Analytical procedure relative standard deviation

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

Precision of an analytical procedure is commonly expressed by an average relative standard deviation (e.g., the precision of the determination of Mn in steel by XRF in a given routine control is 1.5% ). 

The following analytical procedure for the accurate estimation of hydroperoxides was proposed [61], The reduction of peroxide occurs in a solution of isopropanol saturated with Nal in the presence of acetic acid and C02 atmosphere at 373 K (in water bath). The reaction ceases after 15 min. The relative standard deviation equals 0.2%. 

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. 

Abstract A preconcentration method using Amberlite XAD-16 column for the enrichment of aluminum was proposed. The optimization process was carried out using fractional factorial design. The factors involved were pH, resin amount, reagent/metal mole ratio, elution volume and samphng flow rate. The absorbance was used as analytical response. Using the optimised experimental conditions, the proposed procedure allowed determination of aluminum with a detection limit (3o/s) of 6.1 ig L and a quantification limit (lOa/s) of 20.2 pg L, and a precision which was calculated as relative standard deviation (RSD) of 2.4% for aluminum concentration of 30 pg L . The preconcentration factor of 100 was obtained. These results demonstrated that this procedure could be applied for separation and preconcentration of aluminum in the presence of several matrix. 

Whereas precision (Section 6.5) measures the reproducibility of data from replicate analyses, the accuracy (Section 6.4) of a test estimates how accurate the data are, that is, how close the data would represent probable true values or how accurate the analytical procedure is to giving results that may be close to true values. Precision and accuracy are both measured on one or more samples selected at random for analysis from a given batch of samples. The precision of analysis is usually determined by running duplicate or replicate tests on one of the samples in a given batch of samples. It is expressed statistically as standard deviation, relative standard deviation (RSD), coefficient of variance (CV), standard error of the mean (M), and relative percent difference (RPD). 

Method Performance. A blank sample, prepared using the same procedure as for the samples, was included with every five samples. PCB 28 and y-HCH were the only compounds detected in the blanks. Detection limits, calculated as mean blank +3 SD, were typically 2.3-13.3 pg/pF = 0.02-0.12 ng/g soil. Results were not blank corrected. Replicate analysis (the same soil sample extracted three times) was done for several samples. The relative standard deviation (RSD) for replicate analysis was always less than 20% (n = 3). Analytical recoveries were monitored with the aid of two recovery standards mirex for FI and 5-HCH for F2. The mean recovery for mirex was 100 ... 

Determination of LAQL. Tests were performed with the recommended analytical procedures and sorbent materials to establish the LAQL for each analyte. As stated previously, the LAQL is the smallest amount of a compound that can be determined with a recovery from the sorbent greater than 80% and a relative standard deviation less than 10% (9). 

The method for 1,2-DCP was evaluated in the concentration range of 0.124 to 128 mg/m3 in 3-L air samples. The average bias from the independent analytical procedure (total hydrocarbon analyzer) was less than 1% over the range of the method. The pooled relative standard deviation was 6.4% over this range. 

The ICH recommends that repeatability be assessed using a minimum of nine determinations covering the specified range for the procedure (e.g., three concentrations/three replicates as in the accuracy experiment) or using a minimum of six determinations at 100% of the test concentration. Reporting of the standard deviation, relative standard deviation (coefficient of variation), and confidence interval is required. The assay values are independent analyses of samples that have been carried through the complete analytical procedure from sample preparation to final test result. Table 1 provides an example set of repeatability data. 

FIGURE 9 Hierarchy of, relationship between, and objectives and requirements for prevalidation [106], validation [62,63, 68], and standardization of analytical methods [62, 63, 67, 68,75,84] RSD = relative standard deviation, CV = coefficient of variation, SOP = standard operating procedure. 

Cahill et al. [241] have developed a simple and sensitive analytical procedure for determining the concentration of trifluoroacetic acid in plant, soil, and water samples. The analysis involves extraction of trifluoroacetic acid by sulfuric acid and methanol followed by derivatisation to the methyl ester of trifluoroacetic acid. This is accomplished within a single vial without complex extraction procedures. The highly volatile methyl ester is then analysed using headspace gas chromatography. The spike recovery trials from all media ranged from a low of 86.7% to a high of 121.4%. The relative standard deviations were typically below 10%. The minimum detectable limit for the method was 34 ng/g for dry plant material, 0.20 ng/g for soil and 6.5 ng/1 for water. 

Chromatographic system and system suitability. The liquid chromatograph system is equipped with a 288 nm detector and a 3.9 mm x 30 cm column that contains packing LI. The flow rate is about 1.5 mL/min. Chromatograph the standard preparation, and record the peak responses as directed under Procedure. The column efficiency determined from the analyte peak is not less than 1000 theoretical plates, the tailing factor for the analyte peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%. 

The resulting metal, in the salt state, is dissolved in nitric acid and diluted to a known volume with double distilled water. The solution is analyzed by Atomic Absorption for the metals of interest. Metals such as Cadmium, Berylium and Nickel have very low threshold limit values which are set by OSHA and are frequently present in the sample in very low quantities. Many Atomic Absorption units are equipped with a hollow graphite tube atomizer which increases the sensitivity dramatically making it easier for the analyst to obtain reliable results for species present in the sample in very low concentrations. The validity of the metal fume data depends on sampling train calibration and the precision and accuracy of the analytical procedure. NIOSH has reported a 2% relative standard deviation in the analytical method which has been collaboratively tested. 

Prior to performing a formal validation, the analytical chemist should have performed some prevalidation during method development. The expectation is that a well-developed HPLC method should subsequently be validated with no major surprises or failures. Prior to validation, specificity and some degree of robustness should be demonstrated. In addition, some form of system suitability criteria will have been established. System suitability evaluates the capability of an HPLC system to perform a specific procedure on a given day. It is a quality check to ensure that the system functions as expected and that the generated data will be reliable. Only if the system passes this test should the analyst proceed to perform the specific analysis. System suitability can be based on resolution of two specified components, relative standard deviation, tailing factor, limit of quantitation or detection, expected retention times, number of theoretical plates, or a reference check. 

Errors associated with iron quantification and abimdance measurements are common to both fecal monitoring and hemoglobin incorporation methods According to Janghorbani and Young (2 )> acceptable absorption estimates can be obtained if the precision of these measurements is kept below 5% The analytical procedures developed in this study are thus considered satisfactory since the relative standard deviation was 2 48% for total iron quantification and less than 2% for ion abimdance determinations ... 

The precision of an analytical method is the closeness of a series of individual measurements of an analyte when the analytical procedure is applied repeatedly to multiple aliquots of a single homogeneous volume of biological matrix [16], The precision is calculated as coefficient of variation (C.V.), i.e., relative standard deviation (RSD). The measured RSD can be subdivided into three categories repeatability (intra-day precision), intermediate precision (inter-day precision) and reproducibility (between laboratories precision) [16, 78, 79, 81],... 

In the analytical procedure, an accurately measured aliquot of the product is diluted Avith a diluent (normally the mobile phase) and the resulting sample solution is injected into the HPLC. Because the majority of injectable pharmaceuticals are clear solutions, typically a simple dilution step is all that is needed for sample preparation. However, if the parenteral product is an emulsion or a suspension, appropriate steps must be taken to dissolve the product to achieve a clear solution (ultrasonication, filtration, etc.). For the assay procedure, the sample concentration chosen should be such that the peak areas obtained from multiple injections from the same sample are reproducible with minimum variance (<2% relative standard deviation). Peak shape and retention time also play important roles in the precision of the assay. A tailing factor less than 1.5 and a capacity factor less than 10 for the active peak are generally required for a good analytical method. A reference standard solution having the same concentration and using the same diluent as the sample solution is prepared. 

Second, work in the sample matrix. Choose a sample matrix for automating the manual SPE method that is free of analyte. Thus, all the interferences and other problems associated with the matrix will be addressed immediately. Third, spike the clean sample matrix to a known concentration so that recoveries may be calculated. Samples should be spiked to a midlevel concentration range. Finally, run samples in triplicate. Triplicates will give the percent relative standard deviation and are some indication of the reproducibility of your automated procedure. Samples that show a low relative standard deviation typically prove that the method is a well-written automated procedure. High relative standard deviations suggest problems with the matrix and recovery of the sample. 

Spectrophotometric analysis of cyclohexylsulphamic acid (46) and its salts has been carried out. The procedure involves conversion of the cyclamate to N,N-dichloro-cyclohexylamine (123) using excess hypochlorite. 123 is determined by measuring its UV absorption at 314 nm. Two collaborative studies have been reported using this analytical technique for the determination of cyclamate in soft drinks, desserts and jams162,163. The first study reports the results of nine laboratories assaying 3 soft drinks with cyclamate levels of 0.36-0.37 g kg"1 and 3 jams with cyclamate levels of 1.23-1.50 g kg -1. Average recoveries of cyclamate were 99.7% in the soft drinks and 103.8% in the jams with reproducibility coefficients of variation of 6.7% and 4.4%, respectively. The second study involved determination of cyclamates at much lower concentration levels, namely 90-311 mg 1 1 and 202-526 mg kg-1. The results from 15 collaborators gave cyclamate recoveries of 97.5% in soft drinks with relative standard deviations from 4.7% to 6.5%. The recovery from desserts was 98.6% with relative standard deviations of 6.9% to 8.5%. 

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