FAST ANALYTICAL TECHNIQUES FOR HAZARDOUS WASTE ANALYSIS

Rafael Infante Mndez*1, Mara Vidal1, and Yamilet Sampoll2

1Beckton Environmental Laboratories, 192 Villa Street,Ponce, PR 00731

2Chemistry Department, Pontifical Catholic University ofPuerto Rico. Ponce, Puerto Rico 00732

ABSTRACT

A hazardous waste is identified using four characteristics:ignigtability, corrosivity, reactivity, and leaching toxicity. Thetoxicity characteristic leaching procedure (TCLP) is aimed todetermine the mobility of both organic and inorganic analytespresent, and identifies 25 semivolatiles organic compoundsincluding organic acids, base/neutrals, pesticides, and herbicides.Liquid-liquid extraction using methylene chloride is the methodemployed for the extraction of semivolatile organics from theleaching fluid. This procedure is time consuming, labor intensive,and requires large volume of potentially toxic solvents. Tofacilitate the extraction and concentration steps, the use of C8and C18 Empore extraction disks have been explored. The use of thedisk improve the extraction procedure and minimize the use ofsolvents. Application to the TCLP pesticides and herbicides will bepresented and compared to the traditionally approach.

Keywords: Hazardous wastes, TCLP, solid phase extraction,pesticides, herbicides.

INTRODUCTION

The Resource Conservation and Recovery Act (RCRA) direct theEnvironmental Protection Agency (EPA) to set minimum standards forhandling hazardous wastes. RCRA requires EPA to identify thosewastes which, if managed improperly, could pose a hazard to healthor the environment. The EPA developed two categories for groupinghazardous wastes: (1) those listed, and (2) those that exhibit oneof four characteristics- ignigtability, corrosivity, reactivity,and toxicity. Of these toxicity is unique in that it is used toidentify wastes which could potentially leach toxic substances intothe groundwater supply.

To determine the toxicity characteristic of a waste, aleaching procedure was developed to simulate the environment thatmight exists when industrial solid wastes are co-disposed withsolid wastes in a municipal landfill. This test is called theToxicity Characteristic Leaching Procedure (TCLP). The TCLPrepresent a worse case scenario for mismanagement of hazardouswastes in a landfill. In the landfills, carboxylic acids, such as

acetic acid, are generated and could extract heavy metals andorganic compounds from the waste and produce a toxic leachate. TheTCLP test uses acetic acid solution to simulate the leachingprocess. Table 1 list the semivolatile organic compounds that mustbe analyzed in the TCLP extraction fluid.

Table 1. Target Toxic Organic Compounds Determined in TCLPProcedure

EPA Hazardous Contaminant RegulatoryWaste Number level, mg/L

I. Acids and Base/Neutrals Organic Compounds

D023 o-Cresol 200.0bD024 m-Cresol 200.0bD025 p-Cresol 200.0bD026 Cresol 200.0bD030 2,4-Dinitrotoluene 0.13aD032 Hexachlorobenzene 0.13aD033 Hexachlorobutadiene 0.5D034 Hexachloroethane 3.0D036 Nitrobenzene 2.0D037 Pentachlorophenol 100.0D038 Pyridine 5.0aD011 2,4,5-Trichlorophenol 400.0D042 2,4,6-Trichlorophenol 2.0

II. Pesticides

D020 Chlordane 0.03D012 Endrin 0.02D031 Heptachlor (and its epoxide) 0.008D013 Lindane 0.4D014 Methoxychlor 10.0D015 Toxaphene 0.5

III. Herbicides

D016 2,4-D 10.0D017 2,4,5-TP (Silvex) 1.0------------a Quantitation limit is greater than the calculated regulatory

level. The quantitation limit therefore becomes the regulatorylevel.

b If o-, m-, and p-cresol concentration cannot bedifferentiated, the total cresol (D026) concentration is used.The regulatory level of total cresol is 200.0 mg/L.

The organic semivolatile TCLP fraction are generally extractedfrom the TCLP fluid or water matrices using an organic solvent,which may undergo further concentration, replacement, and/orderivatization before being analyzed by gas chromatographic

methods. This procedure is usually time consuming, requires the useof large quantities of solvent and other suspected carcinogenicreagents, is subject to contamination (interferences and falsepositives), and/or loss of sample integrity, allows for possibleformation of emulsions, and presents many difficulties for fieldapplications (such as the large size of the extractors, the needfor a constant control of the stirring process, and the low flowrates required for good recovery). Solid supports, especiallyoctadecyl (C-18) bonded to porous silica, have been used for solidphase extraction of organic components from water solutions (Junkand Richard, 1988). Applications of solid phase extraction toenvironmental waters have been more limited. Excellent recoverieshave been reported for hydrophobic compounds and only in cases ofmore soluble compounds, such as phenol, did recoveries decrease toless than 50%.

Earlier work conducted in our laboratory (Infante and Prez,1991; Infante, Gutierrez, and Prez, 1992) developed sensitive andspecific analytical methodology for monitoring acidic chlorinatedcompounds in drinking water. The method was based on solid phaseextraction. The overall accuracy and precision were comparable toother methods used for compliance purposes. The detection limit wasin the low ng/L range. Possible interferences that can overlaptarget compounds were removed by washing the extraction cartridgewith hexane prior to eluting the target compounds with methylenechloride. The sample preparation method proved to be an effectivemethod for sample reservation. Degradation of the sample componentswas not observed for periods extending several weeks.

Presented here are the results of the application of solidphase extraction using Empore extraction disks to the TCLPpesticides and herbicides fractions. The TCLP fluid containing thetarget analytes is passed through a 47 mm Empore disk that trapsthe compounds. The disk is then eluted with a small quantity ofsolvent, which undergo further concentration, solvent exchange, andderivatization using diazomethane prior to analysis by gaschromatography with electron capture detector. This method is muchmore simple than the liquid-liquid extraction method and uses verylittle glassware. It does not use much solvent or take lot of time,furthermore it can be potentially automated. Fewer steps means lesssample loss and fewer artifacts introduced. This sample preparationtechnique is specially suited for an environmental servicelaboratory environment were large quantities of samples areprocessed daily.

EXPERIMENTAL

Target compounds utilized were Chlordane, Endrin, Heptachlor(and its epoxide), Lindane, Methoxychlor, Toxaphene, 2,4-D, andSilvex. The internal standards utilized was chloroxylene,decachlorobiphenyl was used as surrogate standard. Standardsolutions containing multiple analytes, and the internal standardwere prepared from pure compounds or from certified standardsolutions. Aliquot of these solutions were used to spike organic

free TCLP fluid. Calibration solutions, at five concentrations,were prepared in methylene chloride. Response factor weredetermined at this concentration range and found to be constant(

RESULTS AND DISCUSSION

To demonstrate the feasibility of utilizing the Emporeextraction disk for sample preparation samples of a laboratory,fortified TCLP blank fluid, containing each analyte of concern at aconcentration of 5 mg/L were analyzed following the proceduredescribed before. Table 2 summarized the results for the C8 Emporedisk using methylene chloride as the extraction solvent. Recoveriesranged from below 10% to close to 80% and were very much affectedby the extraction fluid pH.

Table 2. Recovery of pesticides from TCLP extraction fluids usingC8 Empore extraction disks

% Recovery % RecoveryCompound (fluid #1) (fluid #2)

Chlordane 2.8 7.5Endrin 23.4 59.9Heptachlor 27.6 76.9Heptachlor epoxide 18.1 53.8Lindane 15.8 68.3Methoxychlor 9.3 14.6Toxaphene 25.7 17.2----------------------------------

To determine the effect of the matrix pH on the recovery oftarget analytes, the pH was adjusted before the extraction step.Recoveries are shown in Tables 3 and 4. Recoveries for most of thetarget analytes improved by lowering the pH to 2 before theextraction. Further pH lowering did not improved the recoveries, onthe contrary there were worse. This is probably due to degradationof the silica surface at the low pH thus lowering its capability ofholding the analyte.

Table 3. Recovery of pesticides from TCLP extraction fluid # 1 atdifferent pH using C8 Empore extraction disks.

Compound pH= 4.9 pH= 2.1 pH= 1.5

Chlordane 2.8 12.5 4.8Endrin 23.4 40.0 30.2Heptachlor 27.6 28.3 25.3Heptachlor epoxide 18.1 35.0 28.8Lindane 15.8 * 37.6Methoxychlor 9.3 10.6 20.0Toxaphene 25.7 * 27.2---------------------------------------------

Table 4. Recovery of pesticides from TCLP extraction fluid # 2 atdifferent pH using C8 Empore extraction disks.

Compound pH= 2.8 pH= 1.2

Chlordane 7.5 8.1Endrin 59.9 62.0Heptachlor 76.9 44.3Heptachlor epoxide 53.8 58.7Lindane 68.3 37.0Methoxychlor 14.0 44.0Toxaphene 17.2 22.1-----------------------------------

To determine the effect on the solvent strength on therecovery of target analyte, two different solvents were employed:methylene chloride and methylene chloride\ethyl acetate (1:1).Tables 5 and 6 shows the comparison of both solvents on the twodifferent extraction fluids. The methylene chloride/ethyl acetatesignificantly improved the recovery specially for Lindane,Metoxychlor and Chlordane.

Table 5. Recovery of pesticides from TCLP extraction fluid # 1using different extraction solvents on the C8 Emporeextraction disks.

Methylene Methylene chloride/Compound chloride Ethyl acetate

Chlordane 2.8 82.2Endrin 23.4 87.5Heptachlor 27.6 85.0Heptachlor epoxide 18.1 72.5Lindane 15.8 125.0Methoxychlor 9.3 142.0Toxaphene 25.7 *--------------------------------------------------

Table 6. Recovery of pesticides from TCLP extraction fluid # 2using different extraction solvents on the C8 Emporeextraction disks.

Methylene Methylene chloride/Compound chloride Ethyl acetate

Chlordane 7.5 98.7Endrin 59.9 52.8Heptachlor 76.9 60.0Heptachlor epoxide 53.8 51.8Lindane 68.3 125.0Methoxychlor 14.0 96.1Toxaphene 17.2 *--------------------------

Because of the difficulties encountered recovering Toxapheneat quantitative levels, a different silica modified surface wasemployed. Comparison of the recoveries of the target analytes in C8and C18 Empore disks are shown in Tables 7 and 8. In both cases theextracting solvent employed was methylene chloride\ethyl acetate(1:1).

Table 7. Recovery of pesticides from TCLP extraction fluid # 1using C8 and C18 Empore extraction disks.

Compound C8 C18

Chlordane 82.2 85.1Endrin 87.5 89.0Heptachlor 85.0 122.0Heptachlor epoxide 72.5 95.5Lindane 125.0 125.0Methoxychlor 142.0 148.0Toxaphene * *------------------------------

Table 8. Recovery of pesticides from TCLP extraction fluid # 2 atdifferent pH using C8 Empore extraction disks.

Compound C8 C18

Chlordane 98.7 85.1Endrin 52.8 67.5Heptachlor 60.0 73.0Heptachlor epoxide 51.8 45.0Lindane 125.0 125.0Methoxychlor 96.1 89.8Toxaphene * *------------------------------

Differences were observed in the recovery of target compoundsas a function of pH, extracting solvent and silica surface. Thesedifferences cannot be totally explained at this moment, however,they might be due to the fact that the matrix pH affect the silicaon the surface of the Empore disk, thus affecting retentionbehavior of the target analytes.

In summary, solid phase extraction proved to be an adequatetechnique for sample preparation in the analysis of TCLP pesticidesand herbicides. Further improvement is needed in order to optimizethe recovery, specially for Toxaphene. It provides a fast andconvenient way of sample preparation in an environmental laboratoryenvironment. The fact that less solvent, glassware, and thepossibility of automation will provide a cost effective solutionfor sample preparation.

REFERENCES

Infante, R., and Prez, C. (1991). Analysis of Semi-volatileAromatic Chlorinated Acids in Drinking Water by Liquid-SolidExtraction GC/MS. International Journal of EnvironmentalAnalytical Chemistry. 43, 165-176.

Infante, R., Gutierrez, C., and Prez, C. (1992). The Use ofLiquid-Solid Extraction Capillary Column GC/MS for theAnalysis of Chlorinated Acids and Phenols in Drinking Water.Water Science and Technology. Vol. 26, No 9-11, pp 2583-2586.

Junk, G.A. and Richard, J.J. (1988). Organics in Water: SolidPhase Extraction on a Small Scale. Analytical Chemistry. 58,451-454.