HJ 716-2014Water qualiy. Determination of nitroaromatics. Gas chromatography mass spactrometry (English PDF)

7.2 Preparation of the sample

7.2.1 Liquid-liquid extraction

7.2.1.1 Extraction

The exact amount of 1000 ml water sample (sample extraction of the water volume may be appropriately adjusted according to the water quality), with a hydrochloric acid solution (5.18) or hydrogen Sodium hydroxide solution (5.19) adjusting the pH in the neutral water sample, placed in a separatory funnel, was added 5.0 µl substitute standard solution (5.16), Mix, plus 50 ml of methylene chloride and extracted 3 ~ 5 min, allowed to stand for 5 ~ 10 min stratification, the organic phase was separated, then 30 ml of methylene chloride was added Extraction was repeated once, and the combined extracts were dried over anhydrous sodium sulfate, and concentrated to about 0.5 ml, add 5 ml of n-hexane, concentrated to continue Approximately 0.5 ml.

Note 1. Emulsion phenomenon extraction process, we can use salting, stirring, centrifugation, freezing and breaking glass wool filtration method.

Note 2. The concentration of the extract process should pay attention to the speed of the water bath temperature and concentration, otherwise nitrobenzene prone to large losses.

7.2.1.2 Purification

Flush with 8 ml of n-hexane Florisil before the liquid disappears, and the extract was concentrated liquid was transferred to a cleaning column with 4 ml n Washed with hexane and concentrated pipe, washing liquid also transferred onto florisil (Note. You should always maintain a level above the filler left), discard the effluent Washed with 10 ml of dichloromethane - n-hexane (5.20) eluting samples, collected in a receiving tube.

7.2.1.3 Concentrate volume

The eluate was concentrated to about 0.5 ml, to which was added 10.0 µl using internal standard solution (5.15), with dichloromethane and dilute to 1.0 ml, Mix tested.

7.2.2 Solid Phase Extraction

7.2.2.1 Activation. successively with 5 ml of dichloromethane, 5 ml of methanol and 10 ml of water, activated solid phase extraction column, flow rate of about 5 ml/min.

Note 3. The activation process should be avoided SPE packing above the liquid level is drained, or need to re-activation.

7.2.2.2 Extraction. The exact amount of 1000 ml water sample (sample enrichment of the water volume may be appropriately adjusted according to the actual situation of water samples), acid-soluble salt Solution (5.18) or sodium hydroxide solution (5.19) in water samples neutral pH adjusted to each water sample was added methanol (5.2), methanol concentration of about 5 per mille, then add 5.0 µl alternative to the standard solution (5.16) and mix. The water sample to 5 ~ 10 ml/min flow rate of enriched sample After completion, rinse with 10 ml of water on the inner wall of the vial, and enriched in the solid phase extraction column, drained cartridge.

If using automated solid phase extraction sample extraction device, in accordance with the rules of each model of the instrument extracted.

7.2.2.3 elution. with 10 ml of methylene chloride to 2 ml/min sample rate of elution, the eluent dried column eluate to collect concentrated Shrink tube.

47.2.2.4 concentrated volume. eluent shrink to 0.5 ml, was added 10.0 µl using internal standard solution (5.15), with dichloromethane to volume to 1.0 ml, mix, prepare analysis.

Note 4. high suspended solids content of the water sample, not for solid phase extraction.

7.3 Preparation of blank samples

Samples were analyzed at the same time, taking the same volume of water, according to the sample preparation method of (7.2), prepare a blank sample.

Analysis Step 8

8.1 GC reference conditions

Inlet temperature. 250 °C.

Injection mode. split injection, split ratio of 5. 1.

Oven temperature. 60 °C -> 10 °C/min -> 200 °C -> 15 °C/min -> 250 °C.

Column flow rate. 1.0 ml/min.

Injection volume. 1.0 µl.

8.2 Mass Reference Conditions

Scan mode. Full scan or selected ion monitoring (SCAN/SIM).

Scan range. 40 ~ 500 amu.

Ion source temperature. 230 °C.

Transfer line temperature. 280 °C.

Ionization energy. 70 eV.

The remaining parameters are set with reference to the instrument instruction manual.

8.3 Instrument performance checks

Before using the instrument, sample and analyze each running 24 h, gas chromatography mass spectrometer system must be carried out to check the performance of the instrument. Take 1.0 µl Tuning standard solution (5.21) directly into the chromatograph, DFTPP key ion abundance obtained shall meet the specified criteria in Table 1. Otherwise required Some parameters can be adjusted or cleaning the mass spectrometer ion source.

Table 1 Decafluorotriphenylphosphine triphenylphosphine (DFTPP) ion and abundance of key criteria

Mass to charge ratio (m/z) abundance of standard mass ion (m/z) abundance Standard 5% 9% 51 base peak 30% to 60% of the base peak 199 Less than 69 68 275 2% of the peak of the fundamental peak of 10% to 30% 70 less than 69 peaks higher than 2% 365 1% of the base peak 127 base peak of 40% to 60% and less than 441 exist peaks 443 197 is less than 1% of the base peak 442 is greater than 40% of the base peak 198 base peak, the abundance of 17% to 23% 100% 443 442 peak

8.4 Calibration

8.4.1 Calibration Series

A certain amount of nitrobenzene compounds using standard solution (5.14) and the use of alternatives to the standard solution (5.16) in dichloromethane (5.4) to prepare a series of six standard concentration point, the mass concentration of nitrobenzene compounds were 0.1 µg/ml, 0.5 µg/ml, 1.0 µg/ml, 2.0 µg/ml, 5.0 µg/ml, 10.0 µg/ml, was added to the standard uses standard solution (5.15), so that the internal standard concentration was 2.0 µg/ml.

58.4.2 Average relative response factor calibration curve

Standard Series point i of the target (or substitutes) relative response factor (iRRF), according to (1) calculated as follows.

i IS

IS ii

ARRF A

Where. iRRF-- standard series point i object (or substitutes) relative response factor;

ISiA - Standard series point i object (or substitute) corresponding to the response of the internal standard quantitation ion;

iA - response standard series point i object (or substitute) quantitative ion;

IS - standard series, the subject of concentration, g/ml;

i - Standard series point i object (or substitute) mass concentration, g/ml.

Average object (or substitutes) relative response factors iRFF, (2) calculated according to the formula.

RRF

RRF

Wherein. the average iRRF-- object (or substitutes) relative response factors;

iiRRF - Standard series point i object (or substitutes) relative response factor;

n-- standard series points.

RRF standard deviation (SD), in accordance with the formula (3) is calculated.

RRF relative standard deviation (RSD), in accordance with the formula (4) is calculated.

8.4.3 calibration curve using the method of least squares If a standard series of target compounds relative standard deviation of the relative response factor greater than 20%, then the required target Least Squares Method calibration curve calibration. That is relative to the target and within the target response value ratio of the vertical axis, the concentration ratio of the horizontal axis, a calibration curve.

8.5 Determination

Take 1.0 l sample (7.2) into the gas chromatograph mass spectrometer, a calibration curve in accordance with the same instrumental conditions were determined.

8.6 blank test

Take the prepared blank sample (7.3), according to a calibration curve with the same instrumental conditions were determined.

9 Results Calculation and representation

9.1 Qualitative Analysis the retention time of the sample in the target compound (RT), the fragment ions of different mass to charge ratio and ion abundance than qualitative. Nitrobenzene i = 1 n-1SD = 2 (RRF RRF) 100% SDRSD = xRRF Characteristics of ionic compounds 6, see Appendix B.

Retention time in the sample with the desired retention time of the target compound (i.e., the average standard solution relative retention time) of the relative deviation should be controlled within ± 3%; different fragment ion abundance ratios and the expected sample target compound (ie, the standard fragment ions in solution the average ion abundance ratio) relative deviation should be controlled within ± 30%.

Under instrument conditions specified in this standard, total ion current target compound, shown in Figure 1.

1- nitrobenzene -d5 (SS); 2- nitrobenzene; 3-o - nitrotoluene; 4- Room - nitrotoluene; 5-p - nitrotoluene; 6-- Room - nitro chlorobenzene ;

7-p - nitro chlorobenzene; 8- o - nitro chlorobenzene; 9-1--bromo-2-nitrobenzene (IS); 10- to - dinitrobenzene; 11- Room - dinitrobenzene ; 12-2,6-Dinitrotoluene; 13-o - dinitrobenzene; 14-2,4- dinitrotoluene; 15-2,4- dinitrochlorobenzene; 16-3,4- dinitrotoluene;

17-2,4,6- trinitrotoluene; 18- PCNB (SS) Fig.1 Total ion nitrobenzene compounds

9.2 Quantitative Analysis in full-scan method to collect data, to select the ions, internal standard.

9.2.1 average relative response factor calculation when the object (or substitute) using the average relative response factor for calibration, sample quality target (or substitutes) concentrated Degree according to formula (5) is calculated.

x IS ex

IS i

AV DFVA RRF

x= x xx (5)

Where. - mass concentration of the target compound or substitute a sample, g/L;

xA - object (or substitute) response quantitation ion;

ISA - and the target (or substitute) corresponding to the response of the internal standard quantitation ion;

IS - mass concentration of the internal standard, g/L;

exV - sample volume, ml;

0V - water sample volume, L;

DF-- dilution factor.

79.2.2 Calculated using linear or non-linear calibration curve

When the object (or substitute) linear or non-linear calibration curve for calibration, sample target (or substitutes) mass volume concentration is calculated by the corresponding calibration curve according to equation (6).

Vexi x DFx (6)

Where. i - concentration by the calibration curve to obtain the objective compound (or substitutes) of, g/ml;

exV - sample volume, ml;

0V - water sample volume, L;

DF-- dilution factor.

9.3 The results are shown when the measurement result is less than 1.00 g/L, data retention to the second decimal place; when the result is greater than equal to 1.00 g/L, data Three significant figures.

10 precision and accuracy

10.1 Precision

Six laboratories 0.100 g/L, 2.50 g/L, 5.00 g standard samples/L nitrobenzene compounds at different concentrations were measured.

Liquid-liquid extraction. the laboratory relative standard deviation of 1.1% ~ 9.2%, inter-laboratory relative standard deviation of 1.0% to 12.6%, the repeatability limit 0.01 g/L ~ 0.46 g/L, the reproducibility limit 0.03 g/L ~ 0.88 g/L.

Solid Phase Extraction. Laboratory relative standard deviation of 1.3% ~ 8.8%, inter-laboratory relative standard deviation of 1.0% to 11.9%, the repeatability limit 0.01 g/L ~ 0.59 g/L, the reproducibility limit 0.03 g/L ~ 1.02 g/L.

10.2 Accuracy

Liquid-liquid extraction.

Six laboratories containing compounds nitrobenzene low, medium and high concentrations of the different samples were analyzed measured recovery was. 71.9% to 101%. Six laboratories containing compound concentration of nitrobenzene was 2.50 g/L were unified sample Determination recoveries range 78.4% to 101%.

Solid Phase Extraction.

Six laboratories containing compounds nitrobenzene low, medium and high concentrations of the different samples were analyzed measured recovery was. 71.4% ~ 100%. Six laboratories containing compound concentration of nitrobenzene was 2.50 g/L were unified sample Determination recoveries range 73.6% to 101%.

Precision and accuracy of results in Appendix C.

11 Quality Assurance and Quality Control

11.1 Analysis of the internal standard Comparison Comparison internal standard internal standard and internal standard curve middle point of the calibration curve verification, samples with the same batch of the internal standard calibration curve verification, Paul Stay time is not more than 10 s, quantification ion peak area varied between 50% to 100%.

Standard 811.2 allow initial calibration curve Standard Series object (or substitutes) relative response factor (RRF) relative standard deviation (RSD) should be less than or equal to 20%.

If the object of a series of standards relative response factor relative standard deviation is greater than 20%, the target required this method of least squares calibration curve Line calibration, nonlinear curve fitting may also be used for calibration, the correlation coefficient should >=0.990.

11.3 calibration curve verification A second intermediate point of the calibration curve of the standard solution is determined at least every working day, according to equation (7) Calculate measured value of the target compound (cRFF or i) and last initial calibration curve relative deviation (iRFF or s) between (RD). Formula is as follows.

100x-=

siRD

Where. s - the concentration of the calibrator calibration curve middle point, g/ml;

i - The calibration concentration measurement, g/ml.

If RD<=+/-20%, the initial calibration curve can continue to use; if any one of the compounds RD > +/-20%, to reconfigure System curve or intermediate point to measure the...