Relative standard deviation study

What is the estimated relative standard deviation for the results of a collaborative study in which the sample is pure analyte (100% w/w analyte) Repeat for the case in which the analyte s concentration is 0.1% w/w. 

Thus, we expect that approximately 67% of the participants in the collaborative study (+I0) will report the analyte s concentration within the range of 98% w/w to 102% w/w. When the analyte s concentration is 0.1% w/w (C = 0.001), the estimated percent relative standard deviation is... 

Of course, equation 14.26 only provides an estimate of the variability in results submitted by those participating in a collaborative study. A relative standard deviation that is within one-half to twice the estimated value suggests that the method performs acceptably when used by analysts in different laboratories. The percent relative standard deviation for a single analyst should be one-half to two-thirds that for the variability between analysts. 

A study was conducted to measure the concentration of D-fenfluramine HCl (desired product) and L-fenfluramine HCl (enantiomeric impurity) in the final pharmaceutical product, in the possible presence of its isomeric variants (57). Sensitivity, stabiUty, and specificity were enhanced by derivatizing the analyte with 3,5-dinitrophenylisocyanate using a Pirkle chiral recognition approach. Analysis of the caUbration curve data and quaUty assurance samples showed an overall assay precision of 1.78 and 2.52%, for D-fenfluramine HCl and L-fenfluramine, with an overall intra-assay precision of 4.75 and 3.67%, respectively. The minimum quantitation limit was 50 ng/mL, having a minimum signal-to-noise ratio of 10, with relative standard deviations of 2.39 and 3.62% for D-fenfluramine and L-fenfluramine. 

To determine of Ce(IV) in acid soluble single crystals, a simple and sensitive method is proposed. The method is based on the reaction of tropeoline 00 oxidation by cerium(IV) in sulfuric acid solution with subsequent measurement of the light absorption decrease of the solution. The influence of the reagent concentration on the analysis precision is studied. The procedure for Ce(IV) determination in ammonium dihydrophosphate doped by cerium is elaborated. The minimal determined concentration of cerium equal to 0.04 p.g/ml is lower than that of analogous methods by a factor of several dozens. The relative standard deviation does not exceed 0.1. 

The complex of the following destmctive and nondestmctive analytical methods was used for studying the composition of sponges inductively coupled plasma mass-spectrometry (ICP-MS), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and atomic absorption spectrometry (AAS). Techniques of sample preparation were developed for each method and their metrological characteristics were defined. Relative standard deviations for all the elements did not exceed 0.25 within detection limit. The accuracy of techniques elaborated was checked with the method of additions and control methods of analysis. 

A simple, rapid and seleetive eleetroehemieal method is proposed as a novel and powerful analytieal teehnique for the solid phase determination of less than 4% antimony in lead-antimony alloys without any separation and ehemieal pretreatment. The proposed method is based on the surfaee antimony oxidation of Pb/Sb alloy to Sb(III) at the thin oxide layer of PbSOyPbO that is formed by oxidation of Pb and using linear sweep voltammetrie (LSV) teehnique. Determination was earried out in eoneentrate H SO solution. The influenee of reagent eoneentration and variable parameters was studied. The method has deteetion limit of 0.056% and maximum relative standard deviation of 4.26%. This method was applied for the determination of Sb in lead/aeid battery grids satisfaetory. 

In the eourse of the study ICP AES teehnique for determining B, Ba, Ca, Cl, Cu, Ee, K, Mg, Mn, Na, P, S, Se, Si, Sr, and Zn in blood serum is developed. Relative standard deviations vary in the range from 0.02 to 0.25 depending on the element. The eorreetness of results obtained is eonfirmed by eomparing with those of independent analytieal methods. 

Determinarion of MW and MWD by SEC using commercial narrow molecular weight distribution polystyrene as calibration standards is an ASTM-D5296 standard method for polystyrene (11). However, no data on precision are included in the 1997 edition of the ASTM method. In the ASTM-D3536 method for gel-permeation chromatography from seven replicates, the M of a polystyrene is 263,000 30,000 (11.4%) for a single determination within the 95% confidence level (12). A relative standard deviation of 3.9% was reported for a cooperative determination of of polystyrene by SEC (7). In another cooperative study, a 11.3% relative standard deviation in M, of polystyrene by GPC was reported (13). 

An interlaboratory study using mixed vegetable reference material showed average relative standard deviations (RSDs) of 23% ranging from 11% for lutein and a-carotene to 40% for lycopene." Triplicate HPLC injections of the same extract showed RSD values of 0% for P-carotene and 6.8% for lutein. ... 

Fan et al. [106] developed a high performance capillary electrophoresis method for the analysis of primaquine and its trifluoroacetyl derivative. The method is based on the mode of capillary-zone electrophoresis in the Bio-Rad HPE-100 capillary electrophoresis system effects of some factors in the electrophoretic conditions on the separation of primaquine and trifluoroacetyl primaquine were studied. Methyl ephedrine was used as the internal standard and the detection was carried out at 210 nm. A linear relationship was obtained between the ratio of peak area of sample and internal standard and corresponding concentration of sample. The relative standard deviations of migration time and the ratio of peak area of within-day and between-day for replicate injections were <0.6% and 5.0%, respectively. 

Fang et al. [661] have described a flow injection system with online ion exchange preconcentration on dual columns for the determination of trace amounts of heavy metal at pg/1 and sub-pg/1 levels by flame atomic absorption spectrometry (Fig. 5.17). The degree of preconcentration ranges from a factor of 50 to 105 for different elements, at a sampling frequency of 60 samples per hour. The detection limits for copper, zinc, lead, and cadmium are 0.07, 0.03, 0.5, and 0.05 pg/1, respectively. Relative standard deviations are 1.2-3.2% at pg/1 levels. The behaviour of the various chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of seawater. 

Lee and Chau [66] have discussed the development and certification of a sediment reference material for total polychlorobiphenyls. Alford Stevens et al. [49] in an inter-laboratory study on the determination of polychlorobiphenyls in environmentally contaminated sediments showed the mean relative standard deviation of measured polychlorobiphenyl concentrations was 34%, despite efforts to eliminate procedural variations. Eganhouse and Gosset [67] have discussed the sources and magnitude of bias associated with the determination of polychlorobiphenyls in environmental sediments. Heilman [30] studied the adsorption and desorption of polychlorobiphenyl on sediments. 

This automated procedure was estimated to have a precision of 0.13-0.21mg Hg kg-1 at the lmg Hg kgr1 level with standard deviations varying from 0.011-0.02mg Hg kg-1, i.e. relative standard deviations of 8.4-12% at the 17.2-32.3mg Hg kg-1 level in sediments. Recoveries in methyl mercuric chloride spiking studies were between 85 and 125%. The detection limit for the automated method is dependent upon the weight of sample taken for analysis. It is 0.1 pg Hg L 1 in the aqueous samples. The results for the automated method are routinely reported to a lower limit of O.lmg kg 1 which corresponds to a dry sample weight of 0.25g. 

In another study, PLE with methanol was compared with Soxhlet with methanol [49], Recoveries and relative standard deviations were comparable for both the methods, confirming that Soxhlet can easily be substituted by PLE in already developed methods, without other substantial changes in the analytical procedure. 

Two studies compared sonication with Soxhlet extraction with pentane [13], acetone/hexane [13] and hexane/ispropyl alcohol (70 30) [5], The first two Soxhlet extraction solvents yielded lower recoveries than sonication, but the most polar solvent hexane/isopropyl alcohol gave recoveries and relative standard deviations for NP and NPE0i i9 comparable with sonication with hexane/acetone [5],... 

Raman often is evaluated as an alternative to an existing high performance liquid chromatography (HPLC) method because of its potential to be noninvasive, fast, simple to perform, and solvent-free. Raman was compared to HPLC for the determination of ticlopidine-hydrochloride (TCL) [43], risperidone [44] in film-coated tablets, and medroxyprogesterone acetate (MPA) in 150-mg/mL suspensions (DepoProvera, Pfizer) [45] it was found to have numerous advantages and performance suitable to replace HPLC. In an off-line laboratory study, the relative standard deviation of the measurement of the composition of powder mixtures of two sulfonamides, sulfathiazole and sulfanilamide, was reduced from 10-20% to less than 4% by employing a reusable, easily prepared rotating sample cell [46]. 

A relative standard deviation RSD) is also calculated for each set of results to show the overall variation measured throughout the study and as a reassurance that this level of variation is reflected in the observed main effects. 

Methods found for the determination of diazinon in animal products also used homogenization with a polar organic solvent as the first step in residue recovery. Toyoda et al. (1990) isolated diazinon from milk via partition into methylene chloride after extraction of the milk with 70% acetonitrile in water. Based on GC/FPD, an LOD of 10 ppb and a recovery of 89% (3.8% relative standard deviation) at 100 ppb were reported. Diazinon residues in eggs were studied (Leoni et al. 1992) after blending the eggs with acetone and partitioning into dichloromethane and acetone followed by C18-silica SPE. Based on GC/FPD analysis, an LOD of 1 ppb and a recovery of 93% at 13 ppb were reported. 

The reproducibility determined by such a study is often compared with a calculation for the relative standard deviation (RSD) using the Horwitz... 

In a seminal study in 1980, Horwitz and colleagues compiled interlaboratory reproducibility values for a large number of chemical analyses (around 7500, later expanded to more than 10,000) and observed that there was a trend to increased reproducibility (expressed as a relative standard deviation, RSD) with smaller concentration, expressed as a mass fraction (x) (i.e., 1 mg kg 1 = 1 ppm and x= 10 6). An empirical fit of the compiled data gave the Horwitz relationship... 

---