阅读说明：本技术 一种基于衍生化的奶粉中4种人乳寡糖及其定性定量方法 (Derivatization-based milk powder containing 4 human milk oligosaccharides and qualitative and quantitative method thereof ) 是由 梁鑫淼 李欣 闫竞宇 李佳齐 郭志谋 叶贤龙 金高娃 于 2019-10-12 设计创作，主要内容包括：本发明涉及一种基于衍生化的奶粉中4种人乳寡糖及其定性定量方法。其特征是：将奶粉样品进行前处理,然后用衍生化试剂对前处理后奶粉样品中的4种人乳寡糖进行衍生化,再经亲水作用色谱(HILIC)实现奶粉样品中目标人乳寡糖的同时分析。同时根据4种衍生化人乳寡糖衍生物在本分析体系下所绘制的标准曲线,得到奶粉中目标人乳寡糖的绝对含量信息。该方法具有选择性好,稳定性好,操作简便可控,时间短等特点,适用于奶粉和婴儿配方奶粉样品的快速、高通量分析。(The invention relates to 4 human milk oligosaccharides in milk powder based on derivatization and a qualitative and quantitative method thereof. The method is characterized in that: pretreating a milk powder sample, then derivatizing 4 human milk oligosaccharides in the pretreated milk powder sample by using a derivatization reagent, and simultaneously analyzing the target human milk oligosaccharides in the milk powder sample by using hydrophilic interaction chromatography (HILIC). And meanwhile, obtaining the absolute content information of the target human milk oligosaccharide in the milk powder according to a standard curve drawn by the 4 derived human milk oligosaccharide derivatives under the analysis system. The method has the characteristics of good selectivity, good stability, simple and controllable operation, short time and the like, and is suitable for rapid and high-throughput analysis of milk powder and infant formula milk powder samples.)

1. A method for quantifying 4 human milk oligosaccharides in derivatized milk powder is characterized by comprising the following specific steps:

(1) pretreating a milk powder sample, and then derivatizing 4 human milk oligosaccharides in the pretreated milk powder sample by using a derivatization reagent;

(2) separating and analyzing the human milk oligosaccharide derived in the step (1) by using hydrophilic interaction chromatography (HILIC), and recording a chromatogram and peak area;

(3) taking more than 3 different masses of 4 human milk oligosaccharide standards, sequentially carrying out derivatization in the step (1) and separation analysis in the step (2), recording a chromatogram and a peak area, carrying out linear regression calculation on the masses X (mg) by using the peak area Y to obtain a linear regression equation or a standard curve of the derivatized human milk oligosaccharide, and respectively substituting the peak areas of the 4 human milk oligosaccharides obtained in the step (2) into the corresponding linear regression equation or standard curve to obtain the absolute content information of the target human milk oligosaccharide in the milk powder sample;

the 4 human milk oligosaccharides comprise:

2’FL(2’-Fucosyllactose)：Fucα1-2Galβ1-4Glc

LNnT(Lacto-N-Neotetraose)：Galβ1-4GlcNAcβ1-3Galβ1-4Glc

3’SL(3’-Sialyllactose)：Neu5Acα2-3Galβ1-4Glc

6’SL(6’-Sialyllactose)：Neu5Acα2-6Galβ1-4Glc。

2. the quantification method according to claim 1, wherein the 4 human milk oligosaccharides comprise:

2’FL(2’-Fucosyllactose)：Fucα1-2Galβ1-4Glc

LNnT(Lacto-N-Neotetraose)：Galβ1-4GlcNAcβ1-3Galβ1-4Glc

3’SL(3’-Sialyllactose)：Neu5Acα2-3Galβ1-4Glc

6’SL(6’-Sialyllactose)：Neu5Acα2-6Galβ1-4Glc

linear regression calculation of the mass X (mg) with peak area Y,

the linear regression equation of 2' FL is Y70000X +52200, R²＝0.9991；

The linear regression equation of LNnT is that Y is 30000X-1821.8, R²＝0.9999；

The linear regression equation of 3' SL is that Y is 29524X +884.67, R²＝0.9997，

The linear regression equation of 6' SL is that Y is 29742X +706.18, R²＝0.9998。

3. The quantitative method as set forth in claim 1, wherein the pretreatment step in the step (1) is: taking milk powder, adding water and/or an organic solvent for dissolving to prepare a 1-2000mg/mL sample solution, adding 1-5 times of volume of the organic solvent for uniformly mixing, standing for 2-48 hours at 0-10 ℃, centrifuging for not less than 5 minutes at 500-10 ℃ for 50000g, taking out supernatant, adding an adsorbing material according to 1-100% of the mass of the milk powder for further removing residual protein and other low-polarity substances, carrying out vortex oscillation for not less than 5 seconds, centrifuging for not less than 5 minutes at 500-10 ℃ for 50000g, collecting supernatant, centrifuging for 1-5 times, and evaporating to dryness to obtain an oligosaccharide protein-removed sample in the milk powder; the organic solvent is one or more of ethanol, acetone, methanol, acetonitrile, isopropanol and n-butanol.

4. The quantification method according to claim 1, wherein the derivatization process in step (1) comprises: adding a derivatization reagent, sodium cyanoborohydride, DMSO and a glacial acetic acid solution into the pretreated milk powder sample, reacting for 15min-5h at 25-100 ℃, and standing for 0.5-60 min at-10-10 ℃ after the reaction is finished to terminate the reaction; the derivatization reagent is one or two or three of anthranilamide, anthranilic acid and 2-aminoacridone;

according to the mass of 50-100mg of the milk powder, after pretreatment, 100. mu.L of derivatization reagent (0.35-1mol/L) and sodium cyanoborohydride (1-2mol/L) reaction liquid are added, and the solvent is DMSO: glacial acetic acid (V/V) ═ 50:50-70: 30.

5. The quantification method according to claim 1, wherein the step (2) of performing the analysis of the 4 derivatized human milk oligosaccharides by using HILIC technology comprises: performing analysis by adopting one-step or/and multi-step hydrophilic interaction chromatography; eluting with water and organic solvent or buffered saline solution and organic solvent as mobile phase by isocratic and/or gradient method, and detecting.

6. The quantitative method as claimed in claim 1, wherein the HILIC column of step (2) is filled with silica gel or a filler of silica gel surface bonded with polar groups, wherein the bonded polar groups are one or more of amino acids, amides, amino groups, carboxyl groups, glycosyl groups, zwitter ions and the like.

7. The quantitative determination method according to claim 5, wherein the organic solvent in the mobile phase is one or more of methanol, acetonitrile, ethanol, isopropanol and acetone.

8. A method of quantification according to claim 5, characterized in that the buffer salt types selected and their concentration and pH in the mobile phase are as follows:

a) ammonium formate buffer salt, concentration 2-200mM, pH 2-7;

b) ammonium acetate buffer salt at a concentration of 2-200mM, pH 2-7;

c) ammonium bicarbonate buffer salt with concentration of 2-200mM and pH of 6-10;

the ratio of mobile phase water or buffer saline solution and organic solvent as eluent is 5/95-95/5.

9. A method of quantification as claimed in claim 5, 6, 7 or 8, characterized by: optimizing chromatographic operating parameters including flow rate, column temperature and detector, the specific operations are as follows:

a) the flow rate is 0.1-2BV/min

b) The inner diameter of the chromatographic column is 2.1-10mm

c) The column temperature is 15-60 DEG C

d) The detector is one or more than two of a fluorescence detector, an ultraviolet detector and a mass spectrum detector.

10. The quantification method according to claim 1, wherein the milk powder samples in step (1) comprise one or more of milk powder of different brands and infant formula.

Technical Field

The invention relates to 4 human milk oligosaccharides in milk powder based on derivatization and a qualitative and quantitative method thereof. The method is characterized in that: pretreating a milk powder sample, then derivatizing with a derivatization reagent, and simultaneously analyzing the target oligosaccharide in the milk powder sample by hydrophilic interaction chromatography (HILIC). The method has the characteristics of good selectivity, good stability, simple and controllable operation, short time and the like, and is suitable for rapid and high-throughput analysis of milk powder and infant formula milk powder samples.

Technical Field

Breast milk is the gold standard for infant feeding. However, due to the influence of the body of the mother and other factors, some infants cannot be breastfed, and only the second way of feeding infants, namely formula milk powder feeding, is adopted. Among the differences between breast milk and formula feeding, there is a concern about the development of gastrointestinal flora, i.e., the intestinal flora of breast-fed infants is rich in bifidobacteria and lactic acid bacteria. Both of these bacteria are known to have potential benefits on the health of the host. Oligosaccharides are the third largest component in human milk and play a crucial role in the normal growth and development of infants, such as anti-inflammation, anti-infection, immune regulation and maintenance of intestinal flora balance, and the lack of oligosaccharides is likely to be the cause of this difference.

To narrow this difference, GOS and FOS have been added to milk formulas, which however have a large structural difference from naturally occurring human milk oligosaccharides, and during the past year or so, a new pediatric formula based on cow's milk has emerged, which adds the same oligosaccharides as human milk, such as 2' FL and LNnT, to help further narrow this gap. In addition to addressing the need for this difference, there is a need to better understand the predominant oligosaccharide concentrations present in currently marketed infant formulas (highest 3 'SL and 6' SL content) as the basis for new formulations. Therefore, the development of formula milk powder containing human milk oligosaccharides and the corresponding quality control require a suitable method to accurately determine the content of human milk oligosaccharides.

We developed a simple, rapid, high throughput method to achieve simultaneous quantification of 2' FL, LNnT, 3 ' SL and 6 ' SL in milk powder. Since milk powder has a low content of 3 'SL and 6' SL, we used a fluorescence detector to analyze acid oligosaccharides: 3 'SL and 6' SL, uv detector analysis of neutral oligosaccharides: 2' FL and LNnT, which are both difficult to simultaneously quantify human milk oligosaccharides due to content difference.

Disclosure of Invention

The invention relates to 4 human milk oligosaccharides in milk powder based on derivatization and a qualitative and quantitative method thereof. The invention is characterized in that: pretreating a milk powder sample, then derivatizing with a derivatization reagent, and simultaneously analyzing the target human milk oligosaccharide in the milk powder sample by hydrophilic interaction chromatography (HILIC).

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for quantifying target oligosaccharide in milk powder based on derivatization comprises the steps of pretreating a milk powder sample, then derivatizing with a derivatization reagent, and simultaneously analyzing the target oligosaccharide in the milk powder sample through hydrophilic interaction chromatography (HILIC) to obtain content information of the target human milk oligosaccharide in the milk powder. The mobile phase is organic solvent and water or organic solvent and buffer saline solution, and isocratic or gradient elution conditions are used by optimizing chromatographic parameters.

1. The pretreatment steps are as follows: taking a certain milk powder sample, adding water and an organic solvent to dissolve the milk powder sample according to a certain proportion to prepare a sample solution of 1-2000mg/mL, adding 1-5 times of organic solvent by volume, uniformly mixing, standing for 2-48 hours at 0-10 ℃, centrifuging for not less than 5 minutes at 500-10 ℃ for 50000g, taking out supernatant, adding an adsorbing material according to 1-100% of the weight of the milk powder to further remove residual protein and other low-polarity substances, carrying out vortex oscillation for not less than 5 seconds, centrifuging for not less than 5 minutes at 500-10 ℃ for 50000g, collecting supernatant, centrifuging for 1-5 times, and evaporating to dryness to obtain an oligosaccharide protein-removed sample in the milk powder;

2. the derivatization comprises: adding a derivatization reagent, sodium cyanoborohydride, DMSO and a glacial acetic acid solution into the pretreated milk powder sample, reacting for 15min-5h at 25-100 ℃, and standing for 0.5-60 min at-10-10 ℃ after the reaction is finished to terminate the reaction;

the derivatization reagent is anthranilamide, anthranilic acid, 2-aminoacridone and the like;

3. the chromatographic column stationary phase adopted by the analysis method is polar chromatographic packing, comprises silica gel or polar bonded silica gel packing, and has the following structural formula:

wherein SiO is₂Is silica gel, R is polar group, and comprises one or more of amino acid, amide, amino group, carboxyl, glycosyl, zwitter ion and the like;

4. the organic solvent in the mobile phase is one or more of methanol, acetonitrile, ethanol and acetone;

5. the buffer salt type and the concentration and pH value in the mobile phase are as follows:

a) ammonium formate buffer salt, concentration 0-200mM, pH 2.0-7.0;

b) ammonium acetate buffer salt, concentration 0-200mM, pH 2.0-7.0;

c) ammonium bicarbonate buffer salt with concentration of 0-200mM and pH of 6.0-9.0;

6. the mobile phase gradient was optimized as follows: mobile phase water or a buffered saline solution and an organic solvent are used as eluent, and the mixing ratio is 5/95-95/5;

7. the chromatographic operating parameters were optimized as follows: the inner diameter of the chromatographic column is 2.1-10 mm; the flow rate is 0.1-2 BV/min; the column temperature is 15-60 ℃; a detector: a fluorescence detector, an ultraviolet detector and a mass spectrometer detector;

the invention has the following advantages:

1. the selectivity is high. The invention provides a method for separating 4 target oligosaccharides by using a polar chromatographic filler as a stationary phase, which effectively solves the problem of insufficient selectivity of ion exchange chromatography or gel filtration chromatography.

2. The pretreatment method is optimized, and the pollution and interference of impurities in the milk powder are reduced.

3. The derivatization reaction improves the detection sensitivity, and meanwhile, the derivatization reagent flows out in dead time, so that the quantification of the target oligosaccharide is not interfered.

4. The detection is carried out by adopting an ultraviolet detector and a fluorescence detector, so that the detection time is shortened, and the simultaneous quantitative analysis of high-content oligosaccharides (2 ' FL and LNnT) and endogenous low-content oligosaccharides (3 ' SL and 6 ' SL) added in the milk powder is considered.

5. The repeatability is good. The chromatographic column stationary phase used in the invention has good stability and is easy to realize automation.

6. Has wide application range and can be used for analyzing different milk powder and infant formula milk powder.

7. The method has the characteristics of good selectivity, good stability, simple and controllable operation, short time and the like, and is suitable for rapid and high-throughput analysis of milk powder and infant formula milk powder samples.

Drawings

FIG. 1 is the structure of the derivatizing reagent of examples 1, 2 and 3.

FIG. 2 is a chromatogram of the derivatized oligosaccharide standard mixture of example 1 under a fluorescence detector and an ultraviolet detector.

FIG. 3 is a valve switching state diagram in the elution process of example 1.

Detailed Description

Example 1:

(1) pretreatment of milk powder sample

Taking 50mg of milk powder sample (containing oligosaccharide 2' FL 1.5mg and LNnT 0.75mg), adding 0.5mL water to dissolve to obtain 100mg/mL sample solution, adding 1 times volume of anhydrous ethanol, mixing, standing at 4 deg.C for 2 hr, centrifuging at 4 deg.C 40000g for 10 min, taking out supernatant, adding C₁₈20mg of adsorbent further removed residual protein andother low-polarity substances are vortexed and shaken for 30 seconds, then centrifuged for 10 minutes at the temperature of 4 ℃ and 40000g, the supernatant is collected, centrifuged for 1 time and evaporated to dryness, and the oligosaccharide protein-removed sample in the milk powder is obtained;

(2) derivatization of deproteinized oligosaccharide sample in milk powder

Adding 200 mu L of anthranilamide (0.35mol/L) (the specific structure is shown in figure 1) and sodium cyanoborohydride (1mol/L) reaction liquid into the pretreated milk powder sample, wherein the solvent is DMSO: glacial acetic acid (V/V) is 70:30, the reaction is carried out for 2h at the temperature of 60 ℃, and the reaction is stopped after the reaction is finished and the reaction is left for 10 minutes at the temperature of 4 ℃;

(3) drawing of quantitative standard curve

Quality of 2' FL series standard: 1mg, 0.5mg, 0.25mg, 0.125mg, 0.0625mg, 0.03125mg, 0.015625mg, and a series of standards were subjected to derivatization under the conditions and procedures of the method described in "step (2) in example 1", and assayed under the analysis conditions described in "step (4) in example 1", and chromatograms and peak areas were recorded. Linear regression calculation is carried out on the mass X (mg) by using the peak area Y to obtain the linear regression equation of 2' FL, wherein Y is 70000X +52200, and R is²0.9991. The result shows that the mass of the 2' FL is in the mass range of 0.015625-1 mg, and the mass and the peak area form a good linear relation.

Quality of LNnT series standard substance: 0.5mg, 0.25mg, 0.125mg, 0.0625mg, 0.03125mg, 0.015625mg, 0.0078125mg, derivatization of a series of standards under the conditions and procedures of the method "step (2) in example 1", determination under the analytical conditions "step (4) in example 1", and recording of chromatograms and peak areas. Performing linear regression calculation on the mass X (mg) by using the peak area Y to obtain a linear regression equation of LNnT, wherein Y is 30000X-1821.8, and R is²0.9999. The result shows that the mass of LNnT is in the mass range of 0.0078125-0.5 mg, and the mass and the peak area form a good linear relation.

Quality of 3 'SL and 6' SL series standards: 50 μ g, 25mg, 12.5 μ g, 6.25 μ g, 3.125 μ g, 1.5625 μ g, 0.78125 μ g, derivatization of the series of standards under the conditions and procedures of the method described in "step (2) in example 1", and analysis under the conditions described in "step (4) in example 1"Line measurements were taken and chromatograms and peak areas recorded. Linear regression calculation is carried out on the mass X (mu g) by the peak area Y to obtain the linear regression equation of the 3' SL, wherein Y is 29524X +884.67, and R is²The linear regression equation for 0.9997, 6' SL is that Y is 29742X +706.18, R²0.9998. The results show that the mass of 3 'SL and 6' SL is in the mass range of 0.78125-50 mu g, and the mass and the peak area have good linear relation.

(4) Analysis process of oligosaccharide in milk powder

The derivatized milk powder sample was diluted 10-fold with the initial mobile phase (the mobile phase used for column 1 when t is 0). The sample injection amount is 5 mu L, the one-dimensional chromatographic column is a Click TE-GSH column, the inner diameter of the chromatographic column is 2.1mm, and the flow rate is 0.3 mL/min; the two-dimensional chromatographic column uses a stationary phase (amide column) with a silica gel surface bonded with amide groups, the inner diameter of the chromatographic column is 2.1mm, and the flow rate is 0.3 mL/min; the column temperature was 30 ℃ and the UV detector detected 2' FL and LNnT and the fluorescence detector detected 3 ' SL and 6 ' SL. The mobile phase A is acetonitrile, B is water, and C is 100mM ammonium formate. Acetonitrile is a weak elution solvent, and the elution conditions (V/V) are as follows: pump1 (column 1: one-dimensional chromatography column): t 0-15min, 80% → 40% a, linear gradient. Pump2 (column 2: two-dimensional chromatography column): t is 0-4min, 80% a, 20% B, 0% C, isocratic; t-4-4.1 min, 80% a, 20% B, 0% C → 70% a, 20% B, 10% C, linear gradient; t-4.1-15 min, 70% a, 20% B, 10% C → 40% a, 50% B, 10% C, linear gradient.

Description of the system: as shown in fig. 3, under the condition of state 1, the connection state of the six-way valve is 1 → 2, and after the sample of the derived milk powder to be tested is injected, the neutral oligosaccharides (lactose, 2' FL, LNnT) are retained in the one-dimensional chromatographic column, and at this time, the acid oligosaccharides (3 ' SL, 6 ' SL) are discharged into the two-dimensional chromatographic column. At 4 minutes, the valve was switched to the 1 → 6 connection state, then the two chromatography columns were eluted with Pump1 and Pump2, respectively, and the chromatograms and peak areas were recorded, respectively.

(5) As a result: after the oligosaccharide and endogenous oligosaccharide are quantitatively detected in the milk powder sample by the analysis method under the item of step (4) in the example 1, corresponding peak areas are respectively substituted into the linear regression equation corresponding to the step (3), so that the content of the oligosaccharide 2' FL added in the milk powder is 1.47mg/50mg, the content of LNnT is 0.78mg/50mg, and the recovery rates are respectively as follows: 98% and 104%; endogenous oligosaccharide 3 'SL content 24.65. mu.g/50 mg, 6' SL content 12.70. mu.g/50 mg. The method can accurately quantify the added oligosaccharides (2 ' FL and LNnT) and endogenous oligosaccharides (3 ' SL and 6 ' SL) in the milk powder.

Example 2:

(1) pretreatment of milk powder sample

Taking 100mg goat milk powder sample (containing oligosaccharide 2' FL 1.5mg and LNnT 0.75mg), adding 1mL water to dissolve to obtain 100mg/mL sample solution, adding 1 times volume of anhydrous ethanol, mixing, standing at 4 deg.C for 10 min, centrifuging at 4 deg.C 10000g for 20 min, taking out supernatant, adding C₁₈Further removing residual protein and other low-polarity substances by 50mg of an adsorbing material, performing vortex oscillation for 30 seconds, centrifuging at 4 ℃ for 10 minutes at 10000g, collecting supernatant, centrifuging for 3 times, and evaporating to dryness to obtain a sample for removing protein from oligosaccharide in goat milk powder;

(2) derivatization of deproteinized oligosaccharide sample in milk powder

Adding 100 mu L of anthranilic acid (1mol/L) (the specific structure is shown in figure 1) and sodium cyanoborohydride (2mol/L) reaction liquid into the pretreated goat milk powder sample, wherein the solvent is DMSO: glacial acetic acid (V/V) is 70:30, the reaction is carried out for 3h at the temperature of 65 ℃, and the reaction is stopped after the reaction is finished and the reaction product is placed at the temperature of 4 ℃ for 10 min;

(3) drawing of quantitative standard curve

Quality of 2' FL series standard: 1mg, 0.5mg, 0.25mg, 0.125mg, 0.0625mg, 0.03125mg, 0.015625mg, and the series of standards were subjected to derivatization reaction according to the method described in "step (2) in example 1", measured under the analysis conditions described in "step (4) in example 1", and the chromatogram and the peak area were recorded. Linear regression calculation is carried out on the mass X (mg) by using the peak area Y to obtain the linear regression equation of 2' FL, wherein Y is 70000X +52200, and R is²0.9991. The result shows that the mass of the 2' FL is in the mass range of 0.015625-1 mg, and the mass and the peak area form a good linear relation.

Quality of LNnT series standard substance: 0.5mg, 0.25mg, 0.125mg, 0.0625mg, 0.03125mg, 0.015625mg, 0.0078125mg, and mixing the series of standards according to "procedure in example 12) The derivatization reaction was carried out in the same manner as in the above-mentioned "step (4) in example 1", and the chromatogram and the peak area were recorded. Performing linear regression calculation on the mass X (mg) by using the peak area Y to obtain a linear regression equation of LNnT, wherein Y is 30000X-1821.8, and R is²0.9999. The result shows that the mass of LNnT is in the mass range of 0.0078125-0.5 mg, and the mass and the peak area form a good linear relation.

Quality of 3 'SL and 6' SL series standards: 50. mu.g, 25mg, 12.5. mu.g, 6.25. mu.g, 3.125. mu.g, 1.5625. mu.g, 0.78125. mu.g, the series of standards was subjected to derivatization reaction according to the procedure "step (2) in example 1", and measured under the analysis conditions "step (4) in example 1", and the chromatogram and the peak area were recorded. Linear regression calculation is carried out on the mass X (mu g) by the peak area Y to obtain the linear regression equation of the 3' SL, wherein Y is 29524X +884.67, and R is²The linear regression equation for 0.9997, 6' SL is that Y is 29742X +706.18, R²0.9998. The results show that the mass of 3 'SL and 6' SL is in the mass range of 0.78125-50 mu g, and the mass and the peak area have good linear relation.

(4) Analysis process of oligosaccharide in milk powder

The derivatized goat milk powder sample was diluted 10-fold with the initial mobile phase. The sample introduction amount is 5 mu L, a chromatographic column uses a stationary phase (amide column) with a silica gel surface bonded with amide groups, the inner diameter of the chromatographic column is 2.1mm, and the flow rate is 0.2 mL/min; the column temperature was 50 ℃ and the detection was carried out by a fluorescence detector. The mobile phase A is acetonitrile, B is water, and C is 100mM ammonium formate. Acetonitrile is a weak elution solvent, and elution is carried out under a gradient condition (V/V) as follows: t is 0-4min, 80% a, 20% B, 0% C, isocratic; t-4-4.1 min, 80% a, 20% B, 0% C → 70% a, 20% B, 10% C, linear gradient; t-4.1-15 min, 70% a, 20% B, 10% C → 40% a, 50% B, 10% C, linear gradient.

(5) As a result: after the oligosaccharide and endogenous oligosaccharide are quantitatively detected in the milk powder sample by the analysis method under the item of step (4) in the example 1, corresponding peak areas are respectively substituted into the linear regression equation corresponding to the step (3), so that the content of the oligosaccharide 2' FL added in the milk powder is 1.56mg/50mg, the content of LNnT is 0.77mg/50mg, and the recovery rates are respectively as follows: 104% and 103%; endogenous oligosaccharide 3 'SL content 24.96 mu g/50mg, 6' SL content 11.77 mu g/50 mg. The method can accurately quantify the added oligosaccharides (2 ' FL and LNnT) and endogenous oligosaccharides (3 ' SL and 6 ' SL) in the milk powder.

Example 3:

(1) pretreatment of milk powder sample

Taking 50mg of milk powder sample (containing oligosaccharide 2' FL 0.75mg and LNnT 0.375mg), adding 0.5mL water, dissolving to obtain 100mg/mL sample solution, adding 1 times volume of anhydrous ethanol, mixing, standing at 4 deg.C for 2 hr, centrifuging at 4 deg.C 10000g for 10 min, taking out supernatant, adding C₈Further removing residual protein and other low-polarity substances by using 20mg of an adsorbing material, performing vortex oscillation for 30 seconds, then centrifuging for 10 minutes at the temperature of 4 ℃ of 8000g, collecting supernatant, centrifuging for 1 time, and evaporating to dryness to obtain an oligosaccharide protein-removed sample in the milk powder;

(2) derivatization of deproteinized oligosaccharide sample in milk powder

Adding 200 mu L of 2-aminoacridone (0.6mol/L) (the specific structure is shown in figure 1) and cyano sodium borohydride (1mol/L) reaction solution into the pretreated milk powder sample, wherein the solvent is DMSO: reacting glacial acetic acid (70: 30) at 60 ℃ for 2h, and standing at 4 ℃ for 10 minutes to terminate the reaction;

the procedure and the results of plotting the quantitative standard curve were the same as in step (3) of example 1, and the procedure of analyzing oligosaccharides in milk powder was the same as in step (4) of example 1.

(3) As a result: after the oligosaccharide and endogenous oligosaccharide added in the milk powder sample are quantitatively detected by the analysis method under the item of step (4) in the example 1, corresponding peak areas are respectively substituted into the linear regression equation corresponding to the step (3), so that the content of the oligosaccharide added 2' FL in the milk powder is 0.75mg/50mg, the content of LNnT is 0.376mg/50mg, and the recovery rates are respectively as follows: 100% and 100.3%; endogenous oligosaccharide 3 'SL content 24.65. mu.g/50 mg, 6' SL content 12.70. mu.g/50 mg. The method can accurately quantify the added oligosaccharides (2 ' FL and LNnT) and endogenous oligosaccharides (3 ' SL and 6 ' SL) in the milk powder.

Example 4:

(1) pretreatment of milk powder sample

Taking 50mg camel milk powder sample (containing oligosaccharide 2' FL 0.75mg and LNnT 0.375mg), adding 0.5mL water, dissolving to obtain 100mg/mL sample solution, adding 1 times volume of anhydrous ethanol, mixing, standing at 4 deg.C for 2 hr, centrifuging at 4 deg.C 10000g for 10 min, taking out supernatant, adding C₈Further removing residual protein and other low-polarity substances by using 20mg of an adsorbing material, performing vortex oscillation for 30 seconds, centrifuging at 4 ℃ for 10 minutes at 10000g, collecting supernatant, centrifuging for 1 time, and evaporating to dryness to obtain a protein-removed oligosaccharide sample in camel milk powder;

the derivatization process is the same as the step (2) in example 1, and the drawing process and the result of the quantitative standard curve are the same as the step (3) in example 1;

(2) analysis process of oligosaccharide in milk powder

Derivatized camel milk powder samples were diluted 10-fold with the initial mobile phase. The sample introduction amount is 10 mu L, an amino column (a silica gel surface bonded amino group stationary phase) is used as the chromatographic column, the inner diameter of the chromatographic column is 2.1mm, and the flow rate is 0.3 mL/min; the column temperature was 35 ℃ and the detection was carried out by a fluorescence detector. Mobile phase a was acetonitrile, B was water, C was 100mM ammonium formate (PH 3). Acetonitrile is a weak elution solvent, and elution is carried out under the gradient condition that: t is 0-4min, 80% a, 20% B, 0% C, isocratic; t-4-4.1 min, 80% a, 20% B, 0% C → 70% a, 20% B, 10% C, linear gradient; t-4.1-15 min, 70% a, 20% B, 10% C → 40% a, 50% B, 10% C, linear gradient.

(3) As a result: after the oligosaccharide and endogenous oligosaccharide are quantitatively detected in the milk powder sample by the analysis method under the item of step (4) in the example 1, corresponding peak areas are respectively substituted into the linear regression equation corresponding to the step (3), so that the content of the oligosaccharide 2' FL added in the milk powder is 0.74mg/50mg, the content of LNnT is 0.374mg/50mg, and the recovery rates are respectively as follows: 99% and 100%; endogenous oligosaccharide 3 'SL content is 19.37 mug/50 mg, 6' SL content is 6.64 mug/50 mg. The method can accurately quantify the added oligosaccharides (2 ' FL and LNnT) and endogenous oligosaccharides (3 ' SL and 6 ' SL) in the milk powder.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.