Efficient hydrolysis of cellulose into glucose over sulfonated polynaphthalene (SPN) and rapid determination of glucose using positive corona discharge ion mobility spectrometry

Article abstract of DOI:10.1039/c5ra27325k

Sulfonated polynaphthalene (SPN) was successfully developed as solid acid catalysts for the hydrolysis of cellulose into high yields of glucose. The catalytic results indicate that the solid acid exhibits excellent activity, selectivity and recyclability. In addition two simple, rapid, selective, precise and accurate methods for the determination of glucose and cellulose were developed. The first method was based on the direct ion mobility spectrometry (IMS) measurements of glucose in reaction solution. The second method was based on UV-visible spectrophotometry, measurement of absorbance at 286 nm for cellulose.

Full text of DOI:10.1039/c5ra27325k

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Efficient hydrolysis of cellulose into glucose over
sulfonated polynaphthalene (SPN) and rapid
determination of glucose using positive corona
discharge ion mobility spectrometry†
Cite this: RSC Adv., 2016, 6, 7879
*
Fariborz Atabaki, Ebrahim Abedini and Arash Shokrolahi
Sulfonated polynaphthalene (SPN) was successfully developed as solid acid catalysts for the hydrolysis of
cellulose into high yields of glucose. The catalytic results indicate that the solid acid exhibits excellent
activity, selectivity and recyclability. In addition two simple, rapid, selective, precise and accurate
methods for the determination of glucose and cellulose were developed. The first method was based on
the direct ion mobility spectrometry (IMS) measurements of glucose in reaction solution. The second
method was based on UV-visible spectrophotometry, measurement of absorbance at 286 nm for cellulose.
Received 21st December 2015
Accepted 8th January 2016
DOI: 10.1039/c5ra27325k
www.rsc.org/advances
Moreover introduced chlorine group in to solid acids can be
improved catalytic activities. In these catalysts, chlorine groups
Introduction
act as cellulose binders by forming hydrogen bonds with
hydroxyl groups of cellulose and strongly acidic sulfonic groups
function as active sites for breaking b-1,4-glycosidic linkages of
cellulose.22–25 Recently, Tanemura and coworkers reported the
synthesis of a sulfonated polynaphthalene (SPN) with high acid
activities. This solid acid has some advantages. First, it contains
chlorine and sulfonic groups. Second, the catalyst is recoverable
without decreasing its activity and insoluble to boiling water
and many hot organic solvents. Third, it can be successfully
used instead of sulfuric acid as a catalyst.26
Detection and identication of carbohydrate in aqueous
solutions is very important in the several areas of environmental
research.27,28 Many methods have been developed to measure
the total concentration and type of carbohydrates including
colorimetric,29 chromatography,30 infrared spectroscopy,31
light scattering detection32 and nuclear magnetic resonance
spectroscopy.33 However these techniques oen are time
consuming, quite laborious, expensive and requires advanced
analytical skills.
Ion mobility spectrometry (IMS) is an analytical technique
that characterises chemical substances using gas-phase mobil-
ities of ions in homogenous electric eld. In this technique
different types of ions are separated based on their mass, size,
shape, and charge within a milliseconds time scale. IMS has
found widespread application as an analytical technique for
different organic and inorganic compounds such as drugs,
metal, biological compounds, pesticides and volatile and
explosives compounds. High sensitivity, simplicity, and short
response time are the major IMS advantages.34–39
Cellulose, the most abundant polysaccharide with b-glycosidic
linkage, is a major component of nonfood biomass. The
hydrolysis of polysaccharide, especially cellulose, to obtain
reducing sugars such as glucose (a major platform for the
synthesis of a variety of chemicals, fuel and food) is an impor-
tant process for chemical and biochemical industries.1–5
However, cellulose shows high chemical stability and insol-
ubility in most solvents because of its high crystallinity.
Therefore hydrolysis of cellulose to glucose with high selectivity
is one of the most attractive subjects in sustainable chemistry.6,7
Until now, many efforts have been devoted to the hydrolysis of
cellulose by using mineral acids,8–10 enzyme11,12 and supercrit-
ical water.13,14 However acid corrosion, high costs of enzyme,
severe controls of reaction conditions, production of chemical
waste, difficult separation of products and catalysts make this
method unattractive.
Solid acids are conventional materials that have wide
applications in chemical production, separation/purication,
and the chemical industry is currently searching for a highly
active and stable solid acid to improve the environmental safety
of the production of chemicals and energy.15–18
In recent years, several kind of solid acid have been devel-
oped to facilitate the hydrolysis of cellulose with moderate to
good glucose yields. Among them sulfonated carbon-based
solid acid showed superior catalytic activity.19–21
Chemistry Department, Malek-ashtar University of Technology, P. O. Box 83145-115,
Shahin-shahr, I. R. Iran. E-mail: arshokrolahi@gmail.com; ar_shokrolahi@mut-es.
ac.ir
In the present study we report the chemical conversion of
cellulose to glucose by hydrolysis of the SPN catalysts under
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra27325k
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relatively mild conditions and develop a new, simple, rapid, and
accurate IMS-based method for the direct determination of
glucose in reaction solution. In addition a UV-visible spectro-
photometric method was proposed for cellulose determination.
Experimental
All chemicals were commercial products. Absorption measure-
ments were made on a Perkin Elmer UV/vis Lambda 2 Spec-
trophotometer. Fourier transform infrared (FT-IR) spectra were
recorded on a Nicolet IMPACT 400D instrument. Scanning
electron microscopy images (SEM) were taken on SEM SERON
TECHNOLOGY AIS-2100. X-ray diffraction patterns (XRD) were
obtained on a Bruker D8 ADVANCE instrument. The elementary
analysis was obtained from Vario EL III of Elementar Company.
HPLC measurements were carried out on an Agilent 1200 series
(with a refractive index detector). The IMS used in this study was
constructed in Malek-Ashtar University of Technology, Iran,
Shahin-Shahr. The continuous corona discharge ionization
source with positive mode was used in this study. The optimized
experimental conditions for obtaining ion mobility spectra of
glucose are given in Table S1 (see ESI†). The ultrasonic
pretreatment was carried out in Ultrasonic Generator (TOP-
SONIC 10416) all sonication runs were at 20 kHz.
Fig.
particles.
1
The SEM image for the prepared pretreatment cellulose
The SEM analysis (Fig. 1) showed that the pretreated cellulose
particles exhibited an irregular morphology with the particle
size ranging from 0.5 to 20 mm.
Hydrolysis of cellobiose and cellulose
In a typical reaction, cellobiose (0.1 g) or pretreated cellulose
(0.05 g), catalyst (0.1 g), water (4 mL) or sulfuric acid 0.025 mol
Lꢂ1 (4 mL) and were added into Teon-lined stainless steel
autoclave and reacted at 120 ꢀC for prescribed time under
magnetic stirring. Then, the autoclave was cooled by cold water
immediately to avoid further reaction. The mixture was sepa-
rated by ltration or centrifugation. The yield of glucose was
calculated as follows:42
Catalyst preparation
The SPN catalysts was prepared according to the reported
procedure by Tanemura et al.26 In a typical synthesis, to
a magnetically stirred mixture of naphthalene (10.2 g, 80 mmol)
in nitrobenzene (140 mL), FeCl3 (28.6 g, 176 mmol) was added
at room temperature under nitrogen. Aer addition was
complete, the mixture was stirred at 80 ꢀC for 1 h and then
maintained at 150 ꢀC to form black solid. The mixture was
poured into 700 mL methanol containing a small amount of
concentrated HCl (3 mL). The mixture was ltered and washed
with methanol (3 ꢁ 20 mL), chloroform (3 ꢁ 20 mL) and then
the resultant polynaphthalene was nally dried at 120 ꢀC for 3 h
under reduced pressure.
Yield of glucose (%) ¼ (weight of glucose
ꢁ 0.9/weight of cellulose) ꢁ 100
Glucose selectivity (%) ¼
(yield of glucose/conversation of cellulose) ꢁ 100
In the sulfonation step, 4 mL of chlorosulfonic acid was
slowly added to the mixture of 2.5 g polynaphthalene in 60 mL
dichloromethane at room temperature under N2. Aer addition
was complete, the mixture was stirred for 24 h. Precipitated
sulfonated polymer was recovered, washed with distilled water
until pH reach values 6–7. The product was then dried in an
oven at 150 ꢀC for 4 h. The solid acid was characterized by XRD,
FT-IR and elementary analysis (see Fig. S1 and S2 in the ESI†).
The acid density (2.2 mmol gꢂ1) was measured using NaOH
(0.01 mol Lꢂ1) as titrant by acid–base potentiometric titration.
Adsorption of cellobiose and glucose on catalyst
0.1 g of each catalyst was added to 2 mL of aqueous cellobiose
(0.14 mol Lꢂ1) or glucose (0.28 mol Lꢂ1) solution and then
stirred at room temperature and the amount of adsorbed
cellobiose and glucose in supernatant was estimated by UV
spectrophotometry and IMS method respectively.
Hydrolysate analysis
The composition of the catalyst obtained was CH0.46Cl0.03
-
Glucose analysis was conducted using an ion mobility spec-
trometry system. Samples were solved in water to make stan-
dard solutions. 1 mL of the working solution was loaded on the
needle, the solvent was allowed to evaporate and then imme-
O
0.16S0.04 from elemental analysis.
Cellulose pretreatment
Prior to hydrolysis, microcrystalline cellulose (AVICEL®PH-101) diately inserted into the injection port of the IMS. UV spectro-
was pretreated by ultrasonic.40,41 Micro crystalline cellulose (5 g) photometry based method for determining cellulose was
was added in distilled water (200 mL) and sonicated at a power developed. In a typical reaction, about 0.05 g of cellulose was
of 350 W, frequency of 20 kHz for 45 min at room temperatures. taken in a test tube, added 3 mL of conc. sulfuric acid and was
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mixed for 45 minutes. Then the solution was further diluted to
250 mL with water and mixed well. Finally, UV light absorption
at 286 nm is read using UV spectrophotometer.
Cellobiose was determined using an UV spectrophotometry
system according to a method similar to that reported previ-
ously by Albalasmeh et al.43 A volume of 1 mL of 0.1 g Lꢂ1
cellobiose solution is rapidly mixed with 3 mL of concentrated
sulfuric acid in a test tube. Aer 1 min, test tube was cooled by
cold water to bring it to room temperature and absorbance was
measured at 315 nm.
Hydrolysis of cellulose
The catalytic performances of SPN were investigated in the
hydrolysis of cellulose to glucose and the optimizing reaction
conditions determined. In order to rationally evaluate the activity
of SPN catalyst in this reaction, a comparative study was made with
Amberlyst-15. In Table 1, we compared our result on the hydrolysis
of cellulose to glucose with data from some other workers. The
previously reported procedures suffer from one or more drawbacks
such as elevated reaction temperatures, low selectivity and yields of
glucose, low yield of cellulose conversion, long pretreatment time,
and the need for ionic liquids. Additionally, a comparison of
hydrolysis using pretreated cellulose with that using cellulose
(AVICEL®PH-101) was also conducted. The conversion and selec-
tivity for the pretreated cellulose was higher than that obtained
using un-pretreated cellulose (Table 1, entry 2).
Results and discussion
Hydrolysis of cellobiose
Hydrolysis of cellobiose as model compound for cellulose was
carried out at 120 ꢀC over 0.1 g of catalyst in cellobiose solution
(cellobiose 0.1 g, water 4 mL) and catalytic performance of SPN
was compared with Amberlyst-15. The specic surface area and
amount of sulfonic groups per gram of SPN catalyst was 20 m2
gꢂ1 and 2.1 mmol gꢂ1 vs. 50 m2 gꢂ1 and 4.8 mmol gꢂ1 for
Amberlyst-15. As shown in Fig. 2 approximately 95% cellobiose
was hydrolyzed to glucose in two hours while 39% was hydro-
lyzed by Amberlyst-15 at same conditions. Although the SPN has
a small surface area and acid density, this catalyst has much
greater catalytic activity than Amberlyst-15 in hydrolyzing
cellobiose. The high catalytic activity of the SPN can be attrib-
uted to increases in adsorption capacity.22–25 To conrm this
conjecture, adsorption of glucose and cellobiose on the SPN
surface was studied in aqueous solution at room temperature.
As shown in Fig. 2, 16.7% of the added cellobiose was absorbed
by the SPN within 2 h, whereas the Amberlyst-15 did not adsorb
cellobiose in water. Similarly, the SPN catalyst absorbed 7.0% of
the added glucose (less than the cellobiose absorbed by this
catalyst), and Amberlyst-15 did not adsorb glucose in water. The
adsorptive capacity of the SPN, suggests that –Cl, phenolic –OH
or –COOH groups are favorable for cellobiose (the shortest b-1-
4-linked polysaccharide) because more hydrogen bond formed
between the catalyst and cellobiose than glucose.20,22
Effects of the amount of catalyst
Fig. 3 shows the effects of catalyst amount on the cellulose
conversion. In the absence of acid catalyst, the conversion of
cellulose was only 5% aer 24 h of reaction. The results show
that the initial reaction rate and nal conversion were depen-
dent on the amount of catalyst and when the amount of catalyst
increased, the nal conversion increased as well.
ꢀ
Table 2 and 3 show glucose selectivity at 120 C for experi-
ments using different amount of catalyst. Increases in amount
of catalyst (0.1 g to 0.12 g) resulted in a decrease in glucose
selectivity from 90.8 (Table 2 entry 5) to 86.7% (Table 3 entry 5).
Effects of the temperature and time
The effects of temperature on cellulose conversion and glucose
yield under otherwise similar conditions were studied at 100,
120 and respectively 140 ꢀC and the results are illustrated in
Fig. 4 and Table 4. The results in Fig. 4 indicate that the yield of
cellulose conversion slightly increased (from 62.6% to 70.4%)
when the system temperature increased from 100 ꢀC to 120 ꢀC.
At 140 ꢀC, the yield rose noticeably to 79.6%. It is noted that
increases in temperature resulted in a decrease in the glucose
selectivity (see Table 2 and 4) additionally, a gradual increase in
the cellulose conversion was seen with increase in the duration
of the reaction time. The higher temperature helps to disrupt
partially the structure of cellulose and increase the accessibility
of glycosidic bond to the acid sites. Furthermore, the glucose is
not stable enough at higher temperature and degraded into
other products.
The effect of reaction period on the cellulose conversion and
glucose yield were studied at 120 and 140 ꢀC with 0.1 g catalyst
(SPN). The results are illustrated in Table 2 and 4. As seen from
the Table 2, 18 h of reaction completes 67.6% conversion with
90.8% selectivity whereas at the end of 24 h 86.6% of selectivity
was observed. It is clearly evident from the above observation
that 18 h may be the optimum period of this reaction.
Effects of the amount of water
In this study, the effect of the presence of water between 2 and
Fig. 2 Time courses for glucose formation from cellobiose and
adsorption curve of glucose and cellobiose.
10 mL was determined on the hydrolysis of cellulose at the
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Table 1 Comparison of the activity of various catalysts in the hydrolysis of cellulose to glucose
Catalyst/substrate
ratios (g per g)
t
T
Cellulose
Glucose
Glucose
selectivity (%) Ref.
Entry Catalyst
Substrate
(h) (ꢀC) conversion (%) yield (%)
1
2
3
4
5
6
7
8
SPN
SPN
Sonicated cellulose
Microcrystalline
Sonicated cellulose
Ball-milled
Microcrystalline
Ball-milled
2
2
2
18
18
18
24
3
24
4
24
120
120
120
150
100
150
155
120
67.6
51.3
10.3
43
61.4 (64.7)a 90.8 (95.7)
This work
This work
This work
19
20
21
23
24
20.4
—
39.7
—
Amberlyst-15
AC–SO3H
C–SO3H
CMK-3–SO3H
HA–CC–SO3H
SUCRA–SO3H
1.1
12
1.1
0.25
2
41
4
95.3
6.2
64
94.4
11.3
—
74.5
10.8
55
78.9
95.8
—
Microcrystalline
Ionic liquids
pretreated cellulose
9
Si33C66–823–SO3H Ball-milled
1
24
150
61
51
83.6
44
a
Yield was determined by HPLC.
Table 3 Hydrolysis of cellulose at 120 ꢀC and 0.12 g catalysta
Time
(h)
Cellulose
conversion (%)
Glucose
yield (%)
Glucose
selectivity (%)
Entry
1
2
3
4
5
6
7
8
10
12
14
16
18
20
22
24
46.7
57.9
64.9
69.1
72.1
72.4
73.5
74.4
31.3
42.2
50.4
57.2
62.5
62.2
62.8
60.9
67
72.9
77.6
82.8
86.7
85.9
85.4
81.8
a
Pretreated cellulose, 0.05 g; water, 4 mL.
Fig. 3 Effects of catalyst amount on the cellulose conversion (pre-
treated cellulose, 0.05 g; water, 4 mL; reaction temperature, 120 ꢀC).
Table 2 Hydrolysis of cellulose at 120 ꢀC and 0.1 g catalysta
Cellulose
Glucose
Glucose
Entry
Time (h)
conversion (%)
yield (%)
selectivity (%)
1
2
3
4
5
6
7
8
10
12
14
16
18
20
22
24
43.3
52.3
60.7
65.1
67.6
68.7
70.1
70.4
29.4
39.0
49.3
55.5
61.4
62.0
62.3
61.0
67.8
74.6
81.2
85.2
90.8
90.0
88.9
86.6
Fig. 4 Effects of hydrolysis temperature on the cellulose conversion
a
(pretreated cellulose, 0.05 g; catalyst, 0.1 g; water, 4 mL).
Pretreated cellulose, 0.05 g; water, 4 mL.
content. The conversion of cellulose and glucose yield increased
ꢀ
temperature of 120 C, reaction time of 18 h, and 0.05 g cellu- with increasing in amount of water up to 4 mL and aer that
lose over 0.1 g of catalyst (the best operational conditions decreased substantially. The glucose selectivity increased with
studied on this work which will give the best nal conversion increase in amount of water from 81.4% to 90.8%. Introduction
and glucose selectivity). Table 5 shows the relation between the of an optimum content of water is valuable for hydrolysis
amounts of cellulose conversion, glucose yield and water reaction and maintains the Brønsted acidity of the catalyst.
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Table 4 Hydrolysis of cellulose at 140 ꢀC and catalyst, 0.1 ga
Time
(h)
Cellulose
conversion (%)
Glucose
yield (%)
Glucose
selectivity (%)
Entry
1
2
3
4
5
6
7
8
10
12
14
16
18
20
22
24
58.6
65.1
69.8
72.6
75.0
75.9
76.6
79.6
43.0
50.6
56.3
62.7
60.0
60.4
59.5
58.7
73.4
77.8
80.6
86.4
80.0
79.6
77.7
73.7
a
Pretreated cellulose, 0.05 g; water, 4 mL.
Table 5 Effects of water amount on the cellulose conversion and
glucose selectivity
Fig. 5 The ion mobility spectra of the glucose and blank.
Cellulose
Glucose
Glucose
Entry
Water (mL)
conversion (%)
yield (%)
selectivity (%)
1
2
3
4
5
6
2
3
4
6
8
54.8
62.8
67.6
67.5
63.4
57.6
44.6
55.0
61.4
61.0
57.5
52
81.4
87.6
90.8
90.4
90.7
90.3
Table 6 Characteristic ions for glucose and blank ion mobility spectra
Reduced mobility, Ko
Dri time
t (ms)
Peak
(cm2 Vꢂ1 sꢂ1
)
+
10
NH4
3.04 ꢃ 0.09
1.58 ꢃ 0.04
1.48 ꢃ 0.04
4.30
8.83
8.26
Glucose (G1)
Glucose (G2)
Reusability of the catalyst
The stability of SPN was investigated by performing the
conversion of cellulose with the same catalyst. Aer the rst
run, the reusability of the SPN was tested. The recycled solid
acid was used for three times. The obtained results demon-
strating that SPN can be reused in these hydrolysis reactions
(see Table S2 in the ESI†).
Measurement of glucose concentrations
The ion mobility spectra of blank sample and glucose at the
optimum IMS conditions are shown in Fig. 5. Adding ammonia
to the carrier gas as the dopant improved sensitivity and
selectivity, furthermore reduced mobilities are calculated for
+
positive ion mode using (H2O)$nNH4 as an internal calibrant.
The blank spectrum show one peak with reduced mobility
values of 3.04 Vꢂ1 cm2 sꢂ1. The glucose spectrum shows two
peaks, G1 and G2, with reduced mobility values (Ko) of 1.58 and
1.48 cm2 Vꢂ1 sꢂ1, respectively. There is no reported reduced
mobility for product ions originated from glucose in the liter-
ature. Therefore the chemical formula of the product ions
cannot be fully without a mass spectrometer coupled to the IMS.
Table 6 presents the reduced mobility constant values and dri
time.
The calibration curves for the glucose obtained by plotting
their respective response (the area under corresponding peaks
for the glucose was considered as the response) against the
amount of glucose. Linear dynamic range is shown in Fig. 6.
Under optimum conditions, a linear calibration curve was
obtained for glucose from 50 to 400 ng. The equation for the
Fig. 6 Plots of IMS response against the amount of glucose.
analytical curve was y ¼ ꢂ6.2292 + 1.8113x. The correlation
coefficient (R2) and relative standard deviation percentage (RSD
(%) for 200 ng and n ¼ 6) are found to be 0.995 and 7.01%
respectively. Detection limit (DL) of this method for determi-
nation of glucose was 25 ng at a signal-to-noise ratio (S/N) of 3.
This result represent an improvement in sensitivity of more
than 100 times over that of refractive index detection (3–5
mg).45,46
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Measurement amounts of cellulose and cellobiose
Cellulose conversions were determined by UV spectrophotom-
etry based method. This new method was based on the direct
absorbance measurements of hydrolysis products of cellulose
formed by reaction with concentrated sulfuric acid. The treat-
ments with concentrated H2SO4 at room temperature, solubilize
the cellulose by breaking the hydrogen bonds between mole-
cules and the formation of glucose as the product. Then 5-
hydroxymethyl-2-furfural is produced by the dehydration of
glucose with sulfuric acid. We measured the UV absorption
spectrum
of
5-hydroxymethyl-2-furfural
in
aqueous
solution.43,47,48
The optimal conditions for the determination were: wave-
ꢀ
length 286 nm, temperature 25 C and reaction time 45 min.
Fig. 8 shows the spectra of hydrolysis products of cellulose (with
concentrations of 0.12 g Lꢂ1) in aqueous solution at the
optimum conditions.
The concentrations that were prepared for this study are: 0,
0.02, 0.04, 0.08, 0.12, 0.16, and 0.24 g Lꢂ1. A linear calibration
curve was obtained for cellulose from 0.02 to 0.24 g Lꢂ1. The
equation for the analytical curve was y ¼ ꢂ0.0244 + 5.9019x and
the correlation coefficient (R2) was 0.994. The detection limit
(DL) of cellulose in serum blank when using the optimized
conditions was determined 8 ꢁ 10ꢂ3 g Lꢂ1, demonstrating that
the method is sensitive enough to detect cellulose.
For real samples (hydrolysis of cellulose), the cellulose and
catalyst was recovered by ltration, washed thoroughly with
distilled water and nally acetone, and dried. Then, residue was
take in a test tube, added 3 mL of conc. sulfuric acid and was
mixed for 45 minutes. The solution was further diluted to 250
mL with water, mixed well and catalyst was removed by ltra-
tion. Finally, the absorbance of the resulting solution was
measured at 286 nm.
Fig. 7 The section of the watershed 3D plots of the ion mobility
spectra of glucose.
A typical watershed 3D plot of the ion mobility spectra of the
glucose in ltrate sample (real sample) is shown in Fig. 7. The
gure shows that the peak intensities are changed from the
injection time until the sample peaks disappear. The spectra
show a gradual increasing signal intensity aer a short period of
time, reach to maximum and then decay. This gure shows that
the ionic peaks of glucose do not overlap with each other's. The
standard additions method is used to determine amount of
produced glucose in the hydrolysis of cellulose. The recovery
percentages for two samples are listed in Table S3 (see ESI†).
Therefore, the experimental results demonstrated the potential
IMS method for the determination of glucose in samples and no
needs any separation technique in quantitative analysis of
glucose before the sample is introduced into the IMS.
In this work, standard addition method was used to deter-
mine amount of cellulose. The experimental results demon-
strated the potential UV spectrophotometry based method for the
determination of cellulose in samples (see Table S4 in the ESI†).
Absorbance of the cellobiose solutions were measured at 315
nm and the calibration graph was constructed. The concentra-
tions that were prepared for this study are: 0, 0.01, 0.02, 0.04,
0.08 and 0.1 g Lꢂ1. A linear calibration curve was obtained for
cellulose from 0.01 to 0.1 g Lꢂ1. The equation for the analytical
curve was y ¼ 0.0232 + 10.1422x and the correlation coefficient
(R2) and detection limit (DL) were 0.998 and 2.5 ꢁ 10ꢂ3 g Lꢂ1
,
respectively.
Conclusions
(1) The SPN exhibits high catalytic activity and stability for the
direct hydrolysis of cellulose under mild conditions, despite the
small surface area. The better catalytic activity can be attributed
to the ability to adsorb b-1,4-glucan.
(2) Ion mobility spectrometry was successfully applied to the
determination of glucose in aqueous samples. This method-
ology is simple and fast without using any separation
technique.
Fig. 8 UV spectrum of the hydrolysis products of cellulose.
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(3) In this study, UV spectrophotometry based method was 23 Q. Pang, L. Q. Wang, H. Yang, L. S. Jia, X. W. Pan and
successfully applied for determination of cellulose conversions. C. C. Qiu, RSC Adv., 2014, 4, 41212–41218.
The simplicity, ease of operation, good sensitivity and low cost 24 S. L. Hu, T. J. Smith, W. Y. Lou and M. H. Zong, J. Agric. Food
are advantages of the proposed method for the determination of
cellulose without using any separation technique.
Chem., 2014, 6, 1905–1911.
25 S. G. Shen, B. Cai, C. Y. Wang, H. M. Li, G. Dai and H. F. Qin,
Appl. Catal., A, 2014, 473, 70–74.
26 K. Tanemura, T. Suzuki, Y. Nishida and T. J. Horaguchi,
Appl. Polym. Sci., 2013, 127, 4524–4536.
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