Medical Laboratory Science Review MLS | Quizlet

What formulas correctly describes the relationship between absorbance and %T?

A = 2-log %T
A = log 1/T
A = -log T

A solution that has a transmittance of 1.0 would have an absorbance of..

2.0

In absorption spectrophotometry...

Absorbance is directly proportional to transmittance

Which wavelength would be absorbed strongly by a red-colored solution?

450 nm

A green colored solution would show highest transmittance at...

525 nm

A tech is performing an enzyme assay at 340 nm using a visible-range spectrophotometer. After setting the wavelength and sdjusting the readout to zero %T with the light path blocked, a cuvette with deionized whater is inserted. With the light path fully open and the 100% T control at maximum, the instrument readout will not rise about 90%T. What is the most appropriate first course of action?

Replace the source lamp

Which type of monochromater produces the purest monochromatic light in the UV range?

A prism and variable exit slit

Which monochromator specification is required in order to measure the true absorbance of a compound having a natural absorption bandwidth of 30 nm?

5-nm bandpass

Which photodetector is most sensitive to low levels of light?

Photomultiplier tube

Which condition is a common cause of stray light?

Dispersion from second-order spectra

What is the most common cause of loss of linearity at high-analyte concentrations?

Stray light

Which type of filteris best for measuring stray light?

Sharp cutoff

Which of the following materials is best suited for verifying the wavelength calibration of a spectrophotometer?

Holmium oxide glass

Why do many optical systems in chemistry analyzers utilize a reference light path?

To minimize error caused by source lamp fluctuation

Which component is required in a spectrophotometer in order to produce a spectral absorbance curve?

Photodiode array

The half-band width of a monochromator is defined by

the range of the wavelengths passed at 50% transmittance

The reagent blank corrects for absorbance caused by

the color of reagents

A plasma sample is hemolyzed and turbid. What is required to perform a sample blank in order to correct the measurement for the intrinsic absorbance of the sample when performing a spectrophotometric assay?

Substitute saline for the reagent

Which instrument requires a highly regulared DC power supply?

A spectrophotometer with a photomultiplier tube

Which statement regarding reflectometry is true?

100% reflectance is set with an opaque film called a white reference

Bichromatic measurement of absorbance can correct for interfering substances if

The concentration of the interferent to absorbance is the same at both wavelengths

Which instrument requires a primary and secondary monochromator?

Fluorometer

Which of the following statements about fluorometry is accurate?

Unsaturated cyclic molecules are often fluorescent

Which of the following components is not needed in a chemiluminescent immunoassay analyzer?

Source lamp

Which substance is used to generate the light signal in electochemiluminescence?

Ruthenium

Light scattering when the wavelength is greater than 10 times the particle diameter is described by

Rayleigh's law

Which statement regarding nephelometry is true?

The detector response is directly proportional to concentration

The purpose of the nebulizer in an atomic absorption spectrophotometer that uses a flame is to

convert ions to atoms

A flameless atomic absorption spectrophotometer dhydrates and atomizes a sample using

A graphite capillary furnace

When measuring lead in whole blood using atomic absorption spectrophotometry, what reagent is required to obtain the needed sensitivity and precision?

triton-X-100

Interference in atomic absorption spectrophotometery caused by differences in viscosity is called

Matrix effect

All of the following are required when measuring magnesium by atomic absorption spectrophotometry except

A 285 nm reference beam to correct for background absorption

When measuring calcium by atomic absorption spectrophotometry, which is required

Lanthanum oxide to chelate phosphates

Ion selective analyzers using undiluted samples have what advantage over analyzers that use a diluted sample

Are not subject to pseudohyponatremia caused by high lipids

Select the equation describing the potential that develops at the surface of an ion-selective electrode is determined by the

Concentration of the potassium chloride filling solution

The term RT/nF in the Nernst equation defines the Slope of the electrode

Concentration of the potassium chloride filling solution

The ion-selective membrane used tho measure potassium is made of

Valinomycin gel

The response of a sodium electrode to a to-fold increase in sodium concentration should be

An increase in potential of approximately 60 mV

Which of the electrodes below is a current-producing producing rather than a voltage-producing electrode?

Clark electrode

Which of the following would cause a response error from an ion-selective electrode for sodium when measuring serum but not the calibrator?

Protein coating the ion-selective membrane

In polargraphy, the voltage needed to cause depolarization of the cathode is called the

Decomposition potential

Persistent noise from an ion-selective electrode is most often caused by

Blocked junction at the salt bridge

Which element is reduced at the cathode of a Clark polarographic electrode?

Oxygen

Which of the following statements accurately characterizes the coulometric titration of chloride?

Constant current must be present across the generator electrodes

In the coulometric chloride titration

the endpoint is detected by amperometry

Which of the following compounds can interfere with the coulometric chloride assay?

Bromide

All of the following compounds contribute to the osmolality of plasma except

Lipids

One mole per kilogram H2O of any solute will cause all of the following except

Raise vapor pressure by 0.3 mm Hg

What component of freezing point osmometer measures the sample temperature?

Thermistor

What type of measuring circuit is used in freezing point osmometer?

Wheatstone bridge

Which measurement principle is employed in a vapor pressure osmometer?

Seebeck

The freezing point osmometer differs from the vapor pressure osmometer in that only the freezing point osmometer

is sensitive to ethanol

The method for measuring iron or lead by plating the metal and then oxidizing it is called

Anodic stripping voltometrey

The term isocratic is used in high performance liquid chromatography to mean the

Mobile phase consists of a constant solvent composition

The term reverse phase is used in HPLC to indicate the mobile phase is

More polar than the stationary phase

What is the primary means of solute separation in HPLC using C18 columns

Partitioning

the most commonly used detector for clinical gas-liquid chromatography is based upon

Flame ionization

What type o detector is used in high performance liquid chromatography with electrochemical detection

Glassy carbon electrode

In gas chromatography, the elution order of volatiles is usually based upon the

Boiling point

Select the chemical that is used in the most HPLC procedures to decrease solvent polarity

Acetonitrile

In thin-layer chromatography, the distance the solute migrates divided by the distance the solvent migrates in the

Rf

Which reagent is used in thin layer chromatography to extract cocaine metabolites from urine

Alkali and organic solvent

What is the purpose of an internal standard in HPLC and GC methods>

To compensate for variation in extraction and injection

What is the confirmatory method for measuring drugs of abuse?

Gas chromatography with mass spectroscopy (GS-MS)

The fragments typically produced and analyzed in methods employing mass spectroscopy are typically

Cations caused by electron loss or proton attachment

What component is used in a GC-MS but not used in an LC-MS

Electron source

What process is most often used in LC-MS to introduce the sample into the mass filter

Electrospray ionization

In mass spectroscopy the term base peak typically refers t

The peak with the most abundance

Which method is the most useful when screening for errors of amino and organic acid metabolism?

Electrospray ionization tandem-mass spectroscopy

In Tandem-mass spectroscopy, the first mass filter performs the same function as

The chromatography solumn

Why is vacuum necessary in the mass filter of a mass spectrometer?

It prevents collision between fragments

What method is used to introduce the sample into a mass spectrometer for analysis of a trace element?

Inductively charged plasma ionization

Which component is needed for a thermal cycler to amplify DNA?

Programmable heating and cooling unit

In real-time PCR, what value is needed in order to determine the threshold

Background signal

In addition to velocity, what variable is also needed to calculate the relative centrifugal force of a centrifuge

head radius

Which of the situations is likely to cause an error when weighing with an electronic analytical balance

Failure to close the doors of the balance before reading the weight

What is the reference range for arterial blood pH?

7.35- 7.45

Which of the following contributes the most to ther serum total CO2?

HCO3-

In addition to sodium bicarbonate, what other substance contributes most to the amount of base in the blood

Hemoglobin concentration

Which of the following effects results from exposure of a normal arterial blood sample to room air>

PO2 increased, PCO2 decreased, pH increased

The normal difference between alveolar and arterial PO@ is

10 mmHg

A decreased PAO-PAO2 difference is found in

Ventilation defects

the determination of the oxygen saturation of hemoglobin is best accomplished by

Polychromatic absorbance measurements of a whole blood hemolysate

Correction of pH for a patient with a body temperature of 38 would require

Subtraction of 0.015

Select the anticoagulant of choices for blood gas studies

lithium heparin

What is the maximum recommended storage time and temperature for an arterial blood gas sample drawn in a plastic syringe?

30 min, 22 degrees

Which set of results is consistent with uncompensated respiratory alkalosis?

pH 7.66, HCO3 22 mmol/L, PCO2 20 mmHG

Which of the following will shift the O2 dissociation curve to the left

ALkalosis

In which circumstance will the reporting of calculated oxygen saturation of hemoglobin based on PO2, PCO2, pH, temperature, and hemoglobin be in error?

Carbon Monoxide poisoning

Which would be consistent with partially compensated respiratory acidosis?

pH decreased, PCO2 increased, Bicarbonate increased

Which condition results in metabolic acidosis with severe hypokalemia and chronic alkaline urine?

Renal tubular acidosis

Which of the following mechanisms is responsible for metabolic acidosis?

Bicarbonate deficiency

Which of the following disorders is associated with lactate acidosis?

Alcoholism

Which of the following is the primary mechanism of compensation for metabolic acidosis

Hyperventilation

The following conditions are all causes of alkalosis. Which condition is associated with respiratory (rather than metabolic) alkalosis?

Anxiety

Which of the following conditions is associated with both metabolic and respiratory alkalosis?

Hypokalemia

In uncompensated metabolic acidosis, which of the following will be normal?

PCO2

Which of the following conditions is classified as normochloremic acidosis?

Diabetic ketoacidosis

Which PCO2 value would be seen in maximally compensated metabolic acidosis?

15 mm Hg

What are the three levels for quality control of pH and blood gases?

Systematic errors can be detected earlier than with two controls