CN102393429A - Method for detecting trace phosphine gas in water sample by gas chromatograph (GC)-cooperating pre-column twice cold trap enrichment method - Google Patents

Abstract

The invention provides a method for detecting trace phosphine gas in a water sample by a gas chromatograph (GC)-cooperating pre-column twice cold trap enrichment method, and aims to overcome the shortcomings of the existing various measurement methods. The method mainly comprises the following steps of: (1) cooling and enriching the phosphine gas and establishing a GC/NPD (nitrogen phosphorous detector) detection device; (2) extracting and dissolving the phosphine gas in lake water by a gas-liquid two-phase phase equilibrium method, and preparing a gas sample to be detected; (3) preprocessing the gas sample; (4) extracting a certain volume of the gas sample into a gas absorption tube; (5) performing primary enrichment of the processed gas sample in a cold trap I, and removing the impurity gas with a relatively low boiling point; (6) heating the cold trap I so that the gas enters a cold trap II for secondary enrichment; (7) detecting the final enrichment product by a nitrogen phosphorous detector in a gas chromatograph through a chromatographic column; and (8) converting the measured area of a characteristic peak of the phosphine according to a certain formula to obtain the concentration of the phosphine in the water sample to be detected.

Description

A kind of gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample

Technical field

This invention belongs to the environmental monitoring field, relates in particular to a kind of gas chromatography and cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample.

Background technology

Phosphorus is the restriction factor of algae reproduction in the water body.Along with the Chinese society expanding economy, the phosphorus that China enters in the natural water body increases day by day, has caused serious eutrophication phenomenon.At present the waste water dephosphorization method taked of China comprises chemical dephosphorization, biological phosphate-eliminating etc., all produces a large amount of mud, need expend higher cost and mud handled, so the low phosphorus removing method of research sludge yield has become present research focus.

Hydrogen phosphide is again a kind of poisonous and active gas that can be carcinogenic; Human body sucks symptoms such as just can causing n and V, uncomfortable in chest, diarrhoea on a small quantity; So can cause pulmonary edema even the discovery of dead this compound of stupor in environment to cause people's common concern at once when serious, to its distribution in various environment! Transform and generting machanism etc. done a series of researchs.

In biomass geochemistry round-robin traditional understanding, there is not the phosphorus containg substances of gaseous state to phosphorus.Up to 1988, people such as D é vai successfully detected the existence of free state hydrogen phosphide first in the volatile matter of sewage treatment plant, and hydrogen phosphide begins to cause people's extensive concern to the influence and the status in the circulation of phosphorus biomass geochemistry thereof of environment with effect.Hydrogen phosphide is as to the biomass geochemistry round-robin important supplement of phosphorus, and its role, status and generation in circulation, the mechanism of loss it be unclear that.Research to hydrogen phosphide; Helping to understand with the gaseous state phosphorus containg substances is the mechanism of the natural reaction of product, achievement in research can be applied to batch production water body dephosphorized in, realize sludge reduction in the dephosphorization process; Reduce processing cost greatly, also can be applied in the reparation of body eutrophication.

Natural water body is important a ring, especially a water body in lake of the biomass geochemistry round-robin of phosphorus, is usually mainly regarded as the remittance of phosphorus, but hydrogen phosphide detecting in physical environment show, also possibly have the gaseous state phosphorus containg substances in the natural water body.The generation of gaseous state phosphorus containg substances in natural water body and the research that consumes mechanism will be made important supplement to existing phosphorus biomass geochemistry Cyclical Theory.

But because hydrogen phosphide content in physical environment is very little; The detectability of conventional method is too high; Collection, preservation and the beneficiation technologies of phosphine gas do not reach a standard as yet simultaneously, and therefore the conventional sense technology is difficult to realize the hydrogen phosphide under the natural condition is carried out quantitative measurement for a long time.Domestic mensuration hydrogen phosphide mainly adopts molybdate colourimetry, vapor-phase chromatography and fourier infrared analyser, and the detecting device of use is not quite similar, but detectability all fails to satisfy the detection requirement of trace hydrogen phosphide.

Patent documentation CN101281178A discloses a kind of quantitative detecting method and enriching apparatus of trace phosphine gas; But the extraction and the computing method of solubilised state phosphatization hydrogen in the water sample are not disclosed; On this basis; The invention discloses a kind of gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample; Especially the computing method of improvement solubilised state phosphatization hydrogen in having set up method that the biphase equilibrium method extracts phosphine gas and water body, the algorithm of hydrogen phosphide content during this is invented

$m_g=\frac{m^{\′}}{V^{\′}}{V}_g---\left(1\right)$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g---\left(2\right)$

m _g(pg)--------during-----gas-liquid two-phase balance, be distributed in the quality of the hydrogen phosphide in the gas phase;

M ' is------quality of institute's phosphine containing in the gas appearance of-----preparation (pg);

V ' is----------volume of the gas appearance of----preparation (l);

V _g(l)------during-----gas-liquid two-phase balance, gaseous phase volume, V _g=20ml;

C (pg/l)--------the hydrogen phosphide mass concentration of-----water sample to be measured;

V _l(l)----------the volume of-----water sample to be measured;

C _l(pg/l)--------during----gas-liquid two-phase balance, be distributed in the mass concentration of hydrogen phosphide in the liquid phase;

R (J/ (Kmol))--ideal gas constant, R=8.314J/ (Kmol);

The molal weight of M (pg/mol)----hydrogen phosphide;

K (Pal/pg)----Henry's constant;

T (the K)------thermodynamic temperature of gas-liquid two-phase system when-----gas-liquid two-phase balancing method is extracted hydrogen phosphide;

Also belong to open first, filled up domestic and international blank.In addition, the sealing injection device injects through six-way injection valve, to the necessary online large volume sample injection of trace gas; After enrichment, can detect; Big volume syringe is one of improvement of the application, avoids systematic error that the microsyringe repeatable operation brings etc., and the six-way injection valve other end connects high pure nitrogen gas to be measured is all pushed the cold-trap post No. one; Reduce dead volume, increased repeatability and the reliability of measuring the result.

The present invention extracts the phosphine gas in the water sample through the gas-liquid two-phase balancing method; Adopt gas chromatography to cooperate the preceding twice cold-trap concentration method of post; Realized the on-line preconcentration and accurately measurement of trace hydrogen phosphide in the water sample, when analyzing 10～100mL gas appearance, its detectability has reached 0.1ng/m ³, and in natural water body, detect hydrogen phosphide, at home and abroad all belong to first.

Summary of the invention

The objective of the invention is:

Be dissolved in the phosphine gas in the water sample through the extraction of gas-liquid two-phase balancing method, take gas chromatography to cooperate the preceding twice cold-trap concentration method of post again, realize quantitative measurement trace phosphine gas in the water sample.

The present invention's scheme more specifically is:

After adopting the gas-liquid two-phase balancing method to extract to be dissolved in the phosphine gas in the water sample, lucifuge be stored in to gas do not absorb and the airbag that adsorb in, press certain working specification subsequently from the six-way injection valve sample introduction,

Hydrogen phosphide composition in the sample introduction gas gets into gas chromatograph after twice enrichment in the cold-trap before two posts; The response signal that reads nitrogen phosphorous detector is integration in addition; According to integral area,, calculate the total amount of hydrogen phosphide in the sample introduction gas through the typical curve equation of hydrogen phosphide content in the integral area set up and the sample introduction gas; According to the sample introduction gas volume, converse phosphine concentration in the water sample to be measured.

The present invention can be divided into following steps in detail:

A kind of gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample, it is characterized in that concrete steps are following:

(gas chromatography nitrogen phosphorous detector (GC/NPD), the producer of all devices all is in this detection method: the establishment of pick-up unit Shanghai thunder rhythm test apparatus Manufacturing Co., Ltd) for A, phosphine gas cooling enrichment and GC/NPD

Cooling enrichment of assembling phosphine gas and GC/NPD pick-up unit; The testing equipment that requires is: Agilent 4890D gas chromatograph; Thermionic nitrogen and phosphorous detector (NPD) is housed; Chromatographic column is to adopt the capillary column of " 25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard " Crosslinked 5%Ph Me Silicone; Six-way injection valve; The thermos cup of two 2L is made cold-trap; Liquid nitrogen;

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃～280 ℃ of detector temperatures; The flow velocity of carrier gas---nitrogen is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23;

B, employing gas-liquid two-phase balancing method prepare gaseous sample

Accurately draw the 30mL water sample with the 50mL syringe; Inject high pure nitrogen 20mL then; Acutely shake 10～20 minutes up and down to displace phosphine gas wherein; Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in;

The pre-service of C, gaseous sample to be measured

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO testing sample injecting gas absorption tube ₂, H ₂O and H ₂S etc. can produce the gas that disturbs to measuring;

The first cold-trap enrichment of D, hydrogen phosphide

Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge from gas vent;

The secondary cold-trap enrichment of E, hydrogen phosphide

Six-way injection valve is transformed into " on " position, more than the collection tube to 0 of a cold-trap post of Fast Heating ℃, makes gaseous sample brought into No. two cold-traps fast and carry out enrichment once more by nitrogen carrier gas;

The gas chromatograph of F, band nitrogen phosphorous detector detects gas appearance to be measured

After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak;

G, drawing standard curve

Get the standard phosphine gas; Be diluted to the concentration of varying number level by volume with standard nitrogen, same subsequently concentration standard phosphine gas is got 5ml, 10ml, 20ml, 30ml, 40ml, 50ml respectively, and B to E operates set by step; Obtain characteristic peak area separately; The gas appearance institute phosphine containing quality of injecting is made typical curve to corresponding characteristic peak area, and fitting formula, obtain under this order of magnitude the reduction formula of institute's phosphine containing quality and character pair peak area in the gaseous sample;

H, data processing and numerical value convert:

In the characteristic peak area substitution fitting formula with testing sample, calculate the quality of institute's phosphine containing in the testing sample, subsequently the following formula of result of calculation substitution calculated:

$m_g=\frac{m^{\′}}{V^{\′}}{V}_g---\left(1\right)$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g---\left(2\right)$

m _g(pg)--------during-----gas-liquid two-phase balance, be distributed in the quality of the hydrogen phosphide in the gas phase;

M ' is------quality of institute's phosphine containing in the gas appearance of-----preparation (pg);

V ' is----------volume of the gas appearance of----preparation (l);

V _g(l)------during-----gas-liquid two-phase balance, gaseous phase volume, V _g=20ml;

C (pg/l)--------the hydrogen phosphide mass concentration of-----water sample to be measured;

V _l(l)----------the volume of-----water sample to be measured;

C _l(pg/l)--------during----gas-liquid two-phase balance, be distributed in the mass concentration of hydrogen phosphide in the liquid phase;

R (J/ (Kmol))--ideal gas constant, R=8.314J/ (Kmol);

The molal weight of M (pg/mol)----hydrogen phosphide;

K (Pal/pg)----Henry's constant;

T (the K)------thermodynamic temperature of gas-liquid two-phase system when-----gas-liquid two-phase balancing method is extracted hydrogen phosphide;

Result of calculation is the hydrogen phosphide content of water sample to be measured.

Preferably, a kind of gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample, it is characterized in that concrete steps are following:

The establishment of A, phosphine gas cooling enrichment and GC/NPD pick-up unit

Cooling enrichment of assembling phosphine gas and GC/NPD pick-up unit; The testing equipment that requires is: Agilent 4890D gas chromatograph; Thermionic nitrogen and phosphorous detector (NPD) is housed; Chromatographic column is to adopt the capillary column of " 25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard " Crosslinked 5%Ph Me Silicone; Six-way injection valve; The thermos cup of two 2L is made cold-trap; Liquid nitrogen;

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃～280 ℃ of detector temperatures; The flow velocity of carrier gas---nitrogen is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23;

B, employing gas-liquid two-phase balancing method prepare gaseous sample

Accurately draw the 30mL water sample with the 50mL syringe; Testing sample is injected through six-way injection valve from syringe; Add the 1.2g composite flocculation agent and carry out preliminary sedimentation; The component of said composite flocculation agent is zeyssatite and aluminium polychloride (PAC), and the weight ratio of said zeyssatite and aluminium polychloride (PAC) is a zeyssatite: aluminium polychloride is 40-100: 10-25; Inject high pure nitrogen 20mL then, acutely shake 10～20 minutes up and down displacing phosphine gas wherein, draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in;

The pre-service of C, gaseous sample to be measured

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO testing sample injecting gas absorption tube ₂, H ₂O and H ₂S etc. can produce the gas that disturbs to measuring;

The first cold-trap enrichment of D, hydrogen phosphide

Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge from gas vent;

The secondary cold-trap enrichment of E, hydrogen phosphide

Six-way injection valve is transformed into " on " position, more than the collection tube to 0 of a cold-trap post of Fast Heating ℃, makes gaseous sample brought into No. two cold-traps fast and carry out enrichment once more by nitrogen carrier gas;

The gas chromatograph of F, band nitrogen phosphorous detector detects gas appearance to be measured

After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak;

G, drawing standard curve

Get the standard phosphine gas; Be diluted to the concentration of varying number level by volume with standard nitrogen, same subsequently concentration standard phosphine gas is got 5ml, 10ml, 20ml, 30ml, 40ml, 50ml respectively, and B to E operates set by step; Obtain characteristic peak area separately; The gas appearance institute phosphine containing quality of injecting is made typical curve to corresponding characteristic peak area, and fitting formula, obtain under this order of magnitude the reduction formula of institute's phosphine containing quality and character pair peak area in the gaseous sample;

H, data processing and numerical value convert:

In the characteristic peak area substitution fitting formula with testing sample, calculate the quality of institute's phosphine containing in the testing sample, subsequently the following formula of result of calculation substitution calculated:

$m_g=\frac{m^{\′}}{V^{\′}}{V}_g---\left(1\right)$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g---\left(2\right)$

m _g(pg)--------during-----gas-liquid two-phase balance, be distributed in the quality of the hydrogen phosphide in the gas phase;

M ' is------quality of institute's phosphine containing in the gas appearance of-----preparation (pg);

V ' is----------volume of the gas appearance of----preparation (l);

V _g(l)------during-----gas-liquid two-phase balance, gaseous phase volume, V _g=20ml;

C (pg/l)--------the hydrogen phosphide mass concentration of-----water sample to be measured;

V _l(l)----------the volume of-----water sample to be measured;

C _l(pg/l)--------during----gas-liquid two-phase balance, be distributed in the mass concentration of hydrogen phosphide in the liquid phase;

R (J/ (Kmol))--ideal gas constant, R=8.314J/ (Kmol);

The molal weight of M (pg/mol)----hydrogen phosphide;

K (Pal/pg)----Henry's constant;

T (the K)------thermodynamic temperature of gas-liquid two-phase system when-----gas-liquid two-phase balancing method is extracted hydrogen phosphide;

Result of calculation is the hydrogen phosphide content of water sample to be measured.

Further, the computing method of the hydrogen phosphide mass concentration of water sample to be measured are following,

The water sample of adopting back direct projection 24h under sunshine, so that make the hydrogen phosphide quilt photodissociation fully in the water sample, draw the water sample of 30mL after photodissociation is handled then in the syringe of 50mL, the 20mL concentration known of reinjecting contains 10ng/m ³The high pure nitrogen of standard phosphine gas acutely shook several minutes up and down, made hydrogen phosphide reach balance at gas-liquid two-phase, calculated the amount m of hydrogen phosphide in the nitrogen subsequently _g

When hydrogen phosphide reaches balance in the nitrogen G&W, the quality m in gas phase _gCalculate:

(1) the conversion relation formula of standard phosphine gas concentration and peak area:

Peak area ÷ gas volume (ml)=graticule slope, wherein the graticule slope is tried to achieve by typical curve

(2) during the gas-liquid two-phase balance in gas phase the quality of phosphine gas

(3) Henry's constant K's tries to achieve as follows

Amount m because of hydrogen phosphide in the standard specimen _AlwaysKnown, thus after the balance in the water amount of hydrogen phosphide do

m _l=m _Always-m _g

Henry's law: under uniform temperature and equilibrium state, to be directly proportional with its mole fraction in solution be P=Kx to the partial pressure of volatile solutes in gas phase in the lean solution, and P is the partial pressure (Pa) of hydrogen phosphide in gas phase, and x is a mole fraction;

Also can be written as P=KC _l, C _lBe the equilibrium concentration (pg/L) of hydrogen phosphide in liquid phase.

In the formula $P=\frac{\mathrm{NRT}}{V_g}=\frac{m_g\mathrm{RT}}{M{V}_g}$

∴

The mass concentration C of hydrogen phosphide in the actual water sample:

$C=\frac{m_g+m_l}{V_l}=\frac{m_g+C_l{V}_l}{V_l}=\frac{m_g}{V_l}+C_l(\mathrm{pg}/L)$

In the formula, $C_l=\frac{P}{K}=\frac{m_g\mathrm{RT}}{M{V}_{g}K}$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{v_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g=(\frac{1}{30\×{10}^{-3}}+\frac{{10}^{-12}\×8.314\×298.15}{34\×20\×{10}^{-6}\×K})m_g(\mathrm{pg}/L)$

The relation of Henry's constant K and partition factor k:

P＝KC _l， $P=\frac{\mathrm{nRT}}{V_g}=\frac{m_g\mathrm{RT}}{M{V}_g}\×{10}^9=K\frac{m_l}{V_l}$

When hydrogen phosphide reached balance at gas-liquid two-phase, in the time of 25 ℃, the mass ratio k in gas phase and liquid phase did

$k=\frac{m_g}{m_l}=\frac{M{V}_g}{\mathrm{RT}{V}_l}\×K\×{10}^{-9}=\frac{34\×20\×{10}^{-9}}{8.314\×298.15\×30}\×K=0.01372K$

The calculating of Taihu Lake water sample Henry's constant

Table 1

Table 2

Henry's constant average 6.17011E-06, standard deviation 5.59448E-07, relative standard deviation 0.91%

Beneficial effect

The present invention has compared following obvious advantage with other technologies:

A, detectability are low.

This methods analyst 10～100mL gas appearance, its detection is limited to 0.1ng/m3, is enough to satisfy the requirement that trace hydrogen phosphide under most of condition is measured, and domesticly only can reach 0.001mg/m3 with class methods.

When B, gas chromatographic analysis, appearance time is short, and peak shape is obvious, and it is convenient to analyze.

Appearance time is generally at 2.2-2.6min, peak width 0.7s.

Embodiment

Embodiment one:

In certain scientific research project from Yancheng, Jiangsu section Huanghai Sea beach adopt water body example, adopt this method to measure phosphine concentration in the water sample.

Experimental apparatus and reagent:

Agilent 4890D gas chromatograph is equipped with thermionic nitrogen and phosphorous detector (NPD), and chromatographic column is to adopt the capillary column of Crosslinked 5%Ph Me Silicone (25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard); Six-way injection valve; The thermos cup of two 2L (making cold-trap); Liquid nitrogen (Nanjing University refrigeration experiment chamber); Standard P H3 gas (Nanjing special gas factory).

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃ of detector temperatures (280 ℃); Carrier gas (nitrogen) flow velocity is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23.

Accurately draw the 30mL water sample with the 50mL syringe, inject high pure nitrogen 20mL, acutely shake several minutes up and down to displace PH3 gas wherein.Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in.

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO2, H2O and H2S etc. and can produce the gas that disturbs measuring with testing sample injecting gas absorption tube; Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge from the gas vent position; Six-way injection valve is transformed into " on " position, more than the collection tube to 0 ℃ at a cold-trap place of heating, makes gaseous sample brought into No. two cold-traps and carry out enrichment once more by nitrogen carrier gas; The gas chromatograph of band nitrogen phosphorous detector detects gas appearance to be measured.After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak; Converse the quality of the gas to be measured institute phosphine containing of injection according to typical curve, utilize the formula that provides in this patent to calculate the concentration of hydrogen phosphide in the water sample to be measured again.

Experimental result is shown in table 3 precision experimental result, and this law relative standard deviation is 4.00%-4.71%.

Table 3 precision experimental result

Table 4 recovery of standard addition

Embodiment two:

Adopt from the Changjiang River in Jiangsu river bank in certain scientific research project water body example, adopt this method to measure phosphine concentration in the water sample.

Experimental apparatus and reagent:

Agilent 4890D gas chromatograph is equipped with thermionic nitrogen and phosphorous detector (NPD), and chromatographic column is to adopt the capillary column of Crosslinked 5%Ph Me Silicone (25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard); Six-way injection valve; The thermos cup of two 2L (making cold-trap); Liquid nitrogen (Nanjing University refrigeration experiment chamber); Standard P H3 gas (Nanjing special gas factory).

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃ of detector temperatures (280 ℃); Carrier gas (nitrogen) flow velocity is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23.

Accurately draw the 30mL water sample with the 50mL syringe, inject high pure nitrogen 20mL, acutely shake several minutes up and down to displace PH3 gas wherein.Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in.

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO2, H2O and H2S etc. and can produce the gas that disturbs measuring with testing sample injecting gas absorption tube; Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge the gas discharge outlet position; Six-way injection valve is transformed into " on " position, more than the collection tube to 0 ℃ at a cold-trap place of heating, makes gaseous sample brought into No. two cold-traps and carry out enrichment once more by nitrogen carrier gas; The gas chromatograph of band nitrogen phosphorous detector detects gas appearance to be measured.After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak; Converse the quality of the gas to be measured institute phosphine containing of injection according to typical curve, utilize the formula that provides in this patent to calculate the concentration of hydrogen phosphide in the water sample to be measured again.

Experimental result is shown in table 5 precision experimental result, and this law relative standard deviation is 4.71%-5.51%.

Table 5 precision experimental result

Table 6 recovery of standard addition

Embodiment three:

In certain scientific research project from Taihu Lake, Jiangsu Province water body example, adopt this method to measure the water sample phosphine concentration.

Experimental apparatus and reagent:

Agilent 4890D gas chromatograph is equipped with thermionic nitrogen and phosphorous detector (NPD), and chromatographic column is to adopt the capillary column of Crosslinked 5%Ph Me Silicone (25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard); Six-way injection valve; The thermos cup of two 2L (making cold-trap); Liquid nitrogen (Nanjing University refrigeration experiment chamber); Standard P H3 gas (Nanjing special gas factory).

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃ of detector temperatures (280 ℃); Carrier gas (nitrogen) flow velocity is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23.

Accurately draw the 30mL water sample with the 50mL syringe, inject high pure nitrogen 20mL, acutely shake several minutes up and down to displace phosphine gas wherein.Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in.

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO2, H2O and H2S etc. and can produce the gas that disturbs measuring with testing sample injecting gas absorption tube; Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate; Six-way injection valve is transformed into " on " position, more than the collection tube to 0 ℃ at a cold-trap place of heating, makes gaseous sample brought into No. two cold-traps and carry out enrichment once more by nitrogen carrier gas; The gas chromatograph of band nitrogen phosphorous detector detects gas appearance to be measured.After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak; Converse the quality of the gas to be measured institute phosphine containing of injection according to typical curve, utilize the formula that provides in this patent to calculate the concentration of hydrogen phosphide in the water sample to be measured again.

Experimental result is shown in table 7 precision experimental result, and this law relative standard deviation is 3.25%-5.50%.

Table 7 precision experimental result

Table 8 recovery of standard addition

What should explain at last is: above embodiment is only in order to explaining technical scheme of the present invention, but not to its restriction; Although with reference to previous embodiment the present invention has been carried out detailed explanation, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment put down in writing, and perhaps part technical characterictic wherein is equal to replacement; And these are revised or replacement, do not make the spirit and the scope of the essence disengaging various embodiments of the present invention technical scheme of relevant art scheme.

Claims (3)

1. a gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample, it is characterized in that concrete steps are following:

The establishment of A, phosphine gas cooling enrichment and GC/NPD pick-up unit

Cooling enrichment of assembling phosphine gas and GC/NPD pick-up unit; The testing equipment that requires is: Agilent 4890D gas chromatograph; Thermionic nitrogen and phosphorous detector (NPD) is housed; Chromatographic column is to adopt the capillary column of " 25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard " Crosslinked 5%Ph Me Silicone; Six-way injection valve; The thermos cup of two 2L is made cold-trap; Liquid nitrogen;

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃～280 ℃ of detector temperatures; The flow velocity of carrier gas---nitrogen is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23;

B, employing gas-liquid two-phase balancing method prepare gaseous sample

Accurately draw the 30mL water sample with the 50mL syringe; Inject high pure nitrogen 20mL then; Acutely shake 10～20 minutes up and down to displace phosphine gas wherein; Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in;

The pre-service of C, gaseous sample to be measured

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO testing sample injecting gas absorption tube ₂, H ₂O and H ₂S etc. can produce the gas that disturbs to measuring;

The first cold-trap enrichment of D, hydrogen phosphide

Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge from gas vent;

The secondary cold-trap enrichment of E, hydrogen phosphide

Six-way injection valve is transformed into " on " position, more than the collection tube to 0 of a cold-trap post of Fast Heating ℃, makes gaseous sample brought into No. two cold-traps fast and carry out enrichment once more by nitrogen carrier gas.

The gas chromatograph of F, band nitrogen phosphorous detector detects gas appearance to be measured

After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak;

G, drawing standard curve

Get the standard phosphine gas; Be diluted to the concentration of varying number level by volume with standard nitrogen, same subsequently concentration standard phosphine gas is got 5ml, 10ml, 20ml, 30ml, 40ml, 50ml respectively, and B to E operates set by step; Obtain characteristic peak area separately; The gas appearance institute phosphine containing quality of injecting is made typical curve to corresponding characteristic peak area, and fitting formula, obtain under this order of magnitude the reduction formula of institute's phosphine containing quality and character pair peak area in the gaseous sample;

H, data processing and numerical value convert:

In the characteristic peak area substitution fitting formula with testing sample, calculate the quality of institute's phosphine containing in the testing sample, subsequently the following formula of result of calculation substitution calculated:

$m_g=\frac{m^{\′}}{V^{\′}}{V}_g---\left(1\right)$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g---\left(2\right)$

m _g(pg)--------during-----gas-liquid two-phase balance, be distributed in the quality of the hydrogen phosphide in the gas phase;

M ' is------quality of institute's phosphine containing in the gas appearance of-----preparation (pg);

V ' is----------volume of the gas appearance of----preparation (l);

V _g(l)------during-----gas-liquid two-phase balance, gaseous phase volume, V _g=20ml;

C (pg/l)--------the hydrogen phosphide mass concentration of-----water sample to be measured;

V _l(l)----------the volume of-----water sample to be measured;

C _l(pg/l)--------during----gas-liquid two-phase balance, be distributed in the mass concentration of hydrogen phosphide in the liquid phase;

R (J/ (Kmol))--ideal gas constant, R=8.314J/ (Kmol);

The molal weight of M (pg/mol)----hydrogen phosphide;

K (Pal/pg)----Henry's constant;

T (the K)------thermodynamic temperature of gas-liquid two-phase system when-----gas-liquid two-phase balancing method is extracted hydrogen phosphide;

Result of calculation is the hydrogen phosphide content of water sample to be measured.

2. a gas chromatography cooperates the preceding twice cold-trap concentration method of post to detect the method for trace phosphine gas in the water sample, it is characterized in that concrete steps are following:

The establishment of A, phosphine gas cooling enrichment and GC/NPD pick-up unit

Cooling enrichment of assembling phosphine gas and GC/NPD pick-up unit; The testing equipment that requires is: Agilent 4890D gas chromatograph; Thermionic nitrogen and phosphorous detector (NPD) is housed; Chromatographic column is to adopt the capillary column of " 25m * 0.2mm * 0.33 μ m film thickness, Hewlett Packard " Crosslinked 5%Ph Me Silicone; Six-way injection valve; The thermos cup of two 2L is made cold-trap; Liquid nitrogen;

Chromatographic condition: 40 ℃ of column temperatures; 220 ℃～280 ℃ of detector temperatures; The flow velocity of carrier gas---nitrogen is 2mL/min; Air velocity is 120mL/min; Hydrogen flow rate 3～45mL/min; The flow velocity of auxiliary gas nitrogen is 30mL/min; The activation voltage of detecting device is controlled at about 450mV, and activation signal is about 23;

B, employing gas-liquid two-phase balancing method prepare gaseous sample

Water sample to be measured adds the 1.2g composite flocculation agent and carries out preliminary sedimentation, and the component of said composite flocculation agent is zeyssatite and aluminium polychloride (PAC), and the weight ratio of said zeyssatite and aluminium polychloride (PAC) is a zeyssatite: aluminium polychloride is 40-100: 10-25; Accurately draw the water sample of 30mL with the 50mL syringe through precipitation process; Inject high pure nitrogen 20mL then; Acutely shake 10～20 minutes up and down to displace phosphine gas wherein; Draw the gas certain volume behind the exchange equilibrium, with the gaseous sample lucifuge be stored in to hydrogen phosphide do not absorb and the sealed air pocket of adsorbing in.

The pre-service of C, gaseous sample to be measured

When treating that the interior temperature of cold-trap is reduced to below-60 ℃, six-way injection valve is transformed into " off " position,, removes CO testing sample injecting gas absorption tube ₂, H ₂O and H ₂S etc. can produce the gas that disturbs to measuring;

The first cold-trap enrichment of D, hydrogen phosphide

Gaseous sample to be measured is injected a cold-trap carry out first enrichment, remove the lower gas of boiling points such as hydrocarbon, oxygen, nitrogen and separate, discharge from gas vent;

The secondary cold-trap enrichment of E, hydrogen phosphide

Six-way injection valve is transformed into " on " position, more than the collection tube to 0 of a cold-trap post of Fast Heating ℃, makes gaseous sample brought into No. two cold-traps fast and carry out enrichment once more by nitrogen carrier gas;

The gas chromatograph of F, band nitrogen phosphorous detector detects gas appearance to be measured

After the enrichment of hydrogen phosphide secondary, testing sample gets into and to get into gas chromatograph through chromatographic column and detected by nitrogen phosphorous detector (NPD), obtains time-response curve, can read the characteristic peak of hydrogen phosphide according to retention time, notes the area of characteristic peak;

G, drawing standard curve

Get the standard phosphine gas; Be diluted to the concentration of varying number level by volume with standard nitrogen, same subsequently concentration standard phosphine gas is got 5ml, 10ml, 20ml, 30ml, 40ml, 50ml respectively, and B to E operates set by step; Obtain characteristic peak area separately; The gas appearance institute phosphine containing quality of injecting is made typical curve to corresponding characteristic peak area, and fitting formula, obtain under this order of magnitude the reduction formula of institute's phosphine containing quality and character pair peak area in the gaseous sample;

H, data processing and numerical value convert:

In the characteristic peak area substitution fitting formula with testing sample, calculate the quality of institute's phosphine containing in the testing sample, subsequently the following formula of result of calculation substitution calculated:

$m_g=\frac{m^{\′}}{V^{\′}}{V}_g---\left(1\right)$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g---\left(2\right)$

m _g(pg)--------during-----gas-liquid two-phase balance, be distributed in the quality of the hydrogen phosphide in the gas phase;

M ' is------quality of institute's phosphine containing in the gas appearance of-----preparation (pg);

V ' is----------volume of the gas appearance of----preparation (l);

V _g(l)------during-----gas-liquid two-phase balance, gaseous phase volume, V _g=20ml;

C (pg/l)--------the hydrogen phosphide mass concentration of-----water sample to be measured;

V _l(l)----------the volume of-----water sample to be measured;

C _l(pg/l)--------during----gas-liquid two-phase balance, be distributed in the mass concentration of hydrogen phosphide in the liquid phase;

R (J/ (Kmol))--ideal gas constant, R=8.314J/ (Kmol);

The molal weight of M (pg/mol)----hydrogen phosphide;

K (Pal/pg)----Henry's constant;

T (K)--------thermodynamic temperature of gas-liquid two-phase system when----gas-liquid two-phase balancing method is extracted hydrogen phosphide;

Result of calculation is the hydrogen phosphide content of water sample to be measured.

3. cooperate before the post twice cold-trap concentration method to detect the method for trace phosphine gas in the water sample according to the described a kind of gas chromatography of claim 1-2, it is characterized in that:

The computing method of the hydrogen phosphide mass concentration of water sample to be measured are following,

The water sample of adopting back direct projection 24h under sunshine, so that make the hydrogen phosphide quilt photodissociation fully in the water sample, draw the water sample of 30mL after photodissociation is handled then in the syringe of 50mL, the 20mL concentration known of reinjecting contains 10ng/m ³The high pure nitrogen of standard phosphine gas acutely shook several minutes up and down, made hydrogen phosphide reach balance at gas-liquid two-phase, calculated the amount m of hydrogen phosphide in the nitrogen subsequently _g

When hydrogen phosphide reaches balance in the nitrogen G&W, the quality m in gas phase _gCalculate:

(1) the conversion relation formula of standard phosphine gas concentration and peak area:

Peak area ÷ gas volume (ml)=graticule slope, wherein the graticule slope is tried to achieve by typical curve

(2) during the gas-liquid two-phase balance in gas phase the quality of phosphine gas

(3) Henry's constant K's tries to achieve as follows

Amount m because of hydrogen phosphide in the standard specimen _AlwaysKnown, thus after the balance in the water amount of hydrogen phosphide do

m _l=m _Always-m _g

Henry's law: under uniform temperature and equilibrium state, to be directly proportional with its mole fraction in solution be P=Kx to the partial pressure of volatile solutes in gas phase in the lean solution, and P is the partial pressure (Pa) of hydrogen phosphide in gas phase, and x is a mole fraction;

Also can be written as P=KC _l, C _lBe the equilibrium concentration (pg/L) of hydrogen phosphide in liquid phase.

In the formula $P=\frac{\mathrm{NRT}}{V_g}=\frac{m_g\mathrm{RT}}{M{V}_g}$

∴

The mass concentration C of hydrogen phosphide in the actual water sample:

$C=\frac{m_g+m_l}{V_l}=\frac{m_g+C_l{V}_l}{V_l}=\frac{m_g}{V_l}+C_l(\mathrm{pg}/L)$

In the formula, $C_l=\frac{P}{K}=\frac{m_g\mathrm{RT}}{M{V}_{g}K}$

$C=\frac{m_g}{V_l}+C_l=\frac{m_g}{V_l}+\frac{m_g\mathrm{RT}}{M{V}_{g}K}=(\frac{1}{V_l}+\frac{\mathrm{RT}}{M{V}_{g}K})m_g=(\frac{1}{30\×{10}^{-3}}+\frac{{10}^{-12}\×8.314\×298.15}{34\×20\×{10}^{-6}\×K})m_g(\mathrm{pg}/L)$

The relation of Henry's constant K and partition factor k:

P＝KC _l， $P=\frac{\mathrm{nRT}}{V_g}=\frac{m_g\mathrm{RT}}{M{V}_g}\×{10}^9=K\frac{m_l}{V_l}$

When hydrogen phosphide reached balance at gas-liquid two-phase, in the time of 25 ℃, the mass ratio k in gas phase and liquid phase did

$k=\frac{m_g}{m_l}=\frac{M{V}_g}{\mathrm{RT}{V}_l}\×K\×{10}^{-9}=\frac{34\×20\×{10}^{-9}}{8.314\×298.15\×30}\×K=0.01372K.$