A scientist wishes to measure the concentration of methyl benzoate in a plant stream by gas chromatography. He prepares a sample of butyl benzoate to use as an internal standard. The ic results of a preliminary run, which used a solution known to contain 1.37 mg/mL of methyl benzoate (peak A) and 1.51 mg/mL of butyl benzoate (peak B), are shown. The area of peak A is determined to be 301 and the area of peak B is determined to be 349 measured in arbitrary units by the computer. To measure the sample, 1.00 mL of a standard sample of butyl benzoate containing 2.41 mg/mL is mixed with 1.00 mL of the plant stream material. Analysis of the mixture gave a 10 Time (min) 15 peak area of 499 for peak A and 417 for peak B. What is the concentration of methyl benzoate in the plant stream? methyl benzoate concentration: mg/mL Detector Response

A scientist wishes to measure the concentration of methyl benzoate in a plant stream by gas chromatography. He prepares a sample of butyl benzoate to use as an internal standard. The ic results of a preliminary run, which used a solution known to contain 1.37 mg/mL of methyl benzoate (peak A) and 1.51 mg/mL of butyl benzoate (peak B), are shown. The area of peak A is determined to be 301 and the area of peak B is determined to be 349 measured in arbitrary units by the computer. To measure the sample, 1.00 mL of a standard sample of butyl benzoate containing 2.41 mg/mL is mixed with 1.00 mL of the plant stream material. Analysis of the mixture gave a 10 Time (min) 15 peak area of 499 for peak A and 417 for peak B. What is the concentration of methyl benzoate in the plant stream? methyl benzoate concentration: mg/mL Detector Response

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter31: Introduction To Analytical Separations

Section: Chapter Questions

Problem 31.19QAP

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A scientist wishes to measure the concentration of methyl benzoate in a plant stream by gas chromatography. He prepares a sample of butyl benzoate to use as an internal standard. The results of a preliminary run, which used a solution known to contain 1.37 mg/mL of methyl benzoate (peak A) and 1.51 mg/mL of butyl benzoate (peak B), are shown. The area of peak A is determined to be 3.40×102 and the area of peak B is determined to be 398 measured in arbitrary units by the computer. To measure the sample, 1.00 mL of a standard sample of butyl benzoate containing 2.49 mg/mL is mixed with 1.00 mL of the plant stream material. Analysis of the mixture gave a peak area of 437 for peak A and 415 for peak B. What is the concentration of methyl benzoate in the plant stream?
The standard addition method is used to analyze a sample of a river water for mercury. Solution A is made by pipetting 5.00 mL of undiluted sample in to a 10 mL volumetric flask and filling to the mark with DI water. Solution B is made by pipetting 5.00 mL of undiluted sample and 3.00 mL of 15.0 ppb of Hg standard into same 10.0 mL volumetric flask and filling to the mark with DI. Solution A and B are analyzed using atomic absorption spectroscopy and give a percent transmittance values of 56 % and 33 % respectively (not blank corrected). A blank has a transmittance of 96%. What is the corrected absorbance of both solution A and B? A. Solution A: 0.123 Solution B: 0.463 B. Solution A: 0.463 Solution B: 0.234 C. Solution A: 0.123 Solution B: 0.234 D. Solution A: 0.234 Solution B: 0.463
If an instrument gives a response of 1240 for a standard containing 8 ppm of a substance, how much if this substance is in a sample that gives a response of 1705? Are any assumptions needed?
25 ml of pickled brine was taken from an apple pickled with vinegar and diluted to 500 ml, 25 ml of this was taken and acidity was determined with 0.2 N (Factor: 1.05) NaOH. In the main trials, 6.3 ml - 6.5 ml - 6.9 ml, respectively, 0.1 ml base was used in the analysis without using the sample.For example, how many ppm is its acidity?
What is the minimum distribution constant that permits removal of 99% of a solute from 50.0 mL of water with two 25.0-mL extractions with toluene? five 10.0-mL extractions with toluene?
Suppose that you try separating an unknown mixture by normal-phase chromatography with the solvent mixture 50% hexane-50% methyl t-butyl ether (which is more polar than hexane). The peaks are too close together and are eluted rapidly. Should you use a higher or lower percentage of hexane in the next run?
in a chromatographic analysis of water from a drinking fountain gives area of 1.56*10^4, 5.12*10^4, 1.49*10^4 and 1.76*10^4 for CH3CL3, CHCL2BR, CHCLBR2 and CHBR3 respectively. determine the percentage concentration of each of the triichoromethane in the sample
5) Retention factors for three solutes separated on a C8 nonpolar stationary phase at pH = 3 are given. Eluant was a 70:30 vol/vol mixture of 50 mM citrate buffer and methanol. a)Draw the dominant chemical structure of each of the substances at pH = 3. b)The retention factor for acetophenone is 4.21, for salicylic acid is 2.97, and for nicotine is zero. Explain the different retention factors.
1. Are there any difference between using a 2% NaCl and using a water in the paper chromatography. If there are, what is the differences between the two? If they are the just the same, state the reasons.
A STOCK SOLUTION containing 0.1581 g/L K2CrO4 was prepared.In order to make the CALIBRATION STANDARD, 5 ml of the STOCK was transferredinto a 50ml volumetric flask and then diluted with an appropriate solvent.Calculate:(a) The ppm of K2CrO4 in the CALIBRATION STANDARD.(b) The molarity of K2CrO4 in the CALIBRATION STANDARD. (c) Calculate the molar absorptivity of K2CrO4 (at 371.0 nm). Assume that Beer's Law isobeyed over this concentration range.At 371.0 nm, this CALIBRATION STANDARD in a cell of path length 1.00 cm gave a %T of 59.752.
3. Assume that in extraction from water into toulene, analyte A has distribution ratio of 10. A 20 mL portion of an aqueous solution of A is extracted with toulene. Which of thw following procedures will result in most efficient removal of A from the aqueous phase into toulene? (Please show the solution of the correct answer) A. 1 extraction with 20 mL of touleneB. 1 extraction with 40 mL of touleneC. 2 extractions with 20 mL of toulene eachD. 4 extractions with 10 mL of toulene each
Explain why it is incorrect to collect data for temperatures above 100 C in terms of the solute to solvent ratio. Table 1: Temperature VS. solubility data for ammonium chloride. Test tube # g NH4Cl/10 mL H2O Crystallization temp. (ºC) 1 1.0 g/10 mL H2O 10 oC 2 1.8 g/10 mL H2O 20 oC 3 2.9 g/10 mL H2O 40 oC 4 3.8 g/10 mL H2O 65 oC 5 4.4 g/10 mL H2O 95 oC