Performance of a Next Generation Vial Autosampler for the Analysis of VOCs in Water Matrices

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Application Note Performance of a Next Generation Vial Autosampler for the Analysis of VOCs in Water Matrices Abstract By: Ed Price In today s laboratories, increased efficiency and productivity are

1 Application Note Performance of a Next Generation Vial Autosampler for the Analysis of VOCs in Water Matrices Abstract By: Ed Price In today s laboratories, increased efficiency and productivity are of extreme importance. Equally important is the ability to automate analyses without sacrificing sample integrity or data quality. A new vial autosampler, the AQUATek 70, has been developed to fully automate purge and trap analysis of water and wastewater samples in accordance with current EPA methods for volatile analysis. Research will be presented demonstrating the instrument s ability to transfer sample aliquots with the addition of internal standard or surrogate solutions. Data will be evaluated for linearity, precision, and accuracy. In addition the instrument s sample pathway will be evaluated for carryover, inertness, and reliability. Introduction The AQUATek 70 is a liquid autosampler for purge and trap concentration that can handle water and wastewater samples of all types. The system is completely automated with automatic sample measurement, and standard addition in a closed system technique that minimizes the loss of volatiles during shipping, handling, and analysis. Virtually all sample preparation is eliminated, saving time and money. The AQUATek 70 uses a sampling system with years of proven reliability. Rather than bringing the vial to the sample needle, the sample needle is moved to the vial. This eliminates problems such as vial jamming and dropping, and allows particulate laden-samples to settle and remain undisturbed before sampling. This fact, combined with a unique sample pathway made of large bore tubing and large valve orifices eliminates clogging of sample lines and valves. All sampling is followed by a complete rinse of the systems pathway with Tekmar s proprietary high temperature OptiRinse system virtually eliminating carryover. Laboratories have productivity challenges that must be met in order to survive in their competitive markets. The AQUATek 70 meets these needs by accommodating up to seventy 40 ml VOA vials providing the highest sample capacity on the market today. The large sample capacity in combination with the system s reliability make the AQUATek 70 one of the premier vial autosamplers available today. Experimental The goal of this study is to evaluate the autosampler with respect to six key areas: internal standard precision, sampling precision, carryover, cleanliness, inertness, and particulate handling. Calibrations and method detection limit studies will be performed in accordance with EPA method to evaluate the systems cleanliness, and inertness. Carryover will be evaluated for the same compound list to evaluate the autosampler s cleanup procedure and high temperature OptiRinse. To determine the system s internal standard precision, samples with the addition of internal standard by the AQUATek 70 were analyzed for over a four-week period. This data will reveal not only the systems precision, but also the instruments reliability over time. The AQUATek 70 s sample pathway (figure 1) will be evaluated for carryover, and for the instrument s ability to handle particulate-laden samples. All analyses will be performed on an HP 5890 Series II GC equipped with an HP 5971 MSD. The column is a DB m x 0.53 mm ID x 3 um (J&W Scientific, Folsom, CA). The concentrator to be used in this study will be a Tekmar-Dohrmann 3000 Sample Concentrator with a Vocarb 3000 trap (Supelco, Bellefonte, PA). The parameters for the concentrator and the GC were taken from method A doc; 10-Jun-03 Sales/Support: Main: Socialville Foster Rd., Mason, OH

2 Figure 1 Internal Standard Precision The AQUATek 70 is equipped with the ability to automatically add an internal standard or matrix spike to any or all samples. This feature is controlled through the system software, and can be turned on or off depending on the method parameter that is chosen. Internal standard precision and reliability is of extreme importance in any fully automated system. To achieve more realistic data, the internal standard feature was used on every analysis over a four week period. The samples included groundwater and wastewater samples with varying sample concentrations. The data (figure 2) included over 800 analyses and the total %RSD calculated for the 800 runs was 4.5%. % RSD Jan 29-Jan 31-Jan 3-Feb 5-Feb 7-Feb 9-Feb 11-Feb 13-Feb 15-Feb 26-Feb 28-Feb Figure 2 A doc; 10-Jun-03 Page 2 of 5

3 Sampling Precision To ensure accurate and precise results an autosampler must be capable of sampling and transferring sample aliquots with precision and reliability. The precision of the AQUATek 70 s sample delivery was evaluated by two methods. The first test measured the actual volume of sample delivered by the autosampler to the concentrator (figure 3). These volumes were measured by a weight/specific gravity calculation. The results show that for 20 measurements an RSD of 0.32% was achieved. The second test measured the precision of the area counts obtained from BTEX analyses (figure 4). The RSDs for the BTEX compounds is representative of 20 runs. Volume delivered (ml) Run number Figure 3 Compound %RSD benzene 4.47 toluene 2.85 ethylbenzene 3.25 m, p-xylene 2.19 o-xylene 1.27 napthalene 2.76 Figure 4 Minimum Detection Limit A minimum detection limit study was performed to evaluate the AQUATek 70 s accuracy, precision, and cleanliness for low-level analyses. The MDL was established by running seven replicates at 0.1 ppb. The data in figure 5 represents MDLs for the EPA compounds. This data was calculated using a 99% confidence level. Compound MDL (ppb) Compound MDL (ppb) Compound MDL (ppb) dichlorodifluoromethane ,2-dichloropropane ,1,2,2-tetrachloroethane chloromethane dibromomethane ,2,3-trichloropropane vinyl chloride bromodichloromethane n-propyl benzene bromomethane cis-1,3-dichloropropene chlorotoluene 0.03 chloroethane toluene chlorotoluene trichlorofluoromethane trans-1,3-dichloropropene ,3,5-trimethylbenzene ,1-dichloroethene ,1,2-trichloroethane tert-butylbenzene methylene chloride tetrachloroethene ,2,4-trimethylbenzene trans-1,2-dichloroethene ,3-dichloropropane sec-butylbenzene ,1-dichloroethane dibromochloromethane ,3-dichlorobenzene ,2-dichloropropane ,2-dibromomethane isopropyltoluene cis-1,2-dichloroethene chlorobenzene ,4-dichlorobenzene bromochloromethane ,1,1,2-tetrachloroethane ,2-dichlorobenzene chloroform ethyl benzene n-butylbenzene ,1,1-trichloroethane m,p-xylene ,2-dibromo-3-chloropropa ,1-dichloropropene o-xylene ,2,4-trichlorobenzene carbon tetrachloride styrene hexachlorobutadiene benzene bromoform napthalene ,2-dichloroethane isopropyl benzene ,2,3-trichlorobenzene trichloroethene bromobenzene Figure 5 A doc; 10-Jun-03 Page 3 of 5

4 Calibration To evaluate the system s linearity, calibrations were performed for the compounds contained in EPA method Figure 6 displays the relative standard deviations obtained from five point calibrations. The calibration levels for the compounds were 0.5 ppb, 1.0 ppb, 5.0 ppb, 10 ppb, and 20 ppb. Compound %RSD Compound %RSD Compound %RSD dichlorodifluoromethane ,2-dichloropropane ,1,2,2-tetrachloroethane 4.24 chloromethane dibromomethane ,2,3-trichloropropane 5.28 vinyl chloride 2.39 bromodichloromethane 3.42 n-propyl benzene 4.71 bromomethane 5.08 cis-1,3-dichloropropene chlorotoluene 4.44 chloroethane 4.85 toluene chlorotoluene 6.38 trichlorofluoromethane 1.93 trans-1,3-dichloropropene ,3,5-trimethylbenzene ,1-dichloroethene ,1,2-trichloroethane 6.58 tert-butylbenzene 4.31 methylene chloride tetrachloroethene ,2,4-trimethylbenzene 3.49 trans-1,2-dichloroethene ,3-dichloropropane 3.77 sec-butylbenzene ,1-dichloroethane 3.18 dibromochloromethane 3.7 1,3-dichlorobenzene ,2-dichloropropane ,2-dibromomethane isopropyltoluene 4.72 cis-1,2-dichloroethene 3.69 chlorobenzene ,4-dichlorobenzene 5.59 bromochloromethane ,1,1,2-tetrachloroethane ,2-dichlorobenzene 5.2 chloroform 3.59 ethyl benzene 4.23 n-butylbenzene ,1,1-trichloroethane 4.54 m,p-xylene ,2-dibromo-3-chloropropane ,1-dichloropropene 4.18 o-xylene ,2,4-trichlorobenzene 3.07 carbon tetrachloride 4.58 styrene 4.29 hexachlorobutadiene 4.53 benzene 3.11 bromoform 6.11 napthalene ,2-dichloroethane 4.24 isopropyl benzene ,2,3-trichlorobenzene 5.1 trichloroethene 3.65 bromobenzene 4.61 Figure 6 Carryover To evaluate the system s carryover, 100 ppb standards were analyzed and followed by blank deionized water runs. Carryover was calculated based on raw area counts. Figure 7 represents the percent carryover for each compound in the EPA list. Compound %C.O. Compound %C.O. Compound %C.O. dichlorodifluorom ethane ND 1,2-dichloropropane ND 1,1,2,2-tetrachloroethane ND chlorom ethane ND dibrom om ethane ND 1,2,3-trichloropropane ND vinyl chloride ND bromodichloromethane ND n-propyl benzene 0.08 bromomethane ND cis-1,3-dichloropropene ND 2-chlorotoluene 0.05 chloroethane 0.01 toluene chlorotoluene 0.05 trichlorofluoromethane 0.01 trans-1,3-dichloropropene ND 1,3,5-trimethylbenzene ,1-dichloroethene ,1,2-trichloroethane ND tert-butylbenzene 0.05 methylene chloride ND tetrachloroethene ND 1,2,4-trimethylbenzene 0.08 trans-1,2-dichloroethene ,3-dichloropropane ND sec-butylbenzene ,1-dichloroethane ND dibromochloromethane ND 1,3-dichlorobenzene ,2-dichloropropane ND 1,2-dibromomethane ND 4-isopropyltoluene ND cis-1,2-dichloroethene ND chlorobenzene ND 1,4-dichlorobenzene 0.09 bromochloromethane ND 1,1,1,2-tetrachloroethane 0.1 1,2-dichlorobenzene ND chloroform ND ethyl benzene 0.01 n-butylbenzene ND 1,1,1-trichloroethane ND m,p-xylene ,2-dibromo-3-chloropropane ND 1,1-dichloropropene ND o-xylene ,2,4-trichlorobenzene ND carbon tetrachloride ND styrene ND hexachlorobutadiene 0.42 benzene ND bromoform ND napthalene 0.1 1,2-dichloroethane ND isopropyl benzene ND 1,2,3-trichlorobenzene ND trichloroethene ND bromobenzene 0.05 Figure 7 A doc; 10-Jun-03 Page 4 of 5

5 Particulate Handling The AQUATek 70 s flowpath and sampling mechanism have been optimized for particulate-laden samples. The instrument has been designed for water samples that contain up to 15 mm of sediment in a typical 40 ml vial. The entire sample pathway has been plumbed with large bore 1/8 OD Teflon tubing. This in combination with large valve orifices and large internal valve volumes allow for particulate to pass through the interface without danger of clogging. Large particulates are kept from entering the autosampler interface by the sampling needle. The needle contains numerous small diameter holes that act as a filter for larger particles. Due to the autosampler s design, vials are kept stationary from start to finish. This feature allows for particulates to settle within the vial before sampling, greatly reducing particulate interferences. Discussion Laboratories have productivity challenges that must be met to survive in their competitive markets. With a 70-vial capacity, the AQUATek 70 provides the highest sample capacity on the market. Analytically, the AQUATek 70 meets or exceeds the cleanliness, reproducibility, and durability specifications needed in a vial autosampler. Carryover is virtually non-existent with the combination of high temperature OptiRinse, and a Teflon tubing pathway. Almost the entire EPA volatile organic compound list exhibited zero carryover, with the exception of some high molecular weight compounds. The maximum carryover for any compound was hexachlorobutadiene at 0.42%. Linearity between the levels of 0.5 ppb- 20 ppb was excellent. Five point calibrations using fluorobenzene as an internal standard were performed on a 5971 MSD. All calibrations were < 7% RSD with the exception of methylene chloride and chloromethane. These exceptions can be attributed to lab air contamination. Reproducibility of the internal standard addition and sample delivery was excellent. The RSD averaged between 4-6% for the internal standard. These averages were higher than usual due to MSD drift over the course of 800 runs. The internal standard usage was minimal, approximately 11µl of standard per sample. This allows for over 1800 analyses to be performed out of one 20 ml internal standard vessel. The system s ability to handle particulate-laden samples is a tribute to the autosampler s ruggedness. The AQUATek 70 s mechanical reliability and unique sample pathway virtually eliminate any concerns about carryover, inertness, and the presence of particulates. Acknowledgements Lastly, the author would like to thank Rick Bauer and Sandy Cook from ATEL Inc., and Denise Califato from CT&E ESI for their contributions and help in the evaluation of the instrument. A doc; 10-Jun-03 Page 5 of 5

Validation of USEPA Method Using a Stratum PTC, AQUATek 100 Autosampler, and Perkin-Elmer Clarus 600 GC/MS

Validation of USEPA Method Using a Stratum PTC, AQUATek 100 Autosampler, and Perkin-Elmer Clarus 600 GC/MS Validation of USEPA Method 524.2 Using a Stratum PTC, AQUATek 100 Autosampler, and Perkin-Elmer Clarus 600 GC/MS Application Note By: Nathan Valentine Abstract The US EPA developed Method 524.2¹, Measurement