Horizon Technology, Inc. , 45 Northwestern Drive, Salem, NH, 03079, USA. Tel: (603) 893-3663 Fax: (603) 893-4994 E-Mail: support-service@horizontechinc.com

Short Notes 6

EPA Method 1664 by Automated Solid Phase Extraction - Precision, Recovery and Method Detection Limits Susie Petitti, Horizon Technology, Inc., Salem, NH, USA

Introduction Oil and grease analysis using EPA method 1664 presents new challenges for laboratories moving away from Freon™113 based Liquid - Liquid extractions. The “performance based” method 1664 utilizes n-Hexane rather than Freon as the extraction solvent. Either Liquid - Liquid n-Hexane extractions (LLE) or the less cumbersome Solid Phase Extraction (SPE) can be used. SPE eliminates problems associated with LLE using hexane. Hexane is prone to form emulsions during LLE and the hexane floats whereas Freon sinks. Automated SPE reduces solvents, eliminates emulsions, reduces exposure to solvents, improves recoveries and consistency of results, and increases productivity and reduces labor costs. This paper presents data demonstrating the capability of the Horizon Technology SPE-DEX® Automated Extractor Systems for performing the sample extraction. Also presented, is data from a comparison study with LLE-hexane for the initial demonstration of capability. Instrumentation • Horizon Technology SPE-DEX® 3000XL Automated

Extractor System • Horizon Technology SPE-DEX® 4750 Automated

Extractor System • Evaporation source • Oil and Grease SPE disks • Oil and Grease Standard (Hexadecane and Stearic acid in

Acetone) Method Summary I. Initial Precision and Recovery (IPR) 1) Eight replicate, 1-litre volumes of DI water acidified to pH < 2

with 1:1 HCl. 2) 5 ml of hexadecane and stearic acid standard (4 mg/ml of each,

total concentration of 40 ppm) added to each bottle. 3) Four samples extracted with Horizon Technology SPE-

DEX® 4750 Automated Extractor System. 4) Pipet hexane layer into pre-weighed pans and evaporate. 5) Weigh pans with residue after evaporation and calculate

concentration. 6) Four samples extracted by liquid-liquid extraction,

evaporated, and oil and grease concentration calculated. II. Method Detection Limit (MDL) 1) Seven replicate, 1-litre volumes of DI water acidified to pH < 2

with 1:1 HCl. 2) 5 ml of diluted (1:10) hexadecane and stearic acid standard

(total concentration of 4.0 ppm) added to each bottle. 3) Extracted with Horizon Technology SPE-DEX® 4750

Automated Extractor System. 4) Pipet hexane layer into pre-weighed pans and evaporate. 5) Weigh pans with residue after evaporation and calculate

concentration. III. Ongoing Precision and Recovery (OPR) 1) 1-litre volumes of DI water acidified to pH < 2 with 1:1 HCl. 2) 5 ml of hexadecane and stearic acid standard (4 mg/ml of each,

total concentration of 40 ppm) added to each bottle. 3) Extracted with Horizon Technology SPE-DEX® 3000XL

Automated Extractor System. 4) Pipet hexane layer into pre-weighed pans and evaporate. 5) Weigh pans with residue after evaporation and calculate

concentration. Results Each laboratory is responsible for operating a formal quality assurance program. For Method 1664, the minimum requirements include an initial demonstration of laboratory capability (IPR), MDL study, ongoing analyses of standards and blanks (OPR), and analysis of a matrix spike. Each time a modification is made to Method 1664, the laboratory is required to repeat the IPR test and, if the detection limit will be affected by the modification, the laboratory is also required to repeat the MDL study. Table 1 shows the SPE and LLE comparison data for the initial precision and recovery study. The data was obtained from an independent petroleum refinery (Lab A). The Horizon Technology SPE-DEX® 4750 Automated Extractor System was used for solid phase extraction. When comparing results for SPE and LLE in Table 1, the SPE data show greater precision and accuracy.

Horizon Technology, Inc. , 45 Northwestern Drive, Salem, NH, 03079, USA. Tel: (603) 893-3663 Fax: (603) 893-4994 E-Mail: support-service@horizontechinc.com

Short Notes 6

Table 1: Initial Precision and Recovery Data – Lab A

Sample LLE (mg/l)

% Recovery

SPE* (mg/l)

% Recovery

1 35.0 87.5 40.3 100.8 2 32.0 80.0 39.5 98.8 3 34.2 85.5 39.9 99.8 4 31.9 79.8 40.1 100.3

Average 83.2 99.9 Standard Deviation

3.91 0.85

*Extraction performed on Horizon Technology SPE-DEX® 4750 Automated Extractor System Table 2 shows the MDL data from the solid phase extraction of seven replicate samples. The expected recovery for each spiked water sample is 4.0 mL/l. The standard deviation for the replicate study is multiplied by the student t value of 3.143 to compute the MDL value of 0.79 mg/l. The MDL value obtained is less than the 1.4 mg/l specified in the EPA Method. Table 2: Method Detection Limit Using SPE – Lab A

Sample SPE* (mg/l)

1 3.9 2 4.3 3 3.7 4 3.9 5 4.2 6 4.0 7 4.4

Blank 0 Standard Deviation 0.250713

MDL 0.787992 *Extraction performed on Horizon Technology SPE-DEX® 4750 Automated Extractor System Table 3 shows the data for the ongoing precision and recovery study. The data was obtained from an independent commercial laboratory (Lab B) using the Horizon Technology SPE-DEX® 3000XL Automated Extractor System. The results demonstrate that automated SPE is capable of meeting EPA requirements for precision and accuracy.

Table 3: Ongoing Precision and Recovery Study – Lab B *.

Day Blank (mg/l)

Standard Recovery(Expected, 40 mg/l)

% Recovery

1 0.70 36.1 90.25 2 0.50 39.7 99.25 3 1.10 40.4 101.00 4 0.40 39.4 98.50 5 0.00 39.8 99.50 6 0.90 39.6 99.00 7 0.00 39.8 99.50 8 1.10 39.0 97.50 9 0.50 40.3 100.75 10 0.30 38.9 97.25 11 0.00 40.3 100.75 12 0.50 37.8 94.50 13 1.70 38.5 96.25 14 1.00 38.0 95.00 15 0.00 39.6 99.00 16 0.60 38.5 96.25 17 0.30 39.3 98.25 18 0.50 39.3 98.25 19 0.40 39.0 97.50 20 0.40 38.8 97.00 21 0.10 39.5 98.75 22 0.30 39.1 97.75 23 0.60 39.4 98.50 24 0.40 38.8 97.00 25 0.00 41.2 103.00 26 0.70 39.6 99.00 27 0.40 39.9 99.75 28 0.10 37.9 94.75

Average 0.40 39.20 Standard Deviation

0.48 0.98

* Extraction performed on Horizon Technology SPE-DEX® 3000XL Automated Extractor System Conclusions The Oil and Grease data generated by two independent laboratories, demonstrates the capability of Horizon Technology SPE-DEX® Automated Extractor Systems to meet EPA criteria for Method 1664. Better precision and accuracy was also observed when comparing SPE with LLE in the IPR study. Automated SPE reduces solvents, eliminates emulsions, reduces exposure to solvents, improves recoveries and consistency of results, and increases productivity and reduces labor costs.