GC-MS应用EPA方法分析饮用水中的VOC

　　Overview

A Productivity Solution, encompassing the DSQ TM II mass Spectrometer, a FOCUSTM GC，EnviroLabTM Forms 2.0 software, an OI Eclipse 4660 Purge-and-Trap, and the OI 4551A Purge-and-Trap Autosampler, was developed for the analysis ot drinking water according to the criteria listed in United States Environmental Protection Agency (US EPA) Method 524.2.1During development of this comprehensive solution, experiments were set up to evaluate the ability of the instrument to handle the large amount of water associated with this method. Precision and accuracy oi the internal standards and surrogates addition were measured. Instrument parameters were set up to ensure minimal day-to-day maintenance, and consumables were selected based on their pert or mance for the method. A purge-and-trap adapter kit was installed on the FOCUS GC inlet to provide an inter iace for sample introduction. By integrating the hardware, so it ware, methods, and documentation into a turn-key package, the 524.2 Productivity Solution rapidly trans torms the DSQ TM II GC/ MS into a dedicated EPA Method 524.2 analyzer.

The sensitivity of the DSQ TM II mass spectrometer enables the operator to use a 5 mL instead of the traditional 25 mL sparge tube. A11 method detectionlimits (MDL’S)were met as outlined in the method. In addition the smaller sample size shows increased response for the more polar anal ytes due to the increase purge efficiency derived from the higher purge gas to liquid ratio. Enviro Lab Forms 2.0 software simplifies data review and reporting by using application-specific templates for creating instrument sequences for calibration, method detection limit determinations, and daily batch sequences of matrix spikes and matrix spike duplicates. A Standard Operating Procedure and How TO Manual with a Quick Start Guide are included to facilitate the installation of the application.2,3,4

Volatile organic compounds are extracted by bubbling inert gas through a 5 mL water sample, trapped in a tube of sorbent material, and then thermally desorbing into the GC inlet. The desorbed anal ytes are trans ierred to the split/ splitlees inlet on the GC through a heated transfer line. The split/ splitless inlet was operated in split mode, with a column flow of 1 mL/ min and split flow of 80 mL/ min. The column was programmed to elute all compounds in less than 11 minutes as shown in Figure 1. The mass spectrometer was set up for EI full scan from m' z 35 to 260. The instrument parameters are listed in Table 1.

The DSQ TM II system provided or exhibited excellent sensitivity and reproducibility with an average MDL of < 0.095 lig/ L. The system easily met the tuning criteria for 4-bromo fluor obenzene (BFB) by using Target Tuning. The calibration curve met all of the method QC criteria

for linear fit with an average percent relative standard deviation (RSD) of 6. The precision for the internal standard and surrogates was typically < 2% RSD.

　　Instruments

A Productivity Solution, encompassing the DSQ TM II mass Spectrometer, a FOCUSTM GC，EnviroLabTM Forms 2.0 software, an OI Eclipse 4660 Purge-and-Trap, and the OI 4551A Purge-and-Trap Autosampler, was developed for the analysis ot drinking water according to the criteria listed in United States Environmental Protection Agency (US EPA) Method 524.2.

　　Conclusion

The 524 Productivity Solution provides fast chromatography, with a short run time of 15 minutes, including a 5 minute bake out of the column loll owing elution of the last compound. Short run times enable a high-throughput lab to easily process 36 samples or more per 12 hour shift, which

is nearly three times the sample throughput compared to conventional metho do logies. The DSQ TM II system successfully and reliably met the QC criteria for EPA Method 524.2 using the FOCUS GC and split injections. Combined with a fast scanning rate and excellent sensitivity, the DSQ TM II GC/ MS allows users to easily achieve the MDL s required by the EPA method. The 524 Productivity Solution features Enviro Lab Forms 2.0 software, a package that matches the work flow in environmental laboratories is simple to use, and allows novice users to be instantly productive. Electronic methods and a Standard Operating Procedure, along with a How To Manual with Quick Start Guide, can be downloaded to the local PC by installing the Interactive Reference CD, and a Validation Data CD may be used as a reference of typical data for the method. Ultimately, the 524 Productivity Solution transforms the DSQ TM II system into a dedicated analyzer for volatiles in drinking water.