Means and method for controlling eluent gradient in liquid chromatography

Claim 2

Apparatus for varying the relative apportionment of a plurality of eluents flowing into a liquid chromatograph, comprising: means for generating a substantially linearly varying monotonic pilot signal extending between predetermined limiting values, including means for varying the slope of said pilot signal; means for providing a range signal x representative of the intended variation in apportionment of the eluents; a function generator coupled to said means for generating for receiving said pilot signal y and outputting a signal A in response thereto characterized by the expression A = x · G(y) where G is an operator such that G(y) is a monotonic function; means for selectively varying the value of x; and driver means coupled to said function generator for operating an eluent apportioning means to apportion the relative flow rates of ones of a plurality of eluents in accordance with the value of the outputted signal A.

Claim 3

Apparatus according to claim 1, where G(y) = y m .

Claim 4

Apparatus according to claim 2, further including means for varying the value of m.

Claim 5

Apparatus for controllably varying the apportionment gradient between two eluents flowing into the column of a liquid chromatograph comprising: a first function generator for generating a substantially linear, monotonically varying pilot signal y arising between predetermined limits; means for varying the slope of said pilot signal whereby said pilot signal may be caused to arise between said limits in a lesser or greater time period; a second function generator coupled to said first function generator for receiving said pilot signal y and outputting a signal A in response thereto, said signal A having upper and lower limits and characterized by the expression A = x · G(y) where G is an operator such that G(y) is a monotonic non-linear function and x is a predetermined constant value, said second function generator comprising means for selectively varying the value of x to thereby vary the difference between the upper and lower limits of signal A; and eluent apportioning means coupled to said function generator and responsive to said outputted signal A for varying the proportion of two eluents.

Claim 6

Apparatus for controllably varying the apportionment gradient between two eluents flowing into the column of a liquid chromatograph comprising: a first function generator for generating a substantially linear, monotonically varying pilot signal y arising between predetermined limits; means for varying the slope of said pilot signal whereby said pilot signal may be caused to arise between said limits in a lesser or greater time period; a second function generator coupled to said first function generator for receiving said pilot signal y and outputting a signal A in response thereto, said signal A having upper and lower limits and characterized by the expression A = x · G(y) where G is an operator such that G(y) is a monotonic non-linear function and x is a predetermined constant value, said second function generator comprising means for selectively varying the value of x to thereby vary the difference between the upper and lower limits of signal A; and eluent apportioning means coupled to said function generator and responsive to said outputted signal A for varying the proportion of two eluents.

Claim 7

Apparatus as defined in claim 4, further including means coupled to said second function generator and to said eluent apportioning means for adding a constant signal B to said output signal A.

Claim 8

Apparatus as defined in claim 5 wherein said means for adding comprises first means for adjustably determining a first signal; second means for generating a second signal; means for combining said second signal with said output signal A; means for deriving the difference between said first and said second voltages to provide a difference signal x; and means for applying said signal x to said second function generator; whereby the range of the signal A outputted by said second function generator is expanded in accordance with a change in the value of the signal x.

Claim 9

A control system for effecting a non-linear gradient between two eluents in a liquid chromatograph and for selectively expanding and contracting the range of the gradient without varying the shape thereof, comprising: a clock stage for producing clock pulses; means for adjustably varying the rate of said clock pulses; a counter receiving said clock pulses and producing a digital output signal in response thereto; a digital-to-analog converter for converting said digital signal into an analog pilot signal y extending between predetermined limits; means for producing a first signal representing a desired initial eluent ratio; means for producing a second signal representing a desired final eluent ratio; first summing means for receiving said first and said second signals and outputting a range signal x representative of the difference therebetween; a function generator responsive to said pilot signal y and said range signal x to output gradient signal A where A = x · y.sup.m said function generator including means for varying the effective value of m; and means for combining said gradient signal A with said first signal.

Claim 10

A control system for effecting a non-linear gradient between two eluents in a liquid chromatograph and for selectively expanding and contracting the range of the gradient without varying the shape thereof, comprising: a clock stage for producing clock pulses; means for adjustably varying the rate of said clock pulses; a counter receiving said clock pulses and producing a digital output signal in response thereto; a digital-to-analog converter for converting said digital signal into an analog pilot signal y extending between predetermined limits; means for producing a first signal representing a desired initial eluent ratio; means for producing a second signal representing a desired final eluent ratio; first summing means for receiving said first and said second signals and outputting a range signal x representative of the difference therebetween; a function generator responsive to said pilot signal y and said range signal x to output gradient signal A where A = x · y.sup.m said function generator including means for varying the effective value of m; and means for combining said gradient signal A with said first signal.

Claim 11

A control system as defined in claim 7, further including: reset means coupled to said counter and responsive thereto for causing said counter to operate in a reverse mode after attaining a predetermined, maximum value; said reset means further being coupled to said clock stage for increasing the rate at which clock pulses are applied to said counter.

Claim 14

A system as defined in claim 9, wherein said first and second non-linear signals are exponential in form.

Claim 15

A system as defined in claim 9, wherein said second non-linear signal exhibits a characteristic slope which is substantially a reflection in time of the characteristic slope of said first signal.

Claim 18

A method as defined in claim 12, further including the step of adding a constant signal B to said gradient signal to determine the initial ratio of the eluents.

Claim 19

A method as defined in claim 13, wherein said signal G(y) is characterized by the expression G(y) = y.sup.m

Claim 20

A method as defined in claim 12, further including the steps of: increasing the rate at which said periodic, digital signal arises; converting said digital signal to a substantially linearly-decreasing signal y which extends between fixed limits; operating upon said substantially linearly-decreasing signal y with an operator to produce a reset gradient signal having a finite slope; and varying the ratio between the two eluents from said final to said initial concentration in response to the instantaneous value of the reset gradient signal.

Claim 21

A method as defined in claim 15, wherein said linearly-decreasing signal y is operated upon by said operator G(y).

Claim 22

A method as defined in claim 16, wherein said operator G(y) is characterized by the expression G(y) = y.sup.m