ICP_Operations_Guide_2016

Linearity and Detection Limits P 7 Defining ICP Performance Characteristics

erformance Characteristics

The following steps are intended as a practical guide for the determination of an ICP’s performance characteristics: 1. Read the operating manual and familiarize yourself with the software, key instrumental parameters and preferred settings before the instrument is installed. Most instruments are supplied with optimization and wavelength or mass calibration standards that will be used during set-up by the service technician and are intended for use on a regular basis by the operator. Discuss the optimization process with the manufacturer as well as the preferred settings for the key instrumental parameters. The remaining steps assume that the operator fully understands and is able to perform the optimization process that has been defined by the manufacturer as well as the spectral limitations of the instrument. 2. Select the lines to be studied for each element (‘lines’ is used in this document to mean either wavelength or mass). Line selection is based upon spectral interference issues, detection limit requirements and working range requirements. Select as many lines as possible within practicality for each element. The greater the number of lines, the greater the flexibility. 3. Prepare single element standards over the anticipated working range for each element. The range of standards depends upon the analytical requirements. The following ranges are suggestions only: t 3BEJBM WJFX *$1 0&4 BOE ˜H N- t "YJBM WJFX *$1 0&4 BOE ˜H N- t 2VBESVQPMF 3_ NBTT ĕMUFSFE *$1 .4 BOE OH N- This step is important because these data can be used to determine instrument detection limits (IDL), linear working ranges, BOE TQFDUSBM DIBSBDUFSJTUJDT TVDI BT CBDLHSPVOE FRVJWBMFOU DPODFOUSBUJPOT #&$ BOE TQFDUSBM JOUFSGFSFODFT 8JUI NPTU modern (if not all) instruments, the spectra obtained for each element at each concentration can be saved for review later. In addition, the software will calculate the IDL and BEC plus the linear regression of each line will establish the linear working range. All of this is typically done for the operator by the software that comes with the instrument. If at all possible, attempt to: t 6TF TJOHMF FMFNFOU TUBOEBSET UIBU IBWF UIF USBDF NFUBMT JNQVSJUJFT SFQPSUFE PO UIF DFSUJĕDBUF PG BOBMZTJT .PTU DIFNJDBM standards manufacturers provide this information with their single element standards. These data are important in identifying direct spectral overlap interferences and in not identifying an impurity as an interference of this type. t 4UPSF BMM TQFDUSB PO DPNQVUFS BOE DPMMFDU UIF TQFDUSB GPS BMM MJOFT PG JOUFSFTU PO FBDI BOE FWFSZ TPMVUJPO ćJT NFBOT UIBU JG you are interested in possibly using up to 6 lines for roughly 72 elements, then each solution spectrum totaling 72 x 6 = ~ 432 lines per solution and ~ 432 x 5 = 2160 spectra for each element need to be stored for future reference. Most ICP-MS applications would require far fewer data to be collected due to the reduced number of lines available and/or feasible. t 8BTI CMBOL BDJE TPMVUJPO UISPVHI UIF JOTUSVNFOU GPS TFWFSBM NJOVUFT ACFUXFFO FMFNFOUT BOE BMXBZT BOBMZ[F B CMBOL BU UIF beginning of each element concentration series. Look for the presence of the prior element analyzed to confirm that it has been completely washed out of the introduction system. 4. Having the data available on a desktop computer is convenient and allows the analyst to construct potential spectra by calling up the element and the anticipated concentration for each element in the analytical sample. Having several lines available makes the job of line selection easy as well as the estimation of the line’s sensitivity and linearity. Constructing these composite spectra from pure single element solutions eliminates confusion as to the identity of the line. The following example is intended to illustrate the process: Examples of Spectra FYI : All spectra were obtained using a concentric glass nebulizer with no problems around salting out or plugging.

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