CN102175800A - A method for determining the content of 1,3-dioleic acid-2-palmitic acid triglyceride in dairy products - Google Patents

Abstract

The invention discloses a method for measuring the content of 1,3-dioleic acid-2-palmitic triglyceride in dairy products. The method comprises the following steps: (1) extracting fat in dairy products according to a conventional method; (2) ) dissolving the fat extracted in step (1) in dichloromethane, and then measuring the content of 1,3-dioleic acid-2-palmitic acid triglyceride by high performance liquid chromatography. The method of the invention solves the difficulty that the triglyceride cannot be directly quantified, and has the advantages of high accuracy, less influence by environmental changes, simple operation method and the like.

Description

A method for determining the content of 1,3-dioleic acid-2-palmitic acid triglyceride in dairy products

technical field

The invention belongs to the technical field of analytical chemistry, in particular to a method for measuring the content of 1,3-dioleic acid-2-palmitic acid triglyceride in dairy products.

Background technique

1,3-Dioleic acid-2-palmitic acid triglyceride (OPO) is a new resource food added by the Ministry of Health in 2008. It is a triglyceride similar to breast milk fat. About 70% of palmitic acid in breast milk fat is linked to the sn-2 position of triglycerides, while the sn-1 and 3 positions are mainly unsaturated fatty acids. Palmitic acid is an important energy-producing fatty acid in the human body. Its position on triglycerides has a great influence on its digestion and absorption. Palmitic acid on the sn-2 position can be absorbed in the form of sn-2 monoglyceride. And sn-1, palmitic acid on the 3rd position is easy to form insoluble salt with minerals (calcium, magnesium, etc.) and lose, and also cause the loss of minerals and energy. Therefore, 1,3-dioleate-2-palmitic acid triglyceride, as a new type of food additive, has the functions of promoting the body's energy absorption, promoting the absorption of bone minerals such as calcium and magnesium, and alleviating constipation in infants and young children. At present, the research on 1,3-dioleic acid-2-palmitic acid triglyceride has gradually shifted from the laboratory stage to industrial production and application abroad, and it is mainly used in formula food for infants and young children.

At present, the detection method of fat in infant milk powder used in China is mainly to measure the content of various free fatty acids in milk powder. This method is mainly to extract the fat through pretreatment, then esterify the fat in the sample through saponification reaction, and finally quantify each fatty acid methyl ester by gas chromatography external standard method. Therefore, this method can only measure the amount of fatty acid and cannot be used for the determination of triglycerides.

The current method for detecting OPO is mainly to measure the proportion of 2-position palmitic acid in the total palmitic acid. The method is to use pancreatic lipase to remove the sn-1 and 3-position fatty acids of triglycerides, and then use thin-layer chromatography to separate sn-2 monoglycerides, which are derivatized into methyl esters and analyzed by GC, and the spectrum area is normalized. Get the ratio of palmitic acid at the sn-2 position. The total sample was derivatized to form fatty acid methyl esters, and the GC profile gave the proportion of total palmitic acid. Use the formula:

The ratio of sn-2 palmitic acid to the total palmitic acid can be obtained, but this method cannot accurately determine the amount of OPO added.

Therefore, it is necessary to find a method to directly measure the content of OPO and other triglycerides in dairy products.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for directly measuring the content of 1,3-dioleic acid-2-palmitic triglyceride in dairy products.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A method for measuring 1,3-dioleic acid-2-palmitic acid triglyceride content in dairy products, the method comprises the steps of:

(1) Extract the fat in dairy products according to conventional methods;

(2) dissolving the fat extracted in step (1) in dichloromethane, and then measuring the content of 1,3-dioleic acid-2-palmitic triglyceride by high performance liquid chromatography;

Wherein, the high performance liquid chromatography detection condition is:

Chromatographic column: normal phase C18 chromatographic column, the stationary phase is octadecylsilane bonded silica gel adsorption phase;

Mobile phase: Phase A is dichloromethane, phase B is acetone or acetonitrile; at time t ₀ , X is 10-25%; from time t ₀ to time t ₁ , X increases linearly until it reaches 26-37 at time t ₁ %; from time _t1 to time _t2 , X continues to increase linearly until time _t2 reaches 38-60%; from time _t2 to time _t3 , X decreases linearly until time _t3 reaches 10-25% ; Among them, t ₀ , t ₁ , t ₂ , t ₃ are the moments in the total liquid phase detection time, t ₃ is the time when the sample stops detection, t ₀ <t ₁ <t ₂ <t ₃ , and the value range is t ₀ = 0min, 10min≤t ₁ ≤20min, 21min≤t ₂ ≤30min, 29min≤t ₃ ≤35min; X is the volume percentage of the volume of phase A and the total volume of the two phases A and B; the schematic diagram of the above gradient elution is shown in Figure 4 , but the method of the present invention is not limited to the specific elution mode shown in FIG. 4 . Ordinary HPLC detectors can set the elution program to complete the above gradient elution process.

Mobile phase flow rate: 0.3-1.3mL/min, preferably 0.8mL/min;

Detector: evaporative light scattering detector (ELSD) or differential refractive index detector (RI);

Chromatographic column temperature: 18-30°C, preferably 21°C;

Injection volume: 10-20 μk, preferably 20 μL.

Wherein, the dairy product is colostrum, infant food, milk powder, reconstituted milk or milk-containing beverage.

In step (1), the fat in dairy products can be extracted according to conventional methods, preferably the fat is extracted according to the following steps, specifically refer to GB5413.27-2010:

①Pretreatment: If the dairy product is a solid sample containing starch, add an appropriate amount of amylase to remove the starch, and then add hot water to dissolve; if the dairy product is a solid sample without starch, directly add hot water to dissolve; if When the dairy product is a liquid sample, no pretreatment is required;

②Process casein calcium salt: add ammonia water to the solution obtained in step ①, shake evenly, and bathe in hot water for 10-30 minutes;

③Extraction: Add ethanol to the solution obtained in step ② and mix evenly, continue to add diethyl ether to mix evenly, then continue to add petroleum ether to mix evenly, let stand for 10-60min, take the organic layer; repeat adding the above three reagents 1-5 times, Stand still, take the organic layer, combine the organic layers, and evaporate the extract to nearly dryness with a rotary evaporator at 20-70°C, and the viscous liquid obtained is the fat in dairy products.

Wherein, the specification of the normal phase C18 chromatographic column is 4.6*250 mm, 5 μm.

Wherein, after the fat extracted in step (1) is dissolved in dichloromethane, the sample needs to be filtered through an organic membrane and ultrasonically treated before sample injection. The pore diameter of the organic membrane is ≤0.45 μm, preferably 0.25 μm.

Wherein, when the detector is an evaporative light scattering detector, the drift tube temperature is 40-70°C, preferably 50°C; the sensitivity is 1, 2, 4, 8 or 16, preferably 1; the nitrogen flow rate is 1.2-1.8L /min, preferably 1.5L/min.

In the present invention, the content of 1,3-dioleic acid-2-palmitic acid can be determined by quantitative analysis methods commonly used in the art, preferably using external standard method or internal standard method to calculate the peak area, thereby determining 1,3-dioleic acid Acid-2-palmitic acid triglyceride content.

The purity of the ammoniacal liquor, ethanol, ether and petroleum ether described in the present invention can be conventionally used in the art, preferably analytical pure; dichloromethane, acetone and acetonitrile are preferably chromatographically pure. The reagents and raw materials used in the present invention are all commercially available.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

1. The present invention combines the conventional extraction method of fat in dairy products with high-performance liquid chromatography to solve the quantitative analysis problem of triglycerides in dairy products. Compared with the fat detection method used in current dairy products, this method can The different triglycerides are separated and quantified by an external standard method, thus realizing the accurate detection of triglycerides.

2. The chromatographic column is used to separate and detect the content of OPO in the sample. Compared with the method of detecting the proportion of 2-position palmitic acid in the total palmitic acid by gas chromatography, the added amount of OPO can be directly measured. In addition, the chromatographic column can also realize the separation between samples by adjusting the ratio of the mobile phase, so that the baseline separation between the samples can be well achieved, so as to achieve the purpose of accurate quantitative analysis.

3. The present invention uses the most commonly used C18 chromatographic column in high performance liquid chromatography, and the detection cost is relatively low.

Description of drawings

Fig. 1 is the HPLC curve chart of 1,3-dioleic acid-2-palmitic acid triglyceride standard substance and its isomers.

Fig. 2 is a standard curve diagram for determining the mass concentration of 1,3-dioleic acid-2-palmitic acid triglyceride by HPLC.

Fig. 3 is the HPLC graph that the 1,3-dioleic acid-2-palmitic acid triglyceride of milk powder detects in embodiment 1, wherein, 1, trioleic acid triglyceride (OOO) and its polarity are weaker triglycerides; 2, 1,3-dioleic acid-2-palmitic acid triglyceride (OPO); 3, 1,2-dioleic acid-3-palmitic acid triglyceride (OOP); 4, 1 , 2-dipalmitic acid-3-oleic acid triglyceride (PPO); 5, 1,3-dipalmitic acid-2-oleic acid triglyceride (POP); 6, tripalmitic acid triglyceride (PPP) And triglycerides, which are more polar than it.

Fig. 4 is a schematic diagram of gradient elution in the high performance liquid phase detection method of the present invention.

Fig. 5 is the HPLC graph that 1,3-dioleic acid-2-palmitic acid triglyceride detects in the infant milk powder in embodiment 3, wherein, 1, trioleic acid triglyceride (OOO) and its polarity Weaker triglycerides; 2, 1,3-Dioleo-2-palmitate triglyceride (OPO); 3, 1,2-Dioleo-3-palmitate triglyceride (OOP); 4 , 1,2-dipalmitic acid-3-oleic acid triglyceride (PPO); 5,1,3-dipalmitic acid-2-oleic acid triglyceride (POP); 6, tripalmitic acid triglyceride ( PPP) and triglycerides that are more polar than it.

Detailed ways

The present invention can be better understood from the following examples. However, those skilled in the art can easily understand that the content described in the embodiments is only for illustrating the present invention, and should not and will not limit the present invention described in the claims.

Example 1: Determination of OPO content in infant milk powder.

Weigh 1.0g (accurate to 0.1mg) of infant milk powder sample (French Synbiotics) into a liposuction tube, add 10mL of water at 65±1°C to dissolve the sample, and shake to completely disperse the sample. Add 2mL of ammonia water to the sample, place it in a water bath at 65±1°C for 15min, take it out and shake it gently, and cool to room temperature. Add 10 mL of ethanol to the prepared sample and mix well. Add 25mL of diethyl ether, stopper and shake for 1min, add 25mL of petroleum ether, stopper and shake for 1min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. Then add 25mL diethyl ether and 25mL petroleum ether, stopper and shake for 1min, let stand, separate layers, transfer the organic layer into a ground-necked flask, and repeat the extraction operation once more. Combine the organic layers in a ground flask, and concentrate to dryness at 55°C with a rotary evaporator. dichloromethane was diluted to 250mL to obtain a fat solution.

The fat solution obtained above was filtered with a 0.25 μm organic membrane needle filter into a sample bottle, and after ultrasonic treatment, it was determined by high performance liquid chromatography.

HPLC detection conditions are as follows:

High performance liquid chromatography: Agilent1200 type;

Chromatographic column: Sepax HP-C18 (250*4.6mm, 5μm, USA);

Mobile phase: Phase A is dichloromethane, phase B is acetonitrile; at time t ₀ , X is 20%; from time t ₀ to time t ₁ , X increases linearly until time t ₁ reaches 35%; from time t ₁ At time t ₂ , X continues to increase linearly until it reaches 55% at time t ₂ ; from time t ₂ to time t ₃ , X decreases linearly until it reaches 20% at time t ₃ ; t ₀ =0min, t ₁ =17min , t ₂ =27min, t ₃ =35min, X is the volume percentage of the volume of phase A and the total volume of the two phases A and B;

Flow rate: 0.8mL/min;

Detector: evaporative light scattering detector (ELSD); ELSD drift tube temperature: 50°C, nitrogen flow rate: 1.5L/min, sensitivity: 1;

Chromatographic column temperature: 21°C;

Injection volume: 20 μL.

Drawing of standard curve (determination of substance content by external standard method):

Accurately weighed 1,3-dioleic acid-2-palmitic acid triglyceride (OPO) standard product (Sigma, Switzerland) to make the concentration of OPO solution was 1 ~ 300 μg/mL; The standard curve of the peak area in ELSD is drawn as follows: lgY=1.4537+1.1923lgX (R ² =0.9990, Figure 2).

Determination of the separation degree of OPO and its isomer 1,2-dioleic acid-3-palmitic acid triglyceride (OOP):

Weighed OPO and OOP standard products to make a mixed solution with a concentration of 50 μg/mL, and detected them by high performance liquid chromatography to obtain their separation spectrum (Figure 1). The resolution was R=3.18>1.5, that is, complete separation.

Determination of detection limit and quantification limit of OPO and its isomer 1,2-dioleic acid-3-palmitic acid triglyceride (OOP):

Weigh the OPO standard product to make a standard solution, the concentration is 5 μg/mL, dilute step by step, and detect by high performance liquid chromatography, the minimum detection limit (signal-to-noise ratio S/N=3) of OPO is 0.001 μg, and the minimum quantification limit (signal The noise ratio (S/N=10) was 0.05 μg. Precision experiment:

Carry out 6 simultaneous experiments on the same infant milk powder sample by the above method. The HPLC measurement of Experiment 1 is shown in Figure 3. It can be seen that the experiment can separate OPO from OOP and other triglyceride baselines. Compared with the standard curve, the results are as follows Table 1.

Table 1 Determination of the OPO content of the same infant milk powder

The relative standard deviation RSD calculated from the results in Table 1 is 2.20%.

It can be obtained from the above that the relative standard deviation is 2.20%, which indicates that the reproducibility is good.

Through the above method, different amounts of OPO standard products were added to infant milk powder, compared with the background, and compared with the standard curve, the results are shown in Table 2:

Table 2 Determination of recovery rate

It can be obtained from Table 2 that the recovery rate of the experiment is between 78% and 92%, which shows that the method has high accuracy in determining OPO content.

Embodiment 2: the content determination of OPO in the rice flour.

Weigh 1.0g of rice flour (accurate to 0.1mg) into a liposuction tube, add 0.1g of peak-type amylase, add 10mL of 50°C water, cover the bottle, place in a 40°C oven for 30min, and cool to room temperature. Add 10 mL of ethanol to the prepared sample, mix well, add 20 mL of diethyl ether, stopper and shake for 1 min, add 20 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. Then add 5 mL of ethanol, 20 mL of diethyl ether and 20 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, transfer the organic layer into a ground-necked flask, and repeat the extraction operation once. Combine the organic layers in a ground flask, and concentrate to dryness at 50°C with a rotary evaporator. dichloromethane was diluted to 200mL to obtain a fat solution.

The fat solution obtained above was filtered with a 0.25 μm organic membrane needle filter into a sample bottle, and then subjected to high-performance liquid chromatography for determination after ultrasonication.

HPLC detection conditions are as follows:

High performance liquid chromatography: waters 1525 type;

Chromatographic column: Chrom-matrix bio-technology innovation explorer C18HPLCcolumn (250*4.6mm, 5μm, USA);

Mobile phase: Phase A is dichloromethane, phase B is acetone; at time _t0 , X is 15%; from time _t0 to time _t1 , X increases linearly until time X reaches 30% at time _t1 ; from time _t1 At time t ₂ , X continues to increase linearly until it reaches 45% at time t ₂ ; from time t ₂ to time t ₃ , X decreases linearly until it reaches 15% at time t ₃ ; t ₀ =0min, t ₁ =13min , t ₂ =23min, t ₃ =29min, X is the volume percentage of the volume of phase A and the total volume of phases A and B;

Flow rate: 1mL/min;

Detector: evaporative light scattering detector (ELSD); ELSD drift tube temperature: 70°C, nitrogen flow rate: 1.7L/min, sensitivity: 1;

Chromatographic column temperature: 23°C;

Injection volume: 20 μL.

Precision experiment:

Through the above method, 6 simultaneous experiments were carried out on the same rice noodle sample, and the experimental results were compared with the standard curve. The calculation results are shown in Table 3:

Table 3 Determination of OPO content of the same rice flour

The relative standard deviation calculated from the results in Table 3 is RSD=0.84%.

It can be obtained from the above that the relative standard deviation is 0.84%, which indicates that the reproducibility is good.

Example 3: Verification of the recovery rate of OPO in infant milk powder.

Weigh 1.0g (accurate to 0.1mg) of the two infant milk powder samples into liposuction tubes, add 1-100mg of OPO standard, 10mL of 65±1℃ water to dissolve the samples, and shake to completely disperse the samples . Add 2mL of ammonia water to the sample, place it in a water bath at 65±1°C for 15min, take it out and shake it gently, and cool to room temperature. Add 10 mL of ethanol to the prepared sample, mix well, add 30 mL of diethyl ether, stopper and shake for 1 min, add 30 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. Then add 30mL diethyl ether and 30mL petroleum ether, stopper and shake for 1min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. The combined extracts were placed in a ground-necked flask, and concentrated to dryness at 60°C by a rotary evaporator. Dichloromethane was diluted to 250ml to obtain a fat solution.

Filter the fat solution obtained above with a needle filter of 0.45 μm organic filter membrane into a sample bottle, and shake it up for determination by high performance liquid chromatography.

HPLC detection conditions are as follows:

High performance liquid chromatography: Agilent1200 type;

Chromatographic column: Agilent ZORBAX Eclipse XDB-C18 (250*4.6mm, 5μm, USA);

Mobile phase: Phase A is dichloromethane, phase B is acetonitrile; at time t ₀ , X is 18%; from time t ₀ to time t ₁ , X increases linearly until time t ₁ reaches 33%; from time t ₁ At time t ₂ , X continues to increase linearly until it reaches 50% at time t ₂ ; from time t ₂ to time t ₃ , X decreases linearly until it reaches 18% at time t ₃ ; t ₀ =0min, t ₁ =19min , t ₂ =30min, t ₃ =37min, X is the volume percentage of the volume of phase A and the total volume of the two phases A and B;

Flow rate: 0.7mL/min;

Detector: differential refraction detector;

Chromatographic column temperature: 19°C;

Injection volume: 20 μL.

By the above method, different amounts of OPO standard products were added to infant milk powder, compared with the background of infant milk powder, and compared with the standard curve, the results are shown in Table 4, and the HPLC detection spectrum is shown in Figure 5.

Table 4 The recovery rate of standard addition of OPO in infant milk powder

It can be obtained from Table 4 that the recovery rate of the experiment is between 75% and 95%, which shows that the method has high accuracy in determining OPO content.

Example 4: Validation of recovery of OPO in colostrum powder.

Weigh 0.4g of colostrum-based powder (accurate to 0.1mg) into a liposuction tube, add 1-100mg of OPO standard product, then add 10mL of water at 65±1°C to dissolve the sample, and shake to completely disperse the sample. Add 2mL of ammonia water to the sample, place it in a water bath at 65±1°C for 15min, take it out and shake it gently, and cool to room temperature. Add 5 mL of ethanol to the prepared sample and mix well. Add 15 mL of ether, stopper and shake for 1 min. Add 15 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. Then add 5 mL of ethanol, 25 mL of diethyl ether and 25 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, transfer the organic layer into a ground-necked flask, and repeat the extraction operation once. The combined extracts were placed in a ground-necked flask, and concentrated to dryness at 65°C by a rotary evaporator. Dichloromethane was diluted to 200ml to obtain a fat solution.

Filter the fat solution obtained above with a needle filter of 0.45 μm organic filter membrane into a sample bottle, and shake it up for determination by high performance liquid chromatography.

HPLC detection conditions are as follows:

High performance liquid chromatography: Agilent1200 type

Chromatographic column: Chrom-matrix bio-technology innovation explorer C18HPLCcolumn (250*4.6mm, 5μm, USA);

Mobile phase: Phase A is dichloromethane, phase B is acetone; at time t ₀ , X is 19%; from time t ₀ to time t ₁ , X increases linearly until time t ₁ reaches 32%; from time t ₁ At time t ₂ , X continues to increase linearly until it reaches 48% at time t ₂ ; from time t ₂ to time t ₃ , X decreases linearly until it reaches 19% at time t ₃ ; t ₀ =0min, t ₁ =16min , t ₂ =25min, t ₃ =31min, X is the volume percentage of the volume of phase A and the total volume of the two phases A and B;

Flow rate: 0.9mL/min;

Detector: evaporative light scattering detector (ELSD); ELSD drift tube temperature: 65°C, nitrogen flow rate: 1.6L/min, sensitivity: 1;

Chromatographic column temperature: 20°C;

Injection volume: 10 μL.

By the above method, different amounts of OPO standard were added to colostrum powder, compared with the background of colostrum powder, and compared with the standard curve, the results are shown in Table 5:

Table 5 The recovery rate of standard addition of OPO in infant milk powder

It can be seen from Table 5 that the recovery rate of the experiment in the colostrum powder (blank) is between 76% and 96%, which shows that the accuracy of the method for determining the OPO content is very high.

Embodiment 5: the content determination of OPO in milk powder

Weigh 1.0g (accurate to 0.1mg) of infant milk powder sample (French Synbiotics) into a liposuction tube, add 10mL of water at 65±1°C to dissolve the sample, and shake to completely disperse the sample. Add 2mL of ammonia water to the sample, place it in a water bath at 65±1°C for 15min, take it out and shake it gently, and cool to room temperature. Add 10 mL of ethanol to the prepared sample and mix well. Add 25 mL of ether, stopper and shake for 1 min. Add 25 mL of petroleum ether, stopper and shake for 1 min, let stand, separate layers, and transfer the organic layer into a ground-necked flask. Then add 25mL diethyl ether and 25mL petroleum ether, stopper and shake for 1min, let stand, separate layers, transfer the organic layer into a ground-necked flask, and repeat the operation once more. The combined extracts were placed in a ground-necked flask, and concentrated to dryness at 55°C with a rotary evaporator. Dichloromethane was diluted to 250ml to obtain a fat solution.

Filter the fat solution obtained above with a 0.25 μm organic membrane needle filter into a sample bottle, shake it up and use it for high performance liquid chromatography determination.

HPLC detection conditions are as follows:

High performance liquid chromatography: waters 1525 type;

Chromatographic column: Agilent ZORBAX Eclipse XDB-C18 liquid chromatography column (5μm, 4.6mm*250mm,);

Mobile phase: Phase A is dichloromethane, phase B is acetonitrile; at time _t0 , X is 22%; from time _t0 to time _t1 , X increases linearly until time X reaches 30% at time _t1 ; from time _t1 At time _t2 , X continues to increase linearly until it reaches 47% at time _{t2; from time t2 to} time _t3 , X decreases linearly until it reaches 20% at time _t3 ; _t0 = 0min, _t1 = 17min , t ₂ =26min, t ₃ =34min, X is the volume percentage of the volume of phase A and the total volume of the two phases A and B;

Flow rate: 0.9mL/min;

Detector: evaporative light scattering detector (ELSD); ELSD drift tube temperature: 50°C, nitrogen flow rate: 1.5L/min, sensitivity: 1;

Chromatographic column temperature: 19°C;

Injection volume: 20 μL.

The infant milk powder sample was analyzed by the above method, and OPO was baseline separated from other triglycerides. As a result, the OPO content in the sample was 29.45 mg/g.

Claims (5)

1. a method for measuring 1,3-dioleic acid-2-palmitic acid triglyceride content in dairy products, is characterized in that the method comprises the steps: (1) Extract the fat in dairy products according to conventional methods; (2) dissolving the fat extracted in step (1) in dichloromethane, and then measuring the content of 1,3-dioleic acid-2-palmitic triglyceride by high performance liquid chromatography; Wherein, the high performance liquid chromatography detection condition is: Chromatographic column: normal phase C18 chromatographic column; Mobile phase: Phase A is dichloromethane, phase B is acetone or acetonitrile; at time t ₀ , X is 10-25%; from time t ₀ to time t ₁ , X increases linearly until it reaches 26-37 at time t ₁ %; from time _t1 to time _t2 , X continues to increase linearly until time _t2 reaches 38-60%; from time _t2 to time _t3 , X decreases linearly until time _t3 reaches 10-25% ; Among them, t ₀ , t ₁ , t ₂ , t ₃ are the moments in the total liquid phase detection time, t ₃ is the time when the sample stops detection, t ₀ <t ₁ <t ₂ <t ₃ , and the value range is t ₀ =0min, 10min≤t ₁ ≤20min, 21min≤t ₂ ≤30min, 29min≤t ₃ ≤35min; X is the volume percentage of the volume of phase A to the total volume of phase A and phase B; Detector: evaporative light scattering detector or differential refractive index detector; Chromatographic column temperature: 18～30℃; Injection volume: 10-20 μL. 2. the method for measuring 1,3-dioleic acid-2-palmitic acid triglyceride content in the dairy product according to claim 1 is characterized in that described dairy product is colostrum, baby food, milk powder, Reconstituted milk or milk-containing beverages. 3. The method for determining the content of 1,3-dioleic acid-2-palmitic triglyceride in dairy products according to claim 1, characterized in that the specification of the normal phase C18 chromatographic column is 4.6*250mm, 5 μm . 4. the method for measuring 1,3-dioleic acid-2-palmitic triglyceride content in dairy products according to claim 1 is characterized in that the fat that step (1) extracts is dissolved in dichloromethane Afterwards, the samples were filtered through an organic membrane and sonicated before injection. 5. the method for measuring 1,3-dioleic acid-2-palmitic triglyceride content in dairy products according to claim 1, is characterized in that when described detector is evaporative light scattering detector, drift tube The temperature is 40-70°C, the sensitivity is 1, 2, 4, 8 or 16, and the nitrogen flow rate is 1.2-1.8L/min.

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