A system comprising: a microfluidic device comprising a laminated wafer body comprising an internal microchannel, the internal microchannel comprising a first internal charging chamber (4525, 4610, 4710) and a second internal charging chamber (4540, 4615, 4715), wherein each of the first internal charging chamber and the second internal charging chamber comprises a section having an increased diameter compared to other sections of the internal microchannel, the first internal charging chamber (4525, 4610, 4710) and the second internal charging chamber (4540, 4615, 4715) each fluidically coupled to an inlet port and an outlet port on the body of the microfluidic device through the internal microchannel; a gas chromotography column fluidically coupled to the inlet port of the microfluidic device; a gas source configured to supply gas for modulating flow within the microfluidic device; and a 3-way solenoid switching valve fluidically coupled to the gas source and to the first and second internal charging chambers, the switching valve switchable between a first position and a second position, the switching valve in the first position permitting flow of gas from the modulating gas source to the first internal charging chamber (4525, 4610, 4710) to provide column effluent from the first charging chamber (4525, 4610, 4710) to the outlet port of the microfluidic device and to a detector fluidically coupled to the outlet port, the switching valve in the second position permitting fluid flow of gas from the modulating gas source to the second internal charging chamber (4540, 4615, 4715) to provide column effluent from the second charging chamber (4540, 4615, 4715) to the outlet port of the body of the microfluidic device and to the detector fluidically coupled to the outlet port. a microfluidic device comprising a laminated wafer body comprising an internal microchannel, the internal microchannel comprising a first internal charging chamber (4525, 4610, 4710) and a second internal charging chamber (4540, 4615, 4715), wherein each of the first internal charging chamber and the second internal charging chamber comprises a section having an increased diameter compared to other sections of the internal microchannel, the first internal charging chamber (4525, 4610, 4710) and the second internal charging chamber (4540, 4615, 4715) each fluidically coupled to an inlet port and an outlet port on the body of the microfluidic device through the internal microchannel; a gas chromotography column fluidically coupled to the inlet port of the microfluidic device; a gas source configured to supply gas for modulating flow within the microfluidic device; and a 3-way solenoid switching valve fluidically coupled to the gas source and to the first and second internal charging chambers, the switching valve switchable between a first position and a second position, the switching valve in the first position permitting flow of gas from the modulating gas source to the first internal charging chamber (4525, 4610, 4710) to provide column effluent from the first charging chamber (4525, 4610, 4710) to the outlet port of the microfluidic device and to a detector fluidically coupled to the outlet port, the switching valve in the second position permitting fluid flow of gas from the modulating gas source to the second internal charging chamber (4540, 4615, 4715) to provide column effluent from the second charging chamber (4540, 4615, 4715) to the outlet port of the body of the microfluidic device and to the detector fluidically coupled to the outlet port.