CN102519902B - Method for measuring water-soluble nitrogen content in plants and plant products - Google Patents
Method for measuring water-soluble nitrogen content in plants and plant products Download PDFInfo
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Abstract
The invention provides a method for measuring water-soluble nitrogen content in plants and plant products, which includes the following steps: extracting water-soluble nitrogen in a plant and a plant product to obtain a to-be-measured sample containing water-soluble nitrogen; adding potassium persulfate into the to-be-measured sample to obtain a mixed solution under the heating condition; performing ultraviolet catalysis and high-temperature heating to the mixed solution sequentially, so as to obtain a digestion product; detecting the digestion product to obtain ultraviolet spectrum data; and obtaining the water-soluble nitrogen content in the plant and the plant product as per the ultraviolet spectrum data and a predetermined standard curve. Through the adoption of the method provided by the invention, the digestion of the water-soluble nitrogen in the plant and the plant product is more complete, the digestion of the water-soluble nitrogen as well as the digestion of the reductive ingredient in the plant and the plant product can be realized, the reductive function of the to-be-measured sample is lost, the interference in the water-soluble nitrogen ingredient digestion is reduced, so that the digestion effect becomes more uniform, the recovery rate of the water-soluble nitrogen measurement is improved, and the accuracy of the measurement result is improved.
Description
Technical field
The present invention relates to the analysis determining technology field of nitrogen content, relate in particular to the assay method of water soluble nitrogen content in a Plants and vegetable products.
Background technology
Water-soluble nitrogen in plant and vegetable products, comprise nonprotein nitrogen and protein nitrogen.Wherein Maillard (Mei Lade easily occurs in amino acid and the reducing sugar component in water soluble protein or water-soluble nonprotein nitrogen, claim again wheat rad, plum rad, Mei Na or carbonyl amine) reaction, produce the macromolecular substances melanoidin of brownish black, also can produce simultaneously the intermediate molecule of hundreds and thousands of different odors, comprise reductone, aldehyde and heterogeneous ring compound etc., these materials provide pleasant good to eat local flavor and tempting color and luster for food, therefore, the content of water-soluble nitrogen has important impact to the quality of plant and vegetable products.For example, in tobacco, water soluble protein easily cigarette burn and suck or the sleep process in the generation Maillard such as sugar, react, produce fragrance matter, these materials are larger to the contribution of flue gas; And water soluble protein cracking in combustion process produce bad smell situation a little less than, so generally speaking water-soluble nitrogen containing component is larger to the front contribution of flue gas quality, strength and the richness of fragrance, the abundant degree of it and flue gas have close relationship, and the assay method tool of therefore setting up water soluble nitrogen content in a Plants and vegetable products is of great significance.
Mensuration for nitrogen content, usual way is that nitrogen-containing compound is cleared up, obtain to such an extent that nitrate quantitatively is reduced to nitrite, utilize the character of nitrite and sulfanilamide (SN) and N-naphthylethylenediamine hydrochloride reaction solution, adopt spectrophotometry nitrogen content wherein.As employing flow injection analyzers such as Zou Lin, total nitrogen in water and the content (Zou Lin of total phosphorus have been measured, Zhou Shengdong, Chen Wei. total nitrogen and total phosphorus in high-pressure digestion flow injection Simultaneous Spectrophotometric Determination water. Chinese water supply and drainage, 2009,25 (22): 93～97.), its process is: under 110 ℃ of conditions, water sample is cleared up for twice by alkaline potassium persulfate and sulfuric acid, the product of clearing up obtained enters respectively total nitrogen, the total phosphorus analytic system in flow injection analyzer, obtains the content of total nitrogen in water sample, total phosphorus.In the total nitrogen analytic system, clear up product by after copper-plated cadmium circle, nitrate radical quantitatively is reduced to nitrite anions, under acid condition, nitrite anions reacts and generates the aubergine material with sulfanilamide (SN), N-naphthylethylenediamine hydrochloride under 45 ℃ of constant temperatures, its optimum absorb wavelength is 550nm, adopts spectrophotometric method to measure the aubergine material obtained, and obtains the total nitrogen content in water.
This high-pressure digestion has and clears up preferably effect inorganic nitrogen, but for water-soluble nitrogen compounds such as vegetable soda, amino acid, water soluble protein nitrogen, as nicotine, theophylline, valine etc., because its structure is comparatively complicated, while adopting high-pressure digestion, exist and clear up incomplete, halfway phenomenon, thereby cause the recovery that water-soluble nitrogen is measured low, the measurement result obtained is inaccurate.For plant and plant sample, water-soluble nitrogen wherein is mainly vegetable soda, amino acid, water soluble protein nitrogen class, and in plant and vegetable products, also contain the reductibility composition, as carbohydrate, these reductibilities become branch and oxidant reaction, thereby impact is to the clearing up of nitrogen component, while adopting said method to measure water-soluble nitrogen wherein, what obtain clears up product not fully and thoroughly, causes measurement result inaccurate.
Summary of the invention
The object of the present invention is to provide the assay method of water soluble nitrogen content in a Plants and vegetable products, method provided by the invention has the higher recovery to the mensuration of water-soluble nitrogen, obtains measurement result accurate.
The invention provides the assay method of water soluble nitrogen content in a Plants and vegetable products, comprise the following steps:
A) extract the water-soluble nitrogen in plant and vegetable products, obtain containing the sample to be tested of water-soluble nitrogen;
B) under heating condition, in described sample to be tested, add potassium persulfate, obtain mixed solution;
C) described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product;
D) detect the described product of clearing up, obtain ultraviolet spectrum data;
E) according to described ultraviolet spectrum data and predetermined typical curve, obtain water soluble nitrogen content in plant and vegetable products.
Preferably, described ultraviolet catalytic is for carrying out ultraviolet catalytic in the non-sulfuric acid sour environment.
Preferably, the temperature of described ultraviolet catalytic is 90 ℃～110 ℃.
Preferably, the temperature of described high-temperature heating is 95 ℃～150 ℃.
Preferably, described high-temperature heating is the pressurized high-temperature heating.
Preferably, the pressure of described pressurized high-temperature heating is 5Psi～8Psi.
Preferably, the pressure of described pressurized high-temperature heating is 5.5Psi～7.5Psi.
Preferably, the heating-up temperature described step b) is 90 ℃～110 ℃.
Preferably, described step a) is specially:
In described plant and vegetable products, add water, obtain potpourri;
Filter described potpourri, obtain containing the sample to be tested of water-soluble nitrogen.
Preferably, described step b) frontly also comprise:
In described sample to be tested, add hydrogen peroxide, the reductibility component in the described sample to be tested of oxidation;
And/or add activated charcoal in described sample to be tested, remove the inorganic pigment in described sample to be tested;
And/or add disodium ethylene diamine tetraacetate in described sample to be tested, remove the metallic ion in described sample to be tested.
The invention provides the assay method of water soluble nitrogen content in a Plants and vegetable products, comprise the following steps: extract the water-soluble nitrogen in plant and vegetable products, obtain containing the sample to be tested of water-soluble nitrogen; Under heating condition, in described sample to be tested, add potassium persulfate, obtain mixed solution; Described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product; Detect the described product of clearing up, obtain ultraviolet spectrum data; According to described ultraviolet spectrum data and predetermined typical curve, obtain water soluble nitrogen content in plant and vegetable products.In method provided by the invention, potassium persulfate discharges active oxygen atom [O] under heating condition, at first the active oxygen atom obtained [O] can tentatively be cleared up plant and vegetable products, then under the ultraviolet catalytic condition, part active oxygen atom [O] reacts with water and generates free radical under the ultraviolet catalytic condition, this free radical is cleared up water-soluble nitrogen component in sample; Then, active oxygen atom [O] is further cleared up plant and vegetable products under hot conditions, and all kinds of water-soluble nitrogen components are cleared up fully.Method provided by the invention has also been cleared up reductibility composition wherein when the water-soluble nitrogen component in plant and vegetable products is cleared up, make it lose reducing action, eliminated the interference that the water-soluble nitrogen component is cleared up, the result of clearing up obtained has good homogeneity, improved the recovery that water soluble nitrogen content in plant and vegetable products is measured, the measurement result obtained is accurate.In addition, assay method provided by the invention has good stability and repeatability.
Experimental result shows, the recovery that method provided by the invention is measured nicotine in plant and vegetable products is 98.8%～100.9%, the recovery that theophylline is measured reaches 100.8%, and the recovery that valine is measured is 93.7%～101.4%, and the result obtained is accurate.In addition, method provided by the invention adopts the mode of clearing up continuously, simple to operate, save time, and step is easy, and clears up mild condition, and method batch processing sample capability provided by the invention is stronger, and treatment cycle is shorter, has greatly improved detection efficiency.
The accompanying drawing explanation
Fig. 1 is the ultraviolet spectrogram that the embodiment of the present invention 1 obtains;
Fig. 2 is the non-linear secondary standard curve that the embodiment of the present invention 1 obtains;
Fig. 3 is the linear standard curve that the embodiment of the present invention 1 obtains.
Embodiment
The invention provides the assay method of water soluble nitrogen content in a Plants and vegetable products, comprise the following steps:
A) extract the water-soluble nitrogen in plant and vegetable products, obtain containing the sample to be tested of water-soluble nitrogen;
B) under heating condition, in described sample to be tested, add potassium persulfate, obtain mixed solution;
C) described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product;
D) detect the described product of clearing up, obtain ultraviolet spectrum data;
E) according to described ultraviolet spectrum data and predetermined typical curve, obtain water soluble nitrogen content in plant and vegetable products.
For the ease of the mensuration to water soluble nitrogen content in plant and vegetable products, the present invention preferably carries out pre-treatment to plant and the vegetable products obtained, and specifically comprises the following steps:
Plant and vegetable products are dried, pulverize, obtain plant and vegetable products powder.Described bake out temperature is preferably 25 ℃～40 ℃, and more preferably 28 ℃～38 ℃, most preferably be 30 ℃～35 ℃, the granularity of described plant and vegetable products powder is preferably 60 orders～120 orders, and more preferably 65 orders～110 orders, most preferably be 80 orders～100 orders.
After obtaining plant and vegetable products powder, obtain the dry weight of described plant and vegetable products powder, the dry weight of described plant and vegetable products powder preferably obtains in accordance with the following methods:
Measure the moisture in described plant and vegetable products powder, the plant that the plant obtained with weighing and the quality of vegetable products powder deduction obtain and the moisture in the vegetable products powder, obtain the dry weight of described plant and vegetable products powder.The present invention preferably adopts the moisture in the described plant of oven method measuring and vegetable products powder, and described Oven Method is not particularly limited.The quality of plant and vegetable products powder is determined according to the degree of accuracy of measurement result, and in the present invention, the accuracy of measurement result is preferably 0.0001g～0.01g, more preferably 0.001g～0.01g.
After obtaining the dry weight of plant and vegetable products powder, the present invention extracts the water-soluble nitrogen in plant and vegetable products powder, obtains containing the sample to be tested of water-soluble nitrogen.
In the present invention, preferably in plant and vegetable products powder, add water, filter the mixed solution obtained, obtain filtrate, be the sample to be tested that contains water-soluble nitrogen.The mass ratio of the volume of described water and plant and vegetable products powder is preferably (25～100) mL: (0.3～1.0) g, more preferably (40～80) mL: (0.5～0.8) g.
In plant and vegetable products, the reductibility component is to the wherein interference of water soluble nitrogen content mensuration in order to reduce, and the present invention is the reductibility component in the described sample to be tested of preferential oxidation before described sample to be tested is cleared up.In plant described in the present invention and vegetable products, main reduction components is saccharide compound, preferably when total sugar content in described testing sample >=15%, in the time of more preferably >=20%, preferably in described testing sample, add hydrogen peroxide, the reductibility component in the described sample to be tested of oxidation.Reductibility component in described hydrogen peroxide and testing sample is carried out redox reaction, make it lose reducing action, the mass concentration of described hydrogen peroxide is preferably 3%～50%, more preferably 10%～30%, the proportioning of the present invention to described redox reaction Raw, reaction conditionss etc. are not particularly limited, and are the redox reaction between reducing substances well known to those skilled in the art and hydrogen peroxide.
The interference of water-soluble nitrogen being measured in order to reduce impurity, the present invention impurity preferably remove described sample to be tested before described sample to be tested is cleared up in, obtain containing the sample to be tested of water-soluble nitrogen.As described in while containing inorganic pigment in sample to be tested, can adopt following methods to process: preferably in described filtrate, to add activated charcoal, filter the mixed solution obtained, remove inorganic pigment wherein; While in described sample to be tested, containing metallic ion, can adopt following methods to process: preferably in described filtrate, to add disodium ethylene diamine tetra-acetic acid solution, the mixed solution that filtration obtains, remove metallic ion wherein, the concentration of described disodium ethylene diamine tetra-acetic acid solution is preferably 0.1g/L～5g/L, more preferably 0.2g/L～3g/L, most preferably be 0.8g/L～2g/L; While in described sample to be tested, containing inorganic pigment and metallic ion, can first with said method, remove inorganic pigment and remove again metallic ion, also can first with said method, remove metallic ion and remove again inorganic pigment.
After obtaining containing the sample to be tested of water-soluble nitrogen, the present invention, under heating condition, adds potassium persulfate in described sample to be tested, obtain mixed solution.Described potassium persulfate discharges active oxygen atom [O] under heating condition, the active oxygen atom obtained [O] can be cleared up the water-soluble nitrogen in sample to be tested, obtains clearing up product.The mass ratio of described potassium persulfate and described plant and vegetable products dry weight is preferably 1: (1～20), and more preferably 1: (2～15) most preferably are 1: (3～10); Preferably in sample to be tested, add potassium persulfate solution, the volumetric molar concentration of described potassium persulfate solution is preferably 0.1mol/L～1mol/L, and more preferably 0.15mol/L～0.8mol/L, most preferably be 0.25mol/L～0.5mol/L; Described heating-up temperature is preferably 90 ℃～110 ℃, more preferably 95 ℃～105 ℃.
After obtaining mixed solution, the present invention carries out ultraviolet catalytic and high-temperature heating successively by described mixed solution, obtains clearing up product;
At first described mixed solution is carried out to ultraviolet catalytic, obtain the product of clearing up of ultraviolet catalytic.In the ultraviolet catalytic process, part active oxygen atom obtained above [O] reacts with water under the condition of ultraviolet catalytic, preferably under the ultra violet lamp condition, generate free radical, described free radical can be cleared up reductibility components such as all kinds of organic nitrogens in sample to be tested, obtains the product of clearing up of ultraviolet catalytic.Described ultraviolet catalytic preferably carries out ultraviolet catalytic in the non-sulfuric acid sour environment, more preferably in the hydrochloric acid sour environment, carry out ultraviolet catalytic; The temperature of described ultraviolet catalytic is preferably 90 ℃～110 ℃, more preferably 95 ℃～105 ℃.
Obtain ultraviolet catalytic clear up product after, the present invention proceeds high-temperature heating by the product of clearing up of described ultraviolet catalytic, obtains the product of clearing up of described sample to be tested.In high-temperature heating process, active oxygen atom obtained above [O] product of clearing up to described ultraviolet catalytic under hot conditions is further cleared up, and obtains the product of clearing up of described testing sample.The temperature of described high-temperature heating is preferably 95 ℃～150 ℃, more preferably 110 ℃～140 ℃, most preferably is 120 ℃～130 ℃; Described high-temperature heating is preferably the pressurized high-temperature heating, and the pressure of described pressurized high-temperature heating is preferably 5Psi～8Psi, more preferably 5.5Psi～7.5Psi.
Obtain described sample to be tested clear up product after, detect the described product of clearing up, the present invention preferably adopts ultraviolet spectrophotometry to detect the described product of clearing up, and obtains the described ultraviolet spectrum data of clearing up product.The product of clearing up that at first will obtain reduces, obtain nitrite, then described nitrite is preferably reacted with sulfanilamide (SN) and N-(1-naphthyl) ethylenediamine dihydrochloride, obtain the aubergine product, the aubergine product that adopts determined by ultraviolet spectrophotometry to obtain, obtain the described ultraviolet spectrum data of clearing up product.Preferably with the product of clearing up that cadmium will obtain, reduce, obtain nitrite; The concentration of described sulfanilamide (SN) is preferably 1g/L～50g/L, and more preferably 10g/L～40g/L, most preferably be 20g/L～30g/L; The concentration of described N-naphthylethylenediamine hydrochloride is preferably 0.1g/L～10g/L, and more preferably 0.5g/L～8g/L, most preferably be 1g/L～5g/L; Described mensuration wavelength is preferably 520nm～560nm, and more preferably 530nm～550nm, most preferably be 535nm～545nm.
Ultraviolet spectrum data and predetermined typical curve according to technique scheme obtains, can obtain water soluble nitrogen content in plant and vegetable products.
In the present invention, described typical curve preferably obtains in accordance with the following methods:
The standard solution of preparation series concentration;
Under heating condition, in described standard solution, add potassium persulfate, obtain mixed solution;
Described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product;
Detect the described product of clearing up, obtain the ultraviolet spectrum data of series concentration standard solution;
According to described ultraviolet spectrum data drawing standard curve.
Described in the present invention, standard solution is preferably sodium nitrate aqueous solution, adopts the nitrate nitrogen standard of State Standard Matter Research Centre, the standard solution of preparation series concentration.At first, prepare the storing solution of standard substance, the storing solution obtained is diluted to the concentration of standard solution.The mass concentration of described standard solution is preferably 0.001%～10%, and more preferably 0.01%～5%, most preferably be 0.1%～1%; Preferably water is diluted to the standard substance storing solution concentration of standard solution.
After obtaining the standard solution of series concentration, the present invention, under heating condition, adds potassium persulfate in described standard solution, obtain mixed solution.Described potassium persulfate discharges active oxygen atom [O] under heating condition, the active oxygen atom obtained [O] can be cleared up described standard solution, obtains clearing up product.The mass ratio of described potassium persulfate and described standard solution Plays material is preferably 1: (1～20), and more preferably 1: (2～15) most preferably are 1: (3～10); Preferably in described standard solution, add potassium persulfate solution, the volumetric molar concentration of described potassium persulfate solution is preferably 0.1mol/L～1mol/L, and more preferably 0.15mol/L～0.8mol/L, most preferably be 0.25mol/L～0.5mol/L; Described heating-up temperature is preferably 90 ℃～110 ℃, more preferably 95 ℃～105 ℃.
After obtaining mixed solution, described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product.Described ultraviolet catalytic is identical with ultraviolet catalytic and high-temperature heating process in technique scheme with high-temperature heating process.
According to the ultraviolet catalytic in technique scheme and high-temperature heating process, after obtaining clearing up product, detect the described product of clearing up, obtain the ultraviolet spectrum data of series concentration standard solution.Described testing process is identical with the testing process in technique scheme.
According to the testing process in technique scheme, after obtaining the ultraviolet spectrum data of series concentration standard solution, according to described ultraviolet spectrum data and corresponding concentration drawing standard curve thereof, described typical curve is preferably non-linear secondary standard curve or linear standard curve.
Ultraviolet spectrum data and typical curve that the plant obtained according to technique scheme and vegetable products are cleared up product, through calculating the quality of water-soluble nitrogen in plant and vegetable products, by the dry weight of the quality of described water-soluble nitrogen divided by above-mentioned plant and vegetable products, obtain water soluble nitrogen content in plant and vegetable products again.
In the present invention, nicotine, theophylline and valine in the water-soluble nitrogen that plant and vegetable products are contained are measured, and result shows, the recovery that method provided by the invention is measured nicotine, theophylline and valine is higher, and measurement result is accurate.
Nicotine, be commonly called as nicotine, is a kind of alkaloid be present in plant of Solanaceae, has formula (I) structure:
Theophylline is heterocyclic nitrogen compound, and a kind of for vegetable soda in plant and vegetable products has formula (II) structure:
Valine is one of essential amino acid, is one of water-soluble nitrogen compound important in plant and vegetable products, has formula (III) structure:
In plant provided by the invention and vegetable products in the assay method of water soluble nitrogen content, the active oxygen atom that potassium persulfate discharges [O] is at first tentatively cleared up plant and vegetable products, then at ultraviolet catalytic and high-temperature heating condition part active oxygen atom [O], the sample to be tested of plant and vegetable products is cleared up further successively, make water-soluble nitrogen wherein be cleared up more fully and up hill and dale, and eliminated the impact on measuring of wherein reductibility composition, has the good effect of clearing up, improved the homogeneity of clearing up the product tool, the recovery that method provided by the invention is measured water soluble nitrogen content in plant and vegetable products is high, result is accurate.Experimental result shows, the recovery that method provided by the invention is measured the nicotine in water-soluble nitrogen is 98.8%～100.9%, and the recovery of theophylline reaches 100.8%, and the recovery of valine is 93.7%～101.4%.In addition, method provided by the invention has good stability and repeatability.
In order to further illustrate the present invention, below in conjunction with embodiment, water soluble nitrogen content assay method in plant provided by the invention and vegetable products is described in detail, but they can not be interpreted as to the restriction to protection domain of the present invention.
11g sodium nitrate is dissolved in 100mL distilled water, obtains mass concentration and be 10.0% sodium nitrate storing solution.Accurately pipette 1.0mL, 2.0mL, 4.0mL, 6.0mL, the described standard reserving solution of 8.0mL, 10.0mL, water constant volume respectively, to 100mL, obtains the sodium nitrate standard solution to be measured of series concentration.Get respectively described standard solution 2mL to be measured, in impouring Continuous Flow Analysis instrument sample hose, the difference replicate determination is three times, gets its mean value.In the Continuous Flow Analysis instrument, the sample feeding amount is 0.1mL/min, and sample injection time is 100s, and flush time is 120s.At first under 90 ℃, to adding the 2mL volumetric molar concentration in described standard solution to be measured, it is the potassium persulfate solution of 0.3mol/L, the sample size of potassium persulfate solution is 0.8mL/min, then the mixed solution obtained is at 90 ℃, under the acid condition that hydrochloric acid provides, carry out ultra violet lamp 3min, the ultraviolet catalytic that then high-temperature heating obtains under 6Psi pressure clear up product 2.5min, heating-up temperature is 110 ℃, obtains the product of clearing up of sample.Clearing up when product passes through the cadmium post of obtaining is reduced to nitrite, enters detecting device and carries out determined by ultraviolet spectrophotometry, and the detection wavelength is 540nm, obtains the ultraviolet spectrogram of standard substance.
As shown in Figure 1, Fig. 1 is the ultraviolet spectrogram that the embodiment of the present invention 1 obtains to the ultraviolet spectrogram of standard substance, and the signal fork in figure on curve is followed successively by the electrical signal intensity of the standard solution of series concentration since the 5th back to back 6 signals fork.According to the ultraviolet spectrogram of the standard substance of the series concentration obtained and corresponding concentration thereof, draw and obtain typical curve, as shown in Figures 2 and 3, Fig. 2 is the non-linear secondary standard curve that the embodiment of the present invention 1 obtains, Fig. 3 is the linear standard curve that the embodiment of the present invention 1 obtains, the nitrate concentration range of linearity of linear standard curve shown in Figure 3 is 0.1%～1%, linear equation is: A (absorbance)=-1076.98+47750.43C (%), correlation coefficient r is 0.9981.As can be seen from Figure, method provided by the invention is significantly improved to the electrical signal intensity of nitrogen analysis, and has good linear relationship between electrical signal intensity and its concentration, and method provided by the invention has good effect.
Comparative example 1
11g sodium nitrate is dissolved in 100mL distilled water, obtains mass concentration and be 10.0% sodium nitrate storing solution.Accurately pipette 1.0mL, 2.0mL, 4.0mL, 6.0mL, the described standard reserving solution of 8.0mL, 10.0mL, water constant volume respectively, to 100mL, obtains the sodium nitrate standard solution of series concentration.The standard solution 2mL obtained respectively, in impouring Continuous Flow Analysis instrument sample hose, the difference replicate determination is three times, gets its mean value.In the Continuous Flow Analysis instrument, the sample feeding amount is 0.1mL/min, and sample injection time is 100s, and flush time is 120s.At first under 90 ℃, to adding the 2mL volumetric molar concentration in described standard solution, it is the potassium persulfate solution of 0.3mol/L, the sample size of potassium persulfate solution is 0.8mL/min, then the mixed solution 2.5min obtained in the heating of 6Psi high-pressure high-temperature, heating-up temperature is 110 ℃, obtains the product of clearing up of sample.Clearing up when product passes through the cadmium post of obtaining is reduced to nitrite, enters detecting device and carries out the ultraviolet spectrophotometry detection, and the detection wavelength is 540nm, obtains the ultraviolet spectrogram of standard substance.
According to the ultraviolet spectrogram of the standard substance of the series concentration obtained, draw and obtain typical curve.
Embodiment 2～3
3.2446g nicotine is dissolved with distilled water and is settled to 200mL, obtain mass concentration and be 1.60% nicotine storing solution.Pipette the described nicotine storing solution of 16.0mL, 32.0mL, to 100mL, obtain nicotine solution to be measured with the distilled water constant volume.Pipette the nicotine solution to be measured of the described two kinds of variable concentrations of 2.0mL, in impouring Continuous Flow Analysis instrument sample hose, the difference replicate determination is three times, gets its mean value.In the Continuous Flow Analysis instrument, the sample feeding amount is 0.1mL/min, and sample injection time is 100s, and flush time is 120s.At first under 90 ℃, to adding the 2mL volumetric molar concentration in described nicotine solution to be measured, it is the potassium persulfate solution of 0.3mol/L, the sample size of potassium persulfate solution is 0.8mL/min, then the mixed solution obtained carries out ultra violet lamp 3min under the acid condition that 90 ℃, hydrochloric acid provide, the ultraviolet catalytic that then high-temperature heating obtains under 6Psi pressure clear up product 2.5min, heating-up temperature is 110 ℃, obtains the product of clearing up of nicotine sample.Clearing up when product passes through the cadmium post of obtaining is reduced to nitrite, enters detecting device and carries out the ultraviolet spectrophotometry detection, and the detection wavelength is 540nm, obtains the ultraviolet spectrogram of nicotine.
The typical curve obtained according to ultraviolet spectrogram and the embodiment 1 of the nicotine obtained, obtain the nitrogen content of nicotine, the average quality that calculates nicotine is respectively 5.113mg, 10.448mg, the recovery that nicotine is measured is 98.8%, 100.9%, result is as shown in table 1, the measurement result that table 1 obtains for the embodiment of the present invention 2～3 and comparative example 2～3.
Comparative example 2～3
3.2446g nicotine is dissolved with distilled water and is settled to 200mL, obtain mass concentration and be 1.60% nicotine storing solution.Pipette the described nicotine storing solution of 16.0mL, 32.0mL, to 100mL, obtain nicotine solution to be measured with the distilled water constant volume.Pipette the nicotine solution to be measured of the described two kinds of variable concentrations of 2.0mL, in impouring Continuous Flow Analysis instrument sample hose, the difference replicate determination is three times, gets its mean value.In the Continuous Flow Analysis instrument, the sample feeding amount is 0.1mL/min, and sample injection time is 100s, and flush time is 120s.At first under 90 ℃, to adding the 2mL volumetric molar concentration in described nicotine solution to be measured, it is the potassium persulfate solution of 0.3mol/L, the sample size of potassium persulfate solution is 0.8mL/min, then the mixed solution 2.5min obtained in the heating of 6Psi high-pressure high-temperature, heating-up temperature is 110 ℃, obtains the product of clearing up of sample.Clearing up when product passes through the cadmium post of obtaining is reduced to nitrite, enters detecting device and carries out the ultraviolet spectrophotometry detection, and the detection wavelength is 540nm, obtains the ultraviolet spectrogram of nicotine.
The typical curve obtained according to ultraviolet spectrogram and the comparative example 1 of the nicotine obtained, obtain the nitrogen content of nicotine, the average quality that calculates nicotine is 3.943mg, 7.184mg, the recovery that nicotine is measured is 75.95%, 69.19%, result is as shown in table 1, the measurement result that table 1 obtains for the embodiment of the present invention 2～3 and comparative example 2～3.
The measurement result that table 1 embodiment of the present invention 2～3 and comparative example 2～3 obtain
As shown in Table 1, the recovery that method provided by the invention is measured nicotine is 98.8%～100.9%, and the measurement result accuracy is high.
Embodiment 4
The 3.6032g theophylline is dissolved with distilled water and is settled to 100mL, obtain mass concentration and be 3.48% theophylline storing solution.Pipette the described theophylline storing solution of 5mL, to 100mL, obtain theophylline solution to be measured with the distilled water constant volume.Pipette the described theophylline of 2.0mL solution to be measured, in the sample hose of impouring Continuous Flow Analysis instrument, carry out three replicate determinations, get its mean value, testing process is identical with the testing process of embodiment 2～3, obtains the ultraviolet spectrogram of theophylline.
The typical curve obtained according to ultraviolet spectrogram and the embodiment 1 of theophylline, obtain the nitrogen content of theophylline, the average quality that calculates theophylline is 3.633mg, and the recovery that theophylline is measured is 100.8%, result is as shown in table 2, the measurement result that table 2 obtains for the embodiment of the present invention 4 and comparative example 4.
Comparative example 4
The 3.6032g theophylline is dissolved with distilled water and is settled to 100mL, obtain mass concentration and be 3.48% theophylline storing solution.Pipette the described theophylline storing solution of 5mL, to 100mL, obtain theophylline solution to be measured with the distilled water constant volume.Pipette the described theophylline of 2.0mL solution to be measured, in the sample hose of impouring Continuous Flow Analysis instrument, replicate determination is three times, gets its mean value, and testing process is identical with the testing process of comparative example 2～3, obtains the ultraviolet spectrogram of theophylline.
The typical curve obtained according to ultraviolet spectrogram and the comparative example 1 of the theophylline obtained, obtain the nitrogen content of theophylline, the average quality that calculates theophylline is respectively 2.162mg, the recovery that theophylline is measured is 59.0%, result is as shown in table 2, the measurement result that table 2 obtains for the embodiment of the present invention 4 and comparative example 4.
The measurement result that table 2 embodiment of the present invention 4 and comparative example 4 obtain
As shown in Table 2, the recovery that method provided by the invention is measured theophylline reaches 100.8%, and the measurement result accuracy is high.
Embodiment 5～7
The 4.686g valine is dissolved with distilled water and is settled to 200mL, obtain mass concentration and be 2.29% valine storing solution.Accurately pipette 8.0mL, 12.5mL, the described valine storing solution of 15.0mL, to 100mL, obtain valine solution to be measured with the distilled water constant volume.Pipette the described valine of 2.0mL solution to be measured, in impouring Continuous Flow Analysis instrument sample hose, replicate determination is three times, gets its mean value, and testing process is identical with the described testing process of embodiment 2～3, obtains the ultraviolet spectrogram of valine.
The typical curve obtained according to ultraviolet spectrogram and the embodiment 1 of the valine obtained, obtain the nitrogen content of valine, the quality that calculates valine is respectively 3.750mg, 5.562mg, 7.128mg, the recovery that valine is measured is respectively 100.0%, 93.7%, 101.4%, result is as shown in table 3, the measurement result that table 3 obtains for the embodiment of the present invention 5～7 and comparative example 5～7.
Comparative example 5～7
The 4.686g valine is dissolved with distilled water and is settled to 200mL, obtain mass concentration and be 2.29% valine storing solution.Accurately pipette 8.0mL, 12.5mL, the described valine storing solution of 15.0mL, to 100mL, obtain valine solution to be measured with the distilled water constant volume.Pipette the described valine of 2.0mL solution to be measured, in impouring Continuous Flow Analysis instrument sample hose, replicate determination is three times, gets its mean value, and testing process is identical with the testing process of comparative example 2～3, obtains the ultraviolet spectrogram of valine.
The typical curve obtained according to ultraviolet spectrogram and the comparative example 1 of the valine obtained, obtain the nitrogen content of valine, the quality that calculates valine is respectively 2.816mg, 4.381mg, 5.526mg, the recovery that valine is measured is respectively 75.1%, 74.8%, 78.6%, result is as shown in table 3, the measurement result that table 3 obtains for the embodiment of the present invention 5～7 and comparative example 5～7.
The measurement result that table 3 embodiment of the present invention 5～7 and comparative example 5～7 obtain
As shown in Table 3, the recovery that method provided by the invention is measured valine is 93.7%～101.4%, and the measurement result accuracy is high.
As seen from the above embodiment, method provided by the invention has the good effect of clearing up to the water-soluble nitrogen compound, and the recovery obtained is high, and the result obtained is accurate.
The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (9)
1. the assay method of water soluble nitrogen content in a Plants and vegetable products comprises the following steps:
A) extract the water-soluble nitrogen in plant and vegetable products, obtain containing the sample to be tested of water-soluble nitrogen;
B) under heating condition, in described sample to be tested, add potassium persulfate, obtain mixed solution;
C) described mixed solution is carried out to ultraviolet catalytic and high-temperature heating successively, obtain clearing up product, the temperature of described high-temperature heating is 95 ℃～150 ℃;
D) detect the described product of clearing up, obtain ultraviolet spectrum data;
E) according to described ultraviolet spectrum data and predetermined typical curve, obtain water soluble nitrogen content in plant and vegetable products.
2. assay method according to claim 1, is characterized in that, described ultraviolet catalytic is for carrying out ultraviolet catalytic in the non-sulfuric acid sour environment.
3. assay method according to claim 1, is characterized in that, the temperature of described ultraviolet catalytic is 90 ℃～110 ℃.
4. assay method according to claim 1, is characterized in that, described high-temperature heating is the pressurized high-temperature heating.
5. assay method according to claim 4, is characterized in that, the pressure of described pressurized high-temperature heating is 5Psi～8Psi.
6. assay method according to claim 4, is characterized in that, the pressure of described pressurized high-temperature heating is 5.5Psi～7.5Psi.
7. assay method according to claim 1, is characterized in that, the heating-up temperature in described step b) is 90 ℃～110 ℃.
8. assay method according to claim 1, is characterized in that, described step a) is specially:
In plant and vegetable products, add water, obtain potpourri;
Filter described potpourri, obtain containing the sample to be tested of water-soluble nitrogen.
9. assay method according to claim 1, is characterized in that, also comprises before described step b):
In described sample to be tested, add hydrogen peroxide, the reductibility component in the described sample to be tested of oxidation;
And/or add activated charcoal in described sample to be tested, remove the inorganic pigment in described sample to be tested;
And/or add disodium ethylene diamine tetraacetate in described sample to be tested, remove the metallic ion in described sample to be tested.
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