A kind of method of qualitative determination hydroxyl radical free radical in gas-phase reaction system
Technical field
The present invention relates to analysis and testing technology field, be specifically related to the method for qualitative determination hydroxyl radical free radical in a kind of gas-phase reaction system.
Background technology
In many advanced oxidation systems (as ultraviolet photolysis system), hydroxyl radical free radical (OH) is a kind of important living radical, and it has extremely strong oxidation.In known oxygenant, its oxidability is only second to F.OH is a kind of nonselective strong oxidizer, can easily be oxidized various organism and inorganics, and oxidation efficiency is high, and reaction velocity is fast, has extensively carried out at present the analysis of OH is measured to research in fields such as life science, environmental sciences.
At present, the method for mensuration OH mainly contains chemoluminescence method, fluorescence method, electron spin method of trapping (ESR), vapor-phase chromatography, high performance liquid chromatography (HPLC), electrochemical methods and spectrophotometric method etc.Because anti-application places is different with the scope of application, said method cuts both ways, but these methods are all for measuring the hydroxyl radical free radical of biological respinse or liquid-phase reaction system, and there is complicated operation, instrument reagent is special or the defect such as expensive, and its application is restricted.Particularly, in gas phase system, because the reactivity of OH is large, the life-span is short, approximately only has 1 μ s, and therefore existing these methods cannot be directly used in the OH measuring in gas-phase reaction system.
In some advanced oxidation systems, as ultraviolet photolysis system, photodissociation water generates hydroxyl radical free radical seems to be used by lot of documents as a kind of final conclusion, but rarely having document with direct-vision method, to go to prove the generation of hydroxyl radical free radical, is all scavenger its existence of indirect proof by complicated calculating of adding hydroxyl radical free radical conventionally.Therefore,, if can directly prove the existence of hydroxyl radical free radical, for course of reaction and study on mechanism, all have very important significance.
The patent No. is 200910036805.0, in the Chinese patent that patent name is " assay method of OH free radical in low-temperature plasma degradation organic waste gas ", disclosing a kind of method is comprised of following steps: (1) is dissolved in salicylic acid in absolute ethyl alcohol, and the concentration of salicylic acid in absolute ethyl alcohol is reached capacity, then be added drop-wise to equably on filter paper, dry; (2) step (1) gained filter paper is fully launched at the region of discharge of dielectric barrier discharge plasma reactor, it is fully contacted with the gas of the region of discharge of the reactor working chamber of flowing through; (3) energising was processed organic exhaust gas after 2~4 hours, take out described filter paper, after shredding, be soaked in water, then ultrasound wave is processed to the salicylic acid on filter paper and the reaction product 2 of hydroxyl radical free radical, 5-dihydroxy-benzoic acid is dissolved in water completely, and measures the amount that is dissolved in the DHB in water, the relation reckoning that is finally 1: 1 according to the molar weight of hydroxyl radical free radical that participates in reaction with the molar weight of DHB react in the content of hydroxyl radical free radical.Above-mentioned disclosed method is coated with the hydroxyl radical free radical in salicylic filter paper film qualitative determination gas phase for adopting, its defect and deficiency are owing to having adopted Adsorption of Filter Paper method in mensuration process, after dripping salicylic ethanolic solution on filter paper, need to dry, preparation process is comparatively complicated and consuming time; After this Adsorption of Filter Paper hydroxyl radical free radical, in ultrasound wave processing procedure, its reaction product 2,5-dihydroxy-benzoic acid may not be dissolved in water completely from filter paper after desorption, ultrasound wave has oxidisability simultaneously, may work and generate other material DHB, these two factors all can affect follow-up hydroxyl radical free radical qualitative, quantitative and measure.
Summary of the invention
Technical matters to be solved by this invention is to overcome deficiency of the prior art and method that qualitative determination hydroxyl radical free radical in a kind of gas-phase reaction system simple, direct, with low cost is provided.
The technical scheme that the present invention solves the problems of the technologies described above employing is: the method for qualitative determination hydroxyl radical free radical in this gas-phase reaction system, it is characterized in that: take salicylic acid as agent for capturing, make salicylic acid film, be coated on quartz glass plate, be placed in gas phase system to be measured and catch hydroxyl radical free radical, after question response 10min-60min, take out quartz glass plate and scrape salicylic acid film, carry out infrared spectrum (IR) analysis, thereby compare and determine whether gas phase system to be measured exists hydroxyl radical free radical by the infrared spectrum spectrogram with standard substance.Adopting salicylic acid is that bigcatkin willow very easily has uniqueness with hydroxyl radical reaction and product as the benefit of agent for capturing, and the object being coated on quartz glass plate is that coating rear surface is long-pending large and honest and kind suitable, easily fully contacts with the hydroxyl radical free radical in gas phase.
Salicylic acid film manufacturing method of the present invention is as follows: 0.1-1g salicylic acid powder is dissolved in 1-10mL ethanol, again salicylic ethanolic solution is slowly evenly dripped on the quartz glass plate mating with reactor, after ethanol volatilization, just on quartz glass plate surface, form one deck salicylic acid film.The salicylic acid that is formation according to the effect of above-mentioned dosage configuration salicylic acid ethanolic solution and benefit is better dispersed, concentration homogeneous, after ethanol volatilization, on quartz glass plate surface, form the salicylic acid thin layer of a layer thickness homogeneous, can increase the contact area of the hydroxyl radical free radical in salicylic acid and gas phase like this, salicylic acid is fully reacted with hydroxyl radical free radical.
Standard substance of the present invention is 2,3-dihydroxy-benzoic acid, and the infrared spectrum spectrogram of its infrared spectrum spectrogram and test substance is compared, if the two functional group characteristic peak overlaps, provable this gas phase system exists hydroxyl radical free radical.2,3-dihydroxy-benzoic acid is the production thing after salicylic acid and hydroxyl radical reaction, by the comparison of infrared spectrum spectrogram, can very intuitively determine in gas phase system to be measured whether have hydroxyl radical free radical fast.
The present invention compared with prior art has the following advantages: salicylic acid film preparation process is comparatively simple, does not need additional carrier (as filter paper etc.); Salicylic acid film after absorption hydroxyl radical free radical directly scrapes rear employing infrared spectrum measurement from quartz glass plate, centre does not experience other processing procedures, can not affect the amount of its reactant 2,3-dihydroxy-benzoic acid, therefore in gas phase, hydroxyl free base unit weight hour also can adopt, and required time of the process of whole absorption hydroxyl radical free radical is shorter.In addition, adopt infrared spectrum measurement reactant 2,3-dihydroxy-benzoic acid simple, convenient and rapid.
Accompanying drawing explanation
Fig. 1 a, Fig. 1 b, Fig. 1 c are in high humility nitrogen atmosphere, take 185nm ultraviolet light as light source, are opening uviol lamp and are closing under the condition of uviol lamp, respectively the salicylic acid film of gained and infrared spectrum (IR) comparison chart of standard substance after reaction.
Fig. 2 is in middle humidity ozone and air Mixture atmosphere, take 254nm ultraviolet light as light source, is opening under the condition of uviol lamp the salicylic acid film of gained and infrared spectrum (IR) comparison chart of standard substance after reaction.
Fig. 3 is in the air atmosphere that contains hydrogen peroxide, take 365nm ultraviolet light as lamp source, under the condition of close/open uviol lamp, and infrared spectrum (IR) comparison chart of the salicylic acid film of gained after reaction.
Embodiment
Embodiment 1:
0.3g salicylic acid is dissolved in 3mL ethanol, with glue head dropper, salicylic ethanolic solution is slowly evenly dropped on quartz glass plate, after ethanol volatilization, just can form one deck salicylic acid film.The quartz glass plate that this is coated with to salicylic acid film is put into and be take the airtight reaction system that vacuum UV lamp is light source, pass into the high pure nitrogen of high humility (more than 75%), open uviol lamp, after reaction 0.5h, take out quartz glass plate, scrape salicylic acid film, carry out infrared spectrum (IR) analysis.With the salicylic acid film of not opening uviol lamp gained as a comparison, the infrared spectrum spectrogram of these spectrograms and standard substance is compared, as shown in Figure 1.Result is as follows:
Due in infrared spectrum spectrogram, group characteristic frequency district (4000-1500cm
-1) absorption peak can be used for functional group contained in deterministic compound, from high frequency, be followed successively by hydrogen bond district (4000-2500cm
-1), three keypad (2500-2000 cm
-1) and two keypad (2000-1500cm
-1).Fingerprint region (1500-400cm
-1) peak is many and sharp-pointed, as appear at 650-1000 cm
-1the outwardly-bent vibration of hydrocarbon key that absorption peak in region mostly is on phenyl ring forms, and the absorption peak number that dissimilar substituted benzene produces and position (being frequency) are also different.
Fig. 1 a is out uviol lamp and does not open two kinds of salicylic acid film spectrogram (3500-1500cm that obtain under the condition of uviol lamp
-1), in the former infared spectrum at 3012.4 cm
-1occurred a new absorption peak, and this peak is in hydrogen bond district, therefore infers and may produce a new functional group with hydrogen bond.Fig. 1 b is out uviol lamp and does not open two kinds of salicylic acid film spectrogram (1500-400 cm that obtain under the condition of uviol lamp
-1), the former infared spectrum fingerprint region 964.8 cm
-1there is a new characteristic peak, infer that new functional group appears on phenyl ring.Therefore in view of the singularity of its structure of salicylic acid, the hydrogen bond on phenyl ring is very easily replaced by OH, infers that salicylic acid film and hydroxyl radical reaction have generated 2,3-dihydroxy-benzoic acid in this photodissociation system.For further confirmatory experiment result, by the infrared spectrum spectrogram of the salicylic acid film obtaining under uviol lamp unlocking condition and standard substance 2, the infrared spectrum spectrogram comparison (Fig. 1 c) of 3-dihydroxy-benzoic acid, find that both overlap, the characteristic peak of functional group is similar, therefore show that the material of salicylism reaction gained is 2,3-dihydroxy-benzoic acid, thereby determine that this gas phase system really has hydroxyl radical free radical to exist in ultraviolet photolysis process.Verified that the water molecule energy of reporting in document absorbs the ultraviolet light of 185nm, produces hydroxyl radical free radical.
Embodiment 2:
0.6g salicylic acid is dissolved in 6mL ethanol, with glue head dropper, salicylic ethanolic solution is slowly evenly dropped on quartz glass plate, after ethanol volatilization, just can form one deck salicylic acid film.The quartz glass plate that this is coated with to salicylic acid film is put into and be take the confined reaction system that predominant wavelength is light source as 254nm uviol lamp, pass into the air of middle humidity (45%-50%) and the gas that ozone mixes, open uviol lamp, after reaction 0.5h, take out quartz glass plate, scrape salicylic acid film, carry out infrared spectrum (IR) analysis.The infrared spectrum spectrogram of the spectrogram of gained and standard substance is compared, as shown in Figure 2.
By infrared spectrum spectrogram and the standard substance 2 of comparison salicylic acid film, the infrared spectrum spectrogram of 3-dihydroxy-benzoic acid, we find, both spectrograms are almost similar, characteristic group's peak overlaps, therefore infer that salicylic acid has absorbed hydroxyl radical free radical and generated 2,3-dihydroxy-benzoic acid in this ultraviolet photolysis system.Can determine thus, the hydroxyl radical free radical that truly has in this ultraviolet photolysis system exists.The ultraviolet light of having verified the Ozone Absorption 254nm reporting in document produces active oxygen, and this substance and water molecule reaction produce hydroxyl radical free radical.
Embodiment 3:
0.9g salicylic acid is dissolved in 9mL ethanol, with glue head dropper, salicylic ethanolic solution is slowly evenly dropped on quartz glass plate, after ethanol volatilization, just can form one deck salicylic acid film.The quartz glass plate that this is coated with to salicylic acid film is put into and be take the continuous stream reaction system that predominant wavelength is light source as 365nm uviol lamp, air is passed in hydrogen peroxide stripping bottle, the air of carrying hydrogen peroxide molecule after stripping secretly enters reaction system, opening and closing under the condition of uviol lamp respectively, each takes out quartz glass plate after reacting 3h, scrape salicylic acid film, carry out infrared spectrum (IR) analysis.By turn on light with the condition of turning off the light under the spectrogram of gained compare, as shown in Figure 3.
By comparison can find, in the infared spectrum obtaining under the condition of turning on light at 3012.4 cm
-1with 964.8 cm
-1there is respectively a new absorption peak, in conjunction with spectrogram handbook, can infer to have produced a new functional group with hydrogen bond and this functional group appears on phenyl ring.In conjunction with existing research, illustrate that this group is the hydroxyl radical free radical being connected on phenyl ring.Can determine thus, the hydroxyl radical free radical that truly has in this ultraviolet photolysis system exists.Verified that the hydrogen peroxide of reporting in document absorbs the ultraviolet light generation hydroxyl radical free radical of 365nm.
Embodiment 4:
0.3g salicylic acid is dissolved in 3mL ethanol, with glue head dropper, salicylic ethanolic solution is slowly evenly dropped on quartz glass plate, after ethanol volatilization, just can form one deck salicylic acid film.The quartz glass plate that this is coated with to salicylic acid film is put into and be take the continuous stream reaction system that vacuum UV lamp is light source, pass into the air/nitrogen (shown in table 1) of different humidity, open uviol lamp, after reaction 4h, take out quartz glass plate, scrape salicylic acid film, carry out infrared spectrum (IR) analysis.And these salicylic acids and product mixed-powder are dissolved in 10mL deionized water, adopt high performance liquid chromatography (HPLC) to measure 2 of generation, 3-dihydroxy-benzoic acid amount.Because the amount of 2,3-dihydroxy-benzoic acid and the amount of hydroxyl radical free radical are 1:1, therefore 2, the concentration of 3-dihydroxy-benzoic acid is the concentration of hydroxyl radical free radical.High-efficient liquid phase chromatogram determining condition: Supelcosil LC-18 reversed-phase column (250 * 4.6mm), detecting device wavelength is 254nm, flow velocity 1mL/min, mobile phase is 30% distilled water, 70%30mmol/L NaAc_HAc buffer solution (pH=4.9).The experimental result of measuring is as shown in table 1.
Under table 1 different condition, produce the concentration of hydroxyl radical free radical
As shown in Table 1, at uviol lamp, close or using under air/nitrogen of being dried condition as reaction medium, high performance liquid chromatography can't detect 2,3-dihydroxy-benzoic acid substantially, therefore can prove and in these systems, not have hydroxyl radical free radical.The salicylic acid film of gained under a certain reaction conditions wherein of take is example, and its infrared spectrum spectrogram is almost with not participate in the salicylic acid infrared spectrum spectrogram reacting similar.The conclusion of the analysis means gained that both are different is the same, has verified thus and under above-mentioned reaction conditions, in gas phase, has not really had hydroxyl radical free radical.
Under the state of opening at uviol lamp, no matter have the air of certain humidity or the high pure nitrogen of certain humidity as reaction medium, high performance liquid chromatography has all detected 2,3-dihydroxy-benzoic acid, therefore can prove in these systems and have hydroxyl radical free radical.The salicylic acid film of gained under a certain reaction conditions wherein of take is example, and the infrared spectrum spectrogram of its infrared spectrum spectrogram and 2,3-dihydroxy-benzoic acid is similar.These two kinds of methods have corroborated each other in this gas-phase reaction system and have had hydroxyl radical free radical.
Although the present invention with embodiment openly as above; but it is not in order to limit protection scope of the present invention; any technician who is familiar with this technology, not departing from change and the retouching of doing in the spirit and scope of the present invention, all should belong to protection scope of the present invention.