METHOD 8318
N-METHYLCARBAMATES BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC)
1.0SCOPE AND APPLICATION
1.1Method 8318 is used to determine the concentration of N-methylcarbamates in soil, water and waste matrices. The following compounds can be determined by this method:
_______________________________________________________________________________
Compound Name CAS No.a
________________________________________________________________________________
Aldicarb (Temik) 116-06-3
Aldicarb Sulfone 1646-88-4
Carbaryl (Sevin) 63-25-2
Carbofuran (Furadan) 1563-66-2
Dioxacarb 6988-21-2
3-Hydroxycarbofuran16655-82-6
Methiocarb (Mesurol) 2032-65-7
Methomyl (Lannate)16752-77-5
Promecarb 2631-37-0
Propoxur (Baygon) 114-26-1
________________________________________________________________________________
a
Chemical Abstract Services Registry Number.
1.2The method detection limits (MDLs) of Method 8318 for determining the target analytes in organic-free reagent water and in soil are listed in Table 1.
1.3This method is restricted to use by, or under the supervision of, analysts experienced in the use of high performance liquid chromatography (HPLC) and skilled in the interpretation of chromatograms. Each analyst must demonstrate the ability to generate acceptable results with this method.
2.0SUMMARY OF METHOD
2.1N-methylcarbamates are extracted from aqueous samples with methylene chloride, and from soils, oily solid waste and oils with acetonitrile. The extract solvent is exchanged to methanol/ethylene glycol, and then the extract is cleaned up on a C-18 cartridge, filtered, and eluted on a C-18 analytical column. After separation, the target analytes are hydrolyzed and derivatized post-column, then quantitated fluorometrically.
2.2Due to the specific nature of this analysis, confirmation by a secondary method is not essential. However, fluorescence due to post-column derivatization may be confirmed by substituting the NaOH and o-phthalaldehyde solutions with organic-free reagent water and reanalyzing the sample. If
fluorescence is still detected, then a positive interference is present and care should be taken in the interpretation of the results.
2.3The sensitivity of the method usually depends on the level of interferences present, rather than on the instrumental conditions. Waste samples with a high level of extractable fluorescent compounds are expected to yield significantly higher detection limits.
3.0INTERFERENCES
3.1Fluorescent compounds, primarily alkyl amines and compounds which yield primary alkyl amines on base hydrolysis, are potential sources of interferences.
3.2Coeluting compounds that are fluorescence quenchers may result in negative interferences.
3.3Impurities in solvents and reagents are additional sources of interferences. Before processing any samples, the analyst must demonstrate daily, through the analysis of solvent blanks, that the entire analytical system is interference free.
4.0APPARATUS AND MATERIALS
4.1HPLC system
4.1.1An HPLC system capable of injecting 20 μL aliquots and
performing multilinear gradients at a constant flow. The system must also be equipped with a data system to measure the peak areas.
4.1.2C-18 reverse phase HPLC column, 25 cm x 4.6 mm (5 μm).
4.1.3Post Column Reactor with two solvent delivery systems (Kratos
PCRS 520 with two Kratos Spectroflow 400 Solvent Delivery Systems, or equivalent).
4.1.4Fluorescence detector (Kratos Spectroflow 980, or equivalent).
4.2Other apparatus
4.2.1Centrifuge.
4.2.2Analytical balance - + 0.0001 g.
4.2.3Top loading balance - + 0.01 g.
4.2.4Platform shaker.
4.2.5Heating block, or equivalent apparatus, that can accommodate
10 mL graduated vials (Sec. 4.3.11).
4.3Materials
4.3.1HPLC injection syringe - 50 μL.
4.3.2Filter paper, (Whatman #113 or #114, or equivalent).
4.3.3Volumetric pipettes, Class A, glass, assorted sizes.
R
4.3.4Reverse phase cartridges, (C-18 Sep-Pak [Waters Associates],
or equivalent).
4.3.5Glass syringes - 5 mL.
4.3.6Volumetric flasks, Class A - Sizes as appropriate.
4.3.7Erlenmeyer flasks with teflon-lined screw caps, 250 mL.
4.3.8Assorted glass funnels.
4.3.9Separatory funnels, with ground glass stoppers and teflon
stopcocks - 250 mL.
4.3.10Graduated cylinders - 100 mL.
4.3.11Graduated glass vials - 10 mL, 20 mL.
4.3.12Centrifuge tubes - 250 mL.
4.3.13Vials - 25 mL, glass with Teflon lined screw caps or
crimp tops.
4.3.14Positive displacement micro-pipettor, 3 to 25 μL
displacement, (Gilson Microman [Rainin #M-25] with tips, [Rainin #CP-25], or equivalent).
4.3.15Nylon filter unit, 25 mm diameter, 0.45 μm pore size,
disposable (Alltech Associates, #2047, or equivalent).
5.0REAGENTS
5.1HPLC grade chemicals shall be used in all tests. It is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lowering the accuracy of the determination.
5.2General
5.2.1Acetonitrile, CH CN - HPLC grade - minimum UV cutoff at 203 nm
3
(EM Omnisolv #AX0142-1, or equivalent).
5.2.2Methanol, CH OH - HPLC grade - minimum UV cutoff at 230 nm (EM
3
Omnisolv #MX0488-1, or equivalent).
5.2.3Methylene chloride, CH Cl - HPLC grade - minimum UV cutoff at
22
230 nm (EM Omnisolv #DX0831-1, or equivalent).
5.2.4Hexane, C H - pesticide grade - (EM Omnisolv #HX0298-1, or
614
equivalent).
5.2.5Ethylene glycol, HOCH CH OH - Reagent grade - (EM Science, or
22
equivalent).
5.2.6Organic-free reagent water - All references to water in this method refer to organic-free reagent water, as defined in Chapter One.
5.2.7Sodium hydroxide, NaOH - reagent grade - 0.05N NaOH solution.
5.2.8Phosphoric acid, H PO - reagent grade.
34
5.2.9pH 10 borate buffer (J.T. Baker #5609-1, or equivalent).
5.2.10o-Phthalaldehyde, o-C H(CHO) - reagent grade (Fisher
642
#0-4241, or equivalent).
5.2.112-Mercaptoethanol, HSCH CH OH - reagent grade (Fisher
22
#0-3446, or equivalent).
5.2.12N-methylcarbamate neat standards (equivalence to EPA standards must be demonstrated for purchased solutions).
5.2.13Chloroacetic acid, ClCH COOH, 0.1 N.
2
5.3Reaction solution
5.3.1Dissolve 0.500 g of o-phthalaldehyde in 10 mL of methanol, in
a 1 L volumetric flask. To this solution, add 900 mL of organic-free reagent water, followed by 50 mL of the borate buffer (pH 10). After mixing well, add 1 mL of 2-mercaptoethanol, and dilute to the mark with organic-free reagent water. Mix the solution thoroughly. Prepare fresh solutions on a weekly basis, as needed. Protect from light and store under refrigeration.
5.4Standard solutions
5.4.1Stock standard solutions: prepare individual 1000 mg/L solutions by adding 0.025 g of carbamate to a 25 mL volumetric flask, and diluting to the mark with methanol. Store solutions, under refrigeration, in glass vials with Teflon lined screw caps or crimp tops. Replace every six months.
5.4.2Intermediate standard solution: prepare a mixed 50.0 mg/L solution by adding 2.5 mL of each stock solution to a 50 mL volumetric flask, and diluting to the mark with methanol. Store solutions, under
refrigeration, in glass vials with Teflon lined screw caps or crimp tops.
Replace every three months.
5.4.3Working standard solutions: prepare 0.5, 1.0, 2.0, 3.0 and 5.0
mg/L solutions by adding 0.25, 0.5, 1.0, 1.5 and 2.5 mL of the intermediate mixed standard to respective 25 mL volumetric flasks, and diluting each to the mark with methanol. Store solutions, under refrigeration, in glass vials with Teflon lined screw caps or crimp tops.
Replace every two months, or sooner if necessary.
5.4.4Mixed QC standard solution: prepare a 40.0 mg/L solution from
another set of stock standard solutions, prepared similarly to those described in Sec. 5.4.1. Add 2.0 mL of each stock solution to a 50 mL volumetric flask and dilute to the mark with methanol. Store the solution, under refrigeration, in a glass vial with a Teflon lined screw cap or crimp top. Replace every three months.
6.0SAMPLE COLLECTION, PRESERVATION, AND HANDLING
6.1Due to the extreme instability of N-methylcarbamates in alkaline media, water, waste water and leachates should be preserved immediately after collection by acidifying to pH 4-5 with 0.1 N chloroacetic acid.
6.2Store samples at 4E C and out of direct sunlight, from the time of collection through analysis. N-methylcarbamates are sensitive to alkaline hydrolysis and heat.
6.3All samples must be extracted within seven days of collection, and analyzed within 40 days of extraction.
7.0PROCEDURE
7.1Extraction
7.1.1Water, domestic wastewater, aqueous industrial wastes, and
leachates
7.1.1.1Measure 100 mL of sample into a 250 mL separatory
funnel and extract by shaking vigorously for about 2 minutes with 30
mL of methylene chloride. Repeat the extraction two more times.
Combine all three extracts in a 100 mL volumetric flask and dilute
to volume with methylene chloride. If cleanup is required, go to
Sec. 7.2. If cleanup is not required, proceed directly to Sec.
7.3.1.
7.1.2Soils, solids, sludges, and heavy aqueous suspensions
7.1.2.1Determination of sample % dry weight - In certain
cases, sample results are desired based on dry-weight basis. When
such data is desired, a portion of sample for this determination
should be weighed out at the same time as the portion used for analytical determination.
WARNING:The drying oven should be contained in a hood or
vented. Significant laboratory contamination may
result from a heavily contaminated hazardous
waste sample.
7.1.2.1.1Immediately after weighing the sample for
extraction, weigh 5-10 g of the sample into a tared crucible.
Determine the % dry weight of the sample by drying overnight
o
at 105C. Allow to cool in a desiccator before weighing:
% dry weight = g of dry sample x 100
g of sample
7.1.2.2Extraction - Weigh out 20 + 0.1 g of sample into
a 250 mL Erlenmeyer flask with a Teflon-lined screw cap. Add 50 mL
of acetonitrile and shake for 2 hours on a platform shaker. Allow the mixture to settle (5-10 min), then decant the extract into a 250 mL centrifuge tube. Repeat the extraction two more times with 20 mL of acetonitrile and 1 hour shaking each time. Decant and combine all three extracts. Centrifuge the combined extract at 200 rpm for
10 min. Carefully decant the supernatant into a 100 mL volumetric
flask and dilute to volume with acetonitrile. (Dilution factor = 5) Proceed to Sec. 7.3.2.
7.1.3Soils heavily contaminated with non-aqueous substances, such as oils
7.1.3.1Determination of sample % dry weight - Follow
Secs. 7.1.2.1 through 7.1.2.1.1.
7.1.3.2Extraction - Weigh out 20 + 0.1 g of sample into
a 250 mL Erlenmeyer flask with a Teflon-lined screw cap. Add 60 mL
of hexane and shake for 1 hour on a platform shaker. Add 50 mL of acetonitrile and shake for an additional 3 hours. Allow the mixture to settle (5-10 min), then decant the solvent layers into a 250 mL separatory funnel. Drain the acetonitrile (bottom layer) through filter paper into a 100 mL volumetric flask. Add 60 mL of hexane and
50 mL of acetonitrile to the sample extraction flask and shake for
1 hour. Allow the mixture to settle, then decant the mixture into
the separatory funnel containing the hexane from the first extraction. Shake the separatory funnel for 2 minutes, allow the phases to separate, drain the acetonitrile layer through filter paper into the volumetric flask, and dilute to volume with acetonitrile. (Dilution factor = 5) Proceed to Sec. 7.3.2.
7.1.4Non-aqueous liquids such as oils
7.1.4.1Extraction - Weigh out 20 + 0.1 g of sample into
a 125 mL separatory funnel. Add 40 mL of hexane and 25 mL of
acetonitrile and vigorously shake the sample mixture for 2 minutes.
Allow the phases to separate, then drain the acetonitrile (bottom
layer) into a 100 mL volumetric flask. Add 25 mL of acetonitrile to
the sample funnel, shake for 2 minutes, allow the phases to
Repeat the extraction with another 25 mL portion of acetonitrile,
combining the extracts. Dilute to volume with acetonitrile.
(Dilution factor = 5). Proceed to Sec. 7.3.2.
7.2Cleanup - Pipet 20.0 mL of the extract into a 20 mL glass vial containing 100 μL of ethylene glycol. Place the vial in a heating block set at o
50 C, and gently evaporate the extract under a stream of nitrogen (in a fume hood) until only the ethylene glycol keeper remains. Dissolve the ethylene glycol residue in 2 mL of methanol, pass the extract through a pre-washed C-18 reverse phase cartridge, and collect the eluate in a 5 mL volumetric flask. Elute the cartridge with methanol, and collect the eluate until the final volume of 5.0 mL is obtained. (Dilution factor = 0.25) Using a disposable 0.45 μm filter, filter an aliquot of the clean extract directly into a properly labelled autosampler vial. The extract is now ready for analysis. Proceed to Sec. 7.4.
7.3Solvent Exchange
7.3.1Water, domestic wastewater, aqueous industrial wastes, and
leachates:
Pipet 10.0 mL of the extract into a 10 mL graduated glass vial containing 100 μL of ethylene glycol. Place the vial in a heating block o
set at 50 C, and gently evaporate the extract under a stream of nitrogen (in a fume hood) until only the ethylene glycol keeper remains. Add methanol to the ethylene glycol residue, dropwise, until the total volume is 1.0 mL. (Dilution factor = 0.1). Using a disposable 0.45 μm filter, filter this extract directly into a properly labelled autosampler vial.
The extract is now ready for analysis. Proceed to Sec. 7.4.
7.3.2Soils, solids, sludges, heavy aqueous suspensions, and non-
aqueous liquids:
Elute 15 mL of the acetonitrile extract through a C-18 reverse phase cartridge, prewashed with 5 mL of acetonitrile. Discard the first 2 mL of eluate and collect the remainder. Pipet 10.0 mL of the clean extract into
a 10 mL graduated glass vial containing 100 μL of ethylene glycol. Place
o
the vial in a heating block set at 50 C, and gently evaporate the extract under a stream of nitrogen (in a fume hood) until only the ethylene glycol keeper remains. Add methanol to the ethylene glycol residue, dropwise, until the total volume is 1.0 mL. (Additional dilution factor = 0.1;
overall dilution factor = 0.5). Using a disposable 0.45 μm filter, filter this extract directly into a properly labelled autosampler vial. The extract is now ready for analysis. Proceed to Sec. 7.4.
7.4Sample Analysis
7.4.1Analyze the samples using the chromatographic conditions,
post-column reaction parameters and instrument parameters given in Secs.
7.4.1.1, 7.4.1.2, 7.4.1.3 and 7.4.1.4. Table 2 provides the retention
times that were obtained under these conditions during method development.
A chromatogram of the separation is shown in Figure 1.
7.4.1.1Chromatographic Conditions (Recommended)
Solvent A:Organic-free reagent water, acidified with
0.4 mL of phosphoric acid per liter of
water
Solvent B:Methanol/acetonitrile (1:1, v/v)
Flow rate: 1.0 mL/min
Injection Volume:20 μL
Solvent delivery system program:
Time Duration
(min)Function Value(min) File
0.00 FR 1.0 0
0.00 B% 10% 0
0.02 B% 80% 20 0
20.02 B%100% 5 0
25.02 B%100% 5 0
30.02 B% 10% 3 0
33.02 B% 10% 7 0
36.02 ALARM 0.01 0
7.4.1.2Post-column Hydrolysis Parameters (Recommended)
Solution:0.05 N aqueous sodium hydroxide
Flow Rate:0.7 mL/min
o
Temperature 95 C
Residence Time:35 seconds (1 mL reaction coil)
7.4.1.3Post-column Derivatization Parameters
(Recommended)
Solution:o-phthalaldehyde/2-mercaptoethanol (Sec.
5.3.1)
Flow Rate:0.7 mL/min
o
Temperature 40 C
Residence time:25 seconds (1 mL reaction coil)
7.4.1.4Fluorometer Parameters (Recommended)
Cell:10 μL
Excitation wavelength:340 nm
Emission waveleng 418 nm cutoff filter
Sensitivity wavelength:0.5 μA
PMT voltage: -800 V
Time constant: 2 sec
7.4.2If the peak areas of the sample signals exceed the calibration range of the system, dilute the extract as necessary and reanalyze the diluted extract.
7.5Calibration:
7.5.1Analyze a solvent blank (20 μL of methanol) to ensure that the
system is clean. Analyze the calibration standards (Sec. 5.4.3), starting
with the 0.5 mg/L standards and ending with the 5.0 mg/L standard. If the
percent relative standard deviation (%RSD) of the mean response factor
(RF) for each analyte does not exceed 20%, the system is calibrated and
the analysis of samples may proceed. If the %RSD for any analyte exceeds
20%, recheck the system and/or recalibrate with freshly prepared
calibration solutions.
7.5.2Using the established calibration mean response factors, check
the calibration of the instrument at the beginning of each day by
analyzing the 2.0 mg/L mixed standard. If the concentration of each analyte falls within the range of 1.70 to 2.30 mg/L (i.e., within + 15% of
the true value), the instrument is considered to be calibrated and the
analysis of samples may proceed. If the observed value of any analyte exceeds its true value by more than + 15%, the instrument must be
recalibrated (Sec. 7.5.1).
7.5.3After 10 sample runs, or less, the 2.0 mg/L standards must be
analyzed to ensure that the retention times and response factors are still
within acceptable limits. Significant variations (i.e., observed concentrations exceeding the true concentrations by more than + 15%) may
require a re-analysis of the samples.
7.6Calculations
7.6.1Calculate each response factor as follows (mean value based on
5 points):
concentration of standard RF =
area of the signal
5
(3 RF )
i i mean RF = RF =
__ 5
5
[(3 RF - RF)] / 4i __
21/2i %RSD of RF = X 100%
__
RF __
7.6.2Calculate the concentration of each N-methylcarbamate as
follows:
μg/g or mg/L = (RF) (area of signal) (dilution factor)
__
8.0QUALITY CONTROL
8.1Before processing any samples, the analyst must demonstrate, through the analysis of a method blank for each matrix type, that all glassware and reagents are interference free. Each time there is a change of reagents, a method blank must be processed as a safeguard against laboratory contamination.
8.2 A QC check solution must be prepared and analyzed with each sample batch that is processed. Prepare this solution, at a concentration of 2.0 mg/L of each analyte, from the 40.0 mg/L mixed QC standard solution (Sec. 5.4.4). The acceptable response range is 1.7 to 2.3 mg/L for each analyte.
8.3Negative interference due to quenching may be examined by spiking the extract with the appropriate standard, at an appropriate concentration, and examining the observed response against the expected response.
8.4Confirm any detected analytes by substituting the NaOH and OPA reagents in the post column reaction system with deionized water, and reanalyze the suspected extract. Continued fluorescence response will indicate that a positive interference is present (since the fluorescence response is not due to the post column derivatization). Exercise caution in the interpretation of the chromatogram.
9.0METHOD PERFORMANCE
9.1Table 1 lists the single operator method detection limit (MDL) for each compound in organic-free reagent water and soil. Seven/ten replicate samples were analyzed, as indicated in the table. See reference 7 for more details.
9.2Tables 2, 3 and 4 list the single operator average recoveries and standard deviations for organic-free reagent water, wastewater and soil. Ten replicate samples were analyzed at each indicated spike concentration for each matrix type.
9.3The method detection limit, accuracy and precision obtained will be determined by the sample matrix.
10.0REFERENCES
1.California Department of Health Services, Hazardous Materials Laboratory,
"N-Methylcarbamates by HPLC", Revision No. 1.0, September 14, 1989.
2.Krause, R.T. Journal of Chromatographic Science, 1978, vol. 16, pg 281.
3.Klotter, Kevin, and Robert Cunico, "HPLC Post Column Detection of
Carbamate Pesticides", Varian Instrument Group, Walnut Creek, CA 94598.
https://www.doczj.com/doc/2e16710239.html,EPA, "Method 531. Measurement of N-Methylcarbomyloximes and N-
Methylcarbamates in Drinking Water by Direct Aqueous Injection HPLC with
Post Column Derivatization", EPA 600/4-85-054, Environmental Monitoring and Support Laboratory, Cincinnati, OH 45268.
https://www.doczj.com/doc/2e16710239.html,EPA, "Method 632. The Determination of Carbamate and Urea Pesticides in
Industrial and Municipal Wastewater", EPA 600/4-21-014, Environmental Monitoring and Support Laboratory, Cincinnati, OH 45268.
6.Federal Register, "Appendix B to Part 136 - Definition and Procedure for
the Determination of the Method Detection Limit - Revision 1.11", Friday, October 26, 1984, 49, No. 209, 198-199.
7.Okamoto, H.S., D. Wijekoon, C. Esperanza, J. Cheng, S. Park, J. Garcha, S.
Gill, K. Perera "Analysis for N-Methylcarbamate Pesticides by HPLC in Environmental Samples", Proceedings of the Fifth Annual USEPA Symposium on Waste Testing and Quality Assurance, July 24-28, 1989, Vol. II, 57-71.
a
ELUTION ORDER, RETENTION TIMES AND
SINGLE OPERATOR METHOD DETECTION LIMITS
Method Detection Limits b Compound Retention Organic-free
Time Reagent Water Soil
(min) (μg/L)(μg/kg)
_______________________________________________________________________________
c c
Aldicarb Sulfone 9.59 1.944
Methomyl (Lannate) 9.59 1.712
3-Hydroxycarbofuran12.70 2.610c
Dioxacarb13.50 2.2 >50c
c c
Aldicarb (Temik)16.05 9.412
Propoxur (Baygon)18.06 2.417
Carbofuran (Furadan)18.28 2.022
Carbaryl (Sevin)19.13 1.731
d
-Naphthol20.30 - -
Methiocarb (Mesurol)22.56 3.132
Promecarb23.02 2.517
________________________________________________________________________________ a
See Sec. 7.4 for chromatographic conditions
b
MDL for organic-free reagent water, sand, soil were determined by analyzing 10 low concentration spike replicate for each matrix type (except where noted). See reference 7 for more details.
c
MDL determined by analyzing 7 spiked replicates.
d
Breakdown product of Carbaryl.
a
PRECISION DATA FOR ORGANIC-FREE REAGENT WATER
Compound Recovered% Recovery SD%RSD
_____________________________________________________________________________ Aldicarb Sulfone22575.0 7.28 3.24 Methomyl (Lannate)24481.3 8.34 3.42
3-Hydroxycarbofuran21070.0 7.85 3.74 Dioxacarb24180.3 8.53 3.54 Aldicarb (Temik)22474.7 13.5 6.03 Propoxur (Baygon)23277.3 10.6 4.57 Carbofuran (Furadan)23979.6 9.23 3.86 Carbaryl (Sevin)24280.7 8.56 3.54 Methiocarb (Mesurol)23177.0 8.09 3.50 Promecarb22775.7 9.43 4.1
_______________________________________________________________________________ a
Spike Concentration = 300 μg/L of each compound, n = 10
a
PRECISION DATA FOR WASTEWATER
Compound Recovered% Recovery SD%RSD
______________________________________________________________________________
Aldicarb Sulfone23578.317.67.49 Methomyl (Lannate)24782.329.912.10 3-Hydroxycarbofuran25183.725.410.11
b
Dioxacarb - - - Aldicarb (Temik)25886.016.4 6.36 Propoxur (Baygon)26387.716.7 6.47 Carbofuran (Furadan)26287.315.7 5.99 Carbaryl (Sevin)26287.317.2 6.56 Methiocarb (Mesurol)25484.719.97.83 Promecarb26387.715.1 5.74 ________________________________________________________________________________ a
Spike Concentration = 300 μg/L of each compound, n = 10
b
No recovery
a
PRECISION DATA FOR SOIL
Compound Recovered% Recovery SD%RSD
______________________________________________________________________________
Aldicarb Sulfone 1.5778.50.069 4.39 Methomyl (Lannate) 1.4874.00.086 5.81 3-Hydroxycarbofuran 1.6080.00.071 4.44 Dioxacarb 1.5175.50.073 4.83 Aldicarb (Temik) 1.2964.50.14211.0 Propoxur (Baygon) 1.3366.50.1269.47 Carbofuran (Furadan) 1.4673.00.092 6.30 Carbaryl (Sevin) 1.5376.50.076 4.90 Methiocarb (Mesurol) 1.4572.50.071 4.90 Promecarb 1.2964.70.1249.61 _______________________________________________________________________________ a
Spike Concentration = 2.00 mg/kg of each compound, n = 10
1.00 μg/mL EACH OF:
1.ALDICARB SULFONE 6.PROPOXUR
2.METHOMYL7.CARBOFURAN
3.3-HYDROXYCARBOFURAN8.CARBARYL
4.DIOXACARB9.METHIOCARB
5.ALDICARB10.PROMECARB
METHOD 3541 AUTOMATED SOXHLET EXTRACTION 1.0SCOPE AND APPLICATION 1.1Method 3541 describes the extraction of organic analytes from soil, sediment, sludges, and waste solids. The method uses a commercially available, unique, three stage extraction system to achieve analyte recovery comparable to Method 3540, but in a much shorter time. There are two differences between this extraction method and Method 3540. In the initial extraction stage of Method 3541, the sample-loaded extraction thimble is immersed into the boiling solvent. This ensures very rapid intimate contact between the specimen and solvent and rapid extraction of the organic analytes. In the second stage the thimble is elevated above the solvent, and is rinse-extracted as in Method 3540. In the third stage, the solvent is evaporated, as would occur in the Kuderna-Danish (K-D) concentration step in Method 3540. The concentrated extract is then ready for cleanup (Method 3600) followed by measurement of the organic analytes. 1.2The method is applicable to the extraction and concentration of water insoluble or slightly water soluble polychlorinated biphenyls (PCBs) in preparation for gas chromatographic determination using either Method 8080 or 8081. This method is applicable to soils, clays, solid wastes and sediments containing from 1 to 50 μg of PCBs (measured as Arochlors) per gram of sample. It has been statistically evaluated at 5 and 50 μg/g of Arochlors 1254 and 1260, and found to be equivalent to Method 3540 (Soxhlet Extraction). Higher concentrations of PCBs are measured following volumetric dilution with hexane. 1.3The method is also applicable the extraction and concentration of semivolatile organics in preparation for GC/MS analysis by Method 8270 or by analysis using specific GC or HPLC methods. 2.0SUMMARY OF METHOD 2.1PCBs: Moist solid samples (e.g., soil/sediment samples) may be air-dried and ground prior to extraction or chemically dried with anhydrous sodium sulfate. The prepared sample is extracted using 1:1 (v/v) acetone:hexane in the automated Soxhlet following the same procedure as outlined for semivolatile organics in Sec. 2.1. The extract is then concentrated and exchanged into pure hexane prior to final gas chromatographic PCB measurement. 2.2Other semivolatile organics: A 10-g solid sample (the sample is pre-mixed with anhydrous sodium sulfate for certain matrices) is placed in an extraction thimble and usually extracted with 50 mL of 1:1 (v/v) acetone/hexane for 60 minutes in the boiling extraction solvent. The thimble with sample is then raised into the rinse position and extracted for an additional 60 minutes. Following the extraction steps, the extraction solvent is concentrated to 1 to 2 mL. CD-ROM3541 - 1Revision 0 September 1994
主要发达国家环保产业发展概况 一、美国 （一）产业分类情况 美国环保产业分为环保服务、环保设备和环境资源三大类。 （二）产业发展概况 美国现在也在面临和处理一系列挑战，包括水方面、气候变化、细菌、污染、负氧，以及水供应。美国环保局现在也在动用自己的力量重整整个水资源系统，不管是学术界还是市民，都参与到了环保的行业当中。没有人能够再袖手旁观了。
美国环保技术和设备可以帮助解决水跟土壤的问题，其实最主要的是淤泥积土。每一次下雨的时候，空气当中的污染物都会进入到的水中，包括河流，包括大江，而随着水的流动，所有的这些分子，还有污染物都会流向其他地方，所以美国现在的环保部对于处理水污染方面的技术是的重点。要减排，减少能源的消耗，同时要解决这些水方面的问题。 美国技术和设备方面的优势。美国现在已经成为全球在环境保护技术和设备方面领先的国家，美国的研发工作做得非常到位，美国使用目前的研发成果来开发新的技术，例如水资源处理，还有其他诊断和探寻设备，还有在细菌、濒危物种、化肥、杀虫剂等方面的一些技术和设备。其实，目前中国的发展也非常快，在环境方面也解决了很多的问题。面临着新一代的环境系统，在基础设施建设方面也有着更多的优势，所以创新是一个很好的推动力量，只有创新才能推动经济的长远发展，中国和全球各个国家都已经意识到了这一点。 在现代经济当中，各个国家都在鼓励新技术的创新，新技术同时也推动了经济发展，新技术是经济发展的燃料剂和助推剂，可以影响到每个人，也会影响到每天的商业决策。目前有很多数据讲的都是一些新兴企业的产品、市场、知识产权的保护，这些议题是所有全球企业都面临的议题，而同时在这样的环境当中，美国有不断的技术、产品和服务推陈出新，同时美国有着新的体系、新的标准、新的数据，还有新的发现、分析的结果，这些能够更好的保护隐私和安全。关于气候变化和天气管理的政府机构都会对进行评估，对大气、水资源等去进行环评。另外很多企业和国家都面临着非常严峻的供应链的挑战，都会考虑所有的这些环境因素，未来发展的能力已经到了一个临界点，甚至现在天灾也会带来非常严重的后果，例如地震等，另外还有全球一些地区的冲突，所以货物在运输时所造成的损失也越来越频繁，每年因为这些因素导致的货物损失高达数亿美元，有
美国EPA通用土壤筛选值
美国EPA通用土壤筛选值
CAS 号污染 物 土壤（mg/kg） 地下 （μg/L 居 住 备 注 工 业 备 注 基于 地下 水保 护 饮用 水 1 +04 E+0 5 +00 +04 75-86- 5 丙酮氰 醇 2.0E +02 n 2.1 E+0 3 n 1.2E -02 5.8E +01 75-05- 8 乙腈 8.7E +02 n 3.7 E+0 3 n 2.6E -02 1.3E +02 98-86- 2 乙酰苯 7.8E +03 ns 1.0 E+0nms 1.1E +00 3.7E +03
CAS 号污染 物 土壤（mg/kg） 地下 （μg/L 居 住 备 注 工 业 备 注 基于 地下 水保 护 饮用 水 -8 -01 E-0 1 -06 -02 79-06- 1 丙烯酰 胺 2.3E -01 c 3.4 E+0 c 9.1E -06 4.3E -02 79-10- 7 丙烯酸 3.0E +04 n 2.9 E+0 5 nm 3.7E +00 1.8E +04 107-13 -1 丙烯腈 2.4E -01 c* 1.2 E+0c* 9.9E -06 4.5E -02
CAS 号污染 物 土壤（mg/kg） 地下 （μg/L 居 住 备 注 工 业 备 注 基于 地下 水保 护 饮用 水 60-8 +00 E+0 1 -04 +00 116-06 -3 涕灭威 6.1E +01 n 6.2 E+0 2 n 9.1E -03 3.7E +01 1646-8 8-4 涕灭威 砜 6.1E +01 n 6.2 E+0 2 n 8.0E -03 3.7E +01 309-00 -2 艾氏剂 2.9E -02 c* 1.0 E-0 c 6.5E -04 4.0E -03
美国环境保护制度 篇一：环保：美国的垃圾管理机制 环境产业研究 第19期 20XX年7月27日全国工商联环境服务业商会 美国垃圾管理机制 ——商业模式下的系统化垃圾管理 作为经济大国的美国同样也是一个消费大国，持续增长的垃圾排放对其环境质量也造成了极大地威胁。据美国环境署最新公布数字显示，20XX年，美国城市固体垃圾产量达2.5亿吨，如果用卡车运送这些垃圾，组成的车队足以绕地球6圈。但是，在清晰的垃圾管理战略的指导下，美国垃圾处理产业得到了快速的发展，目前已经形成了系统化的垃圾管理商业模式，足以应对日益增长的垃圾排放量。 一、美国垃圾管理概况 （一）垃圾管理战略 美国确定的固体废弃物治理战略方针是实施源头控制政策，从生产阶段抑制废物的产生，减少使用成为污染源的物质；最大限度地实施废物资源回收，通过堆肥、焚烧热能回收利用实现废物资源、能源的再生利用，最后进行卫生填埋。 近年来，美国一直坚持垃圾减量、分流和再利用这个主题，以废物变
资源、废物变能源（焚烧和生物制肥）作为垃圾治理的主导方向，制定的20XX年的垃圾处理目标是：回收利用（包括直接回收、路边分类、堆肥、综合利用等）50%，填埋40%，焚烧10%。 为实现这些目标，美国各州普遍采取垃圾源头控制和减量措施，提出垃圾分流的概念，将食品垃圾、庭院垃圾和餐厨垃圾等按类别作为分流目标，直接进入适用的处理程序，既促进了不同成分垃圾的分类处理，也促进了资源的循环再生，垃圾处理已经形成了比较系统的模式。美国垃圾管理战略已取得了明显的成效：垃圾填埋已经从1980年的89%降为20XX年的54%，而垃圾资源回收再利用则从1980年的9.6%提高到了20XX年的33.4%，垃圾焚烧处理从1980年的1.8%上升到了20XX年的12.6%。 （二）垃圾处理方式的演变 全美国1988年共有垃圾填埋场7924个，1999年为2514个，20XX 年下降到1767个，20XX年又降为1654个，总体上呈下降趋势。垃圾焚烧厂数量从1997年的131座下降到20XX年的101座，包括焚烧和生物制能的废物变能源工厂。20XX年全美国共有废物定点回收场地12694个，路边资源垃圾分类回收项目也从1989年的1042个增长 到20XX年的7689个，成为废物资源回收的重要组成部分。 目前在美国的不同地区，垃圾处理方式的比例各不相同。如：新英格兰地区的填埋占36%，回收占33%，焚烧占31%。美国西部的填埋
9066 1 CD-ROM Revision 0 Date September 1986 METHOD 9066PHENOLICS (COLORIMETRIC, AUTOMATED 4-AAP WITH DISTILLATION) 1.0SCOPE AND APPLICATION 1.1This method is applicable to the analysis of ground water and of drinking, surface, and saline waters. 1.2The method is capable of measuring phenolic materials from 2 to 500ug/L in the aqueous phase using phenol as a standard. 2.0SUMMARY OF METHOD 2.1This automated method is based on the distillation of phenol and subsequent reaction of the distillate with alkaline ferricyanide (K Fe(CN)) and 364-amino-antipyrine (4-AAP) to form a red complex which is measured at 505 or 520 nm. 3.0INTERFERENCES 3.1Interferences from sulfur compounds are eliminated by acidifying the sample to a pH of < 4.0 with H SO and aerating briefly by stirring. 243.2Oxidizing agents such as chlorine, detected by the liberation of iodine upon acidification in the presence of potassium iodide, are removed immediately after sampling by the addition of an excess of ferrous ammonium sulfate (5.5). If chlorine is not removed, the phenolic compounds may be partially oxidized and the results may be low. 3.3Background contamination from plastic tubing and sample containers is eliminated by filling the wash receptacle by siphon (using Kel-F tubing) and using glass tubes for the samples and standards. 4.0APPARATUS AND MATERIALS 4.1Automated continuous-flow analytical instrument: 4.1.1 Sampler : Equipped with continuous mixer.4.1.2 Manifold .4.1.3 Proportioning pump II or III .4.1.4 Heating bath with distillation coil .4.1.5Distillation head .
METHOD 8318 N-METHYLCARBAMATES BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (HPLC) 1.0SCOPE AND APPLICATION 1.1Method 8318 is used to determine the concentration of N-methylcarbamates in soil, water and waste matrices. The following compounds can be determined by this method: _______________________________________________________________________________ Compound Name CAS No.a ________________________________________________________________________________ Aldicarb (Temik) 116-06-3 Aldicarb Sulfone 1646-88-4 Carbaryl (Sevin) 63-25-2 Carbofuran (Furadan) 1563-66-2 Dioxacarb 6988-21-2 3-Hydroxycarbofuran16655-82-6 Methiocarb (Mesurol) 2032-65-7 Methomyl (Lannate)16752-77-5 Promecarb 2631-37-0 Propoxur (Baygon) 114-26-1 ________________________________________________________________________________ a Chemical Abstract Services Registry Number. 1.2The method detection limits (MDLs) of Method 8318 for determining the target analytes in organic-free reagent water and in soil are listed in Table 1. 1.3This method is restricted to use by, or under the supervision of, analysts experienced in the use of high performance liquid chromatography (HPLC) and skilled in the interpretation of chromatograms. Each analyst must demonstrate the ability to generate acceptable results with this method. 2.0SUMMARY OF METHOD 2.1N-methylcarbamates are extracted from aqueous samples with methylene chloride, and from soils, oily solid waste and oils with acetonitrile. The extract solvent is exchanged to methanol/ethylene glycol, and then the extract is cleaned up on a C-18 cartridge, filtered, and eluted on a C-18 analytical column. After separation, the target analytes are hydrolyzed and derivatized post-column, then quantitated fluorometrically. 2.2Due to the specific nature of this analysis, confirmation by a secondary method is not essential. However, fluorescence due to post-column derivatization may be confirmed by substituting the NaOH and o-phthalaldehyde solutions with organic-free reagent water and reanalyzing the sample. If
METHOD 3520C CONTINUOUS LIQUID-LIQUID EXTRACTION 1.0SCOPE AND APPLICATION 1.1This method describes a procedure for isolating organic compounds from aqueous samples. The method also describes concentration techniques suitable for preparing the extract for the appropriate determinative steps described in Sec. 4.3 of Chapter Four. 1.2This method is applicable to the isolation and concentration of water-insoluble and slightly soluble organics in preparation for a variety of chromatographic procedures. 1.3Method 3520 is designed for extraction solvents with greater density than the sample. Continuous extraction devices are available for extraction solvents that are less dense than the sample. The analyst must demonstrate the effectiveness of any such automatic extraction device before employing it in sample extraction. 1.4This method is restricted to use by or under the supervision of trained analysts. Each analyst must demonstrate the ability to generate acceptable results with this method. 2.0SUMMARY OF METHOD 2.1 A measured volume of sample, usually 1 liter, is placed into a continuous liquid-liquid extractor, adjusted, if necessary, to a specific pH (see Table 1), and extracted with organic solvent for 18 - 24 hours. 2.2The extract is dried, concentrated (if necessary), and, as necessary, exchanged into a solvent compatible with the cleanup or determinative method being employed (see Table 1 for appropriate exchange solvents). 3.0INTERFERENCES 3.1Refer to Method 3500. 3.2The decomposition of some analytes has been demonstrated under basic extraction conditions required to separate analytes. Organochlorine pesticides may dechlorinate, phthalate esters may exchange, and phenols may react to form tannates. These reactions increase with increasing pH, and are decreased by the shorter reaction times available in Method 3510. Method 3510 is preferred over Method 3520 for the analysis of these classes of compounds. However, the recovery of phenols may be optimized by using Method 3520 and performing the initial extraction at the acid pH. 4.0APPARATUS AND MATERIALS 4.1Continuous liquid-liquid extractor - Equipped with polytetrafluoroethylene (PTFE) or glass connecting joints and stopcocks requiring no lubrication (Kontes 584200-0000, 584500-0000, 583250-0000, or equivalent). CD-ROM3520C - 1Revision 3 December 1996
潜在致癌剂的危害等 级 致癌性是筛选优先污染物的重要依据之一，下表列出了美国EPA公布的200种致癌剂的危害等级。其中的参数含义为： 1、证据的充分程度（Degree of Evidence） 化学品对人体的致癌性证据之充分程度可以分为下列几类。 （1）证据充分，指致癌剂和人体癌症之间有因果关系。 （2）证据有限，指能提供一些可信的致癌性证据，但证据尚有限，还需作进一步补充。 （3）证据不充分，可能有3种情况，①能获取的致癌性数据很少；②与证据有关的研究尚不能排除偶然性、误差及混淆等情况；③研究结果无致癌性证据。 根据动物实验取得的致癌性证据的充分程度可分4级。 1级，致癌性证据充分。 2级，致癌性证据有限。 3级，致癌性证据不充分。 4级，无致癌性证据。 2、IARC标准分组 国际癌症研究所 （International Agency for research on cancer，简称IARC）将人类的肿瘤风险分为3组。 1组：列在此组内的化学品属致癌物，流行病学和暴露实验均已肯定，基致癌证据是充分的。 2组：化学品可能对人体有致癌性。其中有的对人体的致癌性证据几乎是“充分的”，另一类的证据不够充分。证据程度较高的为A组，较低的为B 组。例如，2A指对人体的致癌性至少存在着有限证据。当动物证据充分而人体数据不充分时，归入2B。 3组：列在本组中的化学品对人类没有致癌性。
3、潜力因素值F（Potency Factor Estimate） 潜力因素值F定义为1/ED 10。ED 10 等于10%终身致癌风险的致癌剂剂量。 F可以和致癌性的确认证据一起，用来划分化学品潜在致癌性的危险等级。 4、潜力因素分组（Potency factor Grouping） 由于潜力因素值F可表示致癌危险性的相对大小，因而，可将潜在致癌剂的相对潜力因素分为4组。潜力因素最高的化学品分在1组，中等潜力因素的为2组，低潜力因素的为3组，最低潜力因素的为4组。 5、致癌危害等级（Cancer Hazard Ranking） 根据人和动物试验所取得的致癌性证据，结合潜力因素分组数据，可将化学品致癌危害等级分为高、中、低3级。
DETERMINATION OF ETHYLENE THIOUREA (ETU) IN WATER USING GAS CHROMATOGRAPHY WITH A NITROGEN-PHOSPHORUS DETECTOR Revision 1.0 December 1992 D.J. Munch and R.L. Graves T.M. Engel and S.T. Champagne Battelle, Columbus Division ENVIRONMENTAL MONITORING SYSTEMS LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268 509-1
DETERMINATION OF ETHYLENE THIOUREA (ETU) IN WATER USING GAS CHROMATOGRAPHY WITH A NITROGEN-PHOSPHORUS DETECTOR 1.0SCOPE AND APPLICATION 1.1This method utilizes gas chromatography (GC) to determine ethylene thiourea (ETU, Chemical Abstracts Registry No. 96-45-7) in water. 1.2This method has been validated in a single laboratory during development. 1 The method detection limit (MDL) has been determined in reagent water and is listed in Table 2. Method detection limits may vary among laboratories, depending upon the analytical instrumentation used and the experience of the analyst. In addition to the work done during the development of this method and its use in the National Pesticide Survey, an interlaboratory method validation study of this method has been conducted. 1.3This method is restricted to use by or under the supervision of analysts experienced in the use of GC and in the interpretation of gas chromatograms. Each analyst must demonstrate the ability to generate acceptable results with this method using the procedure described in Section 9.3. 1.4When a tentative identification of ETU is made using the recommended primary GC column (Section 6.7.1), it must be confirmed by at least one additional qualitative technique. This technique may be the use of the confirmation GC column (Section 6.7.2) with the nitrogen-phosphorus detector or analysis using a gas chromatograph/mass spectrometer (GC/MS). 2.0SUMMARY OF METHOD 2.1The ionic strength and pH of a measured 50 mL aliquot of sample are adjusted by addition of ammonium chloride and potassium fluoride. The sample is poured onto an Extrelut column. ETU is eluted from the column in 400 mL of methylene chloride. A free radical scavenger is then added in excess to the eluate. The methylene chloride eluant is concentrated to a volume of 5 mL after solvent substitution with ethyl acetate. Gas chromatographic conditions are described which permit the separation and measurement of ETU with a nitrogen-phosphorus detector (NPD). 3.0DEFINITIONS 3.1Artificial Ground Water -- An aqueous matrix designed to mimic a real ground water sample. The artificial ground water should be reproducible for use by others. 509-2
1,2-DIBROMOETHANE (EDB), 1,2-DIBROMO-3-CHLORO-PROPANE (DBCP), AND 1,2,3-TRICHLOROPROPANE (123TCP) IN WATER BY MICROEXTRACTION AND GAS CHROMATOGRAPHY Revision 1.1 Edited by J.W. Munch (1995) T. W. Winfield - Method 504, Revision 1.0 (1986) T. W. Winfield - Method 504, Revision 2.0 (1989) James W. Eichelberger - Method 504.1, Revision 1.0 (1993) NATIONAL EXPOSURE RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 45268 504.1-1
1,2-DIBROMOETHANE (EDB), 1,2-DIBROMO-3-CHLOROPROPANE (DBCP), AND 1,2,3-TRICHLOROPROPANE (123TCP) IN WATER BY MICROEXTRACTION AND GAS CHROMATOGRAPHY 1.0SCOPE AND APPLICATION 1-3 1.1This method is applicable to the determination of the following compounds in finished drinking water and groundwater: Chemical Abstract Services Analyte Registry Number 1,2-Dibromoethane106-93-4 1,2-Dibromo-3-Chloropropane96-12-8 1,2,3-Trichloropropane96-18-4 1.2For compounds other than the above mentioned analytes, or for other sample sources, the analyst must demonstrate the usefulness of the method by collecting precision and accuracy data on actual samples and provide qualitative confirmation of results by gas chromatography/mass spectrometry (GC/MS).4 5 1.3The experimentally determined method detection limits (MDL) for EDB and DBCP were calculated to be 0.01 μg/L and the MDL for 123TCP was calculated to be 0.02 μg/L. The method has been useful for these analytes over a concentration range from approximately 0.03-200 μg/L. Actual detection limits are highly dependent upon the characteristics of the gas chromatographic system used. 2.0SUMMARY OF METHOD 2.1Thirty-five mL of sample are extracted with 2 mL of hexane. Two μL of the extract are then injected into a gas chromatograph equipped with a linearized electron capture detector for separation and detection. Analytes are quantitated using procedural standard calibration (Section 3.12). 2.2The extraction and analysis time is 30-50 minutes per sample depending upon the analytical conditions chosen. 2.3Confirmatory evidence should be obtained for all positive results. This data may be obtained by using retention data from a dissimilar column, or when concentrations are sufficiently high by GC/MS. Purge and trap techniques using Methods 502.2 or 524.2 may also be used. Confirmation of all positive results of EDB are especially important, because of the potential for misidentification of dibromochloromethane (DBCM) as EDB. 504.1-2
METHOD 9012B TOTAL AND AMENABLE CYANIDE (AUTOMATED COLORIMETRIC, WITH OFF-LINE DISTILLATION) 1.0 SCOPE AND APPLICATION 1.1 This method is used to determine the concentration of inorganic cyanide (CAS Registry Number 57-12-5) in wastes or leachate. This method detects inorganic cyanides that are present as either soluble salts or complexes. It is used to determine values for both total cyanide and cyanide amenable to chlorination. The "reactive" cyanide content of a waste is not determined by this method. Refer to 40 CFR 261.23 for information on the characteristic of reactivity. 2.0 SUMMARY OF METHOD 2.1 The cyanide, as hydrocyanic acid (HCN), is released from samples containing cyanide by means of a reflux-distillation operation under acidic conditions and absorbed in a scrubber containing sodium hydroxide solution. The cyanide ion in the absorbing solution is then determined by automated UV colorimetry. 2.2 In the automated colorimetric measurement, the cyanide is converted to cyanogen chloride (CNCl) by reaction with Chloramine-T at a pH less than 8 without hydrolyzing to the cyanate. After the reaction is complete, color is formed on the addition of pyridine-barbituric acid reagent. The concentration of NaOH must be the same in the standards, the scrubber solutions, and any dilution of the original scrubber solution to obtain colors of comparable intensity. 3.0 INTERFERENCES 3.1Interferences are eliminated or reduced by using the distillation procedure. Chlorine and sulfide are interferences in this method. 3.2Oxidizing agents such as chlorine decompose most cyanides. Chlorine interferences can be removed by adding an excess of sodium arsenite to the waste prior to preservation and storage of the sample to reduce the chlorine to chloride which does not interfere. 3.3Sulfide interference can be removed by adding an excess of bismuth nitrate to the waste (to precipitate the sulfide) before distillation. Samples that contain hydrogen sulfide, metal sulfides, or other compounds that may produce hydrogen sulfide during the distillation should be treated by the addition of bismuth nitrate. 3.4High results may be obtained for samples that contain nitrate and/or nitrite. During the distillation, nitrate and nitrite will form nitrous acid, which will react with some organic compounds to form oximes. These compounds once formed will decompose under test conditions to generate HCN. The possibility of interference of nitrate and nitrite is eliminated by pretreatment with sulfamic acid just before distillation. Nitrate and nitrite are interferences when present at levels higher than 10 mg/L and in conjunction with certain organic compounds.