ANALYTES: Na+, K+, Ca2+, Mg2+
INSTRUMENT: Thermo Jarrell Ash
Smith-Hieftje 22 SpectrophotometerSAMPLES: Precipitation and streamwater
STANDARDS:
Standards are made from purchased 1000 mg/L sodium, potassium, calcium, and magnesium Atomic Absorption Standards.
PRECIPITATION:
Working Stock:
Dilute the following to 1000 mL with deionized water in a volumetric flask:
Final Conc. Na+: 5 mL of 1000 mg/L sodium standard 5 mg/L K+: 10 mL of 1000 mg/L potassium standard 10 mg/L Ca2+: 20 mL of 1000 mg/L calcium standard 20 mg/L Mg2+: 5 mL of 1000 mg/L magnesium standard 5 mg/LStore refrigerated in an amber high-density polyethylene bottle. Replace every 3 months. (Note: Do not add chloroform.)
Standards:
Prepare standards from the working stock as follows:
Std volume of total Concentration (mg/L)
# working stock volume Na+ K+ Ca2+ Mg2+
1 25 mL 250 mL 0.5 1.0 2.0 0.5
2 20 mL 250 mL 0.4 0.8 1.6 0.4
3 15 mL 250 mL 0.3 0.6 1.2 0.3
4 10 mL 250 mL 0.2 0.4 0.8 0.2
5 5 mL 250 mL 0.1 0.2 0.4 0.1
6 0 mL 250 mL 0.0 0.0 0.0 0.0
Store refrigerated in polyethylene bottles until use. Make fresh for each session. (Note: Do not add chloroform.)
Working Stock:
Dilute the following to 1000 mL with deionized water in a
volumetric flask:
Final Conc. Na+: 20 mL of 1000 mg/L sodium standard 20 mg/L K+: 30 mL of 1000 mg/L potassium standard 30 mg/L Ca2+: 50 mL of 1000 mg/L calcium standard 50 mg/L Mg2+: 20 mL of 1000 mg/L magnesium standard 20 mg/LStore refrigerated in an amber high-density polyethylene bottle. Replace every 3 months. (Note: Do not add chloroform.)
Standards:
Prepare standards from the working stock as follows:
Std volume of total Concentration (mg/L)
# working stock volume Na+ K+ Ca2+ Mg2+
1 50 mL 500 mL 2.0 3.0 5.0 2.0
2 40 mL 500 mL 1.6 2.4 4.0 1.6
3 30 mL 500 mL 1.2 1.8 3.0 1.2
4 20 mL 500 mL 0.8 1.2 2.0 0.8
5 10 mL 500 mL 0.4 0.6 1.0 0.4
6 0 mL 500 mL 0.0 0.0 0.0 0.0
Store refrigerated in polyethylene bottles until use. Make fresh
for each session. (Note: Do not add chloroform.)
REAGENTS:
Lithium/Lanthanum Spiking Solution:
111 g lithium carbonate (Li2CO3)
123 g lanthanum oxide (La2O3)
500 mL concentrated hydrochloric acid (HCl)
CAUTION: This reaction is violent. Work under fume hood,
and proceed slowly and cautiously.
Preparation:
Place the hydrochloric acid in a large Erlenmeyer flask
fitted with a stirring bar on a stirring plate. Add the
lithium carbonate in small increments. Then add the
lanthanum oxide in small increments. Dissolve and dilute to
1 liter with deionized water. (This does not have to be
volumetric). Filter through #4 Whatman paper.
NOTE THAT SAMPLES CANNOT BE RUN UNTIL ONE MONTH AFTER THEY HAVE BEEN CHLOROFORMED.
1) To clean pipetter tips, fill a large beaker with pipetter tips, add deionized water to cover, sonicate the beaker for 1-3 minutes, and then rinse by filling and emptying the beaker with deionized water 10 times.
2) Using a pipetter, pipet 10 mL of each sample or standard into a clean, dry, plastic tube.
3) Using the designated Repipet dilutor, add 0.5 mL of Li/La spiking solution to each tube. Cap and shake vigorously to mix thoroughly.
(Note: To prevent chloride contamination, do not use Li/La
spiking solution in room where anion IC is located.)
NOTES:
2) Use the same pipetter and the same batch of Li/La spiking
solution for all samples and standards.
SESSION FORMAT:
1) Samples are run in blocks of 50: 6 standards and 44 samples.
2) The session always begins and ends with a standard curve.
3) A mid-range standard (standard #3) is run midway between each set of standards.
4) Quality control samples used for cation sessions are listed in the following table:
PRECIPITATION:
QC Sample Dilution Analytes
FN10 01/01/90 - K+, Ca2+, Mg2+
FN10 01/01/90 2 Na+
1185 09/16/92 - K+
1185 09/16/92 2 Ca2+, Mg2+
E384 09/16/92 - K+
E384 09/16/92 2 Ca2+, Mg2+
STREAMWATER:
QC Sample Dilution Analytes
FN09 01/01/90 - K+, Ca2+, Mg2+
FN09 01/01/90 2 Na+
FN10 01/01/90 - Na+, K+, Ca2+, Mg2+
1185 09/16/92 - K+, Ca2+, Mg2+
1185 09/16/92 2 Na+
E384 09/16/92 - K+, Ca2+, Mg2+
E384 09/16/92 2 Na+
Bulk natural
matrix QC's - Na+, K+, Ca2+, Mg2+
QUALITY ASSURANCE:
The values obtained for each mid-range standard should be +5% of the true value. The values obtained for each QC should be +5% of the mean value or within 2 standard deviations of the mean value (z-score range: -2.000 to 2.000). The QC Report gives statistical information for QC's along with target values if available. The QC Report should be examined to determine if the QC's for that particular session pass quality assurance criteria. If not, that session should be rerun.
PROCEDURE:
1) Press POWER button to turn instrument on.
2) Turn to OPERATE.
3) Set elements to be measured using MODE #1: ELEMENTS. (Make sure background correction is not applied at this point: MODE #3: CHANNEL/BACKGROUND. A=A; B=B.)
4) Each element has an individual hollow cathode lamp. Handle the lamps carefully. Hold by the base of the lamp and wipe end with a piece of lens paper. Install lamp in the correct channel position and push forward until the base hits the holder.
Channel A: sodium or calcium
Channel B: potassium or magnesium
5) For each element to be measured, plug in the appropriate hollow
cathode lamp (only plug in one lamp at a time at this point) and
follow these steps:
a) Set the wavelength, bandwidth, and current (smaller knob)
according to the following parameters:
(Use the A/B switch to determine which channel's parameters
are being displayed.)
wavelength bandwidth current
Sodium 589.0 nm 0.5 nm 5.0 ma
Potassium 766.5 nm 1.0 nm 5.0 ma
Calcium 422.7 nm 1.0 nm 3.5 ma
Magnesium 285.2 nm 1.0 nm 3.0 ma
Consult the reproducibility sheets to determine the exact
settings used for the previous run.
b) Once the lamp current, wavelength, and bandwidth have
been set, adjust the photomultiplier voltage (HIGH VOLTAGE)
until the energy meter reading is in the middle of the green
band (0.2 - 0.8) using the course adjustment (larger knob)
first, then the fine adjustment (smaller knob). (Consult
reproducibility sheet for previous setting.)
c) To optimize the wavelength setting for each element, turn
the wavelength setting knob slightly to determine the
optimal (highest) ENERGY reading and lock in at that
wavelength.
6) Plug in both lamps. Check beam alignment of both lamps along
the burner head and adjust if necessary using the 2 metal screws on
the lamp holder so that the 2 beams coincide with each other. Also
check the alignment of the beam over the burner head slit and
adjust the position of the burner head so that the beam is a few mm
above the slit all along the burner head.
7) For magnesium (or other elements if specified), activate the deuterium arc background corrector by turning the background correction on for magnesium using MODE #3: CHANNEL/BACKGROUND. (A=A; B=B-bkg(D).)
8) Open valve on acetylene tank. (If it contains less than 70 psi, install a new tank.)
9) Open air valve that connects to instrument.
10) Turn on water to flush the sink to which the instrument's waste line leads.
11) Place the aspirator in a beaker filled with deionized water. Turn to AIR and flush for about 15 minutes.
12) Close screen, turn to AIR/FUEL and press PILOT. (Be sure screen is closed whenever flame is lit.)
13) Allow instrument to run for about 15 minutes with screen and door closed to equilibrate before beginning.
14) Set time and date using I/O (input/output). (#4=time; #5=date.)
15) Place instrument in S/E mode (scale expansion) using MODE #4: RESULTS. (S/E for A and B = 1.0; Normal; Display A,B, All info.)
16) Set the integration mode using INT. (Set for Auto; 0.5 sec; 0.0 sec Delay.)
17) Optimize absorbance for elements being measured:
Goal is to get approximately the same absorbance achieved
during the previous run for equivalent concentrations. (See
reproducibility sheets.)
a) Aspirate a zero standard. Press A/Z for each channel to
autozero the instrument for both elements. Once sample has
reached the flame and equilibrated, press READ.
b) Aspirate a high standard. Press READ to begin absorbance
readings. The absorbance will be displayed at 0.5 second
intervals.
c) To optimize absorbance, adjust the following to try to
get the desired absorbance for each element:
1) Adjust the position of the burner head. (3 ways:
up/down, back/forward, angular along the beam path.)
2) Adjust the FUEL and OXIDANT flow rates.
3) Adjust the aspiration rate.
d) Continue to read from high standards during the
optimization procedure, autozeroing the instrument
occasionally as needed.
18) Set to read in concentration units using MODE #4: RESULTS.
(Set for Conc; Normal; Display A,B, All info.)
19) Set for standardization using MODE #5: STATISTICS. (Set for 4 runs; Mean only.)
20) Set the integration mode using INT. (Set for Auto; 4.0 sec; 0.0 Delay.)
21) Begin standardization using STD. (Set for Normal calibration; Both; Instrument, after clearing data if necessary.) Enter the concentrations of the standards using the desired number of significant figures for the C standard. Standards 1-4 are in decreasing order.
22) Turn printer on.
23) Screen will prompt, "Run Std Z." Aspirate a zero standard.
24) Press READ after allowing sample to reach flame and equilibrate. (Always wait the same amount of time for all samples and standards throughout the session, usually 10-15 seconds after the sample has reached the flame.)
25) The instrument will take 4 readings and average them. To accept the reading, press ENTER.
26) Proceed with standards 1-5 as above, following screen prompts.
27) Instrument will calculate a calibration curve. At this point, selected standards may be rerun or the curve may be accepted. To get a printout of the curve, press "."
28) Set instrument to run samples using MODE #5: STATISTICS. (Set for 0 runs.) Set integration using INT. (Set for Manual; 4.0 sec; 0.0 Delay.)
29) Set instrument sequence number to 1 using I/O #11: SET SEQUENCE NUMBER. (This can be done at any point during the run to keep the sequence number properly aligned with the tube number being run.)
30) Shake tubes by inverting each tray carefully several times a few minutes before it is to be run.
31) Begin reading standards or samples in the same manner as during calibration procedure:
a) Place the aspirator in the tube, wait the appropriate
amount of time, then press READ. The instrument will only
take one reading.
b) Once the reading has been taken, remove the aspirator,
dip it into a beaker of deionized water to rinse, and then
proceed to the next tube.
1) The standards for each block should be within 5% of their true value. See chart below. (If they are greater than 5% from the true value, the data will be adjusted during the data reduction procedure.)
2) If one or more standards is not within 5% of its true value: After reading the entire set of standards, use A/Z to autozero the instrument to a zero standard and A/C to autocalibrate the instrument to a high standard. This will adjust the standard curve for any drift that has occurred. If it appears that the drift is not linear, it may be necessary to recalibrate the instrument before proceeding. In either case, resume the run by re-reading the standard curve and proceeding with the session.
PRECIPITATION:
Na+: Std # +/- 5% Range K+: Std # +/- 5% Range
1 0.475 - 0.525 1 0.95 - 1.05
2 0.380 - 0.420 2 0.76 - 0.84
3 0.285 - 0.315 3 0.57 - 0.63
4 0.190 - 0.210 4 0.38 - 0.42
5 0.095 - 0.105 5 0.19 - 0.21
Ca2+: Std # +/- 5% Range Mg2+: Std # +/- 5% Range
1 1.90 - 2.10 1 0.475 - 0.525
2 1.52 - 1.68 2 0.380 - 0.420
3 1.14 - 1.26 3 0.285 - 0.315
4 0.76 - 0.84 4 0.190 - 0.210
5 0.38 - 0.42 5 0.095 - 0.105
STREAMWATER:
Na+: Std # +/- 5% Range K+: Std # +/- 5% Range
1 1.90 - 2.10 1 2.85 - 3.15
2 1.52 - 1.68 2 2.28 - 2.52
3 1.14 - 1.26 3 1.71 - 1.89
4 0.76 - 0.84 4 1.14 - 1.26
5 0.38 - 0.42 5 0.57 - 0.63
Ca2+: Std # +/- 5% Range Mg2+: Std # +/- 5% Range
1 4.75 - 5.25 1 1.90 - 2.10
2 3.80 - 4.20 2 1.52 - 1.68
3 2.85 - 3.15 3 1.14 - 1.26
4 1.90 - 2.10 4 0.76 - 0.84
5 0.95 - 1.05 5 0.38 - 0.42
SHUT DOWN PROCEDURE:
1) Turn to AIR. Let flush for about 15 minutes before turning to OFF.
2) Unplug hollow cathode lamps, and put them away when cool.
3) Close valve on acetylene tank. Drain line by turning to AIR/FUEL. To completely drain line, turn repeatably between AIR/FUEL and AIR until acetylene tank gauge goes to 0 psi.
4) Return current and high voltage settings to lowest values.
5) Turn to RESTART/STANDBY.
6) Press POWER button to turn instrument off.
7) Remover burner head once it is cool and clean by sonicating it in a plastic beaker filled with deionized waer. Use a brush and deionized water to clean and rinse the burner head before replacing it in the instrument.
8) Turn printer off.
9) Close air valve that connects to instrument.
10) Turn off water flushing sink.
11) Replace cover over instrument.
NOTES:
1) Fill out reproducibility sheets each time the instrument is run.
2) For reference, Thermo Jarrell Ash manuals are located in the drawer near the instrument.