Agriculture Reference
In-Depth Information
Flame photometer
Reliable and accurate concentration of Na, K, Li, Ca, etc., in solutions
remains important in clinical and soil laboratories, and flame photometer
plays a great role in this direction. Flame photometry (also known as flame
atomic emission spectrometry) is a branch of atomic spectroscopy in which
the species examined in the spectrometer are in the form of atoms. The
other two branches of atomic spectroscopy are atomic absorption
spectrophotometry (AAS) and inductively coupled plasma-atomic
emission spectrometry (ICP-AES), a relatively new and very expensive
technique. In all cases the atoms under investigation are excited by light.
Flame photometry is simple and relatively inexpensive and used for
clinical, biological, and environmental analysis. Flame photometry is
suitable for qualitative and quantitative determination of several cations,
especially for metals that are easily excited to higher energy levels
(namely, Na, K, Rb, Cs, Ca, Ba, Cu) at a relatively low flame temperature.
Careful and frequent calibration is necessary for good results, and it is very
important to measure the emission from the standard and unknown
solutions under conditions that are as nearly identical as possible. The
processes in a flame photometer include the following stages: desolvation
(drying), vaporization, atomization, and ionization. Each of these stages
includes the risk of interference in case the degree of phase transfer is
different for the analyte in the calibration standard and in the sample
Hot air oven and hot
air sterilizer
An electrical instrument used for sterilization. The oven uses dry heat
50-300
C (generally) to sterilize articles. These are widely used to sterilize
articles that can withstand high temperatures and not get burned, like
glassware and powders. Linen gets burned and surgical sharps lose their
sharpness. Generally, a digitally controlled thermostat maintains the
temperature. Double walled insulation separated by an air-filled space in
between keeps the heat in and conserves energy. An air circulating fan
helps in uniform distribution of the heat. The capacities of these ovens
vary. Power supply needs vary from country to country, depending on the
voltage and frequency (hertz) used. Temperature-sensitive tapes or other
devices like those using bacterial spores can be used to work as controls, to
test for the efficacy of the device in every cycle. They do not require water
and there is not much pressure buildup within the oven, unlike an
autoclave, making them safer to work with. A complete cycle involves
heating the oven to the required temperature, maintaining that temperature
for the proper time interval for that temperature, turning the machine off,
and cooling the articles in the closed oven till they reach room temperature
If the door is opened before time, heat escapes and the process becomes
incomplete. Thus, the cycle must be properly repeated all over
