Flame Photometer maintenance is a vital part of making sure that readings and calibration curves are kept to the lowest inter-sample variance possible.
A flame photometer requires maintenance as it is used. Parts suffer can suffer greatly dependent on the sample makeup, the age of the device and the conditions in which the device is kept.
The two main parts which cause the most instability if not properly maintained, and are also the easiest to damage are the mixing chamber and the nebuliser. This could come in the form of either a nebuliser blockage or etching into the nebuliser, which would affect the finely tuned and calibrated spray from the nebuliser. Blockages would cause a pressure gradient in the nebuliser which would affect the spray pattern of the aerosol, whilst etching into the nebuliser would affect the final contact point of the spray needle, thus affecting the spray.
To minimise blockages as standard BWB Technologies provides a finely calibrated cleaning rod to insert into the centre of the nebuliser needle to clean out any blockages. Blockages are caused by viscous material or particulate matter “gunking up” the needle and needing to be manually cleaned. Etching is caused by having a high acidic content which reacts very slowly with the steel of the nebuliser. Normally H2NO3 is the commonly used pre-treatment acid and the NO3 ion gives a degree of protection to the steel, however acids such as HCl and organic acids can cause etching at a faster rate.
The mixing chamber is the other main factor which leads to varying readings due to lack of correct maintenance. It is in this component where the combustible fuel mixture and the sample spray from the nebuliser are introduced to each other and mixed. It contained a small disc (or baffle) split into 4 different slightly angled quarters as well as a large cavity. The placement of the nebuliser is also at an angle so to promote a tornado effect inside the cavity that passes through the small holes in the plastic disk.
If not adequately cleaned when using a viscous material in the analysis, the viscosity can cause the sample to form small particulate matter to form on the inner surfaces of the mixing chamber and baffle. This can then get picked back up by the tornado effect when the sample or calibration standard is changed, which causes a sudden spike in the sample concentration, therefore reducing the stability of the reading.
To clean your mixing chamber, it is usually recommended that an ultra-sonic bath is used to dislodge large particulate matter. DI water mixed with the BWB Technologies recommended cleaning agent forms the base solution for the ultrasonic bath. A rinse of DI water is then used to wash out the mixing chamber and baffle. Always make sure to put back the rubber O-Ring to ensure is it air and water tight, push the baffle into the lower section of the mixing chamber and make sure it is not poking out over the tips of the lower section and flush with the surface, care should be taken to ensure it is replaced in the same orientation and aligned with the drain slots, finally screw the mixing chamber up.
The mixing chamber rarely reacts with other materials and solutions due to being made of highly inert polymers; however the above method should be an effective way of cleaning the mixing chamber.