Jenna Selfridge
Adam Gilbert
Environmental Chemistry
Class Project
Ion Chromatography
Methods and Materials
We first obtained the salts needed to make stock standards. See Table 1. We made an anion stock solution using the calculations below for actual mass to made 100ppm stock solution in a 500mL volumetric flask. We then created a cation stock solution (500mL) in the same way to reach 100ppm. Salts were massed out (actual mass) and put into 500mL volumetric flask.Nanopure water was then added to reach the total 500mL amount. We then diluted samples to make standards as seen in Table 2. We used a micropipette to obtain the designated amount of stock soulution, added Nanopure water to the volumetric flask to get a total of 25mL, capped the volumetric flask, inverted seven times to mix and then poured into labeled beaker. We used clean pipette tips for each dilution and rinsed volumetric flask seven times before making next concentration. We started with lowest concentration and subsequently increased to the higher concentrations. We then loaded samples from designated beaker into the IC tray using clean tubes, see Table 5. We also loaded de-ionized water, nanopure water, as well as ppm known concentrations for quality control. We used water for the mobile phase for the anions and 20 millimolar …
Table 1.
Anion / Salt / Molecular Mass(g) of salt / Mass for 1ppm / Needed mass (for 100ppm in 500mL) / Actual Mass / Actual ppmFluoride / NaF / 41.996 / 0.002211 / 0.2211 / .1126 / 101.88
Chloride / NaCl / 58.443 / 0.001649 / 0.1649 / .0857 / 103.98
Bromide / NaBr / 102.894 / 0.001289 / 0.1289 / .0674 / 104.68
Nitrate-N / NaNO3 / 84.9949 / 0.001371 / 0.1371 / .0688 / 100.38
Nitrite-N / NaNO2 / 68.9955 / 0.00150 / 0.1500 / .0761 / 101.49
Phosphate / KH2PO4 / 136.093 / 0.00143 / 0.1430 / .0750 / 104.68
Sulfate / K2SO4 / 174.2596 / 0.00181 / 0.1810 / .0909 / 100.22
Cation
Ammonium / NH4Cl / 53.4597 / 0.00296 / 0.2960 / .1487 / 100.17
Lithium / LiCl / 42.394 / 0.00331 / 0.3310 / .3062 / 100.27
Sodium / NaCl / 58.443 / 0.001692 / 0.1692 / .1322 / 104.01
Potassium / KH2PO4 / 136.093 / 0.00143 / 0.1740 / .1735 / 99.69
Magnesium / MgSO4*7H2O / 246.3686 / 0.005694 / 0.5694 / .5146 / 101.53
Calcium / CaCl2*2H2O / 146.984 / 0.003668 / 0.3668 / .1869 / 101.92
Table 2.Measurements of Stock Standard to make concentration standards for both anions and cations.
Standards (ppm) / microliters (per 25mL in Volumetric Flask)0 / 0
0.2 / 50
0.5 / 125
1.0 / 250
2.0 / 500
5.0 / 1250
10.0 / 2500
Table 3. Ion Chromatography Run.
Sample # / Sample Name1 / DI
2 / Anion Std 0 ppm
3 / Anion Std 0.2 ppm
4 / Anion Std 0.5 ppm
5 / Anion Std 1.0 ppm
6 / Anion Std 2.0 ppm
7 / Anion Std 5.0 ppm
8 / Anion Std 10.0 ppm
9 / DI
10 / Cation Std 0 ppm
11 / Cation Std 0.2 ppm
12 / Cation Std 0.5 ppm
13 / Cation Std 1.0 ppm
14 / Cation Std 2.0 ppm
15 / Cation Std 5.0 ppm
16 / Cation Std 10.0 ppm
17 / DI
18 / Site 1 15April10
19 / 1ppm Cation QC
20 / Site 2 15April10
21 / Site 3 15April10
22 / Site 4 15April10
23 / DI
24 / 5ppm Anion QC
25 / Site 1 29April10
26 / Site 2 29April10
27 / 1ppm Cation QC
28 / Site 3 29April10
29 / Site 4 29 April 10
30 / DI
31 / Shutdown
RESULTS
All of our R-squared values were all between 0.9212-0.0.999994.
Table 4: Anion concentrations from collection samples.
Amount / Amount / Amount / Amount / Amount / Amountmg/L / mg/L / mg/L / mg/L / mg/L / mg/L
Fluoride / Chloride / Nitrite / Sulfate / Nitrate / Phosphate
Site 1 15April10 / 0.0301 / 0.3712 / 0.2931 / 2.9270 / n.a. / n.a.
Site 2 15April10 / 0.0369 / 1.9202 / 0.4668 / 2.9626 / 0.1007 / 0.0405
Site 3 15April10 / 0.0403 / 2.8778 / 0.4350 / 2.7017 / 0.1412 / n.a.
Site 4 15April10 / 0.0435 / 4.0621 / 0.4801 / 2.9399 / 0.1891 / n.a.
Site 1 29April10 / 0.0289 / 0.3273 / 0.2843 / 2.8175 / n.a. / n.a.
Site 2 29April10 / 0.0386 / 1.9412 / 0.4421 / 2.6670 / 0.0540 / n.a.
Site 3 29April10 / 0.0408 / 2.4118 / 0.4393 / 2.7216 / 0.0943 / n.a.
Site 4 29 April 10 / 0.0420 / 2.9533 / 0.4335 / 2.8195 / 0.0998 / n.a.
Table 5: Cation concentrations from collected samples.
Amount / Amount / Amount / Amount / Amountmg/L / mg/L / mg/L / mg/L / mg/L
Sodium / Ammonium / Potassium / Magnesium / Calcium
Site 1 15April10 / 0.7202 / n.a. / 0.1804 / 0.2280 / 1.4262
Site 2 15April10 / 1.6069 / 0.1664 / 0.3091 / 0.3959 / 2.2635
Site 3 15April10 / 2.1289 / 0.2147 / 0.3300 / 0.4049 / 2.1295
Site 4 15April10 / 2.8850 / n.a. / 0.4722 / 0.4406 / 2.3692
Site 1 29April10 / 0.7676 / n.a. / 1.0175 / n.a. / 1.5409
Site 2 29April10 / 1.7524 / n.a. / 1.6201 / n.a. / 2.2521
Site 3 29April10 / 2.0220 / n.a. / 1.6049 / n.a. / 2.1302
Site 4 29 April 10 / 2.3350 / n.a. / 1.7521 / n.a. / 2.3038
Fluoride- concentrations increased about the same on both days from site to site. Small amounts of fluoride are naturally occurring, especially in ground water.
Chloride- Concentrations did dramatical increase (approx 8times higher at site 4 compared to site 1). This is probably mainly due to road salt as the sites crossed roads into developed neighborhoods. Because it is spring time, a lot of the roads are getting washed off with rain, and the road salt can increase the stream water’s salinity.
Nitrite- We have a sudden increase from site 1-2 in nitrites. As observed, there was anice pretty plush well maintained lawn next to site 2. Because of water-run off from the lawn, this is probably the main cause of the dramatic increase. From sites 3-4, the stream goes through a commercial district and we see another increase before it rained, meaning maybe the rain caused an increase in water being pushed through the bog and we see a decrease in nitrites.
Nitrates- We see a drastic increase in nitrates before it rained. The first site on both days had no nitrates, but going from sites 2,3, and 4, the increase is mainly due to the well maintained lawn.
Site one had a high reduction potential and therefore we would expect high potential to convert nitrates into nitrites. The next sites had substantially decreased reduction potential which could explain the dramatic increase in the concentration of nitrates.
Sulfate-Site 3 was just below the bog, where organic material is abundant and uptakes sulfates. This is why we see a drastic decrease in sulfates on april 15th (before it rained) from site 2-3, and then we see an increase at site 4. On april 29th, the rain probably flushed out a lot of the excess sulfates.
Phosphate- Site 2 on the first day was the only site observed to have any detectable phosphate levels. This is probably due to the maintained lawn run-off and then the stream going thru the bog, where phosphates were taken up as nutrients by organisms.
Sodium- We see a dramatic increase on both days, from site to site. Like chloride, road salt in the neighborhood road’s is likely the cause for this increase. We know that naturally there is sodium content in groundwater.
This also indicates there were more chloride salts than sodium salts, when we compare the two.
Ammonium- Sites 2 and 3 on the first day water was collected did we detect any ammonium. Our IC instrument has had problems with detecting ammonium ions in samples in the past. So, this could have altered our results. Note: Ammonium is considered by-product from Nitrogen fixation from bacteria, or from fertilizer from the lawn from site 2 to 3.
Potassium- We see increases gradually from site 1 to 4 on the first day. After it rained, there was a dramatic increase in detectable potassium from site to site. This could be due to water run off from people’s lawns. Plants in the bog tend not to uptake potassium and we do not see a big difference in water taken after it went through the bog. **Site 1: There are forms of sedimentary rock that contain potassium silicates—Rainpotassium at site 1?
Magnesium- There was no detectable magnesium found in day 2 samples. On day 1, we see an increase from sites 1 to 2, and then from 3-4. We hypothesize that this increase may be due to evaporation and the condensing of water nutrients on day 1 which was a sunny, hot day.
Calcium- Statistically, the detectable amount of calcium remained relatively constant from day to day, despite rainfall. We know calcium can get into waterways because of erosion from rocks, which we see from sites 1 to 2. After the water goes through the bog, organisms uptake calcium and we see a decline in the concentration of detectable calcium, and then a slight increase to site 4.
Conclusion:
Some obvious features along the stream’s path affect ion concentrations, i.e. road run off, lawn fertilizers, organisms in the bog, rainfall, and even sunlight. The most dramatic increases we saw were salinity from road run off as well as nutrients that are used to fertilize people’s lawns. Ion chromatography is a very useful technique to detect anion and cations in water samples. It condenses a large amount of data for you to then analyze and determine the causes for increases and decreases in the nutrients in this freshwater stream
Chemistry ProbeSite / Conductivity (us/cm) / Temperature (degrees Celsius) / Dissoloved Oxygen % / Dissolved Oxygen ppm / Total dissolved solids / pH
1 / 37.3 / 9.8 / 82.6 / 9.6 / 17.96 / 6.55
2 / 19.02 / 9.2 / 80.1 / 11.92 / 12.6 / 6.72
3 / 23.5 / 13.6 / 85.5 / 11.8 / 13.9 / 6.74
4 / 22.9 / 11.8 / 77.0 / 11.2 / 14.8 / 6.79
CFE Probe
Site / Conductivity / Temperature / Dissolved Oxygen % / Dissolved Oxygen ppm / Reduction Oxidation Potential (mV)
1 / 15 / 7.78 / 100.2 / 11.93 / 468
2 / 26 / 8.76 / 97.6 / 11.35 / 264.9
3 / 29 / 13.65 / 88.8 / 9.22 / 101.6
4 / 32 / 9.9 / 99.2 / 11.23 / 160.3