You are quantitating benzene using isopropyl-benzene as aninternal standard. During the first run, you add 100.0 microlitersof 500. microgram/mL benzene and 100.0 microliters of 500.microgram/mL isopropylbenzene to a vial and dilute to 1.000mL toprepare a solution that has a final concentration of 50.0micrograms/mL of benzene and isopropylbenzene. The peak areameasured by GC-MS corresponds to 1225 and 1775, respectively.
Taking an unknown sample of a solution containing benzene with avolume of 100.0 microliters, you spike it with 100.0 microliters of500. microgram/microliter solution of isopropylbenzene and diluteto the 1.000 mL mark. You measure a peak area of 1550 for benzeneand 1800 for isopropyl benzene.
The information is organized in the table below with theappropriate dilution factors applied for what is in the samplevial.
| Standard | Spiked Sample |
|---|
| [Benzene], micrograms/mL | 50.0 | Unknown |
|---|
| Benzene peak area | 1225 | 1550 |
|---|
| [Isopropylbenzene], micrograms/mL | 50.0 | 50.0 |
|---|
| Isopropylbenzene peak area | 1775 | 1800 |
|---|
What is the concentration of Benzene in the unknown sample, inunits of micrograms/mL?
A series of volumetric flasks are being prepared for theanalysis of mercury in the drinking water supply using the methodof standard addition. To prepare the flasks, 10 mL of drinkingwater and a varying amount of standard are added to each flask, andthe flasks are brought to the 25.00mL mark on the volumetricflask.
The concentration of mercury standard used was 20.0microgram/mL.
Please use the data tabulated below to provide the concentrationof mercury in the drinking water, in units of micrograms/mL.
It is recommended to use Excel or similar software
| mL Mercury Standard Added | Signal |
|---|
| 0.00 | 19.65 |
| 1.00 | 30.35 |
| 2.00 | 40.28 |
| 3.00 | 49.78 |
| 4.00 | 60.44 |
| 5.00 | 70.06 |
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