To identify the amount of caffeine in my coffee using an HPLC instrument, standard solutions of caffeine were prepared and analyzed using a 10-mL fixed-volume injection loop. Results for the standards: concentration (ppm) signal (arb. units) 8, 500 16, 900 25, 220 60.0 120.0 180.0 240.0 33, 585 300.0 42, 008 The sample was prepared by placing 10 g of coffee in a small beaker and adding 100 mL of methanol. After allowing the extraction of caffeine and filtration, the extract was quantitatively transferred to a 250-mL volumetric flask and diluted to volume with methanol. A 1.00mL aliquot was transferred to a 10-mL volumetric flask and diluted to volume with methanol. When analyzed by HPLC, the signal for caffeine was found to be 21,500. Create a linear calibration curve; determine the concentration of caffeine in the 10 mL solution in the volumetric flask that was introduced to the injector; and calculate the milligrams of caffeine in the 100 grams of coffee.

To identify the amount of caffeine in my coffee using an HPLC instrument, standard solutions of caffeine were prepared and analyzed using a 10-mL fixed-volume injection loop. Results for the standards: concentration (ppm) signal (arb. units) 8, 500 16, 900 25, 220 60.0 120.0 180.0 240.0 33, 585 300.0 42, 008 The sample was prepared by placing 10 g of coffee in a small beaker and adding 100 mL of methanol. After allowing the extraction of caffeine and filtration, the extract was quantitatively transferred to a 250-mL volumetric flask and diluted to volume with methanol. A 1.00mL aliquot was transferred to a 10-mL volumetric flask and diluted to volume with methanol. When analyzed by HPLC, the signal for caffeine was found to be 21,500. Create a linear calibration curve; determine the concentration of caffeine in the 10 mL solution in the volumetric flask that was introduced to the injector; and calculate the milligrams of caffeine in the 100 grams of coffee.

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter4: Least-squares And Calibration Methods

Section: Chapter Questions

Problem 10P

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2. To determine the concentration of analyte in a sample a standard additions was performed. A 5.00-mL portion of sample was analyzed and then successive 0.10-mL spikes of 1 600.0- mg/L standard of the analyte were added, analyzing after each spike. The following table shows the results of this analysis. Vspike, mL Signal intensity 0.00 0.119 0.10 0.231 0.20 0.339 0.30 0.442 Construct the calibration curve, calculate the linear least-squares equation for the data and determine the concentration of analyte in the original sample.
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?
The amount of caffeine in an analgesic tablet was determined by HPLC using a normal calibration curve. Standard solutions of caffeine were prepared and analyzed using a 10-µL fixed-volume injection loop. Results for the standards are summarized in the following table. Concentration of Standards Signal (arbitrary units) (ppm) 50.0 8354 100.0 16925 150.0 25218 200.0 33584 250.0 42002 The sample was prepared by placing a single analgesic tablet in a small beaker and adding 10 mL of methanol. After allowing the sample to dissolve, the contents of the beaker, including the insoluble binder, were quantitatively transferred to a 25-mL volumetric flask and diluted to volume with methanol. The sample was then filtered, and a 1.00-mL aliquot was transferred to a 10-mL volumetric flask and diluted to volume with methanol. When analyzed by HPLC, the signal for the caffeine was found to be 21469. Report the number of milligrams of caffeine in the analgesic tablet.
Internal standard (As , Cs ), analyte with known concentration (Ax , Cx ) In a chromatographic equipment, a solution containing 0.006727 X and 0.008331 M S give peak area of Ax= 2316 and As= 207. To analyze an unknown sample, 5.0mL of 0.008331M S was added to 5.0mL of X, and the mixture was diluted to 50.0mL. This mixture gave a chromatography spectrum with area Ax= 3206 and As= 200. Find Cx.
3. This is the standard procedure for determination of nicotine in urine. A 1.00mL sample was placed in a 12mL vial 5-aminoquinoline was added as the internal standard (5 ug). The sample was monitored using mass spectrometry at m/z values for nicotine (84) and the internal standard (144). Given the following data determine the concentration of the two unknown samples Nicotine (ug/L) Area Area 12 0.056 0.059 51 0.402 0.391 102 0.684 0.669 157 1.011 205 Unknown 1 Unknown 2 1.278 0.51 1.18 1.063 1.355 0.53 1.32
50 Percentage Red No. 40 Soln 100% 80% 60% 40% Table 4.1: Dilutions of Red No. 40 & Absorbance Volume of Red No. 40 Soln (mL) 10me 8mL опи 4mL Percentage Red No. 40 Soln 100% 80% 60% 40% 20% Volume of DI Water (mL) OML 2mL LIML M UML 8ML Table 4.2: Dilutions of Red No. 40 & Absorbance Concentration Red No. 40 2. Report the wavelength with the maximum absorbance of Red No. 40 dye. Absorbance 20% 2ML Part A: Making a Calibration Curve for Beer's Law 1. Calculate the concentrations of each of your diluted Red No. 40 solutions and add these to Table 4.2. Show at least one sample calculation in the space below. 0.251 0.192 Total Volume 0.181 0·119 0.060 (mL) 10 mL 10 mL 10 mL 10 mL 10 mL
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i) To estimate the accuracy and precision of the method of determination of glucose in a blood sample, blood was spiked with a 88.2 ngml1 of glucose. The amount of glucose was determined in the spiked sample giving the following results in ngml1, 83.6, 69.0, 83.4 100.0 and 76.4. a)Find the accuracy of the quality control sample. b)Find the precision of the quality control sample
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Analysis of an unknown plant extract yield two peaks X and Y in a chromatogram, 15.65 and 17.03 min respectively in a 30.0 cm column. The peak base width for X is 1.06 and 1.15 for Y. The average number of plates in the column is
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The original solution was diluted by a factor of three, and then the absorbance of the diluted cereal sample solution was measured and recorded as (2.0x10^-1). Use the following trendline and dilution factor to determine the concentration of iron, in unit of M, in the original cereal sample solution. The trendline (linear regression) as displayed on the plot is y = 11898x - 0.0112.