Abstract: A gas chromatograph has a switch valve for selectably directing an incoming carrier gas into a first flow route for split analyses or into a second flow route for direct injection analyses. A pressure sensor and a bypass flow route with low flow resistance connected to the carrier gas supply route are also connected to the switch valve. When the switch valve is set for a split analysis, the pressure sensor becomes connected to a vaporization chamber through a flow route with low flow resistance. When the switch valve is set for a direct injection analysis, the pressure sensor becomes connected to the carrier gas supply route through the bypass flow route.

Abstract: A target pressure is calculated by a fluid dynamic theory using a length of the column, an inner diameter of the column and the temperature of the column so that the linear velocity of the gas flowing through the column is at a preset pre-determined value at which the HETP (height equivalent to a theoretical plate) value, as calculated from chemical kinematic theory, is the minimum and the resolution of the column is the highest. Then the pressure of the gas at the entrance of the column of a chromatograph is maintained at the calculated target pressure while the temperature of the column is raised to reduce the analyzing time.

Abstract: A gas chromatograph for operation selectably in both split mode and splitless wide bore injection mode includes a capillary column, a sample injection chamber at the inlet of the column, a three-way valve, a first piping line connected between one of the two outlets of the three-way valve and the sample injection chamber, a split line connected to the sample injection chamber immediately upstream of the inlet of the column for discharging therethrough a portion of a gas being sent out from the sample injection chamber, a second piping line connected between the other of the outlets of the three-way valve and the split line, and a third piping line connected between the first and second piping lines. By properly controlling the total carrier gas flow rate and the column inlet pressure, the split ratio can be controlled easily. By varying the split ratio appropriately during an analysis, the amount of the carrier gas to be wasted in the case of a split mode of operation can be significantly reduced.

Abstract: A gas chromatograph for operation in split mode is controlled by calculating the column flow rate and the total carrier gas flow rate from the length and inner diameter of the column and specified values for temperature and column inlet pressure, adjusting the split flow rate such that the pressure value measured by a pressure sensor becomes equal to the specified pressure value and control the total carrier flow rate to be equal to the calculated value therefor. In this manner, the split ratio of the gas chromatograph can be maintained easily at a specified value. The amount of carrier gas to be wasted can be significantly reduced by appropriately varying the split ratio with time during the course of an analysis.

Abstract: An electron capture type detector for gas chromatography has an ionization vessel containing therein line sources for a radioactive isotope serving as a negative electrode, a collector electrode, a purge gas route, a discharge gas route, and an end of a column disposed at its lower section. The collector electrode includes a filament made of a heat resistant material and itself connected to a heating device such that the filament can be heated to about 300.degree.-600.degree. C. so as to eliminate contaminants deposited on the collector electrode by thermal decomposition, oxidation or reduction, without the necessity of disassembling the detector itself. The contaminants are effectively removed by simultaneously causing air or hydrogen gas to pass over the collector electrode through the ionization vessel from the purge gas route to the discharge gas route.

Abstract: A data storing apparatus for storing and categorizing data from an analytical instrument, which has a file name creator for obtaining a time signal at the beginning of analysis and for writing the time signal in the file name portion of a data file in a memory as a temporarily assigned file name. The data storing apparatus also has a file name changer for obtaining a new name input thereto, and substituting the new name for the time signal in the file name portion of the data file.