CN103424364B - A kind of assay method of L-methionine product content - Google Patents

Abstract

The present invention relates to a kind of assay method of L-methionine product content.It has optical activity according to METHIONINE, and be directly proportional to solution concentration according to optical activity within the scope of finite concentration, sample solution is mixed with METHIONINE product sample, survey its optical activity size, compare with the optical activity of the reference substance solution of the known quality percentage composition of corresponding concentration under the same conditions, and then obtain the content of METHIONINE in product sample.The method is simple, and quick and precisely, and instrument is cheap, with low cost, has obvious advantage, be applicable to the assay of METHIONINE product compared with additive method.

Description

A kind of assay method of L-methionine product content

Technical field

The present invention relates to the assay of METHIONINE product, particularly relate to a kind of assay method of L-methionine product content.

Background technology

METHIONINE, another name L-2-amino-4-methylmercapto butyric acid, white solid, fusing point 281 DEG C, water-soluble, diluted acid and diluted alkaline, be insoluble to ethanol, ether etc.METHIONINE is the amino acid whose one of constitutive protein matter, is mammiferous essential amino acid and ketogenic amino acid.It has detoxication, as Branchamin and nutritional supplement, can maintain body growth and grow and nitrogen balance.

Column front derivation high performance liquid chromatography is had at present to amino acid whose assay, amino-acid analyzer directly measures, formaldehyde method etc., and for the assay of METHIONINE, Chinese Pharmacopoeia adopts non-aqueous titration, with formic acid and glacial acetic acid for solvent, with the titration of perchloric acid standard titration solution, current potential directing terminal is carried out.But all there is certain technical matters in these assay methods: adopt column front derivation high performance liquid chromatography and amino-acid analyzer directly to measure, its result is accurate, but instrument is expensive, and cost is higher; Adopt Formaldehyde Absorption Method for Determination of Low accuracy poor; Employing non-aqueous titration measures, and all alkaline matters (comprising the alkali of Proton opinion) together can be measured, and sample requirement is anhydrous.

Summary of the invention

The object of the present invention is to provide a kind of assay method of L-methionine product content, this assay method is simple, quick and precisely, and with low cost.

The object of the present invention is achieved like this:

An assay method for L-methionine product content, the mass percentage of the METHIONINE contained in described METHIONINE product is at least 90%, in dry product; It is characterized in that, it is take concentration as the hydrochloric acid solution of 5mol/L is solvent, to accurately take a certain amount of described METHIONINE product as sample to be tested, the concentration be mixed with containing METHIONINE is the sample to be tested solution of 0.20 ~ 3.0g/100mL, carry out measuring according to following steps: the METHIONINE reference substance accurately taking a certain amount of known quality percentage composition, be the reference substance solution of 0.20 ~ 3.0g/100mL by the described solvent concentration be mixed with containing METHIONINE, detect in polarimeter, record the optical activity of reference substance solution; Again described sample to be tested solution is detected in polarimeter, record the optical activity of this sample to be tested solution; Finally calculate the content of METHIONINE in sample to be tested.

Said determination method is based on METHIONINE and has optical activity, its optical activity is directly proportional to solution concentration, sample solution is mixed with METHIONINE product sample, its optical activity size is surveyed with polarimeter, compare with the optical activity of the reference substance solution of the known quality percentage composition of corresponding concentration under the same conditions, and then obtain the content of METHIONINE in product sample.

Said determination process is carried out in the scope that temperature is 20 ~ 30 DEG C.To make polarization tube expansion, length increase because temperature raises, and cause the density of solution to be measured to reduce, and temperature variation may make the molecule of test substance occur to associate or dissociation, and optical activity is changed.Found by test: control within the scope of 20 ~ 30 DEG C by the temperature of the process of mensuration, the angle-of-rotation measuring result of its solution to be measured is stablized, without significant change.

Saying specifically, the assay method of a kind of L-methionine product content disclosed by the invention, is characterized in that, it specifically carries out according to following steps:

1. take the METHIONINE reference substance 2.0g that known quality percentage composition is at least 98.5%, claim accurate to 0.0001g, add 5mol/L dissolve with hydrochloric acid solution, be diluted to 100mL, shake up, product solution in contrast, injects afterwards and measures pipe, be placed in polarimeter and detect reading, obtain the optical activity of reference substance solution, wherein, the precision of polarimeter is 0.001 °, and optically-active pipe range is 2dm, condition determination is the D line (589.3nm) of sodium spectrum, and temperature is 20 ~ 30 DEG C;

2. the product that the appropriate mass percentage containing METHIONINE is at least 90% is got, in dry product, constant weight is dried at 105 DEG C, take 2.0g wherein as sample to be tested, claim accurate to 0.0001g, afterwards according to the optical activity of the 1. described condition of step and time-and-motion study gained sample to be tested solution;

3. result calculates

The content of METHIONINE in METHIONINE product is calculated, in dry product according to following formula:

$w(\%)=\frac{\mathrm{\α}\×m_r\×p_r}{{\mathrm{\α}}_r\×m}\×100$

In formula, α is the optical activity of sample to be tested solution;

α _rfor the optical activity of reference substance solution;

P _rfor the mass percentage of METHIONINE in reference substance, numerical value represents with %;

M _rfor the quality of reference substance taken, unit is g;

M is the quality of the sample to be tested taken, and unit is g.

The present invention has following beneficial effect:

The invention discloses a kind of short-cut method adopting Optical Rotation to measure L-methionine product content, the relative standard deviation RSD=0.12% (n=6) of its measurement result, recovery of standard addition 98.64%.The method is simple, and quick and precisely, and instrument is cheap, with low cost, has obvious advantage, be applicable to the assay of METHIONINE product compared with additive method.

Accompanying drawing explanation

Fig. 1 be in the embodiment of the present invention 1 with the concentration of METHIONINE for horizontal ordinate x-axis, the optical activity of its correspondence is the mapping of ordinate y-axis, and the optical activity of the METHIONINE obtained is with the curve map of its concentration change.

Embodiment

Below by embodiment, the present invention is specifically described; but following examples are only for being further detailed the present invention; can not be interpreted as the restriction to its protection domain, the person skilled in the art in this field can make some nonessential improvement and adjustment according to foregoing to the present invention.

Embodiment 1

An assay method for L-methionine product content, it specifically carries out according to following steps:

1. the METHIONINE reference substance 2.1154g that known quality percentage composition is 99.0% is taken, in 100mL measuring bottle, add 5mol/L dissolve with hydrochloric acid solution, be diluted to 100mL, shake up, product solution in contrast, and rinse mensuration pipe for several times by this reference substance solution, then this reference substance solution is slowly injected mensuration pipe, be placed in polarimeter and detect reading, the optical activity obtaining reference substance solution is 0.995 °; Wherein, the precision of polarimeter is 0.001 °, and optically-active pipe range is 2dm, and condition determination is the D line (589.3nm) of sodium spectrum, and temperature is 23 DEG C;

2. the product that the appropriate mass percentage containing METHIONINE is at least 90% is got, in dry product, constant weight is dried at 105 DEG C, take 2.0280g wherein as sample to be tested, afterwards according to the optical activity of the 1. described condition of step and time-and-motion study gained sample to be tested solution, its optical activity is 0.935 °;

3. result calculates

Following formula calculates the content of METHIONINE in METHIONINE product, in dry product:

$w(\%)=\frac{\mathrm{\α}\×m_r\×p_r}{{\mathrm{\α}}_r\×m}\×100$

$=\frac{0.935\×2.1154\×99.0\%}{0.995\×2.0280}\×100$

$=97.04$

In formula, α is the optical activity of sample to be tested solution;

α _rfor the optical activity of reference substance solution;

P _rfor the mass percentage of METHIONINE in reference substance, numerical value represents with %;

M _rfor the quality of reference substance taken, unit is g;

M is the quality of the sample to be tested taken, and unit is g.

Optical activity about METHIONINE is investigated with the linear relationship of its concentration change in this example:

Accurately take METHIONINE reference substance 0.2037g, 0.5292g, 1.0473g, 2.1154g, 3.0428g that known quality percentage composition is 99.0% respectively, be placed in 100mL volumetric flask respectively, add 5mol/ dissolve with hydrochloric acid solution and be diluted to scale, namely obtaining containing METHIONINE concentration is the different reference substance solution of 0.2017g/100mL, 0.5239g/100mL, 1.0368g/100mL, 2.0942g/100mL, 3.0124g/100mL five parts, the condition 1. described by step and operation measure its optical activity respectively, and result data sees the following form 1:

Table 1

According to upper table 1, with the concentration of METHIONINE for horizontal ordinate x-axis, the optical activity of reference substance solution is the mapping of ordinate y-axis, obtains the curve map of optical activity with its concentration change of METHIONINE as shown in the accompanying drawings 1.

Obtain through least square fitting: equation of linear regression y=0.477x, R ²=1 (n=5).Illustrate that the concentration of METHIONINE is in 0.2017 ~ 3.0124 (g/100mL) scope, its optical activity and concentration have good linear relationship.This method determines detected object after diluted acid dissolves and is diluted to the solution of 100mL according to the content of the sampling amount of detected object and METHIONINE wherein, and the concentration of METHIONINE contained in its gained solution is in the central authorities of the range of linearity.

Embodiment 2

A kind of assay method of L-methionine product content, the selecting of its reference substance and reference substance solution, measure identical with embodiment 1, other step is specifically carried out according to the operation steps described in embodiment 1, and in this example, the quality of its sample to be tested is 2.0075g, the optical activity of sample to be tested solution is 0.926 °, and the content that result calculates METHIONINE in sample to be tested is 97.09%.

Embodiment 3

A kind of assay method of L-methionine product content, the selecting of its reference substance and reference substance solution, measure identical with embodiment 1, other step is specifically carried out according to the operation steps described in embodiment 1, and in this example, the quality of its sample to be tested is 2.0351g, the optical activity of sample to be tested solution is 0.948 °, and the content that result calculates METHIONINE in sample to be tested is 98.05%.

Embodiment 4 (reappearance experiment)

A kind of assay method of L-methionine product content, the selecting of its reference substance and reference substance solution, measure identical with embodiment 1, and employing is at least the product of 90% with a collection of mass percentage containing METHIONINE, in dry product, six parts are accurately taken respectively as sample to be tested, other mensuration process and step are specifically carried out according to the operation steps described in embodiment 1, divide the content of METHIONINE in sample to be tested and carry out measurement and calculation respectively six times, its concrete data recorded see the following form 2:

Table 2

Conclusion: by a collection of METHIONINE product replication six times in this example, the average content recording METHIONINE is 97.06%, RSD=0.12%, and this assay method result reappearance is better.

Embodiment 5 (mark-on recovery test)

A kind of assay method of L-methionine product content, it adopts the METHIONINE product totally 5 parts accurately taking known quality percentage composition, be placed in the volumetric flask of 5 100mL respectively, add the METHIONINE product that known quality percentage composition is 99.0% more respectively, as sample to be tested after being mixed, add 5mol/L dissolve with hydrochloric acid solution afterwards, be diluted to 100mL, shake up, as sample to be tested solution, measure according to the operation steps described in embodiment 1, calculate its recovery respectively, selecting of its reference substance and reference substance solution, measure identical with embodiment 1, its specific experiment data see the following form 3:

Table 3

Visible: this method measures the content of METHIONINE in product, and the recovery is between 97.28 ~ 100.20%, and average recovery rate is 98.64%, and its recovery is high, namely illustrate that this method accuracy is high.

Claims (1)

1. an assay method for L-methionine product content, is characterized in that, it specifically carries out according to following steps:

1. take the METHIONINE reference substance 2.0g that known quality percentage composition is at least 98.5%, claim accurate to 0.0001g, add 5mol/L dissolve with hydrochloric acid solution, be diluted to 100mL, shake up, product solution in contrast, injects afterwards and measures pipe, be placed in polarimeter and detect reading, obtain the optical activity of reference substance solution, wherein, the precision of polarimeter is 0.001o, and optically-active pipe range is 2dm, condition determination is the D line of sodium spectrum, and temperature is 20 ~ 30 DEG C;

2. the mass percentage getting the appropriate METHIONINE contained is at least the product of 90%, in dry product, constant weight is dried at 105 DEG C, take 2.0g wherein as sample to be tested, claim accurate to 0.0001g, afterwards according to the optical activity of the 1. described condition of step and time-and-motion study gained sample to be tested solution;

3. result calculates

Following formula calculates the content of METHIONINE in METHIONINE product, in dry product:

In formula, for the optical activity of sample to be tested solution;

for the optical activity of reference substance solution;

for the mass percentage of METHIONINE in reference substance, numerical value represents with %;

for the quality of reference substance taken, unit is g;

for the quality of sample to be tested taken, unit is g.