thelank signal. The sample was injected instead of H2O and mixedell in the first coil-shaped microchannel. Then the mixed solutionas interacted with PtNPs in the second coil-shaped microchannel

o produce a strong CL signal upon mixing. The emitted CL signalas captured by the PMT and recorded using a spectrofluorime-

er.

.6. Sample preparation

Five VB1 tablets (Biphane, Yuhan Co., Korea) and fifteen vita-in B complex tablets (Centrum, Wyeth Co., Korea) were first

round into fine powder. Then, 0.01 mg of VB1 tablet powdernd 0.06 mg of vitamin B complex tablet powder were taken andissolved in 0.001 mol L−1 hydrochloric acid, then transferred to

100 mL volumetric flask followed by dilution with DI water..5 mL from the above solution was taken to determine the amountf VB1 present in the tablets following the analytical proce-ure.

. Results and discussion

.1. Enhancement of luminol CL by PtNPs

The spectroscopic characteristics of the CL reaction were investi-ated in alkaline medium and are shown in Fig. 3. The CL intensityf the luminol–AgNO3 system was enhanced markedly by PtNPsFig. 3, curve 2) while luminol–AgNO3 produced a weak CL signalFig. 3, curve 1). It was found that the CL reaction occured quickly,nly 5 s was required for the maximum peak to appear after injec-ion of PtNPs into luminol–AgNO3 system (data not shown). In ordero confirm the activity of PtNPs, blank experiment was carried outsing citrate, luminol and AgNO3 and no enhancement effect was

ound. Therefore, it can be concluded that the increment of the CLignal of luminol–AgNO3 system was due to the catalytic activityf the PtNPs. The CL intensity of the luminol–AgNO3–PtNPs systemas further enhanced significantly in the presence of VB1 (Fig. 3,

of vitamin B1. P1, P2: syringe pumps; R: reaction chamber; PMT: photomultiplier

curve 3) and the CL intensity was increased with the concentrationof VB1.

3.2. Optimization of the CL reaction

The effects of the CL reaction conditions were investigatedand shown in Fig. 4. Luminol can produce CL signal in alkalineconditions, so the CL intensity mainly depend on the pH andthe concentration of the luminol. The effect of pH was inves-tigated in the range of 7.0–12.0. The CL intensity increased asthe pH increased, though only as far as 10.5, where further pHincreases caused the CL intensity to decline (Fig. 4a). At higherpH, the signal to noise ratio (S/N) was decreased (Fig. S1, sup-plementary material) and the background signal was increased.Thus, luminol with pH of 10.5 was chosen for the whole exper-iment. The effect of the concentration of luminol was examined

Fig. 3. CL emission spectra of the luminol–AgNO3–PtNPs–VB1 system. 1,luminol–AgNO3; 2, luminol–AgNO3–PtNPs; 3, luminol–AgNO3–PtNPs–VB1. Con-ditions: luminol, 0.22 mM (in 0.1 M NaOH); AgNO3, 0.04 mM; PtNPs, 0.2 mM;VB1, 1.7 × 10−6 mol L−1; pH, 10.5; flow rate, 25 and 35 �L min−1; scan speed,1200 nm min−1.

304 M. Kamruzzaman et al. / Sensors and Actuators B 185 (2013) 301– 308

7 8 9 10 11 120

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[Pt NPs] , mM

d

Fig. 4. The effects of (a) pH. Conditions, VB1, 1.7 × 10−6 mol L−1; luminol, 0.22 mM (in 0.1 M NaOH); AgNO3, 0.04 mM; PtNPs, 0.2 mM; flow rate, 25 and 35 �L min−1; scanspeed, 1200 nm min−1; n = 3 (three replicate measurement); S/N, 46; wavelength, 425 nm. (b) Luminol. Conditions: pH, 10.5; S/N, 36 and other conditions are as in (a) exceptluminol. (c) AgNO3. Conditions: luminol, 0.22 mM (in 0.1 M NaOH); S/N, 38 and other conditions are as in (b) except AgNO3. (d) PtNPs. Conditions: AgNO3, 0.04 mM; S/N, 33a

moToucTi0t0t0stgtatsPTotlo

intensity and the reagents consumption was also increased. Thus,the above flow rates were chosen for the whole experiment. Theeffect of the volume of the CL reagents was examined in therange of 10–50 �L. The highest CL intensity of the system was

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nd other conditions are as in (c) except PtNPs.

aterial). Therefore, in order to obtain the maximum S/N ratiof luminol, 0.22 mM luminol was selected for this experiment.he effect of NaOH concentration was also examined and webserved that the maximum CL intensity was obtained whensing 0.1 M NaOH in luminol solution. The effect of the con-entration of AgNO3 was tested in the range of 0.005–0.07 mM.he CL intensity and S/N ratio of the presented CL system wasncreased with the concentration of AgNO3 in the range of.005–0.04 mM and then started to decrease above this concen-ration (Figs. 4 and S3, supplementary material). AgNO3 above.04 mM may form AgOH precipitate in basic medium and coverhe PtNPs which reduces the CL signal. Therefore, AgNO3 of.04 mM was chosen for the subsequent experiments. The pre-ented CL system largely depends on the catalytic activity ofhe PtNPs. Thus, the concentration of the PtNPs might havereat influence on this CL reaction. The effect of the concentra-ion of PtNPs was investigated within the range of 0.01–0.3 mMnd the CL intensity was enhanced with increasing concentra-ions of the PtNPs (Fig. 4d). Considering the S/N ratio (Fig. S4,upplementary material) and reagent consumption, 0.2 mM of thetNPs colloidal solution was selected for the whole experiment.he effect of the reagents flow rate was examined in the range

f 10–50 �L min−1. The maximum CL intensity was obtained athe flow rates of 25 �L min−1 for VB1, AgNO3 and 35 �L min−1 foruminol and PtNPs. At higher flow rates, the CL reaction mightccur outside the reaction chamber leading to decrease the CL

Fig. 5. UV–vis absorption spectra, 1, AgNO3; 2, VB1; 3, PtNPs; 4, luminol; 5,luminol–AgNO3; 6, luminol–AgNO3–PtNPs; 7, luminol–AgNO3–PtNPs–VB1. Condi-tions: luminol, 0.22 mM (in 0.1 M NaOH); AgNO3, 0.04 mM; PtNPs, 0.2 mM; VB1,1.7 × 10−6 mol L−1.

M. Kamruzzaman et al. / Sensors and Actuators B 185 (2013) 301– 308 305

NH

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Scheme 1. Possible CL mechanism of the lum

btained using 10 �L of VB1, AgNO3 and 20 �L of luminol andtNPs.

.3. Possible mechanism of the CL reaction

In order to explore the possible CL reaction mechanism of theuminol–AgNO3–PtNPs–VB1 system, the UV–vis and CL emissionpectra were recorded and are shown in Figs. 3 and 5. Luminolhowed two absorption peaks at about 297 and 347 nm (Fig. 5,

gNO3–PtNPs system in the presence of VB1.

curve 4). When AgNO3 was mixed with luminol, two absorptionpeaks of equal intensity at the same wavelength were obtained(Fig. 5, curve 5) which meant that no obvious reaction occurredbetween luminol and AgNO3. After introducing the PtNPs into theluminol–AgNO3, the absorption peaks of luminol at 297 and 347 nm

increased (Fig. 5, curve 6), and the surface plasmon resonance (SPR)absorption band of PtNPs at 207 nm (data not shown) was littleincreased with little red shift. However, the light absorbed by themixed system was not equal to the sum of the light absorbed by

306 M. Kamruzzaman et al. / Sensors and Actuators B 185 (2013) 301– 308

Table 1Comparison of methods for the quantification of VB1.

Methods Linear range LODs Ref.

Spectrofluorimetry 1.0 × 10−8 to 1.0 × 10−4 mol L−1 4.3 × 10−9 mol L−1 [1]Spectrophotometry 1.7 × 10−5 to 1.7 × 10−5 mol L−1 a 2.0 × 10−6 mol L−1 a [7]Square wave voltammetry 1.0 × 10−6 to 4.0 × 10−3 mol L−1 1.0 × 10−7 mol L−1 [9]Square wave voltammetry 1.0 × 10−8 to 2.2 × 10−6 mol L−1 5.5 × 10−9 mol L−1 [11]Cathodic stripping voltammetry 1.0 × 10−6 to 1.0 × 10−4 mol L−1 2.0 × 10−7 mol L−1 [13]Spectrofluorimetry 8.3 × 10−9 to 3.3 × 10−6 mol L−1 b 2.6 × 10−9 mol L−1 b [15]Spectrofluorimetry coupled with FIA 3.0 × 10−8 to 2.7 × 10−5 mol L−1 c 2.6 × 10−8 mol L−1 c [16]Spectrofluorimetry 2.7 × 10−7 to 1.9 × 10−4 mol L−1 c 5.0 × 10−8 mol L−1 c [18]Chemiluminescence 1.7 × 10−7 to 2.7 × 10−5 mol L−1 c 3.3 mol L−1 c [30]On chip chemiluminescence 1.0 × 10−7 to 4.0 × 10−5 mol L−1 4.8 × 10−9 mol L−1 Presented method

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400

800

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1600

2000

CL

In

ten

sity (

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[VB1], mol L-1

co-existing substances to be tested. A chemical species is consid-ered to be interfering species when it produces an error greater than5%. The results obtained are summarized in Table 2. The results

Table 2Tolerance limit for co-existing substances in the determination of VB1.

Interfering substances Maximumtolerableconcentration ratio

Change in CLintensity (%)

Glucose, fructose, lactose, galactose 200 +1.7Starch, cellulose 100 +3.15

a mg L−1.b ng mL−1.c �g mL−1.

he two individual systems. Therefore, it is presumed that somehanges might be taken place between the mixing species aftereaction. The absorption intensity of the luminol–AgNO3–PtNPsas further increased at the same wavelength in the presence ofB1 (Fig. 5, curve 7), which meant that VB1 took part in enhancing

he CL signal of the luminol–AgNO3–PtNPs. As shown in Fig. 3 (curve), luminol–AgNO3 could not produce strong CL signal although Ag+

an oxidize luminol. AgNO3 is weak oxidant [41] and thus, no CLan be detected from the luminol–AgNO3 system. The CL intensityf the luminol–AgNO3 system was enhanced markedly at 425 nmn the presence of PtNPs (Fig. 3, curve 2) which was close agreement

ith the CL signal of the luminophore, excited 3-aminopthalate ion,n oxidation product of luminol. Thus, by the addition of PtNPs, itould not produce new luminophore, which mean the luminophoref the luminol–AgNO3–PtNPs CL system was still 3-aminopthalateon [42]. Therefore, the CL emitter of the CL reaction betweenuminol and AgNO3 with PtNPs is the same species as the oxi-ation product of luminol and showed enhanced CL intensity at25 nm. The CL intensity of the luminol–AgNO3–PtNPs system was

ncreased markedly by VB1 at the same wavelength (Fig. 3, curve 3)hich implied that 3-aminophthalate ion is still the luminophore

f the presented system.It could therefore be deduced that luminol was oxidized by

gNO3 in the presence of PtNPs to produce luminol radicals and theg+ was reduced to Ag0. The luminol radical then reacted with theissolved oxygen to produce excited 3-aminopthalate ions leadingo the CL. Thiol-containing compounds can react with dissolvedxygen to produce superoxide radicals which can react with lumi-ol radicals and produce CL signal [30]. Therefore, VB1 reactedith the dissolved oxygen and produced superoxide radicals which

eacted with luminol leading to the CL signal at 425 nm. The pos-ible reaction mechanism of the CL system catalyzed by PtNPs isrticulated as shown in Scheme 1.

.4. Analytical performance of the proposed method to determineB1

Under the aforementioned optimum conditions, a calibrationurve of CL intensity versus VB1 concentration was constructedy a series of standard solutions of VB1 pumped into the reactionhamber of the chip. The CL intensity showed a good linear rela-ionship with the concentration of VB1 in the range of 1.0 × 10−7 to.0 × 10−5 mol L−1 with a correlation coefficient of 0.9992 (Fig. 6).he limit of detection (LOD) as defined by IUPAC, CLOD = 3 × Sb/m,here Sb is the standard deviation of the blank signals and m is the

lope of the calibration graph, was found to be 4.8 × 10−9 mol L−1

ith the relative standard deviation of 1.06% for three replicateeterminations of 8.3 × 10−6 mol L−1 of VB1. The sensitivity inerms of LOD and linear range of the presented method is com-ared with some of the reported methods and shown in Table 1.

Fig. 6. Calibration curve of the CL reaction for the determination of VB1. Conditions:luminol, 0.22 mM (in 0.1 M NaOH); AgNO3, 0.04 mM; PtNPs, 0.2 mM; pH, 10.5; flowrate, 25 and 35 �L min−1; scan speed, 1200 nm min−1.

The developed method offers high sensitivity with minute reagentconsumption and analysis time. Therefore, the presented methodprovides a new CL system coupled with microfluidic chip to deter-mine VB1 quantitatively in the VB1 and vitamin B complex tabletsat lower concentration.

3.5. Effects of interfering substances

In order to investigate the selectivity of the proposed method,the effects of the potential interferants and some co-existing sub-stances that might be present in VB1 tablets and multivitamintablets was studied to determine VB1 by analyzing a standard solu-tion of 1.7 × 10−6 mol L−1 VB1 and different concentration of the

Magnesium stearate, gelatin, urea, 50 −4.75Riboflavin (VB2) 35 +2.1Pyridoxine hydrochloride (VB6) 20 −3.12Cyanocobalamin (VB12). 10 −3.9

M. Kamruzzaman et al. / Sensors and Actuators B 185 (2013) 301– 308 307

Table 3Determination of vitamin B1 in the commercially available vitamin B1 and vitamin B complex tablets.

Sample Amount (mg) Standard addition method

Claimed (mg/tablet) Founded by the proposedmethod (mg/tablet) ± SDa

Added (×10−7 g mL−1) Observed (×10−7 g mL−1) ± SDa Recovery (%)

Biphane 10 9.25 ± 0.311.0 1.03 ± 0.22 103.03.0 2.98 ± 0.15 99.35.0 4.88 ± 0.17 97.6

Centrum 2 2.11 ± 0.251.0 1.02 ± 0.19 102.03.0 3.15 ± 0.21 105.05.0

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a Standard deviation for five replicate measurements.

ndicated that most of the co-existing substances had little or noffect on the CL intensity of the proposed system in the determina-ion of VB1.

.6. Analytical application of the presented method

The proposed method was applied to determine VB1 in commer-ially available vitamin B1 tablets and vitamin B complex tablets toalidate the performance of the method. The results for the deter-ination of VB1 in the pharmaceutical samples are presented in

able 3. The amounts of VB1 obtained by the presented method aren good agreement with the claimed contents. Recovery studies

ere also performed on each of the analyzed samples. Recoveriesere found in the range of 97.6–103.0%, and 98.4–105.0% for VB1

ablets and vitamin B complex tablets respectively.

. Conclusion

We demonstrated a microfluidic chip based CL system for therst time to estimate VB1 in pharmaceutical preparations. Theethod is based on the enhanced CL of luminol and AgNO3 in the

resence of PtNPs. It was found that luminol was oxidized by AgNO3o produce luminol radical in the presence of PtNPs which furthereacted with dissolved oxygen and generated strong CL signal. TheL signal of the luminol–AgNO3–PtNPs was further increased byB1 and the CL intensity was enhanced by increasing the con-entration of VB1 in the range of 1.0 × 10−7 to 4.0 × 10−5 mol L−1

nd showed a relatively low LOD. Thus, the microchip-based CLethod exhibited advantages in terms of sensitivity, simplicity of

peration, wide dynamic range, low limit of detection and minuteeagents consumption. Therefore, the presented method can bepplied to determine vitamin B1 with satisfactory results.

cknowledgement

This work was supported by Kyungpook National Universityesearch Fund, 2013.

ppendix A. Supplementary data

Supplementary data associated with this article can be found, inhe online version, at http://dx.doi.org/10.1016/j.snb.2013.04.029.

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Biographies

Mohammad Kamruzzaman received his BSc (Hons) and MSc degree from thedepartment of Applied Chemistry and Chemical Engineering, University of Dhaka,Bangladesh in 2004 and 2006, respectively. Now he is pursuing his PhD at Spectro-chemical Analysis Lab, Department of Chemistry, Kyungpook National University,Daegu, Korea. His current research interest includes chemiluminescence microflu-idic sensor chip, flow injection chemiluminescence analysis, nano-materials basedfluorescence sensor, lanthanide-sensitized spectrofluorimetric method, electro-chemical sensor, and biosensor.

Al-Mahmnur Alam received his BSc (Hons) and MSc degree from the departmentof Chemistry, University of Dhaka, Bangladesh in 2005 and 2007 respectively. Nowhe is pursuing his PhD at Spectrochemical Analysis Lab, Department of Chemistry,Kyungpook National University, Daegu, Korea. His current research interest includeschemiluminescence microfluidic sensor chip, flow injection chemiluminescenceanalysis, nano-materials based fluorescence sensor, lanthanide-sensitized spec-trofluorimetric method, electrochemical sensor, and biosensor

Sang Hak Lee is a professor in the department of Chemistry, Kyung-pook National University, Daegu, Republic of Korea. He received his PhDin 1985 University of Saskatchewan, Canada. His research interests are flowinjection electro-chemiluminescence/chemiluminescence analysis, nano-materialsbased fluorescence sensor, lanthanide-sensitized spectrofluorimetric method,nanomaterial-based bio/chemical sensors, microfluidic chip-based analytical sys-tem, ICP-MS, capillary electrophoresis

Dr. Trung Dung Dang is a visiting researcher in School of Mechanical Engineer-ing, Yeungnam University, South of Korea and an assistant professor in School ofChemical Engineering, HUST, Vietnam. He received his BSc and MSc degree from

nam in 2003 and 2006, respectively. He obtained his PhD from Kyungpook NationalUniversity (South of Korea) in March 2012. His research focuses on microfluidicsdevices for chemical and electrochemical applications; micro-optofluidic devices,and nano-materials