Introduction

This instrument is a clinical flame photometer. It was designed to provide very rapid moderately accurate (1-2%) readings from clinical samples like blood, sweat and tears with the occasional lot of urine. It was designed for routine operation with little training. The clinical design parameters limit its ease of use in non clinical setting where values nm ay be outside the range of the instrument. With some attention to detail in sample preparation it's use can be broadened to encompass the animal physiology lab. This unit is a single chanel, low temperature flame fhotometer for the determination of Na K Li and Ca. It has been fitted with a lineizer module which electronically straightens the calibration curve and permits single poin calibrations.

The controls and indicators

Power On (10): an LED which is illuminated when the instrument is on
Flame On (11): an LED which is illuminated when the flame is alight
Blank (5): control used to set the display to zero while aspirating a blank solution die plain dilutant solution
Sensitivity: Fine (5) and Course (4) - These two controls are used to set the display to an appropriate concentration reading while aspirating a standard solution. The Course control is a four position rotary switch and the fine is a ten turn potentiometer.
Fuel (4): This control provides a fine adjustment of the fuel flow and enables the optimum flame conditions to be set for each element.
Na K Ca (1): This three position slide lever selects the correct filter for the element to be determined. When used with alternate filter types the appropriate label is attached along side the default element.
Decimal (8): This touch control, located adjacent to the digital display, is used to select the decimal point, eg using the decimal push-button to select the decimal point , a reading of 1000 will be displayed as 100.0. This affects the display only the sensitivity of the instrument Power - This rocker switch turns the a.c. power supply on and off. When switched on power will be provided to the instrument and its accessories and an automatic ignition sequence will be initiated. When switched off the flame is extinguished and the power to the instrument and its accessories is cut off.

Initial adjustments

Omit this section if the instrument is already operating

Check to be certain that the gas and air supply lines are securely attached to the instrument.

Turn on the gas supply at the tank and verify that the tank is providing 30 psi. Turn the gas supply back off for now.

Turn on the air supply (lab air tap on the bench) and adjust r at the rear of the instrument until the air pressure gage indicates 12 psi.

Verify that the waste water waste water "U" tube is filled with water. Fill it if the level is low. See figure 3 for the location of the U tube.

Turn the fuel control fully clockwise to the closed position, but do not force it. This control is a precision assembly that will be irrevocably damaged by rough handling.

Open the fuel control 9 turns (counterclockwise)

Start up

Omit this section if the instrument is already operating

Depress the power switch on the front panel. The LED will light and an ignition sequence will commence.

Recheck and readjust the air pressure regulator on the rear panel until the gage reads 12 psi.

Turn on the fuel at the source

Important:: If the flame on LED has not illuminated before the end of the ignition cycle, switch off and wait 60 seconds. Then with out adjusting the fuel control switch on again to initiate another cycle.

If ignition fails again, open the fuel control 1 additional turn and retry. You may repeat this procedure until ignition occurs but under no circumstances should you open the fuel control more than 4 additional turns (to 13 turns) or explosive concentrations of gas may accumulate.

Switch to the ion of interest by sliding the selection lever indicate Na, K or Ca. Make sure that the drainage water-trap is full by adding distilled water from a squeeze bottle until it can be seen running out of the overflow tube.

Insert the nebulizer tube into a beaker containing at least 100 ml of dilutant and continue to aspirate the dilutant for 15 minutes while the instrument warms up. Accuracy is achieved only after a 15 minute warm up.

Standardization

Stock standard solutions are prepared, and subsequently diluted to working standard concentrations. This usually involves several weighings initially, but makes available substantial quantities of stock solutions which need only simple dilution to produce working standards. As this is time consuming, we will use Corning prepared standard stocks to prepare all of the working standards.

Standard stock solutions

The use of deionized type I water is required. Analytical-grade chemicals only must be used. The primary standards provided are as follows

Corning Standard 001 56 120H which is 1000 ppm Na
Corning Standard 001 56 121J which is 1000 ppm K
Corning Standard 001 56 123L which is 1000 ppm Ca

Working standards - Caution working standard dilutions are made with type I deionized water not Corning diluent

Immediately before use, working standards are prepared by diluting the stock standards above with distilled water to produce a 10mM working standard. (299.9 ppm for Na and 399.0 for K) One hundred ml will serve the entire class, so check each others calculations and make up a single batch for each ion. Remember that you need to set the value 10.0 (using the calibration dials) while the sample is asperating

Presentation standards - Caution all dilutions are made with Corning diluent not water.

It is critical to remember that both your samples and this working standard must be diluted 1:200 (25 ul stock in 5000 ul diluent immediately before aspirating it into the flame. Full strength working standards or blood samples can not be read and they will will contaminate the aspirator. The blank working standard is pure dilutant with neither sodium or potassium added serves as the 0 mM blank for adjusting the 0 value of the instrument. Although working stock solutions will keep for about six months at 4∫ C, it is not recommended. Working standards should be held for no more than a week, nor made up in quantities of more than 500 ml.

Routine precautions

This insrument can not output a number greater than 340. Any number in the 300's should be consisered off scale and the sample should be rediluted and reread.
Never use the gas and air controls as on/off valves. If you do, they will soon cease to have any effect on the flow-rate, and may ultimately become dangerous.
Never touch the chimney or look down it from above. It is extremely hot and will result in burns. During ignition it can spew a meter of flame with a sound and fury that will certainly get your attention.
While the instrument is standing idle, with the flame alight but with no samples being applied, draw distilled water continuously through the sampling system. This keeps the temperature of the burner stable, and avoids the danger that rising temperature might otherwise affect the dissociation of the first samples.
Do not handle the inlet end of the atomizer capillary. Sodium deposited by the fingers will cause considerable inaccuracy at the low concentrations being measured.
Although smoking is not permitted in civilized areas, you should still be aware of the fact that cigarette smoke affects the potassium reading. Never smoke while using the instrument; do not use the instrument while smoke is present in the room. if you have handled a lighted cigarette, wash your hands and rinse with DI water.
Any glass ware (beakers, pipettes etc) must be meticulously clean and rinsed with Type I (18 megohms) water. Even careful rinsing with tap water could introduce 500% errors in your readings
Air locks may occur in the capillary if it is not fully immersed in the solution. These are characterized by a string of bubbles clearly visible in the tube. They may be cleared by suction using a plastic syringe.
Calibration

Select the appropriate filter for your ion and, while aspirating dilutant, adjust the blank control so that the display reads zero.

Aspirate your presentation standard (working standard diluted 1:200 with diluent). Allow 20 seconds for the reading to stabilize , and then adjust the course and fine controls to the value of the standard (10 mM for both Na and K). Note: the decimal point. This simply lights up the dot it does not change anything else but it will be easier to read the instrument if you light it up. Your 10.0 mM standard can now be adjusted to 10.0 instead of 100
Remove the standard and aspirate a blank solution of dilutant for 20 seconds. Readjust the blank control.

You can aspirate any other calibration standards that you may have prepared for the same ion and produce a multipoint calibration curve. Start with the lowest and work toward the highest to avoid carry over. Aspirate for 20 seconds, read the instrument then aspirate diluent for 10 seconds and aspirate another sample.

This instrument is equipped with an computer linearizer which lessens the need for preparing a standard curve. In order to obtain maximum linearity from this instrument, however, for maximum accuracy your standards should be near the middle of the effective range for each ion. Remember that you must change the filter to match each ion.

Samples:

(NOTE You really need to have some idea of your expected values to get your dilutions correct. You should dilute your unknowns so that they are close to 10.0 mM)

Carry out your tests, rechecking zero and standards as necessary, or at intervals of not more than 10 to 20 minutes in any case. Remember that you must dilute your samples exactly as you did your standards in order to produce accurate readings. If your readings are exceptionally low (<2.0 mM), your accuracy will suffer and you should consider consider rediluation to a more appropriate concentration. If you dilute 1:100 instead of 1:200 you will double the effective concentration seen by the machine. Don't for get to correct your values for the dilution factor. Remember that the effective concentration range of instrument is from 0 to 200 mmol/L. At no time can a reading greater than 200 be considered accurate. It must be further diluted and the result corrected for the dilution factor.

In addition, This instrument is very good at rejecting interference from other ions. but high levels of any ion will affect the determination of the others. The following specifications will help you deter mine if you are apt to experience interference.

Na - Errors in Na readings due to Ca, K or Li present in biological fluids will not exceed 1 mmol/L Na where the levels of these elements do not exceed 3.5 mmol/L Ca, 100 mmol/L K, and 2.0 mmol/L Lie

K - Errors in K readings due to Ca, Na or Lie present in biological fluids will not exceed 0.1 mmol/L K where the levels of these elements do not exceed 3.5 mmol/L Ca, 180 mmol/L Na, and 2.0 mmol/L Lie

The over all accuracy of this instrument is better than 2%

Shut down
Aspirate cleaning solution for at least one minute Aspirate deproteinizing solution for at least 1 minute. Aspirate dilutant for at least 2 minutes Power off and Gas off at the source.

Walter I. Hatch
wihatch@smcm.edu
August 21, 2005