X and Y = Internal standard
peak areas in 1:1 mixture and plasma samples
 Nonstandard abbreviations: DALY, disability-adjusted life years; A/IS, area drug to internal standard
, tyrosine (100 [micro]L), was added to each standard mixture or urine (100 [micro]L) and vortex mixed for 30 seconds followed by centrifugation (5 min at 3000 rpm); the supernatant (20 [micro]L) was injected.
20 [micro]L blood sample and 100 [micro]L acetonitrile (containing 20 ng/mL internal standard
gelsenicine) were added in a 1.5 mL Eppendorf tube, mixed using a vortex mixer for 1.0 min, and centrifuged at 13,000 rpm for 10 min at 4[degrees]C.
Key words: calibration; chromatography; internal standards
; quantitation; quantitative analysis; response factor.
By using the same pipette used for the calibration solution, 2 ml of the internal standard
solution was mixed and diluted to 100 ml in other volumetric flask.
The selection of internal standard
for LC-MS/MS method was different for HPLC-UV method.
Slightly different sample preparation conditions were used for SIL versus SILAC internal standard
methods prior to LC-MS analysis as shown in Figure 1.
The DC for each blend, polymerized and unpolymerized, was determined by the ratio of the absorbance peak corresponding to the aliphatic carbon-carbon double bond (1637 [cm.sup.-1] peak height) with that of the internal standard
(1715, 1608, and 1582 [cm.sup.-1] peak height), according to methods described in a previous study.
The internal standard
is called W18: "If you pass that you're guaranteed to pass anywhere in the world."
For example, it says Toyota never produced a document showing the company's internal standard
for roof strength was tougher than the federal requirement, CBS News reported.