HJ 592-2010Water quality. Determination of nitrobenzene-compounds by gas chromatography (English PDF)

5.1 Sample collection and preservation

Collect 1 000 ml of sample in the sampling bottle. If the water sample cannot be measured within 24 h, add concentrated sulfuric acid (3.1) to adjust pH<=3. kind the product must be extracted within 7 days, and the extract should be stored in the dark at 4 ° C. It should be analyzed within 30 days.

5.2 Preparation of samples

5.2.1 Extraction of nitrobenzene compounds (except 2,4,6-trinitrobenzoic acid)

Measure 500 ml of sample (when the content is high, take as little as possible) in a separatory funnel, add 25 ml of dichloromethane (3.2), shake for 3 min.

(Exhaust 2~3 times), after standing for 3 min, collect the lower extract in a triangular flask; repeat the extraction once and combine the extracts. Extract After dehydration of anhydrous sodium sulfate (3.4), the volume was adjusted to 1 ml by a rotary evaporator and a nitrogen blower to be analyzed. After extracting twice with dichloromethane the aqueous phase was transferred to a 1 000 ml Erlenmeyer flask.

5.2.2 Extraction of 2,4,6-trinitrobenzoic acid

The above 1 000 ml Erlenmeyer flask was placed in an electric furnace or a hot plate and heated to boil for 20 min, and then cooled to room temperature. Repeat 5.2.1 Procedure, 2,4,6-trinitrobenzoic acid to be determined.

Note 1. The experimental procedure should be operated in a fume hood.

Note 2. During the boiling process of step 5.2.2, the heating temperature should not be too high to avoid violent boiling; when the water sample is less than 500 ml, the water should be kept during heating.

The amount is not less than 100 ml.

Note 3. For high-quality sewage and wastewater samples, water samples should be taken less or directly without concentration. Determination of samples affected by chromatographic analysis, water samples it should be cleaned after taking it. See Appendix A for the operation steps.

6.1 Chromatographic Analysis Reference Conditions

Column temperature. 60 ° C for 4 min, 20/min ° C to 220 ° C, for 3 min; detector temperature. 250 ° C; vaporization Room temperature. 230 ° C; carrier gas flow rate. 1 ml/min; hydrogen flow. 30 ml/min; air flow. 400 ml/min; tail gas flow. 20 Ml/min; injection method. splitless injection, split 0.5 min after injection, split ratio is 30.1; injection volume. 1.0 µl.

6.2 Calibration

6.2.1 Drawing of standard curve

Diluting each nitrobenzene compound standard solution (3.5) with methylene chloride (3.2) to a mass concentration of 5, 10, 20, 40, 60 and 120 µg/ml mixed standard series, respectively, 1.0 µl of the standard series solution is injected into the gas chromatograph inlet, according to the quality of each component A standard curve is drawn for the degree and peak area (or peak height).

6.2.2 Standard chromatogram

A reference chromatogram of each nitrobenzene compound is shown in Figure 1.

2 4 6 8 10 min

1-dichloromethane; 2-nitrobenzene; 3-o-nitrotoluene; 4-m-nitrotoluene; 5-p-nitrotoluene; 6-2,6-dinitrotoluene;

7-2,4-dinitrotoluene; 8-1,3,5-trinitrobenzene; 9-2,4,6-trinitrotoluene

Figure 1 Standard chromatogram of nitrobenzene compounds

6.3 Determination

A 1.0 µl sample (5.2) was injected into the gas chromatograph using a microsyringe and assayed under the same chromatographic conditions as the standard curve.

Record the retention time and peak area (or peak height) of the chromatographic peak.

6.4 Blank test

While the sample is being analyzed, a blank test should be performed. That is, the test water is used instead of the water sample, and the analysis is performed in the same manner as the sample measurement.

7.1 Calculation of results

7.1.1 Calculation of results for nitrobenzene compounds (except 2,4,6-trinitrobenzoic acid)

The components of the nitrobenzene compound in the sample (except 2,4,6-trinitrobenzoic acid) were calculated according to the formula (1).

rhorho ×= standard (1) where. irho - mass concentration of a certain nitrobenzene compound in the sample, mg/L;

rho standard--the mass concentration calculated from the standard curve, mg/L;

1V - the volume of the volume after concentration of the extract, ml;

V -- water sample volume, ml.

7.1.2 Calculation of the results of 2,4,6-trinitrobenzoic acid

The 2,4,6-trinitrobenzoic acid in the sample was calculated according to the formula (2).

1 1.21V

rhorho × ×= standard (2) where. rho--the mass concentration of 2,4,6-trinitrobenzoic acid in the sample, mg/L;

rho standard--the mass concentration of 1,3,5-trinitrobenzene calculated from the standard curve, mg/L;

1V - the volume of the volume after concentration of the extract, ml;

V - water sample volume, ml;

The ratio of the relative molecular mass of 1.21--2,4,6-trinitrobenzoic acid to 1,3,5-trinitrobenzene.

7.2 Results representation

When the sample content is less than 1 mg/L, the result is retained to the third decimal place; when the sample content is greater than or equal to 1 mg/L, the result is guaranteed.

Leave three valid numbers.

8.1 Precision

Five laboratories tested uniform samples containing nitrobenzene compounds at concentrations of 0.020 mg/L and 0.100 mg/L.

The relative standard deviations in the experimental room were. 2.1% to 9.4%, 0.55% to 6.2%;

The relative standard deviations between laboratories are. 2.5% to 9.8%, 4.0% to 8.8%;

The repeatability limit r is. 0.002 ~ 0.003 mg/L, 0.007 ~ 0.011 mg/L;

Reproducibility limits R are. 0.002 to 0.006 mg/L, and 0.015 to 0.026 mg/L, respectively.

For detailed summary data on the specific target components, see Appendix B.

8.2 Accuracy

Sampling analysis of uniform domestic sewage samples containing nitrobenzene compounds with a concentration of 0.035 mg/L in 5 laboratories (scaling amount is 50.0 µg).

Standard recovery rate. 81.2% ~ 94.0%;

The final value of the spiked recovery was 81.2%±16.8%~94.0%±17.6%.

For a summary of the accuracy of the specific target components, see Appendix B.

9.1 Qualitative analysis

A retention time window of t ± 3S should be established prior to sample analysis. t is the average value of the retention time of each concentration level of the reference material at the initial calibration, S is the standard deviation of the retention time of each reference material at the initial calibration. When the sample is analyzed, the target compound retention time should be in the retention time window.

In the mouth.

9.2 Blank test

Make at least one blank sample and blank spiked sample for each batch of samples. The blank sample is analyzed and measured using the same method as the actual sample.

The compound concentration should be below the detection limit. The recovery rate of the blank sample should be controlled at 80% to 120%.

9.3 The correlation curve of the standard curve should be greater than or equal to 0.995, otherwise the standard curve should be redrawn.

9.4 Intermediate concentration test

The intermediate concentration test shall be carried out during sample analysis. The relative deviation between the measured value of the intermediate concentration and the value of the curve shall be less than or equal to 15%, otherwise A new standard curve should be established.

9.5 Matrix addition

At least one matrix spiked sample shall be prepared for each batch of samples. The matrix spiked sample and the actual sample shall be analyzed and determined by the same method.

The recovery rate should be controlled at 70% to 130%.

Appendix A

(normative appendix) Sample purification A.1 Instruments and equipment A.1.1 Column. 300 mm (column length) × 10 mm (inner diameter) glass column with a coarse-pored glass core and a Teflon piston at the bottom.

A.1.2 muffle furnace.

A.1.3 Oven.

A.1.4 Dryer.

A.2 Reagents and materials A.2.1 n-Hexane (C6H14). pure by liquid chromatography.

A.2.2 Acetone (C3H6O). Pure by liquid chromatography.

A.2.3 anhydrous sodium sulfate (Na2SO4). burn in a muffle furnace at 350 ° C for 4 h before use, cool to room temperature, and put into a glass bottle for use.

A.2.4 Silica-magnesium type adsorbent. for chromatography (60-100 mesh), purchase 677 °C activated product, stored in a glass stopper or belt with a grinding A screw-covered glass container lined with a PTFE mat.

Activation of the silica-magnesium type adsorbent. the silicon-magnesium-type adsorbent is placed in a large porcelain crucible and spread out, and the upper part of the porcelain crucible is covered with aluminum foil, and the crucible is placed.

Into the oven, dry at 130 ° C for 16 h, then place the silica-magnesium adsorbent in a desiccator to cool to room temperature, then install the sealed glass Waiting for use in the bottle.

A.3 Purification step A.3.1 Packing column 10 g of the activated silica-magnesium-type adsorbent (A.2.4) was placed in a 50 ml beaker, and an appropriate amount of dichloromethane-n-hexane (1 9) was added.

A silicon magnesium type adsorbent is prepared as a suspension. Then pour the suspension into the column (A.1.1) and tap the column to fill the adsorbent.

Then add 1 cm of anhydrous sodium sulfate (A.2.3) to the top and adjust the elution rate to about 2 ml/min.

A.3.2 Solvent replacement the dichloromethane extract (5.2) was concentrated to 1 ml in a concentrate bottle, 4 ml of n-hexane was added to the concentrate bottle, and then concentrated to 1 ml.

The solvent was replaced with n-hexane.

A.3.3 Purification

When the solvent in the column is released until the sodium sulfate layer is exposed, the extract (A.3.2) after replacing the solvent is transferred to the column, Rinse the concentrate bottle with 30 ml of dichloromethane-n-hexane (1 9), transfer the solution to the column, and collect the eluate until the sulfuric acid is just exposed.

Sodium layer. The fraction of the eluent is eluent I, and the compound contained is m-nitrotoluene and p-nitrotoluene.

Then, the column was eluted with 30 ml of acetone-dichloromethane (1 9), and the eluate was collected. The partial eluent is eluent II, containing the compounds are nitrobenzene, o-nitrotoluene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, 1,3,5-trinitrobenzene, 2,4,6-trinitrate Base armor benzene.

A.3.4 If the components of eluent I and eluent II need to be determined simultaneously, combine the eluent I and the eluent II, and concentrate to 1 ml.

Analysis. Otherwise, eluent I and eluent II to 1 ml should be separately concentrated for analysis.

Appendix B

(informative appendix) Method precision and accuracy Schedule B.1 Precision measured by five laboratories Component Name Average/(mg/L) Relative standard in the experimental room deviation/% Relative standard between laboratories deviation/% Repeatability limit r/(mg/L) Reproducibility limit R/(mg/L) Nitrobenzene 0.018 2.6~9.4 9.0 0.003 0.005 0.101 1.9~5.0 6.7 0.011 0.021 O-nitrotoluene 0.019 2.9~9.2 9.5 0.003 0.006 0.102 1.2~5.4 8.4 0.010 0.026 M-nitrotoluene 0.019 2.1~9.2 8.3 0.003 0.005 0.100 0.75~3.9 6.2 0.008 0.019 P-nitrotoluene 0.019 2.2~7.7 4.8 0.003 0.004 0.101 1.9~4.4 7.9 0.009 0.024 2,4-dinitrotoluene 0.019 2.8~5.6 7.2 0.002 0.004 0.100 0.55~4.4 8.8 0.007 0.026 2,6-dinitrotoluene 0.019 2.5~8.3 9.0 0.003 0.006 0.101 0.97~5.1 7.8 0.010 0.024 2,4,6-trinitrotoluene 0.019 2.8~7.7 5.3 0.003 0.004 0.098 0.55~3.8 8.5 0.007 0.024 1,3,5-trinitrobenzene 0.019 3.0~7.5 9.8 0.003 0.006 0.101 1.9~4.2 6.0 0.010 0.019 Trinitrobenzoic acid 0.018 2.9~6.2 2.5 0.002 0.002 0.098 1.5~6.2 4.0 0.011 0.015 Schedule B.2 Accuracy of five laboratory measurements Component name plus amount/µg Average recovery /Gg Average spike recovery rate /Spike recovery rate final value /Nitrobenzene 50.0 44.4 88.8 88.8±6.1 O-nitrotoluene 50.0 47.0 94.0 94.0±17.6 m-Nitrotoluene 50.0 45.0 90.0 90.0±3.9 p-Nitrotoluene 50.0 46.4 92.8 92.8±6.0 2,4-dinitrotoluene 50.0 46.7 93.4 93.4±5.7 2,6-dinitrotoluene 50.0 44.2 88.4 88.4±11.0 2,4,6-trinitrotoluene 50.0 45.2 90.4 90.4±14.7 1,3,5-trinitrobenzene 50.0 42.2 84.4 84.4±16.4 Trinitrobenzoic acid 50.0 40.6 81.2 81.2±16.8