cant pass float var in insert statement

#include <mariadb/mysql.h>
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float pHReading, TempReading;
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if( tab_reg[0] > 64500 )
pHReading = ( (float)tab_reg[0] - 65535 ) / 100;
else
pHReading = (float)tab_reg[0] / 100;
printf( "Register 43001 pH = %.2f\n", pHReading );
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TempReading = (float)(tab_reg[0])/10;
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query = "insert into pHTemp values( NULL, NOW(), pHReading, TempReading )";
printf( "pHReading: %f and TempReading: %f and QUERY: %s\n", pHReading, TempReading, query );
if (mysql_real_query(mysql, query, strlen(query)))
show_error(mysql);

The resulting output and error are:
pHReading: 3.500000 and TempReading: 24.600000 and QUERY: insert into pHTemp values( NULL, NOW(), pHReading, TempReading )
Error(1054) [42S22] "Unknown column 'pHReading' in 'field list'"root@PiDevel:~/ModBus#

I cant seem to get the float vars pHReading and TempReading to dereference in the query before sending them to the DB

What am I doing wrong???

Richard