CN102183393A - Soil extracting and measuring method of anion surfactant - Google Patents

Abstract

The invention relates to a soil extracting and measuring method of an anion surfactant, which is characterized by comprising the following steps: firstly, using an ethanol water solution to extract the LAS (Laurylbenzenesulfonic Acidsodium Salt) in the soil; and measuring the total content of the LAS by utilizing a water quality anion surfactant methylene blue spectrophotometry in the national standard method GB 7494-87. The invention establishes a method for measuring the LAS in the soil. The method provided by the invention is stable; the extracting course is convenient and rapid; the method and the water quality anion surfactant methylene blue spectrophotometry can measure the LAS content in the soil under the same system; and the method has the comparability with the water quality LAS on the measuring result. In the method provided by the invention, the accuracy is 1.89%; the recovery rate is between 91.65% and97.04%; the detection limit is 0.020mg/kg; the accuracy and the detection limit are superior to an Azure A spectrophotometry, and the recovery rate is equal to the Azure A spectrophotometry; and the method for measuring the LAS in the soil is suitable and feasible.

Description

A kind of anionic surfactant soil extract and assay method

Technical field

The invention belongs to anionic surfactant (LAS) total amount determination techniques field, be specifically related to a kind of anionic surfactant soil extract and assay method, promptly extract LAS in the soil, and measure the total amount of LAS in the soil in conjunction with the methylene blue spectrophotometric method with ethanolic solution.

Background technology

Washing powder etc. contain the life that the synthetic detergent product has greatly made things convenient for people, and are also very extensive in the use of industrial surfactant.But the sewage emissions that contains surfactant causes water quality deterioration, soil pollution, even causes biological damage, has caused people's extensive concern.Therefore, need be to monitoring, analysis and the Rapid identification of anionic surfactant in the environment water.At present, the a plurality of countries that comprise China adopt LAS total amount in the methylene blue spectrophotometry water environment, its cardinal principle is, LAS and methylene blue reaction in water solution system, generate blue methylene blue active substance (MBAS), obtain light absorption value in 652nm wavelength mensuration behind the chloroform extraction.LAS has the report that adopts reddish black A spectrophotometry in the soil at present, but extraction and the detection of LAS in the soil also do not had effective standard method.

Summary of the invention

The purpose of this invention is to provide a kind of anionic surfactant soil extract and assay method, when promptly determining effectively to extract soil LAS method, make the result of the total quantitative determination of soil LAS and GB/T 7494-87 " water quality anionic surfactant methylene blue spectrophotometric method " the total quantity measuring method of described LAS and result have certain comparability, LAS total amount in the environment can be measured, to remedy the deficiencies in the prior art under same system.

Primary and foremost purpose of the present invention provides a kind of anionic surfactant soil extract and assay method, it is characterized in that using ethanol water to extract LAS in the soil.

Method of the present invention specifically is to soak pedotheque with 40～95% ethanol waters, and LAS is extracted in vibration under 10～60 ℃ of temperature.

The ethanol water of above-mentioned ethanol water preferred 70%.Wherein the mass volume ratio g/mL of pedotheque and ethanol water is preferably 1: 2.

Preferred 45 ℃ of above-mentioned extraction temperature, extraction time is 2h.

Sample after the extraction carries out the mensuration of LAS with national standard method GB 7494-87 " water quality anionic surfactant methylene blue spectrophotometric method " after diluting.

The present invention has set up a kind of method of measuring LAS in the soil, and the inventive method is stable, and leaching process is convenient, can measure the content of soil LAS with water quality methylene blue spectrophotometric method under same system, and have comparability with water quality LAS on measurement result.The inventive method precision is 1.89%, and the recovery detects and is limited to 0.020mg/kg between 91.65～97.04%.Precision, detection limit all are better than the precision (2.53%～7.36% of reddish black A spectrophotometric method; Detection limit 0.100mg/kg), the recovery is (96% ± 5.42%) quite, is the method for a kind of suitable feasible mensuration soil LAS.

Description of drawings

Fig. 1: the extraction agent proportioning is to the influence of experimental result in the inventive method.

Fig. 2: anionic surfactant of the present invention (LAS) typical curve

Embodiment

Below to the invention the concrete steps of specifically drawing up a plan for and inventing be described.Wherein the soil anionic surfactant is write a Chinese character in simplified form with LAS, and neopelex is called for short with SDBS.

Employed solution formula of method of the present invention and preparation method are as follows:

1, LAS standard solution (in SDBS) (GBW (E) 081639,1000 μ g/mL), dilution is formulated as standard and uses solution (10.0 μ g/mL).

2, methylene blue solution (50mg/L):

In the 1000mL beaker, add 500ml water, add 50g sodium dihydrogen phosphate (NaH ₂PO ₄H ₂O), stirring slowly adds 6.8mL sulfuric acid (H down ₂SO4, ρ=1.84g/mL), add 50mg methylene blue (C ₁₆H ₁₈N ₃ClS3H ₂O) indicator, stirring and dissolving adds water to 1000mL, mixing.Changing brown reagent bottle over to preserves.

3, cleansing solution:

In the 1000mL beaker, add 500mL water, add 50g sodium dihydrogen phosphate (NaH ₂PO ₄H ₂O), stirring slowly adds 6.8mL sulfuric acid (H down ₂SO4, ρ=1.84g/mL), stirring and dissolving.Add water to 1000mL, mixing.

4, instructions phenolphthalein solution:

Take by weighing 0.25g phenolphthalein (C ₂₀H ₁₄O ₄) indicator, be dissolved in 40mL absolute ethyl alcohol (C ₂H ₅OH), add water 10mL, mixing.

5, sodium hydroxide solution (NaOH=1mol/L):

It is water-soluble and rare to 250mL to take by weighing 10.0g NaOH (NaOH), mixes to be stored in the polyethylene bottle.

6, sulfuric acid (H ₂SO ₄, the solution of ρ=1.84g/mL): c H ₂SO ₄=0.5mol/L (13.5ml sulfuric acid is joined 500ml).

One, the solution formulation of extracting method

Soil LAS extraction efficiency is mainly relevant with duration of oscillation with extraction agent ethanol water proportioning, extraction agent consumption (being the ratio of pedotheque and extraction agent), bath temperature, therefore above-mentioned four factors being set is extraction conditions, each extraction conditions is provided with 4 levels, and is as shown in table 1.Suppose non-interaction action between each factor, adopt L ₁₆(4 ⁵) orthogonal arrage carries out orthogonal test, test condition is optimized.

Table 1 experiment condition and being horizontally disposed with

Gather sewage treatment plant's anaerobic sludge and Liaohe River reed wetland soil, be mixed with the pedotheque that condition test is used by a certain percentage.Extract according to the listed condition of table 1 respectively then, adopt the method (the .GB/T 7494-1987. of State Environmental Protection Administration water quality anionic surfactant is measured the methylenum careuleum spectrophotometric method) of LAS total amount in the methylene blue spectrophotometry water environment to measure content again.Determine optimum extraction condition according to measurement result at last.

Test of table 2 quadrature analysis and range analysis be table as a result

Carry out the extreme difference such as the table 2 and shown in Figure 1 of Orthogonal experiment results and different factors according to table 1.Its extreme difference maximum of factor that the level of factor has the greatest impact to test findings, this factor is main factor.By extreme difference R (duration of oscillation)＞R (extraction agent consumption)＞R (extraction agent proportioning)＞R (extraction temperature), the importance that obtains each factor is followed successively by: duration of oscillation, extraction agent consumption, extraction agent proportioning and extraction temperature.By empty row extreme difference all less than each factor extreme difference, so non-interaction action between above-mentioned each factor.

Select the arithmetic mean value K1 of each factor, K2, K3, the level of maximal value correspondence among the K4 is as the top condition of this factor.Along with the rising of bath temperature, therefore arithmetic mean value maximum when reaching 45 ℃ extracts the maximum extracted quality that can obtain LAS under the temperature at 45 ℃; Extraction agent consumption and extraction time, the maximum extracted quality of acquisition LAS under 20mL extraction agent consumption and the condition of 2 hour extraction time respectively.Orthogonal test analysis shows do not have reciprocation between each factor, so experimentize with regard to extraction agent proportioning and the relation of extracting quality, increases progressively the ethanolic solution that different proportionings are set by 10% between 20-80%.Shown in the experimental result accompanying drawing 1, reached the maximum LAS of acquisition maximum extracted quality at 70% o'clock.

In sum, formulating the preferred plan of extracting LAS in the 10g soil is: the extraction agent proportioning is 70%, and the extraction agent consumption is 20mL, and extracting temperature is 45 ℃, and extraction time is 2 hours.

Two, the concrete steps of typical curve foundation

At first the methylenum careuleum spectrophotometric method of measuring with reference to the GB/T 7494-1987 of State Environmental Protection Administration water quality anionic surfactant is set up typical curve, and concrete grammar is as follows:

(1) LAS standard solution (GBW (E) 081629,1000 μ g/mL) is diluted successively and constant volume, obtain 0.000,0.050,0.100,0.200,0.300,0.500 and the 1.000mg/L standard series, change the separating funnel of 6 250mL respectively over to.

(2) add 10mL sodium chloride solution and 1 instructions phenolphthalein solution, first dropping sodium solution drips sulfuric acid solution to redness again and just takes off to just showing red;

(3) adding 10mL concentration is the methylene blue solution mixing of 50mg/L, adds the 10mL chloroform again, and jolting 30s leaves standstill;

(4) after the layering lower floor's extract immigration is equipped with in the 125mL separating funnel of 50mL cleansing solution;

(5) repeat (2)-(4) step 1 time.

(6) jolting separating funnel 30s puts into the 25mL color comparison tube with lower floor's extract behind the standing demix;

(7) add 5mL chloroform concussion extraction again, emit chloroform extraction liquid behind the standing demix and incorporate color comparison tube into, add chloroform to 25mL, mixing;

(8) be the reference zeroing with the chloroform, read blank light absorption value A ₀, with the light absorption value Ai of 1cm cuvette at 652nm wavelength place mensuration extract.

(9) according to the Ai value of variable concentrations LAS, set up typical curve, as shown in Figure 2

The concentration that typical curve of setting up and related coefficient just can be used for analyzing soil LAS.Carry out the mensuration of sample then:

(10) after sample thawed, 105 ℃ (± 1 ℃) oven dry was fully ground the back and is crossed 200 order metallic screens.

(11) get the 10.000g pedotheque and move in the 50mL centrifuge tube, add mixed extract (70%) 20mL of ethanol and distilled water, 45 ° of vibrations of constant temperature water bath 2h.

(12) centrifugal 20min under the 4000r/min condition gets supernatant and uses the distilled water constant volume to 25mL, and this is the sample storing solution.

(13) pipette 5mL sample storing solution, to 100mL, use liquid stand-by as sample with the distilled water constant volume.

(14) according to experimental procedure 1) in (2)-(8) measure pedotheque.

(15) calculate pedotheque LAS content according to formula.Computing formula is:

$W_{\mathrm{LAS}}=\frac{\frac{(A_W-A_0)-b}{a}\×100\mathrm{mL}\×5\×1000}{\frac{M}{1-W_{H_{2}O}}}$

In the formula: Aw---the absorbance of sample;

A ₀---the absorbance of blank sample;

The slope of a---calibrating curve equation is seen accompanying drawing;

The intercept of b---calibrating curve equation is seen accompanying drawing;

M---the amount of taking by weighing of sample is got 10g;

W _LAS---anionic surfactant concentration, mg/kg

---the water percentage of air-dry sample, %

Embodiment 1:

Select for use the mixed soil sample that method of the present invention is verified, to prove the reliability of its use.

1) pedotheque preparation: get sewage treatment plant's anaerobic sludge and mix by a certain percentage with collection soil.

2) extraction of LAS in the sample

Carry out the extraction and determination and the calculating of sample according to " solution formulation of extracting method ", promptly get the 10g pedotheque, extract with 70% ethanol water, the extraction agent consumption is 20mL, and promptly wherein the mass volume ratio g/mL of pedotheque and ethanol water is 1: 2; Extracting temperature is 45 ℃, and extraction time is 2 hours.

The concrete steps that the methylenum careuleum spectrophotometric method that the detection method of the LAS concentration after the extraction is measured with the GB/T 7494-1987 of State Environmental Protection Administration water quality anionic surfactant, concrete steps see two, typical curve is set up.

3) inventive method certificate authenticity

Mixed soil sample with high, medium and low three kinds of content carries out precision experiment, 5 parallel samples of every group of sample determination respectively.Experimental result sees Table 3, this method absolute error (S) of (mean value is 3.037mg/kg) under the lower content level is 5.89%, relative standard deviation (RSD) is 1.94%, the absolute error (S) of (mean value is 16.336mg/kg) is 3.85% under the high level level, and relative standard deviation (RSD) is 0.24%.Standard method requires the experimental technique relative standard deviation to be no more than 2.3% among the GB GB 7494-87, and the maximum relative standard deviation of this experiment is 1.94%, illustrates that this analysis method precision is better than national standard.

Table 3 precision experimental result

Respectively under high, medium and low three concentration gradients, the standard that adds certain volume is used liquid (100.0mg/L), and making quality behind the mark-on is 0.5～2 times of original quality measurement, and every group is provided with three parallel samples, carries out the recovery of standard addition test.Measurement result sees Table 4, and recovery of standard addition is between 91.65～97.04% under the different content.

Table 4 recovery of standard addition experimental result

Calculating instrument according to typical curve detects and is limited to 0.0004mg/L.Calculate by soil sample amount 10g, this method is 0.020mg/kg to the rising limit of LAS in the soil.

This analysis method and GB 7494-87 " water quality anionic surfactant methylene blue spectrophotometric method " can measure LAS total amount in the environment under same system, what make LAS total amount measurement result in water body and soil and sediment environment has consistance and a comparability.

Claims (8)

1. anionic surfactant LAS soil extract method is characterized in that described extracting method is to use ethanol water to extract LAS in the soil.

2. extracting method as claimed in claim 1, the mass volume ratio g/ml that it is characterized in that above-mentioned soil and ethanol water is 1: 2.

3. extracting method as claimed in claim 1 is characterized in that above-mentioned extracting method is to extract under the temperature to vibrate with ethanol water at 10～60 ℃ to extract LAS in the soil.

4. as each described extracting method in the claim 1～3, it is characterized in that above-mentioned ethanol water concentration is 40～95%.

5. extracting method as claimed in claim 4 is characterized in that above-mentioned ethanol water concentration is 70%.

6. extracting method as claimed in claim 3 is characterized in that above-mentioned extraction temperature is 45 ℃.

7. extracting method as claimed in claim 3 is characterized in that the time that above-mentioned vibration is extracted is 2h.

8. adopt the LAS in the soil that claim 1 extracting method extracts, carry out the mensuration of LAS with national standard method GB 7494-87 water quality anionic surfactant methylene blue spectrophotometric method.

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