Determination reagents, analytical grade

The silicon traces present in the reagents and water used interfere in the determination of microgram amounts of silicon. Analytical grade HCl, H2SO4, and HF, and distilled water contain 2-10" %, 7-10 %, 4-10 %, and 2-10 % of Si, respectively [10]. These reagents may be considerably purified by distillation in quartz or platinum apparatus. Platinum, Teflon, and polyethylene vessels should be used and the silicon in a reagent-blank solution should be taken into account when traces of silicon are determined. The interfering effect of various substances on the determination of Si as silicomolybdenum blue was studied after decomposition of the samples with HF [32]. 

Benzene (analytical grade) was dried by molecular sieves of 4A size and distillated. N-Polyamine (Aldrich, 98%) was double distillated under vacuum. Purity of the reagents was checked chromatographically. It was 99.95 % for CH3(CH2)2NH2 and 99.98% for C6H6. The content of water was determined by Karl Fisher method It was not greater than 0.01%. 

The adsorbent used in the experiment was zeolite synthesised from fly ash. Dyes solution with a concentration of 1000 mg/L was prepared from analytical-grade reagent and DDW. Adsorption kinetics and isotherm experiments for all samples were undertaken using a batch equilibrium technique. The adsorption of dye was performed by shaking 0.1 g of adsorbent in 100 mL of dye solution with an initial concentration of 50-1000 mg/L at 150 rpm at different temperatures. The determination of dye concentration was done on a spectrophotometer by measuring absorbance at of 464, 630 and 560 nm for methyl orange, methylene blue and safranine T, respectively. In accordance with the Lambert-Beer law, the absorbance was found to vary linearly with concentration, and dilutions were undertaken when the absorbance exceeded 0.6. The data obtained from the adsorption tests were then used to calculate the adsorption capacity, qt (mol/g), of the adsorbent by a mass-balance relationship, which represents the amount of adsorbed dye per amount of dry adsorbent. All experimental runs were conducted at 28 2°C. 

The mixture of methylphosphonic dichloride, appropriate alcohol and 30 ml of benzene was refluxed during a period of 6 hours. After the reaction was completed, the mixture was shaken with alkalyzed water and water layer after acidification was reextracted with chloroform. No further purification was performed. Methylphosphonic dichloride was synthesized in Military Institute of Chemistry and Radiometry, Warsaw, Poland and its purity was 98% as determined by GC/MS method. All alcohols were analytical grade products of POCH, Gliwice, Poland, used without further purification. M-series standards (n-alkyl-bis(trifluoromethyl)phosphine sulfides) were obtained from HNU-Nordion (Helsinki, Finland). Derivatization reagents were ether solution of diazomethane obtained by... 

Determinations of pH, either by potentiometry or by spectrophotometry, thus require accurately prepared reference solutions of analytical grade reagents as standards. The standards should be well separated on the pH scale but, to minimize the effects of liquid-junction potentials, they should not be less than pH 3 nor greater than pH 11. 

Analytical reagent-grade reagents needed for determination are listed... 

PEG-200 was a commercial product (Chemische Werke Hiils, A. G.) with mean molecular weight 182 as determined osmometrically in the vapor phase (with an error of 5%) and with water content of 4.42% as determined by K. Fischer s method. (All weights were corrected with respect to this moisture.) CaCl2 was of analytical reagent grade. For the standard solutions, the stock saturated solution was prepared and maintained at the constant temperature of 25°C. The concentration of CaCl2 was tested by the chloride content argento-metrically. 

Thus, control charts measure both the precision and accuracy of the test method. A control chart is prepared by spiking a known amount of the analyte of interest into 4 to 6 portions of reagent grade water. The recoveries are measured and the average recovery and standard deviation are calculated. In routine analysis, one sample in a batch is spiked with a known concentration of a standard and the percent spike recovery is measured. An average of 10 to 20 such recoveries are calculated and the standard deviation about this mean value is determined. The spike recoveries are plotted against the frequency of analysis or the number of days. A typical control chart is shown below in Figure 1.2.2. 

Purge and trap concentration (or thermal desorption) from the aqueous matrices (aqueous samples or aqueous extracts of nonaqueous samples or methanol/ace-tone extract of nonaqueous samples spiked into reagent-grade water), separation of the analytes on a suitable GC column and their determination using a halogen-specific detector or a mass spectrometer. 

Note that f-statistics should be followed when the sample size is small, i.e., <30. In the MDL measurements, the number of replicate analyses are well below 30, generally 7. For example, if the number of replicate analyses are 7, then the degrees of freedom, i.e., the ( -1) is 6, and, therefore, the t value for 6 should be used in the above calculation. MDL must be determined at the 99% confidence level. When analyses are performed by GC or GC/MS methods, the concentrations of the analytes to be spiked into the seven aliquots of the reagent grade water for the MDL determination should be either at the levels of their IDL (instrument detection limit) or five times the background noise levels (the noise backgrounds) at or near their respective retention times. 

To determine the MDLs, laboratories prepare and analyze seven replicates of an analyte-free matrix (reagent water and laboratory-grade sand) spiked with the target analytes at concentrations that are 3-5 times greater than the estimated MDLs. Using seven results, the laboratories calculate the MDL according to the following equation ... 

To analyze the purity of the ASA he produced, the student measured out 0.400 g of pure, analytical reagent grade ASA and then treated it with NaOH to create sodium salicylate. He then added a FeCl3-KCl-HCl solution to create a purple salicylate complex. He then diluted this solution to 250. mL with distilled water. Determine the molarity of the stock solution. 

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