FIT-SPE

Compared with conventional particle-packed SPE cartridges, FIT-SPE provides an increased surface area for the extraction medium and a reduced pressure drop during extraction and desorption. Also, the undesirable plugging effect from insoluble materials in real samples can be very much diminished. Utilization of FIT-SPE has been discussed in a few review articles concerning the on-line coupling of miniaturized SPE to microcolumn liquid-phase separation techniques.24,25... 

Filtration flask (1 or 2 L) with a rubber collar to fit SPE columns. Attach to house vacuum or water-driven aspirator column. 

Sample preconcentration was performed by means of an automated on-line SPE sample processor Prospekt-2 (Spark Holland, Emmen, The Netherlands). Oasis HLB cartridges (Waters, Barcelona, Spain) were used to preconcentrate cannabi-noids present in the water samples whereas isolation of the rest of the compounds was done in PLRPs cartridges (Spark Holland). Before extraction, influent samples were diluted with HPLC water (1 9, v/v) to reduce matrix interferences and to fit some analyte concentrations, e.g., cocaine (CO) and benzoylecgonine (BE), within the linear calibration range. A sample volume of 5 mL was spiked with the internal standard mixture (at 20 ng/L) in order to correct for potential losses during the analytical procedure, as well as for matrix effects. Elution of the analytes to the LC system was done with the chromatographic mobile phase. 

SPE disc technology through rigid disc and membrane disc formats provides a way around the above-listed limitations of packed-bed SPE columns. SPE discs closely resemble membrane filters they are flat, usually 1 mm or less in thickness, with diameters varying in size. Some disks are sold loose, and users must install them in a filter holder. Others are sold preloaded in disposable holders with Luer fittings (82). 

In Section 6.4, it was shown for replicate experiments at one factor level that the sum of squares of residuals, SST, can be partitioned into a sum of squares due to purely experimental uncertainty, SSpe, and a sum of squares due to lack of fit, SSfof. Each sum of squares divided by its associated degrees of freedom gives an estimated variance. Two of these variances, s, f and spe, were used to calculate a Fisher F-ratio from which the significance of the lack of fit could be estimated. 

He prepared the SPE by first wetting it with 2 mL of methanol and then with 2 mL of water. Next, the SPE was attached below a particulate filter in a line leading to a 1-L suction flask (Fig. 12.1a). The inlet of the SFE was fitted with a tube dipped into a 1-L flask of the runoff water containing our compound, XX, at 5 parts per trillion. (He was unable to detect this level of compound by direct injection into an HPLC system.)... 

Single particle energies (SPE s) are determined by fitting the experimental separation of the 7/2+. state from other excitation states. As corrections are made to a given two-body interaction SPE s are redetermined. 

When an SPE sorbent shows good performance with an analyte its fitness for other analytes, however close in structure, should be experimentally confirmed. A case in point is the forensic analysis of the adrenergic agonists Clenbuterol (70) and Compound A (71), both forbidden for use as animal feed additives. Four types of sorbents were tested—cyanopropyl resin, sulfonic acid SCX, mixed SCX + Qg and nonendcapped ( is only the latter type was found to quantitatively extract 71 although the performance of all four was satisfactory for 70. End analysis was by GC-MS-MS127. 

Ansys, Inc. has recently introduced a solid-phase extraction pipette tip, called the SPEC PLUS PT, which is shown in Figure 11.9. The disk is placed in a pipette tip with the filter at the bottom of the column instead of at the top. The disk is conditioned in the normal way and sample is drawn up through the pipette tip and sorbed to the disk. The disk may be washed and then eluted with solvent. The elution consists of a back elution with the solvent pushed through the disk. The disk will be useful for small samples. It is fitted with a 4-mm disk with various phases. The method is a flexible, simple, and an unique approach to small sample handling by SPE. 

There are a number of new technologies that have appeared in solid-phase extraction (SPE) and SPE-related products. Although several of these products are not solid-phase extraction by the simple definition in Chapter 1, they do, however, fit into the general category of extraction and sample preparation using solid phases. Because of their innovation and application to classical SPE, these methods are included in this chapter. They include ... 

The future of SPE is quite exciting and will continue to involve miniaturization of SPE methods and more on-line use of both liquid and gas chromatography. As instruments such as GC/MS and HPLC/MS become more sensitive, smaller sample sizes may be used and on-line methods will become routine. Sampling handling will be minimized with automated systems that fit directly on the gas chromatograph, so that analysis proceeds directly from the water sample or biological sample to the instrument. 

The structural model, So, was fit to each bootstrap data set. That is. So was fit to Di to Dsos, resulting in models 1 to 505 (Mi to M505). When each of these models for the bootstrap data sets (Di to D505) were estimated, the squared prediction error (SPE) for each concentration was estimated. 

The optimum use of SPE procedures requires investigation of different stationary phases, their masses, the volume of conditioning, sample load, wash, elution solvents, and the sample size. These variables are readily studied in column format. But it is costly or inconvenierit to use only a fraction of the 96 wells to perform all the studies. Hence, modular well plates have been developed that have small removable plastic SPE cartridges that fit tightly in the 96-hole base plate, and only a portion needs to be used to develop a method. 

S3. Rcfieetiye R Factory formed Good cotnpres- Excellent Excellent Factory formed Light weight Fittings and spe- -200 1100 Depends on number ... 

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