matrix solid-phase dispersion with chitosan-zinc oxide nanoparticles combined with...

J. Sep. Sci. 2014, 00, 1–7 1

Mostafa Khajeh1

Hongyuan Yan2

Esmat Arefnejad1

Mousa Bohlooli3

1Department of Chemistry,University of Zabol, Zabol, Iran

2Key Laboratory ofPharmaceutical Quality Controlof Hebei Province, College ofPharmacy, Hebei University,Baoding, China

3Department of Biology,University of Zabol, Zabol, Iran

Received July 4, 2014Revised July 30, 2014Accepted August 8, 2014

Research Article

Matrix solid-phase dispersion withchitosan-zinc oxide nanoparticles combinedwith flotation-assisted dispersiveliquid–liquid microextraction for thedetermination of 13 n-alkanes in soil samples

In this study, chitosan-zinc oxide nanoparticles were used as a sorbent of miniaturizedmatrix solid-phase dispersion combined with flotation-assisted dispersive liquid–liquid mi-croextraction for the simultaneous determination of 13 n-alkanes such as C8H18 and C20H42

in soil samples. The solid samples were directly blended with the chitosan nanoparticlesin the solid-phase dispersion method. The eluent of solid-phase dispersion was appliedas the dispersive solvent for the following flotation-assisted dispersive liquid–liquid mi-croextraction for further purification and enrichment of the target compounds prior to gaschromatography with flame ionization detection. Under the optimum conditions, good lin-earity with correlation coefficients in the range 0.9991 < r2 < 0.9995 and low detection limitsbetween 0.08 to 2.5 ng/g were achieved. The presented procedure combined the advantagesof chitosan-zinc oxide nanoparticles, solid-phase dispersion and flotation-assisted dispersiveliquid–liquid microextraction, and could be applied for the determination of n-alkanes incomplicated soil samples with acceptable recoveries.

Keywords: n-Alkanes / Dispersive liquid–liquid microextraction / Soil / Solid-phasedispersionDOI 10.1002/jssc.201400732

� Additional supporting information may be found in the online version of this articleat the publisher’s web-site

1 Introduction

Environmental pollution caused by petroleum hydrocarbonsis the most common pollution issue encountered by environ-mentalists. In recent years, environmental contamination ofpetroleum substances has increased with the industrial de-velopment and growing energy demands. The most commonfunctional categories of compounds in petroleum productsare n-alkanes, which are harmful to the nervous system, causeskin damage, and can cause peripheral neuropathy [1–3].

The necessity of pretreatment method was not explainedsufficiently. After all, some detection means, for exam-ple, HPLC–MS and GC–MS, could determine trace levelsof these contaminates. In order to determine trace levelsof these contaminants, a preconcentration and extraction

Correspondence: Dr. Mostafa Khajeh, Mofateh Street, Zabol, Sis-tan and Baloochestan 98615-538, Islamic Republic of IranE-mail: [email protected]: +98-542-2226765

Abbreviations: DSPE, dispersive solid-phase extraction; FA-

DLLME, flotation-assisted dispersive liquid–liquid microex-traction; SPD, solid-phase dispersion; ZN, chitosan-zinc oxidenanoparticles

steps are necessary. Farajzadeh and Matin [2] have studiedPVC-activated charcoal fibers coated on silver wire with theheadspace method for n-alkanes preconcentration in soil sam-ples. Khalili Zanjani et al. [1] have reported the analysis ofn-alkanes in water samples by headspace solvent microextrac-tion. SPME has some disadvantages such as (a) the polymercoating is fragile and easily broken, and (b) the sample carry-over is sometimes difficult or impossible to be eliminated [4].Headspace sampling has also some disadvantages such as(a) high-molecular-mass and other nonvolatile molecules can-not be extracted by this method (b) the other limitation on thesolvent is that its vapor pressure must be low enough to avoidevaporation during sampling, furthermore, when aqueoussamples have to be analyzed, if the solvent is miscible withwater, the drop size may increase, causing the drop to fallfrom the needle [5].

A sample clean-up method termed dispersive solid-phaseextraction (DSPE) has been introduced by Anastassiadeset al. [6], in which the crude extract was cleaned up by ad-dition of a small amount of sorbent material to an aliquotof the extract to remove the matrix co-extractives. The main

Colour Online: See the article online to view Figs. 1–5 in colour.

C© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com

2 M. Khajeh et al. J. Sep. Sci. 2014, 00, 1–7

advantages of the procedure include high recoveries for awide range organic compounds, high sample throughput,and inexpensive methods that need less labor and organicsolvents [7]. However, the DSPE procedure cannot be usedfor concentrating the target compounds. Thus, to achieve suf-ficient sensitivities for the analysis of trace level target com-pounds, additional concentration methods are often required.In this study, the flotation-assisted dispersive liquid–liquidmicroextraction (FA-DLLME) method was used to improvethe sensitivity of DSPE and to enhance the selectivity of theFA-DLLME by combining DSPE with FA-DLLME.

In recent years, there is an increasing interest in the ap-plication of nanoparticles as sorbents for extraction of targetcompounds. Semiconductor nanoparticles have much atten-tion because of their novel electrical, optical, and mechanicalproperties. Among different semiconductor nanoparticles,zinc oxide nanoparticles are the most frequently reportedbecause of their applications. Due to the large specific area,nanoparticle sorbents have a higher efficiency for the extrac-tion of target compounds [8]. Hybrid materials such as metalnanoparticles based on chitosan have been developed becausegood properties of individual components and outstandingsynergistic influence simultaneously [9].

DLLME is a preconcentration method in which a ternarysystem of solvents is used. In this system, an appropriatemixture of extraction and dispersive solvents is rapidly in-jected into an aqueous solution, resulting in a cloudy systemcontaining fine droplets of the extraction organic solvent dis-persed in the liquid phase, which increases the contact areabetween phases remarkably and reduces the extraction timewith the increasing pre-concentration factors [10–16]. Afterextraction, phase separation is performed by centrifugation,and the enriched target compounds in the organic phaseare determined by spectrometry or chromatography meth-ods. The advantages of this technique are simplicity, rapidity,low cost, high efficiency, and high enrichment factor.

This research represents the first attempt to use chitosan-zinc oxide nanoparticles (ZN) as solid-phase dispersion (SPD)sorbent to develop a new ZN-SPD-FA-DLLME–GC methodfor the extraction and determination of 13 n-alkanes (C8H18–C20H42) in soil samples.

2 Materials and methods

2.1 Reagents and samples

n-Alkanes, acetonitrile, chloroform, methanol,dichloromethane, and acetone were obtained from Merck(Darmstadt, Germany). Ethanol, cyclohexane, toluene, andbenzene were purchased from Merck (Darmstadt, Germany).A stock standard solution of n-alkanes (100 �g/mL) wasprepared in acetone and stored in glass-stoppered bottlesin the dark at 4�C. For the optimization experiments andquantitative analysis, a blank soil sample was collected froma farm near the University of Zabol. The blank soil wasdried in an oven at 130�C for four days in order to remove

any organic solvent trace and moisture, and there was noother residue by survey. The blank samples obtained werechecked to be free of the target n-alkanes before spiking. Themethod used to spike the target samples was as follows: aportion of 20 g of soil was place in a 100 mL vial and analiquot of an n-alkanes solution in acetone was added (thefinal concentration of target samples was 50.0 ng/g). Thevial was sealed hermetically and shaken vigorously for 1 hto achieve perfect homogenization of the compounds in thematrix. The samples were stored at 4�C for 20 days to allowthe interaction among compounds and the matrix to takeplace and then obtain samples that would resemble naturalsoils as much as possible. Real soil samples were taken fromthe vicinity of petrol pump stations in the area of Zabol andthe Persian Gulf.

2.2 Apparatus

GC analyses were carried out using a GC system (Hewlett–Packard 6890, Palo, Alto, CA, USA) equipped with a30 m × 0.32 mm i.d. with 0.25 �m stationary film thicknessHP-5 capillary column and flame ionization detection. Thefollowing temperature program was used: 40�C for 2 min thenprogrammed raising 8�C/min to 120�C. Afterward, raised at20�C/min to 260�C, and then held for 5 min. Other operatingconditions were as follows: carrier gas, helium (99.999%);injector temperature, 260�C; detector temperature, 270�C,and splitless mode. A 5.0 �L Hamilton microsyringe (Reno,Nevada, USA) was employed for injection into GC.

2.3 Preparation of ZN

1.0 g of zinc oxide was dissolved in 100 mL solution of 1%acetic acid to obtain zinc cations. Then, 1 g of chitosan wasadded into this solution and the mixture was sonicated for30 min. After that, 1 mol/L NaOH was added dropwise untilthe solution reached to pH 10. The solution was heated inwater bath at 60�C for about 3 h. Finally, it was filtered andwashed with deionized water for several times, and dried inan oven at 50�C for 1 h [17].

2.4. Characterization of ZN adsorbent

The representative SEM images of ZN and TEM imagesof zinc oxide nanoparticles are shown in Fig. 1. Support-ing Information Fig. S1 shows the schematic method of theFA-DLLME procedure. A mixture of ethanol (as dispersivesolvent) and 200 �L of cyclohexane (as extraction solvent)were added to the home-made microextraction cell. After that,10 mL of water was added to this solution. After 2 min, usingN2 flotation, the organic solvent was separated as a floatinglayer on the surface of the solution.

FTIR spectra (Perkin-Elmer Spectrophotometer) in therange 400 to 4000 cm−1 were studied. To study the pure


J. Sep. Sci. 2014, 00, 1–7 Gas Chromatography 3

Figure 1. (A) SEM image of chitosan-zinc oxide nanoparticles and(B) TEM image of zinc oxide nanoparticles.

chitosan and chitosan-ZnO nanoparticle, the FTIR was ap-plied (Supporting Information Fig. S2). The spectrum ofchitosan (Supporting Information Fig. S2a) exhibited differ-ences from that of chitosan-ZnO nanoparticles (SupportingInformation Fig. S2b). The major differences were as follows:the wide peak at 3418 cm−1, corresponding to the stretchingvibration of hydroxyl, amino and amide groups, moved tolower wave numbers (3405 cm−1), which indicated the inter-action between these groups and ZnO. The decrease of theband related to primary NH2 groups at 1350–1650 and 3300–3500 cm−1 is an indicative of ZnO immobilization onto thechitosan. A new broad absorption band at the range of 400–500 cm−1 was found in the FTIR spectra of chitosan-ZnOnanoparticle composite, which were ascribed to the vibrationof O–Zn–O groups.

2.5 Procedure of ZN-SPD-FA-DLLME

In this study, 0.1 g portion of homogenized sample and 0.2 gsorbent of ZN were placed in a small glass beaker and blendedtogether to be ground. The 0.3 g homogenized mixture wastransferred into an empty cartridge (5 cm × 8 mm i.d.,

prepacked with 50 mg of nanoparticles that acted as matrixsolid phase dispersion sorbent to further remove interferingmatrix components and isolate analytes to achieve high recov-eries [18]) and rinsed with ethanol (also the dispersive solventin FA-DLLME). A mixture of ethanol (as dispersive solvent)and 200 �L of cyclohexane (as extraction solvent) was addedto the homemade microextraction cell. After that, 10 mL ofwater was added to this solution. After 2 min, using N2 flota-tion, the organic solvent was separated as a floating layer onthe surface of the solution. A 1 �L volume of cyclohexanephase was injected into the GC–FID for analysis.

2.6 Calculation

The preconcentration factor is defined as follows:

PF = Cf .a

Ci.s(1)

where Cf.a is the final concentration in the acceptor phaseand Ci.s is the initial concentration of target compounds inthe sample solution. Cf.a was calculated from a calibrationgraph obtained from direct injection of target compoundsstandard solutions.

Extraction recovery (R%) is defined as follows:

R% = Ce × Ve

C0 × Vaq× 100 (2)

where Ce and C0 are the concentration of the analyte in theextraction solvent and the initial concentration of analyte inthe aqueous sample, respectively, and Ve and Vaq are thevolumes of the extraction solvent and the aqueous sample,respectively.

3 Results and discussion

3.1 Optimization of SPD in application of n-alkanes

analysis

One of the outstanding advantages of SPD is that the extrac-tion and clean-up are performed in only one step. In SPD, thesorbent acts both as an abrasive material and a bound solventwhich breaks the sample composition and disperses samplecomponents and further promotes more effective interactionbetween the sorbent and the target compounds [18]. In thisstudy, sample/sorbent ratio could affect the interface areabetween the analytes and sorbent, and plays an importantrole in the purification of samples. Thus, the ratio of sam-ple/component ranging from 1:1 to 1:3 w/w were evaluated(the conditions of FA-DLLME were as follows: dispersive sol-vent volume, 1.0 mL; extraction solvent (cyclohexane), 150 �L;sample volume, 8.0 mL; extraction time, 2 min, and amountof salt (NaCl), 1 mol/L), and the results (Fig. 2) showed thebest recoveries of n-alkanes when the sample/component ra-tio was up to 1:2. Further increasing the proportion of sorbent



Figure 2. Effect of sample/sorbent ratioson the recovery of n-alkanes.

the recoveries of n-alkanes is nearly constant. Thereby, 1:2was used as the optimized ratio of sample and sorbent in thesubsequent studies. Also, the ZN prepacked in the bottom ofthe cartridge acted as SPD sorbent to further remove inter-fering matrix components and isolate target compounds tocarry out high recoveries.

The recovery of ZN was compared to alumina, silica, andC18. Figure 3 shows that the recoveries of analytes by ZNwere slightly higher than alumina, silica, and C18. Perhapsbecause chitosan contains a large number of ring structures.The intramolecular and intermolecular hydrogen bonds wereformed by the –OH and –NH2 in the chitosan. When ZnOwas introduced, the intermolecular hydrogen bonds wereweakened and new hydrogen bonds were formed betweenchitosan and ZnO. Thereby, a stable complex of chitosan-ZnO nanoparticles is formed [9]. This hybrid material hasbeen developed due to excellent properties of individual com-ponents (chitosan and ZnO nanoparticles) and outstandingsynergistic effects. One of the most apparent advantages forpolymer–inorganic nanoscale hybrids is good adsorption ca-pacity and good chemical stability due to ease of function-alization through different polymeric units. Moreover, theremarkable resistance of the polymeric groups and their link-age to acid and to base hydrolysis are an additional advantageto use them as ligand carrying polymers [8]. The interactionbetween sorbent and target compound is probably physicaladsorption or Van der Waals interaction [8].

A satisfactory elution solvent was essential since the ana-lytes should be efficiently desorbed while the remaining ma-trix components should be retained on the cartridge. In thiscase, different kinds of elution solvents including methanol,acetone, acetonitrile, and ethanol were evaluated. The averagerecovery for methanol, acetone, acetonitrile, and ethanol were48.2, 52.9, 50.3, and 53.3%, respectively. Therefore, ethanolwas used as an elution solvent. Thereby, the n-alkanes wereextracted from soil samples into ethanol by SPD method, andthe extract was then used as dispersive solvent in FA-DLLMEprocedure. Also, the dispersive solvent must be miscible withaqueous phase and the extraction solvent (the conditions ofFA-DLLME were as follows: volume of dispersive solvent,1.0 mL; volume of extraction solvent (cyclohexane), 150 �L;volume of sample, 8.0 mL; time of extraction, 2 min; andamount of salt (NaCl), 1 mol/L).

The selection of a suitable extraction solvent is of greatimportance for the FA-DLLME method. The primary require-ments of extraction solvent are as follows: it should havea lower density than water, and low solubility in water soas to prevent the dissolution in the aqueous phase, a goodaffinity to target compounds, it should show good chromato-graphic performance, and also it must be miscible in thedispersive solvent. Based on these criteria, some extractionsolvents such as cyclohexane, toluene, and benzene wereinvestigated in this study. The average recovery for cyclo-hexane, toluene, and benzene were 54.1, 46.9, and 45.8%,

Figure 3. Comparison of ZN with alumina,silica, and C18 sorbent.



Figure 4. The effect of dispersive solventvolume on the extraction recovery of n-alkanes.

respectively. Therefore, cyclohexane was selected as the ex-traction solvent.

3.2 Effect of dispersive solvent volume

For the optimization of the dispersive solvent volume, theexperiments were carried out by using various volumes ofdispersive solvent of ethanol (0.5 to 2.5 mL) and fixed volumeof the extraction solvent cyclohexane (250 �L). According tothe results (Fig. 4), R% is increased by increasing ethanol vol-ume, from 0.5 to 2.0 mL, while decreased when continue toincreasing ethanol volume. At higher volumes of dispersivesolvent, the dispersion of the extraction solvent in water wasincreased, so the recoveries of volume of extraction solventcontaining target analyte would decrease. Therefore, 2.0 mLof ethanol was chosen as the optimum volume of the disper-sive solvent.

3.3 Effect of extraction solvent volume

The volume of extraction solvent is another significant fac-tor that could affect the extraction ability. In this work, the

influence of extraction solvent volume (50 to 250 �L) on theextraction recoveries of the analytes were studied while fixedvolume of dispersive solvent (2.0 mL) was used. Figure 5shows that by increasing the volume of cyclohexane from50 to 200 �L, the recoveries were increased, and after thatfrom 200 to 250 �L the recovery was decreased, this decreaseis probably due to the increased volume of organic phase.Therefore, 200 �L of cyclohexane was used in subsequentexperiments.

3.4. Effect of extraction time and salt addition

In traditional LLE, the extraction time is important and ex-pected to affect the extraction recovery. In this work, the effectof extraction time, in the range of 1–10 min was tested. Theresults revealed that the extraction time has no importanteffect on the R%. It is clear that the surface area betweenthe aqueous phase and cyclohexane is very large. Therefore,transition of the target compound from the aqueous phase tothe cyclohexane is fast. This is the most important advantageof FA-DLLME. Thereby, 2 min was chosen as the extraction

Figure 5. The effect of extraction solventvolume on the extraction recovery of n-alkanes.



Table 1. Comparison of FA-DLLME with HLLME (n = 10)

Method R% RSD%

FA-DLLME 93.5–96.1 1.9–3.5HLLME 87.9–91.2 3.2–6.1

Extraction conditions were as follows: extraction solvent (cy-clohexane) volume, 200 �L; dispersive/homogeneous solvent(ethanol) volume, 2.0 mL; amount of salt (NaCl), 1.0 mol/L.

time and blowing time of N2. Also, the effect of NaCl in therange of 0.0 to 2.0 mol/L was investigated as a salting agent.The results showed that an increase in recovery with theincrease of the salt concentration from 0.0 to 1.0 mol/L wasobserved and after that from 1.0 to 2.0 mol/L the recovery wasconstant. Therefore, 1.0 mol/L of sodium chloride was usedin subsequent experiments.

From all experimental observations, the optimized condi-tions were selected to be extraction solvent, cyclohexane; dis-persive solvent, ethanol; extraction solvent volume, 200 �L;dispersive solvent volume, 2.0 mL; amount of salt (NaCl),1.0 mol/L; and sample/sorbent ratio, 1:2.

3.5 Evaluation of method performance

The analytical figures of merit were obtained under optimalconditions (Supporting Information Table S1). Good linearitywas obtained for all the compounds at concentration withinthe interval tested (10–100 ng/g), and the determination co-efficient (R2) was in the range of 0.9991–0.9995. The regres-sion equations are presented and summarized in Support-ing Information Table S1. Precision (RSD%) was studiedby performing repeatability and reproducibility studies. Therepeatability was studied by intraday analysis (n = 10) ofan extract from a soil sample spiked at a concentration of20 ng/g. Supporting Information Table S1 shows that thevalues between 1.9 and 3.5% were acquired. In order to eval-uate the reproducibility of the method, ten various aliquotsof soil sample were spiked at a concentration of 20 ng/g, ex-tracted and analyzed in triplicate on interdays over a period often days. Supporting Information Table S1 shows the resultsobtained, with values ranging from 2.5 to 6.3%. The LOD,based on S/N = 3 and the limits of quantification (S/N = 6)ranged from 0.08 to 2.5 and 0.16 to 5.0 ng/g, respectively. Thevolumes of ethanol and sample solution were 2 and 10 mL, re-spectively. Thus, the maximum obtainable preconcentrationfactor is 60 for all compounds. This method was comparedto other procedures (Supporting Information Table S2). Ac-cording to the results, LOD (0.08–2.5 ng/g) and RSD% (1.9–3.5%) of this method were improved and better than previousworks. Therefore, this procedure is a good method for ex-traction of n-alkane from soil samples. Under the optimizedconditions (as discussed above), FA-DLLME was comparedto homogeneous liquid–liquid microextraction as typical mi-croextraction technique (Table 1 and Supporting Information T

ab

le2

.D

eter

min

atio

no

fth

en

-alk

anes

ind

iffer

ent

soil

sam

ple

s(s

pik

edw

ith

n-a

lkan

esat

aco

nce

ntr

atio

no

f20

ng

/g)

Sam

ple

Octa

neN

onan

eDe

cane

Unde

cane

Dode

cane

Trid

ecan

eTe

trade

cane

Pent

adec

ane

Hexa

deca

neHe

ptad

ecan

eOc

tade

cane

Non

adec

ane

Icos

ane

Sam

ple

1Fo

und

20.1

10.6

9.2

16.5

9.6

11.9

––

––

––

–RS

D%2.

52.

73.

13.

62.

93.

52.

85.

94.

32.

83.

95.

54.

2R%

95.6

101.

191

.994

.593

.710

2.5

96.1

94.3

95.2

92.1

90.4

92.7

91.5

Sam

ple

2Fo

und

18.5

20.7

12.8

18.9

7.5

9.9

15.7

20.6

17.6

12.7

8.5

7.9

–RS

D%3.

22.

45.

14.

43

2.9

6.2

3.4

2.7

2.5

3.9

4.7

2.8

R%96

.493

.810

0.8

96.1

92.6

95.3

102.

491

.996

.794

.396

.195

.310

1.6

Sam

ple

3Fo

und

21.5

018

.14

10.3

015

.70

8.10

9.7

10.2

13.1

17.3

4.5

–10

.2RS

D%2.

92.

82.

62.

53.

92.

75.

62.

43.

94.

84.

95.

14.

8R%

95.6

95.1

96.2

92.9

94.3

93.7

95.4

94.6

90.9

101.

310

1.6

94.1

102.

1



Fig. S3). FA-DLLME has better R% and RSD% than homo-geneous liquid–liquid microextraction based on ten replicateexperiments.

To evaluate the accuracy and applicability of the proposedprocedure for real soil samples, the extraction, and determi-nation of the n-alkanes in various soil samples were carriedout. To assess the effects of matrix, the soil was spiked withn-alkanes at a concentration of 20 ng/g. Supporting Informa-tion Fig. S4 shows the chromatogram of the real sample 1after spiking with 20 ng/g of n-alkanes. Table 2 representsthe recoveries of three replicate analyses of each soil sampleswhich were 90.4–102.5% with RSD � 6.2%.

4 Conclusion

This study represented the first attempt to use ZN as a se-lective SPD sorbent to develop a new ZN-SPD-FA-DLLME–GC method for the selective extraction and determination of13 n-alkanes in soil samples. Due to the absence of inter-nal diffusion resistance and the large specific area, nanopar-ticle sorbents have a higher efficiency for the removal ofpollutants. The presented ZN-SPD-FA-DLLME method com-bines the advantages of ZN, SPD, and FA-DLLME and couldbe potentially applied for the determination of n-alkanes incomplicated soil samples. The FA-DLLME method was suit-able for the usage of low-density extraction solvent such asbenzene, toluene, and cyclohexane. The new method of FA-DLLME is different from the normal DLLME method whichdoes not require centrifugation to separate the organic ex-traction phase. Gas flotation has been applied to break upthe organics in water emulsion and to finish the extractionprocess.

The authors have declared no conflict of interest.

5 References

[1] Khalili Zanjani, M., Yamini, Y., Shariati, S., J. Hazar.Mater. B 2006, 136, 714–720.

[2] Farajzadeh, M., Matin, A. A., Anal. Sci. 2002, 18, 77–81.

[3] Farajzadeh, M., Hatami, M., Anal. Sci. 2002, 18, 1221–1225.

[4] Ulrich, S., J. Chromatogr. A 2000, 902, 167–194.

[5] Xu, L., Basheer, C., Lee, H. K., J. Chromatogr. A 2007,1152, 184–192.

[6] Anastassiades, M., Lehotay, S. J., Stajnbaher, D.,Schenck, F. J., J. AOAC Int. 2003, 86, 412–431.

[7] Wu, Q., Li, Z., Wang, C., Wu, C., Wang, W., Wang, Z.,Food Anal. Methods 2011, 4, 559–566.

[8] Khajeh, M., Laurent, S., Dastafkan, K., Chem. Rev. 2013,113, 7728–7768.

[9] Li, L. H., Deng, J. C., Deng, H. R., Liu, Z. L., Xian, L.,Carbohydrate Research 2010, 345, 994–998.

[10] Cabuk, H., Akyuz, M., Ata, S., J. Sep. Sci. 2012, 35, 2645–2652.

[11] Khajeh, M., Musavi Zadeh, F., Bull. Environ. Contam. Tox-icol. 2012, 89, 38–43.

[12] Song, G., Zhu, C., Hu, Y., Chen, J., Cheng, H., J. Sep. Sci.2013, 36, 1644–1651.

[13] Farajzadeh, M. A., Khorram, P., Alizadeh Nabil, A. A., J.Sep. Sci. 2014, 37, 1177–1184.

[14] Smitiene, V., Semasko, L., Vickackaite, V., J. Sep. Sci.2014, 37, 1989–1995.

[15] Sun, J., He, H., Liu, S., J. Sep. Sci. 2014, 37, 1679–1686.

[16] Dong, S., Huang, G., Lu, J., Huang, T., J. Sep. Sci. 2014,37, 1337–1342.

[17] AbdElhady, M. M., Int. J. Carbohydr. Chem. 2012, 2012,1–6.

[18] Yan, H., Wang, H., Qiao, J., Yang, G., J. Chromatogr. A2011, 1218, 2182–2188.

[19] Farajzadeh, M., Hatami, M., J. Sep. Sci. 2003, 26, 802–808.


matrix solid-phase dispersion with chitosan-zinc oxide nanoparticles combined with...

Documents