CN106226304A - A kind of method utilizing acid-base indicator method to measure oligochitosan deacetylation - Google Patents

Abstract

The invention belongs to chemical field, be specifically related to a kind of method utilizing acid-base indicator method to measure oligochitosan deacetylation.The present invention measures the method for oligochitosan deacetylation and comprises the steps: that the moisture in S1, mensuration oligochitosan sample is as less loss weight under oligochitosan sample drying weightlessness item；S2, taking oligochitosan sample, after dissolving with distilled water, regulation pH value, to 8.0, adds dilute hydrochloric acid volumetric solution, is simultaneously added dropwise 1% bromocresol green indicator 12, is titrated to solution with sodium hydroxide titration liquid and becomes green and be titration end-point after mixing；S3, the deacetylation of calculating oligochitosan sample.The method that the present invention provides is a kind of method accurate, quickly mensuration oligochitosan deacetylation, simultaneously, the method that the present invention provides uses instrument simple, operation is simple, sample is without special pre-treatment, titration end-point judges that substantially measurement error is little, it is adaptable to the quality control in oligochitosan preparation process.

Description

A kind of method utilizing acid-base indicator method to measure oligochitosan deacetylation

Technical field

The invention belongs to chemical field, particularly relate to a kind of side utilizing acid-base indicator method to measure oligochitosan deacetylation Method.

Background technology

The homopolymer or different that oligochitosan is glucosamine and 2-Acetamido-2-deoxy-D-glucose is formed by connecting with β-Isosorbide-5-Nitrae glycosidic bond Polymers.Oligochitosan is the catabolite of chitosan, but compared with chitosan, it is more preferable that oligochitosan has dissolubility, and viscosity is the lowest more The advantage being easily absorbed by the body, has a wide range of applications in the field such as medicine, agricultural, fine chemistry industry.Oligochitosan not only has anti- The functions such as tumor, bacteriostasis antibiosis, antioxidation, also have fat-reducing, adjust the biological function such as fat, enhancing immunity.

The deacetylation of oligochitosan can affect the biology of oligochitosan, physics, chemical functional and activity, is that oligochitosan is various The embodiment of function, is one of important indicator weighing oligochitosan quality.The deacetylation of oligochitosan refers in oligochitosan total Removing the percentage ratio shared by saccharide residue number of acetyl group in saccharide residue number, the content of free amine group is then the base of its various function Plinth.

At present, the method measuring deacetylating degree of chitosan of report has much both at home and abroad: include alkalimetry (acid base titration Method, potentiometric titration, double hop titrimetry), infrared spectrometry, colloid titration method, refractive index, destruction sample method (element Analytic process, acid hydrolysis liquid analysis of hplc are analyzed with heat).Methyl orange acid-base indicator method measures deacetylating degree of chitosan and includes In 2015 editions " Chinese Pharmacopoeias ", and contain with the methyl orange-aniline blue (1: 2) the alkalimetry mensuration deacetylating degree of chitosan as indicator The method of amount is widely used, it has also become the Chinese Fishery industry standard methods that the Ministry of Agriculture promulgates.But use methyl orange or methyl Orange-aniline blue be the assay method of indicator for measuring oligochitosan deacetylation time also exist terminal colour change inconspicuous, Poor reproducibility, the shortcoming that error is bigger, the shell using methyl orange acid-base indicator method to measure according to 2015 editions " Chinese Pharmacopoeia " is few Sugar deacetylation error reaches more than 60%.Proton nmr spectra (¹H-NMR) as the gold mark measuring deacetylating degree of chitosan Standard, loaded American Pharmacopeia, meanwhile, paper " the Oligosaccharides and Their that Kim etc. delivers Derivatives " and the paper " quality analysis of the oligochitosan product of separate sources " delivered such as Wang Shixin disclose available Hydrogen nuclear magnetic resonance spectroscopy measures the deacetylation of oligochitosan, and measurement result error is little.But¹H-NMR method is due to its instrument cost High and operation needs technical professional, thus cannot be widely popularized use.

Through retrieval, prior art there are no the acid-base indicator method utilized using bromocresol green as indicator and measure shell widow The report of sugar deacetylation, the most not yet sets up the standard method of oligochitosan deacetylation.

Summary of the invention

In order to solve problems of the prior art, the invention provides one and utilize acid-base indicator method to measure shell widow The method of sugar deacetylation.The method that the present invention provides is a kind of method accurate, quickly mensuration oligochitosan deacetylation, with Time, the method that the present invention provides uses instrument simple, and operation is simple, and sample is sentenced without special pre-treatment, titration end-point Disconnected obvious, measurement error is little, it is adaptable to the quality control in oligochitosan preparation process.

The invention provides a kind of method utilizing acid-base indicator method to measure oligochitosan deacetylation, including walking as follows Rapid:

S1, the moisture measured in oligochitosan sample are as less loss weight under oligochitosan sample drying weightlessness item；

S2, taking oligochitosan sample, after dissolving with distilled water, regulation pH value, to 8.0, adds dilute hydrochloric acid volumetric solution, drips simultaneously Bromocresol green indicator 1-6 adding 0.1-1% is dripped, after mixing with sodium hydroxide titration liquid be titrated to solution become green be drip Determine terminal；

S3, the deacetylation of calculating oligochitosan sample, formula is as follows:

$D.D.\%=\frac{(N_{HC1}\×V_{HC1}-N_{NaOH}\×V_{NaOH1})\×0.016\×100\%}{G\×(100-W)\×9.94\%}$

In formula, D.D.% is deacetylation, %；N_HClFor the concentration of HCI liquid, mol/L；V_HClFor HCI liquid Volume, mL；N_NaOHFor the concentration of sodium hydroxide titration liquid, mol/L；V_NaOHFor the volume of sodium hydroxide titration liquid, mL；G is for supplying Test product is weighed, g；W is less loss weight, % under loss on drying item；0.016 is the amino amount that 1mol/L hydrochloric acid is suitable, g；9.94% For theoretical amino content.

Further, the concentration of described oligochitosan sample is 6-10mg/mL.

Further, the concentration of described dilute hydrochloric acid volumetric solution is 0.1-0.5mol/L.

Further, the consumption of described indicator be 1% bromocresol green indicator 1-2 drip.

Further, described sodium hydroxide titration liquid concentration is 0.1-0.5mol/L.

Compared with prior art, the present invention has the beneficial effect that:

(1) method utilizing acid-base indicator method mensuration oligochitosan deacetylation of present invention offer, can accurately, quickly Ground measures oligochitosan deacetylation, and the method that the present invention provides uses instrument simple, and operation is simple, and sample is without special Pre-treatment, titration end-point judges substantially, and measurement error is little, it is adaptable to the quality control in oligochitosan preparation process.

(2) method utilizing acid-base indicator method mensuration oligochitosan deacetylation of present invention offer, makees with bromocresol green For indicator, the change of titration end-point color substantially, can accurately judge titration end-point, reduce evaluated error.

(3) inventor is during research acid-base indicator method measures oligochitosan deacetylation, by substantial amounts of Research finds, the mensuration of sample deacetylation is had a very big impact by oligochitosan pH value of water solution, in oligochitosan aqueous solution, and second Acylamino-just reaches the state completely dissociating out when pH 8.0, now utilizes acid-base indicator method to measure oligochitosan and takes off second Acyl degree, accuracy is high, and causes negative error when oligochitosan aqueous solution pH is less than 8.0, causes positive error when pH is more than 8.0.

Accompanying drawing explanation

Fig. 1 mean molecule quantity≤1000 daltonian oligochitosan (COS_MW1000) hydrogen nuclear magnetic resonance spectrogram (500MHz), its In, A-E represents C2-C6 position feature hydrogen signal on sugar ring.

Fig. 2 mean molecule quantity≤3000 daltonian oligochitosan (COS_MW3000) hydrogen nuclear magnetic resonance spectrogram (500MHz), its In, A-E represents C2-C6 position feature hydrogen signal on sugar ring.

Detailed description of the invention

Below by specific embodiment, the present invention is described in further detail, and protection scope of the present invention is not only It is confined to following example.

Raw materials used in the embodiment of the present invention being commercially available prod, wherein, the equipment component model related to and source are as follows:

Title	Manufacturing enterprise
		S-25 current potential pH meter	Shanghai Lei Ci precision scientific instrument company limited
DK-8D type one thousandth electronic analytical balance	Sai Duolisi group of Germany
		SartouriusMA150 infrared moisture meter	Sai Duolisi group of Germany
Bruker500MHz nuclear magnetic resonance analyser	Brooker company of Germany

Embodiment 1 acid-base indicator method measures oligochitosan deacetylation

S1, weighing 0.5g oligochitosan sample and measure its moisture in infrared moisture meter, record result is as this Less loss weight under batch oligochitosan sample drying weightlessness item；

S2, take oligochitosan sample 0.5g, accurately weighed, accurate add 50mL distilled water, under room temperature, stirring makes it the most molten Solving, adjust pH value to 8.0, precision adds the dilute hydrochloric acid volumetric solution 18mL of 0.3mol/L, is simultaneously added dropwise the bromocresol green indicator of 1% 1-2 drips, and is titrated to solution with the sodium hydroxide titration liquid of 0.15mol/L and becomes green and be titration end-point after mixing；

S3, the deacetylation of calculating oligochitosan sample, formula is as follows:

$D.D.\%=\frac{(N_{HC1}\×V_{HC1}-N_{NaOH}\×V_{NaOH1})\×0.016\×100\%}{G\×(100-W)\×9.94\%}$

In formula, D.D.% is deacetylation, %；N_HClFor the concentration of HCI liquid, mol/L；V_HClFor HCI liquid Volume, mL；N_NaOHFor the concentration of sodium hydroxide titration liquid, mol/L；V_NaOHFor the volume of sodium hydroxide titration liquid, mL；G is for supplying Test product is weighed, g；W is less loss weight, % under loss on drying item；0.016 is the amino amount that 1mol/L hydrochloric acid is suitable, g；9.94% For theoretical amino content.

Respectively to COS_MW1000(deacetylation >=90%, the oligochitosan sample of mean molecule quantity≤1000), COS_MW3000(de- Acetyl degree >=90%, the oligochitosan sample of mean molecule quantity≤3000) carry out deacetylation mensuration, the results are shown in Table 1, table 2.

Table 1COS_MW1000Deacetylation measurement result

According to table 1 it is known that COS_MW1000The method provided by the present invention, recording its deacetylation D.D. value is 93.38%, RSD are 0.28 (n=6).

Table 2COS_MW3000Deacetylation measurement result

According to table 2 it is known that COS_MW3000The method that provided by the present invention of oligochitosan sample, record it deacetylated Degree D.D. value is 92.64%, and RSD is 0.53 (n=6).

Comparative example 1¹H-NMR method measures deacetylation

1)¹H-NMR method measures deacetylation

Precision weighs 20mg COS respectively_MW1000And COS_MW3000It is dissolved in the D of 5mL₂In O (99.96%), obtaining concentration is The sample solution of 4mg/mL, is transferred to gained sample solution in 8mm nuclear magnetic tube be measured, and resonant frequency is 500MHz, surveys Fixed temperature is 297k, finally to echo signal integration, and the wherein hydrogen signal of acetyl group in the acetamido of C2 position on sugar ring (Acetyl-H) at 1.9-2.1ppm, on sugar ring, C2-C6 position hydrogen signal is at 2.6-6.0ppm.COS_MW1000, COS_MW3000Nuclear-magnetism Resonance hydrogen spectrogram is shown in Fig. 1, Fig. 2 respectively.According to table 3, being integrated hydrogen nuclear magnetic resonance spectrogram correspondence peak, deacetylation calculates public affairs Formula is:

D.D (%)={ 1-[(7*A₂)/(3*A₁)]}*100

Wherein, A₂Represent on sugar ring the integrated value of 3 hydrogen signals of acetyl group in the acetylamino of C2 position；A₁Represent on sugar ring The integrated value of C2-C6 position hydrogen signal.

Oligochitosan deuterium-oxide solution Hydrogen Proton chemical shift at 3 25 DEG C of table

Utilize¹H-NMR method records COS_MW1000, COS_MW3000Corresponding deacetylation measurement result is respectively 93.52 ± 0.13 (n=6), 92.81 ± 0.07 (n=6).

2)¹H-NMR method and the contrast of acid-base indicator method measurement result of the present invention

¹H-NMR method is shown in Table 4 with the comparing result of acid-base indicator method measurement result of the present invention.

Table 4¹H-NMR contrasts (n=6) with acid-base indicator method measurement result of the present invention

Sample	1H-NMR (%)	Bromocresol green indicator method (%)	Relative error
				COSMW1000	93.52±0.13	93.38±0.28	0.14±0.15
COSMW3000	92.81±0.07	92.64±0.53	0.17±0.46

As can be seen from Table 4, the measurement result of acid-base indicator method of the present invention mensuration oligochitosan deacetylation is relative Error is less than 0.2%, with¹The measurement result of H-NMR method is consistent.Illustrate that the acid-base indicator method that the present invention provides is used for measuring shell Oligosaccharide deacetylation accuracy is high.

Comparative example 2 methyl orange acid-base indicator method measures oligochitosan deacetylation

COS is measured with reference to the assay method of deacetylating degree of chitosan in 2015 editions " Chinese Pharmacopoeia "_MW1000And COS_MW3000's Deacetylation, measurement result is as shown in table 5 and table 6.

Table 5COS_MW1000Deacetylation measurement result

Table 6COS_MW3000Deacetylation measurement result

From table 5 and the result of table 6, the assay method of deacetylating degree of chitosan in 2015 editions " Chinese Pharmacopoeias " is utilized to survey Obtain COS_MW1000、COS_MW3000Corresponding deacetylation is respectively 30.39 ± 0.70,30.32 ± 0.56, with utilization¹H-NMR method is surveyed The COS obtained_MW1000、COS_MW3000Corresponding deacetylation 93.52 ± 0.13,92.81 ± 0.07 is compared, and has the survey of more than 60% Determine error.

Chitosan sample aqueous solution is colourless solution, and its isoelectric point, IP is about 3.88, and methyl orange pH color change interval is at 3.1- 4.4, and acid color is red, alkali formula color is yellow, therefore, utilizes determination of acid-basetitration using methyl orange as acid-base indicator The deacetylation of chitosan, titration end-point is obvious, and measurement error is little, and accuracy is high.And for oligochitosan, on the one hand, shell Oligosaccharide sample aqueous solution itself presents faint yellow, uses methyl orange as indicator so that titration end-point cannot accurately judge；Separately On the one hand, oligochitosan isoelectric point, IP value is about 4.80, beyond methyl orange pH color change interval, therefore, according to 2015 editions " middle traditional Chinese medicines Allusion quotation " use methyl orange acid-base indicator method measure oligochitosan deacetylation error the biggest.Bromocresol green pH color change interval exists 3.8-5.4, acid color is yellow, and alkali formula color is green (aeruginous), uses bromocresol green as the instruction of acid-base indicator method Agent, the change of titration end-point color substantially, can accurately judge titration end-point, thus can significantly reduce evaluated error.

Comparative example 3 phenolphthalein acid-base indicator method measures oligochitosan deacetylation

With reference to the assay method of deacetylating degree of chitosan in 2015 editions " Chinese Pharmacopoeias ", measure using phenolphthalein as indicator COS_MW1000And COS_MW3000Deacetylation, measurement result is as shown in table 7 and table 8.

Table 7COS_MW1000Deacetylation measurement result

Table 8COS_MW3000Deacetylation measurement result

From table 7 and the result of table 8, record COS using phenolphthalein as indicator_MW1000、COS_MW3000Corresponding is deacetylated Degree is respectively 66.72 ± 0.23,62.01 ± 0.29, with utilization¹The COS that H-NMR method records_MW1000、COS_MW3000Corresponding de-second Acyl degree 93.52 ± 0.13,92.81 ± 0.07 is compared, and there is the evaluated error of about 30%.

The investigation of comparative example 4pH

Inventor, in research process, is found by substantial amounts of research, and oligochitosan pH value of water solution is to oligochitosan The mensuration of sample deacetylation has a very big impact.

Inventor, with reference to the assay method of deacetylating degree of chitosan in 2015 editions " Chinese Pharmacopoeias ", uses bromine cresol The green indicator as acid-base indicator method measures COS_MW1000And COS_MW3000Deacetylation, titration end-point color change bright Aobvious, thus significantly reduce evaluated error, but with¹The assay method of H-NMR method is compared, and the mensuration still with more than 10% is missed Difference.

Finding in research process, by oligochitosan, preparation technology is affected, and the pH value of the aqueous solution of commercially available oligochitosan is 5.12 Left and right, presents faintly acid.Oligochitosan is a kind of basic amine group polysaccharide, if its aqueous solution presents faintly acid, utilizes acid-base indicator When method measures its deacetylation, inherently cause evaluated error.

PH is investigated to acid-base indicator under conditions of pH value change, other condition determinations and method are same as in Example 1 Method measures the impact of the measurement result of oligochitosan deacetylation, the results are shown in Table 9.

The impact (n=6) on oligochitosan deacetylation measurement result of the table 9 oligochitosan aqueous solution difference pH value

pH

7.60

7.80

7.90

8.00

8.10

8.20

D.DMW1000(%)

87.45±0.18

90.94±0.21

91.64±0.31

93.44±0.13

95.62±0.20

97.65±0.25

D.DMW3000(%)

88.14±0.19

89.86±0.20

90.82±0.16

92.69±0.11

94.25±0.18

97.12±0.23

According to the result of table 9, the mensuration of oligochitosan sample deacetylation is had the biggest by oligochitosan pH value of water solution Impact, reason is probably acetylamino in sour environment and is combined with hydrochloric acid and defines oligochitosan hydrochlorate, makes acetylamino Can not dissociate out completely, thus cause bigger evaluated error.Along with the change of solution acid-basicity, acetylamino is slowly swum Separating out, reach the state the most completely dissociating out when pH=8.00, pH<8.00 causes negative error, pH>8.00 just cause Error.

Above content is to combine concrete preferred implementation further description made for the present invention, it is impossible to assert Being embodied as of the present invention is confined to these explanations.For general technical staff of the technical field of the invention, On the premise of present inventive concept, it is also possible to make some simple deduction or replace, all should be considered as belonging to the present invention's Protection domain.

Claims (5)

1. one kind utilizes the method that acid-base indicator method measures oligochitosan deacetylation, it is characterised in that: comprise the steps:

S1, the moisture measured in oligochitosan sample are as less loss weight under oligochitosan sample drying weightlessness item；

S2, taking oligochitosan sample, after dissolving with distilled water, regulation pH value, to 8.0, adds dilute hydrochloric acid volumetric solution, is simultaneously added dropwise Bromocresol green indicator 1-6 of 0.1-1% is dripped, and is titrated to solution with sodium hydroxide titration liquid and becomes green and be titration after mixing Terminal；

S3, the deacetylation of calculating oligochitosan sample, formula is as follows:

$D.D.\%=\frac{\left(N_{HC1}\&times;V_{HC1}-N_{NaOH}\&times;V_{NaOH1}\right)\&times;0.016\&times;100\%}{G\&times;\left(100-W\right)\&times;9.94\%}$

In formula, D.D.% is deacetylation, %；N_HClFor the concentration of HCI liquid, mol/L；V_HClBody for HCI liquid Long-pending, mL；N_NaOHFor the concentration of sodium hydroxide titration liquid, mol/L；V_NaOHFor the volume of sodium hydroxide titration liquid, mL；G is test sample Weigh, g；W is less loss weight, % under loss on drying item；0.016 is the amino amount that 1mol/L hydrochloric acid is suitable, g；9.94% is reason Opinion amino content.

The method utilizing acid-base indicator method to measure oligochitosan deacetylation the most according to claim 1, it is characterised in that: The concentration of described oligochitosan sample is 6-10mg/mL.

The method utilizing acid-base indicator method to measure oligochitosan deacetylation the most according to claim 1, it is characterised in that: The concentration of described dilute hydrochloric acid volumetric solution is 0.1-0.5mol/L.

The method utilizing acid-base indicator method to measure oligochitosan deacetylation the most according to claim 1, it is characterised in that: The consumption of described indicator be 1% bromocresol green indicator 1-2 drip.

The method utilizing acid-base indicator method to measure oligochitosan deacetylation the most according to claim 1, it is characterised in that: Described sodium hydroxide titration liquid concentration is 0.1-0.5mol/L.