HJ 770-2015Water quality. Determination of Phenoxy carboxylic acids herbicide by High Performance Liquid Chromatography. Tandem Mass Spectrometry (English PDF)

4.1 Standard solution

4.1.1 Phenoxy carboxylic acid herbicide standard stock solution. rho = 100 µg/ml.

Can be directly purchased certified standard solution can also be prepared with standard materials. The stock solution is stored in the dark at 0 ° C to 4 ° C or referenced to the manufacturer product manual. Use should be restored to room temperature, and shake.

4.1.2 phenoxy carboxylic acid herbicides standard use of liquid. rho = 10.0 µg/ml (reference concentration).

The standard stock solution (4.1.1) of the phenoxy carboxylic acid compound is diluted with acetonitrile (4.2) as required. Standard use of liquid at 4 °C cold, avoid Light preservation, shelf life of two months. Use should be restored to room temperature, and shake.

4.1.3 Internal standard stock solution. rho = 100 µg/ml.

The internal standard is 2,4-dichlorophenoxyacetic acid-13C6, can be directly purchased certified standard solution can also be prepared with the standard material. The stock solution is at zero °C ~ 4 °C Keep away from light or refer to the manufacturer's product description. Use should be restored to room temperature, and shake.

4.1.4 Internal standard liquid. rho = 10.0 µg/ml (reference concentration).

The internal standard stock solution (4.1.3) was diluted with acetonitrile (4.2) as needed. Internal standard use of liquid at 0 °C ~ 4 °C dark preservation, shelf life Two months. Use should be restored to room temperature, and shake.

4.2 acetonitrile (CH3CN). pesticide residues.

4.3 methanol (CH3OH). pesticide residues.

4.4 Methanol/water mixed solution. 1 4.

4.5 acetonitrile/water mixed solution. 1 4.

4.6 Ammonium acetate solution. C (CH3COONH4) = 0.002 mol/L.

Weigh 0.077 g of ammonium acetate in 500 ml of experimental water and 0.22 µm filter (4.13).

4.7 Sulfuric acid (H2SO4). rho (H2SO4) = 1.84 g/ml.

4.8 Sodium hydroxide (NaOH).

4.9 Sulfuric acid solution. 1 1.

Measure 50 ml of concentrated sulfuric acid (4.7) and slowly add to 50 ml of water.

4.10 Sodium hydroxide solution. rho (NaOH) = 0.4 g/ml.

Weigh 40 g of sodium hydroxide (4.8) in water and set to 100 ml.

4.11 solid phase extraction column. filler for the divinyl benzene and N-vinyl pyrrolidone copolymer (HLB) or the same column efficiency of the extraction column, specifications for the 6 Ml/500 mg.

4.12 Nitrogen. Purity >=99.99%.

4.13 Filtration. 0.22 µm Teflon or other material equivalent filter.

6.1 Sample collection

Samples were collected with reference to the relevant provisions of HJ/T 91 and HJ/T 164.

Fresh water was collected with a pre-washed clean and dry milled brown glass bottle (250 ml).

6.2 Sample storage

Collected water samples 0 °C ~ 4 °C dark preservation, 3 days analysis is completed.

6.3 Preparation of the sample

6.3.1 Direct injection method

Mix 1.0 ml of water, add the internal standard solution 5.0 µl (4.1.4), mix and filter through the 0.22 µm filter (4.13), placed in the sample Bottle, to be tested.

6.3.2 Solid phase extraction method

The solid phase extraction column (4.11) was activated with 10 ml of methanol (4.3) and 10 ml of experimental water to ensure the stigma infiltration. Measure 100 Ml water sample, using a sulfuric acid solution (4.9) or sodium hydroxide solution (4.10) to adjust the pH to neutral water, water samples below 10 ml/min (About 3 to 4 drops/second) flow rate through the column. The volume of the waste water sample can be appropriately reduced according to the actual situation. Mix the solution with 10 ml of methanol/water (4.4) Leave the column to remove the weaker impurities on the column. Followed by purging with nitrogen (4.12) and drying the column. And then 10 ml of a Alcohol (4.3) The column was eluted at a flow rate of about 3 ml/min (about 1 drop/sec), and the eluate was received in the collection tube. The eluate was blown through nitrogen (4.12, Pay attention to keep the liquid slightly fluctuate) to dry, dry with acetonitrile/water solution (4.5) to 1.0 ml, and finally add the internal standard liquid 5.0 µl (4.1.4), after mixing 0.22 µm filter (4.13), placed in the sample bottle, to be tested.

6.4 Preparation of blank sample

6.4.1 Lab blank

The samples were prepared in the same manner as in the water treatment (6.3.1) to prepare a blank sample with direct injection.

The solid phase extraction method was prepared according to the same procedure of water sample treatment (6.3.2) instead of the sample.

6.4.2 Full program blank

Before sampling, follow the sample collection (6.1) and sample preservation (6.2) method, with the experimental water preparation of the whole program blank sample, and with it the sampling process is brought to the sampling site. The whole program blanks the sample with the actual sample and reaches the laboratory at the same time.

7.1 Instrument reference conditions

7.1.1 Liquid Chromatographic Reference Conditions

Mobile phase. 0.002 mol/L ammonium acetate aqueous solution (A phase), acetonitrile (B phase), gradient elution program in Table 1.

Flow rate. 0.3 ml/min.

Column temperature. 40 ° C.

Injection volume. 10 µl.

Table 1 Liquid Chromatography Mobile Phase Gradient Elution Procedure

Time (min) A% B%

6.5 80 20

7.1.2 Mass Spectral Reference Conditions

Negative ion mode

Capillary voltage. 2.8 kV Ion source temperature. 120 ° C Atomization temperature. 350 ° C Atomized gas flow rate. 800 L/h Reverse blow flow rate. 10 L/h Collision air flow rate. 0.10 ml/min Multi-ion reaction monitoring mode (MRM), the specific conditions in Table 2.

Table 2 Monitoring conditions for the multi-ion reaction of the target compound

The compound parent ion (m/z) Ion (M/z) Dwell time/s tap hole voltage/V collision voltage/V 199 * 141 20 15 2-methyl-4-chlorophenoxyacetic acid 0.02 219 * 161 16 12 2,4-dichlorophenoxyacetic acid 0.02 213 * 141 20 15 2- (2-methyl-4-chlorophenoxy Yl) propionic acid 215 143 0.02 233 * 161 16 12 2- (2,4-dichlorophenoxy) - propionic acid 235 163 0.02 253 * 195 16 12 2,4,5-trichlorophenoxyacetic acid 0.02 267 * 195 16 10 2- (2,4,5-trichlorophenoxy) Yl) -propionic acid 269 197 0.02 247 * 161 10 10 4- (2,4-Dichlorophenoxy) -Butyric acid 249 163 0.02 227 * 141 15 12 4- (2-methyl-4-chlorophenoxy Yl) butyric acid 229 143 0.02 225 * 167 15 12 2,4-dichlorophenoxyacetic acid-13C6 227 169 0.02 Note. with the * for the quantitative ion pair, for different mass spectrometry equipment, the parameters may be different, should be measured before the mass spectrometry parameters to optimize the best.

7.1.3 Instrument tuning

According to the instrument manual in the specified time and frequency of liquid chromatography/tandem mass spectrometer for the quality of the instrument and the sensitivity correction, to ensure that the instrument is in the best test state.

In the course of the use of the instrument, if the instrument found that the quality of significant deviation or a significant decline in sensitivity, the instrument should be immediately re-Perform quality and sensitivity correction.

7.2 Calibration

7.2.1 Drawing of calibration curves

(4.1.2) in a mixed solution of acetonitrile/water (4.5), at least 5 concentration points were prepared.

The standard concentrations of phenoxy carboxylic acids were 1.0 µg/L, 2.0 µg/L, 5.0 µg/L, 10.0 µg/L, 50.0 µg/L and 100 µg/L, respectively (This is the reference concentration), in each standard solution of the standard solution by adding 5.0 µl standard internal standard liquid (4.1.4), so that the internal standard mass concentration for 50.0 µg/L, stored in a brown sample vial, to be tested.

From the low concentration to the high concentration, the standard series solution was sequentially injected with the concentration of the target component in the standard series solution as the abscissa the calibration curve is established by plotting the ratio of the peak area (or peak height) to the peak area of the internal standard (or peak height) and the product of the internal standard concentration.

The calibration curve has a correlation coefficient >=0.995, otherwise the calibration curve is redrawn.

Y = ax b (1)

Where. x - target component concentration, µg/L Y - the product of the peak area (or peak height) ratio of the target component and the internal standard substance and the concentration of the internal standard substance A - calibration curve slope B - calibration curve intercept

7.2.2 Liquid Chromatography/Mass Spectrometry

Fig.1 Total ion chromatogram (concentration. 50 µg/L) of liquid chromatography/mass spectrometry of 8 phenoxy carboxylic acid herbicides and internal standard

Note. 1. 2-Methyl-4-chlorophenoxyacetic acid; 2,3. 2,4-dichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid-13C6; 4. 2- (2- 4-chlorophenoxy) propionic acid;

5. 2- (2,4-dichlorophenoxy) -propionic acid; 6. 2,4,5-trichlorophenoxyacetic acid; 7. 2- (2,4,5-trichlorophenoxy) - propionic acid; 8. 4- (2,4-dichlorophenoxy) -but Acid; 9. 4- (2-methyl-4-chlorophenoxy) butyric acid

7.3 Determination

7.3.1 Specimen determination

The same instrumental analysis conditions were used to determine the calibration curve.

7.3.2 Blank test

The measurement of the blank sample (6.4) was carried out according to the same instrument analysis condition (7.1) as the test sample.

Calculation and representation of results

8.1 Qualitative analysis of the target compound

Each of the tested components was selected for 1 parent ion and 2 daughter ions for monitoring. Under the same experimental conditions, the components of the sample to be tested the absolute value of the relative standard deviation should be less than 2.5% compared to the retention time of the target component in the standard sample; and the sample spectrum in the figure, the relative abundance (Ksam) of the qualitative ions of each component is the relative abundance of the qualitative ions in the standard solution spectrum close to the concentration (Kstd), the deviation does not exceed the range specified in Table 3, and it can be determined that there is a corresponding analyte in the sample.

Where. Ksam - the relative abundance of qualitative ions in a sample in a sample,% A2 - the peak area (or peak height) of the qualitative ion pair of a group in the sample A1 - the peak area (or peak height) of the quantitative ion pair of a component in the sample (3) where. Kstd - the relative abundance of qualitative ions in a standard sample,% Astd2 - the peak area (or peak height) of the qualitative ion pair of a group in the standard sample Astd1 - the peak area (or peak height) of the quantitative ion pair of a component in the standard sample

Table 3 Qualitative confirmation of the maximum allowable deviation of the relative abundance of ions

unit.%

A qualitative ion of a component in a standard sample Relative ion abundance (Kstd) Kstd> 50 20 9 precision and accuracy

9.1 Precision

9.1.1 Direct injection method

Six labs were used for the concentration of phenoxy carboxylic acid herbicides at concentrations of 1.0 µg/L, 10.0 µg/L and 50.0 µg/L, respectively.

6 repeated measurements.

The relative standard deviations in the laboratory were 2.4% ~ 13.9%, 1.1% ~ 7.3%, 2.0% ~ 6.6% respectively.

The relative standard deviations were 1.5% ~ 6.8%, 0.6% ~ 4.8%, 0.7 ~ 4.2%, respectively.

The reproducibility limits were. 0.2µg/L ~ 0.3µg/L, 0.9µg/L ~ 1.4µg/L, 5.1µg/L ~ 6.3µg/L.

The reproducibility limits were. 0.2µg/L ~ 0.3µg/L, 1.1µg/L ~ 1.5µg/L, 5.3µg/L ~ 7.4µg/L.

9.1.2 Solid phase extraction

6 laboratories with a concentration of 0.050µg/L of phenoxy carboxylic acid herbicides, 0.500µg/L and 1.00µg/L of the uniform blank sample Line six times to repeat the determination.

The relative standard deviations in the laboratory were 1.4% ~ 8.9%, 0.6% ~ 3.3% and 0.4% ~ 1.8% respectively.

The relative standard deviations were 1.2% ~ 2.1%, 0.2% ~ 0.8%, 0.2% ~ 0.6%, respectively.

The limit of reproducibility was 0.005µg/L ~ 0.007µg/L, 0.018µg/L ~ 0.031µg/L, 0.019µg/L ~ 0.032µg/L.

The reproducibility limits were. 0.005µg/L ~ 0.007µg/L, 0.019µg/L ~ 0.033µg/L, 0.02µg/L ~ 0.033µg/L.

9.2 Accuracy

9.2.1 Direct injection method

Six laboratories were tested for surface water and waste water, and the spiked concentrations were 10.0 µg/L and 50.0 µg/L, respectively. Spiked recovery rate the results were. 88.0% ~ 102%, 87.5% ~ 102%, the final recoveries were 90.8% ± 5.2% ~ 99.8% ± 3.6% 93.3% ± 4.2% ~ 97.5% ± 8.0%.

9.2.2 Solid phase extraction

Six laboratories carried out spike recovery experiments on surface water. The spiked concentrations were 0.100 µg/L and 1.00 µg/L, respectively.

The results showed that the titer was 2.00µg/L and 20.0µg/L, respectively. The recoveries of spiked were 74.2% 89.2%, 75.2% ~ 89.9%, and the final recoveries were 75.9% ± 1.4% ~ 87.5% ± 3.0% and 76.4 ± 1.4% ~ 89.3% ± 1.0%.

The accuracy and accuracy of the results are given in Appendix B.

10.1 Blank analysis

Each analysis is done at least one lab blank and full program blank. To check for possible interference.

The concentration of each target compound in the laboratory blank and the program blank should not exceed the detection limit of the method, otherwise it should be resampled.

10.2 Determination of parallel samples

A parallel sample is to be analyzed for every 20 samples or for each batch (less than 20 samples/batch). The relative standard deviation of the parallel samples should be controlled 20% or less.

10.3 Matrix spikes

Approximately 20 samples or per batch (less than 20 samples/batch) need to be a matrix plus standard sample. The range of recoveries should be determined by direct injection Between 85% and 110%, the recoveries of the solid phase extraction were between 70% and 120%.

10.4 Calibration

10.4.1 Initial calibration

The initial calibration is required for the initial use of the instrument, or when the instrument is repaired, the column is replaced, or the continuous calibration is not acceptable. That is to establish the standard Quasi-curve.

10.4.2 Continuous calibration

Continuous calibration was performed using the intermediate concentration point of the analytical calibration curve, 1 for every 20 samples or per batch (less tha...