Describe the origin of shot noise in a spectrophotometer. How does the relative uncertainty vary with concentration if shot noise is the major noise source?

One method for the quantitative determination of the concentration of constituents in a sample analyzed by gas chromatography is area normalization. Here, complete elution of all the sample constituents is necessary. The area of each peak is then measured and corrected for differences in detector response to the different eluates. This correction involves dividing the area by an empirically determined correction factor. The concentration of the analyte is found from the ratio of its corrected area to the total corrected area of all peaks. For a chromatogram containing three peaks, the relative areas were found to be 16.4, 45.2 and 30.2, in order of increasing retention time. Calculate the percentage of each compound if the relative detector responses were 0.60, 0.78 and 0.88, respectively.

When opening the cover of an analytical detector, which optical elements can help us to differentiate whether the instrument is a spectrofluorometer or a UV-Vis spectrophotometer. Justify your answer:

The response of the instrument must be lincar in the sample matrix. Systematic errors can occur due to sample or standard preparation. It consists of a series of standard analyte solutions separate from the unknown. A blank is used to correct the response from the instrument. Known quantities of a standard solution of the analyte are added to the unknown. It is the method of choice when the matrix of the sample may affect the signal. Matrix effects can cause the same analyte concentration in an unknown and standard to give different responses. It is used to measure the instrument response as a function of a known analyte concentration under a set of conditions.

1. From spinach, the chromatographic analysis will yield two major substances: (a) B-carotene (C40H56), which will separate from the spinach mixture to form a yellow band, and (b) chlorophyll A (CSSH72MGN4OS), which will separate from the mixture to form a green band. i. Describe the characteristics and draw structures of these molecules. ii. From the spectrophotometric analysis, what wavelength (Amax) would you expect ß-carotene (C40H56) to absorb? What wavelength would chlorophyll A (CssH72MgN4O5) absorb?

Quantitative Analysis by External Standard Method Calcium in a juice sample is determined by atomic absorption spectrophotometry. A stock solution of calcium is prepared by dissolving 1.834 g of CaCl, 2H20 in water and diluting to 1000.0 mL. A substock calcium solution was prepared by transferring 10.00 mL of the stock to a 100.00 mL volumetric flask and diluting to the mark. Three standard solutions of calcium were prepared by transferring 2.500 mL. 5.00 mL and 10.00 mL of substock to 50.00 mL volumetric flasks and diluting to the mark. The sample is prepared by transferring 1.000 mL of fruit juice from the original bottle to a 25.00 mL flask and diluting to the mark. Strontium chloride is added to all solutions before dilution to avoid phosphate interference. Instrumental response of the standards is measured against the blank, and the following readings are recorded: 9.10, 18.6 and 37.0. The sampie reading is 28.1. Using the multipoint method, find the concentration of calcium in…

Flame Atomic Absorption Spectroscopy (FAAS) method is selected due to its wide applicability for metal ion analysis in drinking water samples. Provide appropriate discussion to determine the concentration of selected heavy metals (Cu and Cr) in the unknown tap water sample.

1. State the difference between transmittance, absorbance, molar absorptivity, and fluorescence. Which one(s) is proportional to analyte concentration?

You have obtained a gas chromatogram of a two component mixture of compounds A and B. The height of peak A is 3.84 cm. and the width at half height is 1 cm. The height of peak B is 3.49 cm. and the width at half height is 1.36 cm. The percentage of a component in the mixture is proportional to peak area. Estimate peak areas by multiplying height by width at half height. What was the percentage of compound B in the mixture? (Enter your answer as a number without any percent symbol or the word percent.)

A standard solution was prepared containing 10.0 ppm of an analyte and 15.0 ppm of an internal standard. Analysis of the sample gave signals for the analyte and internal standard of 0.155 and 0.233 (arbitrary units), respectively. Sufficient internal standard was added to an unknown sample to make it 15.0 ppm in the internal standard. Analysis of the unknown sample yielded signals for the analyte and internal standard of 0.274 and 0.198, respectively. Calculate the concentration of analyte in the unknown sample.