HJ 894-2017Water quality. Determination of extractable petroleum hydrocarbons(C10-C40). Gas chromatography (English PDF)

7.1 Sample collection and preservation

Water samples were taken according to the relevant provisions of GB 17378.3, HJ/T 91 and HJ/T 164. Sampling bottles (6.1) mining Intensive 1000ml sample, hydrochloric acid solution (5.6) acidified to pH <= 2, the sample was stored at 4 °C, 14d completed Extraction, 40d analysis.

Note. When the petroleum hydrocarbon content in the water sample is too high, the sampling volume may be appropriately reduced.

7.2 Sample Preparation

7.2.1 Sample extraction

Transfer the entire sample to a 2 L separatory funnel (6.6), take 60 ml methylene chloride (5.1) and wash the sample vial.

3 all transferred to a separatory funnel, oscillation extraction 5 min (pay attention to deflated), stand for 10 min, until the two phases delamination, collecting the lower the organic phase. An additional 60 ml of dichloromethane was added and the above procedure was repeated and the extracts were combined. The extract was passed over anhydrous sodium sulfate (5.3) Dehydration. The entire aqueous phase was transferred to a 1000 ml graduated cylinder, and the sample volume was measured and recorded.

Note. Emulsification occurs during the extraction process, salting out, stirring, centrifugation, freezing and other methods can be used demulsification.

7.2.2 Sample concentration

The extract was concentrated to about 1 ml using a concentration apparatus (6.4) (Concentrated dichloromethane Reference conditions. water bath temperature 35 ° C, Degree of vacuum of 750 hPa), 10 ml of n-hexane (5.2) was added and concentrated to about 1 ml (n-hexane concentration, reference conditions. water Bath temperature 35 °C, vacuum degree 260 hpa), then add 10 ml n-hexane (5.2), and finally concentrated to about 1 ml, to be a net the Note. The concentration of the sample volume of not less than 1 ml, otherwise the recovery rate is low.

7.2.3 Sample purification

The column (6.5) was activated with 10 ml of dichloromethane-n-hexane solution (5.7) followed by 10 ml of n-hexane (5.2) when the column of n-hexane is nearly dry, transfer all the concentrated liquid to the purifying column, wash the collecting bottle with about 2 ml of n-hexane (5.2) the washings were combined on a column and eluted with 10 ml of dichloromethane-n-hexane solution (5.7). The column was collected by gravity Eluate in concentrate bottle.

Note. 1g magnesium silicate purification column of petroleum hydrocarbons purification capacity of 5 mg, if the determination of the total amount of petroleum hydrocarbons exceeds 5 mg, the extract required to be combined Divided after dilution management, re-purification measured.

7.2.4 Concentrated volume

Concentrate the eluate to approximately 1 ml using a concentrator (6.4) and dilute to 1.0 ml with n-hexane (5.2) for further testing.

7.3 Blank sample preparation

Replace the sample with distilled water, and follow the same procedure as sample preparation (7.2) to prepare a blank sample.

8.1 GC reference conditions

Inlet temperature. 320 ° C Column flow. 2.0 ml/min Oven temperature. Initial temperature 60 ° C for 1 min, Raise to 290 ° C at 8 ° C/min and then ramp to 320 ° C at 30 ° C/min for 7 min.

FID detector temperature. 330 ° C, hydrogen flow rate. 40.0 ml/min, air flow rate. 350.0 ml/min, makeup gas Flow. 30.0 ml/min.

Injection method. Splitless injection, split 0.75min after injection, split ratio 30.1, injection volume. 1.0 µl.

Collection column loss map, used to deduct the column peak area loss.

8.2 Calibration

Take 5 10 ml brown volumetric flask, respectively, add an appropriate amount of n-hexane (5.2), with a micro syringe were added 10.0, 50.0,100,500,1000 µl C10-C40 n-alkane standard solution (5.8), with n-hexane volume, mix. Formulated the n-alkanes concentration was 1.0 mg/L, 5.0 mg/L, 10.0 mg/L, 50.0 mg/L, 100 mg/L,

4 The total mass concentrations were 31.0 mg/L, 155 mg/L, 310 mg/L, 1550 mg/L, 3100 mg/L respectively.

The standard series of total mass concentration (mg/L) as the abscissa, the total peak area corresponding to the vertical axis, the establishment of the calibration curve line.

8.3 Sample Determination

Specimen (7.2) is measured according to the same GC reference conditions (8.1) as the calibration curve.

8.4 Blank test

The blank sample (7.3) is measured according to the same GC reference conditions (8.1) as the sample.

9.1 Qualitative analysis

According to the chromatographic component retention time of the target compound to be qualitative, the chromatogram shown in Figure 1. C10-C40 target compound the method of determining the total amount of the target compound starts from the peak of n-C10H22 (inclusive) to n-C40H82 (Including) the end of the peak, calculate the total peak area of C10-C40 (here peak area deducts the total peak area after column loss) the chromatogram of the column is shown in Figure 2.

Figure 1 C10-C40 normal paraffin gas chromatogram

5 Figure 2 8.1 Chromatogram of the column under GC reference conditions

9.2 Quantitative analysis

Based on the total peak area of the target compound in the retention time window (the total peak area here is the total peak after subtracting the column loss Area), obtained by external standard method of the total concentration of the target compound. Water quality extractable petroleum hydrocarbons (C10-C40) mass concentration rho (mg/L), calculated according to formula (1).

a-Axrho 1 xxx= (1)

Where. rho - water extractable petroleum hydrocarbon (C10-C40) mass concentration, mg/L;

Total peak area of the target compound (total peak area here is the total peak area after column loss) a - the intercept of the calibration curve;

b - the slope of the calibration curve;

V-water sample volume, L;

V1-sample volume, ml;

f - is the dilution factor.

9.3 Results show

When the determination result is 1.00 mg/L or more, the data retain three significant figures; when the result is less than 1.00 mg/L, Keep two decimal places.

10.1 Precision

Six laboratories, respectively, with extractable petroleum hydrocarbon concentrations of 0.05 mg/L, 0.10 mg/L, 1.00 mg/L of the unification the samples were measured 6 times in parallel. The relative standard deviations in the laboratory ranged from 6.1% to 6.8%, from 7.0% to 9.6% 9.0% ~ 12%; The relative standard deviation of the laboratory were 6.7%, 9.2%, 10% respectively; The repeatability limits were.

C40C10

60.01 mg/L, 0.02 mg/L and 0.30 mg/L, respectively. The reproducibility limits were 0.01 mg/L, 0.03 mg/L and 0.40 mg/L, respectively.

Six laboratories on domestic sewage, seawater and petrochemical industrial wastewater uniform samples were measured 6 times in parallel, the experiment Indoor relative standard deviations ranged from 6.6% to 24%, 6.7% to 31% and 6.2% to 29%, respectively; relative standard between laboratories Deviations range. 29%, 18%, 17%.

10.2 Accuracy

Six laboratories on the surface water, domestic sewage, seawater and petrochemical industrial wastewater uniform samples were spiked analysis the standard additions were 0.05 mg/L, 0.10 mg/L, 0.10 mg/L and 1.00 mg/L, respectively. The spiked recoveries were.

84% -96%, 78% -101%, 74% -93%, 83% -108%. The final recoveries of spiked samples were 91% ± 11% 85% ± 17%, 86% ± 15%, 90% ± 19%.

11.1 Blank test

Make at least 1 lab blank for every 20 samples or batches of samples (less than 20 samples/batches) with a blank value below Method detection limit.

11.2 Calibration curve

The calibration curve for the first calibration should have a correlation coefficient of >= 0.995.

11.3 Continuous calibration

Each determination of 20 samples should be continuous calibration, determination of a calibration curve intermediate concentration standard solution, the determination of the results and the relative error of the initial calibration should be within ± 20%.

11.4 Blank spike

Make at least one blank spike analysis for every 20 samples or batches of samples. The spike recovery should be between 70% and 120%.