HJ 754-2015Water quality. Determination of atrazine by Gas chromatography (English PDF)

4.5 Sodium chloride (NaCl)

It was fired in a muffle furnace at 400 ° C for 4 h, cooled and placed in a ground glass bottle and stored in a desiccator.

4.6 Anhydrous sodium sulfate (Na2SO4)

It was fired in a muffle furnace at 400 ° C for 4 h, cooled and placed in a ground glass bottle and stored in a desiccator.

4.7 Atrazine standard solution. rho = 100 mg/L, the solvent is acetone, commercially available.

4.8 Carrier gas. nitrogen, purity >=99.999%.

4.9 Combustion gas. hydrogen, purity >= 99.95%.

4.10 Gas-assisted gas. oil-free compressed air, purified by 5 Å molecular sieve.

6.1 Sample collection and preservation

Samples were taken with reference to the relevant regulations of HJ/T 91 and HJ/T 164. Use 500 ml hard ground glass bottle or have poly four Samples are taken from the threaded glass bottle of the vinyl fluoride cover. The sample should be filled with the sample bottle and sealed, placed in a refrigerator at 4 °C.

Save inside. The sample should be extracted within 7 days after sampling.

6.2 Preparation of samples

6.2.1 Extraction

Take 100 ml of sample into a 250 ml separatory funnel (5.5), add 5 g of sodium chloride (4.5), dissolve and add 15 ml Dichloromethane (4.1), shaken for 5 min, allowed to stand for 15 min, layered, collected organic phase, repeated extraction, combined extraction the liquid was taken and dried over anhydrous sodium sulfate (4.6).

Note 1. If emulsification occurs during the extraction process, mechanical separation can be used to complete the two-phase separation, including agitation, centrifugation, and ultrasonic methods.

Demulsification, can also be used to break the milk by freezing.

6.2.2 Purification

For samples with complex compositions, the following purification method can be used. concentrate the extract (6.2.1) to near dry and then add positive About 1 ml of hexane is used for purification. Purification step. activate the purification column (5.7) with 10 ml of n-hexane (4.3), wait for the column when the hexane is nearly dry, the n-hexane concentrate is transferred to a purification column, and the concentrating tube is washed 2 to 3 times with 5 ml of n-hexane.

On the upper column, control the elution speed to about 2.5 ml/min (about 1 drop/s), discard the eluent; then use a 10 ml volume ratio of 9.1.

Elution with hexane and ethyl acetate (4.4) was carried out to control the elution rate to about 2.5 ml/min (about 1 drop/s), and the eluate was collected.

Note 2. The cleaner groundwater, surface water and domestic sewage extract (6.2.1) can be directly pressed (6.2.3) without purification steps.

The steps are processed.

6.2.3 Concentration and replacement of solvents

Concentrate the extract (6.2.1) or the purified eluent (6.2.2) with a concentration unit (5.4) and convert the solvent to acetone.

(4.2), make up to 1.0 ml. The samples were stored in a 4 ° C refrigerator and analyzed within 40 d.

6.3 Preparation of blank samples

While analyzing the sample, take 100 ml of experimental water instead of the sample, follow the same procedure as the preparation of the sample (6.2).

A blank sample was prepared.

7.1 Gas Chromatography Reference Conditions

Inlet temperature. 240 ° C, split injection, split ratio 10.1; oven temperature. initial temperature 40 ° C, keep 3 3 min, rise to 190 ° C at 30 ° C/min, hold for 5 min, then increase to 250 ° C at 30 ° C/min, keep 5 min; carrier gas flow rate. 1.0 ml/min; detector temperature. 300 ° C, hydrogen flow rate. 3.0 ml/min, air flow rate. 60.0 Ml/min; injection volume. 1.0 µl.

7.2 Establishing a calibration curve

Take 5 5.0 ml volumetric flasks, add appropriate amount of acetone (4.2), and add 5.0 with a micro-syringe (5.6).

Ll, 10.0 µl, 20.0 µl, 40.0 µl, 100.0 µl of atrazine standard solution (4.7), make up to volume with acetone (4.2), and mix.

The concentration of atrazine was 0.10 mg/L, 0.20 mg/L, 0.40 mg/L, 0.80 mg/L, 2.00 mg/L, respectively.

Standard series. The concentration of the standard series (mg/L) is plotted on the abscissa, and the corresponding peak area (or peak height) of the chromatogram is vertical.

Coordinates, establish a standard curve.

7.3 Sample determination

The sample was treated according to the preparation method (6.2) of the sample, and then measured according to the gas chromatography reference condition (7.1).

Note 3. When the actual sample concentration exceeds the calibration curve range, dilute the sample to the linear range of the calibration curve before sample preparation (6.2) and determination.

7.4 Blank test

The prepared blank sample (6.3) was measured according to the same instrumental analysis conditions as the standard curve.

8.1 Qualitative analysis

The target compound is characterized based on the retention time of the target in the sample and the target in the standard series.

The retention time window t±3S was established before sample analysis. t is the retention of the target compound at each concentration level at the initial calibration Time average, S is the standard deviation of the retention time of the target compound at each concentration level at the initial calibration. Target analysis the compound should peak within the retention time window. The gas chromatogram of atrazine is shown in Figure 1 under the reference chromatographic conditions of this standard.

Figure 1 Gas chromatogram of atrazine (2.0 mg/L)

Note 4. If atrazine is detected in the sample, it can be confirmed using an auxiliary qualitative column (5.3) or GC-MS assisted qualitative determination.

8.2 Quantitative analysis

Calculate the mass concentration (µg/L) of atrazine in the sample according to formula (1) using the external standard curve method.

100011 xx=

In the formula.

rho--the mass concentration of atrazine in the sample, µg/L;

4rho1--calculate the mass concentration of atrazine in the sample according to the standard curve, mg/L;

V--sample sampling volume, ml V1--The concentration of the extract after concentration is adjusted to ml.

8.3 Result representation

When the measurement result is greater than or equal to 100 µg/L, the result retains three significant figures; when less than 100 µg/L, the result is guaranteed.

Leave one decimal place.

9.1 Precision

Six laboratories tested a uniform sample of atrazine at 1.00 µg/L, 10.0 µg/L, and 18.0 µg/L.

The relative standard deviations in the laboratory are. 4.1% ~ 6.7%, 3.1% ~ 6.1%, 2.0% ~ 3.3%; interlaboratory phase the standard deviations were. 5.5%, 3.3%, and 1.3%; the repeatability limits were. 0.30 µg/L, 1.34 µg/L, and 1.41 µg/L, respectively;

Reproducibility limits were. 0.40 µg/L, 1.53 µg/L, and 1.44 µg/L, respectively.

9.2 Accuracy

The blank samples were spiked in 6 laboratories, and the scalar weights were 0.20 µg, 1.00 µg, and 1.80 µg, respectively.

The recoveries of spiked standards were. 85.5%~111%, 88.5%~108%, 88.3%~102%; the final value of spiked recovery was 95.2% ± 6.6%, 96.5% ± 3.6%, 96.3% ± 1.8%.

Six laboratories performed spiked measurements on surface water, industrial wastewater and domestic sewage, respectively. The scalar weight was 0.05.

Gg, 0.50 µg, 1.80 µg, the recoveries of standard addition are. 81.2%~104%, 75.6%~105%, 78.9%~105%;

The final recovery values were 92.9% ± 6.0%, 88.3% ± 8.8%, and 94.4% ± 8.0%.