Spiking experiments

Spiking experiments were performed by first chromatographing solutions of each of the impurities at a given concentration. 

Hageman, T. C., An analysis of clearance factor measurements performed by spiking experiments, Biopharmacology, July/Aug., 39, 1991. 

The iron sulphide in South African coals is a mixture of pyrite and marcasite (18). Although marcasite is known to transform into pyrite at elevated temperatures, separate spiking experiments were performed to see if pyrite or marcasite would show a preferential catalytic effect. The addition of pyrite and marcasite minerals (-200 mesh), to the coal showed equivalent total conversions, and yields of oil and asphaltene. 

Recovery of polychlorobiphenyls from soil samples obtained in spiking experiments was 100% while that of chlorinated insecticides ranged from 81.5% (Heptachlor) to 96.3% (Dieldrin). A limit of detection of 6.5ppb was obtained from aroclors 1254 and 1260. 

The coefficient of variation obtained for the determination of total phosphorus in sediment at the 1400ppm level was 2.5%. Some 98-100% recovery of inorganic phosphate was obtained in spiking experiments carried out on sediments. 

Odanake et al. [1] have reported the application of gas chromatography with multiple ion detection after hydride generation with sodium borohydride to the determination of mono and dimethyl arsenic compounds, trimethyl arsenic oxide and inorganic arsenic in soil and sediments. Recoveries in spiking experiments were 100-102% (mono and dimethyl arsenic compounds and inorganic arsenic) and 72% (trimethyl arsenic oxide). 

To digest sediment samples, 5g of sediment and EDTA solution are extracted with 5ml hexane and the resulting solution gas chromatographed. Concentrations found in a marine sediment ranged from 8.3mg kg-1, (tetramethyllead and methyltriethyllead) to 12mg kg (dimethyldiethyllead and tetraethyllead) and recoveries in spiking experiments were between 8f and 84%. 

Chau et al. [19] found that in spiking experiments on sediments both the diethyl and triethyl species were recovered at satisfactory levels (Table 13.5). 

Extraction Procedure. We modified the extraction procedure of Nelson et al (10). Brie acidified with 2 ml of 5% trichloracetic acid (TCA) was extracted 3 times with 20 ml of petroleum ether. The combined extracts were reduced to 5 ml in a rotating evaporator, returned to the separatory funnel, and combined with 60 ml each of acetonitrile and distilled water. The acetonitrile-water-insecticide mixture was extracted twice with 60 ml of petroleum ether and anhydrous Na2S04 was added to the combined 120 ml extract. The extract was evaporated just to dryness and the residue was dissolved in benzene for analysis by gas-liquid chromatography (GLC). Extraction efficiencies in spiked experiments were 73% (aldrin) and 83% (dieldrin). 

One of the most important trends to simplify these complications is the generation of simple, rapid, and reliable procedures for sample preparation. Method development and setup require the use of materials of known compositions, for example, certified reference materials. Therefore, spiking experiments have to be performed for method quality control. Under such experimental conditions, emphasis has to be placed on the spiking procedures as they exert an influence on the recovery values. Although present scientific knowledge is not perfect, the use of spiking experiments helps to minimize the errors. The integration and automation of all steps between sample preparation... 

Bowles and Apte [698] have described a method for the determination of methylmercuiy compounds in non saline waters using steam distillation followed by gas chromatography with an atomic fluorescence spectrometric detector. These workers evaluated steam distillation as a technique for the separation of methylmercury compounds from water and obtained recoveries in spiking experiments ranging from approximately 100% in fresh waters and estuaries to 80% in sea water. 

Virus identification can start during cell bank characterization and continues until the final product is obtained. It is essential to demonstrate that the viruses are not co-purified with the product (FDA, 1993a, 1997 ICH, 1997). The efficiency of removal or inactivation procedures should be demonstrated on a small scale through spiking experiments, by the use of the viruses themselves, when identified and possible, or with model viruses which mimic any possible variants large or small, DNA or RNA genome,... 

The decalins recovered in the product were present in the tetralin before reaction as minor impurities. The cis- and trans-isomers were fully resolved in our chromatograms and positively identified by spiking experiments with authentic samples. Material balance calculations indicate that the total amount of decalins was essentially unchanged over the course of the reaction. Hooper et al. (10) have also reported that the amount of decalin in tetralin did not change when it was heated to 450°C with coal. However, we do observe that the ratio of the trans- to cis-isomer is greatly changed and seems to approach an equilibrium value after reaction at the highest coal concentration. 

When RMs or proficiency studies are unavailable, the bias of the analytical method is mostly assessed using spiking experiments. As a rule, the bias is estimated by using blank material that is fortified with a known amount of the analyte. The samples are analyzed n times and the mean is calculated ... 

The representativeness of a spiking experiment to asses the method bias is an important issue in food analysis. It has been questioned whether one can evaluate the extraction of substances in a matrix by means of a spiking experiment. The extraction efficiency of incurred and spiked analytes is seldom the same. For some substances, it is hard to find real blank materials. Furthermore, several parameters have influence on the uncertainty of the experimentally determined method bias [32]. It should be stressed that, as it may be concentration-dependent, the method bias should be evaluated for the entire concentration range of the analytical method. 

A strong preference in speciation analysis is to use a separation step that can be combined with a detection step in an on-line system [45]. In such coupling, analytical selectivity relies on the application of different chromatographic or electrophoretic methods, while the use of atomic spectrometric techniques assures high sensitivity and f>t-for-purpose limits of detection (LoDs). However, hyphenated techniques with element-specif>c detection do not provide structural information on the species. If appropriate standards are available, the assignation of chromatographic peaks can be accomplished by spiking experiments. On the... 

Figure 11. For the purpose of this discussion, the most important features in the spectrum are the two methanol peaks labeled b and c, where b is the methyl proton resonance for methanol trapped within the hexameric sphere, and c is the methyl proton resonance for methanol in the bulk solvent. The identity of these peaks was proved by a spiking experiment in which additional methanol added to the NMR tube had the effect of increasing the intensity of peak c. Similar results were obtained in acetone-, DIVISOR and toluene- - It should also be noted that NMR spectra for hexamer 8 synthesized in ethanol or 2-propanol also showed two sets of resonances for each inequivalent proton in the ethanol or 2-propanol molecules. Indeed, in a pressurized NMR sample tube we observed no change in the intensities of peaks b and c at 150 °C in acetone- -...

GC—MS Analysis. The acidic components of four Carthaginian samples (1, 7, 10, and 12) were subjected to a complete analysis by GC. Sample preparation is described in a previous section (see Materials and Methods). Results are given in Table II. The identities of the acids were established by (i) the retention times obtained from reference samples, (ii) the comigration of acids with reference standards during spiking experiments, and (iii) the mass spectra of the constituents (18). 

A spiking experiment carried out is adequate at this stage (only possible if impurity/impurities are available). 

For time experiments, when the initial recovery experiment is completed (when using a real drug product, not from spiked experiments), the solution that is left over is set aside for time t (usually 24 hours at a temperature condition known not to affect the inherent stability of the solution). After time t, the solution is re-shaken by hand and then re-injected to determine assay value. 

The accuracy of the method can be determined by performing recovery experiments or by comparison to another analytical method (such as titration, DSC, and PSA). Spiking experiments, where increasing amounts of an impurity are introduced into the sample and the accuracy of the result versus... 

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